Preparation Of CdS Research Articles

Preparation of CdS–Ag2S nanocomposites by ultrasound-assisted UV photolysis treatment and its visible light photocatalysis activity

Abstract Thiosulfate is a green leaching agent used in the hydrometallurgical process because it is both environmentally benign and can form the required soluble ion complexes. In this article, a novel method for the synthesis of CdS–Ag2S nanocomposites from a solution of relevant ion complexes via ultrasound-assisted ultraviolet (UV) photolysis was proposed. An analysis of the mechanism revealed that the complexes undergo a series of photochemical reactions. The CdS–Ag2S nanocomposites were synthesized by photochemical co-precipitation under UV-C irradiation. The microstructure, chemical composition, optical and electrochemical properties of the prepared nanocomposites were analyzed to verify the synthesis and investigate the product. The photodegradation of methyl orange (MO) under a xenon lamp was performed to determine the photocatalytic activity. Under visible light irradiation, the CdS–Ag2S nanocomposites undergo the electrons transition (from valence band to conduction band) to form photogenerated electron–hole pairs realizing the effective separation of carriers and finally promote the degradation of MO to water and carbon dioxide. The subsequent degradation efficiency of the CdS–Ag2S nanocomposites was found to be 87% after 90 min, and it was larger than 78% for pure CdS prepared via UV photolysis, indicating that the as-developed novel method can effectively fabricate CdS–Ag2S photocatalyst with superior performance.

Preparation and Characterization of CdS and PbS Chalcogenides Compounds and n-CdS/p-PbS photodiode

In this study, a chemical bath deposition method (CBD) is used to synthesize CdS nanocrystalline thin films onto FTO substrate using two temperatures of 70 and 80 ºC for 1h of preparation time. PbS nanocrystalline thin films are also prepared using CBD using temperature of 35 ºC for 2h. XRD measurements confirmed that the prepared CdS and PbS thin films are polycrystalline with hexagonal phase for CdS and cubic for PbS. Scanning Electron Microscope images show increasing particles size of CdS thin films with increasing temperature of preparation and the films became more adherent on the substrates without pinholes or vacancies. Optical properties are investigated through UV-Visible Spectroscopy and found decreasing in the transmittance of prepared thin films with increasing temperature. Energy band gap calculated for CdS and PbS nanocrystalline thin films found with values higher than bulk value indicating to due to the quantum confinement effect. Photoluminescence spectra of prepared CdS nanocrystalline thin films appeared sharp emission beak at around 550 nm for all samples indicating high crystallinity. Photoresponse measurements of the fabricated photodetector showed a significant sensitivity to visible light at zero applied voltage, indicating that the fabricated device is a self-powered photodetector. The device was highly photosensitive of 16833, responsivity of 1.44 mAW−1, and a low rise/fall time of 0.284/0.298 s.

Preparation of CdS and its Photocalytic behaviour for Dye Degradation

A short time ago, transition metal sulphides like CdS has been arduously studied because it has unique catalytic functions. This disclosed that CdS nanocrystals are good photocatalysts because it can quickly generate electron-hole pairs by photo-excitation. In the present work, CdS is prepared by hydrothermal process. Prepared samples were characterized by X-ray diffractions (XRD), SEM, Optical study, and for evaluation of photophysical properties, UV/VIS spectra were recorded. By UV irradiation and photocatalytic decay of dyes, the photoactivity of synthesised CdS was accessed. The CdS shows higher catalytic activity.

Apple juice and red wine induced mirror-image circular dichroism in quantum dots.

Juices, wines, and extracts from plants contain high concentrations of various chiral compounds such as carboxylic acids or sugars. Several prior studies reported the synthesis of metallic and semiconducting nanoparticles relying on components of complex biological solutions. Herein, we present preparation of chiral CdS and CdSe quantum dots (QDs) using apple juice and red wine via phase transfer ligand exchange. Although both apple juice and red wine contain a complex mixture of chiral and achiral compounds, we have successfully used them for selective induction of predicted chiroptical properties and confirmed L-malic acid from the apple juice and L-tartaric acid from the red wine as the chiral inducers. This work illustrates the capability of using complex mixtures to construct chiral QDs with desired chiroptical properties as well as potential of QDs to selectively report a chiral molecule in a complex chiral mixture without the need for elaborate chiral recognition system.

Preparation of CdS@C Photocatalyst Using Phytoaccumulation Cd Recycled From Contaminated Wastewater.

Cadmium is one of the most toxic heavy metal contaminants in soils and water bodies and poses a serious threat to ecosystems and humans. However, cadmium is also an important resource widely used in many industries. The recovery of cadmium in the form of high-value products is considered as an ideal disposal strategy for Cd-contaminated environments. In this work, Pistia stratiotes was used to recycle cadmium from wastewaters through phytoaccumulation and then transformed into carbon-supported cadmium sulfide photocatalyst (CdS@C) through carbonization and hydrothermal reaction. The CdS@C photocatalyst contained a mixture of cubic and hexagonal CdS with lower band gap energy (2.14 eV) and high electron-hole separation efficiency, suggesting an excellent photoresponse ability and photocatalytic efficiency. The impressive stability and photocatalytic performance of CdS@C were demonstrated in efficient photodegradation of organic pollutants. •OH and O2•- were confirmed as the major active species for organic pollutants degradation during CdS@C photocatalysis. This work provides new insights into addressing Cd contaminated water bodies and upcycling in the form of photocatalyst.

Preparation and characterization of CdS prepared by hydrothermal method

An attempt has been made to examine the Cd2+ source concentration effect in the structural, morphological, optical, electrical, and dark current features of CdS films. The nano films have been successfully carried out onto glass substrates by hydrothermal technique at 130 °C for 1 h. Cadmium sulfate salt was used as a source of Cd precursor with various concentrations 0.08, 0.12, 0.14, and 0.2 M. The polycrystalline nature with a mix of cubic and hexagonal system of CdS films structure with the discriminatory orientation of H(002)/C(111) was identified by X-ray diffraction studies. Further, the Field emission-scanning electron microscope (FE-SEM) analysis has revealed a unique morphology as strings-like and flower-like nanostructures. It was clearly observed the existence of CdS nanograins as building units with an average grain size of 24 nm and 15 nm of 0.08 M and 0.12 M CdS thin films, respectively. The computed optical band gap was found in the values range of 2.1–2.3 eV. The Electrical analysis revealed that variation in CdSO4 molarity reduced the electrical resistivity from 2.1 × 108 to 3 × 106 (Ω.cm). Photoconductivity studies showed that the best ratio of the photocurrent to the dark current ratio Iph/Id was 2 × 104 for CdS that was prepared with 0.12 M. The Photoconductivity properties of these films have been presented to show that such films can be useful for photodetector device applications.

Rational design of chemical bath deposition technique for successful preparation of Mn-doped CdS nanostructured thin films with controlled optical properties

The introduction of a rational design for depositing internally-doped nanostructured thin films is of great importance for optoelectronics. In this presented work, Mn-doped CdS thin films with high purity in composition were prepared through the chemical bath deposition technique using a nucleation-doping strategy. This work focuses on an improved chemical design to eliminate mostly ignored property of conventionally doped nanoscale thin films. The synthesis strategy was initiated by the initial formation of MnS nuclei in a colloidal depositing solution followed by injection of cadmium precursor to diffuse into the initial nuclei and play the role of host CdS matrix which was the beginning of the deposition process. Upon optimization of the PL-emission, it was revealed that relative intensity of Mn2+-related peak to the excitonic peak has significantly increased (~100 times) in 80 °C, pH = 6, and precursor molar ratio of Cd:Mn:EDTA:S equal to 1:3:0.4:5, at deposition time of 300-min. The TRPL measurements further revealed the effective contribution of Mn-related midgap states with long-lived decay curve character, which confirms the success of the designed approach to reach internally doped thin films. It was found that the deposition temperature, amount of Cd/Mn/TA precursors, and deposition time are the most important experimental parameters in the proposed synthesis approach. Due to the versatility, generality, and colloidal advantages of this method, it can be extended to the other structures with various types of dopant agent.

Heat-transfer ('iron-on') photocatalytic films

The simple preparation of nanoparticulate CdS and TiO2 photocatalytic (PC) films embedded in a thin (2.5 μm) layer of polystyrene (PS), i.e. PC-PS films, is described. These CdS-PS, or TiO2-PS, films are then readily and easily transferred onto a range of different common flexible materials, such as many different plastics and fabrics, using the heat from an iron. In all cases the heat-transferred PC-PS films appear physically robust, as demonstrated by the 3 M Scotch Tape test, and, for the same PC, exhibit a similar photocatalytic activity, regardless of the material it is ironed onto. The photocatalytic activities of these iron-on films are demonstrated using cotton as the material support. Thus, the CdS-PS-Cot film is used to photoreduce methyl orange, methyl viologen and water using visible light (415 nm) and a sacrificial electron donor (ascorbate or EDTA). The TiO2-PS-Cot film is used to effect the same reduction reactions, but with UVA light (365 nm). The TiO2-PS-Cot film is also able to photocatalyse the oxidation of methylene blue and NO by air. In most cases there is little or no loss of activity with repeated use. Encouragingly, the non-optimised TiO2-PS-Cot film appears more active than the commercial flexible polymeric photocatalytic film Purify Mesh 30 (Taiyo Europe GmbH).

Synergistic effect of nanoflower-like CdS for removal of highly toxic aqueous Cr(VI)

Thiourea assisted hydrothermal preparation of nanoflower-like CdS (NFs) synthesis and its efficient performance to remove toxic Cr (VI) in aqueous solution has been reported in this article. CdS NFs show synergistic behaviour via photo-catalytic reduction and adsorption to remove the toxic Cr (VI) and reduce to non-toxic Cr (III) ionic state in the aqueous solution at the room temperature. The adsorption of Cr (VI) from the aqueous solution stable time was observed ~120 min at the pH of 2 having an adsorption efficiency of 92%. Various adsorptions of kinetic and isothermal models have been further applied to understand the adsorption mechanism. The pseudo-second-order kinetic and Langmuir equilibrium adsorption isotherm model fitted best to describe Cr (VI) adsorption process. These results confirm the possibility of toxic Cr (VI) removal in water remediation without employing any costly noble metal-based catalyst.

Preparation of High-Performance CdS@C Catalyst Using Cd-Enriched Biochar Recycled From Plating Wastewater.

Biochar is widely used for the adsorptive removal of Cd from water and soil, but the Cd-enriched biochar produced carries a risk of secondary pollution. In this work, biochar derived from rice straw was used to adsorb Cd from plating wastewater. The Cd-enriched biochar showed a saturated adsorption capacity of about 63.5 mg/g and could be recycled and used in a mesoporous carbon-supported CdS (CdS@C) photocatalyst after pyrolysis carbonization and a hydrothermal reaction. The results demonstrated that the as-prepared CdS@C photocatalyst contained mixed cubic and hexagonal CdS phases, with a considerably lower band gap (2.1 eV) than pure CdS (2.6 eV). CdS@C exhibited an enhanced photocatalytic performance for the degradation of organic dyes under visible light irradiation compared with pure CdS due to its excellent light-harvesting capacity and efficient electron-hole separation. Moreover, the continuous formation of active species (h+, •OH, and O2•−) was responsible for the photodegradation of organic dyes using CdS@C. This work provides new insights for the safe disposal of Cd-enriched wastewater and for improving the economic viability of Cd-contaminated resources by recovering a value-added photocatalyst.

Preparation and Photocatalytic Properties of CdS and ZnS Nanomaterials Derived from Metal Xanthate.

In this paper, we report a new, simple method for the synthesis of CdS and ZnS nanoparticles (NPs) prepared in a basic aqueous medium using metal xanthate as the sulfur source. The structure, morphology, size distribution, optical band gap, and photocatalytic properties of the newly obtained nanomaterials were investigated by UV-Vis spectroscopy, X-ray diffraction, and transmission electron microscopy. The results show that both CdS and ZnS crystallized in cubic phase and formed NPs with average sizes of 7.0 and 4.2 nm for CdS and ZnS, respectively. A blue shift of UV-Vis absorbance band and higher energy band gap values were observed for both materials in comparison with their bulk counterparts, which is in accordance with the quantum confinement effect. The as-prepared nanomaterials were tested in visible-light driven photocatalytic decomposition of methylene blue (MB). After irradiation for 180 min, the degradation rate of MB with a concentration of 8 × 10−6 mol/L mixed with a photocatalyst (CdS or ZnS, both 10 mg in 100 mL solution of MB) was found to be 72% and 61%, respectively. The CdS NPs showed better photocatalytic activity than ZnS, which could be explained by their lower energy band gap and thus the ability to absorb light more efficiently when activated by visible-light irradiation.

Preparation of CdS–TiO2-Based Palladium Heterogeneous Nanocatalyst by Solvothermal Route and Its Catalytic Activity for Reduction of Nitroaromatic Compounds

In this study, bare CdS nanoparticles (NPs) were prepared by solvothermal method using CdCl2(3-methylbenzaldehyde thiosemicarbazone)2 as a single-source molecular precursor in the presence of ethylene glycol. Further, these CdS NPs were used for the preparation of binary (CdS–TiO2) and ternary (CdS–TiO2/Pd) heterogeneous nanocatalysts. Characterization of the as-prepared nanocatalysts has been carried out using different techniques such as powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV–visible diffuse reflectance spectroscopy, and photoluminescence studies. The peak observed at 2θ = 39.5° in XRD confirms the successful doping of noble metal (Pd) on the surface of CdS–TiO2 nanocatalyst, which is well supported by Raman analysis. From FESEM and TEM analyses, mixed morphology has been observed and elemental composition was confirmed by energy-dispersive X-ray spectroscopy elemental mapping. Furthermore, the as-prepared bare CdS NPs, binary CdS–TiO2, and ternary CdS–TiO2/Pd heterogeneous nanocatalysts were used for the reductive transformation of various nitroaromatic compounds to their corresponding aromatic amines at room temperature. It has been observed that among all of the catalysts, ternary CdS–TiO2/Pd heterogeneous nanocatalyst has excellent catalytic property to reduce all nitroaromatic compounds in very short time span.

Preparation of CdS/ g-C3N4/ MOF composite with enhanced visible-light photocatalytic activity for dye degradation

CdS nanoparticles was hybridized with graphitic carbon nitride (g-C3N4) sheets and titanium metal-organic framework (MOF) using a facile solvothermal method, for the catalytic photodegradation of Rhodamine B dyes under visible light irradiation. Characterization of as-obtained samples was performed by X-ray diffraction, scanning electron microscopy equipped with an energy dispersive X-ray spectrometer (EDS), Fourier transform infrared spectroscope, thermogravimetric analysis, N2 absorption-desorption and ultraviolet–visible diffuse reflection spectra. The CdS/g-C3N4/MOF composite (238.43 m2/g) exhibited a remarkably high photocatalytic activity under the visible light irradiation, the degradation rate reached almost 90.2% for RhB after 90min reaction, far outperforming other decent photocatalysts like pure CdS, MOF, g-C3N4 under the same conditions. The superior photocatalytic activity of the CdS/g-C3N4/MOF composite is attributed to enhanced separation of the photogenerated electron–hole pairs, as well as increased visible-light absorption. Therefore, CdS/g-C3N4/MOF composites, prepared using a facile method are applicable to the development of the novel high-efficiency photocatalytic samples for future research.

Theoretical investigation on the optical and EPR spectra for Cu2+ -doped ZnO-CdS nanocomposites.

The three optical absorption bands and EPR parameters of the [CuO6 ]10- center in the ZnO-CdS composite nanopowders are theoretically studied from the perturbation formulas based on the cluster approach. In the formulas, the contributions to EPR parameters arising from the ligand orbital and spin-orbit coupling interactions via covalence effect are considered. For the studied [CuO6 ]10- cluster, the Cu-O bond lengths are suggested to show a relative elongation ratio ρ (≈ 4.1%) along the z-axis due to Jahn-Teller effect. The defect models suggested in this work are different from the previous assumption that the impurity Cu2+ can replace the host Zn2+ site when it enters the lattices of the ΖnO and ΖnS nanocrystals, forming the tetrahedral [CuΧ4 ]6- clusters (Χ=O, S). The validity of the proposed model is discussed. The differences between the present calculations and the previous ones for the interstitial Cu2+ center in ZnO nanocrystals are analyzed in view of the dissimilar impurity behaviors due to the new composition CdS and distinct preparation conditions.

In situ preparation of CdS decorated ZnWO4 nanorods as a photocatalyst for direct conversion of sunlight into fuel and RhB degradation

In situ synthesis of monoclinic ZnWO4 nanorods decorated with hexagonal CdS nanoparticles by a facile solvothermal method used as photocatalysts for hydrogen production under solar light.

An investigation on SnS layers for solar cells fabrication with CdS, SnS2 and ZnO window layers prepared by nebulizer spray method

The preparation of SnS, CdS, SnS2 and ZnO thin films by nebulizer spray method, and their characterization is reported. The size of crystallites, dislocation density, texture coefficient and strain were estimated using XRD data. SEM study revealed good surface morphology of films. Optical properties of deposited SnS, CdS, SnS2 and ZnO films were estimated using the optical absorption measurements. The calculated optical energy gaps of CdS, SnS2, ZnO and SnS films were, respectively, found as 2.45, 2.41, 3.2 and 1.45 eV. Hall effect measurements exhibited p-type conductivity for SnS and n-type conductivity for CdS, SnS2, ZnO thin films. The grown SnS thin films showed resistivity and carrier concentration as 0.0689 Ωcm and 1.04 × 1019 cm− 3, respectively. Heterojunction solar cells of FTO/CdS/SnS, FTO/SnS2/SnS, and FTO/ZnO/SnS were also fabricated and their properties studied. The fabricated FTO/ZnO/SnS heterojunction solar cell presented a superior performance with conversion efficiency (0.96%) greater than other structures.

Facile preparation of Z-scheme CdS[sbnd]Ag[sbnd]TiO2 composite for the improved photocatalytic hydrogen generation activity

Photocatalytic hydrogen evolution is a prospective approach to solve the problem about energy crisis by fossil fuel combustion. As the good candidate to generate hydrogen under visible light irradiation, the rapid charge recombination and easy photocorrosion of pure CdS nanomaterials limited its hydrogen generation activity and photocatalytic stability. Here we constructed a novel ternary Z-scheme CdSAgTiO2 composite based on CdS nanowires by a three-step process to solve this problem. Compared with CdSTiO2 and CdS, the Z-scheme CdSAgTiO2 composites could obviously extend the light-absorption region, accelerate the transfer rate of charge-separation, and possess stronger redox capability. The prepared Z-scheme CdSAgTiO2 composites show high photocatalytic hydrogen evolution rate of 1.91 mmol h−1 g−1, which is 1.50 and 2.45 times that of CdSTiO2 heterojunction and pure CdS nanowires. The Z-scheme photocatalytic system exhibits the synergetic effects due to more efficient charge transfer and surface plasmon resonance absorption. Ag nanoparticles used as electron mediator could decrease the recombination of the photocarriers, alter the path of charge transfer and suppress the photocorrosion. This work opens up a new way for the novel Z-scheme photocatalytic systems that suppress the photocorrosion of CdS, and has a promising application in the photocatalytic water splitting.

Facile preparation of mixed-phase CdS and its enhanced photocatalytic selective oxidation of benzyl alcohol under visible light irradiation

Selective oxidation is one green technique for routine organics synthesis and environmental remediation. However, the conversion ratio resulted from environment-friendly method employing traditional photocatalytic materials like CdS is relatively low as compared with homogeneous catalytic reaction. Herein, in this paper, a facile method is reported to prepare mixed-phase CdS nanocrystals at room temperature. The as-prepared CdS samples were characterized by X-ray diffraction (XRD), UV–Vis diffuse reflectance spectra (DRS), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic oxidation of benzyl alcohol into benzaldehyde catalyzed by as-prepared CdS was carried out with high conversion of 68% generated within 60 min using O2 as a benign oxidant under ambient condition. The enhanced catalytic activity could be attributed to the mixed-phased crystal structure which facilitates the separation of photogenerated charge carriers.

Preparation and Characterization of Polycrystalline CdS Thin Films Deposited by Chemical Bath Deposition

Preparation and Characterization of Polycrystalline CdS Thin Films Deposited by Chemical Bath Deposition

Preparation of PbS and CdS cosensitized graphene/TiO2 nanosheets for photoelectrochemical protection of 304 stainless steels

TiO2 nanosheets with highly reactive {0 0 1} facet exposed were prepared and modified with graphene and PbS/CdS quantum dots (GT/PbS/CdS) by a facile two-step hydrothermal method and a sonication-assisted successive ionic layer adsorption and reaction (S-SILAR) process. The GT/PbS/CdS composites exhibit superior photoelectrochemical performance for the enhanced photocurrent density, corrosion potential and corrosion morphology of the connected 304 stainless steel. The light harvesting feature of the composites is improved for the narrow band gap quantum dots deposition and the interband transition of the photoexcited electrons in the heterostructure. The p-n junction electric field formed in the TiO2/PbS interface and the CdS/PbS interface promotes the separation of electrons and holes in the hybrid semiconductor. The increased inner electric field intensity in the semiconductor/electrolyte interface and the Schottky barrier in the semiconductor/metal interface boost the photogenerated electron transfer from the semiconductor to the connected metal, leading to enhancement of the photoelectrochemical protection performance. Furthermore, the electrochemical oxidation and reduction of the PbS is expected to prolong the protection in dark.