Synthesized Cadmium Sulfide Nanoparticles Research Articles

Impact of reaction temperature on the structural, surface morphology and antibacterial activity of hydrothermally synthesized CdS nanoparticles

Cadmium Sulfide (CdS) nanoparticles were synthesized hydrothermally at various reaction temperatures (140, 160, 180,200)°C. Crystal structure and surface morphology were studied corresponding to the reaction temperature. The X,-ray diffraction results, reveals that CdS nanoparticles were prepared have high crystallinity with polycrystalline nature and hexagonal wurtzite phase. The preferential orientation was along (002) and (110) planes. The average crystallite size was tended to increase with the increase of reaction temperature which about (21-24) nm. The structure parameters such as dislocation density and microstrain was examined. CdS nanoparticle images in Field Emission Scanning Electron Microscopy (FESEM) indicates rounded ball (cauliflower), the particle size was in the range of (23-245) nm and the smallest size was obtained for the nanoparticles at reaction temperature 200°C. The antibacterial activity of cadmium sulfide CdS nanoparticles was estimated against two types of common bacteria (Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus). It was found that there is a strong antibacterial activity and the greatest effect was for the prepared nanoparticles at reaction temperatures 160 and 180 oC, and the highest activity was found against (E. coli) bacteria as well as with the increase of nanoparticles concentration. This work combines microbiology and nanotechnology, perform probable advances in the formulation of a new kind of antibacterial.

Acetogenic bacteria utilize light-driven electrons as an energy source for autotrophic growth

Acetogenic bacteria use cellular redox energy to convert CO2 to acetate using the Wood-Ljungdahl (WL) pathway. Such redox energy can be derived from electrons generated from H2 as well as from inorganic materials, such as photoresponsive semiconductors. We have developed a nanoparticle-microbe hybrid system in which chemically synthesized cadmium sulfide nanoparticles (CdS-NPs) are displayed on the cell surface of the industrial acetogen Clostridium autoethanogenum The hybrid system converts CO2 into acetate without the need for additional energy sources, such as H2, and uses only light-induced electrons from CdS-NPs. To elucidate the underlying mechanism by which C. autoethanogenum uses electrons generated from external energy sources to reduce CO2, we performed transcriptional analysis. Our results indicate that genes encoding the metal ion or flavin-binding proteins were highly up-regulated under CdS-driven autotrophic conditions along with the activation of genes associated with the WL pathway and energy conservation system. Furthermore, the addition of these cofactors increased the CO2 fixation rate under light-exposure conditions. Our results demonstrate the potential to improve the efficiency of artificial photosynthesis systems based on acetogenic bacteria integrated with photoresponsive nanoparticles.

Energy transfer from fluorescein dye dispersed with CdS nanoparticles as evidenced by emission spectrum measurements

Cadmium Sulphide (CdS) nanoparticles show very interesting optical properties due to quantum confinement effects, that make them useful for biomedical labelling, optoelectronic devices, etc. In this work we show that when CdS nanoparticles are dispersed in organic dyes, the optical properties of the dyes change considerably. We have synthesized CdS nanoparticles by co-precipitation method and characterized by XRD and TEM. Nanoparticles have been dispersed in aqueous solution of fluorescein dye and their absorption and photoluminescence (PL) spectra were recorded. The intensities of PL spectra and the peak wavelength of emission shifted remarkably from the spectra of corresponding pure dye solution. The observed shifts are attributed to the band structure modification by the formation of chemical complex when dye molecules get adsorbed onto nanoparticle surfaces. FRET mechanism is responsible for the rapid quenching of dye fluorescence.

Defect induced magnetism in green synthesized Cadmium Sulfide nanoparticles for spintronics applications

Introducing room – temperature ferromagnetism, in wide bandgap semiconductors has gained significant interest in the field of diluted magnetic semiconductors. Here, the Cadmium Sulfide and CdS – C. odorata leaf extract composites, fabricated through green synthesis routes, show room – temperature ferromagnetism and improved electrical conductivity. Here, the origin of magnetism is attributed to the trapped electrons in the F – center, which is emanated from the sulfur vacancies. Besides, the composite has ligand – induced magnetism due to the electron transfer at the interface between the CdS and the leaf extract. Enhanced conductivity observed in the composite nanoparticle is due to the loss of a few electrons from the F – center to the conduction band. The leaf extract modified CdS samples exhibit unconventional ferromagnetism which makes them ideal for spintronics applications without any magnetic impurity doping. The improved electrical conductivity exhibited by the samples forecast their multi – utility potential to be exploited for electrical and photovoltaic applications in addition to their DMS and spintronic applications.

Ultrasound assisted dispersive solid phase microextraction of inorganic arsenic from food and water samples using CdS nanoflowers combined with ICP-OES determination

Direct determination of arsenic species in real samples is challenging due to their trace concentration and spectral interferences by coexisting ions. Herein, we proposed an ultrasound-assisted dispersive solid phase microextraction (DSPME) procedure for the analyses of the trace inorganic arsenic. The hydrothermally synthesized cadmium sulfide nanoparticles (CdS NPs) completely adsorbed both arsenic species within 20 s at the initial arsenic concentration of 100 µg L−1. The detection limit (3 S/m) of the proposed method was found to be 0.5 ± 0.2 and 0.8 ± 0.2 ng L−1 for As(III) and As(V), respectively. The accuracy of the method against the systematic and constant errors was confirmed by the analysis of the Standard Reference Material (SRM) (>95% recovery with <5% RSD). The Student’s t-test values were found to be less than the critical Student’s t value at a 95% confidence level. The method was successfully employed for the determination of arsenic in food samples.

Synthesis and Characteristics of CdS Nanoparticles in Normal (1 g) and Simulated Microgravity (SMG)

In the present investigation, the cadmium sulphide (CdS) nanoparticles are synthesized in the normal gravity i.e. 1 g (called as control) and in simulated microgravity (called as SMG). The SMG was created by using an instrument called Random Positioning Machine (RPM). Cadmium sulfide nanoparticles were synthesized by using standard chemical method under normal gravity (1 g) and simulated microgravity conditions. The synthesized CdS nanoparticles were characterized by Ultraviolet Visible spectroscopy, Fourier Transform Infrared Ray spectroscopy (FTIR), X-ray diffraction (XRD). The UV-visible absorption spectrum of CdS nanoparticle solution showed a distinct absorption peak at 472.19 nm in control and 458.26 nm in SMG. The band gap calculated from the absorption edge for microgravity sample was 2.71 eV and for control sample was 2.63 eV. The crystalline size of CdS nanoparticles synthesised in control and Micro-g was determined by XRD. Obtained results showed smaller the particle size in microgravity sample (10.78 nm) as compared to control sample (13.89 nm).

Synthesis of CdS Nanoparticles by Electrochemical Method: Correlation for Photodegradation of Trichloroacetic Acid, Chloroacetic Acid, Acetic Acid and Antibacterial Efficiency

Cadmium sulfide (CdS) nanoparticle has been successfully synthesized by electrochemical method which is simple and inexpensive method. The synthesized CdS nanoparticles were used as a catalyst for the photodegradation of trichloroacetic acid, chloroacetic acid and acetic acid under various experimental conditions by volumetric method. The CdS nanoparticles were characterized by various techniques such as SEM-EDAX, UV-Visible spectroscopy, FTIR-IR spectrum and X-ray diffraction studies. The study of UV-Visible spectroscopy revealed that the CdS nanoparticles showed that the maximum intensity peak at 253.64 nm in the UV-region and the band gap energy is found to be 2.39 nm which was calculated using Tauc-plot. The SEM results showed that the CdS nanoparticles have spherical shape. The EDAX spectra revels the presence of Cd and S in the nanoparticles. From XRD data, the structure of CdS nanoparticles was found to be cubic structure and crystallite size was found to be 16.10 nm. The photocatalytic activity of the synthesized CdS nanoparticles was investigated by the kinetics of photodegradation of carboxylic acids by volumetric method by using NaOH solution. Taft LFER was tested, the isokinetic temperature β was calculated for oxidation of carboxylic acids. The antibacterial activity of CdS nanoparticles was investigated by using gram positive (<i>Bacillus subtilis </i>MTCC 2763) and gram negative (<i>Escherichia coli </i>MTCC 40) bacteria by disc diffusion Kirby-Bauer method in Mueller Hinton Agar Plate by determining the ZOI.<div><br></div>

In-situ preparation of cadmium sulphide nanostructure decorated CNT composite materials for the development of selective benzaldehyde chemical sensor probe to remove the water contaminant by electrochemical method for environmental remediation

Here, it was successfully synthesized cadmium sulphide nanoparticles decorated carbon nanotube film as a nanocomposite materials with an average diameter of ~16.35 nm; CdS-CNT NCs by a facile solution method in basic phase. As-grown CdS-CNT NCs film was characterized in details by FE-SEM, TEM, EDS, XPS, XRD, and FTIR spectroscopy. Glassy carbon electrode (GCE) was modified by CdS-CNT NCs and CdS-CNT NCs/Nafion/GCE assembly was employed to determine lethal Benzaldehyde (BZ) by simple electrochemical approach. Carcinogenic BZ was nominated as a target pollutant by the selectivity investigation, where BZ shows differential pulse voltammetric electrochemical response towards the CdS-CNT NCs/Nafion/GCE electrode probe. It also showed a superb sensitivity as well as ultra-low limit of detection (LOD). In the investigative study, for BZ concentration of 0.1 nM–1.0 mM, the calibration plot was found linear (r2 = 0.9992), where calculated sensitivity and LOD values were obtained as 5.43 μAμM−1cm−2 and 2.2 ± 0.1 pM (S/N = 3) respectively. This report also includes the potential validation of CdS-CNT NCs/Nafion/GCE electrode probe as a selective chemical sensor for BZ. In this approach, CdS-CNT composite was used to fabricate the highly sensitive as well as selective benzaldehyde chemical sensor probe with lowest detection limit by electrochemical technique for the safety of environmental and healthcare fields in broad scale.

Structural, Optical, Electrical and Photocatalytic Degradation Properties of Cadmium Sulfide Nanopaticles by Sol Gel Methodd

Cadmium sulfide (CdS) nanoparticles were synthesized via inexpensive sol gel method at different sintering temperature (350, 400 and 450 °C). The synthesized CdS nanoparticles have been characterized by X-ray diffraction, UV-visible spectroscopy, photoluminescence spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy and Fourier transform infrared spectroscopy. The XRD pattern confirmed the formation of hexagonal Wurtzite structure for all the sintering temperatures. The crystallite size, microstrain and dislocation density have been evaluated using XRD data. SEM and HR-TEM analysis showed morphological transformation with better crystallite and spherical shaped CdS nanoparticles were observed. EDS is also performed to confirm the elemental composition of CdS nanoparticles. FT-IR analysis identified the absorption peaks of the Cd-S extension with moisture content. The UV-visible spectra showed absorption peak in the range of 223-257 nm and optical band gap decrease with increase of sintering temperatures. In addition the synthesized CdS nanoparticles were effectively used to degrade methyl orange dye under sunlight irradiation. The CdS nanoparticles were the potential candidate for optoelectronic applications.

Cytotoxicity assessment of chitosan coated CdS nanoparticles for bio-imaging applications

Nanoparticle-based therapies are found to be effective due to the unique mechanisms-of-action to engineered nanoparticles. These nanoparticles are programmed to be target specific and they can hold drugs along with imaging agents for simultaneous diagnostic and therapeutic purposes. They are making their way into the clinical realm. In this work we propose to develop Cadmium sulphide (CdS) nanoparticles with reduced toxicity that could function as a theranostic nanoparticle for bio- imaging applications. The work focuses on the toxicological investigation of surface modified cadmium sulphide nanoparticles. Uncoated and Chitosan coated CdS nanoparticles were synthesized by wet chemical method. The physico-chemical properties of the nanoparticles were characterized by X-ray diffraction, UV–Vis absorption, Fourier transform infrared, photoluminescence, X-ray photoelectron spectroscopy, dynamic light scattering, zeta potential and transmission electron microscopy. MTT assay was performed for toxicity profiling of the synthesized CdS nanoparticles in Human Jurkat cell and erythrocytes cell lines. The results showed a significant reduction in toxicity when the CdS nanoparticles surface was modified with Chitosan. Flow cytometer studies were performed to assess the incorporation of the synthesized nanoparticles into the cells. Photoluminescence studies showed that the surface modified CdS nanoparticles retained their fluorescence intensity regardless of their surface modification with Chitosan. Chitosan modified surface of the nanoparticles served as an effective barricade against the degradation of cadmium core. Surface modification with Chitosan, reduced the toxicity of cadmium sulphide nanoparticles retaining their fluorescent property in the cells. Thus by intentionally attaching bio-conjugates can be efficiently used for drug delivery to target specific cells as well as enable the imaging for cells.

X-ray peak profile analysis and optical properties of CdS nanoparticles synthesized via the hydrothermal method

Cadmium sulfide (CdS) nanoparticles were prepared by hydrothermal method at 150 °C under different reaction times. It was found that hydrothermal method is an effective, quick, and eco-friendly method to synthesis CdS nanoparticles of hexagonal structure at lower temperature. X-ray peak profile analysis by Williamson–Hall analysis and size–strain plot was employed to estimate the crystallite size and lattice strain of the synthesized CdS nanoparticles and to investigate their effects on the peak broadening. The values of strain, stress and energy density were determined for all XRD peaks of wurtzite hexagonal phase of CdS, by applying various forms of Williamson–Hall procedure, such as UDM (uniform deformation model), USDM (uniform stress deformation model) and UDEDM (uniform deformation energy density model). The obtained results indicate that the crystallite size of CdS nanoparticles estimated from Scherrer equation, Williamson–Hall plots and size–strain plot, are nearly similar and in the range of 14–37 nm. CdS nanoparticles were also investigated using high-resolution transmission electron microscopy (HR-TEM), Fourier transform infra-red spectroscopy (FT-IR), and UV–visible and fluorescence spectroscopy. A dependence of the band gap and the nanoparticle size on the reaction time was reported.

Doping Dependent Structural, Optical, Thermal and Catalysis Properties of Synthesized Cadmium Sulfide Nanoparticles

Doping Dependent Structural, Optical, Thermal and Catalysis Properties of Synthesized Cadmium Sulfide Nanoparticles

Photoluminescence and photocatalytic studies of cadmium sulfide/multiwall carbon nanotube (CdS/MWCNT) nanocomposites

In this study, cadmium sulfide (CdS) nanoparticles were introduced to multiwall carbon nanotubes (MWCNTs) to fabricate CdS/MWCNT nanocomposites in two stages. In the first stage, CdS nanoparticles were synthesized using the hydrothermal method. Then in the next stage, the synthesized CdS nanoparticles were added to MWCNTs by magnetic stirring. The optical properties were determined by using UV–Vis spectroscopy, photocatalytic and photoluminescence analyses. X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) Spectroscopy, Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX) spectroscopy and Transmission Electron Microscopy (TEM) analyses were carried out on the samples in order to accomplish the structural and morphological characterization. The results showed that the optical characteristics of MWCNTs increase by adding CdS nanoparticles to their external walls.

Antimicrobial Activity of Bio and Chemical Synthesized Cadmium Sulfide Nanoparticles

Background: The green synthesis of cadmium sulfide (CdS) nanoparticles has been regarded as the most promising technique for their prospective applications in biological system. Aim of the work: In this study isolation of different bacterial strains from stool samples of healthy volunteer, selection of the most efficient bacterial strains able to reduce cadmium sulfide metal into nanoparticles. Characterization of biosynthesized metal nanoparticles by standard analytical methods. Mediating the biosynthesized cadmium sulfide nanoparticles in medical applications in comparison to those produced by chemical methods. Materials and methods: Extracellular Escherichia coli E-30 and Klebsiella pneumoniae K-6 isolated from stool samples were the strains used for biosynthesis. Cadmium sulfide nanoparticles were also produced by wet chemical method. The characterizations of cadmium sulfide nanoparticles were done by using UV-Visible Spectroscopy, Transmission electron microscopy (TEM), energy dispersive x-ray (EDX) and Fourier transform infrared spectroscopy (FT-IR). Results: Escherichia coli E-30 has shown to be efficient in synthesizing cadmium sulfide nanoparticles where CdS nanoparticles were with average size ranging from 3.2 to 44.9 nm while average size of CdS nanoparticle was synthesized by Klebsiella pneumoniae K-6 ranging from 8.5 to 44.9 nm. While cadmium sulfide nanoparticles synthesized by wet chemical method, ranging from 8.77 to 16.50 nm. Biosynthesized cadmium sulfide nanoparticles by Escherichia coli E-30 showed highest antimicrobial activity on Aspergillus fumigatus, Geotricum candidum, Bacillus subtilis,Staphylococcus aureus and Escherichia coli than chemical synthesized of CdS nanoparticles. Conclusion: Escherichia coli and Klebsiella pneumoniae isolated from stool samples had the ability to produce cadmium sulfide nanoparticles. This kind of microorganisms can be used for synthesis of nanoparticles and heavy metal absorption for detoxification of environment.

Effective chemical route for the synthesis of thiophenol stabilized cadmium sulphide (CdS) quantum dots: compact discussions on the structural, morphological, optical and dielectric properties

This article describes the synthesis of CdS quantum dots by conventional chemical precipitation technique using thiophenol as a stabilizer. Structural information, crystallite size, lattice strain and dislocation density were determined by powder XRD analysis. FTIR analysis confirms the functional groups present in the synthesized CdS nanoparticles. FESEM and TEM analyses were used to investigate the morphology, particle size, phase identification and particle size distribution of the CdS nanoparticles. EDX analysis gives the elemental composition of the title compound. UV–vis-NIR reflectance spectroscopy brings out the nano-regime nature and bandgap of the resultant CdS product. Photoluminescence analysis describes the various emission properties of CdS quantum dots. The emission spectrum was analyzed through Commission International de I’Eclairage (CIE) 1931 chromaticity diagram to explore the dominant emission from the CdS quantum dots. DLS analysis gives out the information regarding secondary particle size of CdS nanoparticles. Dielectric study gives the relation between the dielectric constant and frequency for various temperatures. This work may help to develop a better understanding of solution growth mechanism and stabilizing nature of nanoparticles through chemical synthesis technique. The CdS nanoparticles are useful for the photovoltaic device applications.

Biofabrication of morphology improved cadmium sulfide nanoparticles using Shewanella oneidensis bacterial cells and ionic liquid: For toxicity against brain cancer cell lines

The present work determines the anticancer activity of bio-mediated synthesized cadmium sulfide nanoparticles using the ionic liquid and bacterial cells (Shewanella oneidensis). Bacterial cells have been exposed to be important resources that hold huge potential as ecofriendly, cost-effective, evading toxic of dangerous chemicals and the alternative of conventional physiochemical synthesis. The Shewanella oneidensis is an important kind of metal reducing bacterium, known as its special anaerobic respiratory and sulfate reducing capacity. The crystalline nature, phase purity and surface morphology of biosynthesized cadmium sulfide nanoparticles were analyzed by Fourier transform infrared spectroscopy, X-ray diffraction, Field emission scanning electron microscopy, Energy dispersive spectroscopy and Transmission electron microscopy. The use of imidazolium based ionic liquids as soft templating agent for controlling self-assembly and crystal growth direction of metal sulfide nanoparticles has also advanced as an important method. The microscopic techniques showed that the nanoparticles are designed on the nano form and have an excellent spherical morphology, due to the self-assembled mechanism of ionic liquid assistance. The antitumor efficiency of the cadmium sulfide nanoparticles was investigated against brain cancer cell lines using rat glioma cell lines. The effectively improved nano-crystalline and morphological structure of CdS nanoparticles in the presence of IL exhibit excellent cytotoxicity and dispersion ability on the cell shape is completely spread out showing a nice toxic environment against cancer cells. The cytotoxicity effect of cadmium sulfide nanoparticles was discussed with a diagrammatic representation.

Visible light driven photocatalytic degradation of ofloxacin and malachite green dye using cadmium sulphide nanoparticles

This work demonstrates an effective approach for the degradation of persistent and mutagenic water pollutants under visible light illumination. Cadmium sulphide (CdS) was synthesized using a facile hydrothermal approach and its structural, morphological and optical properties were evaluated by various techniques such as XRD, FTIR, UV-DRS, TGA/DSC, HRTEM and EDX. The XRD spectrum indicated that the synthesized CdS was a crystal mixture of cubic and hexagonal phases. HRTEM images displayed the formation of well crystalline CdS nanoparticles, grown in high density. Further, the synthesized CdS nanoparticles were effectively used as photocatalyst for the degradation of fluoroquinolone antibiotic (ofloxacin) and mutagenic water pollutant (malachite green) under visible light irradiation. Role of hydroxyl radicals (OH) in the photocatalytic process was confirmed by terephthalic acid photoluminescence (TA-PL) technique. Degradation efficiency of about 79.5% and 96% was obtained for ofloxacin and malachite green in the reaction time of 80 and 60min, respectively. It was found that photocatalytic degradation of both compounds i.e. drug and dye followed pseudo first order reaction kinetics.

Synthesis and Characterization of Cadmium Sulfide Nanoparticles by Chemical Precipitation Method.

Cadmium sulfide (CdS) nanoparticles were synthesized by chemical precipitation method using cadmium chloride (CdCl2), sodium sulfide (Na2S) and water as a solvent by varying temperatures from 20-80 degrees C. The nanoparticles were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), High-resolution transmission electron microscopy (HR-TEM) and UV-Visible spectroscopy. XRD pattern revealed cubic crystal structure for all the synthesized CdS nanoparticles. Raman spectra showed first and second order longitudinal optical (LO) phonon vibrational modes of CdS. The size of CdS nanoparticles was found to be in the range of 15-80 nm by FE-SEM analysis, in all cases. The atomic percentage of cadmium and sulfur was confirmed to be 1:1 from EDS analysis. TEM micrograph depicts the spherical shape of the particles and the size is in the range of 15-85 nm while HR-TEM images of CdS nanoparticles exhibit well-resolved lattice fringes of the cubic structure of CdS. The optical properties of CdS were examined by UV-Visible spectroscopy which showed variation in absorption band from 460-480 nm. The band gap was calculated from the absorption edge and found to be in the range of 3.2-3.5 eV which is greater than the bulk CdS.

Synthesis of CdS nanoparticles using different sulfide ion precursors: Formation mechanism and photocatalytic degradation of Acid Blue-29

Cadmium sulphide (CdS) nanoparticles were synthesized by different combinations of chemical precursors using H2S, Na2S and (NH4)2S as sulphide ion sources. The reactions were carried out by a single pot chemical precipitation method under ambient conditions. The X-ray diffraction (XRD) patterns obtained for the synthesized nanoparticles (NPs) were used to determine their crystal structure and the crystallite size. The average particle sizes of the synthesized nanoparticles were determined by transmission electron microscopy, UV–vis spectra and XRD techniques. Electron dispersive spectroscopy and Fourier transform infrared spectroscopy were used to investigate the purity of the synthesized CdS nanoparticles. The smaller particle size for CdS was obtained with Na2S, followed by H2S and (NH4)2S and that the quantization in the band gap was directly in correlation with decreased particle size effects. In addition, mixed phase of wurtzite–zinc blende was synthesized with H2S, while phase pure zinc blende and wurtzite phase was obtained with Na2S and (NH4)2S, respectively. The series of synthesized CdS nanoparticles were exploited for photocatalytic degradation of an organic dye derivative, Acid Blue-29, under visible light and the effect of different precursor combinations on photocatalytic efficiency was analysed. An increase in photocatalytic rate was observed by the decrease in particle size on using different sulfide ion precursors, which can be attributed to the increase in the catalyst surface area, band gap and powerful redox capability. The effect of different sulphide ion sources on the structural and photocatalytic properties was compared and optimized by the above studies.

Preparation, Characterization, and Size Control of Chemically Synthesized CdS Nanoparticles Capped with Poly(ethylene glycol)

We prepared cadmium sulfide (CdS) nanoparticles of a specific size via chemical precipitation at room temperature and characterized them using high-resolution transmission electron microscopy, x-ray powder diffraction, ultraviolet–visible spectroscopy, and Fourier-transform infrared (FTIR) measurements. The results showed that the samples were grown with a cubic phase; the particle size could be changed from 2 nm to 4 nm by varying the molar ratios of the precursors (cadmium chloride and sodium sulfide) in the presence of poly(ethylene glycol) (PEG) as an effective capping agent. The optical bandgap of the synthesized nanoparticles was calculated and ranged from 2.73 eV to 2.92 eV depending on the particle size. A large blue-shift from the bulk bandgap (2.42 eV) was observed owing to the quantum size effect. Surface passivation and adsorption of PEG on the CdS nanoparticles was explained on the basis of FTIR measurements; two bands were observed at 476 cm–1 and 622 cm–1, corresponding to cadmium and sulfide stretching vibrations. We conclude that particle size can be controlled by varying the molar ratios of the precursors. Owing to the PEG encapsulation, the as-prepared samples were extremely stable over time.