CdS Crystals Research Articles

Structural Modifications of CdS/Graphene Oxide with Ionic Dopants of Fe/Ag for Degradation of Methylene Blue

Global demand for pollution removal agents requires advanced materials to provide a good protocol to keep clean water resources. The composition of CdS was modified with ionic dopants including iron (Fe) and silver (Ag) and is incorporated into graphene oxide (GO) nanoparticles. The obtained compositions are CdS, Fe-CdS, Ag-CdS, CdS@GO, Fe-CdS@GO, and Ag-CdS@GO that have been fabricated by the co-precipitation method and examined by several techniques to estimate the morphological, optical, and structural properties using TEM, SEM, UV–Vis analysis, and XRD. The crystallite size of the CdS@Go was measured using the Williamson-Hall (W–H) method and was found to be around 28.6 nm. Furthermore, the a-axis was found to be 5.78 Å and 5.80 Å for cubic crystals and the a-axis achieved 14.28 to 14.24 Å for an orthorhombic crystal of CdS, respectively. The average roughness varied from 32.30 ± 3.3 to 66.65 ± 10.9 nm for CdS and Ag-CdS@GO. The degradation of methylene blue (MB) is increased from 75.56, 73.87, 76.01, 81.53, 89.34, and 91.68% for CdS, Fe-CdS, Ag-CdS, CdS@GO, Fe-CdS@GO, and Ag-CdS@GO after 60 min of exposure under visible light irradiation. The pseudo-first-order constant (Kapp) is increased from 4.4 × 10−3 to 39.4 × 10−3 min−1 for CdS and Ag-CdS@GO.

EFFECT OF CALCINATION TEMPERATURE VARIATION ON GREEN SYNTHESIS OF CADMIUM SULFIDE FOR CIPROFLOXACIN PHOTODEGRADATION

The green synthesis method has been successfully carried out to CdS with tea leaf extract and calcination temperature variation for the application of photocatalytic degradation of ciprofloxacin antibiotic. Variations in calcination at temperatures of 500, 600, and 700 ℃ were carried out to determine the effect of temperature on morphology and elemental composition, crystal structure and size, functional groups, and band gap energy by SEM-EDX, XRD, FTIR, and UV-DRS Spectrophotometer. The SEM-EDX image of the synthesized CdS is smooth and spherical and there is agglomeration with an even distribution of elements. The results of XRD and FTIR characterization showed the CdS peaks. The size of the CdS crystal increased with increasing temperature, namely CdS-600 at 64 nm and CdS-700 at 81.58 nm. The band gap energy value is influenced by the calcination temperature during synthesis with the band gap energy values of CdS-600 2.3 eV and CdS-700 2.38 eV. The percentage of CdS effectiveness with variations in calcination temperature in ciprofloxacin photodegradation is CdS-500 at 32.18%, CdS-600 at 48.72%, and CdS-700 at 8.73%. The optimum condition of CdS synthesis in degrading ciprofloxacin by photocatalytic process occurs at a temperature of 600℃ with a photocatalytic irradiation time under visible light for 120 minutes, a CdS mass of 10 mg, and an initial concentration of ciprofloxacin of 25 ppm. This result demonstrates the potential of an environmentally friendly method that can be applied in wastewater treatment.

Evolution of structural features in GO/CdS multilayer films for advanced optoelectronic devices

In this work graphene oxide/cadmium sulphide [GO/CdS]n multilayer films were obtained onto FTO/SLG substrates by cyclic electrophoretic deposition (EPD) and successive ion layer adsorption and reaction (SILAR) methods, with 3, 5, 7 and 10 cycles. The optical characterization for 3 cycles sample exhibits an optical band gap of ∼2.9 eV due the nanocrystalline nature of CdS, from 5 to 10 cycles a blue shift is observed in the band gap around ∼2.15 eV by the electronic disorder induced by graphene oxide intercalation and the mixture of hexagonal/cubic phases of CdS. Raman spectra shows the longitudinal optical modes LO, 2LO and 3LO, the LO peak position shows a blue shift in comparison to the bulk CdS. The multilayer films of 3 and 5 cycles shows a wide range of photoluminescence emission from 350 to 700 eV, for samples of 7 and 10 cycles a quenching and red shift is observed attributed to the CdS crystals growth with a peak emission at 615 eV from bulk CdS, which make the materials suitable for photovoltaic solar cells and UV-Vis diodes for optoelectronic devices.

Enhanced photocatalytic H2 evolution: optimized atomic hydrogen desorption via free-electron transfer in sulfur-rich MoWS2+x on vacancy-engineered CdS crystals

The metal substitution method and in situ sulfur vacancy method synergistically increase carrier density, create electron-rich sites, weaken the S–Hads bond, and enhance hydrogen evolution in MoWS2+x/CdSv photocatalysts across the UV-vis-NIR region.

Solvent Annealing Enabling Reconstruction of Cadmium Sulfide Film for Improved Heterojunction Quality and Photovoltaic Performance of Antimony Selenosulfide Solar Cells

AbstractAntimony selenosulfide, Sb2(S,Se)3, has been considered as new‐generation light‐harvesting material for high‐efficiency photovoltaic applications due to its adjustable bandgap, high absorption coefficient, and excellent stability. In terms of device operation, the electron transfer from the electron transporting layer to Sb2(S,Se)3 layer plays a critical role in improving the photovoltaic energy conversion efficiency of solar devices. Intricately manipulating the surface and interface properties has been a great challenge in solar cell fabrications. Herein, an effective approach toward the reconstruction of the CdS interfacial layer, and the following Sb2(S,Se)3 absorber film by utilizing polar ethylenediamine (EDA) solvent annealing at room temperature is developed. It is found that the presence of nitrogen‐containing functional groups of EDA on the CdS surface not only promotes the grain growth and crystallization of CdS, but also induces optimized deposition of Sb2(S,Se)3 films in terms of interfacial contact and defect formation. Finally, the Sb2(S,Se)3 solar cell based on EDA–CdS achieves a top efficiency of 10.10%. This study provides an efficient method and a new understanding of chemically healing inorganic thin films.

Quantization of the Energy Spectrum of Holes in the Adiabatic Potential of the Electron

The spectra of the interband absorption of microscopic CdS crystals, 15 to 30 Å in size, grown in a transparent insulating matrix, are analyzed. A structural feature caused by quantization of the energy spectrum of the hole in the adiabatic potential of its Coulomb interaction with the electron has been detected near the transitions to the lower level of the size quantization of the electron.

Size Quantization of the Electron Energy Spectrum in a Microscopic Semiconductor Crystal

The interband absorption spectrum of microscopic CdS crystals ranging in size from ~30 to 800 Å and dispersed in a transparent insulating matrix has been studied. There is a significant (~0.8-eV) shift of the fundamental absorption edge in the short-wavelength direction, and there are oscillations in the interband absorption spectrum caused by quantum size effect.

Theoretical Analysis of Resonant Hyper-Raman Scattering of Light by 2 LO Phonons in a CdS Crystal

Theoretical Analysis of Resonant Hyper-Raman Scattering of Light by 2 LO Phonons in a CdS Crystal

Upconversion fluorescent tuning based on CdS and SiO2 photonic crystals for computer chip label

Manipulating fluorescence color to achieve patterned function may access to many applications and remains some challenges. In this work, we provide an effective way to manipulate upconversion fluorescence through the photonic crystals. The structure of the photonic crystals (PCs) has a regulatory effect on upconversion fluorescence. We assembled NaYF4:Yb3+/Er3+ upconversion nanoparticles (UCNPs) with SiO2 and CdS photonic crystals respectively to obtain the photonic crystals/upconversion nanoparticles (PCs/UCNPs) composites. We studied the manipulating mechanism of two kinds of photonic crystals on upconversion fluorescence, and realized patterning application. This study provides a new way to realize information coding, patterned display of fluorescence manipulating.

System of excitons bound at oxygen centers and stimulated emission of CdS crystals

The paper presents the results of a study of the optical properties of CdS on the basis of the band anticrossing theory (BAC) with the involvement of the wider source data to the analysis results. Depending on the growth conditions, the presence and change in the concentration of oxygen and intrinsic point defects, which determine the composition of the crystals, have been taken into account. Data from studies of the structural features of crystals have also been used. The concept of nonuniform distribution of oxygen isoelectronic centers in the CdS volume due to their predominant segregation in layers of stacking faults (SFs) and also on dislocations has been introduced. To analyze the optical data, the capabilities of the method for constructing band models, which collect extensive and multilateral information about specific samples have been used. A refined model multizone of [Formula: see text] with SFs, which determines the spectrum of edge emission, has been presented. The nature of the edge emission A2B6 crystals with a small deviation from stoichiometry (CdS type) was explained as a spectrum of bound excitons at oxygen centers in SF layers. The article gives recommendations for the diagnostics of CdS crystals, suitable for creating stable luminescent systems or lasers.

Resonant hyper-Raman scattering of light by LO phonons in wurtzite semiconductors

Theoretical treatment of resonant hyper-Raman scattering of light by LO phonons in wurtzite semiconductors is given. The hyper-Raman process was considered for the scattering geometry y(xxz)x at which it involves the two-photon transitions to the B and C excitons of the s-type. Allowance was made for different sequences of intermediate virtual states. On the example of a CdS crystal the influence of the possible dipole transitions to the deeper valence band on the frequency dependence of the scattering cross section was investigated.

Influence of Zn in the CdS Crystal Lattice and Its Impact over the Catalytic Activity in the H2 Production

Solid solutions ZnxCd1−xS were compared by coprecipitation and sonochemistry methods, where x = 0.2 . This rate is the one that presents the best photocatalytic activity and the best performance for the production of hydrogen from a water source, according to our previous results. The influence of the synthesis method on the morphology and its electronic properties of the CdS and Zn0.2Cd0.8S systems was investigated, as well as the effect of the incorporation of Zn in the crystal lattice and its effect on the production of hydrogen from the division of water. X-ray diffraction characterization confirmed the formation of a solid solution corresponding to a face-centered cubic crystalline phase with preferential growth of (111), (220), and (311) planes and hierarchical morphology according to SEM and TEM microscopy, formed by aggregated nanoparticles of ZnxCd1−xS compound. The crystallite size decreased with the Zn incorporation in the crystal lattice from 8.61 nm by a coprecipitation method to 4.37 nm when the synthesis was assisted with sonochemistry, and the crystallite sizes range from 7.92 nm to 3.80 nm for the case of CdS pure. Other characterization techniques were also used, such as photoluminescence (PL), Raman microscopy, and N2 adsorption and desorption. The PL results show tunability of band edge emission as a function of zinc concentration in the Zn0.2Cd0.8S nanoparticles. For the water splitting to hydrogen production, the separation of the charge carriers promoted by the incorporation of Zn in addition to the shallow trap emissions generated defects in the catalyst structure; such processes are important factors found which increased with the sonochemical method, as well as the potential matched positions.

Pressure effect on the electronic spectra of CdSe and CdS

The effect of pressure on the electronic band structure of CdSe and CdS compounds has been investigated using the density functional theory. In this approach, the generalized gradient approximation (GGA) and the Purdue–Burke–Ernzerhof (PBEsol) parameterization were used for the exchange-correlation potential calculation. The ground-state properties are determined for the bulk materials (CdS and CdSe) in wurtzite phase. Structure and electronic properties are studied in the range of hydrostatic pressures between 0 and 100 GPa. The electron band-energy structure and density of states were calculated at different pressures. The equilibrium structural parameters, bulk modules and bandgaps are calculated and compared with the available experimental data and other theoretical results. The shift in the energy gap, total energy and lattice parameters of CdSe and CdS crystals with pressure is determined and compared with other known data.

Slow Photon-Enhanced Heterojunction Accelerates Photocatalytic Hydrogen Evolution Reaction to Unprecedented Rates

Slow Photon-Enhanced Heterojunction Accelerates Photocatalytic Hydrogen Evolution Reaction to Unprecedented Rates

The Raman and hyper-Raman scatterings of light by LO-phonons in a CdS crystal under excitation near resonance with the An=2and Bn=1exciton levels

AbstractThe theoretical treatment of the scattering of light by LO-phonons under one-photon and two-photon excitation near resonance with the An=2and Bn=1exciton levels in a CdS crystal is given. The influence of the complex structure of the top valence band on these levels is taken into account by the use of the perturbation theory. Assumption of the nonzero matrix elements of the dipole transitions between the A and B sub-bands leads to the fact that the linear combinations of the 1s and 2p exciton wave functions conform to the two “perturbed” energy levels. The possible manifestations of this mixing of states in the resonance Raman and hyper-Raman scatterings are considered.

Calculation of the vibrational spectra of CdSe and CdS crystals with zinc blende structure

Binary semiconductor materials belonging to the AIIBVI group (where A = Cd, Zn, Hg; B = S, Se, Te) attract considerable attention due to interesting physical properties. The structural, electronic and optical properties of these crystals make them promising materials for a number of applications in nonlinear optics devices, detectors, photodiodes, solar cells, etc. In this work, the theoretical first-principle calculations of the electron, phonon, optical and thermodynamic properties of a CdSe and CdS crystals with a zinc blende structure are performed. The electron and phonon dispersion at high symmetry directions, density of electron and phonon state, temperature dependence feature of Raman spectra, heat capacity, free energy, entropy, enthalpy and Debay temperature are estimated with the generalized gradient approximation (GGA). A Perdew–Burke–Ernzerhof functional (PBEsol) was utilized. To study the optical properties a complex dielectric function ε(ħω). All of the calculated parameters correlate well with the known experimental data.

Effects of Ion Bombardment on the Spectra of the Edge Photoconductivity and in the Current–Voltage Characteristics of CdS Crystals

Effects of Ion Bombardment on the Spectra of the Edge Photoconductivity and in the Current–Voltage Characteristics of CdS Crystals

Synthesis and Photocatalytic Activity of TiO2/CdS Nanocomposites with Co-Exposed Anatase Highly Reactive Facets.

In this work, TiO2/CdS nanocomposites with co-exposed {101}/[111]-facets (NH4F-TiO2/CdS), {101}/{010} facets (FMA-TiO2/CdS), and {101}/{010}/[111]-facets (HF-TiO2/CdS and Urea-TiO2/CdS) were successfully synthesized through a one-pot solvothermal method by using [Ti4O9]2− colloidal solution containing CdS crystals as the precursor. The crystal structure, morphology, specific surface area, pore size distribution, separation, and recombination of photogenerated electrons/holes of the TiO2/CdS nanocomposites were characterized. The photocatalytic activity and cycling performance of the TiO2/CdS nanocomposites were also investigated. The results showed that as-prepared FMA-TiO2/CdS with co-exposed {101}/{010} facets exhibited the highest photocatalytic activity in the process of photocatalytic degradation of methyl orange (MO), and its degradation efficiency was 88.4%. The rate constants of FMA-TiO2/CdS was 0.0167 min−1, which was 55.7, 4.0, 3.7, 3.5, 3.3, and 1.9 times of No catalyst, CdS, HF-TiO2/CdS, NH4F-TiO2/CdS, CM-TiO2, Urea-TiO2/CdS, respectively. The highest photocatalytic activity of FMA-TiO2/CdS could be attributed to the synergistic effects of the largest surface energy, co-exposed {101}/{010} facets, the lowest photoluminescence intensity, lower charge-transfer resistance, and a higher charge-transfer efficiency.

Silver sulfide as strong catalyst of crystal growth in the chemical transport method

This study demonstrates the catalytic activity of Ag2S in the formation of single crystals. CdS crystals are grown using the chemical transport method with iodine as transporting agent. The gradient temperature is also varied. Then the same syntheses are repeated with the addition of Ag2S in the catalytic amount which leads to the formation of much bigger single crystals of CdS. Obtained products are characterized with PXRD, SEM, EDX, and ICP-MS investigations. It is confirmed that Ag2S is not present in formed crystals, also SEM images show their compositional homogeneity. We conclude that Ag2S acts as strong catalyst of crystal growth.

Effect of morphology transformation on photocatalytic performance of CdS crystal

In this study, multi-shaped CdS was synthesized by hydro- and solvothermal methods. Interestingly, the results of scanning electron microscopy and transmission electron microscopy showed that branch-like CdS could be transformed into ball-like and flake-like in deionized water by ethylenediaminetetraacetic acid and l-cysteine, respectively, and the growth mechanism of CdS was discussed and explored: the ion-binding rate might be the main factor for the morphology transformation of CdS. X-ray diffraction and energy dispersive spectroscopy revealed branch-like CdS which exhibited the hexagonal phase. Besides, the optical characteristics of CdS were performed by ultraviolet–visible and photoluminescence spectrum. Also, CdS was utilized to explore the photocatalytic activity of rhodamine B, and the result showed that the photocatalytic activity of ball-like CdS was higher than flake-like and branch-like CdS.