CdS Composites Research Articles

Zn‒doped and (Sn: Zn) co-doped CdS nanostructures for optoelectronics

Zn doped and Sn:Zn co‒doped CdS semiconductor nanostructured have been fabricated by chemical reaction, then thin film samples have been deposited by pulsed laser method. The coated films have a hexagonal phase as demonstrated by X‒ray (XRD) diffraction with fine Nano-crystallites with crystallite size between (2.6–2.85 nm). The UV–visible test showed good transmittance and obtained energy gap increased for Zn:CdS (3.30 eV) compared to bulk CdS. Electrical examination revealed that some samples have an enhancement in current with increased applied voltage in Sn ions adding to the Zn:CdS composition might be due to adding sub-levels electronic transitions. Morphology characterization was examined by atomic force (AFM) microscopy and was declared that the samples were quite smooth and increased roughness with increased co‒doping ions.

Ternary Memory Behavior of Carbazole‐Based Donor–Acceptor Polymer and CdS NPs Composites

AbstractMulti‐level memory can greatly improve information density, so it has been widely studied. In this study, a carbazole‐based donor–acceptor polymer poly[2,7‐9‐(heptadecan‐9‐yl)‐9H‐carbazole‐alt‐7H‐benzimidazo[2,1‐a]benz[de]isoquinolin‐7‐one] (PCz‐BB) is synthesized, which exhibits flash‐type ternary memory behavior. Further, CdS nanoparticles (NPs) are embedded into the prepared polymer to enhance the storage performance. The current–voltage (I–V) characteristics of memory devices based on PCz‐BB:CdS composites and the effect of the embedding ratio of CdS NPs on the memory devices are studied. It is verified that the ON2/ON1/OFF current ratios of the devices at low CdS embedding concentrations are improved, and the threshold voltages are also reduced. The memory device based on the optimal embedding concentration (3 wt% CdS) exhibits a high ON2/ON1/OFF current ratio of 18631:72:1, a low threshold voltage of −0.40/−1.20 V, and excellent stability. The mechanism of resistive switching is explained by the theory of charge traps and conductive filaments. This work provides a new avenue for high‐performance multi‐level organic electrical storage materials.

Boosting charge transfers in cadmium sulfide nanorods with a few layered Ni-doped MoS2 nanosheets for enhanced photocatalytic hydrogen evolution

The molybdenum sulfide (MoS2) is a promising low-cost photocatalyst aimed at the hydrogen production reactions, however, obtaining a detailed understanding of its catalytic site has proved to be a challenging task. Several studies indicated that the active sites for catalytic reaction are mainly associated with the edge sites of 2D-layered MoS2, and their basal plane (in-plane) displays poor activity toward catalytic reactions. Herein, we established the simple approaches to enhance the activity of MoS2 by conversion of in-plane active sites into active surface edge sites by transition metal (Ni) doping followed by exfoliation. These activated MoS2 was utilized for enormous upgrading of CdS photocatalytic activity for hydrogen production and is roughly 249 mmol h−1 g−1, which is 70 times higher than pure CdS, showed ∼140 h stable H2 production. The amended conductivity, improved surface area and huge active sites are extremely advantageous properties expanded by metal doping to MoS2 and exfoliation. Additionally, another reason for the enhanced activity of Ni–MoS2/CdS system was due to promotion of catalytic kinetics by Ni and Mo sits, they are admirable activity of water dissociation and higher ability of hydrogen adsorption correspondingly. These modifications made of superior photogenerated charge carriers’ separation and migration for effective utilization. As far as we know, this system demonstrates the utmost effective performance among inclusive reported MoS2 based CdS composites. Remarkably, these outcomes will have abundant potential for the progress of immensely actual photocatalytic systems.

Enhanced photocatalytic pure water splitting of porous g-C3N4/CdS composite by the bimetallic phosphide

Here, a novel CoNiP nanoclusters-decorated photocatalyst consisted of porous g-C3N4 (PCN) and CdS were reported for the pure water splitting. Under visible light (λ ≥ 400 nm), the activities and durability for photocatalytic water splitting over the PCN-CdS composite can be importantly improved by CoNiP. And the photocatalytic H2-evolution rate could be maximized to 122.08 μmol g‐1 h‐1 for pure water-splitting through regulating the loading amount of CoNiP and the ratio of Co, Ni and P, which are all larger than those of PCN-CdS, PCN-CdS-Pt, PCN-CdS-Co2P and PCN-CdS-Ni2P. Comparing to the single metal phosphides (Co2P and Ni2P), the higher photocatalytic activities of PCN-CdS enhanced by the bimetallic phosphide (CoNiP) are on account of the extended light absorption, more exposed active sites, the regulated electronic structure, accelerated electrons transfer, the more negative Fermi energy and more trapped electrons in CoNiP. In addition, the PCN-CdS-CoNiP composite exhibits the high stability during the 3 cycling tests for 12 h, due to its stable structure resulted by the reinforced chemical connection between PCN and CoNiP in a form of P+-Pδ--Coδ+/Niδ+, in which the positive charge center (P+) originates from the replacement of C in PCN by P. This research indicates that the bimetallic phosphide could be a promising candidate of precious metals substitutes in photocatalyst system with higher activities.

Application of Vogel–Tamman–Fulcher (VTF) model to CdS–B2O3 glasses

In this paper, we report that the DC electrical conductivity is a very interesting property which provides important information about mechanism in solid. The CdS–B2O3 glasses of different composition were prepared in the laboratory. The conductivity was measure in the temperature 308–473 K. A plot of log σ versus 1/T is drawn for various compositions. From this it observed that electrical conductivity increases linearly with temperature which shows Arrhenius nature for different composition of CdS–B2O3. Activation energy for all samples is laying in the range 0.29–0.82 eV which decreases with mol% of CdS. The decrease in conductivity for greater B2O3 concentrations may be due to reduced segmental motion. The temperature dependence conductivity shows percolative behavior and a clear cross over from Vogel–Tamman–Fulcher to Arrhenius behavior. The adiabatic and non-adiabatic hopping conduction is checked by drawing a plot of log σ versus activation energy at fixed temperature.

Facile fabrication of g-C3N4/CdS heterojunctions with enhanced visible-light photocatalytic degradation performances

The construction of heterojunction used to improve the photocatalytic performance of photocatalyst has attracted much attention in recent years. In this study, we aim to investigate the synergistic effect of g-C 3 N 4 and CdS on photocatalytic degradation of organic dye pollutants. Several g-C 3 N 4 /CdS heterojunctions with different g-C 3 N 4 contents were successfully synthesised via a simple hydrothermal reaction. Experimental measurements on photocatalytic degradation of methylene blue (MB), rhodamine B (RhB) and MB/RhB mixtures were conducted. The photodegradation results indicate that the prepared g-C 3 N 4 /CdS composites all demonstrate remarkable visible-light photocatalytic properties, and this performance is due to the formation of the g-C 3 N 4 /CdS heterojunction structures. Compared with pure g-C 3 N 4 and CdS, the g-C 3 N 4 /CdS heterojunctions not only effectively enhance the absorption of visible light but also significantly inhibit the recombination of photogenerated carriers. Thus, this condition prolongs the lifetime of active species and markedly improves their photodegradation activities. Especially, the 0.04GCS exhibits the best photocatalytic degradation performance on MB, and its degradation rate constant is up to 0.0301 min −1 within the irradiation time of 90 min, which is 9 and 3 times higher than that of the pure g-C 3 N 4 and CdS, respectively. In the meantime, the 0.12GCS also shows excellent photodegradation activity on RhB, and its degradation efficiency is nearly 2.32 and 2.97 times that of the pure g-C 3 N 4 and CdS. The different degradation behaviours of the composite photocatalysts on MB/RhB mixed pollutant were investigated. The possible reaction mechanism of the photocatalytic degradation on organic dyes by the g-C 3 N 4 /CdS heterojunctions was also explored.

Ultrathin layered Zn-doped MoS2 nanosheets deposited onto CdS nanorods for spectacular photocatalytic hydrogen evolution

The utilization of non-precious and noble-metal free catalysts for the photo conversion of water into hydrogen is of significant interest. In particular, the typical layered MoS2 has attracted interest as a low-cost alternative to platinum in the photocatalytic hydrogen evolution system. However, theoretical studies have suggested that the activity of the MoS2 co-catalyst arises only at the S sites on the edges of grains, and not on the basal planes. In this respect, the doping of a foreign metal into the MoS2 system is an interesting method for boosting the hydrogen production rate by increasing the conductivity and number of active sites. Herein, simple methods are used to decorate CdS nanorods with earth-abundant, few-layered zinc-doped MoS2 nanosheets (Zn-MoS2/CdS), and the so-obtained Zn-MoS2/CdS composite is used for the photocatalytic hydrogen evolution reaction under solar irradiation in the presence of lactic acid as a hole scavenger. Thus, the catalyst is shown to provide significant hydrogen generation activity, along with excellent and continuous photo stability for more than 60 h under optimal conditions. Moreover, the hydrogen evolution rate of the Zn-MoS2/CdS composite is up to ~75-fold greater than that of the pure CdS. The loading of Zn-MoS2 is shown to increase the synergistic effects of the photocatalyst due to the effective separation of charge carriers, extensive exposure of catalytic sites, and high dispersion of the few-layered Zn-MoS2. In addition, the stability of the optimized material is enhanced by the doping of Zn metal into the MoS2. To the best of our knowledge, the hydrogen evolution activity of the as-prepared composite is the highest ever reported for the CdS and single metal-doped MoS2-based catalysts. Hence, this type of Zn-MoS2/CdS composite is strongly believed to have great potential as a low-cost, highly-efficient, noble-metal free catalyst for the photocatalytic reduction of water.

MoS2/CdS rod-like nanocomposites as high-performance visible light photocatalyst for water splitting photocatalytic hydrogen production

This study demonstrates a high-performance visible-light-driven photocatalyst for water splitting H 2 production. CdS nanorods (30 nm in diameters) with shorter radial transfer paths and fewer defects were prepared by a solvothermal method. To mitigate the recombination of electrons and holes, MoS 2 nanosheets with rich active sites were modified on the surface of CdS nanorods by a room-temperature sonication treatment. The photocatalytic water splitting tests show that the MoS 2 /CdS nanocomposites exhibit excellent H 2 evolution rates. The highest H 2 evolution rates (63.71 and 71.24 mmol g −1 h −1 in visible light and simulated solar light irradiation) was found at the 6% MoS 2 /CdS nanocomposites, which was 14.61 times and 13.39 times higher than those of the corresponding pristine CdS nanorods in visible light and simulate solar light irradiation, respectively. The apparent quantum efficiency (AQE) of the 6% MoS 2 /CdS nanocomposites at 420 nm was calculated to be 33.62%. The electrochemistry tests reveal that the enhanced photocatalytic activity is a result of extra photogenerated charge carries, greatly enhanced charge separation and transfer ability of the MoS 2 /CdS composites. This study may give new insights for the rational design and facile synthesis of high-performance and cost-effective bimetallic sulfide photocatalysts for solar-hydrogen energy conversion. • CdS/MoS 2 composites were prepared by a room-temperature sonication method. • This material shows excellent photocatalytic H 2 production performance. • The decoration of MoS 2 nanosheets enables to effectively reduce photo-corrosion. • The performance is due to good separation and transfer ability.

Rational design, fabrication, optical properties and high-efficiency visible-light photocatalytic degradation performance for organic pollutants of Eu:Bi2WO6/CdS nanostructures

Over the past few years, semiconductor materials (especially bismuth tungstate) exhibiting unique environment purification and energy conversion capacities arouse huge attention as impacted by issues of environmental pollution and energy shortage, whereas its application is restricted by the problems of high carrier recombination rate and unsatisfactory degradation efficiency. In this study, Eu:Bi 2 WO 6 nanostructures containing Eu ions of different concentrations were synthesized with a chemical solution method, and CdS was generated on the surface of Eu:Bi 2 WO 6 nanostructures in situ epitaxial to synthesize the Eu:Bi 2 WO 6 /CdS composites. The effects of Eu doping concentration on the crystal structure, chemical composition, local structure, optical properties and visible-light photocatalytic properties exhibited by Eu:Bi 2 WO 6 /CdS nanostructures were studied more specifically, and the Eu doping behavior on the improvement mechanisms for optical and photocatalytic performance exhibited by Eu:Bi 2 WO 6 /CdS nanostructures was clarified. The robust PL emission peak at about 390 nm and weak emission peak at nearly 450 nm are attributed to the exciton emission and defect state of Bi 2 WO 6 /CdS nanostructure, respectively. As indicated from the mechanism insights, the reasonable introduction of Eu 3+ could alter the band gap of the photocatalyst, and the epitaxial CdS could decrease the recombination probability of electron and hole in the Bi 2 WO 6 /CdS, while improving the photocatalytic activity. This study supplies new occasions for rational excogitation and better comprehending of atomic-scale complicated structures for applications in numerous fields (e.g., energy and environmental protection).

High-Performance α-Bi<sub>2</sub>O<sub>3</sub>/CdS Heterojunction Photocatalyst: Innovative Design, Electrochemical Performance and DFT Calculation

Heterojunction semiconductor photocatalysis is an auspicious technique for clear up organic pollutants from water, and have been of valuable strategy in the area of photocatalysis. Herein, electrophoretic deposition procedure was used to prepare α-Bi2O3/CdS type-Ⅱ heterojunction photocatalysts. The results of PL, Raman, and EIS show that there is a heterojunction effect in α-Bi2O3/CdS, which is propitious to improve the separation efficiency of photogenerated electron-hole pairs. The DFT calculation reveals that the work function of CdS (4.57 eV) is higher than that of α-Bi2O3 (3.37 eV), which facilitates the migrating of e- from the CB of α-Bi2O3 to the CB of CdS, and the migrating of h+ from the VB of CdS to the VB of α-Bi2O3, thus the e--h+ pairs with high redox ability are retained. The performances were assessed by degrading methyl orange (MO), acid magenta under simulated visible light irradiation. Under simulated visible light irradiation, BC45 composite exhibited the highest degradation efficiency of 87% (MO) and 81% (acid fuchsin) for 4 h, which was about 2 times higher than that of CdS (MO) and (acid fuchsin). It is believed that the dual characteristics of H2O wettability and dye adsorption performance in α-Bi2O3/CdS composites promote photocatalytic process compared with single CdS and α-Bi2O3. The study could provide new insights to develop efficiently capable photocatalysts of the α-Bi2O3/CdS composites.

Bi4Ti3O12/CdS Nanocomposites Enhance the Photocatalytic Degradation Performance

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[Formula: see text]/CdS composites were synthetized by coprecipitation method, which CdS particles selectively deposited on Bi4Ti3O[Formula: see text] 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[Formula: see text]/CdS composites had the highest photocatalytic activity against RhB under visible light, and the degradation rate of RhB was 98.8% after 120[Formula: see text]min of simulated light, 2.14 times that of pure Bi4Ti3O[Formula: see text], and the Bi4Ti3O[Formula: see text]/CdS-10[Formula: see text]wt.% 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 [Formula: see text]O[Formula: see text], h[Formula: see text] and [Formula: see text]OH have effects in the degradation of RhB, and thus suggested a possible mechanism for the photodegradation process of the Bi4Ti3O[Formula: see text]/CdS-10[Formula: see text]wt.% composite photocatalyst.

Effects of Preparation Conditions on the Efficiency of Visible-Light-Driven Hydrogen Generation Based on Cd0.25Zn0.75S Photocatalysts

Photocatalytic H2 production utilizing H2S, an industrial side-product, is regarded as an environmentally friendly process to produce clean energy through direct solar energy conversion. For this purpose, sulfide-based materials, such as photocatalysts, have been widely used due to their good solar response and high photocatalytic activity. In this work, a ZnS–CdS composite was studied, and special attention was dedicated to the influence of the preparation parameters on its H2 production activity. The ZnS–CdS composite, with an enhanced photoactivity for H2 production, was synthesized both from ammine complexes and, in a conventional way, directly from acetates at various pH values. Deviating from the traditional method, the photoactivity of ZnS–CdS prepared from ammine complexes was not affected by the pH. Besides, the hydrothermal treatment and the ammonia content strongly influenced the rate of H2 production in this system. DRS, TEM, SEM, XRD, and quantum yield measurements prove the dependence of the photoactivity of these catalysts on the structural and morphological properties determined by the preparation conditions. The promising photocatalytic efficiency achieved with the application of these ZnS–CdS catalysts, prepared without any metal deposition, encourages further investigations to enhance the rate of hydrogen generation by optimization of the reaction conditions for practical utilization.

Ni-doped CdS porous cubes prepared from prussian blue nanoarchitectonics with enhanced photocatalytic hydrogen evolution performance

In this paper, NixCdyS composite photocatalysts were synthesized by using Ni-doped Cd–Co PBA as the precursor, which retains the advantages of PBA such as porous structure, large specific surface and highly dispersed metal active sites. The photocatalytic hydrogen production performance over NixCdyS is three times higher than that of pure CdS with H2 yield of 8.45 mmol g−1 h−1. The catalyst was analyzed by the UV/Vis absorption spectra, photoluminescence spectra, time-resolved photoluminescence spectra, transient photocurrent responses, electrochemical impedance spectra, Mott-Schottky test, etc. A series of characterization results prove that the electron-hole recombination rate, electrochemical resistance and band gap of nickel-doped CdS composites are obviously smaller than CdS, which are important factors to improve the photocatalytic hydrogen production performance. This work may provide some reference value for the fabrication of other functional materials using PBA as precursors.

Synergistic Promotion Effect of ZnCoS Solid Solution and Co1-xS on Photocatalytic Hydrogen Production of the CdS Composite.

Photocatalytic reactions over effective photocatalysts are attractive to explore clean hydrogen energy from water with the utilization of solar energy. Ternary Co1-xS@ZnCoS/CdS (ZCS/CdS) composites are constructed as photocatalysts through the hydrothermal formation of Co1-xS and ZnCoS nanoparticles on CdS nanorods. Superior to the binary Co1-xS/CdS composite, ZCS/CdS shows the improved photocatalytic activity with a hydrogen production rate of 58.4 mmol·g-1·h-1, which is 31.4 and 2.1 times higher than those of CdS and Co1-xS/CdS, respectively. Different from binary Co1-xS/CdS, the participation of a small amount of zinc favors the formation of ZnCoS solid solution in ZCS/CdS. A synergistic promotion effect of ZnCoS and Co1-xS is confirmed due to tight heterojunctions among Co1-xS, ZnCoS, and CdS in ZCS/CdS. The unique heterostructure of ZCS/CdS benefits its enhanced absorption ability of visible light, accelerating the separation of photoinduced electron-hole pairs and the electron transfer. ZCS/CdS exhibits the strong reduction ability and superior photocatalytic stability due to the role of double Z-scheme electron transfer pathways in the ternary composite. This work provides a suitable way to tune noble metal-free composite photocatalysts for efficient H2 production.

CDs/ZnO composite material with solid state fluorescence performance for quantitative determination of methyl red content and antibacterial properties

A water-soluble probe composite material (CDs/ZnO) was synthesized by microwave pyrolysis methods of citric acid, urea and zinc oxide (ZnO) with aggregation-induced emission activity. We creatively realized the composite of CDs and nano-ZnO in the form of foam, then used as bactericide for the first time and showed excellent antibacterial properties. Also, the composite materials overcame the problem of aggregation-induced quenching (ACQ) and realized solid-state emission. The materials had two different emission centers, and the two emission peaks were varied with the change of excitation wavelength. Furthermore, Methyl red (MR) showed fluorescence quenching for CDs/ZnO with obvious linear correlation, which demonstrated potential in the measurement of MR in dyeing wastewater. The CDs/ZnO we obtained perfectly inherited the advantages of CDs and nano ZnO, it has not just no cytotoxicity to cells, but also has a good killing effect on bacteria. Hence, this work shows significant adaptable fluorescence-based protocol with enormous potential applications in biology.

Bimetallic MOF-Derived Sulfides with Heterojunction Interfaces Synthesized for Photocatalytic Hydrogen Evolution

The synthesis of highly efficient and stable CdS composites without noble metals has become a hotspot in the photocatalytic field. Although NiS is an ideal candidate, it remains a challenge to optimize the combination of NiS and CdS to improve the photocatalytic activity for hydrogen evolution. Herein, we have successfully synthesized a CdS@NiS photocatalyst using bimetallic metal–organic frameworks (MOFs) as the precursor. The formation of bimetallic Cd/Ni-MOFs can lead to well-contacted heterogeneous interfaces between CdS and NiS at the nanoscale, efficiently promoting the separation of photogenerated carriers and boosting electron interface transfer. The obtained results demonstrated that CdS@NiS exhibits a high photocatalytic hydrogen evolution rate of 42.7 mmol·g–1·h–1, and the corresponding apparent quantum yield reaches 13.23% at 450 nm, superior to those obtained using the traditional simple physical mixing methods. This work provides a promising strategy for the design of new photocatalysts for hydrogen evolution.

Photocatalytic reduction of uranium(VI) under visible light with 2D/1D Ti3C2/CdS

• Visible-light-driven photoreduction of U(VI) is achieved without any sacrificial agents. • Ti 3 C 2 in 2D/1D Ti 3 C 2 /CdS composites acts as a Janus co-catalyst. • A high U(VI) extraction capacity of 500 mg/g was obtained in 40 min. • The Ti 3 C 2 /CdS composites keep high performance in wide pH range. Herein, for the first time, the visible-light-driven 2D/1D Ti 3 C 2 /CdS nanorods composites were fabricated by electrostatic assembly strategy to achieve efficient uranium(VI) photoreduction without any sacrificial agents. While CdS is the main catalyst, Ti 3 C 2 in the composites acts as a Janus co-catalyst for the photoreduction of uranium(VI), in view of the fact that it can simultaneously enhance the photocatalytic performance and the stability of CdS. With the initial uranium(VI) concentration at 50 ppm, 97% uranium(VI) reduction efficiency was achieved by the optimal Ti 3 C 2 /CdS composites during 40 min visible light irradiation without any sacrificial agents. The kinetic reaction rate reaches as high as 1520 μmol/(g·h). Meanwhile, the Ti 3 C 2 /CdS composites keep high performance regardless of acidic, neutral and alkali conditions. The findings of this work highlight the vast opportunities for Ti 3 C 2 /CdS composites in the treatment of radioactive wastewater.

Preparation of Si–α-Fe2O3/CdS composites with enhanced visible-light photocatalytic activity for p-nitrophenol degradation

Si–hematite (α-Fe2O3) nanosheets with highly exposed (110) facets were obtained first, and Si–α-Fe2O3/CdS composites were developed using a well-designed hydrothermal method. The prepared Si–α-Fe2O3/CdS composites showed enhanced visible-light photocatalytic activity compared with Si–α-Fe2O3 and CdS. The construction of the Si–α-Fe2O3/CdS heterojunction can inhibit the recombination of the photogenerated electron–hole pairs on the catalyst surface effectively. The synergistic effects of the photo-Fenton and the heterojunction promoted the production of the active species in the Si–α-Fe2O3/CdS system and enhanced the photocatalytic degradation activity under visible-light irradiation. The SFC-1:1 composite exhibited the highest photocatalytic activity toward p-nitrophenol degradation. The photocatalytic degradation mechanism was also investigated.

Altering NH4OH concentration in producing chemical bath deposited CdS to steadily support electrodeposited CdTe

Development of chemical bath deposited (CBD) CdS to steadily support the electrodeposited (ED) CdTe, by changing the volume of NH4OH, a pH adjuster, in the CBD bath is reported here. The optimal volume of NH4OH, which is the controlling parameter of interest, was identified based on the optical, electrical, structural, and morphological properties of the CdS developed. The sample developed exhibits the band gap energy of 2.32 eV with light transmittance >80% (500–900 nm). The photo-electrochemical cell and Mott-Schottky studies revealed n-type conductivity, open circuit voltage (VOC) of 0.529 V, and short circuit current density (JSC) of 12.290 μA/cm2 at the CdS/electrolyte junction while the X-ray diffraction data and phase analysis revealed the formation of a blended hexagonal/cubic structures. Further, the scanning electron microscopic and the energy-dispersive X-ray spectroscopic studies elucidated a well-compact grain arrangement and agreed with the theoretical chemical composition (1:1) of CdS respectively.

White photoluminescence emission using CdS + CdCO3 composite thin films

The optical properties of CdS + CdCO3 composite thin films prepared by the chemical bath method on glass substrates, at different bath-temperatures (Tb) in the interval 20–80 °C, are reported. Chemical bath method allows to produce CdS + CdCO3 composite films controlling their composition through bath temperature. For Tb = 80 °C CdS is mainly produced, for 20 °C ≤ Tb ≤ 70 °C a composite of CdS + CdCO3 is formed in the films, while at Tb = 20 °C a predominantly CdCO3 in the bulk of the films along with nanostructured CdS (5 ± 2 nm size) is obtained. X ray diffraction patterns shown that CdS grows in the cubic zinc blende phase and CdCO3 in the rhombohedral structure; CdS and CdCO3 grow simultaneously and independently, but Raman measurements indicate how the proportion between CdS and CdCO3 depends on Tb. Optical absorbance spectra allow to assign an indirect transition for CdCO3 at 3.10 ± 0.03 eV when Tb = 20 °C and 2.80 ± 0.04 eV for 70 °C. Direct band gap values in the 2.50–2.80 eV interval were calculated for the seven CdS samples prepared across the entire Tb range. The CdS average crystallite size varied from 5 nm to 35 nm as Tb changed from 20 to 80 °C. The PL spectra show similar bands in the 1.6–2.9 eV (775 - 430 nm) interval indicating PL emissions are originated in CdS nanocrystals and probable defect states in CdCO3. The production of composite material with a major proportion of CdCO3 promotes the nucleation of CdS nanocrystals, at relative low temperatures, with an effective coupling improving emission properties of the films.