SlideShare a Scribd company logo
1 of 135
Chemistry of Nanoscale
                Materials
       Synthesis, Properties and Applications
             Potential Impacts of Nanoscale Materials

           Pharmacy                      Water purification
       Therapeutic drugs                      Catalysts
 Tagging DNA and DNA chips                    Sensors
      Information Storage             Nanostructured Electrodes
 Chemical/Optical components            Improved polymers
Environmental/Green Chemistry          Smart magnetic fluids
          Solar Cells                Improved National Security
                 Environmental remediation
Definitions
Nanoparticle: A solid particle in the 1-1000 nm range that could be
noncrystalline, an aggregate of crystallites, or a single crystallite
Nanocrystal: A solid particle that is a single crystal in the nanometer
size range.
Quantum dot. A particle that exhibits properties of quantum
confinement.
Nanostructured/ Nanophase/ nanoscale material:
        Any solid material that has a nanometer dimension;
Colloid: A stable liquid phase containing particles in the 1-1000
nm range. A colloidal particle is one such 1-1000 nm sized particle
Cluster: A collection of units (atoms or reactive molecules) of up
to about 50 units. Cluster compounds are such moieties
surrounded by a ligand shell that allows isolation of a molecular
species (stable, isolable, soluble)
Size Relationships of Chemistry, Nanoparticles,
        and Condensed Matter Physics


                        Nanoscale              Condensed
   Atoms/Molecules                              Matter
                        Particles
   1                  125            70,000 6 x 106           ∞
                        Diameter 1-10 nm      Diameter 100-∞ nm
                                                Solid State
  Quantum Chemistry          ?                   Physics


  In the nanoscale regime, neither quantum chemistry nor
  classical laws of physics hold
Factors Affected by Size Reduction:
          Bulk vs. Nano

          Melting Points
         Optical properties
              Colors
         Surface Reactivity
        Magnetic properties
           Conductivity
           Specific heats
About 2/3 of the Chemical Elements
             are Metals
Matter has Unusual Properties on the nm Scale

If you take gold and
make particles about     ruby-red
10 nm in diameter, it    stained glass
looks wine-red or        from gold
blue-gray, depending     nanoparticles
on how close the
particles are together
Preparation of Au Nanoparticles by a
          Chemical Route



               Reducing agent

               Capping agent

                                Au nanoparticles
   Au3+ Salt
Transmission Electron Microscopy Images of Au Nanoparticles
Gold Nanospheres with Increasing
               Diameter Size




Bulk Au
                   4 nm     12 nm      25 nm     37 nm

• Optical properties of metal nanoparticles depend on their shape and size
• Particle functionalization can be done on the surface
• Visible optical changes occur
Origin of the Properties

               Bulk Metal                         Nanoscale metal

Unoccupied                       Decreasing
  states                         the size…

 occupied
  states
                                                   Separation between
             Close lying bands                       the valence and
                                                    conduction bands

       Unbound electrons have                Electron motion becomes
       motion that is not confined       confined, and quantization sets in

                                          Particle size < mean free path
                                                           of electrons
Band Structure in Metals

                       EF (Fermi Level)
                         EF depends on the density
        Density ρ = N/V (where N = Number of electrons, V = volume)

        Assuming all energy levels have the same number of electrons,
                                  δ = EF / N
                                Since N ∝ V

                            Therefore, δ ∝ 1/V
                V = L3 (where L = side length of the particle)
                                  Hence,
                                 δ ∝ EF/L3

As the side length of the particle decreases the energy level spacing increase
Gold Nanospheres with Increasing
               Diameter Size




Bulk Au
                   4 nm     12 nm      25 nm     37 nm

• Optical properties of metal nanoparticles depend on their shape and size
• Particle functionalization can be done on the surface
• Visible optical changes occur
Surface Plasmon Absorption of Au Nanoparticles




  Surface plasmon absorption in metal nanoparticles arises from the collective
  oscillations of the free conduction band electrons that are induced by the
  incident electromagnetic radiation.
Factors that Affect the Surface Plasmon
  Absorbance of Metal Nanoparticles
  Plasmon absorption of metal nanoparticles is
     sensitive to the surrounding environment

  1. Dielectric of the surrounding medium

  2. Solvents (nature of the solvent)
Dielectric Constant and its Effect of the
       Surface Plasmon Absorption Band

Position of the plasmon absorption band can be discussed
within the framework of the Drude model

                        λ2 = λp2 (ε∝ = 2εm)
Where λp is the bulk plasma wavelength, ε∝ is the high frequency dielectric
constants due to interband and core transitions, and εm is the medium dielectric
constant

      The refractive index is directly related to its dielectric constant

                                  n = (εm)1/2
Normalized surface plasmon absorption
        band of Au nanoparticles in cyclohexane
                and o-dichloromethane




                                                             J. Phys. Chem. B. 2002, 106, 7729
Inset shows the dependence of the square of the observed peak position of the surface plasmon
band as a function of twice the medium dielectric function. ( m was determined from the
expression, m = n2)
How Does SP Band of Alkanethiolate-Au
       Clusters Vary with Refractive Index

                                         The optical dielectric of the
                                         ligand shell, and not that of the
                                         solvent, dominates the Au cluster
                                         dielectric environment




                                             Langmuir 1998, 14, 17




Dodecanethiolate-stabilized Au cluster
Melting Points
Property is a consequence of the averaged coordination number
of the participating atoms

Typically, for bulk materials, surface atoms form a negligible
part of the total number of atoms

The smaller a particle becomes, the more the proportion of
surface atoms increases
Full shell clusters are constructed by successively packing layers
     – or shells – of metal atoms around a single metal atom
                The number of atoms per shell is
                  (Sum of atoms + 10n2 + 2)
                      where n = number of shell
The Relation Between the total number of atoms in
  Full shell (‘Magic Number’) clusters and the
           percentage of surface atoms
      Full-shell     Total      Surface
      Clusters     Number of   Atoms (%)
                    Atoms
        1 Shell        13           92
       2 Shells        55           76
       3 Shells       147           63
       4 Shells       309           52
       5 Shells       561           45
       7 Shells       1415          35
Relation Between the Size of Gold
                        Particles and Their Melting Point

                     1200
                     1000
Melting Point (oC)




                     800
                     600
                     400
                     200
                       0
                            0   1   2   3   4   5   6    7     8   9   10
                                        Particle Radius (nm)
Other Important Properties of Metal
          Nanoparticles

Gold nanoparticles have been shown to be
photoluminescent

Unique electrochemical properties

Gold nanoparticles have shown electron – acceptor
properties

Enhanced catalytic properties
Semiconductor Nanoparticles
       Group 14 (old group IV) Si, Ge

       III-V Materials: GaN, GaP, GaAs, InP, InAs

       II-VI Materials: ZnO, ZnS, ZnSe, CdS, CdSe, CdTe


Quantum dots are
semiconductors particles
that has all three
dimensions confined to the
1-100 nm length scale

                             Colloidal CdSe quantum dots dispersed in hexane
Energy Diagrams Illustrating the
Situation for a Nanoparticle, in Between
 a Molecule and a Bulk Semiconductor
                          NANOPARTICLE

          MOLECULE

          LUMO                           BULK SOLID
                                               CB
 Energy




                                 ∆E       Eg
                     ∆E
                                               VB
          HOMO
Quantum Confinement in
          Semiconductor Nanoparticles

Eg (quantum dot) = Eg(bulk) + ( h2/8R2) (1/me + 1/mh) – 1.8e2/4πε 0εR


       Eg = bandgap energy of a quantum dot or bulk solid
                      R = quantum dot radius
          mc = effective mass of the electron in the solid
           mh = effective mass of the hole in the solid
                ε = dielectric constant of the solid
                   ε0 = permittivity of a vacuum
Room-Temperature Spectra of CdSe
               Quantum Dots

(a) Absorption and
    photoluminescence spectra
    as a function of diameter

(b) Quantum yield of
    photoluminescence as a
    function of size. Squares
    represents deep-trap
    emission, and circles
    represent band-edge
    emission



    Murray, C. B. Synthesis and characterization of II-VI quantum dots and their
    assembly into 3D quantum ot superlattices. Ph.D Thesis, MIT, Cambridge , MA 1995
Inorganic Semiconductors




Trap states are caused by defects, such as vacancies, local
lattice mismatches, dangling bonds, or adsorbates at the
surface
Chemical Synthetic Routes for
  Metal and Semiconductor
Nanoparticles and Structures

     Additional Synthetic Approaches
                • Sonochemical
               • Electrochemical
                • Photochemical
          • Chemical Vapor Deposition
Aspects of Nanoparticle Growth in
                 Solution
                     Arrested precipitation
        Precipitation under starving conditions: a large number
        of nucleation centers are formed by vigorous mixing of
                         the reactant solutions.

          If concentration growth is kept small, nuclei growth is
                      stopped due to lack of material.
Particles had to be protected from Oswald Ripening by stabilizers
                         Oswald Ripening
         The growth mechanism where small particles dissolve,
           and are consumed by larger particles. As a result the
           average nanoparticle size increases with time and the
          particle concentration decreases. As particles increase
                        in size, solubility decreases.
Synthetic Approaches for Metal and
          Semiconductor Nanoparticles
              via Chemical Routes
       1. Metal Compound
    • Positively charge metal salt, or
     • Metal centers of complexes

2. Solvents (depends on the nature of the salt)
                         • Water
                • Polar organic solvents
             • Non-polar organic solvents
3. Reducing agent (determined by the nature of the metal compound)
                            • Gaseous hydrogen
                          • Hydridic compounds
                    • Reducing organics, e.g. alcohols
                                   Many others
Stabilization of Nanoclusters Against
             Aggregation
1. Electrostatic stabilization
       Adsorption of ions to the + - - - - - + - - - +
                                            -- - + -
    surface. Creates an electrical  - δ+ δ+ δ+ - δ+ δ δ+ --
                                   --          --
   double layer which results in a - δ+ δ+ -    + δ+ δ+ -
                                   + - - --- - --
                                     - -                -+
      Coulombic repulsion force                  +    -
     between individual particles


   2. Steric Stabilization
    Surrounding the metal center
    by layers of material that are
          sterically bulky,
        Examples: polymers,
           surfactants, etc
Synthetic Approaches for Metal and
     Semiconductor Nanoparticles
         via Chemical Routes
                         4. Stabilizers
                      Role of stabilizers:
Stabilizing agents/ligands/capping agents/passivating agents
             • prevent uncontrollable growth of particles
                    • prevent particle aggregation
                         • control growth rate
                        • controls particle size
           • Allows particle solubility in various solvents
Other Common Stabilizers
                      1. Organic ligands
   • Thiols (thioethanol, thioglycerol, mercaptoethylamine, etc)
                              • Amines
                            • phosphates

 2. Surfactants

  3. Polymers

  4. Solvents
         ether
       thioether

5. Polyoxoanions
Schematic Procedure for Cluster Synthesis

                        Add
                   electron donor     •• ••••
                                                              •• ••••••
      + ++                               ••                   ••• ••••
                                                               • •
      ++ +                              •• • • •
                                      • ••                    •• ••
                                                              ••••• •••
                                                               •
   Metal cations                    Metal atoms in              Cluster
    in solution                       solution                 formation




   Ligand
                             • •• •
                            •••• • •••••
                             • • •••           Isolation in
 molecules (•)             •••• •••• • •
                            •• • • •            solid form      •
                                                               ••••
                                                              •••••
                                                               ••
                            ••••••••• •••••
                             •••••• •••
                             •• ••
                              •         •                       •
Schematic Procedure for Cluster
               Synthesis

                   Add                         Add
                  Ligand                     electron
                molecules (•)                 donor
 ++ + +                           + +                    •••• •••• ••••
                                                         •• •• ••
                                                         •••• • •••• • ••••
 ++ +                           • +• • • +
                                                         • • ••• • •••
                                                            •• ••
                                                             •••• • ••••
 + ++                                                        •        •
                                    •• •
                                  • + +•                   •• •• ••
                                                         ••••••• ••••• ••••
                                                        ••••••••• ••
                                                                 • • • •
                                                        • ••••• • • •••
                                                        ••••• •• • ••
                                                            •
                                                        • • • • •
                                                            •• ••
                                                             ••• •••
Metal cations
 in solution                                             Stabilized
                                                        Metal particles
                                                         in solution
Synthesis of Metal Nanoparticles in
           Organic Media
Biphasic reduction procedure

                  Add phase
              transfer reagent    Extract
                e.g. tetraoctyl
                 ammonium
 Aqueous           bromide
                   (TOAB)
solution of
 metal salt                              Add
                                       Reducing
                                        agent
TEM Image of Au Nanoparticles Prepared
 in the Presence of a Surfactant (CTAB)




        CTAB = cetyltrimethylammonium bromide
                                J. Phys. Chem. B. 2001, 105, 4065
Nucleation and Growth
  Homogeneous nucleation occurs via a stepwise sequence of
bimolecular additions until a nucleus of critical size is obtained.
 a. Nucleation from supersaturated solution

                     nS             Sn
 b. Diffusion-Controlled Growth

                  Sn + S           Sn+1

                                   LaMer et al. J. Am. Chem. Soc. 1950, 72, 4847

Highly monodisperse nanoparticles are formed if the processes
   of nucleation and growth can be successfully separated

                 • Nucleation process must be fast
                  • Growth process must be slow
Nucleation
Nucleus Radius is calculated as follows:

                  ∆G = 4πσ(r2 – [2r3 / 3r*])

                                         Where r = nucleus radius
                                            r* = critical nucleus radius
                                            σ = surface tension



       ∆G(nucleus) = n(∆G formation, bulk – ∆G formation, free atom) + σA

                                      Where A = particle surface area
Dendrimer-Templated Nanocluster
              Synthesis
Structure of poly(amidoamine) dendrimer (PAMAM)




                           Generation 2 PAMAM Dendrimer
Dendrimer-Templated Nanocluster Synthesis
              Pioneered in 1998, by
       Donald A. Tomalia (Michigan Molecular Institute
                Richard M. Crooks (TAMU)

                                      Hydrazine
  PAMAM +             CuAc2          1 x 10-4 mol
 1 x 10-6 mol                                       Cu Nanoclsuters
                   1 x 10-5 mol

                                           Formation of Cu nanoclusters
                                           can be monitored by UV-vis
                                                spectrophotometry

                                            Reaction is pH dependent:
                                           Presumably H+ ions compete
                                           with Cu2+ ions for the tertiary
                                                   amine sites
                                              J. Am. Chem. Soc. 1998, 120, 4877
                                              J. Am. Chem. Soc 1998, 120, 7355
Reverse Micelles
                     Water-in-oil droplets

                              [H2O]
             Water pool w =
                            [surfactant]

 Particle size is controlled by the size of the water
      droplets in which synthesis takes place

Consider that:                            V = volume , R = radius,
                   R = 3V/A                   A = surface area



                      3Vaq[H2O]              σ = head polar group area
            Rw =                               Vaq = volume of water
                         σ[s]
Parameters Affecting Particle Growth/
         Shape/ Structure

•   Type of capping agent/stabilizers
•   Concentration of the reactants
•   pH value of the solution
•   Duration of heat treatment
Sonochemical Approaches for
            Nanoscale Particle Synthesis
                    Rectified Diffusion

 ‘area’ effect                              ‘shell’ effect

      +                          Bubble
Acoustic
pressure




                                 Liquid shell
     -
                                 Bubble
Sonochemical Approaches for
          Nanoscale Particle Synthesis
                            Step 1:
  • Bubble expands when surrounding medium experiences –ve
                           pressure

 • Bubble collapses when surrounding medium experiences +ve
                            pressure

• Bubble collapse leads to extreme temperatures (5,000 – 50, 000
           K), and pressure (100 atm) within the bubble

Step 2:
   Solvent or solute molecules present within the bubbles are
decomposed under these extreme conditions and generate highly
                       reactive radicals
Formation of Highly Reactive Radicals
 Depending on the liquid medium, sonication leads to the
     generation of oxidizing and reducing radicals

              In aqueous solution
               H2O         • H + •OH

           M+ + H •                M + H+


  In solutes like alcohols, sonication leads to secondary radicals
          RHOH + H (OH• )
                  •               ROH• + H2(H2O)

          ROH • + M+          M + RO + H+
Examples of Metal Nanoparticles
       Prepared by Sonication
 Ag nanoparticles prepared in aqueous solution at 1 MHz
                   H2O •          • H + OH

      Ag+ + H •             Ag + H+


                                 J. Phys. Chem. 1987, 91, 6687


Au nanoparticles prepared by sonication

                   ROH •
          AuCl4-           Au + Products

                               Langmuir 2002, 18, 7831-7836
Synthesis of CdS Nanoparticles
General:
              Anionic or
Cd(II) salt + Lewis basic   + Sulfide               1-10 nm
               polymers       source                  CdS




                   Sodium
Cd(NO3)2.4H2O + polyphosphate + Na2S                CdS
   2 x 10-4 M    2 x 10-4 M    2 x 10-4 M
                                    Chem. Mater. 1999, 11, 3595
Synthesis of CdSe Nanoparticles

      General:                             High
                        Phosphine oxide
Cd(CH3)2 + Se reagent +                 temperature
                           surfactant                             CdSe



                                  HAD-TOPO-TOP
   Cd(CH3)2 +       (C8H17)3PSe                         CdSe


HAD-TOP-TOP = hexadecylamine-trioctylphosphine oxide-trioctylphosphine
                                      J. Am. Chem. Soc. 1993, 115, 8706
Synthesis of ZnSe Nanoparticles


Zn(CH3CH2)2 +   (C8H17)3PSe                       Zn/Se TOP
                                                   Solution
Zn/Se TOP + Hexadecylamine 270 C
                              o
                                              ZnSe
 Solution
                                J. Phys. Chem. B. 1998, 102, 3655



     TOPO binds too strongly to Zn
          TOP binds too weakly
Amines, however have intermediate strength
Synthesis of III-V Semiconductor
                Nanoparticles
Synthesis of III-V semiconductor nanoparticles is quite complex
                   Requires high temperature

                                                     370 – 400 oC
GaCl3 + tris-(trimethylsilyl)phosphine + TOPO-TOP                    GaP


   GaP particles prepared in this manner lacked monodispersity


            GaCl3 + As(SiMe3)3         ~ 700 oC         GaAs
                                                        Chem. Mater. 1989, 1, 4
                                              J. Am. Chem. Soc. 1990, 112, 9438
Synthesis of InP and InCl3
                               260 oC, TOP InP nanocrystals
      InCl3 + [(CH3)3Si]3P



Synthesis of InAs via Dehalosilylation
                             Me3SiCl      Me3SiCl      Me3SiCl
                             evolved      evolved      evolved
 InCl3 + (Me3Si)3As                                              InAs
                      3 days, rt       70-75 C
                                            o
                                                     150 C
                                                        o

                                        4 days       4 days

                                            Chem. Mater. 1989, 1, 4
Factors Affecting the Nature of the
              Nanoparticle

•   Particle size and shape
•   Surface properties
•   Particle-solvent interactions
•   Particle-particle interactions
Common Methods for Nanoparticle
            Characterization
                                    Surface state

Particle   Surface          Surface                   Surface
 Size       Area          composition                structure;
                                                    Topography
                         Surface
                        Complexes
 Electron Microscopy
  X-ray diffraction                                   LEED
Magnetic Measurements          AES,                    SEM
                               XPS,                    TEM
                              SIMS,                   EXAFS
                              EPMA,
                              EXAFS

                               IR, UV-Vis, ESR, NMR, Raman
UV-Visible Spectroscopy

 • Particularly effective in characterizing semiconductor and
                          metal particles

• Useful for metal nanoparticle characterization whose surface
  plasmon absorbance lies in the visible range, e.g. Cu, Au, Ag

          • Can be used to determine particle size:
(For semiconductor nanoparticles: as the radius decreases, the
      band gap increases and λmax shifts to lower energy.

                    • Particle aggregation

 • Information about the surface, e.g. presence of adsorbates
Infrared Spectroscopy
      IR has been used as a surface probe for nanostructures

              Example illustrated by Bardley:
Adsorbing CO onto the metal nanoparticle surface resulted in IR
                 depending on particle size

                                                More face:
                More edge:
                                                bridged CO
                linear CO is
                                                  is stable
                   stable 2.5 nm 4 nm    6 nm


As particle size increased, the ratio of terminal CO to bridging
                         CO decreased et al. Chem. Mater. 1992, 4, 1234
                                   Bradley,
Nuclear Magnetic Resonance (NMR)
                    Two uses:
 1. Probing the ligands that surround metal core
2. Probing the intra-core metallic atoms (difficult)

             Probing the intra-core metallic atoms
Nuclear spin relaxation time, and nuclear resonance frequency,
are sensitive to any metallic property the particle may exhibit
Change in frequency (known as ‘Knight shift’) is a consequence
of the interaction of the metal nucleus with the conduction band
                            electrons
  If particles are very small, in favorable cases, the Knight shift
  allows resonances for surface and interior metal particles to be
                              identified
Microscopy

• TEM: High voltage beam passes through a very thin
  sample. The sample areas that do not allow passage of
  electrons allow image to be presented

• STM: Involves dragging a sharp needlelike probe across a
  sample very close to the surface. The tunneling current
  between the sample and probe tip can be monitored . As
  probe approaches an elevated portion, the probe moves up
  and over, and produces a surface map.

• AFM: The probe tip is essentially touching the surface,
  and the surface can be mapped by the weak interaction
  between the tip and the sample.
Transmission Electron Microscopy
    • Provides direct visual information of size, shape, dispersity,
                       structure and morphology

             • Routine magnifications > 40,000 to 0.2 nm

                            Drawbacks
  • Samples are dried and examined under high vacuum conditions

• Therefore, no direct information is gained on how particles exist in
                                solution

  • Only a finite number of particles can be examined and counted,
      which may not be a representative of the sample as a whole

  • Requires electron beam in which case, some nanoparticles may
  undergo structural rearrangement, aggregation or decomposition.
Scanning Tunneling Microscopy (STM)

  Makes possible the determination of the total diameter of the
      nanoparticle, including the stabilizing ligand shell
  Effective probe of the electronic properties of nanoparticles
                               Reetz et al. Science 1995, 267, 367-369


A combined STM/TEM study of Pd nanoparticles stabilized by
                      R4N+Br-.

 Determined thickness of stabilizing ligand shell by subtracting
   the STM determined diameter from the TEM determined
                           diameter
Shortcomings to STM
• Nanoparticles may not stick well to the substrate surface,
  preventing good images from being obtained

• Geometry of the tip shape may lead to inaccurate
  measurements or artifacts in the image

• Tunneling mechanism is not well understood

• Samples have to be dried

• Specific techniques applied to imaging are not mature, i.e.
  standard literature protocols have not been established
Atomic Force Microscopy
• Technique is purely mechanical
   – A cantilevered tip attached to a spring is dragged across
     a sample
   – Increase or decrease in tip height is measured yielding a
     surface height profile as a function of distance
   – Can be carried out on non-conducting samples

                        Shortcomings
    • Can reliably determine particle height but not diameter

  • Cannot distinguish between subtle shape differences, or
     image particles that are not spatially close to each other
High Aspect Ratio Nanoparticles
        • What is a high aspect ratio nanoparticle?

• Aspect ratio refers to the ratio of a particles length to its
                             width
                            Aspect ratio = length
                            width

• High aspect ratio nanoparticles have elongated structure
         Examples: nanotubes, nanowires, nanorods

• Often have distinctive properties as opposed to the bulk
              materials or even spherical particles

          e.g. Chemical, electrical, magnetic, optical, etc.
Types of High Aspect Ratio Nanoparticles
Nanowires                                                        Aspect ratio
                                 Synthetic Method
Ni, Au, Pt, Ag, Co, Cu, ZnO   Templated electrodeposition          Up to 250
    TiO2, ZnO, SiO2                         Sol-gel                   250
         Silicon              Nanocluster-mediated vapor-liquid-     > 100
                                         solid growth                > 20
MnO2, Fe2O3, Cu2O, Pd,          Electrodeposition on graphite
     Cu, Au, Ag                             surface
Nanotubes
 Gold                         Templated electroless deposition       250
 Silica                                    Sol-gel                   250
Carbon                            High temperature: laser           > 100
                               ablation, arc discharge, others

Nanorods
Gold                          Surfactant/seed mediated synthesis      ~20
CdSe                          Surfactant/seed mediated synthesis     2-10
 Cu                                    Micellar growth              1.7-3.7
 Se                                    Crystal growth                > 100
UV-Visible Absorption Spectrum of
Au Nanorods with Aspect Ratio 3.3




                     J. Phys. Chem. B. 1999, 103, 3073
Synthesis of Au Nanorods
1.    Formation of 4 nm “seed” by reduction of HAuCl4

          HAuCl4                          NaBH4
          solution
                     + Sodium citrate

2.    Seed-mediated growth in the presence of cetyltrimethylammonium
       bromide (CTAB) produces rod-like Au spheroids and nanorods

           HAuCl4
          Solution   + ascorbic acid
          in CTAB
     3.    Seed-mediated growth in the presence of cetyltrimethyammonium
          bromide (CTAB) of rod-like Au nanoparticles leads to Au nanorods

           HAuCl4
          Solution
                     + ascorbic acid
          in CTAB

                CTAB = cetyltrimethylammonium bromide (a surfactant)
Increase in Intensity of the Longitudinal
Plasmon Band with Increase in Nanorod
             Concentration




                            Chem. Mater. 2003, 15, 1957
TEM Image of Au Nanorods Prepared
 by a Seed-Mediated Growth Method




Aspect Ratio = 13




          J. Phys. Chem. B. 2001, 105, 4065
Gold Nanoparticles with Increasing
         Aspect Ratio


             Increasing aspect ratio


 1
                                                         18




         Obare, S. O.; Jana, N. R.; Murphy, C. J. Unpublished results
Increase in Aspect Ratio of Au
Nanoparticles Shifts the Longitudinal
     Plasmon Band to the NIR




                          Chem. Mater. 2003, 15, 1957
Calculated absorption spectra of Au nanoparticles
    with Varying Medium Dielectric Constant




   Link, S.; Mohamed, M. B.; El-Sayed, M. A. J. Phys. Chem. B. 1999, 103 (16), 3073-3077
Synthesis of Ag Nanorods and Nanowires
 Formation of 4 nm “seed” by reduction of AgNO 3

      AgNO3                            NaBH4
      solution
                  + Sodium citrate                              Ag seed

  Formation of Ag nanorods; aspect ratio was varied by changing the
                                  seed
                 concentration; pH is higher ~ 11.8
       AgNO3
       solution   + ascorbic acid     NaOH

                   Formation of Ag nanowires; pH is low



       AgNO3      + ascorbic acid
       solution                       NaOH

            CTAB = cetyltrimethylammonium bromide (a surfactant)
TEM Images of Silver Nanorods and
          Nanowires




                        Chem. Commun. 2001, 617
Silver Nanoparticles with Increasing
           Aspect Ratio

                        Increasing aspect ratio

1                                                         10




    Murphy, C. J.; Jana, N. R. Adv. Mater. 2002, 14, 80
Electrochemical Synthesis of
                Nanoparticles
     Synthesis of High Aspect Ratio Nanoparticles
    Nanoporous Membrane Templated Fabrication


                                              SEM image of typical
                                                alumina membrane.




Typically membranes consists of
     1. Anodized alumina
  2. Track etch polycarbonate              www. whatman.com
                                  J. Vac. Sci. Technol. B 2003, 35, 1097
Nanowire Synthesis by Electrodeposition

                                Sputter                Place membrane in
                               copper on               aqueous solution of
                                bottom                     metal salt

 Nanoporous alumina membrane




                                                                M+
                Apply potential
                                                                    e- -
                                                                    e
                                                        M+(aq) + e-          M(s)

              Remove copper                Dissolve alumina
              with CuCl/HCl                 in warm .5 M
                 solution                        KOH
Current–Time Transient for the Deposition of 60 nm
Nickel Nanowires into a 6 µm Polycarbonate Template




       Science 1993, 261, 1316
The Sol-Gel Process
M-O-R + H2O → MOH + R-OH                    (Hydrolysis)

M-OH + HO-M → M-OH + H2O                   (Condensation)
                           Sol                Gel
    Metal
              Hydrolysis         Gelling
   Alkoxide
   Solution
Sol-Gel Synthesis for High Aspect
            Ratio Fabrication

             Materials synthesized by sol-gel method:

    TiO2: Chem. Mater. 1997, 9, 2544, Adv. Mater. 1994, 8, 857.
                 CdS: Adv. Mater. 2001, 13, 1393.
SiO2: Chem. Mater. 1997, 9, 2544. J. Am. Chem. Soc. 1995, 117, 2651
              In2O3: J. Mater. Chem. 2001, 11, 2901.
             Ga2O3: J. Mater. Chem. 2001, 11, 2901.
                V2O5: Chem. Mater. 1997, 9, 2544
                MnO2: Chem. Mater. 1997, 9, 2544
                WO3: Chem. Mater. 1997, 9, 2544
SEM Image of TiO2 Nanostructures
     Prepared by the Sol-Gel Process




SEM image of TiO2 nanostructures obtained by immersing the template membrane in the
                        sol for (A) 5, (B) 25, and (C) 60 s.
SEM Image of MnO2 Nanostructures
  Prepared by the Sol-Gel Process




SEM image of MnO2 fibers prepared in the 200-nm-pore-diameter alumina
                        template membrane
SEM Image of V2O5 Nanostructures
 Prepared by the Sol-Gel Process




 SEM images of the template-synthesized V2O5 microstructures
SEM Image of Co3O4 Nanostructures
  Prepared by the Sol-Gel Process




  SEM image of Co3O4 fibers prepared in the 200-nm-pore-diameter
                  alumina template membrane
Synthesis of Carbon Nanotubes
     Synthesis of carbon                       1993, Nature 1993, 363, 603
                                      Iijima an coworkers first synthesized carbon
   nanotubes involves high             nanotubes via the thermal decomposition of
   temperature approaches                             hydrocarbons.
                                     High temperature decomposition of vapors such
                                     as benzene or acetylene, in the presence of Co,
                                     Fe, or Ni catalysts, formed single walled carbon
                                                    nanotubes.

                                              1996, Science 1996, 273, 483
                                     Laser Ablation method (Smalley and coworkers)
                                     Method produced nanotubes formed into ropes of
                                     100-500 carbon nanotubes, at yields of more than
                                                         70%.
A single walled carbon nanotube
                                                2002, Nano Lett. 2002, 2, 1043
Carbon nanotubes are cylindrical      Catalyst-free synthesis (Avouris and coworkers)
structures consisting of rolled-up   Method developed for carbon nanotube synthesis
  graphene sheets with fullerene       on a silicon surface. Advantage is that catalyst
              caps.                  removal is not necessary for purification.
Ligands and the Surfaces they are
              Reported to Functionalize
Ligand       Name                Surface            Proposed
                                 modified            linkage
 R–S–H           Thiols
                               Au, Ag, Cu, Hg, Fe
R–S–S–R        Disulfides
 R–C N        Isocyanides            Pt, Pd
            Carboxylic acids      Metal oxides
             Phosphonates         Metal oxides
               Siloxanes          Metal oxides
            Hydroxamic acids      Metal oxides
Selective Functionalization



       1-butaneisocyanide




    2-mercaptoethylamine


                            Adv. Mater. 1999, 11, 1021
Applications of High Aspect Ratio
              Nanoparticles
Several applications of high aspect ratio nanoparticles have been
        shown, and many others continue to be unfolded

                 Applications is areas such as:
                             •Biology
                          •Gene therapy
                         •Bioseparations
                           •Separations
                            •Catalysis
                             •Sensing
                           •Electronics
                      •Optical applications
                                Etc.
Nanowire Synthesis by Electrodeposition

                                Sputter                Place membrane in
                               copper on               aqueous solution of
                                bottom                     metal salt

 Nanoporous alumina membrane




                                                                M+
                Apply potential
                                                                    e- -
                                                                    e
                                                        M+(aq) + e-          M(s)

              Remove copper                Dissolve alumina
              with CuCl/HCl                 in warm .5 M
                 solution                        KOH
Au-Ni-Au Nanorods Bound and Unbound
      to Fluorescein-tagged Poly-His
                                           Confocal fluorescence
                                         image of Au-Ni-Au after
                                         modification of Ni portion
                                          with Fluorescein-tagged
                                                  poly-His



  SEM image of Au-Ni-Au
       Nanowires



Angew. Chemie. Int. Ed. 2004, 43, 3048
Exposure of Fluorescein-tagged Poly-His
        Proteins to Au-Ni-Au Nanorods




 Left: Fluorescein-tagged poly-His
              solution

Right: Fluorescein-tagged poly-His
Solution after exposure to Au-Ni-Au
              Nanorods                Angew. Chemie. Int. Ed. 2004, 43, 3048
Separation of His-tagged Proteins
from a Non-His-tagged Structures

                 a. Solution of IgG protein (no
 a   b    c           His)-Green Alexa dye
                      mixed with His-tagged
                     protein-Red Alexa Dye

                  b. After exposure to Au-Ni-
                      Au; (non-His protein
                       remains in solution)

                 c. Separated Au-Ni-Au from a
                            in solution

                    Angew. Chemie. Int. Ed. 2004, 43, 3048
Smart Nanotubes for Bioseparations
        and Biocatalysis




                   J. Am. Chem. Soc. 2002, 124, 11864
Smart Nanotubes for Bioseparations
              and Biocatalysis
                                                Nanotubes preferentially
                                              reside in cyclohexane due to
          Vial containing cyclohexane            the outer hydrophobic
           (upper) and water (lower)                     surface




                            Add nanotubes A
cyclohexane

      H2 O



    Nanotubes A. Dansylamide on inner void and C 18 on outer surfaces
   Danyslamide dye fluoresces green             J. Am. Chem. Soc. 2002, 124, 11864
Smart Nanotubes for Bioseparations
              and Biocatalysis

                                                Nanotubes preferentially
          Vial containing cyclohexane         reside in Aqueous phase due
           (upper) and water (lower)             to the outer hydrophilic
                                                          surface



                            Add nanotubes B
cyclohexane

      H2 O



    Nanotubes B. Quinineurethan on inner and no silane on outer surfaces
   Quinineurethan dye fluoresces blue           J. Am. Chem. Soc. 2002, 124, 11864
Smart Nanotubes for Bioseparations
              and Biocatalysis
                                               Nanotubes A preferentially
                                              reside in Organic phase while
          Vial containing cyclohexane
                                                nanotubes B reside in the
           (upper) and water (lower)
                                                      aqueous phase




                            Add nanotubes A
cyclohexane                 Add nanotubes B

      H2 O


    Nanotubes A. Dansylamide on inner void and C 18 on outer surfaces
    Nanotubes B. Quinineurethan on inner and no silane on outer surfaces
                                                J. Am. Chem. Soc. 2002, 124, 11864
Multifunctional Nanorods for Gene Delivery
                                                              Nature Materials 2003, 2, 668

      Goal of gene therapy: to introduce foreign cells into somatic cells to
     supplement defective genes, or provide additional biological functions

                                    H2N                          H2N
                       S-S                             S-S                DNA*
            HOOC                          OOC


   Au Ni
                        HN-DNA*                                             HN-DNA*
               S-S                                               S-S
      OOC                                        S-T   OOC
                             HS-Transferrin


                                                               Observations
                                          1.    Nanorods were internalized into the cell but did not
                                                                 enter the nucleus
                                             2.    GFP was observed in the nucleus indicating
                                                   delivery of the reporter gene to the nucleus
                Human kidney cell             3.    Au-S-T served to promote cellular uptake
                                             4.   Disulfide linkage acts as a cleavable point to
                                                     promote release of DNA within the cell
DNA* = DNA plasmids which encodes Green fluorescent Protein GFP
What is Nanoparticle
   Engineering/Surface Modification
Tailored synthesis of core-shell nanoparticles
  with defined morphologies and properties

                              shell

                           core
Why Surface Modification?
  1. The shell can alter the charge, functionality, and
                 reactivity of the surface

2. The shell can enhance the stability and dispersibility
                   of the colloidal core

  3. Magnetic, optical, or catalytic functions may be
     readily imparted to the dispersed colloidal core

4. Encasing colloids in a shell of different composition
   may also protect the core from extraneous chemical
                  and physical changes
Effects of Surface Modification
Chemical and Colloidal Stability
               • Nanoparticle degradation through chemical etching
    • Agglomeration caused by strong van der Waals attractive forces

Tuning of Physical Properties
              For example, the optical properties of metal nanoparticles are
         influenced by their environments. Controlled surface modification can
                                  alter these properties


Control of Interparticle Interactions Within Assemblies
     •       Collective properties of nanoparticle assemblies are influenced to a
                     large extent by the separation between the particles.

         •    Coating the particles with a uniform shell of inert material could
                         control the distance between the particles
Types of Core-Shell Nanoparticles


          • Metal-Polymer
            • Metal-Metal
  • Semiconductor- Semiconductor
       • Semiconductor-Metal
      • Metal - Semiconductor
Polymers on Metals

• Main reason is for nanoparticle stabilization
• Could also be used to assemble nanoparticles

• Examples:
   –   Chem. Mater. 1998, 10, 1214
   –   J. Am. Chem. Soc. 1999, 121, 8518
   –   Adv. Mater. 1999, 11, 34
   –   Adv. Mater. 1998, 10, 132
   –   Chem. Commun. 1998, 351
   –   Adv. Mater. 1999, 11, 131
   –   J. Am. Chem. Soc. 1999, 121, 10642
   –   Nano Lett. 2002, 2, 3
Sketch of the surface reactions involved in
the formation of a thin silica shell on citrate-
          stabilized gold particles




                                 Langmuir 1996, 12, 4329
UV-visible spectra of sodium citrate-
stabilized, 15 nm diameter gold colloids 1
day after addition of different amounts of
                   APS
                         APS: polymerization initiator
                        3-aminopropyltrimethoxysilane




                                 Langmuir 1996, 12, 4329
15 nm gold particles coated with thin
                 silica layers




  18 hours after addition         42 h after addition           5 days after addition
      of active silica
The silica shell keeps on growing, but eventually small silica particles also nucleate out
                                    of the solution.
                                                             Langmuir 1996, 12, 4329
Silica-Coated Au Nanoparticles

                                                                            Langmuir 1996, 12, 4329




Transmission electron micrographs of silica-coated gold particles produced during the extensive
growth of the silica shell around 15 nm Au particles with TES in 4:1 ethanol/water mixtures. The
shell thickness are (a, top left) 10 nm, (b, top right) 23 nm, (c, bottom left) 58 nm, and (d, bottom
                                              right) 83 nm
Influence of thin silica shells on the UV-
 visible spectra of aqueous gold colloids




  Experimental                   Calculated

                         Langmuir 1996, 12, 4329
Influence of thick silica shells on the UV-
 visible spectra of ethanolic gold colloids




   Experimental                Calculated
                               Langmuir 1996, 12, 4329
Effect of Solvent Refractive Index on the
Color of Dispersions of 15 nm Gold Particles
          with a 60 nm Silica Shell




   The solvent refractive indices (left to right) are 1.45, 1.42, 1.39, and 1.36

                                                          Langmuir 1996, 12, 4329
Silica Coating of Silver Colloids
                                NaBH4
    AgClO4 + sodium citrate                 10 nm Ag nanoparticles

    Ag + 3-aminopropyltrimethoxysilane + sodium silicate       Ag@SiO2
nanoparticles
Silicate ion concentration
              0.02 %             0.01 %                    0.005 %




                                                 Langmuir 1998, 14, 3740
Emulsion Polymerization
Emulsion polymerization is a type of polymerization that takes place in an
emulsion typically incorporating water, monomer, and surfactant. The most
 common type of emulsion polymerization is an oil-in-water emulsion, in
 which droplets of monomer (the oil) are emulsified (with surfactants) in a
                        continuous phase of water.

                                                       In aqueous solution




     surfactant



         Monomer + free radical initiator → Polymer
Polymer-Coated Silver Nanoparticles




  TEM images of silver particles: (A) uncoated particle, (B) polystyrene/methacrylate
 coated particles, (C) polystyrene/methacrylate coated particles with a covalently bound
BSA layer, and (D) the same as panel C after exposure to gold colloids. Negative staining
                        by phosphotungstic acid used for all images

                                                   J. Am. Chem. Soc. 1999, 121, 10642
Preparation of Polymer-Coated
           Functionalized Silver Nanoparticles




  Extinction spectra of silver particles: (A) uncoated particles and (B) polystyrene coated
particles. Solid line: suspension in water. Dotted line: suspension in water, after 1 h in 1.8 M
                                             NaCl
                                                        J. Am. Chem. Soc. 1999, 121, 10642
Synthetic Protocols for the Synthesis of Coupled
                1D Nanoparticle Arrays

 Procedures for (A) Ppy-
   linked Au Colloids




Alkyldithiolate-Linked
     Au Colloids

 Ppy = poly(pyrrole)




                                 Chem. Mater. 1998, 10, 1214
Au Colloids Linked by PPy




Transmission electron microscope images of 1D and near-
        1D arrays of Au colloids linked by Ppy
                                         Chem. Mater. 1998, 10, 1214
Semiconductor on Semiconductor
Tailoring optical properties

Enhancing the luminescence


   Shell




                               Energy
     Core                               core
                                                              shell
                                               shell   core
Energies of Various Semiconductors

                                                                  TiO2
                        GaP
 Energy (eV)


               GaAs                  CdS
                              CdSe          ZnO            TiO2
                                                    WO3
               1.4                                                3.0
                      2.25
                              1.7    2.5
                                           3.2            3.2
                                                  3.2




 Values at pH = 1
Inorganic Semiconductors




Trap states are caused by defects, such as vacancies, local
lattice mismatches, dangling bonds, or adsorbates at the
                         surface
Examples for Semiconductor-
Semiconductor Core-Shell Nanoparticles
   Examples include:
       ZnS on CdSe
       CdS on CdSe
      CdSe on CdS, etc


      J. Phys. Chem. B. 1997, 101, 9463
      J. Phys. Chem. B. 1998, 102, 1884
         J. Phys. Chem. 1993, 97, 5333
        J. Phys. Chem. 1996, 100, 6381
        J. Phys. Chem. 1996, 100, 8927
       J. Phys. Chem. 1996, 100, 13226
      J. Phys. Chem. 1996, 100, 20021
CdSe Coated with ZnS Nanoparticles
Me2Cd + TOPSe                  CdSe
                                   300 oC
       (TMS)2/Me2Zn/TOP



                                   ∆T

                 ZnS


                  CdSe


   J. Phys. Chem. 1996, 100, 468            TEM picture of (CdSe)ZnS nanocrystals
CdSe Coated with ZnS Nanoparticles
                                                   J. Phys. Chem. 1996, 100, 468




 Absorption spectrum of the (CdSe)TOPO
      (dotted line) and the (CdSe)ZnS         Normalized fluorescence spectra of CdSe-TOPO
nanocrystals (solid line). The fluorescence    (dotted line) and CdSe@ZnS (solid line) with
of the (CdSe)ZnS is also shown (solid line)                   470 nm excitation
Observations on the Optical Characteristics
       of CdSe/ZnS Nanoparticles

 Fluorescence of CdSe-TOPO shows the broad tail, due to
                     surface traps.

  CdSe/ZnS fluorescence spectrum has a flat baseline; this
indicates that the ZnS reduces the traps present on the CdSe
                      (TOPO) surface

 Fluorescence of CdSe (CdSe/ZnS) was stable for months
              compared to uncapped CdSe

No reduction in the CdSe quantum yield was observed for
       months with the CdSe/ZnS nanoparticles
                                       J. Phys. Chem. 1996, 100, 468
Synthesis of HgS/CdS Core-Shell
             Nanostructures
                                              J. Phys. Chem. 1993, 97, 5333
 HgScore CdSshell
         HgCl2 + H2S + sodium polyphosphate → HgS

         HgS + Cd(ClO4)2 + H2S → HgS/CdS

CdScore HgSshell

       Cd(ClO4)2 + H2S + sodium polyphosphate → CdS

       CdS + HgCl2 + H2S → CdS/HgS

           Note: Due to the much lower solubility of HgS compared with CdS
                     particles result in an exchange of Cd2+ by Hg2+
                    (CdS)n + mHgCl2 → (CdS)n-m(HgS)m + mCdCl2
CdS/HgS Mixed Colloids
                       J. Phys. Chem. 1993, 97, 5333




HgS nanoparticles   HgS coated with CdS
Absorption Spectra of Core-Shell CdS
       on HgS Nanoparticles
                      J. Phys. Chem. 1993, 97, 5333




 A = HgS
Fluorescence Spectra of Core-Shell
    CdS on HgS Nanoparticles
                                    HgS nanoparticles do not
                                           fluoresce

                                  CdS coated HgS nanoparticles
                                            fluoresce:
                                             Possibly due to
                                    removal of traps for
                                 nonradiative      recombinations
                                                     or
                                            Fluorescence could
                                            arise from band to
                                          band recombination in
                                                 HgS core

 J. Phys. Chem. 1993, 97, 5333
CdS/HgS Mixed Colloids




               J. Phys. Chem. 1993, 97, 5333
Metal – Metal Core-Shell
                  Nanostructures
Examples reported in the literature

         Au/Ag : J. Chem. Phys. 1964, 41, 3357-3363
   Au/Cd : Ber. Bunsenges. Phys. Chem. 1994, 98, 180-189
    Au/Pb : Ber. Bunsenges. Phys. Chem. 1994, 98, 180-189
          Au/Sn : J. Phys. Chem. 1994, 98, 6931-6935
    Au/Tl : Ber. Bunsenges. Phys. Chem. 1994, 98, 180-189
    Ag/Pb : Ber. Bunsenges. Phys. Chem. 1992, 96, 754-759
          Ag/Cd : J. Phys. Chem. 1994, 98, 6931-6935
   Ag/In : Ber. Bunsenges. Phys. Chem. 1992, 96, 2411-2414
        Au/Pt : J. Phys. Chem. B. 2000, 104, 2201-2203
Pt/Au Core-Shell Nanoparticles
 Synthesis of Aucore Ptshell Nanoparticles
                                High T
NaAuCl4 + sodium citrate                 Au nanoparticles (~ 20 nm)
                                   H2
         PtCl   4
                 2-
                      + Au nanoparticles                 Au/Pt


Synthesis of Ptcore Aushell Nanoparticles
                                 H2
 PtCl4 + sodium polyacrylate
      2-
                                       Pt nanoparticles (~12 nm)
                                γ-rays
       Pt nanoparticles + K2Au(CN)2
                                MeOH
                                                                Pt/Au

                                         J. Phys. Chem. B. 2000, 104, 2201-2203
PtcoreAushell Nanoparticles


Pt nanoparticles   1:1 Pt/Au nanoparticles   1:2 Pt/Au nanoparticles




                                  J. Phys. Chem. B. 2000, 104, 2201-2203
Pt/Au Core-Shell Nanoparticles
                                         J. Phys. Chem. B. 2000, 104, 2201-2203




Absorption spectra of Pt nanoparticles
before and after deposition of various
     amounts of gold. Overall Pt
     concentration is 1 x 10-4 M
Concentration of Pt:Au is given on the    Absorption spectra of Au nanoparticles
                curves                     before and after deposition of various
                                         amounts of Pt. Overall Au concentration:
                                         3 x 10-4 M Molar of Au:Pt is given on the
                                                           curves
AucorePtshell Nanoparticles




Electron micrograph of Au core particles before (left) and after (right)
                  deposition of Pt in the ratio 1:2
                                  J. Phys. Chem. B. 2000, 104, 2201-2203
Metal-Semiconductor Core-Shell
           Nanoparticles
    Metals can be used as templates to make hollow semiconductor
                            nanostructures

     Fabrication of composite nanoparticles with a large electronic
capacitance, i.e. a large difference in the Fermi level of the core relative
to the conduction band edge of the shell will enable electrons to diffuse
       through the shell and be trapped in the core for a long time

                               Examples:
                   Au/CdSe: J. Mater. Res. 1998, 13, 905-908
                  Au/CdS: J. Phys. Chem. B. 1997, 101, 7675
                    Ag/TiO2: Langmuir 2000, 16, 2731-2735
                  Au/TiO2: J. Phys. Chem. B. 2000, 104, 10851
                    TiO2/Ag: Langmuir 1999, 15, 7084-7087
                ZnO/Au: J. Phys. Chem. B. 2003, 107, 7479-7485
Au/CdS Composite Nanoparticles




 Au nanoparticles   Au/CdS composite
                      nanoparticles
                        J. Phys. Chem. B. 1997, 101, 7675
Synthesis of CdS-Capped Au
             Nanoparticles

                           High T
NaAuCl4 + sodium citrate            Au nanoparticles (~ 20 nm)




  MNA = 2-mercaptonicotinic acid
                                        J. Phys. Chem. B. 1997, 101, 7675
Absorption Spectra of Au/CdS
      Nanocomposites

                                      Absorption properties
                                      of Au/CdS are not the
                                        result of a simple
                                          addition of the
                                          spectra of two
                                         nanoclusters, but
                                      rather an influence of
                                       the CdS on the Au.
  Au
               Au/CdS
Au/MNA
         CdS




                        J. Phys. Chem. B. 1997, 101, 7675
Emission Spectra of Au/CdS
                 Nanocomposites




  Emission quenching of CdS is
  indicative of the occurrence of
electron transfer from excited CdS
         into the Au core.

Conduction band energy for CdS =
         - 1.0 V vs. NHE

  Fermi level of Au = + 0.5 V vs.    J. Phys. Chem. B. 1997, 101, 7675
               NHE

More Related Content

What's hot

Surface modification of nanomaterials
Surface modification of nanomaterialsSurface modification of nanomaterials
Surface modification of nanomaterialszenziyan
 
Nanomaterial and their application
Nanomaterial and their applicationNanomaterial and their application
Nanomaterial and their applicationPreeti Choudhary
 
Synthesis and characterization of nanocomposites
Synthesis and characterization of nanocompositesSynthesis and characterization of nanocomposites
Synthesis and characterization of nanocompositessowmya sankaran
 
Synthesis and characterization of nanocomposites
Synthesis and characterization of nanocompositesSynthesis and characterization of nanocomposites
Synthesis and characterization of nanocompositessowmya sankaran
 
Solvothermal method mithibai college msc part 1 pradeep jaiswal
Solvothermal method mithibai college msc part 1 pradeep jaiswalSolvothermal method mithibai college msc part 1 pradeep jaiswal
Solvothermal method mithibai college msc part 1 pradeep jaiswalPradeep Jaiswal
 
Polymer nanocomposites
Polymer nanocompositesPolymer nanocomposites
Polymer nanocompositesamzad hossain
 
Nanomaterials
NanomaterialsNanomaterials
NanomaterialsMaya Bhat
 
Nano particles synthesis
Nano particles synthesisNano particles synthesis
Nano particles synthesisinamchemist
 
Synthesis of Nanomaterials
Synthesis of NanomaterialsSynthesis of Nanomaterials
Synthesis of NanomaterialsAnantha Kumar
 
Synethsis method
Synethsis methodSynethsis method
Synethsis methodabdul latif
 
Nano architecture: self assembly and template methods.
Nano architecture: self assembly and template methods.Nano architecture: self assembly and template methods.
Nano architecture: self assembly and template methods.sana shaikh
 
POLYMER MODIFICATION WITH CARBON NANOTUBES
POLYMER MODIFICATION WITH CARBON NANOTUBESPOLYMER MODIFICATION WITH CARBON NANOTUBES
POLYMER MODIFICATION WITH CARBON NANOTUBESArjun K Gopi
 
Properties of nano materials
Properties of nano materialsProperties of nano materials
Properties of nano materialsMohd. Bilal
 
Nano technology fabrication methods
Nano  technology fabrication methodsNano  technology fabrication methods
Nano technology fabrication methodskamal330
 

What's hot (20)

Nanomaterials
NanomaterialsNanomaterials
Nanomaterials
 
Nanocomposite
NanocompositeNanocomposite
Nanocomposite
 
Surface modification of nanomaterials
Surface modification of nanomaterialsSurface modification of nanomaterials
Surface modification of nanomaterials
 
Nanomaterial and their application
Nanomaterial and their applicationNanomaterial and their application
Nanomaterial and their application
 
Synthesis and characterization of nanocomposites
Synthesis and characterization of nanocompositesSynthesis and characterization of nanocomposites
Synthesis and characterization of nanocomposites
 
Synthesis and characterization of nanocomposites
Synthesis and characterization of nanocompositesSynthesis and characterization of nanocomposites
Synthesis and characterization of nanocomposites
 
Solvothermal method mithibai college msc part 1 pradeep jaiswal
Solvothermal method mithibai college msc part 1 pradeep jaiswalSolvothermal method mithibai college msc part 1 pradeep jaiswal
Solvothermal method mithibai college msc part 1 pradeep jaiswal
 
Characterization techniques of nanoparticles
Characterization techniques of nanoparticlesCharacterization techniques of nanoparticles
Characterization techniques of nanoparticles
 
Polymer nanocomposites
Polymer nanocompositesPolymer nanocomposites
Polymer nanocomposites
 
Nanomaterials
NanomaterialsNanomaterials
Nanomaterials
 
Nanocatalysis
NanocatalysisNanocatalysis
Nanocatalysis
 
Nano particles synthesis
Nano particles synthesisNano particles synthesis
Nano particles synthesis
 
Synthesis of Nanomaterials
Synthesis of NanomaterialsSynthesis of Nanomaterials
Synthesis of Nanomaterials
 
Synethsis method
Synethsis methodSynethsis method
Synethsis method
 
Nano architecture: self assembly and template methods.
Nano architecture: self assembly and template methods.Nano architecture: self assembly and template methods.
Nano architecture: self assembly and template methods.
 
POLYMER MODIFICATION WITH CARBON NANOTUBES
POLYMER MODIFICATION WITH CARBON NANOTUBESPOLYMER MODIFICATION WITH CARBON NANOTUBES
POLYMER MODIFICATION WITH CARBON NANOTUBES
 
Properties of nano materials
Properties of nano materialsProperties of nano materials
Properties of nano materials
 
carbon nanotubes
 carbon nanotubes   carbon nanotubes
carbon nanotubes
 
Nano technology fabrication methods
Nano  technology fabrication methodsNano  technology fabrication methods
Nano technology fabrication methods
 
Applications of nanomaterials by dr.ck
Applications of nanomaterials by dr.ckApplications of nanomaterials by dr.ck
Applications of nanomaterials by dr.ck
 

Viewers also liked

Nanochemistry
NanochemistryNanochemistry
Nanochemistrytabirsir
 
Synthesis of nanoparticles- physical,chemical and biological
Synthesis of nanoparticles- physical,chemical and biologicalSynthesis of nanoparticles- physical,chemical and biological
Synthesis of nanoparticles- physical,chemical and biologicalPriya Nanda
 
Preparation of Nanoparticles
Preparation of NanoparticlesPreparation of Nanoparticles
Preparation of Nanoparticleshephz
 
Unique Properties At The Nanoscale
Unique Properties At The NanoscaleUnique Properties At The Nanoscale
Unique Properties At The NanoscaleLionel Wolberger
 
Properties of Nano-materials
Properties of Nano-materialsProperties of Nano-materials
Properties of Nano-materialsPartha P. Mishra
 
Gold nanoparticles applications and challenges
Gold nanoparticles  applications and challengesGold nanoparticles  applications and challenges
Gold nanoparticles applications and challengesMathew Thomas Maliael
 
Core shell nanostructures
Core shell nanostructuresCore shell nanostructures
Core shell nanostructuresshashank chetty
 
Nikhil nanoparticles and liposomes
Nikhil nanoparticles and liposomesNikhil nanoparticles and liposomes
Nikhil nanoparticles and liposomesNikhil Patil
 
Properties of nano materials
Properties of nano materialsProperties of nano materials
Properties of nano materialsPoojith Chowdhary
 
Gold nano particles
Gold nano particlesGold nano particles
Gold nano particlesshreni bandi
 
Synthesis of Nano Materials
Synthesis of Nano MaterialsSynthesis of Nano Materials
Synthesis of Nano MaterialsJp Reddy
 
Optical properties of nanomaterials
Optical properties of nanomaterialsOptical properties of nanomaterials
Optical properties of nanomaterialsudhay roopavath
 
final group meeting powerpoint 8-5
final group meeting powerpoint 8-5final group meeting powerpoint 8-5
final group meeting powerpoint 8-5Karen Richards
 
Book nanochemistry a_chemical_approach_to_nanomaterials
Book nanochemistry a_chemical_approach_to_nanomaterialsBook nanochemistry a_chemical_approach_to_nanomaterials
Book nanochemistry a_chemical_approach_to_nanomaterialsnileshbarange
 
1 nanomaterial-synthesis-methods (1)
1 nanomaterial-synthesis-methods (1)1 nanomaterial-synthesis-methods (1)
1 nanomaterial-synthesis-methods (1)Popy Merliana
 
Synthesis and charaterization of la1 x srxmno3 perovskite nanoparticles
Synthesis and charaterization of  la1 x srxmno3 perovskite nanoparticlesSynthesis and charaterization of  la1 x srxmno3 perovskite nanoparticles
Synthesis and charaterization of la1 x srxmno3 perovskite nanoparticlesMai Trần
 

Viewers also liked (20)

Nanochemistry
NanochemistryNanochemistry
Nanochemistry
 
Nanochemistry
NanochemistryNanochemistry
Nanochemistry
 
Synthesis of nanoparticles- physical,chemical and biological
Synthesis of nanoparticles- physical,chemical and biologicalSynthesis of nanoparticles- physical,chemical and biological
Synthesis of nanoparticles- physical,chemical and biological
 
Preparation of Nanoparticles
Preparation of NanoparticlesPreparation of Nanoparticles
Preparation of Nanoparticles
 
Unique Properties At The Nanoscale
Unique Properties At The NanoscaleUnique Properties At The Nanoscale
Unique Properties At The Nanoscale
 
Properties of Nano-materials
Properties of Nano-materialsProperties of Nano-materials
Properties of Nano-materials
 
Presentation On Nanoparticles
Presentation On NanoparticlesPresentation On Nanoparticles
Presentation On Nanoparticles
 
Gold nanoparticles applications and challenges
Gold nanoparticles  applications and challengesGold nanoparticles  applications and challenges
Gold nanoparticles applications and challenges
 
Core shell nanostructures
Core shell nanostructuresCore shell nanostructures
Core shell nanostructures
 
Nikhil nanoparticles and liposomes
Nikhil nanoparticles and liposomesNikhil nanoparticles and liposomes
Nikhil nanoparticles and liposomes
 
Properties of nano materials
Properties of nano materialsProperties of nano materials
Properties of nano materials
 
Gold nano particles
Gold nano particlesGold nano particles
Gold nano particles
 
Synthesis of Nano Materials
Synthesis of Nano MaterialsSynthesis of Nano Materials
Synthesis of Nano Materials
 
Optical properties of nanomaterials
Optical properties of nanomaterialsOptical properties of nanomaterials
Optical properties of nanomaterials
 
final group meeting powerpoint 8-5
final group meeting powerpoint 8-5final group meeting powerpoint 8-5
final group meeting powerpoint 8-5
 
Book nanochemistry a_chemical_approach_to_nanomaterials
Book nanochemistry a_chemical_approach_to_nanomaterialsBook nanochemistry a_chemical_approach_to_nanomaterials
Book nanochemistry a_chemical_approach_to_nanomaterials
 
Nanophysics lec (1)
Nanophysics  lec (1)Nanophysics  lec (1)
Nanophysics lec (1)
 
Nano kolkata
Nano kolkataNano kolkata
Nano kolkata
 
1 nanomaterial-synthesis-methods (1)
1 nanomaterial-synthesis-methods (1)1 nanomaterial-synthesis-methods (1)
1 nanomaterial-synthesis-methods (1)
 
Synthesis and charaterization of la1 x srxmno3 perovskite nanoparticles
Synthesis and charaterization of  la1 x srxmno3 perovskite nanoparticlesSynthesis and charaterization of  la1 x srxmno3 perovskite nanoparticles
Synthesis and charaterization of la1 x srxmno3 perovskite nanoparticles
 

Similar to CHEMISTRY OF NANOSCALE MATERIALS

Introduction nanoscience
Introduction nanoscienceIntroduction nanoscience
Introduction nanosciencePraveen Vaidya
 
NT0209 UNIT IV_SupportingPPT-2.pdf
NT0209 UNIT IV_SupportingPPT-2.pdfNT0209 UNIT IV_SupportingPPT-2.pdf
NT0209 UNIT IV_SupportingPPT-2.pdfJa Veed
 
Introduction to nanoscience and nanotechnology
Introduction to nanoscience and nanotechnologyIntroduction to nanoscience and nanotechnology
Introduction to nanoscience and nanotechnologyaimanmukhtar1
 
sizedependentproperties.pptx
sizedependentproperties.pptxsizedependentproperties.pptx
sizedependentproperties.pptxAditya Bhardwaj
 
Gamma ray spectrum by using na i(tl)detector ..
Gamma ray spectrum by using na i(tl)detector ..Gamma ray spectrum by using na i(tl)detector ..
Gamma ray spectrum by using na i(tl)detector ..Hemn Rahman
 
Ion beam for material analysis(IBA)-RBS-CHANNELING
Ion beam for material analysis(IBA)-RBS-CHANNELINGIon beam for material analysis(IBA)-RBS-CHANNELING
Ion beam for material analysis(IBA)-RBS-CHANNELINGKIAN34
 
13_Properties of Nanomaterials.pptx
13_Properties of Nanomaterials.pptx13_Properties of Nanomaterials.pptx
13_Properties of Nanomaterials.pptxRABEYABASORI
 
8 152-2-7-2011 slides
8 152-2-7-2011 slides8 152-2-7-2011 slides
8 152-2-7-2011 slidesJoanne Cox
 
Nano Tech Lecture2 Dr. A. Waheed Anwar
Nano Tech Lecture2 Dr. A. Waheed AnwarNano Tech Lecture2 Dr. A. Waheed Anwar
Nano Tech Lecture2 Dr. A. Waheed AnwarEngr Mansoor Mirza
 
Calculation of Optical Properties of Nano ParticlePHYSICS 5535- .docx
Calculation of Optical Properties of Nano ParticlePHYSICS 5535- .docxCalculation of Optical Properties of Nano ParticlePHYSICS 5535- .docx
Calculation of Optical Properties of Nano ParticlePHYSICS 5535- .docxRAHUL126667
 
Nano science _technology
Nano science _technologyNano science _technology
Nano science _technologyVřáj Pàtêl
 
NanoBiotechnology Lecture-1-3-2023.pdf
NanoBiotechnology Lecture-1-3-2023.pdfNanoBiotechnology Lecture-1-3-2023.pdf
NanoBiotechnology Lecture-1-3-2023.pdfSudeshnaChakraborty38
 
Microprobing with electrons
Microprobing with electronsMicroprobing with electrons
Microprobing with electronsJonathan Price
 
Nano science _technology
Nano science _technologyNano science _technology
Nano science _technologyKaushal Patel
 
quantum dots and forms of nanomaterials.ppt
quantum dots and forms of nanomaterials.pptquantum dots and forms of nanomaterials.ppt
quantum dots and forms of nanomaterials.pptManju923187
 
Nanotechnology In Bio Medical Applications
Nanotechnology In Bio Medical ApplicationsNanotechnology In Bio Medical Applications
Nanotechnology In Bio Medical Applicationslusik
 
Nanosc2nc
Nanosc2ncNanosc2nc
Nanosc2ncgana9
 

Similar to CHEMISTRY OF NANOSCALE MATERIALS (20)

Introduction nanoscience
Introduction nanoscienceIntroduction nanoscience
Introduction nanoscience
 
NT0209 UNIT IV_SupportingPPT-2.pdf
NT0209 UNIT IV_SupportingPPT-2.pdfNT0209 UNIT IV_SupportingPPT-2.pdf
NT0209 UNIT IV_SupportingPPT-2.pdf
 
Introduction to nanoscience and nanotechnology
Introduction to nanoscience and nanotechnologyIntroduction to nanoscience and nanotechnology
Introduction to nanoscience and nanotechnology
 
6. Nanomaterials
6. Nanomaterials6. Nanomaterials
6. Nanomaterials
 
sizedependentproperties.pptx
sizedependentproperties.pptxsizedependentproperties.pptx
sizedependentproperties.pptx
 
Gamma ray spectrum by using na i(tl)detector ..
Gamma ray spectrum by using na i(tl)detector ..Gamma ray spectrum by using na i(tl)detector ..
Gamma ray spectrum by using na i(tl)detector ..
 
Ion beam for material analysis(IBA)-RBS-CHANNELING
Ion beam for material analysis(IBA)-RBS-CHANNELINGIon beam for material analysis(IBA)-RBS-CHANNELING
Ion beam for material analysis(IBA)-RBS-CHANNELING
 
13_Properties of Nanomaterials.pptx
13_Properties of Nanomaterials.pptx13_Properties of Nanomaterials.pptx
13_Properties of Nanomaterials.pptx
 
8 152-2-7-2011 slides
8 152-2-7-2011 slides8 152-2-7-2011 slides
8 152-2-7-2011 slides
 
Nano Tech Lecture2 Dr. A. Waheed Anwar
Nano Tech Lecture2 Dr. A. Waheed AnwarNano Tech Lecture2 Dr. A. Waheed Anwar
Nano Tech Lecture2 Dr. A. Waheed Anwar
 
Calculation of Optical Properties of Nano ParticlePHYSICS 5535- .docx
Calculation of Optical Properties of Nano ParticlePHYSICS 5535- .docxCalculation of Optical Properties of Nano ParticlePHYSICS 5535- .docx
Calculation of Optical Properties of Nano ParticlePHYSICS 5535- .docx
 
Size effect of nanomaterials
Size effect of nanomaterials Size effect of nanomaterials
Size effect of nanomaterials
 
Nanotechnology-5.docx
Nanotechnology-5.docxNanotechnology-5.docx
Nanotechnology-5.docx
 
Nano science _technology
Nano science _technologyNano science _technology
Nano science _technology
 
NanoBiotechnology Lecture-1-3-2023.pdf
NanoBiotechnology Lecture-1-3-2023.pdfNanoBiotechnology Lecture-1-3-2023.pdf
NanoBiotechnology Lecture-1-3-2023.pdf
 
Microprobing with electrons
Microprobing with electronsMicroprobing with electrons
Microprobing with electrons
 
Nano science _technology
Nano science _technologyNano science _technology
Nano science _technology
 
quantum dots and forms of nanomaterials.ppt
quantum dots and forms of nanomaterials.pptquantum dots and forms of nanomaterials.ppt
quantum dots and forms of nanomaterials.ppt
 
Nanotechnology In Bio Medical Applications
Nanotechnology In Bio Medical ApplicationsNanotechnology In Bio Medical Applications
Nanotechnology In Bio Medical Applications
 
Nanosc2nc
Nanosc2ncNanosc2nc
Nanosc2nc
 

More from INSTITUTO TECNOLÓGICO DE SONORA

More from INSTITUTO TECNOLÓGICO DE SONORA (20)

22 Materiales Compuestos II
22 Materiales Compuestos II22 Materiales Compuestos II
22 Materiales Compuestos II
 
21 Materiales Compuestos I
21 Materiales Compuestos I21 Materiales Compuestos I
21 Materiales Compuestos I
 
20 Vidrios
20 Vidrios20 Vidrios
20 Vidrios
 
19 Materiales Cerámicos II
19 Materiales Cerámicos II19 Materiales Cerámicos II
19 Materiales Cerámicos II
 
18 Materiales Cerámicos I
18 Materiales Cerámicos I18 Materiales Cerámicos I
18 Materiales Cerámicos I
 
17 Materiales Poliméricos I
17 Materiales Poliméricos I17 Materiales Poliméricos I
17 Materiales Poliméricos I
 
16 Materiales Poliméricos
16 Materiales Poliméricos16 Materiales Poliméricos
16 Materiales Poliméricos
 
15 Aleaciones NO Ferrosas
15 Aleaciones NO Ferrosas15 Aleaciones NO Ferrosas
15 Aleaciones NO Ferrosas
 
14 Hierros Fundidos
14 Hierros Fundidos14 Hierros Fundidos
14 Hierros Fundidos
 
13 Tratamientos Superficiales
13 Tratamientos Superficiales13 Tratamientos Superficiales
13 Tratamientos Superficiales
 
12 Ensayo de Jomminy
12 Ensayo de  Jomminy12 Ensayo de  Jomminy
12 Ensayo de Jomminy
 
11 Tratamientos Térmicos
11 Tratamientos Térmicos11 Tratamientos Térmicos
11 Tratamientos Térmicos
 
10 Clasificación de Aceros
10 Clasificación de Aceros10 Clasificación de Aceros
10 Clasificación de Aceros
 
9 Diagrama fe c
9 Diagrama fe c9 Diagrama fe c
9 Diagrama fe c
 
8 Diagramas de Fases
8 Diagramas de Fases8 Diagramas de Fases
8 Diagramas de Fases
 
7 Endurecimiento por Deformación
7 Endurecimiento por Deformación7 Endurecimiento por Deformación
7 Endurecimiento por Deformación
 
6 Fallas en Materiales
6 Fallas en Materiales6 Fallas en Materiales
6 Fallas en Materiales
 
5 Solidificación
5 Solidificación5 Solidificación
5 Solidificación
 
4 Materiales Metálicos
4 Materiales Metálicos4 Materiales Metálicos
4 Materiales Metálicos
 
3 Estructura Cristalina
3 Estructura Cristalina3 Estructura Cristalina
3 Estructura Cristalina
 

Recently uploaded

CAULIFLOWER BREEDING 1 Parmar pptx
CAULIFLOWER BREEDING 1 Parmar pptxCAULIFLOWER BREEDING 1 Parmar pptx
CAULIFLOWER BREEDING 1 Parmar pptxSaurabhParmar42
 
Education and training program in the hospital APR.pptx
Education and training program in the hospital APR.pptxEducation and training program in the hospital APR.pptx
Education and training program in the hospital APR.pptxraviapr7
 
UKCGE Parental Leave Discussion March 2024
UKCGE Parental Leave Discussion March 2024UKCGE Parental Leave Discussion March 2024
UKCGE Parental Leave Discussion March 2024UKCGE
 
Drug Information Services- DIC and Sources.
Drug Information Services- DIC and Sources.Drug Information Services- DIC and Sources.
Drug Information Services- DIC and Sources.raviapr7
 
Easter in the USA presentation by Chloe.
Easter in the USA presentation by Chloe.Easter in the USA presentation by Chloe.
Easter in the USA presentation by Chloe.EnglishCEIPdeSigeiro
 
M-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptxM-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptxDr. Santhosh Kumar. N
 
3.21.24 The Origins of Black Power.pptx
3.21.24  The Origins of Black Power.pptx3.21.24  The Origins of Black Power.pptx
3.21.24 The Origins of Black Power.pptxmary850239
 
Ultra structure and life cycle of Plasmodium.pptx
Ultra structure and life cycle of Plasmodium.pptxUltra structure and life cycle of Plasmodium.pptx
Ultra structure and life cycle of Plasmodium.pptxDr. Asif Anas
 
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptx
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptxPISA-VET launch_El Iza Mohamedou_19 March 2024.pptx
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptxEduSkills OECD
 
Presentation on the Basics of Writing. Writing a Paragraph
Presentation on the Basics of Writing. Writing a ParagraphPresentation on the Basics of Writing. Writing a Paragraph
Presentation on the Basics of Writing. Writing a ParagraphNetziValdelomar1
 
Prescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptxPrescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptxraviapr7
 
In - Vivo and In - Vitro Correlation.pptx
In - Vivo and In - Vitro Correlation.pptxIn - Vivo and In - Vitro Correlation.pptx
In - Vivo and In - Vitro Correlation.pptxAditiChauhan701637
 
2024.03.23 What do successful readers do - Sandy Millin for PARK.pptx
2024.03.23 What do successful readers do - Sandy Millin for PARK.pptx2024.03.23 What do successful readers do - Sandy Millin for PARK.pptx
2024.03.23 What do successful readers do - Sandy Millin for PARK.pptxSandy Millin
 
CapTechU Doctoral Presentation -March 2024 slides.pptx
CapTechU Doctoral Presentation -March 2024 slides.pptxCapTechU Doctoral Presentation -March 2024 slides.pptx
CapTechU Doctoral Presentation -March 2024 slides.pptxCapitolTechU
 
CHUYÊN ĐỀ DẠY THÊM TIẾNG ANH LỚP 11 - GLOBAL SUCCESS - NĂM HỌC 2023-2024 - HK...
CHUYÊN ĐỀ DẠY THÊM TIẾNG ANH LỚP 11 - GLOBAL SUCCESS - NĂM HỌC 2023-2024 - HK...CHUYÊN ĐỀ DẠY THÊM TIẾNG ANH LỚP 11 - GLOBAL SUCCESS - NĂM HỌC 2023-2024 - HK...
CHUYÊN ĐỀ DẠY THÊM TIẾNG ANH LỚP 11 - GLOBAL SUCCESS - NĂM HỌC 2023-2024 - HK...Nguyen Thanh Tu Collection
 
How to Add a New Field in Existing Kanban View in Odoo 17
How to Add a New Field in Existing Kanban View in Odoo 17How to Add a New Field in Existing Kanban View in Odoo 17
How to Add a New Field in Existing Kanban View in Odoo 17Celine George
 
Human-AI Co-Creation of Worked Examples for Programming Classes
Human-AI Co-Creation of Worked Examples for Programming ClassesHuman-AI Co-Creation of Worked Examples for Programming Classes
Human-AI Co-Creation of Worked Examples for Programming ClassesMohammad Hassany
 
The Stolen Bacillus by Herbert George Wells
The Stolen Bacillus by Herbert George WellsThe Stolen Bacillus by Herbert George Wells
The Stolen Bacillus by Herbert George WellsEugene Lysak
 

Recently uploaded (20)

CAULIFLOWER BREEDING 1 Parmar pptx
CAULIFLOWER BREEDING 1 Parmar pptxCAULIFLOWER BREEDING 1 Parmar pptx
CAULIFLOWER BREEDING 1 Parmar pptx
 
Education and training program in the hospital APR.pptx
Education and training program in the hospital APR.pptxEducation and training program in the hospital APR.pptx
Education and training program in the hospital APR.pptx
 
UKCGE Parental Leave Discussion March 2024
UKCGE Parental Leave Discussion March 2024UKCGE Parental Leave Discussion March 2024
UKCGE Parental Leave Discussion March 2024
 
Drug Information Services- DIC and Sources.
Drug Information Services- DIC and Sources.Drug Information Services- DIC and Sources.
Drug Information Services- DIC and Sources.
 
Easter in the USA presentation by Chloe.
Easter in the USA presentation by Chloe.Easter in the USA presentation by Chloe.
Easter in the USA presentation by Chloe.
 
M-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptxM-2- General Reactions of amino acids.pptx
M-2- General Reactions of amino acids.pptx
 
3.21.24 The Origins of Black Power.pptx
3.21.24  The Origins of Black Power.pptx3.21.24  The Origins of Black Power.pptx
3.21.24 The Origins of Black Power.pptx
 
Ultra structure and life cycle of Plasmodium.pptx
Ultra structure and life cycle of Plasmodium.pptxUltra structure and life cycle of Plasmodium.pptx
Ultra structure and life cycle of Plasmodium.pptx
 
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptx
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptxPISA-VET launch_El Iza Mohamedou_19 March 2024.pptx
PISA-VET launch_El Iza Mohamedou_19 March 2024.pptx
 
Presentation on the Basics of Writing. Writing a Paragraph
Presentation on the Basics of Writing. Writing a ParagraphPresentation on the Basics of Writing. Writing a Paragraph
Presentation on the Basics of Writing. Writing a Paragraph
 
Prescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptxPrescribed medication order and communication skills.pptx
Prescribed medication order and communication skills.pptx
 
In - Vivo and In - Vitro Correlation.pptx
In - Vivo and In - Vitro Correlation.pptxIn - Vivo and In - Vitro Correlation.pptx
In - Vivo and In - Vitro Correlation.pptx
 
2024.03.23 What do successful readers do - Sandy Millin for PARK.pptx
2024.03.23 What do successful readers do - Sandy Millin for PARK.pptx2024.03.23 What do successful readers do - Sandy Millin for PARK.pptx
2024.03.23 What do successful readers do - Sandy Millin for PARK.pptx
 
CapTechU Doctoral Presentation -March 2024 slides.pptx
CapTechU Doctoral Presentation -March 2024 slides.pptxCapTechU Doctoral Presentation -March 2024 slides.pptx
CapTechU Doctoral Presentation -March 2024 slides.pptx
 
CHUYÊN ĐỀ DẠY THÊM TIẾNG ANH LỚP 11 - GLOBAL SUCCESS - NĂM HỌC 2023-2024 - HK...
CHUYÊN ĐỀ DẠY THÊM TIẾNG ANH LỚP 11 - GLOBAL SUCCESS - NĂM HỌC 2023-2024 - HK...CHUYÊN ĐỀ DẠY THÊM TIẾNG ANH LỚP 11 - GLOBAL SUCCESS - NĂM HỌC 2023-2024 - HK...
CHUYÊN ĐỀ DẠY THÊM TIẾNG ANH LỚP 11 - GLOBAL SUCCESS - NĂM HỌC 2023-2024 - HK...
 
Personal Resilience in Project Management 2 - TV Edit 1a.pdf
Personal Resilience in Project Management 2 - TV Edit 1a.pdfPersonal Resilience in Project Management 2 - TV Edit 1a.pdf
Personal Resilience in Project Management 2 - TV Edit 1a.pdf
 
How to Add a New Field in Existing Kanban View in Odoo 17
How to Add a New Field in Existing Kanban View in Odoo 17How to Add a New Field in Existing Kanban View in Odoo 17
How to Add a New Field in Existing Kanban View in Odoo 17
 
Human-AI Co-Creation of Worked Examples for Programming Classes
Human-AI Co-Creation of Worked Examples for Programming ClassesHuman-AI Co-Creation of Worked Examples for Programming Classes
Human-AI Co-Creation of Worked Examples for Programming Classes
 
Finals of Kant get Marx 2.0 : a general politics quiz
Finals of Kant get Marx 2.0 : a general politics quizFinals of Kant get Marx 2.0 : a general politics quiz
Finals of Kant get Marx 2.0 : a general politics quiz
 
The Stolen Bacillus by Herbert George Wells
The Stolen Bacillus by Herbert George WellsThe Stolen Bacillus by Herbert George Wells
The Stolen Bacillus by Herbert George Wells
 

CHEMISTRY OF NANOSCALE MATERIALS

  • 1. Chemistry of Nanoscale Materials Synthesis, Properties and Applications Potential Impacts of Nanoscale Materials Pharmacy Water purification Therapeutic drugs Catalysts Tagging DNA and DNA chips Sensors Information Storage Nanostructured Electrodes Chemical/Optical components Improved polymers Environmental/Green Chemistry Smart magnetic fluids Solar Cells Improved National Security Environmental remediation
  • 2. Definitions Nanoparticle: A solid particle in the 1-1000 nm range that could be noncrystalline, an aggregate of crystallites, or a single crystallite Nanocrystal: A solid particle that is a single crystal in the nanometer size range. Quantum dot. A particle that exhibits properties of quantum confinement. Nanostructured/ Nanophase/ nanoscale material: Any solid material that has a nanometer dimension; Colloid: A stable liquid phase containing particles in the 1-1000 nm range. A colloidal particle is one such 1-1000 nm sized particle Cluster: A collection of units (atoms or reactive molecules) of up to about 50 units. Cluster compounds are such moieties surrounded by a ligand shell that allows isolation of a molecular species (stable, isolable, soluble)
  • 3. Size Relationships of Chemistry, Nanoparticles, and Condensed Matter Physics Nanoscale Condensed Atoms/Molecules Matter Particles 1 125 70,000 6 x 106 ∞ Diameter 1-10 nm Diameter 100-∞ nm Solid State Quantum Chemistry ? Physics In the nanoscale regime, neither quantum chemistry nor classical laws of physics hold
  • 4. Factors Affected by Size Reduction: Bulk vs. Nano Melting Points Optical properties Colors Surface Reactivity Magnetic properties Conductivity Specific heats
  • 5. About 2/3 of the Chemical Elements are Metals
  • 6. Matter has Unusual Properties on the nm Scale If you take gold and make particles about ruby-red 10 nm in diameter, it stained glass looks wine-red or from gold blue-gray, depending nanoparticles on how close the particles are together
  • 7. Preparation of Au Nanoparticles by a Chemical Route Reducing agent Capping agent Au nanoparticles Au3+ Salt
  • 8. Transmission Electron Microscopy Images of Au Nanoparticles
  • 9. Gold Nanospheres with Increasing Diameter Size Bulk Au 4 nm 12 nm 25 nm 37 nm • Optical properties of metal nanoparticles depend on their shape and size • Particle functionalization can be done on the surface • Visible optical changes occur
  • 10. Origin of the Properties Bulk Metal Nanoscale metal Unoccupied Decreasing states the size… occupied states Separation between Close lying bands the valence and conduction bands Unbound electrons have Electron motion becomes motion that is not confined confined, and quantization sets in Particle size < mean free path of electrons
  • 11. Band Structure in Metals EF (Fermi Level) EF depends on the density Density ρ = N/V (where N = Number of electrons, V = volume) Assuming all energy levels have the same number of electrons, δ = EF / N Since N ∝ V Therefore, δ ∝ 1/V V = L3 (where L = side length of the particle) Hence, δ ∝ EF/L3 As the side length of the particle decreases the energy level spacing increase
  • 12. Gold Nanospheres with Increasing Diameter Size Bulk Au 4 nm 12 nm 25 nm 37 nm • Optical properties of metal nanoparticles depend on their shape and size • Particle functionalization can be done on the surface • Visible optical changes occur
  • 13. Surface Plasmon Absorption of Au Nanoparticles Surface plasmon absorption in metal nanoparticles arises from the collective oscillations of the free conduction band electrons that are induced by the incident electromagnetic radiation.
  • 14. Factors that Affect the Surface Plasmon Absorbance of Metal Nanoparticles Plasmon absorption of metal nanoparticles is sensitive to the surrounding environment 1. Dielectric of the surrounding medium 2. Solvents (nature of the solvent)
  • 15. Dielectric Constant and its Effect of the Surface Plasmon Absorption Band Position of the plasmon absorption band can be discussed within the framework of the Drude model λ2 = λp2 (ε∝ = 2εm) Where λp is the bulk plasma wavelength, ε∝ is the high frequency dielectric constants due to interband and core transitions, and εm is the medium dielectric constant The refractive index is directly related to its dielectric constant n = (εm)1/2
  • 16. Normalized surface plasmon absorption band of Au nanoparticles in cyclohexane and o-dichloromethane J. Phys. Chem. B. 2002, 106, 7729 Inset shows the dependence of the square of the observed peak position of the surface plasmon band as a function of twice the medium dielectric function. ( m was determined from the expression, m = n2)
  • 17. How Does SP Band of Alkanethiolate-Au Clusters Vary with Refractive Index The optical dielectric of the ligand shell, and not that of the solvent, dominates the Au cluster dielectric environment Langmuir 1998, 14, 17 Dodecanethiolate-stabilized Au cluster
  • 18. Melting Points Property is a consequence of the averaged coordination number of the participating atoms Typically, for bulk materials, surface atoms form a negligible part of the total number of atoms The smaller a particle becomes, the more the proportion of surface atoms increases Full shell clusters are constructed by successively packing layers – or shells – of metal atoms around a single metal atom The number of atoms per shell is (Sum of atoms + 10n2 + 2) where n = number of shell
  • 19. The Relation Between the total number of atoms in Full shell (‘Magic Number’) clusters and the percentage of surface atoms Full-shell Total Surface Clusters Number of Atoms (%) Atoms 1 Shell 13 92 2 Shells 55 76 3 Shells 147 63 4 Shells 309 52 5 Shells 561 45 7 Shells 1415 35
  • 20. Relation Between the Size of Gold Particles and Their Melting Point 1200 1000 Melting Point (oC) 800 600 400 200 0 0 1 2 3 4 5 6 7 8 9 10 Particle Radius (nm)
  • 21. Other Important Properties of Metal Nanoparticles Gold nanoparticles have been shown to be photoluminescent Unique electrochemical properties Gold nanoparticles have shown electron – acceptor properties Enhanced catalytic properties
  • 22. Semiconductor Nanoparticles Group 14 (old group IV) Si, Ge III-V Materials: GaN, GaP, GaAs, InP, InAs II-VI Materials: ZnO, ZnS, ZnSe, CdS, CdSe, CdTe Quantum dots are semiconductors particles that has all three dimensions confined to the 1-100 nm length scale Colloidal CdSe quantum dots dispersed in hexane
  • 23. Energy Diagrams Illustrating the Situation for a Nanoparticle, in Between a Molecule and a Bulk Semiconductor NANOPARTICLE MOLECULE LUMO BULK SOLID CB Energy ∆E Eg ∆E VB HOMO
  • 24. Quantum Confinement in Semiconductor Nanoparticles Eg (quantum dot) = Eg(bulk) + ( h2/8R2) (1/me + 1/mh) – 1.8e2/4πε 0εR Eg = bandgap energy of a quantum dot or bulk solid R = quantum dot radius mc = effective mass of the electron in the solid mh = effective mass of the hole in the solid ε = dielectric constant of the solid ε0 = permittivity of a vacuum
  • 25. Room-Temperature Spectra of CdSe Quantum Dots (a) Absorption and photoluminescence spectra as a function of diameter (b) Quantum yield of photoluminescence as a function of size. Squares represents deep-trap emission, and circles represent band-edge emission Murray, C. B. Synthesis and characterization of II-VI quantum dots and their assembly into 3D quantum ot superlattices. Ph.D Thesis, MIT, Cambridge , MA 1995
  • 26. Inorganic Semiconductors Trap states are caused by defects, such as vacancies, local lattice mismatches, dangling bonds, or adsorbates at the surface
  • 27. Chemical Synthetic Routes for Metal and Semiconductor Nanoparticles and Structures Additional Synthetic Approaches • Sonochemical • Electrochemical • Photochemical • Chemical Vapor Deposition
  • 28. Aspects of Nanoparticle Growth in Solution Arrested precipitation Precipitation under starving conditions: a large number of nucleation centers are formed by vigorous mixing of the reactant solutions. If concentration growth is kept small, nuclei growth is stopped due to lack of material. Particles had to be protected from Oswald Ripening by stabilizers Oswald Ripening The growth mechanism where small particles dissolve, and are consumed by larger particles. As a result the average nanoparticle size increases with time and the particle concentration decreases. As particles increase in size, solubility decreases.
  • 29. Synthetic Approaches for Metal and Semiconductor Nanoparticles via Chemical Routes 1. Metal Compound • Positively charge metal salt, or • Metal centers of complexes 2. Solvents (depends on the nature of the salt) • Water • Polar organic solvents • Non-polar organic solvents 3. Reducing agent (determined by the nature of the metal compound) • Gaseous hydrogen • Hydridic compounds • Reducing organics, e.g. alcohols Many others
  • 30. Stabilization of Nanoclusters Against Aggregation 1. Electrostatic stabilization Adsorption of ions to the + - - - - - + - - - + -- - + - surface. Creates an electrical - δ+ δ+ δ+ - δ+ δ δ+ -- -- -- double layer which results in a - δ+ δ+ - + δ+ δ+ - + - - --- - -- - - -+ Coulombic repulsion force + - between individual particles 2. Steric Stabilization Surrounding the metal center by layers of material that are sterically bulky, Examples: polymers, surfactants, etc
  • 31. Synthetic Approaches for Metal and Semiconductor Nanoparticles via Chemical Routes 4. Stabilizers Role of stabilizers: Stabilizing agents/ligands/capping agents/passivating agents • prevent uncontrollable growth of particles • prevent particle aggregation • control growth rate • controls particle size • Allows particle solubility in various solvents
  • 32. Other Common Stabilizers 1. Organic ligands • Thiols (thioethanol, thioglycerol, mercaptoethylamine, etc) • Amines • phosphates 2. Surfactants 3. Polymers 4. Solvents ether thioether 5. Polyoxoanions
  • 33. Schematic Procedure for Cluster Synthesis Add electron donor •• •••• •• •••••• + ++ •• ••• •••• • • ++ + •• • • • • •• •• •• ••••• ••• • Metal cations Metal atoms in Cluster in solution solution formation Ligand • •• • •••• • ••••• • • ••• Isolation in molecules (•) •••• •••• • • •• • • • solid form • •••• ••••• •• ••••••••• ••••• •••••• ••• •• •• • • •
  • 34. Schematic Procedure for Cluster Synthesis Add Add Ligand electron molecules (•) donor ++ + + + + •••• •••• •••• •• •• •• •••• • •••• • •••• ++ + • +• • • + • • ••• • ••• •• •• •••• • •••• + ++ • • •• • • + +• •• •• •• ••••••• ••••• •••• ••••••••• •• • • • • • ••••• • • ••• ••••• •• • •• • • • • • • •• •• ••• ••• Metal cations in solution Stabilized Metal particles in solution
  • 35. Synthesis of Metal Nanoparticles in Organic Media Biphasic reduction procedure Add phase transfer reagent Extract e.g. tetraoctyl ammonium Aqueous bromide (TOAB) solution of metal salt Add Reducing agent
  • 36. TEM Image of Au Nanoparticles Prepared in the Presence of a Surfactant (CTAB) CTAB = cetyltrimethylammonium bromide J. Phys. Chem. B. 2001, 105, 4065
  • 37. Nucleation and Growth Homogeneous nucleation occurs via a stepwise sequence of bimolecular additions until a nucleus of critical size is obtained. a. Nucleation from supersaturated solution nS Sn b. Diffusion-Controlled Growth Sn + S Sn+1 LaMer et al. J. Am. Chem. Soc. 1950, 72, 4847 Highly monodisperse nanoparticles are formed if the processes of nucleation and growth can be successfully separated • Nucleation process must be fast • Growth process must be slow
  • 38. Nucleation Nucleus Radius is calculated as follows: ∆G = 4πσ(r2 – [2r3 / 3r*]) Where r = nucleus radius r* = critical nucleus radius σ = surface tension ∆G(nucleus) = n(∆G formation, bulk – ∆G formation, free atom) + σA Where A = particle surface area
  • 39. Dendrimer-Templated Nanocluster Synthesis Structure of poly(amidoamine) dendrimer (PAMAM) Generation 2 PAMAM Dendrimer
  • 40. Dendrimer-Templated Nanocluster Synthesis Pioneered in 1998, by Donald A. Tomalia (Michigan Molecular Institute Richard M. Crooks (TAMU) Hydrazine PAMAM + CuAc2 1 x 10-4 mol 1 x 10-6 mol Cu Nanoclsuters 1 x 10-5 mol Formation of Cu nanoclusters can be monitored by UV-vis spectrophotometry Reaction is pH dependent: Presumably H+ ions compete with Cu2+ ions for the tertiary amine sites J. Am. Chem. Soc. 1998, 120, 4877 J. Am. Chem. Soc 1998, 120, 7355
  • 41. Reverse Micelles Water-in-oil droplets [H2O] Water pool w = [surfactant] Particle size is controlled by the size of the water droplets in which synthesis takes place Consider that: V = volume , R = radius, R = 3V/A A = surface area 3Vaq[H2O] σ = head polar group area Rw = Vaq = volume of water σ[s]
  • 42. Parameters Affecting Particle Growth/ Shape/ Structure • Type of capping agent/stabilizers • Concentration of the reactants • pH value of the solution • Duration of heat treatment
  • 43. Sonochemical Approaches for Nanoscale Particle Synthesis Rectified Diffusion ‘area’ effect ‘shell’ effect + Bubble Acoustic pressure Liquid shell - Bubble
  • 44. Sonochemical Approaches for Nanoscale Particle Synthesis Step 1: • Bubble expands when surrounding medium experiences –ve pressure • Bubble collapses when surrounding medium experiences +ve pressure • Bubble collapse leads to extreme temperatures (5,000 – 50, 000 K), and pressure (100 atm) within the bubble Step 2: Solvent or solute molecules present within the bubbles are decomposed under these extreme conditions and generate highly reactive radicals
  • 45. Formation of Highly Reactive Radicals Depending on the liquid medium, sonication leads to the generation of oxidizing and reducing radicals In aqueous solution H2O • H + •OH M+ + H • M + H+ In solutes like alcohols, sonication leads to secondary radicals RHOH + H (OH• ) • ROH• + H2(H2O) ROH • + M+ M + RO + H+
  • 46. Examples of Metal Nanoparticles Prepared by Sonication Ag nanoparticles prepared in aqueous solution at 1 MHz H2O • • H + OH Ag+ + H • Ag + H+ J. Phys. Chem. 1987, 91, 6687 Au nanoparticles prepared by sonication ROH • AuCl4- Au + Products Langmuir 2002, 18, 7831-7836
  • 47. Synthesis of CdS Nanoparticles General: Anionic or Cd(II) salt + Lewis basic + Sulfide 1-10 nm polymers source CdS Sodium Cd(NO3)2.4H2O + polyphosphate + Na2S CdS 2 x 10-4 M 2 x 10-4 M 2 x 10-4 M Chem. Mater. 1999, 11, 3595
  • 48. Synthesis of CdSe Nanoparticles General: High Phosphine oxide Cd(CH3)2 + Se reagent + temperature surfactant CdSe HAD-TOPO-TOP Cd(CH3)2 + (C8H17)3PSe CdSe HAD-TOP-TOP = hexadecylamine-trioctylphosphine oxide-trioctylphosphine J. Am. Chem. Soc. 1993, 115, 8706
  • 49. Synthesis of ZnSe Nanoparticles Zn(CH3CH2)2 + (C8H17)3PSe Zn/Se TOP Solution Zn/Se TOP + Hexadecylamine 270 C o ZnSe Solution J. Phys. Chem. B. 1998, 102, 3655 TOPO binds too strongly to Zn TOP binds too weakly Amines, however have intermediate strength
  • 50. Synthesis of III-V Semiconductor Nanoparticles Synthesis of III-V semiconductor nanoparticles is quite complex Requires high temperature 370 – 400 oC GaCl3 + tris-(trimethylsilyl)phosphine + TOPO-TOP GaP GaP particles prepared in this manner lacked monodispersity GaCl3 + As(SiMe3)3 ~ 700 oC GaAs Chem. Mater. 1989, 1, 4 J. Am. Chem. Soc. 1990, 112, 9438
  • 51. Synthesis of InP and InCl3 260 oC, TOP InP nanocrystals InCl3 + [(CH3)3Si]3P Synthesis of InAs via Dehalosilylation Me3SiCl Me3SiCl Me3SiCl evolved evolved evolved InCl3 + (Me3Si)3As InAs 3 days, rt 70-75 C o 150 C o 4 days 4 days Chem. Mater. 1989, 1, 4
  • 52. Factors Affecting the Nature of the Nanoparticle • Particle size and shape • Surface properties • Particle-solvent interactions • Particle-particle interactions
  • 53. Common Methods for Nanoparticle Characterization Surface state Particle Surface Surface Surface Size Area composition structure; Topography Surface Complexes Electron Microscopy X-ray diffraction LEED Magnetic Measurements AES, SEM XPS, TEM SIMS, EXAFS EPMA, EXAFS IR, UV-Vis, ESR, NMR, Raman
  • 54. UV-Visible Spectroscopy • Particularly effective in characterizing semiconductor and metal particles • Useful for metal nanoparticle characterization whose surface plasmon absorbance lies in the visible range, e.g. Cu, Au, Ag • Can be used to determine particle size: (For semiconductor nanoparticles: as the radius decreases, the band gap increases and λmax shifts to lower energy. • Particle aggregation • Information about the surface, e.g. presence of adsorbates
  • 55. Infrared Spectroscopy IR has been used as a surface probe for nanostructures Example illustrated by Bardley: Adsorbing CO onto the metal nanoparticle surface resulted in IR depending on particle size More face: More edge: bridged CO linear CO is is stable stable 2.5 nm 4 nm 6 nm As particle size increased, the ratio of terminal CO to bridging CO decreased et al. Chem. Mater. 1992, 4, 1234 Bradley,
  • 56. Nuclear Magnetic Resonance (NMR) Two uses: 1. Probing the ligands that surround metal core 2. Probing the intra-core metallic atoms (difficult) Probing the intra-core metallic atoms Nuclear spin relaxation time, and nuclear resonance frequency, are sensitive to any metallic property the particle may exhibit Change in frequency (known as ‘Knight shift’) is a consequence of the interaction of the metal nucleus with the conduction band electrons If particles are very small, in favorable cases, the Knight shift allows resonances for surface and interior metal particles to be identified
  • 57. Microscopy • TEM: High voltage beam passes through a very thin sample. The sample areas that do not allow passage of electrons allow image to be presented • STM: Involves dragging a sharp needlelike probe across a sample very close to the surface. The tunneling current between the sample and probe tip can be monitored . As probe approaches an elevated portion, the probe moves up and over, and produces a surface map. • AFM: The probe tip is essentially touching the surface, and the surface can be mapped by the weak interaction between the tip and the sample.
  • 58. Transmission Electron Microscopy • Provides direct visual information of size, shape, dispersity, structure and morphology • Routine magnifications > 40,000 to 0.2 nm Drawbacks • Samples are dried and examined under high vacuum conditions • Therefore, no direct information is gained on how particles exist in solution • Only a finite number of particles can be examined and counted, which may not be a representative of the sample as a whole • Requires electron beam in which case, some nanoparticles may undergo structural rearrangement, aggregation or decomposition.
  • 59. Scanning Tunneling Microscopy (STM) Makes possible the determination of the total diameter of the nanoparticle, including the stabilizing ligand shell Effective probe of the electronic properties of nanoparticles Reetz et al. Science 1995, 267, 367-369 A combined STM/TEM study of Pd nanoparticles stabilized by R4N+Br-. Determined thickness of stabilizing ligand shell by subtracting the STM determined diameter from the TEM determined diameter
  • 60. Shortcomings to STM • Nanoparticles may not stick well to the substrate surface, preventing good images from being obtained • Geometry of the tip shape may lead to inaccurate measurements or artifacts in the image • Tunneling mechanism is not well understood • Samples have to be dried • Specific techniques applied to imaging are not mature, i.e. standard literature protocols have not been established
  • 61. Atomic Force Microscopy • Technique is purely mechanical – A cantilevered tip attached to a spring is dragged across a sample – Increase or decrease in tip height is measured yielding a surface height profile as a function of distance – Can be carried out on non-conducting samples Shortcomings • Can reliably determine particle height but not diameter • Cannot distinguish between subtle shape differences, or image particles that are not spatially close to each other
  • 62. High Aspect Ratio Nanoparticles • What is a high aspect ratio nanoparticle? • Aspect ratio refers to the ratio of a particles length to its width Aspect ratio = length width • High aspect ratio nanoparticles have elongated structure Examples: nanotubes, nanowires, nanorods • Often have distinctive properties as opposed to the bulk materials or even spherical particles e.g. Chemical, electrical, magnetic, optical, etc.
  • 63. Types of High Aspect Ratio Nanoparticles Nanowires Aspect ratio Synthetic Method Ni, Au, Pt, Ag, Co, Cu, ZnO Templated electrodeposition Up to 250 TiO2, ZnO, SiO2 Sol-gel 250 Silicon Nanocluster-mediated vapor-liquid- > 100 solid growth > 20 MnO2, Fe2O3, Cu2O, Pd, Electrodeposition on graphite Cu, Au, Ag surface Nanotubes Gold Templated electroless deposition 250 Silica Sol-gel 250 Carbon High temperature: laser > 100 ablation, arc discharge, others Nanorods Gold Surfactant/seed mediated synthesis ~20 CdSe Surfactant/seed mediated synthesis 2-10 Cu Micellar growth 1.7-3.7 Se Crystal growth > 100
  • 64. UV-Visible Absorption Spectrum of Au Nanorods with Aspect Ratio 3.3 J. Phys. Chem. B. 1999, 103, 3073
  • 65. Synthesis of Au Nanorods 1. Formation of 4 nm “seed” by reduction of HAuCl4 HAuCl4 NaBH4 solution + Sodium citrate 2. Seed-mediated growth in the presence of cetyltrimethylammonium bromide (CTAB) produces rod-like Au spheroids and nanorods HAuCl4 Solution + ascorbic acid in CTAB 3. Seed-mediated growth in the presence of cetyltrimethyammonium bromide (CTAB) of rod-like Au nanoparticles leads to Au nanorods HAuCl4 Solution + ascorbic acid in CTAB CTAB = cetyltrimethylammonium bromide (a surfactant)
  • 66. Increase in Intensity of the Longitudinal Plasmon Band with Increase in Nanorod Concentration Chem. Mater. 2003, 15, 1957
  • 67. TEM Image of Au Nanorods Prepared by a Seed-Mediated Growth Method Aspect Ratio = 13 J. Phys. Chem. B. 2001, 105, 4065
  • 68. Gold Nanoparticles with Increasing Aspect Ratio Increasing aspect ratio 1 18 Obare, S. O.; Jana, N. R.; Murphy, C. J. Unpublished results
  • 69. Increase in Aspect Ratio of Au Nanoparticles Shifts the Longitudinal Plasmon Band to the NIR Chem. Mater. 2003, 15, 1957
  • 70. Calculated absorption spectra of Au nanoparticles with Varying Medium Dielectric Constant Link, S.; Mohamed, M. B.; El-Sayed, M. A. J. Phys. Chem. B. 1999, 103 (16), 3073-3077
  • 71. Synthesis of Ag Nanorods and Nanowires Formation of 4 nm “seed” by reduction of AgNO 3 AgNO3 NaBH4 solution + Sodium citrate Ag seed Formation of Ag nanorods; aspect ratio was varied by changing the seed concentration; pH is higher ~ 11.8 AgNO3 solution + ascorbic acid NaOH Formation of Ag nanowires; pH is low AgNO3 + ascorbic acid solution NaOH CTAB = cetyltrimethylammonium bromide (a surfactant)
  • 72. TEM Images of Silver Nanorods and Nanowires Chem. Commun. 2001, 617
  • 73. Silver Nanoparticles with Increasing Aspect Ratio Increasing aspect ratio 1 10 Murphy, C. J.; Jana, N. R. Adv. Mater. 2002, 14, 80
  • 74. Electrochemical Synthesis of Nanoparticles Synthesis of High Aspect Ratio Nanoparticles Nanoporous Membrane Templated Fabrication SEM image of typical alumina membrane. Typically membranes consists of 1. Anodized alumina 2. Track etch polycarbonate www. whatman.com J. Vac. Sci. Technol. B 2003, 35, 1097
  • 75. Nanowire Synthesis by Electrodeposition Sputter Place membrane in copper on aqueous solution of bottom metal salt Nanoporous alumina membrane M+ Apply potential e- - e M+(aq) + e- M(s) Remove copper Dissolve alumina with CuCl/HCl in warm .5 M solution KOH
  • 76. Current–Time Transient for the Deposition of 60 nm Nickel Nanowires into a 6 µm Polycarbonate Template Science 1993, 261, 1316
  • 77. The Sol-Gel Process M-O-R + H2O → MOH + R-OH (Hydrolysis) M-OH + HO-M → M-OH + H2O (Condensation) Sol Gel Metal Hydrolysis Gelling Alkoxide Solution
  • 78. Sol-Gel Synthesis for High Aspect Ratio Fabrication Materials synthesized by sol-gel method: TiO2: Chem. Mater. 1997, 9, 2544, Adv. Mater. 1994, 8, 857. CdS: Adv. Mater. 2001, 13, 1393. SiO2: Chem. Mater. 1997, 9, 2544. J. Am. Chem. Soc. 1995, 117, 2651 In2O3: J. Mater. Chem. 2001, 11, 2901. Ga2O3: J. Mater. Chem. 2001, 11, 2901. V2O5: Chem. Mater. 1997, 9, 2544 MnO2: Chem. Mater. 1997, 9, 2544 WO3: Chem. Mater. 1997, 9, 2544
  • 79. SEM Image of TiO2 Nanostructures Prepared by the Sol-Gel Process SEM image of TiO2 nanostructures obtained by immersing the template membrane in the sol for (A) 5, (B) 25, and (C) 60 s.
  • 80. SEM Image of MnO2 Nanostructures Prepared by the Sol-Gel Process SEM image of MnO2 fibers prepared in the 200-nm-pore-diameter alumina template membrane
  • 81. SEM Image of V2O5 Nanostructures Prepared by the Sol-Gel Process SEM images of the template-synthesized V2O5 microstructures
  • 82. SEM Image of Co3O4 Nanostructures Prepared by the Sol-Gel Process SEM image of Co3O4 fibers prepared in the 200-nm-pore-diameter alumina template membrane
  • 83. Synthesis of Carbon Nanotubes Synthesis of carbon 1993, Nature 1993, 363, 603 Iijima an coworkers first synthesized carbon nanotubes involves high nanotubes via the thermal decomposition of temperature approaches hydrocarbons. High temperature decomposition of vapors such as benzene or acetylene, in the presence of Co, Fe, or Ni catalysts, formed single walled carbon nanotubes. 1996, Science 1996, 273, 483 Laser Ablation method (Smalley and coworkers) Method produced nanotubes formed into ropes of 100-500 carbon nanotubes, at yields of more than 70%. A single walled carbon nanotube 2002, Nano Lett. 2002, 2, 1043 Carbon nanotubes are cylindrical Catalyst-free synthesis (Avouris and coworkers) structures consisting of rolled-up Method developed for carbon nanotube synthesis graphene sheets with fullerene on a silicon surface. Advantage is that catalyst caps. removal is not necessary for purification.
  • 84. Ligands and the Surfaces they are Reported to Functionalize Ligand Name Surface Proposed modified linkage R–S–H Thiols Au, Ag, Cu, Hg, Fe R–S–S–R Disulfides R–C N Isocyanides Pt, Pd Carboxylic acids Metal oxides Phosphonates Metal oxides Siloxanes Metal oxides Hydroxamic acids Metal oxides
  • 85. Selective Functionalization 1-butaneisocyanide 2-mercaptoethylamine Adv. Mater. 1999, 11, 1021
  • 86. Applications of High Aspect Ratio Nanoparticles Several applications of high aspect ratio nanoparticles have been shown, and many others continue to be unfolded Applications is areas such as: •Biology •Gene therapy •Bioseparations •Separations •Catalysis •Sensing •Electronics •Optical applications Etc.
  • 87. Nanowire Synthesis by Electrodeposition Sputter Place membrane in copper on aqueous solution of bottom metal salt Nanoporous alumina membrane M+ Apply potential e- - e M+(aq) + e- M(s) Remove copper Dissolve alumina with CuCl/HCl in warm .5 M solution KOH
  • 88. Au-Ni-Au Nanorods Bound and Unbound to Fluorescein-tagged Poly-His Confocal fluorescence image of Au-Ni-Au after modification of Ni portion with Fluorescein-tagged poly-His SEM image of Au-Ni-Au Nanowires Angew. Chemie. Int. Ed. 2004, 43, 3048
  • 89. Exposure of Fluorescein-tagged Poly-His Proteins to Au-Ni-Au Nanorods Left: Fluorescein-tagged poly-His solution Right: Fluorescein-tagged poly-His Solution after exposure to Au-Ni-Au Nanorods Angew. Chemie. Int. Ed. 2004, 43, 3048
  • 90. Separation of His-tagged Proteins from a Non-His-tagged Structures a. Solution of IgG protein (no a b c His)-Green Alexa dye mixed with His-tagged protein-Red Alexa Dye b. After exposure to Au-Ni- Au; (non-His protein remains in solution) c. Separated Au-Ni-Au from a in solution Angew. Chemie. Int. Ed. 2004, 43, 3048
  • 91. Smart Nanotubes for Bioseparations and Biocatalysis J. Am. Chem. Soc. 2002, 124, 11864
  • 92. Smart Nanotubes for Bioseparations and Biocatalysis Nanotubes preferentially reside in cyclohexane due to Vial containing cyclohexane the outer hydrophobic (upper) and water (lower) surface Add nanotubes A cyclohexane H2 O Nanotubes A. Dansylamide on inner void and C 18 on outer surfaces Danyslamide dye fluoresces green J. Am. Chem. Soc. 2002, 124, 11864
  • 93. Smart Nanotubes for Bioseparations and Biocatalysis Nanotubes preferentially Vial containing cyclohexane reside in Aqueous phase due (upper) and water (lower) to the outer hydrophilic surface Add nanotubes B cyclohexane H2 O Nanotubes B. Quinineurethan on inner and no silane on outer surfaces Quinineurethan dye fluoresces blue J. Am. Chem. Soc. 2002, 124, 11864
  • 94. Smart Nanotubes for Bioseparations and Biocatalysis Nanotubes A preferentially reside in Organic phase while Vial containing cyclohexane nanotubes B reside in the (upper) and water (lower) aqueous phase Add nanotubes A cyclohexane Add nanotubes B H2 O Nanotubes A. Dansylamide on inner void and C 18 on outer surfaces Nanotubes B. Quinineurethan on inner and no silane on outer surfaces J. Am. Chem. Soc. 2002, 124, 11864
  • 95. Multifunctional Nanorods for Gene Delivery Nature Materials 2003, 2, 668 Goal of gene therapy: to introduce foreign cells into somatic cells to supplement defective genes, or provide additional biological functions H2N H2N S-S S-S DNA* HOOC OOC Au Ni HN-DNA* HN-DNA* S-S S-S OOC S-T OOC HS-Transferrin Observations 1. Nanorods were internalized into the cell but did not enter the nucleus 2. GFP was observed in the nucleus indicating delivery of the reporter gene to the nucleus Human kidney cell 3. Au-S-T served to promote cellular uptake 4. Disulfide linkage acts as a cleavable point to promote release of DNA within the cell DNA* = DNA plasmids which encodes Green fluorescent Protein GFP
  • 96. What is Nanoparticle Engineering/Surface Modification Tailored synthesis of core-shell nanoparticles with defined morphologies and properties shell core
  • 97. Why Surface Modification? 1. The shell can alter the charge, functionality, and reactivity of the surface 2. The shell can enhance the stability and dispersibility of the colloidal core 3. Magnetic, optical, or catalytic functions may be readily imparted to the dispersed colloidal core 4. Encasing colloids in a shell of different composition may also protect the core from extraneous chemical and physical changes
  • 98. Effects of Surface Modification Chemical and Colloidal Stability • Nanoparticle degradation through chemical etching • Agglomeration caused by strong van der Waals attractive forces Tuning of Physical Properties For example, the optical properties of metal nanoparticles are influenced by their environments. Controlled surface modification can alter these properties Control of Interparticle Interactions Within Assemblies • Collective properties of nanoparticle assemblies are influenced to a large extent by the separation between the particles. • Coating the particles with a uniform shell of inert material could control the distance between the particles
  • 99. Types of Core-Shell Nanoparticles • Metal-Polymer • Metal-Metal • Semiconductor- Semiconductor • Semiconductor-Metal • Metal - Semiconductor
  • 100. Polymers on Metals • Main reason is for nanoparticle stabilization • Could also be used to assemble nanoparticles • Examples: – Chem. Mater. 1998, 10, 1214 – J. Am. Chem. Soc. 1999, 121, 8518 – Adv. Mater. 1999, 11, 34 – Adv. Mater. 1998, 10, 132 – Chem. Commun. 1998, 351 – Adv. Mater. 1999, 11, 131 – J. Am. Chem. Soc. 1999, 121, 10642 – Nano Lett. 2002, 2, 3
  • 101. Sketch of the surface reactions involved in the formation of a thin silica shell on citrate- stabilized gold particles Langmuir 1996, 12, 4329
  • 102. UV-visible spectra of sodium citrate- stabilized, 15 nm diameter gold colloids 1 day after addition of different amounts of APS APS: polymerization initiator 3-aminopropyltrimethoxysilane Langmuir 1996, 12, 4329
  • 103. 15 nm gold particles coated with thin silica layers 18 hours after addition 42 h after addition 5 days after addition of active silica The silica shell keeps on growing, but eventually small silica particles also nucleate out of the solution. Langmuir 1996, 12, 4329
  • 104. Silica-Coated Au Nanoparticles Langmuir 1996, 12, 4329 Transmission electron micrographs of silica-coated gold particles produced during the extensive growth of the silica shell around 15 nm Au particles with TES in 4:1 ethanol/water mixtures. The shell thickness are (a, top left) 10 nm, (b, top right) 23 nm, (c, bottom left) 58 nm, and (d, bottom right) 83 nm
  • 105. Influence of thin silica shells on the UV- visible spectra of aqueous gold colloids Experimental Calculated Langmuir 1996, 12, 4329
  • 106. Influence of thick silica shells on the UV- visible spectra of ethanolic gold colloids Experimental Calculated Langmuir 1996, 12, 4329
  • 107. Effect of Solvent Refractive Index on the Color of Dispersions of 15 nm Gold Particles with a 60 nm Silica Shell The solvent refractive indices (left to right) are 1.45, 1.42, 1.39, and 1.36 Langmuir 1996, 12, 4329
  • 108. Silica Coating of Silver Colloids NaBH4 AgClO4 + sodium citrate 10 nm Ag nanoparticles Ag + 3-aminopropyltrimethoxysilane + sodium silicate Ag@SiO2 nanoparticles Silicate ion concentration 0.02 % 0.01 % 0.005 % Langmuir 1998, 14, 3740
  • 109. Emulsion Polymerization Emulsion polymerization is a type of polymerization that takes place in an emulsion typically incorporating water, monomer, and surfactant. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer (the oil) are emulsified (with surfactants) in a continuous phase of water. In aqueous solution surfactant Monomer + free radical initiator → Polymer
  • 110. Polymer-Coated Silver Nanoparticles TEM images of silver particles: (A) uncoated particle, (B) polystyrene/methacrylate coated particles, (C) polystyrene/methacrylate coated particles with a covalently bound BSA layer, and (D) the same as panel C after exposure to gold colloids. Negative staining by phosphotungstic acid used for all images J. Am. Chem. Soc. 1999, 121, 10642
  • 111. Preparation of Polymer-Coated Functionalized Silver Nanoparticles Extinction spectra of silver particles: (A) uncoated particles and (B) polystyrene coated particles. Solid line: suspension in water. Dotted line: suspension in water, after 1 h in 1.8 M NaCl J. Am. Chem. Soc. 1999, 121, 10642
  • 112. Synthetic Protocols for the Synthesis of Coupled 1D Nanoparticle Arrays Procedures for (A) Ppy- linked Au Colloids Alkyldithiolate-Linked Au Colloids Ppy = poly(pyrrole) Chem. Mater. 1998, 10, 1214
  • 113. Au Colloids Linked by PPy Transmission electron microscope images of 1D and near- 1D arrays of Au colloids linked by Ppy Chem. Mater. 1998, 10, 1214
  • 114. Semiconductor on Semiconductor Tailoring optical properties Enhancing the luminescence Shell Energy Core core shell shell core
  • 115. Energies of Various Semiconductors TiO2 GaP Energy (eV) GaAs CdS CdSe ZnO TiO2 WO3 1.4 3.0 2.25 1.7 2.5 3.2 3.2 3.2 Values at pH = 1
  • 116. Inorganic Semiconductors Trap states are caused by defects, such as vacancies, local lattice mismatches, dangling bonds, or adsorbates at the surface
  • 117. Examples for Semiconductor- Semiconductor Core-Shell Nanoparticles Examples include: ZnS on CdSe CdS on CdSe CdSe on CdS, etc J. Phys. Chem. B. 1997, 101, 9463 J. Phys. Chem. B. 1998, 102, 1884 J. Phys. Chem. 1993, 97, 5333 J. Phys. Chem. 1996, 100, 6381 J. Phys. Chem. 1996, 100, 8927 J. Phys. Chem. 1996, 100, 13226 J. Phys. Chem. 1996, 100, 20021
  • 118. CdSe Coated with ZnS Nanoparticles Me2Cd + TOPSe CdSe 300 oC (TMS)2/Me2Zn/TOP ∆T ZnS CdSe J. Phys. Chem. 1996, 100, 468 TEM picture of (CdSe)ZnS nanocrystals
  • 119. CdSe Coated with ZnS Nanoparticles J. Phys. Chem. 1996, 100, 468 Absorption spectrum of the (CdSe)TOPO (dotted line) and the (CdSe)ZnS Normalized fluorescence spectra of CdSe-TOPO nanocrystals (solid line). The fluorescence (dotted line) and CdSe@ZnS (solid line) with of the (CdSe)ZnS is also shown (solid line) 470 nm excitation
  • 120. Observations on the Optical Characteristics of CdSe/ZnS Nanoparticles Fluorescence of CdSe-TOPO shows the broad tail, due to surface traps. CdSe/ZnS fluorescence spectrum has a flat baseline; this indicates that the ZnS reduces the traps present on the CdSe (TOPO) surface Fluorescence of CdSe (CdSe/ZnS) was stable for months compared to uncapped CdSe No reduction in the CdSe quantum yield was observed for months with the CdSe/ZnS nanoparticles J. Phys. Chem. 1996, 100, 468
  • 121. Synthesis of HgS/CdS Core-Shell Nanostructures J. Phys. Chem. 1993, 97, 5333 HgScore CdSshell HgCl2 + H2S + sodium polyphosphate → HgS HgS + Cd(ClO4)2 + H2S → HgS/CdS CdScore HgSshell Cd(ClO4)2 + H2S + sodium polyphosphate → CdS CdS + HgCl2 + H2S → CdS/HgS Note: Due to the much lower solubility of HgS compared with CdS particles result in an exchange of Cd2+ by Hg2+ (CdS)n + mHgCl2 → (CdS)n-m(HgS)m + mCdCl2
  • 122. CdS/HgS Mixed Colloids J. Phys. Chem. 1993, 97, 5333 HgS nanoparticles HgS coated with CdS
  • 123. Absorption Spectra of Core-Shell CdS on HgS Nanoparticles J. Phys. Chem. 1993, 97, 5333 A = HgS
  • 124. Fluorescence Spectra of Core-Shell CdS on HgS Nanoparticles HgS nanoparticles do not fluoresce CdS coated HgS nanoparticles fluoresce: Possibly due to removal of traps for nonradiative recombinations or Fluorescence could arise from band to band recombination in HgS core J. Phys. Chem. 1993, 97, 5333
  • 125. CdS/HgS Mixed Colloids J. Phys. Chem. 1993, 97, 5333
  • 126. Metal – Metal Core-Shell Nanostructures Examples reported in the literature Au/Ag : J. Chem. Phys. 1964, 41, 3357-3363 Au/Cd : Ber. Bunsenges. Phys. Chem. 1994, 98, 180-189 Au/Pb : Ber. Bunsenges. Phys. Chem. 1994, 98, 180-189 Au/Sn : J. Phys. Chem. 1994, 98, 6931-6935 Au/Tl : Ber. Bunsenges. Phys. Chem. 1994, 98, 180-189 Ag/Pb : Ber. Bunsenges. Phys. Chem. 1992, 96, 754-759 Ag/Cd : J. Phys. Chem. 1994, 98, 6931-6935 Ag/In : Ber. Bunsenges. Phys. Chem. 1992, 96, 2411-2414 Au/Pt : J. Phys. Chem. B. 2000, 104, 2201-2203
  • 127. Pt/Au Core-Shell Nanoparticles Synthesis of Aucore Ptshell Nanoparticles High T NaAuCl4 + sodium citrate Au nanoparticles (~ 20 nm) H2 PtCl 4 2- + Au nanoparticles Au/Pt Synthesis of Ptcore Aushell Nanoparticles H2 PtCl4 + sodium polyacrylate 2- Pt nanoparticles (~12 nm) γ-rays Pt nanoparticles + K2Au(CN)2 MeOH Pt/Au J. Phys. Chem. B. 2000, 104, 2201-2203
  • 128. PtcoreAushell Nanoparticles Pt nanoparticles 1:1 Pt/Au nanoparticles 1:2 Pt/Au nanoparticles J. Phys. Chem. B. 2000, 104, 2201-2203
  • 129. Pt/Au Core-Shell Nanoparticles J. Phys. Chem. B. 2000, 104, 2201-2203 Absorption spectra of Pt nanoparticles before and after deposition of various amounts of gold. Overall Pt concentration is 1 x 10-4 M Concentration of Pt:Au is given on the Absorption spectra of Au nanoparticles curves before and after deposition of various amounts of Pt. Overall Au concentration: 3 x 10-4 M Molar of Au:Pt is given on the curves
  • 130. AucorePtshell Nanoparticles Electron micrograph of Au core particles before (left) and after (right) deposition of Pt in the ratio 1:2 J. Phys. Chem. B. 2000, 104, 2201-2203
  • 131. Metal-Semiconductor Core-Shell Nanoparticles Metals can be used as templates to make hollow semiconductor nanostructures Fabrication of composite nanoparticles with a large electronic capacitance, i.e. a large difference in the Fermi level of the core relative to the conduction band edge of the shell will enable electrons to diffuse through the shell and be trapped in the core for a long time Examples: Au/CdSe: J. Mater. Res. 1998, 13, 905-908 Au/CdS: J. Phys. Chem. B. 1997, 101, 7675 Ag/TiO2: Langmuir 2000, 16, 2731-2735 Au/TiO2: J. Phys. Chem. B. 2000, 104, 10851 TiO2/Ag: Langmuir 1999, 15, 7084-7087 ZnO/Au: J. Phys. Chem. B. 2003, 107, 7479-7485
  • 132. Au/CdS Composite Nanoparticles Au nanoparticles Au/CdS composite nanoparticles J. Phys. Chem. B. 1997, 101, 7675
  • 133. Synthesis of CdS-Capped Au Nanoparticles High T NaAuCl4 + sodium citrate Au nanoparticles (~ 20 nm) MNA = 2-mercaptonicotinic acid J. Phys. Chem. B. 1997, 101, 7675
  • 134. Absorption Spectra of Au/CdS Nanocomposites Absorption properties of Au/CdS are not the result of a simple addition of the spectra of two nanoclusters, but rather an influence of the CdS on the Au. Au Au/CdS Au/MNA CdS J. Phys. Chem. B. 1997, 101, 7675
  • 135. Emission Spectra of Au/CdS Nanocomposites Emission quenching of CdS is indicative of the occurrence of electron transfer from excited CdS into the Au core. Conduction band energy for CdS = - 1.0 V vs. NHE Fermi level of Au = + 0.5 V vs. J. Phys. Chem. B. 1997, 101, 7675 NHE

Editor's Notes

  1. Aromatic organic compounds make useful chromophores for receptor design, but metal nanoparticles are emerging as importanat colorimetric reporters due to their high extinction coefficients. Gold nanoparticle for examples display plasmon absorption bands that depend on their shape and size, and degree of aggregation. By varying the size of gold nanospheres we can change their color from orange to red. These particles can be used as optical reporters by functionalizing their surface. We have seen in the previous experiment how we have developed Li selective ligands based on Phen, and he ligand form a 2:1 complex with Li.
  2. Aromatic organic compounds make useful chromophores for receptor design, but metal nanoparticles are emerging as importanat colorimetric reporters due to their high extinction coefficients. Gold nanoparticle for examples display plasmon absorption bands that depend on their shape and size, and degree of aggregation. By varying the size of gold nanospheres we can change their color from orange to red. These particles can be used as optical reporters by functionalizing their surface. We have seen in the previous experiment how we have developed Li selective ligands based on Phen, and he ligand form a 2:1 complex with Li.