CdS Nanowires Research Articles

Dynamically Monitoring the Photodeposition of Single Cocatalyst Nanoparticles on Semiconductors via Fluorescence Imaging.

Loading of cocatalysts through photodeposition has been considered as one of the most promising methods to improve the photocatalytic activities of semiconductors, because of the advantages of intimate contact, easy preparation, and site-directed loading. While extensive efforts have been made to characterize the cocatalysts after synthesis, the growth kinetics of cocatalysts during photodeposition is largely a black box, thus leading to relatively empirical optimizations on the loading strategies of cocatalysts to date. Herein, we dynamically imaged the photodeposition of single cocatalysts on semiconductors via a wide-field fluorescence (FL) microscope, utilizing g-C3N4 sheets and CdS nanowires as models. This capability was based on the quenching effect of cocatalysts on the intrinsic FL emission of semiconductors. Single cocatalyst study revealed that FL emission of photocatalysts decayed monoexponentially during photodeposition, and cocatalysts possessed a self-limited growth. The significant heterogeneities (differences) of cocatalysts during photodeposition were also uncovered, regarding the apparent induction time, deposition rate and FL quenching amplitude. These informations were difficult to be accessed using the ex situ characterization. Programmable photodeposition and dissolution of CoxP were also realized, utilizing a focused laser beam with a spot size of <1 μm. This work explored the hidden details of the growth of cocatalysts during photodeposition, opening up a new avenue to optimize photodeposition for rationally designing more efficient photocatalysts.

Nanoscale X-ray detectors based on individual CdS, SnO[formula omitted] and ZnO nanowires

The development of nanoscale X-ray sensors is of crucial importance to achieve higher spatial resolution in many X-ray-based techniques playing a key role in materials science, healthcare, and security. Here, we demonstrate X-ray detection using individual CdS, SnO2, and ZnO nanowires (NWs). The NWs were produced via vapor–liquid–solid technique and characterized using X-ray diffraction, scanning, and transmission electron microscopy. Electrical measurements were performed under ambient conditions while exposing two-terminal NW-based devices to X-rays generated by a conventional tungsten anode X-ray tube. Fast and stable nanoampere-range X-ray beam induced current (XBIC) in response to X-ray illumination was observed. The high XBIC measured in the NW devices could be attributed to the efficient transport and collection of generated charge carriers due to the single-crystalline nature of NWs and the short NW length. Such fast-response and high-sensitivity nanoscale X-ray detectors can find applications in sub-micron resolution imaging and nanofocused beam shape measurements.

Aggregation induced emission (AIE) materials based on diketopyrrolopyrrole chromophore for CdS nanowire solar cell applications

We designed and synthesized two diketopyrrolopyrrole (DPP) derivatives (DPP1 and DPP2) which are substituted with phenyl and thiophene moieties in between DPP core and merocyanine dyes, respectively. The introduction of thiophene ring subunit at core position endows DPP2 significantly alters the photophysical, electrochemical and aggregation induces enhanced emissive (AIEE) properties compared to those of DPP1. As a practical point of view, we successfully employed DPP1 and DPP2 as sensitizer on CdS nanowires for fabrication of dye sensitized solar cell (DSSCs). The DSSC based on DPP2 (0.268%) dye yielded higher power conversion efficiency (PCE) as compared to DPP1 (0.195%) under standard illumination of Sunlight (AM 1.5 G, 100 mW/cm2). The basis for this different behaviour has been discussed.

Optically-controlled resistive switching effects of CdS nanowire memtransistor* *Project supported by the National Natural Science Foundation of China (Grant No. 51702245) and the Fundamental Research Funds for the Central Universities, China (Grant No. WUT2020IB010).

Since it was proposed, memtransistors have been a leading candidate with powerful capabilities in the field of neural morphological networks. A memtransistor is an emerging structure combining the concepts of a memristor and a field-effect transistor with low-dimensional materials, so that both optical excitation and electrical stimuli can be used to modulate the memristive characteristics, which make it a promising multi-terminal hybrid device for synaptic structures. In this paper, a single CdS nanowire memtransistor has been constructed by the micromechanical exfoliation and alignment lithography methods. It is found that the CdS memtransistor has good non-volatile bipolar memristive characteristics, and the corresponding switching ratio is as high as 106 in the dark. While under illumination, the behavior of the CdS memtransistor is similar to that of a transistor or a memristor depending on the incident wavelengths, and the memristive switching ratio varies in the range of 10 to 105 with the increase of the incident wavelength in the visible light range. In addition, the optical power is also found to affect the memristive characteristics of the device. All of these can be attributed to the modulation of the potential barrier by abundant surface states of nanowires and the illumination influences on the carrier concentrations in nanowires.

S-scheme carrier kinetic pathway constructed by covalent-anion channels in self-assembled cadmium/rhenium sulfide hybrids for efficient Cr(VI) reduction

Exploring photocatalysts to accelerate heavy metal Cr(VI) photoreduction is of great significance. Different from traditional strategies, this work proposes a simple and feasible strategy to construct cadmium/rhenium sulfide (CdS/ReS2) S-scheme heterojunctions for enhancing carrier separation through a covalent-anion-driven self-assembling approach. Herein, the construction of internal electric field induced by an atomic-hybridization at CdS/ReS2 interface drives the photoexcited electrons from one-dimensional CdS nanowires to two-dimensional ReS2 nanosheets upon light irradiation, resulting in the formation of an S-scheme carrier kinetic pathway, which enables the separation of electron-hole pairs to accelerate Cr(VI) photoreduction. As a result, the reduction reaction of CdS/ReS2 heterojunction is increased about 11.4 and 24.3 times compared to pristine CdS and ReS2. Our findings provide a new insight in regulating carrier transfer pathway and designing new-type photocatalysts.

Enhanced catalytic activity of one-dimensional CdS @TiO2 core-shell nanocomposites for selective organic transformations under visible LED irradiation

In this study, we are interested in the photocatalytic activity under visible LED irradiation of one- dimensional (1D) CdS @TiO2 core–shell nanocomposites (CSNs) prepared through a facile and convenient method. For the synthesis of 1D CdS@TiO2 core/shell structure, titania source (Tetrabutyl titanate) was hydrolyzed by water vapor transmission on the surface of CdS nanowires (NWs) which were prepared via solvothermal method. The characterization of 1D CdS@TiO2 core–shell nanocomposites (CdS@TiO2 CSNs) was performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis spectroscopy, and UV–Vis diffuse reflectance spectroscopy (DRS). The as-synthesized sample was utilized for the selective reduction of nitro compounds to benzimidazole and anilide, and also the reduction of benzophenones to alcohol under blue LED irradiation. The 1D CdS@TiO2 CSNs exhibited enhanced photoactivity compared with the pure TiO2, CdS nanowires and commercial TiO2-P25. The excellent reusability of the photocatalyst was examined for six runs. The results demonstrated that the prepared sample has the potential to provide a promising visible light-driven photocatalyst for other organic transformations.

Development of excellent and novel flowery zirconia/cadmium sulfide nanohybrid electrode: For high performance electrochemical supercapacitor application

The energy storing devices such as batteries as well as super-capacitors are limited due to poor electrochemical performance and less cycling stability of electrode materials. To achieve significantly high performance and stability which are critical criteria for examining an electrode material for supercapacitor applications, the production of nanostructured materials for improving specific surface area and electrical conductivity is very crucial. In present work, simple and economical coprecipitation route is used to synthesize ZrO2/CdS nanohybrid. Structure, chemical composition, oxidation state and morphology of the synthesized materials i.e. ZrO2, CdS and ZrO2/CdS nanohybrid were seasoned via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), transmission electron microscopy (TEM), respectively. Energy dispersive x-ray spectroscopy (EDX) was used to confirm the elemental composition of all prepared materials. The incorporation of CdS nanowires in ZrO2 sheets improves the morphology of the nanohybrid. Due to improved morphology, the nanohybrid (ZrO2/CdS) showed a remarkable stability (2000 cycles), specific capacitance (1391F/g) and specific energy (48.27 Wh/Kg) at a current density of 2.5A/g measured via three electrode galvanostatic charge discharge (GCD) system. Additionally, extraordinary electrochemical performances of ZrO2/CdS nanohybrid have remarkable technological applications in future.

Enhanced PEC Water Splitting Performance of Silver Nanoparticle-Coated CdS Nanowire Photoanodes: The Role of Silver Deposition

In this work, Ag@CdS nanowires (NWs) were fabricated via a facile hydrothermal route and magnetron sputtering. The structure and morphology of the Ag@CdS NWs were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photon spectroscopy. The synthesized Ag@CdS NWs exhibit an enhanced light sensitizing ability due to plasmon-enhanced absorption at the Ag and CdS interface. The Ag@CdS NW photoanode exhibits superior light harvesting and photoelectrochemical performance with an optimal photocurrent density of about 6.15 mA/cm2 at a 0.18 V bias versus the saturated calomel electrode (SCE) and a photocurrent density of about 4.7 times compared to that of the pure CdS NW photoanode. The photochemical conversion efficiency calculated for Ag(45 s)@CdS NWs is found to be 6.6% (potential vs SCE at 0.12 V) compared to 1.28% for CdS NWs at the same potential. The H2 generation obtained from the Ag(45 s)@CdS NW photoanode is 1.8 times higher than that from the pure CdS NW photoanode.

Metallic CuS decorated CdS nanowires for efficient photocatalytic H2 evolution under visible-light irradiation

Visible-light-driven photocatalysis holds a broad prospect for alleviating the energy crises. Here we report novel CuS nanoparticles/CdS nanowires Schottky heterojunctions via a two-step hydrothermal synthesis and used for photocatalytic H2 generation driven by visible-light (λ ≥ 420 nm). Compared with pure CdS NWs, the CuS/CdS nanocomposites show outstanding visible light H2 evolution, with an optimal rate reaching 2076.5 μmol h−1 g−1. The intrinsic properties of CuS/CdS nanocomposites, such as structure, optical properties, and combined configuration are systematically analyzed by experimental characterizations and theoretical calculations. The comprehensive results show that the Schottky junction between CuS NPs and CdS NWs accelerates photoinduced electron drift from semi-conductive CdS to metallic CuS, improving their activities of water splitting. This work offers a simple route to synthesize one-dimensional CdS-based nanocomposites for efficient visible-light driven energy conversion.

PREPARATION AND CHARACTERIZATION OF VISIBLE-LIGHT-DRIVEN Ce-DOPED CdS NANOWIRES FOR PHOTODEGRADATION OF RHODAMINE B

Visible-light-driven Ce-doped CdS nanowires were synthesized by a solvothermal method. Phase and morphology of Ce-doped CdS nanowires were investigated by XRD and SEM analyses. The analytical results certified that both CdS and Ce-doped CdS samples were uniform pure phase of hexagonal CdS nanowires. The photocatalytic activities of CdS and Ce-doped CdS nanowires were investigated through the photodegradation of rhodamine B (RhB) under visible light irradiation. The 3% Ce-doped CdS nanowires have the highest photocatalytic efficiency of 95.75% within 120 min and are the promising material used for wastewater treatment.

Determination of the Wurtzite and Zincblende Fractions in II–VI Semiconductor Nanowires

We present a detailed powder X-ray diffraction (p-XRD) and transmission electron microscopy (TEM) study to explore the structural properties of CdS, CdSe, and CdTe semiconductor nanowires (NWs) gro...

Synthesis and visible-light photocatalytic properties of BiOBr/CdS nanomaterials

The visible-light-responsive composite photocatalyst is beneficial to improve the solar energy utilization efficiency through the coupling of narrow bandgap materials. In this work, CdS nanowires were prepared by hydrothermal method, and then BiOBr/CdS composite materials with different mass ratios were successfully prepared by a simple two-step sonography-precipitation method using CdS nanowires as a deposition template. The photocatalysts were characterized by XRD, SEM, XPS, TEM, and other methods. Rhodamine B (RhB) was used as a model pollutant to evaluate the photocatalytic activity of BiOBr/CdS catalysts with different mass ratios. The photocatalytic test results show that the composite photocatalyst containing 60% BiOBr has the highest photocatalytic activity, which indicates that it is related to the decrease in photogenerated charge recombination rate. Subsequently, the electrochemical and physical methods were used to illustrate the electron transfer mechanism and the main active center of the as-prepared samples. Free radical capture experiments reveal that holes are the main active species in the photocatalytic process of composite samples. BiOBr/CdS composite photocatalyst was prepared by a simple precipitation method using dispersed one-dimensional CdS nanowires as a template. BiOBr/CdS heterostructure combined adsorption and catalysis to degrade RhB molecules more efficiently. Free radical trapping experiments reveal that holes are the main active species in the photocatalytic process of composite samples.

Co(OH)2 water oxidation cocatalyst-decorated CdS nanowires for enhanced photocatalytic CO2 reduction performance.

Photocatalytic CO2 reduction is a promising technology to resolve the greenhouse effect and energy crisis. In this work, a Co(OH)2 nanoparticle decorated CdS nanowire (Co(OH)2/CdS) based heterostructured photocatalyst was prepared via a solvothermal and subsequent co-precipitation method, and it was used for photocatalytic CO2 reduction. The optimal Co(OH)2/CdS photocatalyst achieves a CO production rate of 8.11 μmol g-1 h-1 under visible light irradiation (λ > 420 nm), which is about 2 times higher than that of bare CdS. The experimental results show that a Co(OH)2 cocatalyst possesses a great capability of consuming holes, which promotes the oxygen-producing half-reaction and accelerates charge separation, thus enhancing the CO2 photoreduction performance of CdS. Notably, without using complex synthesis processes, hazardous substances or expensive ingredients, Co(OH)2/CdS shows high light absorption, efficient charge separation and complete CO product selectivity. This work offers a new pathway for the construction of cost-effective photocatalytic materials to achieve highly efficient CO2 reduction activity by the integration of a Co(OH)2 cocatalyst.

Experimental evidence of continuous isotropic-nematic phase transition in CdS nanowire nanocomposites of a nematic liquid crystal

ABSTRACT The calamitic nematic liquid crystal generally exhibits a discontinuous weakly first-order isotropic-nematic (I-N) phase transition. We found that, on the incorporation of CdS nanowire in the nematic host, the weakly first-order discontinuous I-N phase transition evolved as a continuous phase transition. The parallel and perpendicular components of dielectric permittivity and bulk conductivity of nanocomposites of CdS nanowires of a nematic liquid crystal (NLC) are found to follow continuous I-N phase transition in contrast to the discontinuous weakly first-order transition of the pure host nematic liquid crystal. This was further confirmed from scattered iGntensity measurements on the CdS nanocomposite samples of nematic liquid crystal in homeotropically aligned cells. Such measurements indicate a continuous phase transition for the nanocomposites of NLC having concentrations less than 0.2 wt% of CdS nanowires in NLC. The dielectric anisotropy, birefringence, threshold voltage of nanocomposites of CdS nanowire in a calamitic nematic liquid crystal with varying concentration of the nanowire have been measured. The ionic conductivity of nanocomposites of CdS nanowires of NLC increases with increasing concentration of CdS nanowires.

Highly efficient H2 generation over Cu2Se decorated CdS0.95Se0.05 nanowires by photocatalytic water reduction

The development of efficient co-catalysts for promoting solar-driven water splitting to hydrogen (H2) energy conversion is of increasing importance but still a challenging scheme. In the present work, a noble-metal-free copper selenide (Cu2Se) is primarily evaluated the possibility of functioning as a co-catalyst for enhancing photocatalytic H2 evolution activity by virtue of density functional theory (DFT) calculations. Then, the photocatalysts CdS0.95Se0.05 nanowires (NWs) decorated with Cu2Se nanoparticles (NPs) as co-catalyst are designed and successfully fabricated via a hydrothermal method. Under visible light (λ ≥ 400 nm) illumination, the as-prepared Cu2Se/CdS0.95Se0.05 nanocomposites loading with 20 mol% of Cu2Se NPs exhibits the highest photocatalytic activity with an H2 generation rate of 570.7 μmol·h−1 and a corresponding apparent quantum efficiency (AQE) of 31.26%, which is about 7.1 and 27.4 times greater than that of pristine CdS0.95Se0.05 and CdS NWs, respectively. Theoretical calculations and experimental measurements demonstrate that the excellent activity of the hybrid catalysts is ascribed to the formation of Ohmic-type heterojunctions between CdS0.95Se0.05 semiconductor and semi-metallic Cu2Se, which can not only facilitate the charge carriers separation and transportation but also improve the surface H2-evolution kinetics.

Local strain gauge based on the nanowires ring resonator embedded in a flexible substrate

The authors proposed a flexible microresonator based on nanowires composed of Ⅱ–Ⅵ compounds to detect the small strain caused by external motion. The nanowire ring resonator is embedded in polydimethylsiloxane (PDMS) flexibility to improve the coupling efficiency. In this work, CdS nanowire is fabricated onto a PDMS flexible substrate. With the help of a fibre tip, the single nanowire is manipulated under a microscope, allowing the curved line to be a ring and making the litter overlapping. This overlap increases coupling efficiency and sensor performance. The ring cavity has the parameters of diameter 1 µm, length 75 µm and radius ∼10 µm. Experiments demonstrated the process of fabricating a strain sensor and detected peak shifts. This resonant wavelength appeared red-shift and linear tuned when stretching the flexible substrate. The quality factor was about 2000 and the gauge factor was about 80 nm per stretching unit. Being a small structure and high sensitivity, the sensor can be integrated into the chip. This promotes the development of miniaturisation to some extent. As a result, this work is beneficial to optical manipulation, further being extended to the tunable light source.

Core-shell cadmium sulphide @ silver sulphide nanowires surface architecture: Design towards photoelectrochemical solar cells

Design and development of cadmium sulphide core with silver sulphide shell assembly in nanowire (NWs) surface architecture has been explored through room temperature, simple chemical route towards photoelectrochemical solar cell application. Incorporation of low band gap Ag2S nanoparticles over the outer surface of the chemical bath deposited CdS NWs has been achieved by simple cation exchange route based on negative free energy of formation. Shell optimization has been performed by investigating structure, surface morphologies and optical analyses and correlated with the photovoltaic parameters. Interestingly, core–shell CdS NWs/ Ag2S exhibits 1.5 better performance in terms of linear voltammetry, photocurrent transient response and the photo stability than bare CdS. Furthermore, three-fold enhancement in photoelectrochemical conversion efficiency have been observed for optimized FTO/ CdS NWs/Ag2S compared to bare FTO/CdS NWs due to the augmented light harvesting and condensed charge recombination. External quantum efficiency exhibits 24% for the optimized CdS NWs/ Ag2S core shell structure. Mott-Schottky and electrochemical impedance spectroscopy measurements have been used for better understanding the impact of gradual growth of Ag2S over CdS NWs which directly influences the overall photocurrent density of the devices.

Effect of sulfur precursor concentration on the structures and optical properties of CdS nanowire array on Cd foil by solvothermal method

CdS nanowire array on foil has been fabricated through a solvothermal method, which is uniform, regular and approximately perpendicular to the Cd foil. With the variation of sulfur precursor concentration, the relative intensity of (100), (002) and (101) peak are variable. The nanostructured CdS show the preferential (002)-orientation growth. At the sulfur concentration of 0.1 mol/l, 0.2 mol/l and 0.3 mol/l, CdS nanowires are approximately perpendicular to the Cd foil. At the high sulfur concentration, the characterization of array is destroyed. The band gap, which are estimated from the absorptance spectra using the Kubelka-Munk method, increase with the increasing sulfur precursor concentration until the concentration reaches up to 0.4 mol/l and no longer increases. It is very important to understand the relation between the experimental parameters and the physical properties of the CdS nanowires.

Optically Programmable Plateau-Rayleigh Instability for High-Resolution and Scalable Morphology Manipulation of Silver Nanowires for Flexible Optoelectronics.

The ability to engineer microscale and nanoscale morphology upon metal nanowires (NWs) has been essential to achieve new electronic and photonic functions. Here, this study reports an optically programmable Plateau-Rayleigh instability (PRI) to demonstrate a facile, scalable, and high-resolution morphology engineering of silver NWs (AgNWs) at temperatures <150 °C within 10 min. This has been accomplished by conjugating a photosensitive diphenyliodonium nitrate with AgNWs to modulate surface-atom diffusion. The conjugation is UV-decomposable and able to form a cladding of molten salt-like compounds, so that the PRI of the AgNWs can be optically programmed and triggered at a much lower temperature than the melting point of AgNWs. This PRI self-assembly technique can yield both various novel nanostructures from single NW and large-area microelectrodes from the NW network on various substrates, such as a nanoscale dot-dash chain and the microelectrode down to 5 μm in line width that is the highest resolution ever fabricated for the AgNW-based electrode. Finally, the patterned AgNWs as flexible transparent electrodes were demonstrated for a wearable CdS NW photodetector. This study provides a new paradigm for engineering metal micro-/nanostructures, which holds great potential in fabrication of various sophisticated devices.

A Ternary Dumbbell Structure with Spatially Separated Catalytic Sites for Photocatalytic Overall Water Splitting.

Solar‐driven overall water splitting based on metal sulfide semiconductor photocatalysts remains as a challenge owing to the strong charge recombination and deficient catalytic active sites. Additionally, significant inhibition of back reactions, especially the oxidation of sulfide ions during the photocatalytic water oxidation catalysis, is an arduous task that requires an efficient photogenerated hole transfer dynamics. Here, a ternary dumbbell‐shaped catalyst based on RuO2/CdS/MoS2 with spatially separated catalytic sites is developed to achieve simultaneous production of hydrogen and oxygen under simulated solar‐light without any sacrificial agents. Particularly, MoS2 nanosheets anchored on the two ends of CdS nanowires are identified as a reduction cocatalyst to accelerate hydrogen evolution, while RuO2 nanoparticles as an oxidation cocatalyst are deposited onto the sidewalls of CdS nanowires to facilitate oxygen evolution kinetics. The density functional theory simulations and ultrafast spectroscopic results reveal that photogenerated electrons and holes directionally migrate to MoS2 and RuO2 catalytic sites, respectively, thus achieving efficient charge carrier separation. The design of ternary dumbbell structure guarantees metal sulfides against photocorrosion and thus extends their range in solar water splitting.