The document summarizes different methods for synthesizing cadmium sulfide (CdS) nanoparticles. It describes an aqueous precipitation method using cadmium nitrate and sodium sulfide precursors that produces yellow CdS precipitate. It also outlines a sol-gel method using cadmium acetate, diaminobenzene, and thioacetamide precursors that generates a CdS sol and gel. Additionally, it mentions a hydrothermal method using cadmium nitrate, thiourea, and hexamethylenetetramine precursors under high temperature and pressure that can control CdS morphology. The document provides an overview of various preparation techniques for CdS nanoparticles.

1. Synthesis of Cadmium Sulfide
nanoparticles
R.Gandhimathi

2. 1nm- One thousandth of a micron (10–9m) (or) a billionth of a meter
Semiconductor nanoparticles
• An important class of nanostructured
materials that have a larger number of
interesting physical, chemical,
mechanical, optical, & electronic,
properties
• Semiconductor nanoparticles(10-
100nm) /semiconductor nanocrystals
(or) quantum dots (2-7nm), which can
emit monochrome & tunable fluorescent
light based on their sizes &
compositions
Compound semiconductor Nanoparticles
Binary compounds- Combination of two elements
Group II-VI, III-V, IV-VI, E.g., GaAs, GAP, CdS
Ternary compounds- Alloy semiconductors
Group III-VxV1-x or IIIxIII1-xV, E.g., Ga0.7Al0.3As,
GaAsxP1-x
Quaternary compounds- Combination of many
binary and ternary compounds
Group III-VxV1-x or IIIxIII1-xV, E.g., Cu2ZnSnS4,
Ag2ZnSnSe4

3. Covers the IR to ultraviolet range could be
the basis for a variety of efficient light–
emitting devices spanning the entire range
of the visible spectrum such as blue–
green lasers
Top of the VB and the bottom of the CB occur at
the same value of electron momentum
Maximum energy of the VB occurs at a
different value of momentum to the
minimum in the CB energy
Direct Indirect Bandgap
Minimum energy difference between the top of the VB and the bottom of the CB
Band gap

4. 4
II–VI semiconductors
ME (M = Cd, Zn, Hg; E = S, Se, Te)
Comprising elements of Groups II and VI of the Periodic Table
Bonding in II–VI compounds is a mixture of covalent and ionic types
Good candidates for optical and optoelectronic devices because of their direct bandgap
• Cadmium selenide (CdSe)
• Cadmium sulfide (CdS)
• Cadmium telluride (CdTe)
• Zinc selenide (ZnSe)
• Zinc sulfide (ZnS)
• Zinc telluride (ZnTe)

5. 5
CdS Nanoparticles Properties
• CdS yellow in color
• II-VI group element
• Direct Bandgap-2.42eV
• Remarkable electrical, optical
and surface properties
• Polymorphs: hexagonal greenlockite
& cubic hawleyite
Applications
▪ solar cells
▪ optical detectors
▪ optoelectronic devices

6. Preparation of CdS Nanoparticles
6
Method chosen:
Aqueous precipitation method
Precursors Used:
Cadmium Nitrate (Cd(NO3)2.4H2O)
Sodium sulfide (Na2S)
Diethylene Glycol DEG
(size of nanoparticles effectively controlled
by adding small amount of protecting agent)
METHODOLOGY
20ml 0.1M(Cd(NO3)2.4H2O
+
10ml DEG
After stirring 3 hrs,
yellow precipitate of
CdS formed, washed
with ethanol and acetone
and dried at room
temperature
3 2( ) 2 ( ) ( ) 3 2( )
( ) 2 ( )
aq aq s aq
Cd NO Na S CdS Na NO
+ → +

7. Precursors
Cadmium acetate hydrate
Diaminobenzene
Thioacetamide
Deionized (DI) water
A sol is a colloidal or molecular suspension of solid
particles of ions in a solvent. Dispersed phase is so
small that gravitational forces do not exist;
only van der Waals forces and surface charges are
present
A gel is a semirigid mass that forms when the solvent
from the sol begins to evaporate, and the particles or
ions left behind begin to join in a continuous network
After a drying process, the liquid phase is removed
from the gel. Then a thermal treatment may be
performed in order to favor further poly condensation
and enhance mechanical properties
• Dissolve Cadmium acetate hydrate and
diaminobenzene in deionized (DI)
water and stirrer 4 h
• Add thioacetamide to the solution and
stirrer for another 4 h
• Centrifuge with 3000 rpm to collect the
precipitate and wash down with
numerous times of DI water and then
dry in a desiccators
METHODOLOGY
Synthesis of CdS nanoparticle by sol-gel method as low temperature NO sensor 2 Rakesh K. Sonker, B.C. Yadav, Vinay Gupta, Monika Tomar, https://doi.org/10.1016/j, Materials Chemistry
and Physics , 2019
Preparation of CdS Nanoparticles Sol-gel method

8. Preparation of CdS Nanoparticles Hydrothermal method
Precursors
▪ Cadmium nitrate tetrahydrate (Cd(NO3)2·4H2O)
▪ Thiourea (CH4N2S)
▪ Capping agent hexamethylenetetramine [(CH2)6N4), HMT]
▪ Deionized water
(Cd(NO3)2·4H2O) : CH4N2S) : [(CH2)6N4), HMT
1:1:0 - dendritic-like CdS (D-CdS),
1:3:1 - branched-like CdS (B-CdS),
1:1:1- petaloid-like CdS (P-CdS)
• The mixture is transferred to a teflon-lined stainless-steel
autoclave, (sealed and kept at 200 ℃ for 12 hours)
• Cooled to room temperature
• Washed several times with ultrapure water and ethanol,
• Vacuum-dried and preserved for further Characterization
Preparation of CdS semiconductor nanomaterials with different morphologies Haiyan Fu1,2, Hui Ou1,2*, Yongping Luo1,2, Zonghu Xiao1,2, Ping Huang1,2 , Lishuigen1,2 and Chen Liu1, 2020 3rd
International Conference on Chemistry and Energy Research IOP Conf. Series: Earth and Environmental Science 639 (2021) 012010 IOP Publishing doi:10.1088/1755-1315/639/1/012010 1
Hydrothermal method is a chemical
reaction in water in a sealed pressure
vessel, which is in fact a type of reaction at
both high temperature and pressure.
METHODOLOGY

9. Thank you
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