CdS Structures Research Articles

Anodized TiO2 Nanotubes Sensitized with Selenium Doped CdS Nanoparticles for Solar Water Splitting

In this research, TiO2 nanotubes (NTs) were produced by electrochemical anodization of a Ti substrate where different NH4F wt.% in the electrolyte was added. NTs with diameter of 65–90 nm and 3.3–4.9 µm length were obtained and sensitized with binary cadmium chalcogenides nanoparticles, CdS and CdSe, by successive ionic layer adsorption and reaction method (SILAR). Additionally, both anions S and Se were deposited onto Cd, labeled as CdSSe and CdSeS, to evaluate the effect of the deposition order of the anion from the precursor solution to form cadmium chalcogenides. The structural, optical, and electrochemical performance were analyzed through the SEM, XRD, XPS, UV-VIS, lineal voltammetry and chronoamperometry characterizations. The increase of NH4F wt.% from 1.5% to 4.5% produced a decrement of the diameter and length attributed to the fluoride ions concentration causing solubility of the NTs. XRD confirmed the TiO2 anatase and hexagonal CdS structures. From the EDS and XPS results, the presence of small amount of Se in the sensitized samples demonstrated the doping effect of Se instead of forming ternary semiconductor. With the sensitization of the TiO2 NTs with the nanoparticles, an improved hydrogen generation was observed (reaching 1.068 mL h−1 cm−2) in the sample with CdSSe. The improvement was associated to a synergetic effect in the light absorption and higher cadmium chalcogenide amount deposited when sulfur ions were deposited before selenium.

CdS structures prepared in AAO nanochannels via different synthesis methods under limited conditions

CdS is mainly prepared in nonlimited condition, inspired by the potential application of biomimetic nanochannels, we used AAO template as the limited condition to synthesize CdS structures via different synthesis methods for new application.

Monomeric and dimeric cadmium(II) complexes of S-alkyl/aryl dithiocarbazate as single-source precursors for cadmium sulfide nanoparticles: An experimental, theoretical interpretation in the stability of precursor and visible light dye degradation study

The reaction of S-alkyl/aryl dithiocarbazate functionalized with 2-acetyl pyridine ligands and cadmium chloride in ethanol leads to the formation of a mono nuclear cadmium(II) complex, [Cd(L1)2] (SP1), (HL1 is S-methyl-2-(1-(pyridine-2-yl)ethylidene)hydrazine-1-carbodithioate) and a dinuclear dichloro bridged complex, [(L2)Cd(μ-Cl)2Cd(L2)] (SP2), (L2 is S-benzyl-2-(1-(pyridine-2-yl)ethylidene)hydrazine-1-carbodithioate). The complexes are characterized by FTIR, single X-ray crystallography and thermogravimetry analysis. Density functional calculations indicate that different coordination patterns of the complexes with HL1 and HL2 ligands relate with the available space of the dissociation of CdCl2 in their solutions. Thermochemical destruction of the precursor complexes at the molecular level fabricated hexagonal CdS nanoparticles where the morphology is guided by the precursor. In situ generated thiols e.g., CH3SH in case of SP1, and PhCH2SH in case of SP2, internally stabilized the flower-like and rod shaped CdS structures, respectively. The synthesized nanoparticles were characterized by powder X-ray diffraction (XRD), scanning electronic microscope (SEM) and energy-dispersive X-ray spectroscopy (EDAX). The UV–Vis spectroscopic study shows a prominent quantum confinement effect in CdS with a band gap energy of 2.4 eV and 2.5 eV for SP1 and SP2, respectively. The CdS nanocrystals under investigation degrade Rose Bengal (RB) dye (96%) under visible light irradiation. A reusability study shows that the CdC nanoparticles retain their catalytic activity (86%).

Improved optical and structural properties of cadmium sulfide nanostructures for optoelectronic applications

In this study, the effect of ZnO seed layer on the growth of uniform CdS nanostructures was investigated using chemical bath deposition technique. Besides, the influence of molar concentration of reagents on the surface morphology, structural and optoelectrical properties of the deposited CdS thin films were examined. The CdS nanostructures were grown on bare glass and ZnO/glass substrates with different reagent molar concentrations. The results indicated an improvement in the homogeneity and uniformity of the grown CdS nanostructures on ZnO seed layer which can be due to the low lattice mismatch between ZnO and CdS structures. The CdS/ZnO samples were optimized by changing the molar concentration of reagents. A three–dimensional intersecting vertical nanosheet morphology with hexagonal structure was obtained when modified chemical concentration of 0.5 M was applied. The XRD pattern of CdS nanosheets indicated the hexagonal phase of CdS which were strongly orientated along (002) plane. The elevated intensity of dominant peak related to this sample confirmed the improved crystal quality of this CdS nanostructure comparing to the other samples. The UV–Vis spectrum demonstrated a high absorption coefficient for CdS intersecting nanosheets which might be due to the high specific surface area and light trapping behavior of this sample. The photoluminescence study also showed an improvement in optical properties of optimized CdS nanostructures. In order to study the optoelectrical properties of CdS nanostructures, metal–semiconductor–metal photodetectors were fabricated with different CdS samples and their current–voltage characteristics were analyzed. The results indicated an enhancement in photosensitivity, responsivity, and speed of photodetectors based on optimized CdS nanostructures.

Core/Shell CdSe/CdS Bone‐Shaped Nanocrystals with a Thick and Anisotropic Shell as Optical Emitters

AbstractColloidal core/shell nanocrystals are key materials for optoelectronics, enabling control over essential properties via precise engineering of the shape, thickness, and crystal structure of their shell. Here, the growth protocol for CdS branched nanocrystals is applied on CdSe nanoplatelet seeds and bone‐shaped heterostructures are obtained with a highly anisotropic shell. Surprisingly, the nanoplatelets withstand the high growth temperature of 350 °C and structures with a CdSe nanoplatelet core that is overcoated by a shell of cubic CdS are obtained, on top of which tetrahedral CdS structures with hexagonal lattice are formed. These complex core/shell nanocrystals show a band‐edge emission around 657 nm with a photoluminescence quantum yield of ≈42% in solution, which is also retained in thin films. Interestingly, the nanocrystals manifest simultaneous red and green emission and the relatively long wavelength of the green emission indicates charge recombination at the cubic/hexagonal interface of the CdS shell. The nanocrystal films show amplified spontaneous emission, random lasing, and distributed feedback lasing when the material is deposited on suitable gratings. This work stimulates the design and fabrication of more exotic core/shell heterostructures where charge carrier delocalization, dipole moment, and other optical and electrical properties can be engineered.

Effect of electrolytes on photoelectrochemical performance of a CuS–CdS heterojunction

CdS–CuS heterojunction films have been grown successfully on a copper substrate using a chemical bath deposition (CBD) method. The obtained films are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical absorption, Raman spectroscopy and photoluminescence (PL) analysis and the photo-electrochemical (PEC) properties of the CdS–CuS heterojunction have been studied using different electrolytes. The XRD pattern of CuS–CdS shows peaks corresponding to CuS (hexagonal) and CdS (cubic) structures, while the optical absorption studies revealed the presence of an absorption edge corresponding to CuS–CdS (band gap of 1.85 eV). The Raman spectra of the CuS, CdS and CuS–CdS heterojunctions were recorded and are in good agreement with the results reported in the literature. TEM and cross-sectional SEM images show an overlap between CuS rods and CdS flasks. The charge transfer across the layers was studied by using PL spectra. The measurement of the photo-electrochemical properties using a conventional two electrode system for an iodine electrolyte showed the highest conversion efficiency of 1.40% as against for potassium ferro–ferricyanide (0.38%) and polysulphide electrolytes (0.02%).

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.

Synthesis, growth mechanism and photocatalytic property of CdS with different kinds of surfactants

CdS is a well-known visible-light-sensitive semiconductor and has been widely used in photocatalysis. In order to improve the photocatalytic of CdS, CdS structures with different kinds of surfactants were synthesized by hydrothermal method.

Organic-free synthesis of porous CdS sheets with controlled windows size on bacterial cellulose for photocatalytic degradation and H2 production

Herein, a series of two-dimensional porous CdS sheets supported on bacterial cellulose (BC@CdS) were facilely synthesized through a biotemplate method without using any organic capping agent. Based on the unique 2D porous structure of BC@CdS, visible-light-driven H2 production activity was enhanced by ∼3.5 times compared with pure CdS nanoparticles. Furthermore, the “connecting windows” sizes of BC@CdS sheets were successfully controlled by adjusting the coating time. Our results demonstrate that the connecting window sizes play important role in photocatalytic degradation of methyl orange. To our best knowledge, it is the first time to use BC as a “scaffold” for the controlled growth of 2D porous CdS structures. It is hoped that our current work could widen the strategies for further synthesis of surface-clean 2D materials with controlled porous structures.

Low Threshold Room Temperature Amplified Spontaneous Emission in 0D, 1D and 2D Quantum Confined Systems

We address optical amplification properties of quantum nanoparticles of the cadmium selenide/cadmium sulfide (CdSe/CdS) material system with different dimensionality of spatial confinement. CdSe/CdS core/shell quantum dots (QDs), core/shell quantum rods (QRs) and 5 monolayer thick core/crown nanoplatelets (NPLs) at ambient temperature are considered, exhibiting 0D, 1D and 2D spatial confinement dimensionality of the electronic system, respectively. Continuous films of all these nanoparticles are synthesised, and amplified spontaneous emission (ASE) spectra are measured under femtosecond pumping at wavelengths of 400 nm and 800 nm, respectively. The lowest threshold is found for NPLs and the highest for QDs, demonstrating the influence of the rod-like and plate-like CdS structures. To emphasize this effect, ASE is demonstrated also in CdSe/CdS QRs and NPLs under nanosecond pumping at 355 nm in the same material films. The amplification has been achieved without use of any feedback structure, emphazising the efficiency of the antenna effect. The pumping threshold fluences for NPLs and QRs are observed to be similar, but no ASE is observed in QDs up to the damage threshold of the nanoparticle layers. The length variation investigation with nanosecond pumping resulted in the gain coefficients of 29 cm−1 and 37 cm−1 for QRs and NPLs, respectively.

Decoration of wide bandgap semiconducting materials for enhancing photoelectrochemical efficiency of PEC systems.

The production of photoanodes based on wide-band gap materials such as TiO2 is economically viable because of the low cost of synthesis methods. Contrary to economic aspects, wide-band gap semiconductor materials have a significant disadvantage due to low sensitivity to photons of visible light. To increase the photoactive parameters of the material of the electrodes in the visible range, the methods for decorating nanomasses of titanium dioxide by narrow-gap semiconductors are used. One of the most suitable narrow-gap semiconductor materials are CdS and Fe2O3. Controlled deposition of such materials on wide-gap semiconductors allows to regulate both the diffusion time of charge carriers and the band structure of TiO2/Fe2O3 and TiO2/CdS composites. The dimensions of the structure of the photoelectrode material of the cell have a large influence on the characteristics of the photocatalyst created. Thus, in the hematite structures of nanometre dimension, the rate of recombination of charge carriers fades away in comparison with bulk structures. Reducing the size of CdS structures also positively affects the nature of the photocatalytic reaction.

Effective shuttling of photoexcitons on CdS/NiO core/shell photocatalysts for enhanced photocatalytic hydrogen production

Hierarchical structure of NiO immobilized on CdS photocatalyst (CdS/NiO) was synthesized for stable and efficient H2 production. The catalyst is designed to suppress the photo-corrosion behaviour without affecting catalytic activity of CdS structures having tamarind leaf-like morphology is protected by fabricating thin-layer of NiO. The exterior thin-layer transmits the light into CdS in-turn exciton moved to surface for reaction with adsorbed reactant species. Structural, morphological and optical properties were studied using X-ray diffraction (XRD), ultraviolet-visible light (UV–vis) diffuse reflectance spectra (DRS), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS). The results illustrates that synthesized catalyst composed of crystalline CdS/NiO hierarchical structure that absorbs light in the visible spectrum and improved charge carrier separation than CdS or NiO alone. The photocatalytic activity was examined for H2 generation under visible light irradiation using Xe-lamp as light source. In order to achieve enhanced H2 production rate amount of NiO loading was optimized and results were found in the following order CdS/NiO > CdS. Under optimal conditions the catalyst showed stable H2 evolution for 30 h of continuous irradiation. Under optimal conditions catalyst showed visible light to H2 conversion efficiency of 6.63%.

Plasmonic enhancement of photoluminescence from cadmium sulfide and lead sulfide quantum dots

Plasmonic core/shell nanoparticles Ag/SiO2 with different shell thicknesses were synthesized. Localized plasmon resonance was investigated by UV-vis spectroscopy. Arranged layers of plasmonic nanoparticles and quantum dots were obtained on a quartz substrate using a spin-coating technique. Plasmon-enhanced photoluminescence excited by 405 nm laser corresponding to the plasmon resonance was studied on CdS and PbS quantum dots structures. The possibilities of twofold and fourfold intensity increase are demonstrated for CdS and PbS quantum dots respectively.

Hierarchical crystal growth of sheaf-like CdS by microemulsion/hydrothermal route

Cadmium sulfide nanostructures with a sheaf-like morphology were obtained via the simple microemulsion/hydrothermal process. By controlling the synthetic parameters such as reaction time, temperature and microemulsion media, different morphologies were obtained. These new CdS structures were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The optical properties of CdS semiconductor were discussed by the UV–Vis absorption and photoluminescence (PL) studies. Sheaf-like structures may be formed by the splitting crystal growth mechanism, which is known to explain the morphology of some mineral crystals present in nature.

Enhanced photocatalytic activity of Zn-doped dendritic-like CdS structures synthesized by hydrothermal synthesis

Abstract In this work, a series of Zn-doped dendritic-like CdS structures have been synthesized by a simple hydrothermal method. The as-prepared samples have been characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS), ultraviolet-visible (UV–vis) and room temperature photoluminescence (PL). Their photocatalytic activities have been evaluated by the photocatalytic degradation of methylene blue (MB) under simulated visible-light irradiation. XRD results indicate that the phase of Zn:CdS was hexagonal phase. XRD and EDS results indicate that Zn 2+ was successfully introduced into CdS. FESEM results indicate that low Zn 2+ doping concentration can keep the dendritic-like CdS structures, but the morphologies of Zn:CdS are flower-like structures at high Zn 2+ doping concentration. UV–vis results indicate that doping Zn 2+ can be used to improve the absorbing capability of dendritic-like CdS for visible light, and the content of Zn 2+ affects the band gap. PL results indicate that doping Zn 2+ can be used to improve the luminescence property of dendritic-like CdS. Photocatalytic results indicate that doping Zn 2+ is conducive to improve the photocatalytic efficiency of dendritic-like CdS to MB, and the highest degradation rate is 92.8%. And the photocatalytic mechanism of Zn-doped dendritic-like CdS to MB is also described.

Preparation of self-assembled hollow microsphere CdS via solvothermal method and its optical properties

In this work, the hollow microsphere CdS has been prepared by solvothermal method with oxalic acid as auxiliary agent. The effects of different experimental conditions on the morphology of CdS have been investigated. The as-prepared CdS has been analyzed by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive spectrometer, room temperature photoluminescence and ultraviolet–visible (UV–Vis). And the photocatalytic activity has been investigated on the degradation of methylene blue under simulated solar light irradiation. XRD result indicates that hollow microsphere CdS is hexagonal phase, which is highly crystallized. FE-SEM results indicate that the diameter of hollow microsphere CdS is about 5 μm, and the diameter of center hole is about 500 nm. UV–Vis result indicate that hollow microsphere CdS has a strong absorption in visible light region and the optical energy band gap is 2.31 eV. The fluorescence spectrum shows that hollow microsphere CdS structures have three emission peaks at 455, 545 and 582 nm, respectively. Photocatalytic result shows that the activity of hollow microsphere CdS remains 90 % after 5 recycle times, which indicates that hollow microsphere CdS has a good catalytic efficiency and stability to methylene blue. The growth mechanism of hollow microsphere CdS structures is also described.

Preparation of hierarchical CdS structures and effect of sodium dodecyl benzene sulfonate (SDBS) on the morphologies

Dendritic-like CdS and flower-like CdS structures have been prepared by hydrothermal method. The as-prepared CdS have been analyzed by X-ray diffraction, field emission scanning electron microscopy (FESEM), ultraviolet–visible and room temperature photoluminescence (PL). And the photocatalytic activities also have been investigated. FESEM results indicate the role of SDBS is to make the CdS crystals assemble together. The optical energy band gap of dendritic-like CdS is 2.46 eV, and flower-like CdS is 2.48 eV. PL results show that dendritic-like CdS and flower-like CdS emit both blue and green fluorescence. Photocatalysis results show that the catalytic efficiency of dendritic-like CdS is better than flower-like CdS.

Optical properties of flower‐like CdS prepared by a hydrothermal method with SDBS as surfactant

In this article, flower‐like CdS structures have been prepared by a hydrothermal method with SDBS as surfactant. The influences of different experimental conditions on the morphologies, UV‐Vis and fluorescence properties of CdS have been investigated. The performances of CdS have been analyzed by X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM), ultraviolet‐visible (UV–Vis) and room‐temperature photoluminescence (PL). The XRD result indicates that the flower‐like CdS structures are of hexagonal phase. The FESEM results indicate that the main role of SDBS is to make the CdS crystals assemble together to form the flower‐like structures. The UV–Vis results show CdS has a strong absorption in the ultraviolet region and visible‐light region. The PL results show CdS has two emission peaks, respectively at 461 nm and 553 nm. The growth mechanism for the formation of flower‐like CdS structures is also described.

Facile one‐pot low‐temperature solid‐state approach towards phase transformation of nanoCdS

Nanocadmium sulphide (CdS) has been prepared by the one-pot solid-state method from cadmium chloride (CdCl2) and sodium sulphide (Na2S) without any capping agent. The grinding period plays a major role in transforming CdS from the cubic (zinc blende) to the hexagonal (wurtzite) phase, hitherto unreported at the lowest temperature of 200°C by the solid-state approach. The compounds are characterised by powder X-ray diffraction, UV–visible absorption spectroscopy, scanning electron microscopy and high resolution transmission electron microscopy techniques. On the basis of the results, it has been observed that with only grinding and without subsequent heat treatment, the compounds named with their grinding period as subscript have either zinc blende – CdS(30 min) or mixed zinc blende/wurtzite – CdS(2,4, 6 and 8 h) structures. However, when subjected to heat treatment at 200°C, there is a complete phase transformation to the wurtzite structure achieved only with the CdS(8 h) compound, while the rest of the compounds show similar phases as the compounds prepared without annealing. The photocatalytic efficiency of CdS compounds on methyl orange follows the order, CdS(cubic) > CdS(mixed phase → cubic + hexagonal) > CdS(hexagonal), with cubic phase CdS showing greater efficiency than mixed and hexagonal phases.

Generation of Reactive Oxygen Species, Electrons/Holes, and Photocatalytic Degradation of Rhodamine B by Photoexcited CdS and Ag2S Micro-Nano Structures

Identifying the dominantly active species and their reactive behaviors in semiconductor photocatalysis is important for developing a full understanding of their photochemical and photophysical properties. Here we report an effective method for studying the reactive oxygen species (ROS) and charge carriers generated by irradiating single crystalline CdS and Ag2S micro-nano structures (MNS). Our method, based on electron spin resonance spectroscopy (ESR) combined with spin trapping and spin labeling techniques, confirmed the generation of superoxide and charge carriers and their contribution to photocatalytic degradation of rhodamine B elicited by CdS and Ag2S MNS. The electronic band structures determined the reactivity of photogenerated holes/electrons and the generation of reactive oxygen species. Our comparison of CdS and Ag2S MNS showed that, because of the large difference between their band edge positions, these two sulfides differ greatly in ROS production and in the reactivity of photoinduced elect...