SYNTHESIS OF ZnSe final

PROJECT PRESENTATION ON
“Synthesis Of ZnSe Nanocrystals”
By:
Jitesh Kumar BE/15007/12
Atish Sinha BE/15009/12
Gaurav Raj Anand BE/15067/12
7/11/2016 contact@gauravrajanand.com

Contents
Introduction
Objective
Methodology
Work Done(Step 1)
Characterization Process
Expected Results
Work done (Step 2)
Further Work
References

Introduction
Nanocrystals
• A nanocrystal is a crystalline particle with at least one dimension measuring less than
1000 nanometers (nm), where 1 nm is defined as 1 thousand-millionth of a meter (10-
9 m).
• The size of nanocrystals distinguishes them from larger crystals. For example, silicon
nanocrystals can provide efficient light emission while bulk silicon does not and may be
used for memory components.
• When embedded in solids nanocrystals may exhibit much more complex melting
behaviour than conventional solids and may form the basis of a special class of
solids. They can behave as single-domain systems (a volume within the system having
the same atomic or molecular arrangement throughout) that can help explain the
behaviour of macroscopic samples of a similar material without the complicating
presence of grain boundaries and other defects.
• Semiconductor nanocrystals having dimensions smaller than 10nm are also described
as quantum dots.

Applications of Nanocrystals
Illumination
Flat panel
display
Optical and
Infrared Lasers
Removal of
pollutants and
toxins
Solar Panels
Refining of
Crude Oils
Drug
Manufacture
Protein
Analysis
Biotags for
Gene
Identification

Zinc Selenide
• Zinc selenide (ZnSe) is a light-yellow, solid compound
comprising zinc (Zn) and selenium(Se).
• It is an intrinsic semiconductor with a band gap of
about 2.70 eV at 25 °C (77 °F).
• ZnSe rarely occurs in nature, and is found in the mineral
that was named after Hans Stille called "stilleite“.
• Fig. 1 ZnSe Unit Cell 3D Fig. 2 Zinc Selenide

• Properties of ZnSe
ZnSe can be made in
both hexagonal
(wurtzite) and cubic
(zincblende) crystal
structure.
It is a wide-bandgap
semiconductor of
the II-IV
semiconductor
group (since zinc and
selenium belong to
the 12th and 16th
groups of
the periodic table,
respectively).
The material can be
doped n-
type doping with, for
instance, halogen
elements. P-type
doping is more
difficult, but can be
achieved by
introducing gallium .

• Material of Properties of Zinc Selenide
Optical Properties
Bulk Absorption Coefficient @ 10.6µm <= 0.0005 cm-1
Temperature Change of Refractive Index @
10.6µm
61 x 10-6/°C
Refractive Index Inhomogeneity @ 632.8 nm < 3 x 10-6
Thermal Properties
Thermal Conductivity @ 20° C 0.18 W/cm/°C
Specific Heat 0.356 J/g/°C
Linear Expansion Coefficient @ 20° C 7.57 x 10-6/°C

Mechanical Properties
Young’s Modulus 67.2 GPa (9.75 x 106 psi)
Rupture Modulus 55.1 MPa (8,000 psi)
Knoop Hardness 105-120 kg/mm2
Density 5.27 g/cm3
Poisson’s Ratio 0.28
Fig 3 ZnSe Transmission Charts Thermo-Optic Coefficient @ Various Wavelengths dn/dT
(10-5°C-1)

• Applications of ZnSe
ZnSe is used to form II-
VI light-emitting
diodes and diode lasers. It
emits blue light.
ZnSe doped with chromium
(ZnSe:Cr) has been used as
an infrared laser gain
medium emitting at about
2.4 µm.
In daily life, it can be found
as the entrance optic in the
new range of "in-ear" clinical
thermometers, seen as a
small yellow window
ZnSe activated with tellurium
is a scintillator with emission
peak at 640 nm, suitable for
matching with photodiodes.
It is used in x-ray and gamma
ray detectors.

Objective
Synthesis of Zinc Selenide Nanocrystals
Study of its optical and electrical
properties
Application in Photovoltaic Cells

Methodology
• The methodology used in preparation of ZnSe nanocrystals by us is
called solvo thermal synthesis method.
• In this case, we use water as a solvent, because of which it is called
hydrothermal synthesis.
• Solvothermal synthesis is a method for preparing a variety of materials
such as metals, semiconductors, ceramics, and polymers.
• The process can be used to prepare many geometries including thin
films, bulk powders, single crystals, and nanocrystals.
• In addition, the morphology (sphere (3D), rod (2D), or wire (1D)) of the
crystals formed is controlled by manipulating the solvent
supersaturation, chemical of interest concentration, and kinetic control.
• The method can be used to prepare thermodynamically stable and
metastable states including novel materials that cannot be easily
formed from other synthetic routes.

• Over the last decade, a majority (~80%) of the literature
concerning solvothermal synthesis has focused on
nanocrystals.
• A magnetic stirrer was used for this process, which was
set at different RPMs for a good number of hours for
mixing and drying.
• A microwave was used for further drying.

Work Done (Step 1)
In the typical synthesis of CdSe, highly pure CdCl2 powder (99.9%) and
elemental
Selenium (99.999%) was used without further purification. Ethylene
glycol and Hydrazine hydrate were also used.
In this synthesis process,
CdCl2 (4.0 g) and elemental
selenium (2.0 g) was taken
with deionized water,
ethylene glycol and
hydrazine hydrate in the
volume ratio of 7:3:1
respectively in a 200ml
capacity conical flask.
Then, the solution was
refluxed under vigorous
stirring at 60°C
for 6 hrs. The black
precipitates was collected
and washed with
anhydrous ethanol and
hot distilled water several
times, then dried in
vacuum at 50°C for 5 h.
The sample was carefully
filtered out and put in a
microwave at 300 degree
Celsius for 5 minutes.
7/11/2016 contact@gauravrajanand.comFinally, ZnSe Nanocrystals were obtained.

Expected Results
X-Ray diffraction spectra of ZnSe.

TEM of ZnSe nanocrystals and corresponding particle size distribution.

PL Spectra of ZnSe Nanocrystals

Characterization Process
XRD
UV
Spectroscopy
SEM
FTIR
Spectroscopy

Work Done (Step 2)
Another sample of ZnSe nanocrystals was prepared using
the same method. The ZnSe nonocrystals were again dried.
The process now to be carried out was doping the sample
with Magnesium(0.5g)
Magnesium was then made into a solution by mixing few
millilitres of distilled water to it and then to ZnSe.
Drying was carried on in a similar manner with the help of
microwave.

Future Work
• The sample ZnSE/ Mg doped is to be sent to Cochin
University through courier for characterization.
• The characterization would involve following processes:
a)XRD
b)UV characterization
c)SEM
d)FTIR Spectroscopy
• The results will be expected in around a week.
• The results of the ZnSe nano crystals and ZnSe/Mg doped
nanocrystals will be put for a comparision.
• A detailed report would follow.

References
• L. Pavesi (2000). "Optical gain in silicon nanocrystals". Nature 408: 440.
doi:10.1038/35044012.
• Jump up ^ S. Tiwari (1996). "A silicon nanocrystal based memory". Appl.
Phys. Lett. 68: 1377. doi:10.1063/1.116085.
• Jump up ^ J. Pakarinen (2009). "Partial melting mechanisms of embedded
nanocrystals". Phys. Rev. B 79: 085426. doi:10.1103/physrevb.79.085426.
• Jump up ^ D. V. Talapin (2012). "Nanocrystal solids: A modular approach to
materials design". MRS Bulletin 37: 63. doi:10.1557/mrs.2011.337.
• Cr2+ excitation levels in ZnSe and ZnS, G. Grebe, G. Roussos and H.-J.
Schulz, J. Phys. C: Solid State Phys. vol. 9 pp. 4511-4516 (1976)
doi:10.1088/0022-3719/9/24/020

• Zhang BP, Wang WX, Yasuda T, Segawa Y, Edamatsu K, Itoh T. Appl
Phys Lett
1997;71:3370–2.
• Shavel A, Gaponik N, Eychmüller A. J Phys Chem B
2004;108:5905–8.
• Zeng RS, Rutherford M, Xie RG, Zou BS, Peng XG. Chem Mater
2010;22:2107–13.
• Wang C, Zhang WX, Qian XF, Zhang XM, Xie Y, Qian YT. Mater
Chem Phys
1999;60:99–102.
• Xiong S, Huang SH, Tang AW, Teng F. Mater Lett 2007;61:5091–4.
• Aparna C. Deshpandea, Shashi B. Singha, Majid Kazemian
Abyaneha, Renu Pasrichab, S.K. Kulkarni - Low temperature
synthesis of ZnSe nanoparticles – 2008
• Lin Yang, Lingyun Liu, Dingquan Xiao, Jianguo Zhu - Preparation
and characterization of ZnSe nanocrystals by a microemulsion-
mediated method – 2011

Thank You!!
• Questions, if any are invited.

SYNTHESIS OF ZnSe final

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