Hexagonal Phase Of CdS Research Articles

Fabrication of large area nanorod like structured CdS photoanode for solar H2 generation using spray pyrolysis technique

Large area nanorod like structured CdS films (9 × 9 cm2) were deposited on the FTO glass substrate using simple and economic spray pyrolysis deposition technique for photoelectrochemical (PEC) hydrogen production. With an intention of electrode scaling-up, the deposition area of photoanode was varied to evaluate its effect on the PEC hydrogen generation capability. High photocurrent of 5 mA has been achieved from the PEC active area of 37.5 cm2. Its unit area (1 cm2) counterpart yielded Solar-to-Hydrogen (STH) conversion efficiency of 0.20% at a bias of 0.2 V vs Ag/AgCl using sacrificial reagents under solar simulator (AM1.5) with 80 mW/cm2 irradiance. The 500 nm thick film exhibiting uniformly distributed nano-rod features yielded 3-times more photocurrent, as well as hydrogen evolution than other films. It exhibited an enhanced photo-activity as indicated by the higher IPCE values (5–9%) in the wavelength range of 450–550 nm. It exhibited superior optical properties (Eg ∼2.4eV), and formation of high crystallinity hexagonal CdS phase with space group P63MC. The superior performance of the photoanode is attributed to the nanostructured morphology acquired under optimized spray pyrolysis conditions. Large area photoanodes showed unaltered photo-activity indicating the homogeneity in the film properties even in scaled-up version.

Colloidal-route synthesis of N-butylaniline capped ZnS and CdS nanoparticles

A new secondary amine (N-butyl aniline) has been used as surfactant to synthesize monodispersed ZnS and CdS nanoparticles via the colloidal-route. The structural nature and optical properties of the as-synthesized nanoparticles have been analyzed. The average diameter of the ZnS and CdS nanoparticles are approximately 4nm and 6nm respectively. X-ray diffraction pattern confirms the cubic phase of ZnS and hexagonal phase of CdS.

Understanding the “Tailoring Synthesis” of CdS Nanorods by O2

Parameters such as solution concentrations and composition of the ambient atmosphere are known to be important in phase and morphology control in the solvothermal synthesis of CdS semiconductor nanorods (NRs), but a clear understanding of the underlying mechanisms involved is lacking. In this work, a series of experiments were performed to demonstrate that the key factor affecting the phase and morphology of CdS NRs is the amount of O(2) in the space above the reaction solution in the sealed vessel relative to the amount of precursors in solution: O(2)-depleted conditions resulted in more cubic phase CdS and thick polycrystalline NRs with an aspect ratio usually less than 3, which have small blue shifts in band-edge emission and little surface trap emission, while O(2)-rich conditions resulted in more hexagonal-phase CdS and slim single-crystal NRs, which have significantly blue shifted band-edge emission and relatively strong surface trap emission. Thus, increasing the amount of solution in the vessel, changing the ambient atmosphere from air to N(2), and increasing the reagent concentration all lower the molar ratio of O(2) to reagents and lead to more cubic phase and thicker NRs. The results indicate that the composition of the "empty" section of the reaction vessel plays as important a role as the composition of the liquid in determining the phase and morphology, something that has been overlooked in earlier work. A mechanism to explain the effect of oxygen on the nucleation and growth stages has been proposed on the basis of those results and further supported by shaking experiments and ZnS NR synthesis manipulation. The CdS NRs synthesized under different conditions showed obvious differences in photocatalytic activity, which indicated that controlling the synthetic process can lead to materials with tailored photocatalytic activity.

Hydrothermal synthesis of CdS microparticles–graphene hybrid and its optical properties

A reduced graphene oxide–CdS microparticles (RGO–CdS) hybrid was prepared through a one-pot hydrothermal method in which graphene oxide (GO) served as the support and cadmium chloride as the starting material. GO was reduced to RGO during a hydrothermal reaction. The morphology, structure characterization, and crystal structure of the as-prepared hybrid were performed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. It was shown that in the composite, the CdS microparticles were dispersed uniformly in the RGO sheet, and the addition of GO did not influence the crystal structure of the hexagonal phase CdS. The as-prepared RGO–CdS hybrid shows efficient fluorescent features due to the size effect of the CdS microparticles. By combining the unique properties of RGO and CdS microparticles, the strategy presented in this study is expected to be useful to prepare highly efficient graphene-based hybrids for potential applications in various fields.

Interstitial sulfur photoluminescence in thermochemically synthesized CdS nanocrystals (NCs)

We have synthesized CdS NCs (NCs) by a thermochemical approach. CdSO4 and Na2S2O3 were used as the precursors and thioglycolic acid (TGA) was used as capping agent molecule. The structure and optical property of the NCs were characterized by means of XRD, TEM, UV-visible optical spectroscopy and photoluminescence (PL). XRD and TEM analyses demonstrated hexagonal phase CdS NCs with an average size of around 2 nm. Synthesized NCs exhibited a band gap of about 3.21 eV and showed a broad band emission from 400 to 750 nm centered at 503 nm. This broad band emission is related to surface states of CdS and our results showed that the emission peak can be attributed to the interstitial sulfur. The best attained photoluminescence quantum yield of the NCs was about 11%. At the same conditions the PL quantum yield of TGA capped NCs was about 20 times higher than that of TG capped NCs.

Ionic liquid-assisted synthesis, structural characterization, and photocatalytic performance of CdS nanocrystals

With the assistance of the ionic liquid trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentylphosphinate), we have successfully synthesized short nanorods, quasi-nanospheres and faceted CdS nanoparticles via thermal decomposition of cadmium diethyldithiocarbamate complexes. It was shown that the shape, size and crystallinity of the products could be controlled through delicate regulation of the reaction temperature, monomer concentration, reaction time, and ionic liquid ratio. We found that higher temperature was beneficial to the good crystallinity, while the lower temperature and higher monomer concentration were in favor of anisotropic structures. The used ionic liquid contributed to the formation of hexagonal phase CdS nanocrystals, and its ratio played an important role in determining the ultimate morphology of products. The possible mechanism for the formation CdS nanocrystals was proposed. Furthermore, the as-prepared CdS samples demonstrated a highly photocatalytic activity in the degradation of methyl orange under visible light irradiation.

Synthesis of CdS nanocrystals by a microwave activated method and investigation of the photoluminescence and electroluminescence properties

We have synthesized CdS nanocrystals (NCs) by a microwave activated method. CdSO4 and Na2S2O3 were used as the precursors and thioglycolic acid (TGA) was used as capping agent molecule. The aqueous synthesis was based on the heat sensitivity of Na2S2O3. In this method, microwave irradiation creates the activation energy for dissociation of Na2S2O3 and leads to the CdS NCs formation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses demonstrated hexagonal phase CdS NCs with an average size around 3nm for sample prepared at 5min irradiation time. A band gap range of 3.38–2.89eV was possible only by increasing the microwave irradiation time, corresponding to a 2.7–3.7nm size. Photoluminescence (PL) spectra showed a white emission between 400 and 750nm. The best attained PL quantum yield (QY) of the NCs was about 10%. Synthesized NCs were used as emissive layer in a light emitting device (LED) with ITO/PEDOT:PSS/PVK/CdS-NCs/AL structure. Turn on voltage of fabricated device was about 7V. The CIE color coordinate of the LED at (0.34, 0.43) demonstrated a near white light LED with an emission on green-yellow boundary of white.

Template-free solution approach to synthesize CdS dendrites with SCN based ionic liquid

Cadmium sulfide dendrites were synthesized by a facile hydrothermal treatment from CdCl 2 and ionic liquid 1-butyl-3-methlyimidazole thiocyanate acted both as sulfur source and surfactant. The product was characterized by means of X-ray powder diffraction and scanning electron microscopy. X-ray powder diffraction studies indicated that the product was well-crystallized hexagonal phase of CdS, and the scanning electron microscopy images showed that the obtained powders consisted of a wealth of well-defined CdS dendritic microstructures with a pronounced trunk and highly ordered branches. The UV–Vis and photoluminescence spectroscopy measurements were taken as well. The possible formation mechanism of CdS dendrites was simply proposed in the end.

Investigation of the photoluminescence properties of thermochemically synthesized CdS nanocrystals

In this work we have synthesized CdS nanocrystals with thermochemical method. CdSO4 and Na2S2O3 were used as the precursors and thioglycolic acid (TGA) was used as capping agent molecule. The structure and optical property of the nanocrystals were characterized by means of XRD, TEM, UV-visible optical spectroscopy and photoluminescence (PL). X-ray diffraction (XRD) and TEM analyses demonstrated hexagonal phase CdS nanocrystals with an average size around 2 nm. Synthesized nanocrystals exhibited band gap of about 3.2 eV and showed a broad band emission from 400-750 nm centered at 504 nm with a (0.27, 0.39) CIE coordinate. This emission can be attributed to recombination of an electron in conduction band with a hole trapped in Cd vacancies near to the valance band of CdS. The best attained photoluminescence quantum yield of the nanocrystals was about 12%, this amount is about 20 times higher than that for thioglycerol (TG) capped CdS nanocrystals.

Biotemplated preparation of CdS nanoparticles/bacterial cellulose hybrid nanofibers for photocatalysis application

In this work, we describe a novel facile and effective strategy to prepare micrometer-long hybrid nanofibers by deposition of CdS nanoparticles onto the substrate of hydrated bacterial cellulose nanofibers (BCF). Hexagonal phase CdS nanocrystals were achieved via a simple hydrothermal reaction between CdCl 2 and thiourea at relatively low temperature. The prepared pristine BCF and the CdS/BCF hybrid nanofibers were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), UV–vis absorption spectroscopy (UV–vis), and X-ray photoelectron spectroscopy (XPS). The results reveal that the CdS nanoparticles were homogeneously deposited on the BCF surface and stabilized via coordination effect. The CdS/BCF hybrid nanofibers demonstrated high-efficiency photocatalysis with 82% methyl orange (MO) degradation after 90 min irradiation and good recyclability. The results indicate that the CdS/BCF hybrid nanofibers are promising candidate as robust visible light responsive photocatalysts.

Investigation of the Photoluminescence Properties and Nonlinear Optical Responses of Thermochemically Synthesized CdS Nanoparticles

In this work, we have investigated the nonlinear optical properties of thermochemically synthesized CdS nanoparticles, The structure and optical property of the nanopartilces were characterized by means of XRD, UV-visible optical spectroscopy, and photoluminescence (PL) and Z-scan technique was used to measure the nonlinear refraction and absorption indexes. X-ray diffraction (XRD) analysis demonstrated hexagonal phase CdS nanoparticles with an average size around 1.8 nm. Band gap of nanocrystals was about 3.2 eV and they showed a broad band emission from 400–750 nm centered at 504 nm. The nonlinear refractive index was about in order of 10−8 (cm2/W), and the nonlinear absorption coefficient was obtained in order of 10−3 (cm/W) with negative sign. The linear absorption coefficient (α was obtained about 2.62 cm−1.

Cadmium (II) pyrrolidine dithiocarbamate complex as single source precursor for the preparation of CdS nanocrystals by microwave irradiation and conventional heating process

The complex of cadmium with pyrrolidine dithiocarbamate Cd(pdtc)2 has been used as single source precursor for the synthesis of CdS nanoparticles. The formation of CdS nanostructures was achieved by thermal decomposition of the complex under microwave irradiation and conventional heating in presence of hexadecylamine. The CdS nanoparticles with disordered close-packed structure were obtained under microwave irradiation, whereas wurtzite hexagonal phase CdS nanorods were obtained by conventional heating method (up to 150°C). Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and high resolution transmission electron microscopy (HRTEM) studies also were carried out to study the structure and morphology of nanoparticles. The optical property of the CdS nanoparticles was studied by UV–visible and fluorescence emission spectral studies. Fluorescence measurements on the CdS nanoparticles show a strong emission spectrum with two sub bands that are attributed to band-edge and surface-defect emissions. The reduction of a suitable cadmium metal complex is considered to be one of the single pot methods to generate CdS semiconductor nanoparticles with different shapes and high yield.

Preparation of p-type CdS thin films and in situ dark conductivity in vacuum deposited CdS:Cu films

CdS:Cu thin films were prepared using a vacuum co-evaporation technique. The Hall measurements indicate that the conductivity characteristic of CdS thin films transformed from highly compensated in as-grown or weakly annealed materials to p-type conductive in strongly annealed materials. X-ray diffraction spectra show that as-deposited thin films were the hexagonal phase of CdS except the presence of copper for high Cu doping and the diffraction peaks of Cu disappeared after annealing. From the X-ray photoelectron spectroscopy we found the ionization of Cu atoms and the formation of an acceptor level. In situ dark conductivity in vacuum as-deposited CdS:Cu was performed in the temperature range between 27 and 250 °C. An abnormal temperature dependence of conductivity was observed in medium and heavily Cu-doped films. The formation of a p-type material at a certain temperature was also studied by the hot probe measurements, which indicates a complex compensation process in the Cu-doped CdS films.

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.

Preparation of CdS/TiO2NTs Nanocomposite and Its Activity of Photocatalytic Hydrogen Production

The CdS/TiO 2 NTs nanocomposite was prepared through ion-exchange and precipitation reactions. The nanostructure properties of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-visible absorption spectra (DRUVAS), fluorescence emission spectra (FES) and X-ray fluorescence analyzer (XRF). SEM results revealed that the lamellar sodium trititanate originating from the TiO 2 particles individually curled to form the sodium trititanate nanotubes by self-assembled mechanism. The results of XRD, TEM and DRUVAS demonstrated that hexagonal phase CdS with about 8 nm particle size were homogeneously loaded on the surface of anatase TiO 2 NTs and the absorption edge of the composite was extended to the visible region. The CdS/TiO 2 NTs composite exhibited the highest activity of hydrogen production (1708 μL/g) by photocatalytic water decomposition in comparison with TiO 2 NTs and TiO 2 powder under visible light irradiation (λ > 400 nm) for 6 h.

Photocatalytic decolorization and degradation of Congo Red on innovative crosslinked chitosan/nano-CdS composite catalyst under visible light irradiation

The crosslinked chitosan/nano-CdS (CS/n-CdS) composite catalyst prepared by simulating bio-mineralization process was extensively characterized by FT-IR spectra, XRD, SEM, TEM and TGA. An azo dye, Congo Red (CR), was used as model pollutant to study its photocatalytic activity under visible light irradiation. The influences of catalyst amount, initial CR concentrations, pH of the reaction solution and different anions on CR decolorization and degradation reaction kinetics were investigated. Results of characterization indicated the successful formation of hexagonal phase of CdS on raw chitosan under mild conditions. The photocatalytic degradation was found to follow a pseudo-first-order kinetics according to Langmuir–Hinshelwood (L–H) model. The dye could be decolorized more efficiently in acidic media than alkaline media. The presence of NO 3 − accelerated evidently the degradation of CR, while the other chosen anions (Br −, SO 4 2− and Cl −) had an inhibitory effect on the decolorization of CR, of which the inhibitory effect of Cl − was the most pronounced. UV–vis spectra were analyzed to indicate that degradation of CR in the solution was the break up of the N N bonds and degradation of aromatic fragment in this reaction system. The recycling experiments confirmed the relative stability of the catalyst.

Growth and mechanism of CdS nanorods by microstructure analysis

Nanorods of II–VI semiconductor CdS are prepared from simple precursors by wet chemical method. The CdS nanorods are characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). XRD studies showed that the crystal structure of the nanorods is in the hexagonal phase of CdS. The preferred orientation of (0 0 2) direction suggests that the nanorods of CdS is grown along (0 0 2) direction. The growth direction is further confirmed by microstructural analysis using HRTEM. Growth mechanism of the nanorods is explained on the basis of the population balance equation (PBE) model. The PBE model explains that the initially formed nanodots undergo oriented attachment (under ageing) along a particular direction having effective dipole moment (in the case of CdS it is (0 0 2) followed by coalescence leading to the smooth nanorods). This process takes place by ageing of the reaction solutions. The quasi-spherical nature of the particles results in a non-integral aspect ratio for the nanorods. Optical studies by UV–vis spectroscopy show a blue-shifted absorption at 493 nm because of the quantum confined excitonic absorption.

Phase transition of CdS in the presence of ethylenediamine and formation of hollow CdS submicron particles with needle-like structure

Solid submicron particles, composed of amorphous, hexagonal and cubic phase CdS, were synthesized in water–ethylenediamine solution by precipitating Cd2+ ions with S2− ions, which were generated from the radiolytic reduction of Na2S2O3. In addition, the effects of the absorbed dose on the crystallization process of CdS were investigated in detail. Moreover, hollow CdS submicron particles with needle-like structure could be obtained from the solid CdS submicron particles probably through a hollowing process based on Ostwald ripening and the phase transition of CdS from amorphous to crystalline. In the above processes, ethylenediamine played an important role.

Synthesis of CdS nanowires using nanoporous alumina template

Hexagonal Porous Alumina (PA) nanostructures with ordered pores have been fabricated using two-step anodisation of aluminium. CdS nanowires of diameters between 50?60 and 100?110 nm have been grown on PA templates by two different chemical and electrochemical techniques. Microstructural properties of the nanowires have been investigated using Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Selected area electron and X-ray diffraction patterns show the growth of polycrystalline nanowires with hexagonal CdS phase. Optical properties of CdS nanowires grown by two different methods have been studied using optical absorption, Photoluminescence (PL) and Raman spectroscopy.

Raman monitoring of wide bandgap MBE growth

The combination of Raman spectroscopy and molecular beam epitaxial (MBE) growth can supply valuable additional information on interface and layer formation. Here the growth of CdS on InP(100), that of undoped and nitrogen doped ZnSe on GaAs(100) as well as the nitridation of GaAs(100) serve as examples for the usefulness of this in situ and on line technique. In particular, evidence for a reaction in the initial phase of CdS/InP(100) interface formation and the transformation from the cubic to the hexagonal phase of CdS at around 200 nm layer thickness is provided. In the case of ZnSe growth on GaAs(100) the incorporation of nitrogen in the layer results in a deterioration of the ZnSe layer crystallinity together with the appearance of compressive strain in the GaAs substrate. The latter is assigned to nitrogen diffusion into the substrate which is further supported by a nitridation experiment of GaAs which also leads to the formation of a thin layer of GaN. Moreover, the underlying substrate is heavily disturbed as can be judged from the detection of As cluster.