Crystalline Cadmium Sulfide Research Articles

Swift heavy ion irradiation induced modifications in electron beam deposited CdS thin films

The field of tailoring the physio-chemical properties by the way of radiation leads to the immense opportunities in the domain of advanced photonics and optoelectronic devices. In the present contribution, 120 MeV silver ions (Ag9+) induce electronic excitations which instigate modifications in crystalline cadmium sulphide (CdS) thin films deposited via electron beam evaporation are examined. X-ray Diffraction (XRD) reveals that the peak intensity and FWHM get affected as a consequence of swift heavy ions (SHI) irradiation while crystal phase remains preserved even after irradiation. Raman analysis exhibits the asymmetry in the fundamental longitudinal optical (LO) phonon mode which is directly related to the surface defects, reduction in particle size, and amorphization after irradiation. Field emission scanning electron microscopy (FESEM) images exhibit the reduction in particle size followed by highly strained as-deposited samples get stabilize with the deposited energy. The spherical shaped nanoparticles are observed for as-deposited and irradiated films through atomic force microscopy (AFM) and also, declared the nano-grain formation as resulted from negative surface tension induced at higher fluences. Photoluminescence (PL) spectra indicate the electronic excitations inspired additional yellow band due to generation of ICd-Vcd Frenkel pair defects along with the green and red emission.

Microwave-assisted solvothermal in-situ synthesis of CdS nanoparticles on bacterial cellulose matrix for photocatalytic application

Bacterial cellulose (BC) is a unique nanofibrous biomaterial, and crystalline cadmium sulphide (CdS) is regarded as one of the most attractive visible light-driven photocatalysts. In this study, a BC@CdS nanocomposite for photocatalytic degradation of organic dye methylene blue (MB) was prepared with a facile and highly efficient strategy. The nanocomposite was prepared through a designed “anchoring-reacting-forming” pathway. SEM images showed that the BC-alcogel was the best matrix for nano-fabrication on which nanosized CdS particles were homogeneously distributed (approximately 100 nm). The results from FT-IR, XRD and XPS revealed that the CdS nanoparticles, mainly cubic and hexagonal crystallite, are attached to the BC fibers via coordination effect. The BC-supported adsorbent photocatalytic material was easy to be recycled and followed a new “adsorption–accumulation–degradation” mechanism of photocatalytic degradation. The results showed BC matrix had a strong adsorption effect on MB molecules, which improved local concentration of MB and promoted the rate of photocatalytic reaction. This novel adsorbent photocatalytic nanocomposite material (contained 12.4% CdS, about 0.91 mg for degradation experiment) possessed highly efficient photocatalytic activity with 77.39% removal of MB after 180 min visible light irradiation (the degradation rate was 28.3% mg−1 h−1), and exhibited satisfactory cyclic utilization with slight attenuation. Therefore, BC@CdS nanocomposite is a novel promising candidate as adsorbent photocatalysts with visible light response.

Enhanced anharmonic phonon coupling and decay dominated by low‐energy phonons in CdS nanowires

AbstractLow‐energy optical phonons with energy in the order of that of acoustic phonons are readily populated at room temperature, and therefore, they play a key role in thermal, electronic, and thermo‐electric fundamental processes in a solid material. High‐quality crystalline cadmium sulfide (CdS) nanowires with a diameter of several tens of nanometer and a length up to several micrometers (3–5 μm) demonstrate strong exciton–phonon coupling. This strong coupling interaction allows us to observe low‐energy optical phonons and their anharmonic couplings to high‐energy phonon modes. In this study, second and higher order multiphonons related to the phonon were observed in near resonance Raman scattering condition (excitation wavelength of 532 nm). The clear observation of the multiphonon modes makes it possible to study composite phonon anharmonic decay. The experimental results show that low‐energy phonons (both optical and acoustical) dominate anharmonic phonon decay in CdS.

Effect of temperature on structural and optical properties of solvothermal assisted CdS nanowires with enhanced photocatalytic degradation under natural sunlight irradiation

Photocatalytic degradation of toxic dyes is an important topic across the globe. This paper reports the photocatalytic degradation of methylene blue (MB) dye using cadmium sulfide (CdS) nanowires as a photocatalyst under natural sunlight irradiation. The CdS nanowires were successfully synthesized by a solvothermal route using ethylenediamine as a solvent with a series of different reaction temperature from 160 to 200 °C for a fixed time of 24 h. Multiple characterization techniques were used to investigate the structural, morphology, optical and photocatalytic study of as-synthesized CdS samples. The XRD patterns reveal highly crystalline CdS nanomaterials with a hexagonal crystal structure. The FESEM and HRTEM observations clearly confirmed a large number of uniform nanowires grown in different directions and interconnected with each other. The stoichiometric ratio of Cd:S is almost 1:1, confirmed by EDS analysis. Room temperature PL spectra of CdS nanowires exhibit a narrow emission at a wavelength of 512 nm. The CdS nanowires synthesized at 200 °C shows the excellent photocatalytic performance with highest photodegradation efficiency has reached up to 98.75% within 20 min, under sunlight irradiation. The 93.06% and 89.10% photodegradation efficiency were observed in CdS nanowires synthesized at 180 °C and 160 °C, respectively. From these result, it is observed that the crystallite size and morphology of CdS nanowires are the influence factors for the photodegradation efficiency of MB dye. Furthermore, the mechanism of MB dye photodegradation using CdS nanowires was discussed. These CdS nanowires with high photocatalytic activity can be used for future in water pollutant degradation.

Visible light driven photocatalytic degradation of ofloxacin and malachite green dye using cadmium sulphide nanoparticles

This work demonstrates an effective approach for the degradation of persistent and mutagenic water pollutants under visible light illumination. Cadmium sulphide (CdS) was synthesized using a facile hydrothermal approach and its structural, morphological and optical properties were evaluated by various techniques such as XRD, FTIR, UV-DRS, TGA/DSC, HRTEM and EDX. The XRD spectrum indicated that the synthesized CdS was a crystal mixture of cubic and hexagonal phases. HRTEM images displayed the formation of well crystalline CdS nanoparticles, grown in high density. Further, the synthesized CdS nanoparticles were effectively used as photocatalyst for the degradation of fluoroquinolone antibiotic (ofloxacin) and mutagenic water pollutant (malachite green) under visible light irradiation. Role of hydroxyl radicals (OH) in the photocatalytic process was confirmed by terephthalic acid photoluminescence (TA-PL) technique. Degradation efficiency of about 79.5% and 96% was obtained for ofloxacin and malachite green in the reaction time of 80 and 60min, respectively. It was found that photocatalytic degradation of both compounds i.e. drug and dye followed pseudo first order reaction kinetics.

One-dimensional CdSxSe1−x nanoribbons for high-performance rigid and flexible photodetectors

High quality one-dimensional single crystalline cadmium sulfide selenide (CdSxSe1−x) nanoribbons were synthesized and fabricated as the high-performance rigid and flexible photodetectors.

Absorption of Light by Free Charge Carriers in the Crystalline CdS Under Intense Electron Irradiation

The process of light absorption by free electrons in the crystalline cadmium sulfide under irradiation by a nanosecond electron beam with the current density of 8–100 A/cm2 is studied. A superlinear increase in optical absorption is observed if the beam current density is increased from ~8 to 12 A/cm2. The nature of light absorption by thermalized electrons corresponds to the scattering on lattice defects. An increase in the exponent of the power dependence of light absorption on the wavelength with increasing beam current density is associated with the single and double ionization of donors and acceptors. It is concluded that accumulation of charge carriers occurs without capture by traps due to their impact ionization by secondary electrons, whose energy in the thermalization stage is comparable with the band gap of the crystal. According to the results of calculations, the capture cross section of electrons by holes at quadratic recombination is ~10–20 cm2, the Auger recombination coefficient is ~10-31 cm6∙s–1, and the charge carrier concentration is ~1.3∙1018–1.5∙1019 cm–3.

Novel synthesis of biologically active CdS nanoclusters in cell-mimicking vesicles

ABSTRACTStable cadmium sulphide (CdS) nanoclusters have been synthesised in non-ionic surfactant vesicles (niosomes). The nanocluster characteristics show strong dependence on the Cd2+ precursor concentration. At low precursor concentration, aggregates comprising fine nanocrystals of CdS with diameter 2–5 nm are formed. At high precursor concentrations, crystalline CdS nanoclusters (15–20 nm in diameter) are formed. Interestingly, these nanoclusters reside exclusively in the vesicular bilayer. Moreover, these nanoclusters are highly photoluminescent and exhibit cytotoxicity towards cancerous HeLa cells. As the vesicular bilayer mimics the cell membrane, the present work is extremely relevant to the use of the CdS nanoclusters for diagnostic and therapeutic purpose.

Facet-Selective Epitaxy of Compound Semiconductors on Faceted Silicon Nanowires.

Integration of compound semiconductors with silicon (Si) has been a long-standing goal for the semiconductor industry, as direct band gap compound semiconductors offer, for example, attractive photonic properties not possible with Si devices. However, mismatches in lattice constant, thermal expansion coefficient, and polarity between Si and compound semiconductors render growth of epitaxial heterostructures challenging. Nanowires (NWs) are a promising platform for the integration of Si and compound semiconductors since their limited surface area can alleviate such material mismatch issues. Here, we demonstrate facet-selective growth of cadmium sulfide (CdS) on Si NWs. Aberration-corrected transmission electron microscopy analysis shows that crystalline CdS is grown epitaxially on the {111} and {110} surface facets of the Si NWs but that the Si{113} facets remain bare. Further analysis of CdS on Si NWs grown at higher deposition rates to yield a conformal shell reveals a thin oxide layer on the Si{113} facet. This observation and control experiments suggest that facet-selective growth is enabled by the formation of an oxide, which prevents subsequent shell growth on the Si{113} NW facets. Further studies of facet-selective epitaxial growth of CdS shells on micro-to-mesoscale wires, which allows tuning of the lateral width of the compound semiconductor layer without lithographic patterning, and InP shell growth on Si NWs demonstrate the generality of our growth technique. In addition, photoluminescence imaging and spectroscopy show that the epitaxial shells display strong and clean band edge emission, confirming their high photonic quality, and thus suggesting that facet-selective epitaxy on NW substrates represents a promising route to integration of compound semiconductors on Si.

Electrical, electrochemical and photo-electrochemical studies on the electrodeposited n-type semiconductor hexagonal crystalline CdS thin film on nickel substrate

Electrodeposited cadmium sulfide (CdS) on nickel substrate of new properties from aqueous solutions of Cd2+ and S2O3 2− at 313 K has been obtained using cyclic voltammetric and potentiostatic techniques. The mechanism of the electrode reactions for the electrodeposition of CdS has been evaluated and proposed. Energy dispersive X-ray florescence elemental analysis and X-ray diffraction investigations demonstrate that, the electrodeposited CdS is pure and hexagonal polycrystalline in nature, at our optimal conditions. Furthermore, the electrodeposited CdS is of n-type semiconductor was investigated and confirmed by Mott–Schotky test. Donor concentration (ND) was determined to be 1.0 × 1017 cm−3. In this research we discovered that, the electrodeposited semiconductor CdS on Ni substrate has low resistivity and magnetic properties (became as a strong magnet) at the mentioned conditions. The photoelectrochemical measurements of the electrodeposited CdS on nickel electrode had been investigated at room temperature and under illumination giving good results.

Characterization of single crystalline CdS nanowires synthesized by solvothermal method.

Cadmium sulfide (CdS) nanowires with uniform diameter were prepared by the solvothermal method using ethylenediamine (en) as solvent. The products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scan electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). It was found that the products are hexagonal crystals of CdS nanowires with diameter of 28 nm and length up to several micrometres. Selected area electron diffraction (SAED) and high resolution TEM (HRTEM) studies indicate the single-crystalline nature of CdS nanowires with an oriented growth along the c-axis direction. The absorption spectrum of the as-prepared CdS nanowires shows an absorption peak of around 485 nm. These CdS nanowires exhibit bright photoluminescence (PL) with two distinct emission bands at 502 nm and 696 nm.

Microstructural and optical characterizations of highly stable nanospheres of crystalline CdS via selective approach

A novel and selective approach to obtain highly stable and capping nanospheres of crystalline cadmium sulfide (CdS) via solution growth in cadmium nitrate tetrahydrate-thiourea-ligand-pH buffer systems using a Taguchi experimental design is presented. CdS characterization is carried out by laser diffraction particle size analyzer, X-ray diffraction, scanning electron microscope/energy dispersive X-ray spectroscopy, and UV-Vis absorption spectroscopy. Synthesized nanospheres of crystalline CdS with an average crystal particle diameter of 37.5 nm and a capping layer thickness of 17.7–35.7 nm (73 to 115 nm as capped nanoparticles) keep size and form stable in aqueous solution. These crystalline CdS nanospheres exhibit a 2.46 eV band gap, as well as, an optical bandwidth comprises in the visible range with potential applications in solar cells.

Morphological variations in cadmium sulfide nanocrystals without phase transformation

A very novel phenomenon of morphological variations of cadmium sulfide (CdS) nanorods under the transmission electron microscopy (TEM) beam was observed without structural phase transformation. Environmentally stable and highly crystalline CdS nanorods have been obtained via a chemical bath method. The energy of the TEM beam is believed to have a significant influence on CdS nanorods and may melt and transform them into smaller nanowires. Morphological variations without structural phase transformation are confirmed by recording selected area electron diffraction at various stages. The prepared CdS nanorods have been characterized by X-ray powder diffraction, TEM, UV-Vis spectroscopy, and photoluminescence spectroscopy. The importance of this phenomenon is vital for the potential application for CdS such as smart materials.

Coarsening of extracellularly biosynthesized cadmium crystal particles induced by thioacetamide in solution

A novel coarsening route for extracellularly biosynthesized cadmium nanocrystals was investigated for the first time. In this process, the white rot fungus Coriolus versicolor was employed to take up cadmium ions and synthesize extracellular cadmium crystal particles. The coarsening of the particles was induced by thioacetamide under certain conditions. Scanning electron microscopy showed that the formed cadmium crystal particles were coarsened from about 100 nm to 2–3 μm. The corresponding energy-dispersive X-ray spectra confirmed the presence of proteins in the particles. The maximum removal efficiency of Cd(II) increased from 17% to 87%, and the corresponding sorption capacity of biomass increased from 4 to 24 mg g −1 with the completion of the coarsening process. The properties of the coarsened particles were also examined using X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD analysis of fungal mycelial pellets embedded with the coarsened particles confirmed the formation of cubic crystalline cadmium sulfide particles. The TEM results suggest that the coarsened particles were composed of clusters of several smaller particles. The changes in the functional groups on the biomass surface were studied through Fourier transform infrared spectroscopy. Based on the results above, a possible mechanism for the formation and coarsening of cadmium crystal particle is also discussed.

Single Crystalline Cadmium Sulfide Nanowires with Branched Structure

In this article, we report the synthesis of branched single crystal CdS nanowires. This branched CdS nanostructure is prepared by a simple surfactant-directing method, which is of particular interest as it uses readily available reagents and provides a convenient route to high-yield single crystal nanowires but with branched shape. These branched nanowires have an average diameter of about 40 nm and length up to several micrometers. A possible mechanism has been proposed and the addition of surfactant dodecylthiol into the two mixed-solvents would play an importance effect on the structure of the product. Based on the mechanism, by controlling the synthesis conditions, such as the ratios between the surfactant, inorganic solvent, and organic solvent, other kinds of nanostructures based on CdS nanowires were also prepared. Photoluminescence (PL) measurement reveals that the branched CdS nanowires have a strong emission at about 700 nm which might be due to its special structure.

Synthesis of single crystalline CdS nanorods by a PVP-assisted solvothermal method

A wide range of cadmium sulphide (CdS) 1-D nanocrystals were prepared using a novel polyvinylpyrrolidone (PVP)-assisted solvothermal method that employed ethylenediamine (en) as the solvent. X-ray diffraction (XRD) results shows that the nanorods are of hexagonal structure, and are further identified as single crystalline in selected area electron diffraction (SAED). The optical properties of CdS were characterized by optical absorption spectra and photoluminescence spectra. A series of experiments were carried out with different concentrations of PVP, and all the results confirm that the dosage of PVP is a vital factor in the morphology and optical properties of CdS. Moreover when the best dosage of 0.8 g/50 mL was used, continuous single-crystalline nanorods with regular and smooth morphology were obtained. The mechanism for the PVP-assisted solvothermal synthesis of CdS 1-D nanostructures was also investigated, and the reaction model of CdS/PVP was first presented.

Single crystalline CdS nanorods fabricated by a novel hydrothermal method

Cadmium sulphide (CdS) nanorods have been prepared by a novel thioglycolic acid assisted hydrothermal method. X-ray diffraction shows that the nanorods are of hexagonal structure, and high-resolution transmission electron microscopy further identifies that the CdS nanorods are single crystalline in nature. The optical properties of CdS nanorods were characterized by ultraviolet–vis and photoluminescence spectra. Furthermore, the mechanism for the TGA assisted hydrothermal synthesis of CdS nanorods has been preliminary presented.

Preparation of Nanosized Crystalline CdS Particles by the Hydrothermal Treatment

We report studies of the effect of hydrothermal treatment on physical properties such as crystalline phase, size, and morphology of nanosized cadmium sulfide (CdS) particles. CdS precipitates have been synthesized by the reaction of Cd(NO3)2 with Na2S at room temperature. These CdS precipitates have been hydrothermally treated in the range 120–240°C with variation of the treatment time. The effects of acid catalysts and other additives were also investigated. The particles prepared were characterized by XRD, TEM, and BET methods. With increased hydrothermal treatment temperature and time, crystallization from amorphous to crystalline form, cubic or hexagonal, and an increase of particle size occurred. CdS particles of well-developed hexagonal form were obtained at a hydrothermal treatment temperature of 240°C; the primary hexagonal grain size was on the order of 20–30 nm. The addition of an acid catalyst, HCl, or of Cd(NO3)2 into the precipitate sol promoted crystal growth and phase transformation during the hydrothermal treatment, but another additive, Na2S, showed the opposite trend. It appears that hydrothermal treatment combined with proper additives could be an effective method for preparation of nanosize crystalline CdS particles.

Structural and Electronic Properties of Cadmium Sulfide Clusters

Crystalline cadmium sulfide is a semiconductor for which the wurtzite and zinc blende structures are energetically almost degenerate. Due to quantum-confinement effects, it is possible to tune the optical properties of finite cadmium sulfide clusters by varying their size. Here, we report results of a theoretical study devoted to the properties of stoichiometric CdnSn clusters as a function of their size n. We have optimized the structure, whereby our initial structures are spherical parts of either of the two crystal structures, and we have studied systems with up to almost 200 atoms. The calculations were performed by using a simplified LCAO-DFT-LDA scheme. The results include the structure, electronic energy levels (in particular the frontier orbitals HOMO and LUMO), and stability as a function of size. The results allow for a unique definition of a surface region. The Mulliken populations indicate that the bonds within this region are more ionic than in the bulk. Furthermore, whereas the HOMO is delocalized over major parts of the nanoparticle, the LUMO is a surface state, which confirms recent experimental findings. Finally, the relative stability of the zinc blende and wurtzite structures is strongly dependent on the size of the system, and there is a close connection between the HOMO-LUMO energy gap and stability.

Disulfide disproportionation and CdS formation upon cadmium sorption on FeS 2

Adsorption reactions are important for understanding the distribution of ions between aqueous and solid phases; they govern solution concentrations, bioavailability, and mobility of ions in the environment. Iron disulfide is a sorbent of cadmium in reduced systems but sorption on sulfides is not well understood. The purpose of this research is to determine the surface structures and products of cadmium sorbed on amorphous FeS 2. Raman spectroscopy, x-ray diffraction, electron microscopy, and scanning tunneling microscopy were used to study the disulfide surface. The FeS 2 undergoes surface reconstruction and disproportionation during cadmium sorption, which leads to discrete zones of elemental sulfur, cadmium sulfide, and iron hydroxide. Therefore, simple surface complexation is not the predominant mechanism of sorption. Disproportionation may provide a mechanism for the surface to reorganize and for isolated crystalline cadmium sulfide domains to develop. Cadmium surface precipitates are very stable and their formation may be a significant means of attenuating this hazardous element. Thus, it appears that FeS 2 may be an important sorbent of cadmium in natural environments.