Narrow Results

In this work, we study the influence of the temperature on the mechanism of current transfer in the reverse branch of the current–voltage (I–V) characteristics of n-CdS/p-CdTe heterostructures. The study of the heterostructure, using the technique of on energy-dispersive X-ray analysis, showed that a layer of CdS_xTe${}_{1-x}$ is formed at the boundary of the heterojunction with a varying composition, being equal $x\approx 0.48$ from the side of CdS and $x\approx 0.02$ from the CdTe side. In the studied range of the temperatures and bias voltage, the current-voltage characteristics are described well by a power law $J=A{V}^{\alpha }$, where the exponent $\alpha$ changes with the temperature and voltage. Under the influence of the temperature and charge carrier concentration, the mechanism of current transfer in the structure changes from exclusion ($\alpha \approx 0.5$) to ohmic ($\alpha \approx 1$), and then goes to injection ($\alpha \approx 2$). The inhomogeneous intermediate CdS_xTe${}_{1-x}$i-layer at the boundary of the n-CdS/p-CdTe heterostructure is characterized by the presence of metastable states that rearrange at high temperatures and certain charge carrier concentrations. As a result of this, the exclusion slows down and electrons are injected from the rear molybdenum contact.

II–VI Semiconductor nanocrystals (NCs) with tunable visible emission, such as CdS, CdSe and CdTe, were synthesized in aqueous solution using thiols as capping molecules. Hydrazine was found to promote the growth of NCs through a special mechanism. In only a few hours, the synthesis process was completed at room temperature. Under moderate conditions, the capping molecules not only changed the growth rate of NCs simply by varying the concentration, but also altered the spectral properties of NCs. The capping molecules with amino groups were propitious to the growth of CdS NCs, whereas the kinetic growth of CdS NCs was more affected by the surface passivation efficiency of NCs than by steric hindrance in the system. The fastest growth of the CdS NCs was achieved when glutathione was used as a capping molecule, while the emission of CdS and CdSe NCs were shown to remain steady and tunable using the same capping molecule. The growth rate of 3-mercaptopropionic acid-capped CdS and CdSe NCs slowed down significantly, while CdTe NCs were obtained with excellent emission properties when capped with the same molecule. Furthermore, our approach will also be useful for the study of the kinetic growth of NCs in aqueous solution.

A new-type photocatalyst of cadmium sulfide carbon nanotubes (CdS/CNTs) was prepared by the hydrothermal method. This as-prepared CdS/CNTs composite photocatalyst was proved to exhibit an excellent photocatalytic activity for degradation of tetracycline (TC). Specially, the 95%-CdS–5%-CNTs composite photocatalyst played the best degradation rate (81.2%) in 60 min under the visible light irradiation. Moreover, this 95%-CdS–5%-CNTs composite photocatalyst possessed great stability and could be used at least four cycles with almost no loss of photocatalytic efficiency. Furthermore, the as-synthesized CdS/CNTs composite photocatalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-Vis diffused reflectance spectra (UV-Vis), Raman and thermal gravimetry (TG). In addition, the possible mechanism and kinetics of photodegradation of TC with CdS/CNTs photocatalyst was also discussed.

A unique CdS/Fe₃O₄/rGO composite photocatalyst is successfully synthesized by the microwave method. It displays promising photocatalytic activity towards the photo-degrading of tetracycline (TC) in aqueous solution, the degradation rate of TC is 69% with adding 0.1g CdS/Fe₃O₄/rGO photocatalyst into 20mg/L tetracycline for 2h under visible light irradiation. Furthermore, the mechanism was systematically investigated by active species trapping experiment. It can be known that ${\mathrm{\text{e}}}^{-}\mathrm{\text{was}}$ the major active species in the photodegradation process and the possible process of charge transfer for CdS/Fe₃O₄/rGO was proposed based on the experimental results. The as-prepared samples were carefully evaluated by XRD, TEM, XPS, VSM, PL spectra, Raman spectrometer.

An integrated tandem photoelectrochemical (PEC) cell, composed of a three-dimensional (3D) ZnO/CdS/NiFe layered double hydroxide (LDH) core/shell/hierarchical nanowire arrays (NWAs) photoanode and a $p$-Cu₂O photocathode, was designed for unassisted overall solar water splitting in this study. The optical and photoelectrochemical characteristics of ZnO-based photoanodes and Cu₂O photocathode were investigated. The results show that ZnO/CdS/NiFe LDH nanostructures offer significantly enhanced performances with a photocurrent density reaching 5.8mA$\cdot$cm${}^{-2}$ at 0.9V and an onset potential as early as 0.1V (versus RHE). The enhancement can be attributed to the existence of CdS nanoparticles (NPs) which boosts the light absorption in visible region and enhances charge separation. Moreover, the introduction of NiFe LDH nanoplates, with unique hierarchical mesoporous architecture, promotes electrochemical reactions by providing more active sites as co-catalyst. On the above basis, the ZnO/CdS/NiFe LDH–Cu₂O two-electrode tandem cell system was established. At zero bias, the device shows a photocurrent density of 0.4mA$\cdot$cm${}^{-2}$ along with the corresponding solar-to-hydrogen (STH) conversion efficiency reaching 0.50%. Our results indicate that the tandem PEC cells consisting of metal–oxide–semiconductor photoelectrodes based on Earth-abundant and low-cost materials hold promising application potential for overall solar water splitting.

Semiconductor materials used in the field of photocatalysis have been attracting much attention. Due to the advantages of green, pollution-free and sustainable development of solar energy, it is an ideal strategy to explore excellent semiconductor materials as high light photocatalysts for energy conversion. Herein, Bi₄Ti₃O${}_{12}$/CdS composites were synthetized by coprecipitation method, which CdS particles selectively deposited on Bi₄Ti₃O${}_{12}$ nanosheets. The phase structure and optical properties of the samples were characterized by XRD, SEM, N₂ adsorption–desorption and UV-visible diffuse spectra (UV-DRS). The results showed that the Bi₄Ti₃O${}_{12}$/CdS composites had the highest photocatalytic activity against RhB under visible light, and the degradation rate of RhB was 98.8% after 120min of simulated light, 2.14 times that of pure Bi₄Ti₃O${}_{12}$, and the Bi₄Ti₃O${}_{12}$/CdS-10wt.% composites also showed good stability. UV-DRS demonstrated that the optical absorption range of the composite extends to visible regions, and photocurrent tests also showed that the composite enhances the separation and migration of photoogenic electron–hole pairs, mainly due to the formation of 2D nanosheets/0D particles heterojunctions between the bronzn CdS of the perovskite BTO and hexagonal fibers. Furthermore, free radical assays confirmed that both $\cdot$O${}_2^{-}$, h${}^{+}$ and $\cdot$OH have effects in the degradation of RhB, and thus suggested a possible mechanism for the photodegradation process of the Bi₄Ti₃O${}_{12}$/CdS-10wt.% composite photocatalyst.

Two novel CdS- and Cr-doped CdS nanostructures, including nanoparticles and nanoparticles, were successfully synthesized by solvothermal reaction with hydrazine hydrate (HHA), ethylene glycol (EG), ethylenediamine (EN) and ethanolamine (EA) as mixed solvents in different sulfur and cadmium sources. The structure, morphology and properties of the products were characterized using X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectrometer (EDS) and Vibrating sample magnetometer (VSM), respectively. The morphology of the Cr-doped CdS nanostructures was nanorod, with an average diameter of 70–90nm and lengths of 1–2.5$\mu$m. The product was observed to be composed of S, Cd and Cr by EDS. The VSM tests demonstrated that the Cr-doped CdS nanorods had super strong ferromagnetism at room temperature, while pure CdS nanorods were weak ferromagnetism. The results confirmed that the prepared the Cr-doped CdS nanorods had ferromagnetism at room temperature, and the saturation magnetization $M_s$ was approximately 9.125 (10${}^{-3}$emu/g), the coercivity of $H_c$ was approximately 139.22Oe.

The advancement of technology has resulted in severe issues in the natural environment, notably organic water contamination that poses a significant threat to living organisms. To mitigate such problems, various technological solutions have been developed to treat water pollution. The emergence of photocatalytic semiconductor technology has enabled the utilization of numerous novel semiconductor composites for pollution control due to their high efficacy and eco-friendliness. In this paper, TpTt/CdS composites were produced via a simple two-step process, and the resulting samples were characterized using X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, ultraviolet (UV)–visible and photodegradation experiments using methylene blue to simulate organic pollutants. The experimental findings reveal that the composite structure system enhances the radiation absorption capacity of CdS in the UV range, as well as the adsorption capability of organic pollutants. This introduces a fresh concept for modifying semiconductor composite structures and highlights the considerable potential of CdS in degrading organic contaminants.

In this study, a cladding-modified fiber-optic sensor is reported for NO₂ gas detection. Monitoring the purity of air is the need of the hour, with the growing technologies. Hence, in this work, Ag-doped CdS is coated over the cladding-removed region of 3cm length by Chemical Bath Deposition (CBD) which acts as the gas-sensing medium. Ag–CdS is coated over four fibers each with a different coating duration of 10min, 20min, 30min and 40min. Characterization of Ag–CdS is done by Scanning Electron Microscope (SEM), UV-visible absorption spectroscopy and UV-visible reflectance spectroscopy. The spectral response for different concentrations of NO₂ is studied on the four fibers separately, and it is analyzed and compared. The minimum detection limit is 100ppm and the response time is 10min. Out of the four fibers, Ag–CdS-30 exhibited the best response with a sensitivity of 15.5%. The results are compared with cladding-modified fiber coated with CdS, which was reported previously. The effect of Ag-doping is analyzed.