Synthesis of CdS Nanoparticles: Surface Morphology and Optical Study
Satish N. Vaishnav1,
Sachin S. Borase2, and Sudam D. Chavhan3*
1Department
of Chemistry, Sardar Vallabhbhai Patel Arts and Science College, Ainpur Tal.
Raver, Dist.-Jalgaon, Maharashtra, Pin-425507, India
2Depaertment
of Chemistry, V. U. Patil Arts and Dr. B. S. Desale Science College, Sakri
424304, India.
3Department
of Physics, V. V. M.’s Sitaram Govind Patil Arts, Science and Commerce College,
Sakir, Dist.-Dhule. Maharashtra, Pin-424304, India
Corresponding Author:
sudam1578@gmail.com
Abstract
In the present study, high-quality cadmium
sulfide (CdS) nanoparticles were synthesized using a simple and low-cost
chemical precipitation method. Particle size control was achieved through the
use of thioglycerol as a capping agent. The optical properties of the
synthesized CdS nanoparticles were investigated using UV–visible spectroscopy,
which revealed strong absorption in the visible region with a noticeable blue
shift of the absorption edge toward shorter wavelengths, confirming the
nanoscale nature of the CdS particles. To explore their applicability in optoelectronic
devices, CdS nanoparticle thin films were fabricated using the spin-coating
technique. The surface morphology of the deposited films was examined using
field-emission scanning electron microscopy (FE-SEM), which confirmed the
formation and uniform distribution of nanoparticles. The results demonstrate
that the chemical precipitation approach provides an effective and scalable
route for producing CdS nanoparticles suitable for low-cost optoelectronic
applications, including solar cells and light-emitting diodes.
Keywords: CdS, nanoparticles, chemical precipitation, FE-SEM, UV-visible
spectroscopy.
1.
Introduction
Chalcogenide
based materials are of vitally important for the sustainable development of
modern society. Their roles in advanced equipment in green energy harvesting,
defense technology, space technology, and biomedical industries are
unparalleled [1-3]. These chalcogenide based II-VI semiconductors are versatile
materials in terms of physical and chemical properties. They possesses an
excellent optoelectronic properties that made them a special among other
materials. Among the chalcogenide compounds, CdS is the simplest one to
synthesis because of its favorable chemical properties. The CdS has the direct
bandgap energy of 2.4 to 2.5 eV. The synthesis of CdS nanoparticles provides an
opportunity to tailor the optical, electronic and surface properties because of
quantum confinement effect [4-6]. The
importance of CdS nanoparticles is to achieve precise bandgap and emission
wavelength through via controlling the growth of particle size. This peculiar
characteristics is applicable to fabricate high-performance optoelectronic
devices, particularly, in quantum dot solar cells, the band alinement with
interface layer has significantly enhanced charge separation and reduced
non-radiative recombination. Nanoparticles of CdS also played a crucial role in
making of high color purity light-emitting diode. Besides, it is also used in
photocatalytic reactions such as organic pollutant degradation and hydrogen gas
evolution.
There
are several ways to synthesize the CdS nanoparticles, particularly,
solvothermal method, hydrothermal method, sol-gel technique, sonochemical
method, combustion, micro-emulsion, wet-chemical synthesis, chemical reduction
synthesis and thermal decomposition techniques etc [4-13]. Among the various preparation strategies,
low-temperature chemical precipitation synthesis methods is particularly
important as it enable cost-effective, scalable, and substrate-compatible formation
of CdS nanoparticles while keeping its intrinsic physical properties. The
chemical precipitation method allow the formation of CdS nanoparticles at
temperatures below 100 °C, offering precise control over particle size,
morphology, and surface states through adjustment of precursor concentration,
pH, and reaction kinetics. Although nanoparticles synthesized at low
temperatures may exhibit high defect densities compared to those prepared under
hydrothermal conditions, controlled synthesis and post-treatment strategies can
effectively tailor surface states to enhance charge separation,
photoluminescence efficiency, and visible-light activity [4]. Moreover,
low-temperature synthesis facilitates integration of CdS nanoparticles onto
flexible substrates and layered device architectures, making it particularly
attractive for next-generation photovoltaic, optoelectronic, and photocatalytic
applications. Beyond optoelectronics, the synthesis of CdS nanoparticles is
crucial for photocatalytic applications, where surface-related phenomena
dominate performance. And for this purpose, surface passivation, dopant
incorporation and heterostructure formation processes are adopted to enhance
photo-stability, catalytic efficiency. Therefore, this method is more robust
and has a great potential to achieve large scale production in order to
incorporate into vast green energy production system.
In
the present study, we have explored the synthesis of CdS nanoparticles by
chemical precipitation method to study the surface morphology and optical
properties of the synthesized materials.
Experimental Details
All the chemicals were of
A. R. grade and purachased from LOBA
Chem Pvt. Ltd. They were used without any further purification. Cadmium
nitrates Cd(NO3)2. 4H2O and thiourea (CH₄N₂S) were used as precursors
for Cd and S ions. Thioglycerol was used to controll the size of CdS
nanoparticles. The cadminium and sulpher precusors were added into round bottom
flask. The thioglycerol was added in an appropriate amount to control the size
of CdS nanoparticles. The pH and reaction temperature were controlled. After the complition of reaction, the
precipitate was collected and washed with ethanol and deionized water several
times to remove residual ions and impurities. Finally, the synthesized
nanoparticles of CdS are dried in air at 100 oC for several hours.
The dried power was used to the study the optical properties of the CdS
synthesized nanoparticles. The synthsized nanoparticles were also used to make
thin films by using the spin-coating method and scanning electron microscopic
study was carried out.
Result and Discussion
Figure 1 shows the optical absorption of
CdS nanoparticles. It
exhibits strong absorption in the ultraviolet and visible regions, which is
characteristic of a direct band-gap of CdS nanoparticles. A pronounced
absorption edge is observed in the visible region, indicating the onset of
band-to-band electronic transitions from the valence band to the conduction
band. For the bulk CdS the absorption edge is near 500-520 nm but for the
current CdS nanoparticles, the absorption edge is blue shifted. This behavior
is attributed to quantum confinement effect, which is observed due to reduced
particles size. The observed absorption tailing below the band edge is
attributed to defects and surface states present in the synthesized
nanoparticles. The absorbance spectrum of CdS confirms the successful formation
of CdS nanoparticles.
Figure 1: UV-Visible
absorption spectrum of synthesized CdS nanoparticles.
Figure 2 shows the surface morphology of
CdS nanopartical thin films prepared via spin-coating technique. The SEM image
shows a densely packed thin film composed of CdS nanoparticles. The
nanoparticles appear well defined with relatively smooth surfaces and exhibit a
narrow size distribution, indicating controlled nucleation and growth during
synthesis. The agglomeration of particles is observed in SEM -image. And it is
attributed to the solvent used to prepare the CdS nanoparticle solution for
spin coating. The clusters of
nanoparticles are found in the SEM image reveals the challenge to prepare
uniform thin film of CdS nanoparticle. This drawback can be solved using an
appropriate solvent to disperse the CdS nanoparticles.
Figure 2: FE-SEM image of CdS
nanoparticles prepared by using spin-coating method.
Conclusions
In
the present study, CdS nanoparticles were successfully synthesized using
chemical precipitation method. The UV-Visible absorbance spectrum showed strong
absorption edge in the visible region. The shift the absorption confirms the
quantum size effect of synthesized CdS nanoparticles. To realize CdS
nanoparticles role in fabrication of opto-electronic devices, we have prepared
the CdS nanoparticles films by using spin-coating method. The field-effect
Scanning electron microscopic image confirms the nanocrystlline growth of CdS.
The synthesized CdS nanoparticle thin films shows the promising features for
its potential use in fabrication of optoelectronic devices particularly solar
cell, and light-emitting diodes.
Acknowledgement
This
paper is dedicated to the Hon. Principal Dr.
R. R. Ahire of Vidya
Vikas Mandal’s Sitaram Govind Patil Arts, Science and Commerce College, Sakri,
on the occasion of his superannuation, in respect of his idealistic headship
and affection toward research. Authors are greatly thankful to the respective
head of the belonging institutes for their constant support and encouragement.
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