synthesis of doped chromium oxide nanoparticles
TRANSCRIPT
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CENTRAL UNIVERSITY OF PUNJAB, BATHINDA
Credit seminar
Size dependent optical properties of Zn doped Cr2O3 nanoparticles
Submitted by:Name: Gaurav Kumar Yogesh
Program: M.Sc. Physics (Nanophysics)Reg. No. CUPB/M.Sc./PMS/SBAS/2013-14/01
Supervisor: Dr. Kamlesh Yadav
Centre for Physical and Mathematical Sciences
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Content Introduction Historic background Method to prepare nanoparticles Properties of nanoparticles Material and methods Experimental analysis Results and discussion Conclusions Review of literature References
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introduction
Technologies ,which incorporate the materials, to
manipulate measures or features with atleast one of its
critical dimensions between 1 nm to 100nm.
Nanomaterials can be of two types; engineered or non-
engineered
Engineered nanoparticles are intentionally created to meet
the specific applications e.g. CNT, Fullerene etc.
Non-engineered nanoparticles are unintentionally created
by nature such as volcanic ash, DNA and protein.
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How big or small are nanoparticles?
www.essentialchemicalindustry.org
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Nanotechnology Through History
Gold colloids were used for
aesthetic (decoration) and
curative purposes
the Lycurgus Cup (4th
Century B.C) is ruby red in
transmitted light and green
in reflected light, due to the
presence of gold colloids
1857: Faraday reported
formation of deep-red
solutions of colloidal Au LS-FCM University di Bologna
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Why small thing ?
Fasters
Lighters
Can get into small spaces
Cheaper
More energy efficient
Less waste product
Use less materials to produce
Different properties
http://snf.stanford.edu/Education/Nanotechnologynt scales
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Methods to achieve the nanoparticles Top-Down approach
These approach use larger (macroscopic) initial structure,
which can be eternally controlled in the process of
nanostructure.
Typical examples are etching through the mask and ball
milling and applications of several plastic deformation. Bottom-Up approach
These approaches include the miniaturization of materials
components (up to atomic level) with further self assembly
process leading to the formation of nanostructure
Typical examples are quantum dot formation during
epitaxial growth and formation of nanoparticles from
colloidal dispersion.
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Why nanoparticles exhibit different properties then bulk ?
Two of the reasons:
1. Ratio of surface area-to-volume of structure
increases most atoms are at or near the surface,
which make them more weakly bonded and
more reactive.
2. Quantum mechanical effects are important, size
of structure is on same scale as the wavelengths
of electrons, and quantum confinement occurs
resulting in changes in electronic and optical
properties
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Examples of Nanotechnology Applications Supercomputer in your palm,
Very tiny motors, pumps, micro sensor, and accelerometers;
Energy storage (batteries) and conversion (solar cells) using nanowires and nanotubes
Stain and wrinkle resistant clothes, transparent zinc oxide sunscreen, fast-absorbing drugs and nutrients.
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objective
To synthesise the nanoparticles by using the novel solvent
and cost effective
To study the doping effect on its optical and structural
properties.
To compare the various results on its process of
synthesising the nanoparticles and doping effects
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Material and methods
All the reagents were of AR/GR quality and were purchased
from the Sigma-Aldrich, Loba- Chemi Pt. Ltd., and were
used without further purification.
Infrared (IR) spectra of nanoparticles were recorded with
KBr on a Bruker FT-IR spectrometer.
Surface morphology and size of the particles has been
recorded with gold coating on the samples
UV-visible spectroscopy was used to record the optical band
of the nanoparticles.
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Experimental analysisFor the characterisation of the samples we do the following
analysis
1. Morphological and structural analysis: FESEM had been used to study the morphological and
structure of prepared samples.
2. Optical analysis: The optical band gap of the material had been calculated
by the (Shimazdu 02206) UV-visible spectrometer
3. Spectroscopical analysis: The various functional groups and the characteristics
peaks due to the various compounds can be observed by (Brucker Ltd) FTIR spectrometer
All the experimental analysis has been performed at the lab of (Centre for Physical and Mathematical sciences) central university of Punjab, Bathinda
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Results and discussion
http://www.iitk.ac.in/meesa/SEM/tutorial/SEM_MS
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Morphlogical and structural analysis FESEM image of the prepared samples of respective particle sizes are 55,
41, 26, 22 nm.
Fig. FESEM image of Zn doped Cr2O3 nanoparticles
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Spectroscopical analysis FTIR stands for Fourier Transform Infrared Spectroscopy. Works on the principle of the Michelson's Interferometer. FTIR spectrometer acquires broadband NIR and FIR spectra. FTIR is method of obtaining the infrared spectra by collecting an inferogram
of a sample signal, using the interferometer and then a Fourier transform on the inferogram to obtain the spectrum
FTIR spectrometer collects and digitised the interferogram, perform the FT function and display the spectrum
Every bond or the functional groups requires the different frequency for absorption, hence characteristic peaks is observed for the every functional groups or the part of the molecules.
According to principle
Applied Infrared frequency = Natural frequency of vibration
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Spectroscopical results
Fig. FTIR characteristics peaks of the Zn doped Cr2O3 nanoparticles
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FTIR set-up
Fig. FTIR set-up of central university of Punjab, Bathinda
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Optical analysis
Optical band gap of the following samples are calculated by Tauc relation, by extrapolating the slope of the peaks gives the optical band of the nanomaterials.
Fig. Optical band of the samples are obtained by the FTIR data
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Samples characterisations and results
Name of the samples
Method of preparation of the samples
Average particles size(nm)
Optical band gap(eV)
Characteristic peaks observed in FTIR (Cr-O Vibration) cm-1
Sample-1 Sol-gel 55 1.50 619
Sample-2 Sol-gel 26 3.50 484
Sample-3 Hydrothermal
22 3.70 760
Sample-4 Sol gel 41 2.09 803
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Size dependent optical properties of the nanoparticles
Decrease in the size of nanoparticles results in the
increase in the optical band gap of the nanomaterials.
It arises due the quantum confinement .
Surface Plasmon resonance: The resonance condition is
established when the frequency of
incident photons matches the natural frequency of surface
electrons oscillating against the restoring force of positive
nuclei. SPR in subwavelength scale nanostructures can be
polaritonic or plasmonic in nature.
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Contd..
Fig. Variation of the particle size withBand gap of nanoparticles
Fig. Variation of the refractive of the Nanoparticles with Band gap
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Conclusions
Size dependent optical properties of nanomaterials.
Refractive index of the nanomaterials is decreases with the
increases in the band gap.
Confirmation of the quantum size effect.
Cr2O3 nanoparticles can be used in creating the highly efficient
solar cells and optoelectronic devices.
Because of large band gap(≈ 3 eV) used in the insulating materials.
The band gap of the nanoparticles can altered by changing the
environmental conditions or the preparing technique.
It can used in manufacturing the Transparent conducting Oxide
(TCO) materials which have both simultaneous property of
conducting and transparent.
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References Abdullah, M., Rajab, F. M., & Al-Abbas, S. M. (2014). Structural and optical
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Thank You