The document summarizes a research paper on the size-dependent optical properties of zinc-doped chromium oxide (Cr2O3) nanoparticles. It includes an introduction, methods used to prepare and analyze the nanoparticles, results of the analysis showing decreasing band gap and changing refractive index with decreasing particle size, and conclusions about the nanoparticles exhibiting quantum confinement effects and potential applications in solar cells and optoelectronic devices.

1. 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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2.  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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3.  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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4. www.essentialchemicalindustry.org
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5.  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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6.  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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7.  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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8.  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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9.  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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10.  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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11.  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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12. For 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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13. http://www.iitk.ac.in/meesa/SEM/tutorial/SEM_MS
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14.  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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15.  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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16.  Fig. FTIR characteristics peaks of the Zn doped Cr2O3 nanoparticles
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17. Fig. FTIR set-up of central university of Punjab, Bathinda
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18.  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 data5/22/2015 18

19. 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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20.  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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21. Fig. Variation of the particle size with
Band gap of nanoparticles
Fig. Variation of the refractive of the
Nanoparticles with Band gap
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22.  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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