Size Of CdS Nanoparticles Research Articles

Synthesis of CdS Nanoparticles via AOT-Water-<i>n-</i>Heptane Microemulsion Technique

The aim of the study was to synthesis the CdS nanoparticles via AOT-water-n-heptane microemulsion technique. Ternary phase diagram was constructed to obtain the concentration range of oil, surfactant and water. Three main phases form on the ternary phase diagram of AOT-water-n-heptane, which were gel, cloudy and clear phases. The clear phase was heptane rich region. Meanwhile, cloudy phase have consisted two phases and the gel phase was due to high concentration of AOT. The result showed that clear phase region shrink when the Cd2+ and S2-solvent was added or replaced the water component of the tertiary system.The existence of CdS nanoparticles with average size of 14.0 nm has been calculated by using UV-Vis Spectrometry meanwhile the TEM image showed that the size of CdS nanoparticles was about 49-89 nm. It also have concluded that the same concentration at solvents Cd2+ and S2- does not effected the size of nanoparticles.

Modification of Carbon Nanotubes with Cadmium Sulfide Quantum Dots to Obtain Electrode Materials for Current Sources

It has been shown by the modification of multiwalled carbon nanotubes with cadmium sulfide quantum dots that nanocomposites based on multiwalled carbon nanotubes with monitored size of deposited cadmium sulfide nanoparticles can be fabricated. It has been shown that carbon nanotubes modified with CdS quantum dots are good catalysts for the oxygen electrodes of low-temperature fuel cells. The size of CdS nanoparticles was monitored by absorption spectra of a colloidal solution. The proposed method can be employed to fabricate nanocomposites from carbon nanotubes and semiconductor catalysts.

Preparation and characterization of a novel system of CdS nanoparticles embedded in borophosphate glass matrix

A novel composite system of CdS nanoparticles embedded in sodium/potassium/calcium-mixed borophosphate glass has been prepared. The composite was characterized by X-ray diffraction, transmission electron microscope, density measurements, UV–vis absorption and Raman spectroscopies. Different sizes of nanoparticles were prepared by changing the annealing conditions such as temperature and time. Density measurements showed that the density of the composite systems increases by doping and also increases with increasing the size of CdS nanoparticles. X-ray measurements revealed that the structure of the prepared CdS nanoparticles is a hexagonal one and the sizes of the nanoparticles are ranging from 32 to 38Å for the samples annealed at low temperature and short time. However, the sample annealed at high temperature and long time, X-ray and Raman measurements showed a formation of CdSO4 layer at the interface between the surface of the nanoparticles and the host glass matrix. Optical measurements in conjunction with TEM and X-ray proved that the band gaps determined from optical absorption of CdS nanoparticles embedded in the glass matrix are larger than the band gap of the same sizes confined with a high potential barrier. Finally, Raman spectroscopy confirmed the formation of CdS nanoparticles by the appearance of transverse and longitudinal optical phonons of CdS.

Rectification effect in poly-p-xylylene-cadmium sulfide graded nanocomposites

The hybrid poly-p-xylylene-cadmium sulfide nanocomposites characterized by gradients of concentrations and sizes of CdS nanoparticles along the lines of an applied electric field have been synthesized using the vapor deposition polymerization in an inhomogeneous electric field. The maximum concentration of cadmium sulfide can exceed 10 vol %, while the average effective sizes of the nanoparticles depend on the concentration and do not exceed 5 nm. The synthesized thin-film nanocomposites exhibit a quantum confinement effect. According to the estimates obtained from the shift of the absorption band edge, the radius of nanoparticles is 2.7 nm near the negative electrode and 3.5 nm near the positive electrode. It has been found that the sample formed in an electric field of 10 kV/cm manifests a rectification effect, which can be associated with the gradient of nanoparticle sizes. The measurements of current-voltage characteristics and photoconductivity have demonstrated that the synthesized samples possess high photoconductivity. The photocurrent in the sample prepared in an electric field of 10 kV/cm can exceed the dark current by two orders of magnitude, and the rectification effect in this case disappears.

Synthesis and characterization of semiconductor nanoparticles by the amphiphilic block copolymers

A series of well-defined amphiphilic PS-b-PMSMA copolymers with controlled molecular weight and block length were successfully synthesized via atom transfer free radical polymerization (ATRP). The CdS nanoparticles were fabricated in the spherical micelles self-assembled from these prepared PS-b-PMSMA copolymers. Then, the CdS/PS-b-PMSMA films were obtained by spin coating the CdS/PS-b-PMSMA solution on silicon wafer. The experimental results showed the addition of Cu(II) could decrease the value of polydispersity index (PDI) for the prepared copolymers. Under the most suitable experiment condition, the PDI of PS-b-PMSMA copolymers could be limited to below 1.30 as the molecular weight of copolymers was less than 30,000. On the other hand, the ratio of block length between PS and PMSMA had a great influence on the micelle size. The larger ratio of PS to PMSMA block length resulted in the larger size of micelles and CdS nanoparticles that caused a red-shift of UV–vis and PL spectra. The red-shift of spectra was explained by the quantum confinement effect associated with the tiny size of the CdS nanoparticles.

Photocatalytic activity of CdS nanoparticles synthesized by a facile composite molten salt method

Single-crystalline CdS nanoparticles were synthesized for the first time by the composite-molten-salt (CMS) method, with advantages of one-step, ambient pressure, low temperature, template-free and low cost. The influence of temperature, growth time and amount of salts on the morphology of CdS nanoparticles was systematically investigated. It shows that a smaller size of CdS nanoparticles can be obtained under lower temperature, less growth time and more composite salts. UV–vis reflection spectrum of the nanoparticles reveals that the nanoparticles have a bandgap of 2.34eV. Photoluminescence spectrum was also carried out to explore its optical property. Photocatalytic degradation of rhodamine B (RhB) and methylene blue (MB) in presence of the CdS nanoparticles was compared with that in presence of the commercial TiO2 nanoparticles under the simulated sunlight.

Synthesis and Characterization of Pure CdS Nanoparticles for Optoelectronic Applications

Pure CdS nanoparticles were synthesized by using a simple aqueous precipitation method at room temperature. The CdS nanoparticles were then subjected to low temperature heat treatment at 200°C for 2 h. The prepared powder was characterized by various analytical techniques such as powder XRD, SEM, TEM, thermal and spectroscopic analyses. XRD study confirmed the high crystalline nature of prepared compounds and the presence of hexagonal and cubic phases of the CdS nanoparticles. The particle size of CdS nanoparticles were calculated by Scherrer's formula and it was found that the particles were in the range of 8 to 10 nm. SEM images confirmed the homogeneous distribution of the nanoparticles. Photoluminescence studies of CdS nanoparticles showed green emission with peak intensity maximum at 535 nm. Raman spectra of the as-prepared and heat treated samples were recorded using Laser-Raman technique. The bandgap of the CdS particles was calculated from the absorption edge of the UV-Vis spectrum and was found to be 2.48 eV. TEM analysis revealed that most of the crystallites were spherullitic in nature and their size was around 10 nm, which agreed well with the XRD result.

CdS nanoparticles deposited on montmorillonite: Preparation, characterization and application for photoreduction of carbon dioxide

CdS nanoparticles were precipitated by the reaction of cadmium acetate with sodium sulphide in the presence of cetyltrimethylammonium (CTA) and deposited on montmorillonite (MMT). The resulting CdS-MMT nanocomposite contained 6wt.% of CdS and 30wt.% of CTA. Band-gap energy of CdS was estimated at 2.63±0.09eV using the Tauc plot. The size of CdS nanoparticles was calculated from the band-gap energy at 5nm and from the micrographs of transmission electron microscopy (TEM) at 5nm. Selected area electron diffraction (SAED) recognized the cubic structure of CdS (Hawleite). The dynamic light scattering (DLS) method confirmed that CdS nanoparticles were anchored on the surface of MMT particles. CTA was found to be intercalated into MMT and adsorbed on its external surface.CdS-MMT was used for the photoreduction of carbon dioxide dissolved in NaOH solutions. The yields of originating gas products can be arranged in the order: H2≫CH4>CO. Amounts of these products were 4–8 folds higher then those obtained with TiO2 Evonic P25. Hydrogen reduced CO2 to CO and CH4.

Performance enhancement of CdS-sensitized TiO 2 mesoporous electrode with two different sizes of CdS nanoparticles

In order to absorb broad spectrum and enhance the absorption in visible region, a novel electrode architecture is designed to co-sensitize TiO 2 mesoporous film with two different sizes of CdS nanoparticles. Firstly, an added layer of CdS film with large size CdS nanoparticles (L-CdS) is coated on the TiO 2 mesoporous film using spin-coating technique. Then the small size CdS nanoparticles (S-CdS) are deposited on TiO 2/L-CdS mesoporous film by sequential chemical bath deposition method. The co-sensitization electrode (TiO 2/L-CdS/S-CdS electrode) shows enhancement and broadening of absorption spectrum, in comparison with single-sensitization electrodes (TiO 2/L-CdS and TiO 2/S-CdS electrodes). The conversion efficiency of the semiconductor-sensitized solar cells (SSSCs) prepared with TiO 2/L-CdS/S-CdS electrode is 1.60% which is higher than that of the SSSCs prepared with TiO 2/L-CdS and TiO 2/S-CdS electrodes.

Single step synthesis of highly stable good quality water soluble semiconductor/dendrimer nanocomposites through irradiation route

Gamma irradiation method has been used successfully to prepare nanocrystalline CdS/dendrimer nanocomposites in both aqueous and non-aqueous media at room temperature under ambient pressure. Sodium thiosulfate and carbon disulfide were used as sulfur sources in aqueous solution or in methanol. To the best of our knowledge, this is the first report of room temperature synthesis of semiconductor/dendrimer nanocomposites through gamma irradiation route. The sizes of CdS nanoparticles within the nanocomposites were found to be 3.1 and 2.9 nm in water and methanol, respectively, under identical conditions. Dependence of generation, core and surface functionality of dendrimer on particle size, distribution and also on surface charge has been investigated. Small area electron diffraction (SAED) pattern shows that different phase of CdS nanocrystallites in the composite materials can be generated in the present method if sulfur source is varied. Interestingly, in contrast to the available methods, the present radiolytic process has enabled to produce CdS nanoparticles within the dendrimer matrix with narrow size distribution (as low as 6%) along with increased stability. Our adopted method is suitable for synthesis of nanocomposites in aqueous medium, which is a pre-requisite for biomedical applications.

Biosynthesis of CdS nanoparticles: An improved green and rapid procedure

A low-cost green and reproducible microbes (Lactobacillus sp. and Sachharomyces cerevisiae) mediated biosynthesis of CdS nanoparticles is reported. The synthesis is performed akin to room temperature in the laboratory ambience. X-ray and transmission electron microscopy analyses are performed to ascertain the formation of CdS nanoparticles. Individual nanoparticles as well as a few aggregate having the size of 2.5-5.5nm are found. UV-vis spectroscopy study revealed the surface plasmon resonance at 393 and 369nm respectively for Lactobacillus and yeast assisted synthesis of CdS nanoparticles. The absorbance spectra were used to estimate the values of optical band gap and particle size of CdS nanoparticles. A possible involved mechanism for the biosynthesis of CdS nanoparticles has also been proposed.

Growth mechanism and optical property of CdS nanoparticles synthesized using amino-acid histidine as chelating agent under sonochemical process

Using amino-acid histidine as chelating agent, CdS nanoparticles have been synthesized by sonochemical method. It is found that by varying the ultrasonic irradiation time, we can tune the band gap and particle size of CdS nanoparticles. The imidazole ring of histidine captures the Cd ions from the solution, and prevents the growth of the CdS nanoparticles. The deviation in the linear relation in between cube of radius of nanoparticles and ultrasonic irradiation time confirms the growth of CdS nanoparticles occur via two process; one is the diffusion process of the reactants as well as reaction at the surface of the crystallite. CdS nanoparticles synthesized using histidine as organic chelating agent have band edge emission at ∼481 nm and have greater photoluminescence intensity with blue-shift to higher energy due to typical quantum confinement effect.

Nanomaterials based on CdS nanoparticles in polyethylene matrix

The synthesis of CdS nanoparticles stabilized in the bulk of a polyethylene matrix is described. The size of synthesized nanoparticles is determined by means of transmission electron microscopy. The composition of nanoparticles is defined by X-ray phase analysis. It is shown that the variation of the process-dependent parameters during synthesis of nanoparticles in a polymer + oil solution melt results in the formation of CdS nanoparticles with average sizes of 4.9, 5.4, and 6.2 nm with a reasonably narrow size distribution and well-formed structure. The optical properties of synthesized nanomaterials are investigated. The investigation of Raman scattering reveals softening of the LO-phonon mode with decreasing CdS nanoparticle size. A broad high-energy band of photoluminescence connected with the exciton annihilation in conditions of size quantization is detected.

Photocatalytic growth of CdS, PbS, and Cu xS nanoparticles on the nanocrystalline TiO 2 films

The CdS/TiO 2, PbS/TiO 2, and Cu x S/TiO 2 nanocomposites were synthesized via the photocatalytic reduction of sulfur on the surface of nanocrystalline TiO 2 films. The photocatalytic synthesis produced smaller CdS nanoparticles in the comparison with the conventional chemical deposition of cadmium sulfide. The mean size of CdS nanoparticles can be varied by changing the illumination intensity and the TiO 2 film calcination temperature. An AFM study of the surface structure of CdS/TiO 2 and PbS/TiO 2 nanocomposites showed that the photocatalytic deposition results in formation of the polycrystalline 7–80 nm (CdS) or 20–30 nm (PbS) long nanorods. Spatial separation of the photogenerated charge carriers in CdS/TiO 2 and PbS/TiO 2 nanocomposites was assumed to be the driving force of the formation of such elongated metal sulfide nanoparticle agglomerates.

Fine-Tuning Nanoparticle Size by Oligo(guanine)n Templated Synthesis of CdS: An AFM Study

We are presenting a method for modulating the size of CdS nanoparticles by templating their formation with oligo(guanine)n oligomers where n varied from 5 to 20. The variation in template length resulted in observable changes in the size distribution of the CdS nanoparticles. Statistical analysis of AFM images showed a general trend whereby the CdS average height decreased for longer oligoGn and increased for shorter oligoGn. Concomitantly, shorter oligoGn yielded more dispersed populations, while longer oligoGn gave less dispersed populations. This synthetic methodology could be extended to the synthesis of other nanoparticles and even to mixed-metal nanoparticles resulting in a powerful method for fine-tuning size-dependent properties.

Relationship between size of cadmium sulfide nanoparticles and water pool diameter in reverse micelles

Preparation of CdS nanoparticles in water sodium bis(2-ethylhexyl) sulfosuccinate isooctane reverse micelles with various water contents is studied. A direct correlation between the water pool diameter in the reverse micelles and the mean size of CdS nanoparticles is found. DOI: 10.1134/S1070427207090212 Recently a great interest has been attracted to prep- aration and characterization of nanomaterials (1). Reverse micelles in hydrocarbon solvents proved to be appropriate systems for nucleation and growth of nanoparticles. Water droplets (pools) in surfactant- based micelles act not only as microreactors, but also as steric inhibitors of aggregation of atoms and mole- cules. Micellar synthesis was used to prepare various nanomaterials, among them CdS (see review (2)). Cadmium sulfide is a semiconductor used as a work- ing medium in lasers and also as a material for fab- rication of photoresistors, photodiodes, and solar bat- teries. The advantages of the synthesis of nanopar- ticles in reverse micelles are, first, in mild conditions of the process (no high temperature and pressure is required) and, second, in that the size and shape of nanoparticles can be controlled by the micelle struc- ture and dynamics. Presently, in this research field, the major focus is on preparation and characterization of nanoparticles, but not on properties of the dispersions. Particularly, it remains to be understood whether the properties of the micelles and microemulsions are different in the course of synthesis of nanoparticles.

Photoinduced variations in the size of nanoparticles of CdS in colloidal solutions

The possibility of decreasing the size of colloidal nanoparticles of CdS in the oxidative photocorrosion reaction in the presence of methylviologen and of increasing their size during photocatalytic reduction of sulfur in ethanol in the presence of cadmium acetate. A dependence of the quantum yield of the latter reaction on the initial size of CdS nanoparticles was observed, which was interpreted as a result of quantum size effects.

Nanoparticle Formation in Water-in-Oil Microemulsions: Experiments, Mechanism, and Monte Carlo Simulation

The dynamics of nanoparticle formation in water-in-oil microemulsions via temporal size evolution has been followed from UV-visible absorption spectra of CdS nanoparticles. Existing Monte Carlo (MC) simulations of nanoparticle formation are primarily based on the mechanism of nuclei formation and their growth by coalescence-exchange of drops, which alone do not predict particles of large size as observed in some experiments. Hence, we have included an additional size enlargement process, namely coagulation of nanoparticles during drop coalescence. We find that particle coagulation, constrained by microemulsion drop size, shows very good agreement with our experimental data on CdS nanoparticle size evolution, for different drop sizes. Thus a combined approach of spectroscopy and MC simulation is helpful in elucidating the mechanism of nanoparticle formation in these confined systems, leading to prediction of size-controlled nanoparticle synthesis.

Low-temperature solid-state synthesis and phase-controlling studies of CdS nanoparticles

IntroductionIn recent years, intensive development of nanocrystal-line materials in nanotechnology has occurred world-wide. CdS has been an important semiconductor owingto its unique electronic and optical properties, and itspotential applications in solar energy conversion, non-linear optical, photoelectrochemical cells and hetero-geneous photocatalysis [1, 2]. To date, synthesis ofnanosized CdS has been a subject matter of immenseinterest and its synthesis has been tried by variousmethods [3–14]. However, either complex processcontrol, reagents or long synthesis time would berequired for these routes.Recently, solid-state reaction has been developed inthe synthesis of nanomaterials due to its many advan-tages: no need for solvent, no pollution, simple processand so on [15–21]. Though CdS nanoparticles have alsobeen synthesized by room temperature solid-statereaction [22], further studies about the particles growthhave scarcely been reported. Herein, we report on thefurther growth studies of high quality CdS nanoparti-cles synthesized by a simple low-temperature solid-state reaction. Different surfactants have been intro-duced to the reaction process, and different sizes ofCdS nanoparticles have been obtained under differentreaction temperatures.Also, CdS has two different crystal patterns, whichare cubic and hexagonal, respectively. As we know,cubic CdS is considered a metastable phase whilehexagonal CdS is the thermodynamics stable one of thesemiconductor. Usually it was believed that the phasetransition process of CdS from cubic to hexagonalwould be happened under high temperature or micro-wave radiation [23], and the research on this transitionprocess has been reported [24]. In this paper, it wasfound that crystal patterns of CdS nanoparticles wouldbe easily controlled by the suitable surfactant oraddition, and this phase-controlling could be carriedout in low-temperature solid-state reaction, which isvery interesting and simple.ExperimentalChemicalsThe cadmium acetate (AR) Cd(CH

Population Balance Models and Monte Carlo Simulation for Nanoparticle Formation in Water-in-Oil Microemulsions: Implications for CdS Synthesis

We address controlled CdS nanoparticle formation by tuning experimental synthesis conditions. To this end, a bivariate population balance equation (PBE) model has been developed based on time scale analysis, to explain the mechanism of nanoparticle formation in self-assembled templates. It addresses the process of mixing two water-in-oil (w/o) microemulsions, each containing a pre-dissolved reactant in the microemulsion drops. Brownian collision and coalescence of two water drops of nanometer size results in mixing and exchange of reactant molecules, leading to chemical reaction. The water insoluble reaction product nucleates to form a nanoparticle in an individual drop, which subsequently grows internally by consuming the excess product and by coalescence-exchange with other drops. Finite rates of nucleation and coalescence-exchange are accounted for in the PBE, while the rates of reaction and internal growth of nanoparticles are found to be instantaneous. Experimentally proven binomial redistribution of reactant and product molecules upon drop coalescence is implemented in the present work. This results in a very good prediction of experimental data of the mean aggregate number (MAN) and hence size of CdS nanoparticles. Both our model and Monte Carlo (MC) simulation quantitatively capture the reported variation of MAN with molar excess of Cd2+ concentration and microemulsion drop size. Our results together with previous experimental data establish that usage of stoichiometrically five times or more of excess Cd2+ concentration can cause surface adsorption and desirable enhanced emission intensity of CdS nanoparticles, without altering particle size. We also propose a simplified and computationally efficient univariate PBE model. The univariate model gives very fast (in minutes) and accurate estimates (for low reactant concentrations) of the number and mean size of CdS nanoparticles. Time-scale analysis offers a good a priori choice of the appropriate model based on range of reactant concentrations.