CdS Powder Research Articles

Design and Synthesis of Novel Single-Crystalline Hierarchical CdS Nanostructures Generated by Thermal Evaporation Processes

Through thermal evaporation of a mixture of CdS and graphite powder, we produced a novel hierarchical nanostructure of single-crystalline CdS. It is in the form of cuspidated double headed nanocomb. In the absence of graphite powder, the thermal evaporation of powder CdS alone would result in the formation of CdS nanobelts. The hexagonal wurtzite phase of the CdS nanostructures was verified by XRD, and the single crystallinity confirmed by SAED. As revealed in FESEM and TEM analysis, the obtained hierarchical CdS nanocomb has 2-fold symmetry and the teeth grown perpendicular to the comb trunk are nanospikes of much smaller size. A mechanism for the growth of the hierarchical CdS nanocombs and CdS nanobelts has been described. In the study of optical properties of the CdS nanomaterials, we observed that the photoluminescence peak of CdS nanocombs showed a red-shift of ∼7 nm in comparison to that of CdS nanobelts.

CdS Powders Obtained by Chemical Bath Deposition

We studied the influence of the mixing on the properties of CdS powders obtained by Chemical Bath Deposition. The powders were obtained from baths containing cadmium chloride, thiourea, and ammonia. The obtained powders were characterized using FT-IR, in order to evaluate the purity of the obtained powder. Granulometric studies were made in order to establish the grain size distribution of the particles, and X ray diffraction in order to determine the structure of nanostructured CdS.

ChemInform Abstract: Preparation and Photocatalytic Properties of Silica-Supported Fine CdS Powders.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Interfacial Charge Carrier Dynamics in Core−Shell Au-CdS Nanocrystals

The interfacial charge carrier dynamics for core−shell Au-CdS nanocrystals with various shell thicknesses were investigated and presented. Due to the difference in band structures between Au and CdS, a pronounced photoinduced charge separation took place at the interface of Au and CdS, resulting in the electron-charged Au core and the hole-enriched CdS shell. The electron-charging of Au core in Au-CdS nanocrystals was revealed with the corresponding XPS analysis and photocurrent measurement. Time-resolved PL spectra were measured to quantitatively analyze the electron transfer event between CdS shell and Au core for Au-CdS nanocrystals. An increase in the electron-transfer rate constant was observed for Au-CdS nanocrystals with increasing shell thickness, probably due to the less pronounced electron−hole interaction of thicker CdS, which enabled a fuller extent of participation of photoexcited electrons in the charge separation process. On the other hand, the hole-enriched CdS shell of Au-CdS nanocrystals upon light illumination was characterized with a photocatalytic process. The photocatalytic activity of Au-CdS nanocrystals was found to increase with increasing shell thickness, attributable to the greater capability of light absorption achieved by the extensive growth of the CdS shell. The correlation of photocatalytic activity with the shell thickness of Au-CdS nanocrystals corresponded well with that of the electron-transfer rate constant. As compared to the relevant commercial products like N-doped P-25 TiO2 and CdS powders, the as-synthesized Au-CdS nanocrystals exhibited superior photocatalytic performance under visible light illumination, demonstrating their potential as an effective visible-light-driven photocatalyst. Furthermore, the result of performance evaluation under natural sunlight shows that the present Au-CdS nanocrystals can be used as highly efficient photocatalysts which may practically harvest energy from sunlight.

Properties of CdS films deposited by the electron beam evaporation technique

Abstract Thin CdS films were electron beam evaporated. The CdS powder synthesized in the laboratory by a chemical method was used as source for the deposition of films. Clean glass substrates were used. The substrate temperature was varied in the range of 30–250 °C. X-ray diffraction studies indicated polycrystalline hexagonal structure. The band gap was 2.39 eV. The grain size was 25–35 nm and the surface roughness was 0.3–1.5 nm with increase of substrate temperature. Photoconductive cells fabricated with the doped and undoped films have exhibited high photosensitivity and high signal to noise ratio. The current voltage characteristics were linear.

Manifestation of metastable cubic modifications in finely dispersed A2B6 compounds

The presence of metastable cubic modifications has been revealed by X-ray diffraction in polycrystalline CdS and CdSe powders with grain sizes on the order of several dozen nanometers. The optical reflection and photoluminescence spectra of the cubic CdS phase have been measured in the temperature interval of 77–295 K. The main exciton transition energies and the temperature coefficients of the bandgap width variation have been determined.

Arm-Length-Controlled Synthesis, Field Emission, and Luminescence of CdS Multipods

At a low temperature of 550 °C, multiarmed CdS nanostructures were successfully prepared by thermal evaporation of CdS powders without use of any catalysts. The length and tip diameter of the arms in CdS multipods could be controlled by simply varying the growth time. With the arm length increasing, the tip diameter successively decreases. Short-armed multipods (SMPs) are made of both zinc blende and wurtzite phase CdS, while medium-armed multipods (MMPs) and long-armed multipods (LMPs) consist of only hexagonal phase CdS. LMPs exhibit good field-emission (FE) properties with relatively high field-enhancement factor and enhanced luminescence compared to SMPs and MMPs because of the needle-shaped arms and high crystallinity. Besides bind energy emission of CdS, LMPs exhibit a broad red emission in CL spectrum because of the arms with high aspect ratios.

Hierarchical Cd4SiS6/SiO2 Heterostructure Nanowire Arrays

Novel hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays were fabricated on silicon substrates by a one-step thermal evaporation of CdS powder. The as-grown products were characterized using scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Studies reveal that a typical hierarchical Cd4SiS6/SiO2 heterostructure nanowire is composed of a single crystalline Cd4SiS6 nanowire core sheathed with amorphous SiO2 sheath. Furthermore, secondary nanostructures of SiO2 nanowires are highly dense grown on the primary Cd4SiS6 core-SiO2 sheath nanowires and formed hierarchical Cd4SiS6/SiO2 based heterostructure nanowire arrays which stand vertically on silicon substrates. The possible growth mechanism of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays is proposed. The optical properties of hierarchical Cd4SiS6/SiO2 heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.

Spectroscopic Analysis and Synthesis of Wide Band Gap CdS Quantum Dots Using Colloidal Synthesis Technique at Low Temperature

A broad range of II-VI materials has been investigated in order to produce light in the full visible range for optoelectronic applications. The present investigation was carried out for the spectroscopic analysis and synthesis of wide band gap cadmium sulfide nanoparticles. Large-band gap semiconductors have the added advantage in that; they can support higher electric field before breaking down, which means that they can be used for high-power electronic devices.Synthesis has been carried out using colloidal synthesis technique at low temperature. The size, stabilization and optical properties were studied using UV-vis Spectrophotometer and Spectroflourometer. Further, the structural studies of synthesized powder were carried out using X-ray diffraction technique; which also confirms the formation of desired product. The capping ligand and the impurities present in the sample were characterized by Fourier transform infra red spectroscopy. Synthesized CdS powder dispersed in aqueous media gave the value of 193 nm for the onset wavelength using UV-vis spectrophotometer, which is significantly blue-shifted compared to bulk CdS and shows the quantum confinement effect. From the onset wavelength the radius of CdS quantum dot calculated using the Brus equation was found to be ca. 0.7 nm.

Bicrystalline CdS Nanoribbons

We report the synthesis and characterization of a unique CdS architecture made of two intersecting ribbons that form a ridge-shaped bicrystalline CdS nanoribbon via simple thermal evaporation of CdS powder. The CdS bicrystalline nanoribbons have a tapering width decreasing from 600 to 50 nm and lengths of several tens of micrometers. The nanostructures show strong band gap emission and weak defect-related emission. Zigzag CdS bicrystalline nanoribbons are occasionally formed at the tip region.

Preparation, characterization and growth mechanism study of CdS/Cr nanostructures

Abstract Dentiform nanorods and tassellike nanowires CdS/Cr nanostructures were synthesized via a simple one-step thermal evaporation of CdS and Cr metal powder in mass scale. The morphology and detailed nanostructures were characterized by using scanning electron microscope, X-ray diffraction, and transmission electron microscope. The dentiform nanorods were fabricated at a low Ar flow rate, while the tassellike nanowires were created at a higher Ar flow rate. It is found that CdS/Cr dentiform nanostructures are the Cr-doped CdS nanostructure, whereas the tassellike nanowires CdS/Cr heterostructures are CdS nanowires attached with Cr particles on their surfaces. The selected area electron diffraction pattern indicates the Cr particle is polycrystalline, attributable to the {1 1 0}, {2 0 0} crystal planes of Cr. The formation of the CdS/Cr tassellike nanowires was initiated by the Au catalyst vapor–liquid–solid mechanism, and vapor–solid process also played a role in the defining the dentiform nanostructures. Photoluminescence measurements show that the tassellike nanowires have three emission bands around 468 nm, 510 nm and 718 nm, which originate from the enwrapped Cr, the band-gap of bulk CdS backbones and the surface defects of the CdS, respectively.

Novel CdS Nanostructures: Synthesis and Field Emission

Here, we reported the success in the synthesis of novel CdS nanostructures, nanotubes, core-sheath nanowires, and tube−wire nanojunctions, by thermal evaporation of CdS powder and purposed a model for the growth mechanism. The core−sheath nanowires consist of a crystalline core and amorphous sheath. The photoluminescence characterization indicated that the CdS nanostructures were crystalline and showed a narrow peak at 516.5 nm. In addition, the CdS nanostructures exhibited better field emission properties with a field enhancement factor of 1.5 × 10 4 and turn-on field of 1.4 V/μm.

Stimulated emission of CdS nanowires grown by thermal evaporation

High-quality CdS nanowires with wurtzite structure were produced by thermal evaporation of CdS powder. The nanowires were core-shell structures, consisting of crystalline core and amorphous/polycrystal shell. The intensity of the second-order longitudinal phonon mode in the Raman spectrum of the CdS nanowires is higher than that of the first-order mode due to exciton-phonon coupling. The photoluminescence of the CdS nanowires is power dependent, and the photoluminescence peak at 516.5nm becomes narrower with increase in excitation power, indicating the stimulated emission characteristics of CdS nanowires. The population inversion generated by two-photon absorption is mainly attributed to the occurrence of stimulated emission.

The Catalyst-Assisted Synthesis of High Quality CdS Single-Crystal Nanowires Through an Epitaxy Mechanism

High quality wurtzite CdS nanowires have been synthesized by thermal evaporation of CdS powder onto Si substrate in the presence of Au catalyst at 650 degrees C by using pure H2 as a carrier gas. The nanowires were 10 nm in diameter and a few tens of micrometers in length. XRD patterns demonstrated that as prepared CdS is a pure crystalline material. High-resolution transmission electron microscopy of the materials showed that all CdS nanowires grew along (0001). According to analysis of selective area electron diffraction patterns taken from the interface, we proposed that there is a kind of epitaxy relationship in the interface region between Au catalyst and CdS grown, i.e., (0001)CdS // (111)Au, and [1210]CdS // [011]Au.

CdS/SiO2 nanowire arrays and CdS nanobelt synthesized by thermal evaporation

CdS/SiO2 nanowire arrays and CdS nanobelts were synthesized by thermal evaporation of CdS and CdO mixture powders, with highly selective etching occurring on the silicon substrate surfaces. Study of the growth mechanism of CdS/SiO2 nanowire arrays and the growth process of CdS nanobelts showed that the growth of CdS dendrites plays an important role in the formation of CdS/SiO2 nanowire arrays, and that the mechanism of CdS/SiO2 nanowire arrays growth was in good agreement with “self-assembling nanoelectrochemistry”. In the thermal evaporation process, an interaction between Si from silicon substrate and Cd took place.

Synthesis and photoelectrochemical behavior of nanocrystalline CdS film electrodes

Abstract In this paper, we prepared the nanocrystalline CdS films on the indium-doped tin oxide (ITO) glass substrates using a doctor-blade technique. The source CdS powder was first prepared by a hydrothermal method and then ground into a screen-printing paste by adding ethyl cellulose as a binder and terpineol as a solvent. The CdS samples were characterized by XRD, SEM, TEM, and UV–Vis diffuse reflectance spectroscopy. A photocurrent of 3.51 mA/cm2, a fill factor of 0.44, an open circuit photovoltage of 0.50 V, and a conversion efficiency of 2.2% were obtained under a simulated solar illumination of 35 mW/cm2, when the CdS film was annealed at 380 °C in air for 30 min. The maximum quantum efficiency of 5.5% was obtained at an incident wavelength of 500 nm. Our method provides a general way to prepare electrodes of metal chalcogenide nanocrystalline films.

Synthesis and Interface Structures of Zinc Sulfide Sheathed Zinc−Cadmium Nanowire Heterojunctions

Zinc sulfide (ZnS) sheathed zinc (Zn)-cadmium (Cd) nanowire heterojunctions have been prepared by thermal evaporating of ZnS and CdS powders in a vertical induction furnace at 1200 degrees C. Studies found that both the Zn and Cd subnanowires, within a single nanoheterojunction, are single-crystallines with the growth directions perpendicular to the [210] plane, whereas the sheathed ZnS is polycrystalline with a thickness of ca. 5 nm. The Zn/Cd interface structure in the ZnS sheathed Zn-Cd nanowire heterojunctions was thoroughly experimentally studied by high-resolution transmission electron microscopy and theoretically studied using a near-coincidence site lattice (NCSL) concept. The results show that the Cd and Zn have a crystalline orientation relationship as [0001]Zn//[0001]Cd, (10(-)10)Zn//(10(-)10)Cd, (01(-)10)Zn//(01(-)10)Cd, and ((-)1100)Zn//((-)1100)Cd.

Synthesis and stability studies of thiophenol capped CdS nanoparticles

Abstract The results of the studies on the preparation and stability of thiophenol-capped CdS nanoparticles prepared by a non-aqueous chemical method are reported. Solutions of cadmium acetate and sodium sulphide were taken as the precursors and thiophenol was used as a capping agent to control the growth and also to prevent flocculation of the synthesized particles. The synthesized CdS nanoparticles were characterized by the optical absorption and X-ray diffraction (XRD) studies. The blue shift of the optical absorption edge indicated the formation of particles in the nanometer size regime. The particle sizes were estimated from the band gap values obtained from the optical absorption spectra using effective mass approximation (EMA). The CdS powder sample was used for the X-ray Diffraction studies. Broadening of the diffraction peaks with an increase in the stabilizer concentration also suggests the decrease in particle size with increase in the stabilizer concentration. Particle sizes calculated from the X-ray diffraction studies agree fairly well with those estimated from the optical absorption studies. The particle size could be conveniently controlled by adjusting the concentration of the stabilizer. X–ray diffraction studies were also carried out at higher temperatures. Particle size did not change with temperature as indicated by XRD. Stability of the synthesized nanoparticles was studied by recording the optical absorption spectra for 45 days. A change in particle size was observed at lower stabilizer concentrations for the first few days. But at higher stabilizer concentrations there was no change in particle size with time.

Electronic and luminescent properties of Cr-doped cadmium sulfide nanowires

Cr-doped CdS nanowires were synthesized in large scale through thermal co-evaporation of CdS and metal Cr powders. General morphology, detailed microstructure and optical properties were characterized using various techniques. Devices consisting of individual Cr-doped CdS nanowire were fabricated and they exhibited remarkable rectifying characteristics. I-V curves of individual Cr-doped CdS nanowire devices demonstrate that the present nanowires are n-type doped and have high conductivity (10.96 Ω−1cm−1), indicating great potential applications in nanoscale electronic and optoelectronic devices.

The selective synthesis of single-crystalline CdS nanobelts and nanowires by thermalevaporation at lower temperature

CdS nanobelts and nanowires were successfully synthesized by simplethermal evaporation of CdS powder at a temperature as low as650 °C, usingpure H2 as a carrier gas. The morphology of the products could be conveniently controlled byadjusting the deposition parameters. Electron microscopy studies of the materials showedthat the single-crystalline CdS nanowires have a diameter of 200 nm and a length of tens ofmicrometres, and the nanobelts are 100–200 nm in width, 30 nm in thickness and tens ofmicrometres in length. High-resolution transmission electron microscopy demonstrated thatthe nanobelts, which are different from the nanowires growing along the direction, have three types of growth direction: , and . It is demonstrated that a reductive carrier gas, such as hydrogen, plays animportant role in the whole growth process of CdS nanowires and nanobelts.