CdS Nanowires Research Articles

All-optical broadband terahertz modulator based on CdS NWs/Si heterojunction and interface photoconductivity analysis

A high-performance, low-cost terahertz modulator is fabricated by spin-coating CdS nanowires onto silicon. This all-optical modulator achieves broadband modulation (0.4–1.6 THz) with a significant depth of 85% at a low power density (2 W cm−2), exceeding bare silicon by fourfold. THz-TDS confirms its terahertz amplitude modulation capability. Tests of the simple photonic switch further illustrate the modulator’s potential for carrying information on a terahertz transmission wave. The modulation mechanism is explained through energy band theory and photoconductivity data. This work also presents a novel method for probing heterostructure formation using THz-TDS with laser irradiation.

High-Performance 1D CdS/2D Te Heterojunction Photodetector

Abstract Van der Waals heterostructures facilitate the versatile combination of two-dimensional (2D) materials with semiconductors that possess distinctive band structures, offering a promising platform for developing photodetectors with extensive spectral range and high sensitivity. This study showcases the flawless integration of one-dimensional (1D) CdS nanowires with 2D Te nanosheets, resulting in the creation of a high-performance, mixed-dimensional heterojunction photodetector. Bandgap engineering at the CdS/Te interface promotes Type II band alignment, markedly improving the separation and transport of photo-generated charge carriers. Additionally, the interaction between materials of different dimensions significantly enhances the device’s photoresponsivity and detectivity. When operated at low bias, the photodetector displays an impressive rectification ratio of up to 8.57×103, along with superior photoelectric performance spanning the ultraviolet to visible light spectrum. Particularly under 450 nm wavelength laser illumination, the device displayed a high photoresponsivity of up to 126 A W−1, a high detectivity of 1.03×1010 Jones, an external quantum efficiency of up to 3.49×102%, and a rapid response time of 35 ms. The photoresponsivity of this device was at least an order of magnitude higher than other reported mixed-dimensional heterojunction photodetectors. The development of the 1D CdS/2D Te heterostructure opens new pathways for high-sensitivity, broad-spectrum photodetection technologies.

Enhancing and broadening the photoresponse of CdS nanowire by constructing core–shell heterostructure

Limited by the severe surface recombination and large bandgap, it is still a challenge to achieve a high-performance broad-spectrum photodetector based on CdS nanowires (NWs). In this work, the CdS/GeS core–shell heterostructure is constructed to enhance and broaden the photoresponse of CdS NWs. The CdS/GeS core–shell heterostructure NWs are prepared by the chemical vapor deposition method, exhibiting smooth surfaces, controlled shell thicknesses, and compositions. From the UV-Vis-near-infrared (NIR) diffuse reflectance spectrum, PL, and time-resolved photoluminescence studies, it is found that the surface recombination is weakened and the light absorption range is widened after the constructing core–shell heterostructure. When configured into photodetectors, the responsivity of the CdS/GeS core–shell heterostructure NWs is up to 76.8 A W−1, which is 10 folds higher than that of pristine CdS NWs. Furthermore, the photoresponse wavelength of the CdS/GeS core–shell heterostructure NWs is extended from 405 to 850 nm. The improved photodetection performance is attributed to the effective separation of photogenerated carriers at the heterostructure interface, weakened surface recombination, and excellent light absorption of the GeS shell. All results imply that constructing core–shell heterostructures is an effective strategy for constructing high-performance photodetectors.

Defect Engineering and Piezoelectrical Polarization Synergistically Assisted for Photoelectrochemical Sensing Based on CdS Nanowires

AbstractDeveloping progressive photoelectrochemical (PEC) techniques holds great potential for advancing analytical sensitivity in clinical. However, the low transport and separation of charge carrier efficiency and deficient active sites block efficient and durable PEC analytical performance features. And herein a piezo‐assisted PEC sensing platform for glutathione (GSH) detection are successfully prepared based on S vacancies rich CdS (Sv‐CdS) nanowires. The collaboration of piezoelectric polarization and S vacancies engineering contributed to the boosted PEC performance by accelerating the spatial separation of photogenerated charges and providing abundant active sites. Moreover, the charge transfer efficiency further promoted with the introduction of GSH acted a hole scavenge that effectively suppresses the electron‐hole recombination, giving rise to an amplified photocurrent. As a demonstration, the proposed method presents an outstanding analytical performance toward GSH. Consequently, this work provides an inspirable and convenient route for designing high‐efficiency photoelectrode in PEC sensing in virtue of judicious structural, and defect engineering, and the exploring of an external‐field‐coupling‐enhanced PEC platform.

Influence of functionalized diketopyrrolopyrrole sensitizer on the performance of CdS nanowire based-DSSC applications

Synthesis of chromophore (E)-2-(2-(2-(5-(2,5-bis(2-ethylhexyl)-3,6-dioxo-4-(thiophen-2-yl)-2,3,5,6 tetrahydropyrrolo [3,4-c] pyrrol-1-yl) thiophen-2-yl) vinyl)-4H-chromen-4 ylidene) malononitrile (DPP-CM-CN) has been designed and achieved in multistep reaction strategy. The experimental, photophysical and electrochemical properties along with theoretical calculations were explored. DPP-CM-CN dye was – chemically anchored on CdS nanowires (NWs) to investigate its influence on the dye-sensitized solar cell (DSSC) applications. Under the illumination of standard sunlight conditions, the photovoltaic performance of DPP-CM-CN based CdS nanowire device displayed a power conversion efficiency (PCE) of 0.38 %, which is 3.30 times higher as compared to a bare CdS nanowire (0.115 %) based DSSC device; ascribed to the dye loading time on CdS nanostructures. The present results suggest the potential ability of DPP-CM-CN to enhance DSSC device efficiency and reveal the importance of dye molecules in device fabrication, a key step towards the development of DSSC technology.

Novel Phenothiazine and Coumarin based Sensitizers: Design, Synthesis and Photoelectrochemical Application by Anchoring on CdS Nanowires

Novel metal-free organic dyes (E)-2-cyano-3-(10-(prop-2-yn-1-yl)-10H-phenothiazin-3-yl)acrylic acid (PPC) and (E)-2-cyano-3-(10-((1-((7-methyl-2-oxo-2H-chromen-4-yl)methyl)-1H-1,2,3-triazol-4-yl)methyl)-4a,10a-dihydro-10H-phenothiazin-3-yl)acrylic acid (PCTC) was synthesized and then anchored to 1D cadmium sulfide nanowires (1D CdS NWs) for application in photoelectrochemical dye-sensitized solar cell (DSSC). The 1D CdS nanowires were interconnected into a nanonetwork using solution chemistry in a straightforward and efficient manner. The UV-visible spectroscopy, cyclic voltammetry and density functional theory (DFT) were effectively employed to analyze the characteristics of PPC and PCTC. The sensitizer-anchored CdS nanowires have a broader range of light absorption in the UV-visible spectrum compared to bare CdS nanowires. The complete device has the assembly FTO, compact CdS, CdS nanowires, synthesized dye and counter electrode. In photovoltaic assessment, the PCTC and PPC devices yield 3.19 and 3.04 times, respectively, more efficiency than naked CdS nanowires under conventional sunshine illumination (100 mW/cm2, AM 1.5G). The obtained results provide strong evidence supporting the presence of rising external quantum efficiency (EQE) and show a high level of consistency with the optical tests.

Morphology and luminescent properties of gold catalysed CdS 1D structures: The influence of temperature and atmosphere

In this work, CdS nanowires (NWs) were prepared by the catalytic method using Au nanoparticles onto GaAs and CdS substrates. Scanning and transmission electron microscopy techniques (SEM, TEM) allowed observing different morphologies in the obtained products: variable diameter, pointed and ultra-long several microns length NWs. Also, a nanotube like hollow structure was identified when CdS/ITO/glass substrates were used, and its possible mechanism of formation is presented. The origins of the obtained morphologies was explained as depending on the type of vapor specie, the growth temperature and the used substrate. The photoluminescence (PL) of the NWs can be observed with the naked eye even at RT. PL spectra as a function of temperature were analysed and related with the morphology features.

A binary dumbbell visible light driven photocatalyst for simultaneous hydrogen production with the selective oxidation of benzyl alcohol to benzaldehyde

Photocatalytic H2 production with selective oxidation of organic moieties in an aqueous medium is a fascinating research area. However, the rational design of photocatalysts and their photocatalytic performance are still inadequate. In this work, we efficiently synthesized the MoS2 tipped CdS nanowires (NWs) photocatalyst using soft templates via the two-step hydrothermal method for efficient H2 production with selective oxidation of benzyl alcohol (BO) under visible light illumination. The optimized MoS2 tipped CdS NWs (20 % MoS2) photocatalyst exhibits the highest photocatalytic H2 production efficiency of 13.55 mmol g−1 h−1 with 99 % selective oxidation of BO, which was 42.34 and 2.21 times greater photocatalytic performance than that of pristine CdS NWs and MoS2/CdS NWs, respectively. The directional loading of MoS2 at the tips of CdS NWs (as compared to nondirectional MoS2 at CdS NWs) is the key factor towards superior H2 production with 99 % selective oxidation of BO and has an inhibitory effect on the photo corrosion of pristine CdS NWs. Therefore, the amazing enhancement in the photocatalytic performance and selectivity of optimized MoS2 tipped CdS NWs (20 % MoS2) photocatalyst is due to the spatial separation of their photoexcited charge carriers through the Schottky junction. Moreover, the unique structure of the MoS2 flower at the tip of 1D CdS NWs offers separate active sites for adsorption and surface reactions such as H2 production at the MoS2 flower (confirmed by Pt photo deposition) and subsequently the selective oxidation of BO at the stem of CdS NWs. This rational design of a photocatalyst could be an inspiring work for the further development of an efficient photocatalytic system for H2 production with selective oxidation of BO (a strategy of mashing two potatoes with one fork).

Size-dependent optical and dielectric anisotropy of CdS nanowire doped high-birefringent nematic liquid crystalline compound

Highly birefringent liquid crystals have grabbed ample attention because of their potential applications as an active medium for devices in visible, infrared and other spectral regions. Here, we have attempted to study the effect of the size and concentration of CdS nanowires on a nematic liquid crystal. Anisotropy in liquid crystals is one of those distinguishing traits that gain their superiority over other materials. We hereby have analyzed how optical and dielectric anisotropy respond to variations in the size and concentration of the dopant. The study is of significant scientific value because there is very little literature available on how dopant size can alter liquid crystalline properties and also introduces a method to tune the properties of pure liquid crystals (LCs) by varying the size and concentration of the dopant. The study explains how the size of the nanowires changes the analyzed parameters and up to what extent. The obtained results yield a significant increase in both optical and dielectric anisotropy by doping CdS nanowires making them an excellent choice for dopant selection. CdS-doped nematic LC mixtures have proved to be highly birefringent and possess a high positive dielectric anisotropy as well. Such a compound can be of great application in device fabrications such as laser beam steerers, electronic lenses, attenuators and light shutters, etc.

Single-mode nanolasers based on FP-WGM hybrid cavity coupling

As an idealized light source, semiconductor nanowire (NW) lasers have been extensively studied due to its potential applications in many fields such as optoelectronics, nanophononics, optical communication, signal processing, and displays. In this letter, we proposed a novel approach to realize a single-mode nanolaser by forming an Fabry–Perot whispering gallery mode (FP-WGM) hybrid nanocavity between two cross-contact CdS NWs, i.e. x and y-NW. In our method, x-NW supports the regular FP oscillation in the axis direction while the cross section of y-NW provides a ultrasmall WGM nanocavity with a higher Q-factor and mode election which confirms the specific single mode can be excited. Experimentally, single-mode lasing emission centered at 517 nm was obtained with full width at half maximum of 0.08 nm and lasing threshold of ∼50 kW cm−2. The suggested designing skills projected a general strategy for lasing mode regulation and single-mode realization. The single-mode low-threshold lasing strategy in coupled NWs may open a new avenue for practical applications of NW lasers and further trigger other photonic devices at a visible range.

Optimization of the Diameter of CdS Nanowires Embedded in a CZTS Buffer Layer under Different Solar Incidence Angles

Optimization of the Diameter of CdS Nanowires Embedded in a CZTS Buffer Layer under Different Solar Incidence Angles

Ultralong Nanowires of Cadmium Phosphate Hydroxide Synthesized Using a Cadmium Oleate Precursor Hydrothermal Method and Sulfidation Conversion to Ultralong CdS Nanowires.

Ultralong nanowires with ultrahigh aspect ratios exhibit high flexibility, and they are promising for applications in various fields. Herein, a cadmium oleate precursor hydrothermal method is developed for the synthesis of ultralong nanowires of cadmium phosphate hydroxide. In this method, water-soluble cadmium salt is used as the cadmium source, water-soluble phosphate is used as the phosphorus source, and sodium oleate is adopted as a reactant to form cadmium oleate precursor and as a structure-directing agent. By using this method, ultralong nanowires of cadmium phosphate hydroxide are successfully synthesized using CdCl2, sodium oleate, and NaH2PO4 as reactants in an aqueous solution by hydrothermal treatment at 180 °C for 24 h. In addition, a new type of flexible fire-resistant inorganic paper with good electrical insulation performance is fabricated using ultralong nanowires of cadmium phosphate hydroxide. As an example of the extended application of this synthetic method, ultralong nanowires of cadmium phosphate hydroxide can be converted to ultralong CdS nanowires through a convenient sulfidation reaction. In this way, ultralong CdS nanowires are successfully synthesized by simple sulfidation of ultralong nanowires of cadmium phosphate hydroxide under mild conditions. The as-prepared ultralong nanowires of cadmium phosphate hydroxide are promising for applications as the precursors and templates for synthesizing other inorganic ultralong nanowires and have wide applications in various fields.

Harvesting the Vibration Energy of CdS for High‐Efficient Piezo‐Photocatalysis Removal of U(VI): Roles of Shape Dependent and Piezoelectric Polarization

Piezo‐photocatalysis could coalesce the advantages of mechanical vibration and solar energy perfectly to achieve high‐efficiency catalytic activity. Herein, the quintessential piezoelectric material CdS nanowires with different aspect ratios are precisely constructed and applied for piezo‐photocatalytic reduction of U(VI) for the first time. The ultrasonic (60 kHz, 100 W) induces piezoelectric potential to generate a 0.57 eV A−1 electric field, which is added to the direction of CdS (010) as a driving force to efficiently separate photogenerated charges. The alliance between piezoelectric effect and photocatalytic activity endows CdS NW‐3 with the fastest piezo‐photocatalytic rate under ultrasonic vibration and 5 W LED irradiation, and the relevant rate constant (0.042 min−1) is about 12 and 53.8 times than that of LED and ultrasonication. More importantly, 93.74% of U(VI) could be removed from natural uranium mine wastewater. Therefore, this piezo‐photocatalysis system that reduces U(VI) to easily separable (UO2)O2·2H2O(s) provides valuable input for disposal applications of radioactive wastewater and broadens the horizons of nuclear energy utilization toward the advancement of carbon neutrality.

Eosin‐G and ethyl eosin dye sensitized CdS nanowires towards dye sensitized solar cells applications

AbstractOne dimensional (1‐D) CdS nanowires have been grown through a low temperature chemical route and have been sensitized with eosin‐G and ethyl eosin dyes to broaden the absorption spectrum of CdS and to enhance the photoelectrochemical (PEC) performance under illumination. The used method is advantageous due to its simplicity, low cost, scalability, and controllability. Interestingly, eosin‐G and ethyl eosin dyes yield nearly four‐ and six‐fold increase in device efficiency compared to bare CdS when tested in dye‐sensitized solar cell assembly. Structural, surface morphological, optical, and surface wettability studies have been formulated for CdS, whereas identification of materials along with PEC investigations were conducted through current density–voltage (J‐V), external quantum efficiency (EQE), characteristics under the illumination of 94.6 mW/cm2 (AM 1.5G), and electrochemical impedance spectroscopy (EIS).

Customizing dumbbell-shaped heterostructured artificial photosystems steering versatile photoredox catalysis.

Benefiting from their excellent light-capturing ability, suitable energy band structure and abundant active sites, transition metal chalcogenides (TMCs) have been attracting widespread attention in heterogeneous photocatalysis. Nonetheless, TMCs still suffer from sluggish charge transfer kinetics, a rapid charge recombination rate and poor stability, rendering the construction of high-performance artificial photosystems challenging. Here, a ternary dumbbell-shaped CdS/MoS2/CuS heterostructure with spatially separated catalytically active sites has been elaborately designed. In such a heterostructured nanoarchitecture, MoS2 clusters, selectively grown on both ends of the CdS nanowires (NWs), act as terminal electron collectors, while CuS nanolayers, coated on the sidewalls of CdS NWs through ion exchange, form a P-N heterojunction with the CdS NW framework, which accelerates the migration of holes from CdS to CuS, effectively suppressing the oxidation of sulfide ions and improving the stability of CdS NWs. The well-defined dumbbell-shaped CdS/MoS2/CuS ternary heterostructure provides a structural basis for spatially precise regulation of the charge migration pathway, where photogenerated electrons and holes directionally migrate to the MoS2 and CuS catalytic sites, respectively, ultimately achieving efficient carrier separation and significantly enhancing photoactivity for both photocatalytic hydrogen generation and selective organic transformation under visible light. Moreover, we have also ascertained that such ion exchange and interface configuration engineering strategies are universal. Our work features a simple yet efficient strategy for smartly designing multi-component heterostructures to precisely modulate spatially vectorial charge separation at the nanoscale for solar-to-hydrogen conversion.

Directing the CdS nanosheet and nanowire to high efficiency for photocatalytic anaerobic dehydrogenation of benzyl alcohol to benzaldehyde by depositing Au25 nanoclusters

The photocatalysis of direct dehydrogenation of benzyl alcohol to benzaldehyde is an energy saving way to synthesize fine chemicals and pure hydrogen by using solar energy. The CdS-based catalysts were one of the typical kinds of photocatalysts for this reaction. The morphology of CdS could be easily tuned, which could greatly influence the photocatalytic performances. However, the morphology effect of CdS on the photocatalytic behaviour of the direct dehydrogenation of benzyl alcohol has not been investigated yet. In this work, we synthesized CdS with two different morphologies (nanosheet (NS) and nanowire (NW)) and found the CdS-NS showed much higher photocatalytic activity for converting the benzyl alcohol than the CdS-NW, but the selectivity to benzaldehyde over the two supports was very low. By depositing Au25 nanoclusters on the CdS-NW and CdS-NS, the morphology effect of the CdS support could be mitigated and their catalytic activity and selectivity could be greatly boosted for the photocatalytic anaerobic dehydrogenation of benzyl alcohol to benzaldehyde and H2. The results of this work would provide new insight into the design of efficient photocatalysts for synthesizing fine chemicals.

Novel 1,2,4-triazole sensitizers using N-arylsydnone as Synthon: Synthesis, Spectral, electrochemical, DFT and photovoltaic properties

Two novel 1,2,4-triazolone derivatized triphenylamine (TPA) and phenothiazine (PTZ) based metal-free organic dyes have been designed, synthesized and anchored on 1D CdS nanowires to serve as photoelectrochemical (PEC) dye-sensitized solar cells (DSSCs). Solution chemistry is employed simply and efficiently to link cadmium sulfide nanowires (CdS NWs) into a nano-network. Optical, electrochemical and density functional theory (DFT) have been well utilized to examine the properties of synthesized dyes (TPA and PTZ). In the visible range, sensitizer-anchored CdS NWs exhibit a wider region of light absorption referenced to naked CdS NWs. Comprehensive photovoltaic assessment showed that TPA and PTZ devices respectively showed IPCE 3.02 and 3.13 times more efficient than bare CdS NWs under standard sunlight (100 mW/cm2, AM 1.5G) illumination. The collected findings offer solid evidence for the existence of increasing external quantum efficiency (EQE) and exhibit good agreement with the optical experiments.

Electronic, magnetic and optical properties of Co(II) doped and (Al, Co) co-doped CdS nanowires: An ab initio study

In this work, we have carried out first-principles calculations for understanding the optoelectronic and magnetic properties of Co(II)-doped and (Al, Co) co-doped CdS nanowires. In the free carrier Co(II)-doped CdS NW, the spin-down Co(II)-ta state is completely empty, leading to a super-exchange process. The exchange coupling of the electron carrier (provided by Al co-doping) with the spin-down Co(II)-ta state promote a ferromagnetic ordering via double exchange interactions with a Curie temperature above room temperature. From the optical analysis, we found that Co(II) doping causes a blue-shift of the fundamental energy gap of CdS nanowire. The observed d-d spin-allowed transition peak of the Co(II) ion at 1.97 eV in the visible region is consistent with the experiments. The n-type Al co-doping not only generates an exciton-magnetic polaron (EMP) peak next to the fundamental bandgap but also exhibits the red-shift of the fundamental energy gap and Co(II)'s d-level-to-d-level transition bands. The correlation between spin-spin interaction and optical absorption shows that the d-d spin-allowed transition and optical energy gap both exhibit a blue-shift (red-shift) in the AFM (FM), supporting the experimental observation. Due to the paramagnetic behavior of the Co ions in the far configuration, there is no shift in the d-d transition peak or optical bandgap in the AFM and FM.

A novel ternary nano-photocatalyst (Ni/Ni3C/CdS) for HER and water purification with enhanced photocatalytic activity

CdS-based nanomaterials received much attention since it was synthesized and used as photocatalysts in HER reaction and degradations of organic pollutants. However, it is still an urgent issue to improve the stability and catalytic performance of these kinds of materials before they meet the requirements of the practical applications. Therefore, A novel nano-photocatalyst named as NC-15 was prepared in this paper by loading Ni3C nanosheets (NSs) and Ni nanoparticles (NPs) to the surface of CdS nanowires (NWs). Using a 300 W Xe-lamp (≥400 nm) as the illumination source, NC-15 could accelerate the H2-evolution reaction (HER) in aqueous solution of lacticacid (10 vol%) with the rates of 15247 μmol·g-1h−1 which is ca. 381-time higher than that of CdS NWs, and OTC (LEF) could be ca. 91 % (89 %) degenerated as its aqueous solution (40 ppm) were irradiated 60 mins. The electrochemical analysis indicates that NC-15 should be an n-type semiconductor with the overpotential of −1.08 V vs. Ag/AgCl, which is much lower than those of CdS NWs (-1.20 V), Ni3C/CdS (-1.18 V) and Ni/CdS (-1.13 V) and indicates a faster-photogenerated electrons transfer rate of NC-15. The theoretical simulations confirm that the Ni NPs should supply the active sites during the photocatalytic procedure and the internal electric field at the interfaces of CdS/Ni3C and Ni3C/Ni could accelerate the photogenerated carriers’ separation and migration. In a word, CdS-based ternary nano-photocatalysts possess great potential in the practical application of HER and photodegradation reactions.

Metal Ni nanoparticles in-situ anchored on CdS nanowires as effective cocatalyst for boosting the photocatalytic H2 production and degradation activity

Rapid recombination of photoinduced charge carriers and photoinstability greatly hinder the large-scale application of CdS photocatalysis. Herein, non-noble metal Ni nanoparticles (NPs) as highly efficient co-catalysts are evenly anchored onto the surface of CdS nanowires (NWs) via a facile freeze calcination method. As a result, the H2 production performance of the optimal Ni/CdS NWs under the filter (λ ≥ 420 nm) is about 80 times that of the bare CdS NWs, reaching 13,267.2 μmol h−1 g−1 and the apparent quantum efficiency (AQE) is 9.3%. Furthermore, Ni/CdS NWs photocatalysts have a surprising performance in the degradation of reactive red (RR2) and tetracycline hydrochloride (TCH), and the optimal photodegradation properties are 0.125 and 0.069 min−1, respectively. According to the experimental characterization and theoretical calculation analysis, the deposition of Ni NPs not only increases the active sites of the reaction but also restrains the recombination of photoinduced charge carriers, so ameliorating the photocatalytic performance of CdS photocatalysts. This work provides a novel standpoint for designing non-noble metal co-catalyst/semiconductor photocatalysts for efficient solar energy conversion.