In this presentation , we will learn about synthesis, properties and applications of zinc oxide (ZnO) as a nano material.

1. Nano Materials Synthesis, Properties,Applications, etc.Nano Materials Synthesis, Properties,Applications, etc.
Zinc Oxide ( ZnO )Zinc Oxide ( ZnO )
WAQI AHMED NAJAMWAQI AHMED NAJAM
31159991183115999118
Master Of Electronics And InformationMaster Of Electronics And Information
Engineering (MEIE)Engineering (MEIE)
Email:Email: waqinajam@qq.comwaqinajam@qq.com
Tel: 18629489487Tel: 18629489487
Date Of Presentation : November 19Date Of Presentation : November 19thth
20152015

4. Characteristics of crystal lattice:
Each constituent particle is represented by one point in a crystal
lattice. These points are known as lattice point or lattice site.
Lattice points in a crystal lattice are joined together by straight
lines. By joining the lattice points with straight lines the geometry
of the crystal lattice is formed.
Unit Cell – The smallest portion of a crystal lattice is called Unit
Cell. By repeating in different directions unit cell generates the
entire lattice.
There are three types of Centered Unit Cell.
(a) Body Centered Unit Cells: – If one constituent particle lies at
the centre of the body of a unit cell in addition to the particles
lying at the corners, it is called Body-Centered Unit Cell.
(b) Face-Centered Unit Cells: – If one constituent particle lies at
the centre of each face besides the particles lying at the corner,
it is known as Face-Centered Unit Cells.
(c) End-Centered Unit Cell: – If one constituent particle lies at
the centre of any two opposite faces besides the particles lying
at the corners, it is known as End-Centered Unit Cell. It is also
known as base-centered unit cell.
Orthorhombic Cubic Lattice
Cubic Lattice

5. The lattice constants are a = 3.25 Å and c = 5.2 Å;
their ratio c/a ~ 1.60 is close to the ideal value for
hexagonal cell c/a= 1.633. Wurtzite Structure
Wurtzite Structure

6.  In this chemical route, we used the inc Acetate [Zn(CH3CO2)2.2H2O] precursor as
a inc ion source.
 In this typical synthesis process of ZnO nanocrystals, the inc Acetate was
dissolved in NaOH with a molar ratio of 1:85.
 The solution was strongly stirred with reflux at a constant temperature of 80°C for
3 hour.
 Finally, white precipitate was formed within the solution.
 The solution was filtered by a Whatman filter paper of precise porosity.
 The precipitate was washed repeatedly many times by ethanol to eliminate
impurities.
 The washed precipitate was annealed at a temperature of 100°C in an oven for 2
hour and ground into fine powders.
 The fine powders were characterized using XRD, SEM, UV–vis, and
photoluminescence spectroscopy.
 The absorbance spectrum of the annealed powders was obtained in the range of
200 to 900 nm using JASCO UV–VIS-NIR spectrometers (Model-V570, Jasco
Analytical Instruments, Easton, MD, USA).

7. 
The X-ray diffraction studies indicated the
development of hexagonal structure of the chemically
synthesized ZnO nanocrystals.

The different peak orientations were observed
along the (100), (002), (101), (102), and (110)
planes.

The typical hexagonal wurtzite structure of
the synthesized ZnO nano particles is inferred
from the XRD pattern, which is in good
agreement with the intrinsic fundamental
structure of ZnO as reported in the literature.

The crystallite size (D) of the synthesized ZnO
nanocrystals was calculated using the Debye-
Scherrer formula as given below.
D= kλ / β2θcosθ
Where k is a constant taken to be 0.94,λ is the
wavelength of the X-ray used (λ=1.54 Å),β2θis the full
width at half
maxima of the (002) peak of the X-ray diffraction pattern,
and 2θis the Bragg angle around 34.44°. Finally, the
calcu-lated average value of grain size is found to be 25
nm.

8. 
The photoluminescence spectroscopy
is an excellent intensive technique for
the investigation of the exact band edge
transition levels of a material.

A well-defined photoluminescence
spectrum of the synthesized ZnO nano
crystals is depicted in Figure 5.

The ZnO nano crystal PL spectrum
showed a very strong and intense
emission peak at 365 nm, exactly near
the band edge emission, while showing
no trap-related emission.

From the PL study, the optical band
gap of the synthesized ZnO nano
particles was estimated to be 3.5 eV.

A broad green-yellow illumination
peak is observed over 450 to 600 nm
which is attributed to the amount of non
stoichiometry.

Chemical impurities may also cause
a surrounding of structural defects by
distorting the lattice as well as the
surface of a crystal.

9. 
The absorbance spectrum of the
synthesized ZnO nano-crystals is shown
in Figure 3.

From Figure 3, it is evident that the
ZnO nanocrystals showed high
absorbance in the wavelength range of
200 to 270 nm in the absorbance
spectrum.

The absorbance decreases abruptly
near the band edge around 365 nm, after
which it turns to the transmittance region.

Optical band gap of the synthesized
ZnO nanocrystals was critically examined
by the following equation.
αhν=A(hν-Egm)2
where A is the characteristic parameter
(independent of photon energy) for this
transition , h is Plank's constant, and ν is
the frequency of the light. Eg is the band
gap, and m is the parameter which
characterizes the transition process
involved.
(1/μ=1/me+1/mh), where mass of electron(me)
=0.19 and mass of hole(mh)=0.8.

10. In this study, ZnO nano crystalline powders were synthesized successfully with
hexagonal phase through the novel chemical route using inc Acetate as organic
precursors. The optical band gap value of the synthesized ZnO nanocrystals is
found to be 3.50 eV from the absorption spectroscopy, while the
photoluminescence spectrum reveals a strong emission at 365 nm along with a
broad green-yellow emission. In this investigation, a blue shift observed in both of
the absorbance optical studies and PL spectroscopy on the ZnO nano particles
indicates quantum confinement of carriers, which confirms the effective particle size
reduction of the synthesized ZnO powders.