Structure Of CdS Research Articles

Tailoring the CdS surface structure for photocatalytic applications

Semiconductor mediated photocatalysis is envisaged as a promising approach to initiate the diverse redox reactions under the ambient conditions. Although titania still remains as benchmark photocatalyst, its wide band gap and rapid charge carrier recombination blights their utility under natural solar light. Thus, search of functional materials with narrow gap and suitable band edge potentials has drawn significant attention for photocatalytic applications. Towards this end, CdS have been impressive as prime nanomaterial which is mainly attributed to their visible light absorption capacity, more negative conduction band edge potential, and simplistic preparation with diverse morphologies and their proficiency to form stable heterostructure with variety of co-catalysts. However, photocorrosion vulnerability of CdS becomes the origin of intimidation for long term operations and massive charge carrier recombination constrains their performance. In this review article, surface structure of the CdS modified with various co-catalysts such as metal NPs, metal oxides, sulfides, phosphides, carbides, g-C3N4, polymers and carbon materials to overcome the aforementioned drawbacks is discussed. Besides, fundamental aspects concerning the relationship between the crystal structure and morphological effects of CdS on the photocatalytic property is emphasized. The preparative methods, charge carrier dynamics and performance of CdS-based binary and ternary composites benefitting the model reactions such as pollutant degradation, hydrogen evolution and organic functional group transformation is reviewed in detail. The literature survey concludes that the surface modifications with co-catalysts can be the constructive approach for exploring the CdS based nanomaterials for broader environmental applications.

Band structure and enhanced photocatalytic degradation performance of Mg-doped CdS nanorods

Abstracts In this paper, Mg-doped CdS nanorods (MgCdS) were prepared by a simple solvothermal method to investigate the band structure and enhanced photocatalytic degradation performance under visible light illumination. Mg element is successfully doped into the lattice of CdS and it doesn't destroy the nanorod structure of CdS. The band gap of CdS is widened by Mg doping. The prepared MgCdS shows improved photocatalytic degradation performance than CdS, and 5% MgCdS has the optimal photocatalytic degradation performance, which can degrade approximately 96% RhB in 70-min visible light illumination. The enhanced photocatalytic degradation performance of 5% MgCdS is due to the increased photogenerated charge carrier concentration and the effectively suppressed recombination of photogenerated carriers.

Influence of transition metals (Sc, Ti, V, Cr, and Mn) doping on magnetism of CdSProject supported by the National Natural Science Foundation of China (Grant No. 11664023) and the HongLiu First-class Disciplines Development Program of Lanzhou University of Technology and State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals of China.

The influence of transition metals (Sc, Ti, V, Cr, and Mn) doping at different distances on the magnetism of CdS is studied by using generalized gradient approximation combined with Hubbard U in the VASP package. The results show that the doping systems are more stable, easy to form, and the wurtzite structure of CdS is not changed. It is found that the systems are antiferromagnetic (AFM) when nearest neighbor doping, which is attributed to the direct charge transfers between two impurity ions. The systems are ferromagnetic (FM) when the doping distance increases further, since the double exchange interactions are observed among the 3d orbital of the transition metal, the Cd-5s and the S-3p orbitals are at conduction band minimum. We also found that the total magnetic moment of each ferromagnetic system increases with the order of SC to Mn-doping, the spin polarizability of Cr-doping system is 100%. The estimated Curie temperature indicates that the Cr- and Mn-doped CdS in this paper can achieve room-temperature ferromagnetic characteristics, especially the Cr doping is the most prominent. And TM-doping does not destroy the semiconductor characteristics of the system. Therefore, the TM-doped CdS can be used as an ideal dilute magnetic semiconductor functional material.

EFFECT OF Ce DOPING ON THE CHARACTERISTIC PROPERTIES OF CdS NANOPARTICLES

In our present study, Ce doped CdS nanoparticles were synthesized in room temperature environment by using chemical co-precipitation technique which is cheap in cost. Ce doped CdS nanoparticles ( average particle size: 3.7 nm) were found to have cubic structure as a result of XRD measurements. It has also been clearly observed that Ce dopant ions do not alter the structure of the host semiconductor CdS. Using the spectrum obtained as a result of UV-Vis measurement, the energy band gap of Ce doped CdS nanoparticles was determined as 2.73 eV. This value was observed to be higher than the energy band gap of bulk CdS (2.42 eV). Thus, it can be said that this change in the energy band gap is due to the quantum confinement effect. The maximum IPCE value was 27% for Ce doped CdS nanoparticles while the IPCE values was 4% for pure CdS nanoparticles, respectively. The IPCE of the solar cells improves with the Ce dopant ion. Moreover, the spectral response range of Ce doped CdS nanoparticles widens with the Ce dopant ion. This is attributed to the long lifetimes of the Ce3+ excited states that facilities the transfer of the charge carries to the photoelectrode.

Investigation of electrochemical supercapacitor performance of WO3-CdS nanocomposites in 1 M H2SO4 electrolyte prepared by microwave-assisted method

In this work, we have prepared WO3-CdS nanocomposites for supercapacitor electrode by Microwave-Assisted Method. The orthorhombic and monoclinic mixed structure of WO3 and hexagonal structure of CdS was observed by XRD pattern. The FESEM micrograph showed the irregular particle shape and HRTEM images demonstrated the small rod shape morphology with irregularity. The EDAX analysis confirmed the presence of W and Cd elements. From the electrochemical analysis, we have calculated the maximum capacitance as 650 F/g for WO3-CdS (6 wt%) electrode. The long cycle test showed 133% of capacitance retention with 100% Coulombic efficiency.

Effect of preparation on opto-electrical properties of CdS /N, S-rGO photocatalyst for splitting of water by visible light

CdS supported on N, S-rGO photocatalysts were prepared successfully by a hydrothermal and a gas-solid reaction method. Catalysts made by the gas-solid reaction method was found to be more active. XRD, Raman spectroscopy, XPS, UV-DRS, PL and Electrical impedance spectroscopy were used to characterize the prepared catalyst. Present study reveals that catalysts synthesized by the gas-solid reaction at higher temperature had a close-packed hexagonal structure of CdS and also a chemical interaction between CdS and N, S-rGO. The interaction results into development of heterojunction between CdS and NS-rGO. Such interaction was absent in those catalysts which were prepared by the hydrothermal technique. Heterojunction prevents the recombination of photogenerated electrons and holes resulting in the higher rate of hydrogen production. XPS studies show the atomic % N is higher in the catalyst which was prepared by the gas-solid reaction. Electrochemical impedance studies reveal that interfacial charge transfer resistance of CdS/NS-rGO (prepared by the gas-solid reaction) is 6 times lower compared to a catalyst prepared by the hydrothermal method. Flat band potentials, calculated by analysis of Mott. Schottky data reflect that catalysts synthesized by the gas-solid reaction have higher negative values of flat band potential compared to those of hydrothermal synthesis. More negative conduction band edge potential has been observed for CdS supported on the surface of N, S-rGO prepared by the gas-solid reaction which results in an increase in the rate of reduction of H2O/H2. Defects density, as measured by the Raman spectroscopy, is observed to correlate with activity.

Effect of transition metals (Sc, Ti, V, Cr and Mn) doping on electronic structure and optical properties of CdS

The influences of transition metals (Sc, Ti, V, Cr and Mn) doping at different distances on the stability, electronic structure, conductivity and optical properties of CdS are studied by using VASP code. The results show that the Cr-doped CdS is easy to form, followed by V, Ti, Sc and Mn. The next nearest-neighbor doping is the most stable in each transition metal-doped system. The band-gaps gradually decrease with the order of Sc, Ti, V, Cr, Mn-doping, all doped systems become the degenerate semiconductor. Doping not only enhances conductivity, but also improves photocatalytic performance, especially Mn-doped CdS has obvious improvement. The absorption intensity in the visible light range of the single-doping is more than that of two atoms doped system in different distances, of which Mn and Cr single-doping are the most prominent.

Datos del estudio de películas delgadas de CdS:Al crecidas por el método de deposición de baño químico después del envejecido

Este artículo presenta los datos del estudio de las propiedades estructurales, ópticas y vibracional de películas delgadas de CdS:Al sintetizadas por el método de deposición de baño químico (DBQ) después del envejecido. Las muestras fueron caracterizadas por difracción de rayos X, espectroscopia UV-visible y fotoluminiscencia, y espectroscopia Raman. El patrón de difracción de rayos X de las muestras presenta una estructura cristalina hexagonal de CdS. El tamaño del cristalito fue estimado para cada película delgada. La brecha de banda de energía fue calculada empleando el método de Tau. Las muestras presentan defectos en su estructura. Un estudio detallado sobre la estructura fue llevado a cabo en el rango de 200 a 800 cm–1, donde los modos vibracionales 1LO y 2LO están presentes. Los datos no han sido reportados o discutidos por ahora.

Hollow structured PtNix alloy as cocatalyst of CdS for hydrogen generation under visible light irradiation

PtNix hollow nanoparticles (HNPs) as a cocatalyst was synthesized by a galvanic replacement method at room temperature, and then was loaded on CdS. The hollow structure of PtNix alloy was confirmed by TEM and STEM. Photocatalytic hydrogen production reaction was performed for PtNix/CdS catalyst under 300 W Xe lamp (λ ≥ 420 nm). It is noteworthy that PtNi0.5/CdS shows the highest hydrogen evolution activity of 2.9 mmol/h with QE = 51.24% at 420 nm, which is higher than that of situ-photodeposited Pt onto CdS (0.57 mmol/h). The enhancement of hydrogen evolution performance of PtNi0.5/CdS could be attributed to the porous shell and hollow structure of PtNi0.5 NPs, as well as the strong electronic coupling effect between Pt and Ni. Besides, the sheet structure of CdS in some degree promoted the hydrogen production rate. Therefore, the PtNix HNPs could be a promising cocatalyst of CdS for solar driven hydrogen evolution.

The staggered heterojunction of CeO2/CdS nanocomposite for enhanced photocatalytic activity

To modify the photocatalytic activity of CeO2, CdS nanoparticles was composited with CeO2 through a homogeneous precipitation method. The crystal structure, composition, morphology, and optical properties of CdS/CeO2 composite were analyzed in detail. The results found that CdS/CeO2 composite consisted of the cubic fluorite structure of CeO2 and wurtzite hexagonal structure of CdS. Meanwhile, TEM magnification of CdS/CeO2 composite exhibited clear lattice fringe corresponding to [hkl] plane of CeO2 and CdS. UV–visible absorption spectra showed that CdS extended the adsorption edge of the CdS/CeO2 composite to longer visible region, which related to the decrease of band gap. The coexistence of staggered type II band alignment in the CdS/CeO2 composite facilitated the charge separation of visible–excited electrons and holes, thereby decreasing the recombination and improving the efficient photocatalytic activity for methylene blue dye degradation, with the apparent rate constant (0.0102 min−1) which is about 7 times higher than that of pure CeO2 (k = 0.0014 min−1).

Structure and Optical Properties of CdTe and CdS Thin Films after Hard Ultraviolet Irradiation

The influence of hard ultraviolet radiation on the crystalline structure, surface morphology and optical characteristics of CdS and CdTe semiconductor layers obtained by direct current magnetron sputtering are investigated. It was established that the optical characteristics of the studied films CdS and CdTe are insensitive to hard ultraviolet irradiation. The crystalline structure of the CdS and CdTe layers is changed after irradiation. The period of the lattice for cadmium sulfide films increases from c = 6.77(01) Å to c = 6.78(88) Å, which may be due to the formation of point defects and defective complexes. Decrease the integral FWHM of the peaks on the X-ray diffraction patterns of the layers of CdS and CdTe was observed, due to the increase of the coherent scattering regions as a result in the process of near-surface layers partial recrystallization of the investigated films.

High-efficiency visible light photocatalytic performances of the CdS(HS)/g-C3N4 composites: the role of intimate connection and hollow structure

The CdS(HS)/g-C3N4 photocatalysts with an intimate connection was successfully synthesized by a facile deposition method. The CdS hollow microspheres (CdS(HS)) were well anchored on the surface of g-C3N4 to form an intimate connection by the hydrogen bonding between g-C3N4 and CdS(HS). The structures, morphologies, optical and electrical properties and photocatalytic performance of samples were successfully characterized by multiple means. The CdS(HS)/g-C3N4 composites exhibited excellent photocatalytic activity and stability for the photodegradation of RhB, and the degradation rate constant of CdS(HS)/g-C3N4 with optimum CdS(HS) mass ratio of 0.25% was about 2.1 times higher than that of the pure g-C3N4 under the visible light irradiation for 20 min. After four cycles, the CdS(HS)(0.25%)/g-C3N4 composite still maintained the high photocatalytic activity with the RhB degradation efficiency of 95%. Surprisingly, the photocorrosion of CdS(HS) caused by the photogenerated holes was inhibited effectively. The improvement of these properties should be ascribed to the intimate connection between g-C3N4 and CdS(HS) and the hollow structure of CdS(HS). The photocatalytic mechanism was also analyzed systematically. Furthermore, it was of great interest that the CdS(HS)/g-C3N4 composites possessed an excellent sedimentation property and they can be easily separated from the solution, which will be propitious to practical application.

Synthesis of sea urchin-like microsphere of CdS and its gas sensing properties

In this article, sea urchin-like microspheres of CdS (NUM-CdS) assembled by nano-needles were successfully synthesized with ethylenediamine as a complexing agent through a simple solvothermal process. Herein, the structures of NUM-CdS samples were selectively controlled by optimizing the concentration of thiourea. Various techniques were employed to explore the morphology, microstructure and specific surface area of the materials, including XRD, FTIR, SEM, TEM, and BET. Hierarchical sea urchin-like microspheres were composed by numerous nano-needles with a diameter of ∼15 nm. The gas sensing properties of NUM-CdS samples were systematically measured. The response of NUM-CdS-3 was ∼21–100 ppm ethanol, which was 7 times higher than that of NUM-CdS-6 at 230 °C. Meanwhile, the rapid response and recovery characteristics (∼1 s) were observed because of the hierarchical structure and catalytic actions of CdS.

Photocatalytic CO2 reduction activity of Z-scheme CdS/CdWO4 catalysts constructed by surface charge directed selective deposition of CdS

Rational construction of Z-scheme photocatalysts and deep exploration of Z-scheme transfer mechanism are highly desirable for improving the activity of CO2 reduction photocatalysts but remains a significant challenge. Herein, we synthesized a series of heterostructured CdS/CdWO4 materials by selectively depositing CdS nanoparticles on the edges of CdWO4 nanoplates. Selective deposition mechanism of CdS and the formation of the composites were studied in detail. The photocatalytic CO2 reduction activities of the synthesized materials were investigated and the results show that CdS/CdWO4 materials exhibit higher photocatalytic activity than pure CdS and CdWO4. We suggest that the enhanced photoreduction CO2 activity is attributed to Z-scheme charge transfer mechanism based on the analyses of the products of CO2 reduction and the band structure of CdS and CdWO4. Kelvin probe force microscope on CdWO4 nanoplates shows that the photogenerated electrons, driven by electric field forces, would migrate to the edge of CdWO4. The charge transfer direction, coupling with the selective deposition of CdS nanoparticles, facilitates CdS/CdWO4 composites following Z-scheme transfer. In-situ Pt photodeposition tests provide strong experimental support to the charge transfer mechanism. The results gained herein are expected to provide some useful insights into the structure-oriented rational design of Z-scheme photocatalysts for CO2 reduction.

One‐Step Solid‐Phase Synthesis of 2D Ultrathin CdS Nanosheets for Enhanced Visible‐Light Photocatalytic Hydrogen Evolution

Photocatalysts with 2D ultrathin nanosheet structures are gradually attracting significant interest from researchers because of their excellent photoelectric and physicochemical properties. However, the efficient fabrication of 2D CdS nanosheets with high crystallinity and ultrathin thickness still faces huge challenges. In this work, 2D ultrathin CdS nanosheets are synthesized through a simple one‐step solid‐phase strategy using CdSO4 · 8/3H2O as precursors in the CH4N2S atmosphere. The 2D ultrathin CdS nanosheet obtained by calcining at 300 °C for 4 h shows superior photocatalytic activity: the photocatalytic rate of hydrogen generation reaches 149.67 μmol h−1, and the corresponding apparent quantum efficiency is 36.7% at 450 nm. The enhanced photocatalytic activity and excellent photocatalytic stability are realized through the high crystallinity and ultrathin 2D nanosheet structure of CdS, which provide a high surface‐to‐volume ratio and enriched active adsorption sites. The 2D ultrathin nanosheet structure prevents the surface sulfide ions from being oxidized because of the extremely short interface distances and photocatalytic carrier transport, resulting in effective photocorrosion inhibition. Controlled experiments also show that the precursors ZnSO4 · 7H2O and Cd(Ac)2 · 2H2O are converted to 2D ZnS and CdS nanosheets through the one‐step solid‐phase method, illustrating that this simple one‐step solid‐phase strategy can be extended to the fabrication of other metal sulfide photocatalysts with 2D nanostructures.

Hydrophilic Doped Quantum Dots “Ink” and Their Inkjet‐Printed Patterns for Dual Mode Anticounterfeiting by Reversible Cation Exchange Mechanism

AbstractLuminescent quantum dots (QDs) patterns have attracted great attention in anticounterfeiting applications because they can emit fluorescence upon excitation. Here, different from traditional luminescent patterns for anticounterfeiting purposes, a novel strategy based on the reversible cation exchange enabled Ag doped CdS quantum dots (CdS:Ag QDs) is reported to provide a higher security for anticounterfeiting. First, the reversibility of cation exchange enabled doped QDs crystal engineering have been revealed. The switch from nonluminescence to luminescence for several cycles by such a mechanism has been achieved. Second, the hydrophilic doped QDs “ink” can be prepared by surface modification, and then flexible bulk‐sized patterns can be printed on different substrates by inkjet printing technology, such as the parchment paper, PET foil, and paper currency substrates. Third, owing to the characteristic of stable crystal structure of CdS:Ag QDs, the patterns of such doped QDs on substrates can be switched by in situ cation exchange to achieve conversion of the disappearance and recovery of luminescent signals, from which a multiple dual mode anticounterfeiting verification can be provided.

CdS Photocatalysts Modified with Ag: Effect of the Solvothermal Temperature on the Structure and Photoactivity for Hydrogen Production

This work studies the effect of the temperature in the solvothermal synthesis of CdS modified with Ag (Ag-CdS) over both the structure of CdS and the chemical state of the Ag species. The increase in the solvothermal temperature produces the evolution of the CdS nanostructures from nanoparticles of low crystallinity in coexistence with small nanocrystals with strong confinement effect to the formation of highly crystalline nanorods. The Ag species also change with the solvothermal temperature from Ag2S species, formed at low temperature, to metallic species as the temperature increases. The photoactivity of the Ag-CdS samples is the result of the combination of three factors: crystallinity of the CdS structures, existence of small nanocrystals with strong confinement effect and the presence of segregated Ag2S species. The Ag-CdS sample prepared at 120 °C shows the better efficiency for hydrogen production because it achieves the better combination of the aforementioned factors.

Dual-Color Lasing Lines from EMPs in Diluted Magnetic Semiconductor CdS:NiI Structure.

Have one ever seen a semiconductor that can issue two-color lasing lines? The diluted magnetic semiconductor (DMS) can do this. Here, we have observed dual lasing lines of 530 nm and 789 nm from a DMS structure of CdS:NiI, in which the excitonic magnetic polaron (EMP) and localized excitonic magnetic polaron (LEMP) are excitations out of ferromagnetic (NiS)x nanocluster and NiI2 nanoclusters within CdS lattice; both of them could lead to the collective EMP state at high excitation and therein produce coherent emission lines simultaneously. This occurrence is due to the superposition of EMP near CdS bandedge and the combination of the charge-transfer band of (NiI)n cluster with the LEMP within CdS lattice by overcoming the strong electron correlation of NiI cluster in a DMS structure, evidenced also by ab initio calculation. This finding opens a way to understand the collective behaviour of spin-coupled excitons in DMS and to find novel applications in the spin-related quantum technology.

Ultrathin CdS shell-sensitized hollow S-doped CeO2 spheres for efficient visible-light photocatalysis

By virtue of the systematic effects of S-doping on CeO2 and the ultrathin shell structure of CdS, the CeO2−xSx@CdS nanocomposite exhibits excellent photocatalytic activity under visible-light illumination for both H2 evolution (rate up to 1147.2 μmol g−1 h−1) and RhB degradation (efficiency reached 99.8%) as compared to CeO2, CeO2−xSx, and CdS.

Structural, vibrational, optical, morphological and compositional properties of CdS films prepared by a low-cost electrochemical technique

Very dense and uniform thin films of CdS were deposited on fluorine-doped tin oxide (FTO) substrates for thin film semiconductor devices application, such as in solar cells. The simplified electrochemical deposition method applied uses two-electrode system with FTO as the working electrode and high-purity graphite rod as the counter electrode. The CdS films grown at different cathodic voltages (1500 mV, 1550 mV and 1600 mV) were characterized for their structural, vibrational, optical, morphological and chemical compositional properties using state-of-the-art glancing incidence X-ray diffraction (GIXRD), Raman spectroscopy, UV–Visible spectrophotometry, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) respectively. XRD results reveal the existence of pure hexagonal crystal structure of CdS in the films in both as-grown and heat-treated conditions. The size of crystallites are in the range of (9–14) nm and (11–17) nm while the size of grains in these highly uniform and dense films are in the range (180–860) nm and (270–880) nm before and after annealing respectively. Raman results show the typical fingerprint of CdS in the form of the 1LO and 2LO phonon vibration peaks. The energy bandgaps obtained from optical measurements fall in the range of (2.50–2.59) eV which narrow down to 2.42 eV after annealing, for the different growth voltages used. EDX reveals all the films to be S-rich, with Cd/S ratio of ∼0.9 after annealing.