1. UV-VIS AND RAMAN SPECTROSCOPY:
PRINCIPLE AND APPLICATIONS IN
NANOTECHNOLOGY
PRESENTED BY:
MANALI SOMANI (2015TTF2390)
SNEHA NAWAGE (2015TTF2395)
ANUBHAV SHUKLA (2015TTF
PRESENTED TO:
PROF. MANGALA JOSHI

2. ▪ The study of molecular structure and dynamics through the absorption,
emission and scattering of light
What is Spectroscopy?

3. Principle of Spectroscopy
• The principle is based on is the measurement of the spectrum of sample
containing atom/molecule
• Spectrum is a graph of intensity of absorbed or emitted radiation by
sample verses frequency or wavelength
• Spectrophotometer is an instrument design to measure the spectrum of a
compound.

4. RAMAN SPECTROSCOPY

5. Consider the collision between a photon and a molecule
ν0
νs

6. Raman Effect
▪ Scattering can be:
– Elastic- Scattered photon have the same energy and
frequency as the incident photons; it is called as
Rayleigh scattering
– Inelastic- A small fraction of light [approx. 1 in 107] is
scattered at optical frequencies different than the
frequency of incident photons. This process of
scattering is termed the Raman effect
▪ Stokes Raman Scattering: Emitted photon is of
lower frequency than incident photon
▪ Anti-stokes Raman Scattering: Emitted
photon is of higher frequency than incident
photon

7. Interaction between electric field of incident photon and molecule
▪ Light, with incident frequency ‘n0’, has an oscillating electric field (E) :
E = E0 cos (2pn0t)
▪ Induces molecular electric dipole (µ):
µ =  E =  E0 sin (2pn0t)
▪ Proportional to molecular polarizability ()
→Ease with which the electron cloud around a molecule can be distorted
▪ In molecular vibrations, the normal coordinate Q varies periodically with the vibrational frequency ‘nvib’
Q = Qo cos (2pnvibt)
where Qo is the magnitude of the given normal vibration
E

8. ▪ α = αo + (δα/δQ)0 Q = αo + (δα/δQ)0 Qo cos (2pnvibt)
where (αo) is the equilibrium value of (α), and (δα/δQ)0 is the change in
polarizability with external vibration.
▪ Resultant dipole
▪ Raman scattering occurs only when the molecule is ‘polarizable’
change in polarizability,
▪ Routine energy range: 200 - 4000 cm–1
Rayleigh scattering
µ = [α0E0 cos(2πνt)] + ½ (δα/δQ)0 E0[cos(2π(ν- νvib)t) - cos(2π(ν+
νvib)t)]
Raman scattering
Anti-Stokes Raman ScatteringStokes Raman Scattering

9. ▪ Which modes will have a change in polarizability?
asymmetric stretch
Vibrational spectroscopy spectrum rules
symmetric stretch bend

10. • Gross selection rule in IR spectroscopy:
vibration must lead to an oscillating dipole
4000 2000 0
Infrared spectrum of CO2
• Gross selection rule in Raman spectroscopy:
vibration must lead to a change in polarizability
Vibrational spectroscopy spectrum rules

11. 4000 2000 0
 Only the symmetric stretch is observed.
What happened to the other two vibrations?
Vibrational spectroscopy spectrum rules
Raman spectrum of CO2

12. Symmetric stretch
Q

d
dQ> 0


13. Bend
Q

d
dQ
= 0


14. Asymmetric stretch
d
dQ
= 0

Q


15. Types of Raman Spectroscopy
▪ Coherent Anti-Stokes Raman Spectroscopy (CARS)
▪ Resonance Raman (RR) Spectroscopy
▪ Surface-Enhanced Raman Spectroscopy (SERS)
▪ Surface-Enhanced Resonance Raman Spectroscopy (SERRS)

16. Information from Raman Spectroscopy
characteristic
Raman frequencies
changes in
frequency of
Raman peak
polarisation of
Raman peak
width of Raman
peak
intensity of
Raman peak
composition of
material
stress/strain
state
crystal symmetry
and
orientation
quality of
crystal
amount of
material
e.g. Si 10 cm-1 shift per %
strain
e.g. thickness of
transparent coating
e.g. MoS2, MoO3
e.g. orientation of CVD
diamond grains
e.g. amount of plastic
deformation

17. Identification of single atomic layers of
graphene
A. C. Ferrari, et al., Phys. Rev. Lett. (2006), Vol. 97, 187401
Graphite
Graphene

18. Carbon Nanotube
Typical Raman spectra for SWCNT

19. Raman spectra of the CNTs after different
times of nitrogen plasma treatment
Comparison of Raman spectra of SWCNTs, DWCNTs, and MWCNTs

20. Effect of high-pressure on octahedra tilts: LaAlO3
P. Bouvier & J. Kreisel, J. Phys.: Condens. Matter (2002), Vol. 14, pp. 3981
‘Tilted’ perovskites (ABX3)

21. Raman imaging in nano-technology
Contacts on a Si wafer
Do the contacts induce strain ?
Raman (strain) image
Strain underneath & at corner of contacts
Potential effect on dopants …
Change in band position
Strain !

22. UV-VIS SPECTROSCOPY

23. Introduction
23
UV visible spectroscopy is also known as electronic spectroscopy in which, the amount
of light absorbed at each wavelength of UV and visible regions of electromagnetic
spectrum is measured.
This absorption of electromagnetic radiations by the molecules leads to molecular
excitations.

24. Principle of UV-VIS Spectrometry
Ultraviolet light and visible light cause an electronic Transition of electron from one
filled orbital to another of higher Energy unfilled orbital.
These transition occur between the electronic energy levels. As molecule absorbs energy
, an electron is promoted from occupied orbital to an unoccupied orbital of greater
potential energy. Generally the most probable transition is from (HOMO) to (LUMO).

25. Continued…
 Ultraviolet absorption spectra arise from transition of electron within
a molecule from a lower level to a higher level.
 A molecule absorb ultraviolet radiation of frequency (𝜗), the
electron in that molecule undergo transition from lower to higher
energy level.
The energy can be calculated by the equation,
E=h𝜗
25

26. E₁-Eₒ= h𝜗
Etotal=Eelectronic+Evibrational+Erotational
The energies decreases in the following order:
Electronic >Vibrational > Rotational
Continued…

27. Types of Transitions
In U.V spectroscopy molecule undergo electronic transition involving
σ, π and n electrons.
Four types of electronic transition are possible.
 σ ⇾ σ* transition
 n ⇾ σ* transition
 n ⇾ π* transition
 π ⇾ π* transition

28. Transition’s Characteristics
~ 400–700 nm
~ 150-250 nm
~ 200 – 400 nm
~ 115 nm

29. When a sample is exposed to light energy that matches the energy difference between
a electronic transition within the molecule, the light energy would be absorbed by the
molecule and the electrons would be promoted to the higher energy orbital.
A spectrometer records the degree of absorption by a sample at different wavelengths
and the resulting plot of absorbance (A) versus wavelength (λ) is known as a spectrum.
The significant features:
 λmax (wavelength at which there is a maximum absorption)
 Emax (The intensity of maximum absorption)
The Absorption Spectrum

30. Continued…
UV-Vis Spectrum of Silver Nanoparticles
UV-visible spectrum of Silver Nanoparticles showing maximum absorption at 420 nm.
λmax
Emax

31. Lambert’s Law
▪ When a monochromatic radiation is passed through a solution, the decrease in the intensity
of radiation with thickness of the solution is directly proportional to the intensity of the
incident light.
▪ Let I be the intensity of incident radiation.
x be the thickness of the solution.
Then I
dx
dI
 KI
dx
dI

Lambert’s Law
Where, , A is AbsorbanceA
I
I
0
log
(ε is Absorption coefficient)A = ε
ℓ

32. Beer’s Law
• When a monochromatic radiation is passed through a solution, the decrease in the
intensity of radiation with thickness of the solution is directly proportional to the intensity
of the incident light as well as concentration of the solution.
• Let I be the intensity of incident radiation.
x be the thickness of the solution.
C be the concentration of the solution.
Then
IC
dx
dI
.
Beer’s Law
E is Molar extinction coefficient
0I
I
T 
T is transmittance
A = ε C ℓ

33. Applications of UV-Vis spectroscopy
Detection of functional groups
Detection of extent of conjugation
Identification of an unknown compound
Determination of configurations of geometrical isomers
Determination of the purity of a substance

34. Stability of Nanoparticle
The optical properties of silver
nanoparticles change when particle
agglomerate
When nanoparticle aggregate, the
plasmon resonance will be red-
shifted to a longer wavelength
The peak will broaden or a
secondary peak will form at longer
wavelengths

35. Identification of Size & Shape
Magnitude, peak wavelength and
spectral bandwidth of the SPR of
nanoparticles are dependent on
particle size, shape and material
composition
 Different shape have characteristic
peak in spectra like triangular shaped
particles appear red, pentagon appear
green, and blue particles are spherical.

37. Determination of Concentration
With increase in the concentration of
silver nanoparticle the SPR peak show
bathochromic shift ie. shift towards
red.
Concentration of silver nanoparticle
solutions can be calculated using the
Beer-Lambert’s law as it correlates the
optical density with concentration

38. In situ Nanoparticle Assesment
Use in determinate the changes that
occur during the synthesis of the nano
particle in the in situ process
Increase in no. of nano particle show
Hypsochromic shift

39. References
▪ Yoon D., Moon H. and Cheong H. Variations in the Raman Spectrum as a Function of the
Number of Graphene Layers. Journal of the Korean Physical Society (2009), Vol. 55 (3), pp.
1299-1303
▪ Ahmed Jamal G. R., Mominuzzaman S. M. Different Techniques for Chirality Assignment of
Single Wall Carbon Nanotubes. Journal of Nanoscience and Nanoengineering (2015), Vol. 1
(2), pp. 74-83.
▪ Hooijdonk E. V., Bittencourt C., Snyders R.,Colomer J-F. Functionalization of vertically aligned
carbon nanotubes. Beilstein J. Nanotechnol. (2013), Vol. 4, pp. 129–152.
▪ Bouvier P., Kreisel J. Pressure-induced phase transition in LaAlO3. J. Phys.: Condens.
Matter (2002), Vol. 14, pp. 3981–3991
▪ Joshi M, Bhattacharyya A, Wazid A S, Characterization techniques for nanotechnology
application in textile, Indian Journal of Fibre & Textile Research (2008), Vol. 33, pp. 304-317.
▪ Zook J M, Long S E, Cleveland D, Geronimo C A, MacCuspie R I, Measuring silver nanoparticle
dissolution in complex biological and environmental matrices using UV–visible absorbance,
Anal Bioanal Chem, (2011), Vol. 98, 1993-2002.

40. THANK YOU!