Hexagonal Phase Of CdS Research Articles

Visible light response and heterostructure of composite CdS@ZnS–ZnO to enhance its photocatalytic activity

In this work, CdS@ZnS–ZnO composites were prepared by the temperature-programmed hydrothermal method combined with the microwave-assisted hydrothermal method. The composite consisted mainly of cubic phase ZnS, hexagonal phase CdS and hexagonal phase ZnO, and presented a spherical structure with relatively uniform size and shape. There were heterostructures between CdS, ZnS and ZnO in the spherical structure. At the same time, the grain size, specific surface area, average pore diameter and pore volume of the composited material changed significantly, and its light absorption performance in the visible light region was obviously enhanced, and the photocatalytic activity was also greatly improved. Under ultraviolet light, CdS@ZnS–ZnO can degrade simulated pollutants by more than 90% within 20 min. In addition, the results of hydrogen evolution from photolysis of water showed that the ternary composite CdS@ZnS–ZnO had excellent hydrogen evolution capacity compared with pure CdS, ZnS and ZnO, whose hydrogen evolution amount can reach 3647 μmol g−1 in 8 h, was 298 times than that of P25. Moreover, it still maintained a high hydrogen evolution capacity after 4 cycles.

Nitrogen-doped graphene quantum dots decorated ZnxCd1-xS semiconductor with tunable photoelectric properties

In this study, ZnxCd1-xS/N-GQDs composites with different Zn/Cd ratios were synthesized via a facile solvothermal process. A series of techniques were introduced to investigate the effect of Zn/Cd ratios and N-GQDs on the performances of ZnxCd1-xS/N-GQDs. The results show that the crystal structure and photoelectric performance of the composites can be tuned via adjusting the Zn/Cd ratios. ZnxCd1-xS/N-GQDs composites transform from a hexagonal structure to a cubic structure with the increase of Zn content, and the diffraction peaks are located between hexagonal phase CdS and cubic phase ZnS. Meanwhile, the photocurrent responses and electrochemical impedance present good tunability via adjusting the Zn/Cd ratios. Zn0.9Cd0.1S/N-GQDs composites with the higher photocurrent value of 3.79 μA cm−2 and lower interfacial impedance are superior to ZnxCd1-xS/N-GQDs composites with other Zn/Cd ratios. Moreover, the introduction of N-GQDs obviously enhances the photoelectric properties of the semiconductor.

STRUCTURAL AND OPTICAL PROPERTIES OF CADMIUM SULFIDE NANOPARTICLES PREPARED BY PRECIPITATION METHOD

Cadmium Sulfide nanoparticles were prepared by a simple and cost effective precipitation method. Xray analysis revealed broad diffraction peaks indicating that the particles are of very small size. The prominent broad peaks at 2θ values of 26.48°, 43.90°, and 51.91°, which could be indexed to the (002), (110) and (112) direction of the hexagonal phase of CdS. Optical studies showed maximum absorbance in the UV region but minimum absorbance in the VIS-NIR regions make it an excellent material for screening off UV portion of electromagnetic spectrum in UV filters and sensors.

Synthesis and photocatalytic property of cubic phase CdS

In order to understand the nanostructure-based architectures and phase structures of CdS on the photocatalytic property, we have synthesized 3 D flower-like CdS with cubic phase and hexagonal phase CdS nanoparticles by hydrothermal method. The as-prepared samples have been characterized by XRD, FESEM, and UV–Vis. The photocatalytic activity has been evaluated by the photocatalytic degradation of methylene blue (MB) under simulated visible-light irradiation. FESEM results reveal that the morphologies of cubic phase CdS are flower-like structures, and the morphologies of hexagonal phase CdS are nanoparticles. The optical energy band gap of flower-like CdS is 2.25 eV from UV–Vis result. Moreover, the flower-like CdS exhibits better photocatalytic activity and its highest degradation rate to MB can reach 90.4% than that of CdS nanoparticles.

Electrochemical investigation of hybridized WO3–CdS semiconducting nanostructures prepared by microwave-assisted wet chemical route for supercapacitor application

Herein, we are reporting the enhanced electrochemical performance of hybridised WO3–CdS nanocomposites prepared by microwave assisted wet chemical route without post synthesis of heating for different wt% of CdS (2 wt%, 4 wt% and 6 wt%) loading with WO3. Then, the end products were characterized by various techniques to evaluate their structural and morphology, thermal, optical, and electrochemical properties. From the XRD analysis, the orthorhombic and monoclinic structure of WO3 and hexagonal phase of CdS were observed and the average crystalline size is calculated as ± 19 nm. The microscopic examination such as SEM images showed smooth and tiny particle and HRTEM images showed rod shape morphology in the as-prepared particle. The presence of W and Cd elements are confirmed by EDAX analysis. The existences of functional groups related to W and Cd are analyzed by FTIR investigation and confirmed the chemical bonding nature. Thermal (TGA/DTA) analysis showed that as-prepared structures are stable up to 450°C temperature. The electrochemical investigations have been carried out, and their enhanced specific capacitances were calculated as 44 F/g for pure WO3 (a) nanostructures and 48, 170, and 172 F/g correspondingly for the hybridised WO3–CdS (b, c, d) nanocomposites.

Photocatalytic Performance of Cubic and Hexagonal Phase CdS Synthesized via Different Cd Sources

CdS has been widely used in photocatalysis, by virtue of its sensitivity to visible-light irradiation. But CdS has two crystalline phases, which are not equally well understood. Hence, we synthesized cubic phase and hexagonal phase hierarchical CdS with different Cd sources by the hydrothermal method. These as-prepared CdS samples were characterized by powder x-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), ultraviolet–visible spectrophotometer (UV–Vis), and room temperature photoluminescence (PL). Photocatalytic degradation of methylene blue was evaluated under simulated visible-light irradiation. PXRD results revealed that the CdS samples manifested a cubic phase when the Cd source was CdCl2, but the CdS assumed a mixed hexagonal and cubic phase when the Cd source was Cd(NO3)2. FESEM results indicate that the morphologies of CdS are both flower-like structures. The optical energy band gap of cubic phase CdS is 2.26 eV, but mixed hexagonal and cubic phase CdS is 2.24 eV according to UV–Vis results. PL results show that CdS samples of both phases have a similar emission peak near 560 nm, which is consistent with UV–Vis absorption spectrums. In addition, mixed hexagonal and cubic phase CdS exhibits better photocatalytic activity than cubic phase CdS.

Doping effect investigation of Li-doped CdS thin films

ABSTRACTLi-doped CdS (CdS:Li) thin films with 0, 1, 2 and 3 wt-% Li concentrations were prepared by the spray technique using a perfume atomiser. The effect of Li doping concentration on the structural, optical, electrical and magnetic properties was systematically investigated and the results are reported in this paper. Analysis of the microstructure indicates that all the films consist of a hexagonal CdS phase with a strong (0 0 2) preferential growth texture. Nanoneedles were evinced from the SEM images of the doped films. Optical studies reveal that the transparency and band gap were dependent on Li-doping content. Hall effect measurements reveal that all the doped films exhibit p-type conductivity and the resistivity values strongly depend on the occupancy of Li atoms on the substitutional and interstitial sites of the CdS lattice. Room temperature ferromagnetism was observed for the doped films.

Fabrication of highly selective formaldehyde sensor through a novel spray deposited ZnO/CdS heterostructured interface: A surface charge enhancement approach

In the nanotechnology era, design and development of heterostructures are quiet often persuade exciting materials properties. These nanostructures have been investigated towards numerous applications including gas sensors over the years. In this background, we have solely investigated the charge transport properties, and role of photon interaction in the spray deposited ZnO/CdS heterostructure. Observed crystal structure of heterostructure revealed the formation of hexagonal wurtzite structure of ZnO and hexagonal phase of CdS respectively. Compositional analysis of deposited ZnO/CdS heterostructure showed the predominance of cadmium. Layered morphology of ZnO and CdS was observed with agglomerated nanograins on the surface. The exciton-phonon coupling strength of the heterostructure was found to be 0.2194. Heterostructure showed a fascinating figure of merits towards formaldehyde vapor at room temperature under photonic interaction. The lowest detection limit of formaldehyde was found to be 10 ppm. The response and recovery times for 10 ppm formaldehyde were 78 and 25 s respectively. Facile and low-cost heterostructure fabrication, high sensitive detection, long-term stability, faster response-recovery profile with better transient characteristics are the novel features of this work.

Synthesis, Formation Mechanism, and Magnetic Properties of Monodisperse Semiconducting Spinel CdCr2S4 Nanocrystals via a Facile “Seed-Mediated” Growth Method

The chalcogenide spinel CdCr2S4 is a well-established ferromagnetic semiconductor that exhibits unique properties and is a promising candidate for spintronic applications. With band gap in the visible wavelength region, CdCr2S4 nanocrystals offer the exciting possibility of tailoring both the optical and magnetic properties with precise morphology control. However, the synthesis of monodisperse CdCr2S4 nanocrystals is challenging and has not been reported. A unique “seed-mediated” growth process has been developed for the synthesis that involves using cubic-phase CdS, which has a face-centered cubic crystal structure similar to that of CdCr2S4, as a “seed” to react with CrCl3·6H2O in a solution mixture of 1-dodecanethiol and 1-octadecene. Remarkably, hexagonal-phase CdS is ineffective as a “seed” for formation of the desired product. A mechanism for formation of monodisperse CdCr2S4 nanocrystals by the selective growth process is proposed, and the structural and magnetic properties of the synthesized nanocrystals are presented. The novel synthetic strategy can be exploited for the controlled formation of other complex magnetic chalcogenides.

Growth and characterization of graphite doped CdTe/CdS thin film heterojunction

Doping is a notable factor to improve the performance of CdTe/CdS heterojunction solar cell. Graphite doped CdTe/CdS heterojunction on Si (1 1 1) substrate has systematically fabricated by thermal evaporator method under medium vacuum (10 -4 torr) condition. Characterization of doped CdTe/CdS film was carried out by various diagnostic techniques such as X-ray diffraction (XRD) exhibits the polycrystalline structure of cubic phase CdTe and hexagonal phase CdS, scanning electron microscopy (SEM) shows the smoothening of the film, energy dispersive X-ray (EDX) confirm the elemental composition found in the film and current-voltage (I-V) analysis suggests the diode like properties where the current is slightly increased by the doping of graphite into CdTe/CdS heterojunction compared to the reported literature. Analysis of I-V characteristics has been made to investigate the current conduction mechanism in CdTe/CdS heterojunction.

From CdS to Cu7 S4 Nanorods via a Cation Exchange Route and Their Applications: Environmental Pollution Removal, Photothermal Conversion and Light-Induced Water Evaporation

A detailed transformation process of cation exchange (CE) chemistry from hexagonal phase CdS to CdS-Cu7S4 core-shell heterostructures nanorods and eventually to monoclinic phase Cu7S4 nanorods is reported. Applications of the nanorods in environmental pollution removal, photothermal conversion and light-induced water evaporation were investigated. The influence of the reaction time, morphology, and crystal phase on the photocatalysis, photothermal conversion and light-induced water evaporation was discussed. The results showed maximum removal value of rhodamine B by 97.8% at 1 h timepoint. Aqueous dispersion of the core-shell CdS-Cu7S4 heterostructures nanorods prepared with 2 h (1.0 g/L) exhibited a good photothermal conversion performance as it saw increase in sample temperature by 37.8 oC in 300 s under the irradiation of 980 nm laser. The exposure of as-obtained sample film to simulated sunlight irradiation at 2 h (8 mg) increased the weight loss of pure water by 0.62 g in 30 min with the water evaporation efficiency up to 48.4%. We are reporting an excellent light-induced water evaporation performance potential of the nanorods discussed.

Nano-architecture based photoelectrochemical water oxidation efficiency enhancement by CdS photoanodes

In the present work, 2D nanostructuring has been utilized to impart an efficiency improvement to the hexagonal phase CdS films for the photoelectrochemical (PEC) cells those were deposited by spray pyrolysis technique. By controlling the aerosol droplet- size, population and impingement time during the spray pyrolysis deposition, various nano-features viz. randomly aligned nanorods, nanotubes and nanowires of CdS has been demonstrated for the first time. A growth mechanism has been proposed to predict the temporal evolution of the nanostructures. The prominent nanoscale structures show improved optical properties in the visible range of solar spectrum. The structural studies validate the morphological differences of nanostructures in terms of the texture coefficient analysis as well as 2D micro x-ray diffraction imaging. Electrochemical characterization is carried out to understand the effect of nanostructuring on the PEC performance of the CdS photoanodes in the sulphide (0.1 M Na2S + 0.02 M Na2SO3) electrolyte at applied bias of 0.2 V (versus SCE). The evolution of morphology from randomly aligned rods to nanowire is responsible for improved photocurrent (3.5 times). CdS film morphology can be tuned to nanotubes, nano- rose buds and nanorod bunches even by doping Zn2+ ions in CdS lattice. Nano-structuring of doped CdS has shown enhanced performance of the photoanodes. The nanotubes structures yielded highest photocurrent density of 1.6 mA cm−2. Whereas modifying the 2D-nanostructured CdS film by simple MoO3 spray coating yields the photocurrent enhancement to 2.1 mA cm−2.

Swift Heavy Ion Induced Functionality In Nanocrystalline CdS Thin Films: Role Of Growth Temperature

Influence of growth temperature on swift heavy ion (SHI) induced structural and optical functionality in CdS thin films is explored for photonic applications. Intense green emission is observed in nanocrystalline CdS thin films grown by pulsed laser deposition (PLD) at two different substrate temperatures (Ts): room temperature (RT) and 200 ºC. The role of Ts and its implications on the effect of dense electronic excitation provoked by swift heavy ion irradiation (SHII) on various optical and structural properties of CdS films is investigated under the influence of 70 MeV 58 Ni +6 ion beam. It reveals from the present studies that Ts may crucially affect the crystalline structure, vibrational and electronic states of the film and thereafter the functionality induced by ion beam. It is found that ion beam is capable to transform structural phase from mixed phase of cubic and hexagonal structure to either pure cubic or pure hexagonal phase of CdS depending upon the pre-existing preferred orientation in pristine film. The modification in crystallite size and band gap due to impact of ion beam is found to be strongly dependent on pre-existing structural phase, as determined by Ts. The studies presented here confirm that initial growth conditions play a key role even after post deposition SHII treatment in selecting precisely the functional behavior of the films.

Facile synthesis of cadmium sulphide-polyaniline (CdS-PANI) nanocomposite and its field emission investigations

A simple two step chemical route has been employed to synthesize cadmium sulphide - polyaniline (CdS-PANI) nanocomposite. In the first step PANI nanotubes are synthesized by oxidative polymerization followed by deposition of CdS nanoparticles on them. In order to investigate the structural, chemical and optical properties of the CdS-PANI nanocomposite, various characterization techniques have been used. The microscopic analysis reveals that the PANI nanotubes having length in several microns with cavity diameter of ~ 10 to 20 nm are decorated with CdS nanoparticles of 5 to 10 nm. The XRD spectrum indicates formation of crystalline hexagonal phase of CdS, supported by the SAED pattern obtained during TEM analysis. The FTIR and UV-visible spectra confirm formation of the conducting phase of PANI. The field emission studies of the CdS-PANI nanocomposite indicate low turn on field of 1.4 V/μm, corresponding to emission current density ~ 1 μA/cm2, and emission current density of ~ 5.5 mA/cm2 has been drawn at an applied field of 3.8 V/μm. Furthermore the emission current is observed to be fairly stable at the preset values over long term duration. The enhanced field emission properties, exhibited in terms of low turn on field, and delivery of very high emission current density at relatively lower applied field, are attributed to the nanometric dimensions of the PANI nanotubes and CdS nanoparticles, and modulation of electronic properties due to formation of heterojunction. The overall field emission results propose the CdS-PANI nanocomposite as a promising material for field emission based devices.

Synthesis and structural characterization of CdS nanoparticles using nitrogen adducts of mixed diisopropylthiourea and dithiolate derivatives of Cd(II) complexes

[Cd(diptu)2(ced)], [Cd(diptu)2(ced)(bpy)], [Cd(diptu)2(ced)(phen)], (where diptu=diisopropyl thiourea; ced=1-cyano-1-carboethoxylethylene-2,2′-dithiolate; bpy=2,2′-bipyridine and phen=1,10-phenanthroline) have been prepared and used as single source precursors for the preparation of hexadecylamine capped CdS nanoparticles. The precursor complexes were characterized by elemental analysis, FTIR and TGA. The structural properties of the nanoparticles were investigated using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy techniques (SEM). The optical properties of the nanoparticles were studied using UV–Visible and photoluminescence spectroscopy. The XRD analysis showed that the nanoparticles were indexed to the hexagonal phase of CdS and the TEM results showed CdS nanoparticles with average crystallite sizes of 4.00–8.80nm.

Preparation of highly photocatalytic active CdS/TiO2 nanocomposites by combining chemical bath deposition and microwave-assisted hydrothermal synthesis

CdS/TiO2 nanocomposites were prepared from Cd and Ti (1:1M ratio) using cetyltrimethylammonium bromide by a two-step chemical bath deposition (CBD) and microwave-assisted hydrothermal synthesis (MAHS) method. A series of nanocomposites with different morphologies and activities were prepared by varying the reaction time in the MAHS (2, 4, and 6h). The crystal structure, morphology, and surface physicochemical properties of the nanocomposites were characterized by X-ray diffraction, UV–visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption–desorption measurements. The results show that the CdS/TiO2 nanocomposites were composed of anatase TiO2 and hexagonal CdS phases with strong absorption in the visible region. The surface morphologies changed slightly with increasing microwave irradiation time, while the Brunauer–Emmett–Teller surface area increased remarkably. The photocatalytic degradation of methyl orange (MO) was investigated under UV light and simulated sunlight irradiation. The photocatalytic activity of the CdS/TiO2 (6h) composites prepared by the MAHS method was higher than those of CdS, P25, and other CdS/TiO2 nanocomposites. The CdS/TiO2 (6h) nanocomposites significantly affected the UV and microwave-assisted photocatalytic degradation of different dyes. To elucidate the photocatalytic reaction mechanism for the CdS/TiO2 nanocomposites, controlled experiments were performed by adding different radical scavengers.

Impact of in situ preparation of CdS filled PVP nano-composite

Cadmium sulfide nanoparticles filled polyvinyl pyrrolidone (PVP) were prepared by in situ wet chemical precipitation technique. X-ray diffraction (XRD), Fourier transforms infrared spectra (FTIR), transmission electron microscopy (TEM) and ultraviolet–visible (UV/Vis) were used to characterize the prepared nano-composites. Density Function Theory (DFT) was used to approve the complexation process. XRD results indicate appearance of two peaks at about 28.1°, 27.4° corresponds to (101) and (002) planes which suggest hexagonal phase of CdS with lattice constants of 4.14, 6.72Å in the polymeric matrix. UV/Vis spectra reveal that nano-composite films show quantum confinement effect. The absorption showed a shift toward the shorter wavelength (blue shift) with decrease in the concentration of Cd+ ions. Optical band gap and particle size were calculated and is in agreement with the results obtained from TEM data. Transmission electron microscopy shows that the prepared CdS nanoparticles were dispersed and nearly uniform in diameter within the polymeric matrix.

The Synthesis and Characterization of Novel Cadmium Sulphide Nanocrystallites and their Thin Films

Diethyl dithiocarbamate [Cd (S2CN Et2)2] complex is used to deposit the cadmium sulphide thin film at much lower temperature by Aerosol Assisted Chemical Vapour deposition (AACVD) and same precursor is used to synthesize the nanocrystals in Oleylamine at elevated temperature. Thermogravimetric analysis shows that precursor [Cd (S2CN Et2)2] decomposes in the single stage, losing 62% of total weight. Deposition of thin films at 300 °C and 400 °C showed the growth of CdS clusters which were made of granular crystallites. These results are confirmed by SEM analysis. Thermolysis of the precursor in oleylamine at 240 °C gave the nanoparticles most of them are monodispersed spherical shape, few having mono and dipod structures. TEM images confirm the structures. XRD results show the thin films and nanoparticles have hexagonal phase of CdS.

Synthesis of multi-podal CdS nanostructures using heterocyclic dithiocarbamato complexes as precursors

Bis(dipiperidinyldithiocarbamato)cadmium(II) (1) and bis(ditetrahydroquinolinyldithio-carbamato)cadmium(II) (2) were used as precursors for the synthesis of oleylamine (OA), decylamine (DA) and dodecylamine (DDA) capped CdS nanoparticles. The optical properties of these particles have been studied. The absorption spectra for the amine capped CdS particles are blue shifted in relation to the bulk material. The corresponding photoluminescence spectra show a narrow band edge emission. High quality crystalline CdS particles of different shapes, ranging from short nanorods and elongated nanorods (rods, bipods, tripods and tetrapods) to nanocubes were obtained when the reaction temperature was varied between 180 and 270°C. A decrease in the length of the rods and bipodal nanoparticles was observed with an increase in the length of the chain of the amine (capping agent) used. The p-XRD patterns revealed the hexagonal phase of CdS to be dominant in all the samples. Infra-red studies suggest that the mode of bonding of the amines (oleylamine, decylamine and dodecylamine) on the CdS nanoparticle surfaces is through electron donation from the nitrogen atoms.

Crystal structure-selective formation and carrier dynamics of type-II CdS–Cu31S16 heterodimers

Anisotropically phase-segregated CdS–Cu31S16 heterodimers with type-II band alignment were spontaneously formed by selective growth of monoclinic Cu31S16 phases on preformed hexagonal CdS phases. The photo-induced carrier dynamics of the heterodimer was investigated by fluorescence and transient absorption measurements.