Bare WS2 Research Articles

Effects of UV ozone treatment on the photoresponse of the Pt nanoparticles decorated WS2

Chemical vapor deposition (CVD)-grown and Pt nanoparticles (NPs) decorated multilayer WS2 is treated by ultraviolet (UV) ozone for the modification of the surface roughness to realize the enhanced hot carriers injection via the internal photoemission (IPE). The morphology, structure and photophysical properties as well as the dependence of the photoresponse on the UV ozone treatment are investigated. The UV ozone treatment demonstrates obvious effect on the WS2 surface roughness (Sa), which reaches the maximum around 14 nm after 2 min exposure and subsequently decrease with the extension of treatment duration. UV ozone treatment also leads to obviously diminished photoluminescence (PL) and shortened excitons lifetime for bare WS2 while its influence on the electronic structure is negligible. The diminished PL, shortened PL decaying lifetime and increased Sa are all originated from the formation of WOx due to the consumption of top WS2 layer by the severe oxidation, and such effects will be greatly alleviated when the fresh and undisturbed underlying WS2 layer appears with the treatment duration extended to 4 min. The 2 min UV ozone treated WS2/Pt exhibits optimal wide spectrum photoresponse (400–900 nm) with the near infrared (NIR) responsivity around 18 A/W at 750 nm, about 60 % higher compared to that of untreated one while the 4 min overtreated WS2/Pt demonstrates much deteriorated photoresponse. Such behavior can be ascribed to the enhanced hot electrons injection from Pt to WS2 due to the formation of rough Schottky contact as well as the separation of photo-excited electron-hole pairs by Schottky junction. Our study proves that the Sa is a key factor not only for the exciton dynamics but also for the hot electron injection from Pt to WS2.

Defect Passivation of 2D Semiconductors by Fixating Chemisorbed Oxygen Molecules via h-BN Encapsulations.

Hexagonal boron nitride (h-BN) is a key ingredient for various 2D van der Waals heterostructure devices, but the exact role of h-BN encapsulation in relation to the internal defects of 2D semiconductors remains unclear. Here, it is reported that h-BN encapsulation greatly removes the defect-related gap states by stabilizing the chemisorbed oxygen molecules onto the defects of monolayer WS2 crystals. Electron energy loss spectroscopy (EELS) combined with theoretical analysis clearly confirms that the oxygen molecules are chemisorbed onto the defects of WS2 crystals and are fixated by h-BN encapsulation, with excluding a possibility of oxygen molecules trapped in bubbles or wrinkles formed at the interface between WS2 and h-BN. Optical spectroscopic studies show that h-BN encapsulation prevents the desorption of oxygen molecules over various excitation and ambient conditions, resulting in a greatly lowered and stabilized free electron density in monolayer WS2 crystals. This suppresses the exciton annihilation processes by two orders of magnitude compared to that of bare WS2. Furthermore, the valley polarization becomes robust against the various excitation and ambient conditions in the h-BN encapsulated WS2 crystals.

Pt and black phosphorus co-modified flower-like WS2 composites for fast NO2 gas detection at low temperature.

Incomplete recovery, baseline drift, and a long response time have been impeding the practical applications of transition metal dichalcogenide (TMD)-based gas sensors. Here, we report WS2 sensors with significantly improved gas recovery, rapid response, and negligible baseline drift by the incorporation of black phosphorus (BP) as well as the decoration of Pt to detect NO2 for the first time. Compared to bare WS2, the BP-WS2 sensors show higher sensitivity, better repeatability, and more excellent selectivity towards NO2 at the optimal operating temperature of 50 °C. Furthermore, the optimized 30%BP-WS2/Pt sensors exhibit a continuous enhancement in the recovery level and sensitivity with negligible baseline drift. The 30%BP-WS2/Pt sensor also exhibits a shorter response time of 28 s than 49.5 s for its counterpart WS2 sensor towards 32 ppm NO2. The enhanced sensing properties are primarily due to the combined effects of more adsorption sites provided by BP, the spill-over effect of Pt catalysis, and the WS2/BP heterostructure. Therefore, the Pt-decorated 30%BP-WS2 sensor exhibits prominent gas-sensing properties of high gas sensitivity, a low detection limit of 100 ppb, good selectivity, and fast response. Our strategy provides a new route for designing and optimizing TMD-based gas sensors with excellent gas-sensing performance.

Ultra-thin WS2 decorated Co-based Metal‒organic framework derived materials for synergistic electrocatalysis towards pH-Universal hydrogen evolution reaction

Rational designing of a WS2-based hybrid material is extremely important to resolve low-edge sites and poor conductivity of bare WS2, but it is still challenging to construct applicable structures. In this study, an electrocatalyst with ultra-thin WS2 nanosheets homogeneously decorated on Co–N-co-doped carbon hollow nanocages (WS2-3/Co–N–CN-750) is developed, which has favorable hydrogen evolution reaction (HER) activity and stability. The performance of WS2-3/Co–N–CN-750 is significantly improved due to the collective synergy of the specific micro-morphology, interfacial structure, and electronic property. The hybridization of WS2 and Co9S8 can optimize the electronic structure, reduce hydrogen adsorption energy, slash the decomposition barrier of H2O, and accelerate the electron transfer to WS2. Furthermore, the marginal sites of WS2 are significantly increased by optimizing the aggregation growth of WS2. Besides, the precipitation of appropriate Co particles and the Co-based metal-organic framework (Co-MOF) lay a solid foundation for the favorable conductivity of the hybrid material. However, samples after stability tests reveal that cobalt sulfide is corroded and transformed in a locally strong alkali condition. This study highlights the synergies of multicomponent hybridization and provides insights into the stability of congeneric materials.

Co-decoration of WS2 nanosheets with both Au and In2O3-nanoparticles for attaining the CO sensing in self-heating mode

Two-dimensional materials such as WS2 nanosheets (NSs) have unique merits such as high surface area, good conductivity at low temperatures and good chemo-physical stability. In this study, we co-decorated In2O3 and Au NPs on WS2 NSs for CO gas sensing studies. The fabricated sensors were used in self-heating mode of operation at 25 °C, which can significantly decrease the power consumption. It was found that co-decorated gas sensor not only operates at a lower applied voltage, but also exhibits a higher sensing performance (sensitivity and selectivity), relative to bare WS2 NSs. On one hand, generation of In2O3-WS2 heterojunctions acted as notable sources of the resistance modulation and on the other hand, Au with its catalytic effect, significantly enhanced the dissociation of oxygen molecules and also offers many favorable adsorption sites for CO molecules. Therefore, we believe that co-decoration of WS2 is a reliable strategy to enhanced the sensing features in self-heating mode, which is highly demanded for devices with reduced power consumption.

One-step calcination synthesis of 2D/2D g-C3N4/WS2 van der Waals heterojunction for visible light-induced photocatalytic degradation of pharmaceutical pollutants.

It is well-documented that accumulation of pharmaceutically active compounds (PhACs), such as antibiotics, in aquatic ecosystems is a prominent environmental hazard. Herein, a series of 2D materials-based heterojunctions, conceptualized based on the integration of graphitic carbon nitride (g-C3N4) with tungsten disulfide (WS2), was fabricated through a facile one-step calcination process, and systematically evaluated for eliminating tetracycline (TC) and sulfamethoxazole (SMX) from aqueous matrices. The microstructure, optical properties, and surface chemistry of the as-prepared composites were examined with a range of microscopy and spectroscopy techniques. In comparison with pristine g-C3N4 or bare WS2, the g-C3N4/WS2 material, with optimal WS2 loading, showed significantly improved photocatalytic activity, towards degradation of TC (84%) and SMX (96%), under visible light. Free radical scavenging experiments revealed that superoxide anions and hydroxyl radicals were predominantly responsible for the rapid breakdown of the PhACs. In addition, the dissociation intermediates and residues were identified and the plausible photocatalytic degradation pathways of TC and SMX over the as-constructed 2D/2D heterojunction were discussed. Further, the photocatalysis end products were non-toxic, as inferred via the resazurin cell viability assay, employing Escherichia coli as a model organism. Most importantly, the 2D/2D g-C3N4/WS2 architecture was structurally resilient and exhibited a fairly stable cycling performance for persistent usage in wastewater treatment. The outcomes of this study testify that 2D/2D heterojunction of g-C3N4 fragments and WS2 nanosheets holds great promise for destroying antibiotics or their metabolites, usually present in wastewaters.

Au–WS2 Nanohybrids with Enhanced Optical Nonlinearity for Optical Limiting Applications

Utilizing plasmonic effects of metal nanostructures on tailoring the properties of semiconducting materials has gained substantial research attention in the past 10 years. Here, we report the plasmon resonance-induced enhanced optical nonlinearity of Au–WS2 nanohybrids prepared via the blending of liquid phase exfoliated few-layer WS2 nanosheets with chemically synthesized spherical gold nanoparticles (NPs). Nonlinear optical properties were studied using the open aperture Z-scan technique with nanosecond laser pulses of wavelength 532 nm, which lie in the plasmonic band of Au NPs (480–550 nm) and B-excitonic transition range of WS2 nanosheets (520–535 nm). Au–WS2 nanohybrids exhibited an enhanced nonlinear absorption and optical limiting activity with an effective nonlinear absorption coefficient of 182 cm/GW at an on-axis input intensity of 0.14 GW/cm2, which is 3.87 times higher than that of bare WS2 nanosheets. The improved NLO response of nanohybrids is due to the plasmon resonance-induced local field effects, which significantly enhance B-excitonic transitions in WS2 nanosheets. The simulated field intensity enhancement profile also confirmed the effect of formation, where a strong interaction of plasmonic fields with WS2 nanosheets is clearly visible. The enhancement observed in simulated absorption density profiles indicated improved B-excitonic transitions in WS2 nanosheets due to the resonant plasmonic field. Au–WS2 nanohybrids exhibited a low limiting threshold of 0.55 J/cm2, which is better than that of many eminent nanohybrids reported so far. The strategy followed in this work for attaining superior nonlinear optical responses in Au–WS2 nanohybrids will be useful to develop novel nonlinear optical materials for photonic device applications.

Facile fabrication of efficient tungsten disulfide nanoparticles for enhanced photocatalytic removal of tetracycline (TC) and Pb (II) photoreduction

In this present work, tungsten disulfide (WS2) nanoparticles (NPs) by the simple hydrothermal process are a potential photocatalyst that displays a considerable reactivity in heavy metal reduction and degradation of antibiotics pollutants. The WS2 to form nanoparticles to restrict the rapid recombination rate of photo-induced carriers is considered to be a profitable system to promote the ability of photocatalytic heavy metal reduction. The Pb (II) reduction efficiency of the WS2 NPs photocatalyst approach 89.4%, which is 3 folds the rate of bare WS2. Besides, the superior photocatalytic capability for tetracycline (TC) removal (96.6%) also was 2.7 times higher than those of bare WS2. The excellent photocatalytic performance was due to the efficient holes and electrons separation of WS2 and the formation of NPs structure, which received robust photocatalytic redox reaction potentials. The new one-dimensional structure of WS2 NPs decreases the transfer route of photo-response charge carriers. This study supplied a vision to the route of interfacial separation and transport for exciting holes and electrons, which can relate to the interfacial migration of perfected WS2 NPs photocatalysts. It exhibited impressive photocatalytic capability of heavy metal reduction and antibiotics removal. This investigation will offer an observation of the channel of interfacial engineering and separation for excited electrons to solve the environmental pollution problem.

WSSe Nanocomposites for Enhanced Photocatalytic Hydrogen Evolution and Methylene Blue Removal under Visible-Light Irradiation.

In this study, a novel tungsten disulfide diselenide (WSSe) nanocomposite by a facile hydrothermal process with great capable photocatalytic efficiency for hydrogen evolution from water and organic compound removal was discussed. The WSSe nanocomposites form heterojunctions in order to inhibit the quick recombination rate of photo-induced electrons and holes. This is considered to be a useful method in order to enhance the capability of photocatalytic hydrogen production. The hydrogen production rate of the WSSe nanocomposites approaches 3647.4 μmol/g/h, which is 12 and 11 folds the rates of the bare WS2 and WSe2, respectively. Moreover, the excellent photocatalytic performance for Methylene blue (MB) removal (88%) was 2.5 and 1.8 times higher than those of the bare WS2 and WSe2, respectively. The great photocatalytic efficiency was owing to the capable electrons and holes separation of WSSe and the construction of the heterostructure, which possessed vigorous photocatalytic oxidation and reduction potentials. The novel one-dimensional structure of the WSSe heterojunction shortens the transport pathway of the photo-induced electrons and holes. It possesses the great capable photocatalytic efficiency of the hydrogen production and organic dye removal. This study offers an insight into the route of interfacial migration and separation for induced charge carriers in order to generate clean hydrogen energy and to solve the issue of environmental pollution.

Preparation of Fe2O3/WS2 heterostructures with enhanced photocatalytic performances for dye degradation and Cr (Ⅵ) reduction

In the present study, a two-step hydrothermal method was employed to synthesize Fe2O3/WS2 composites with flower-like structure, which performed significant photocatalytic activities compared with the bare components. The morphologies and structures of the as-prepared photocatalysts were characterized, as well as the surface chemical components and the optical properties. Afterwards, the photocatalytic properties of the catalysts were evaluated through degrading MB dye and reducing Cr (VI) under the simulated solar-driven irradiation. Among these photocatalysts, 2WF behaved an efficiently oxidation degradation of 20 mg/L MB solution within 20 min, more than 5 times of bare Fe2O3 nanoparticles and nearly 3 times of bare WS2 nanosheets. Besides that, it exhibited an excellent photocatalytic reduction activity on reducing 40 mg/L Cr (VI) solution within 80 min, which was far superior to bare Fe2O3 and WS2. The excellent photocatalytic oxidation and reduction abilities enabled Fe2O3/WS2 heterostructures to be applied in the field of organic and inorganic pollutant decontaminations.

Fabrication of WS2/WSe2 Z-Scheme Nano-Heterostructure for Efficient Photocatalytic Hydrogen Production and Removal of Congo Red under Visible Light

In this study, a novel tungsten disulfide/tungsten diselenide (WS2/WSe2) heterojunction photocatalyst by a facile hydrothermal process with great capable photocatalytic efficiency for hydrogen evolution from water and organic compound removal was discussed. The WS2/WSe2 heterojunction photocatalyst to form heterojunctions to inhibit the quick recombination rate of photo-response holes and electrons is reflected to be a useful method to enhance the capability of photocatalysis hydrogen production. The hydrogen production rate of the WS2/WSe2 photocatalyst approach is 3856.7 μmol/g/h, which is 12 and 11 folds the efficiency of bare WS2 and WSe2, respectively. Moreover, the excellent photocatalytic performance for Congo Red (CR) removal (92.4%) was 2.4 and 2.1 times higher than those of bare WS2 and WSe2, respectively. The great photocatalytic efficiency was owing to the capable electrons and holes separation of WS2/WSe2 and the construction of Z-scheme heterostructure, which possessed vigorous photocatalytic oxidation and reduction potentials. The novel one-dimensional structure of WS2/WSe2 heterojunction shortens the transport pathway of photo-induced electrons and holes. This work provided an insight to the pathway of interfacial separation and transferring for induced charge carriers, which can refer to the interfacial engineering of developed nanocomposite photocatalysts. It possessed great capable photocatalytic efficiency of hydrogen production and organic dye removal. This study offers an insight to the route of interfacial migration and separation for induced charge carriers to generating clean hydrogen energy and solve environmental pollution issue.

Outstanding photocatalytic activity of WS2/TiO2 quantum dots for ciprofloxacin removal

This investigation aims to efficiently removing ciprofloxacin (CIP) by Z-scheme heterojunction of WS2/TiO2 quantum dots (QDs) under visible light. Interestingly, the photodegradation rate of CIP over WS2/TiO2 (2:1) photocatalysts is much better (2.73- and 3.87-folds) than bare WS2 and TiO2. Great surface area, the construction of the Z-scheme heterostructure, superior efficiency of visible light absorption, and reinforced charge separation rate played dominant aspects in expanding the photocatalytic action of pollutants removal. In addition, the Z-Scheme heterojunction photocatalyst not only decrease the recombination rate of electron-hole pair, but also supports the charge of interfacial transfer ability and enhance photodegradation efficiency. This study proposes new visions for the design of potential Z-scheme visible-light photocatalysts for the degradation of antibiotics in environmental field.

Atomic adsorption of Sn on mechanically cleaved WS2 surface at room temperature

Room temperature (RT) adsorption of tin (Sn) under ultra-high vacuum (UHV) conditions on mechanically cleaved tungsten disulfide (WS2) surfaces is reported here. In-situ low energy electron diffraction (LEED) and scanning tunneling microscopy (STM) studies indicate commensurate adsorption of Sn on the hexagonal surface of WS2. Bare WS2 displays an atomic periodicity of lattice constant 0.34 nm. Growth of Sn reveals monomer like a single atom or unpaired (U) and dimer like- or paired (P) adsorptions on the top (`T’) sulfur (S) sites of the trigonal prismatic sublattice within the honeycomb lattice of WS2. The lateral distance between two nearest adsorbed monomers is around 0.34 nm which is exactly similar to the atomic periodicity of the underneath WS2 substrate crystal. For the case of dimer like- adsorption, the separation between two adspecies is 0.293 nm. The bond length of the adsorbed Sn with the surface S atoms is around 40 (±10) pm. We do not find any evidence of Sn adsorption on the bridge (`B’) or hollow (`H’) site of the WS2 lattice. Analysis of the LEED spots and the FFT images of the STM micrographs after Sn adsorption discloses a stretched hexagonal surface which is most likely due to the overall consequence of a perfectly commensurate monomer and nearly commensurate dimer like- adsorptions of the Sn atoms on the WS2 surface.

Convenient Synthesis of WS2–MoS2 Heterostructures with Enhanced Photocatalytic Performance

A series of WS2–MoS2 composites with different phase ratios have been successfully constructed. First, WS2 with hexagonal phase structure has been achieved by directly annealing a mixture of commercial W and S powders in an Ar atmosphere. Then the hydrothermal method is utilized to realize the epitaxial growth of MoS2 onto the surface of WS2. The dual-petal nanostructure of WS2–MoS2 composites has been revealed by scanning electron microscopy and transmission electron microscopy. The measurement of the optoelectronic property illustrates that WS2–MoS2 heterostructures can present more active sites and a higher effective separation of carriers than can bare WS2 and MoS2. Specifically speaking, 4WS2–96MoS2 can cause the complete degradation of methylene blue within 150 min, and the difference value of the photocurrent can reach a value of 26 μA, which obviously outperforms that of bare MoS2 and WS2. These aforementioned improved performances are closely related to this rationally designed structure for WS2–...

Facile synthesis of 1T-WS2/graphite nanocomposite for efficient solar-driven oxygen evolution reaction

In this work, crystalline two-dimensional (2D) tungsten disulfide nanodisc-like structures (1T-WS2) and its nanocomposite with graphite sheets synthesized using a facile two-step solvothermal procedure for photoelectrochemical (PEC) oxygen evolution reaction (OER). The XRD patterns revealed the existence of WS2 (1T phase) crystalline structure. Both WS2 nanodiscs and graphite were ultrasonicated to exfoliate the sheets and the suspension was solvothermally treated to design a WS2/graphite (WS2/G) nanocomposite. Fascinating flower-like nanostructures composed of nanodiscs observed during the detailed morphological investigation. The FE-SEM observation demonstrated well-dispersed graphite sheets in WS2 nanodiscs. The photoelectrochemical water splitting performance of bare WS2 and WS2/G hybrid photoanodes investigated under simulated 1 SUN irradiations revealed threefold increase in the photocurrent density of WS2/G hybrid photoanode compared to WS2.

Binder-free WS2/ZrO2 hybrid as a photocatalyst for organic pollutant degradation under UV/simulated sunlight and tests for H2 evolution

Novel photocatalysts based on sunlight-driven active two-dimensional (2D) layered materials have drawn considerable attention because of their structural-to-photoactive properties. In this study, via binder-free electrostatic self-assembly, WS2/ZrO2 hybrids were synthesized using a two-step hydrothermal process. The catalysts were thoroughly examined using different analysis techniques. The results indicated that in the WS2/ZrO2 hybrids, ZrO2 nanoparticles (NPs) were randomly grafted on the planar surfaces of WS2 nanosheets (the ZrO2 NPs were tightly anchored to the nanosheets). The WS2/ZrO2 hybrids could considerably enhance the photocatalytic reactions under ultraviolet (UV) and simulated sunlight irradiation with an increase in the amount of ZrO2 NPs anchored to WS2 nanosheets, which influenced the photodegradation rate of crystal violet (CV) dye and the H2 evolution activity. Notably, the rate of H2 generation via the photolysis of water was 1023.9 μmol g−1 h−1 for the WS2/ZrO2-2 catalyst, indicating both the enhanced photocatalytic degradation activity and the H2 advancement performance of the WS2/ZrO2 hybrid. The photocatalytic H2 advancement rate for the WS2/ZrO2-2 catalyst was 5.28 and 1.49 times higher than those for the bare WS2 catalyst under UV and simulated solar illumination, respectively. Additionally, the WS2/ZrO2-2 hybrid exhibited high recyclability owing to the highly hydrophobic nature of the 2D WS2, which was beneficial for the separation of the hybrid photocatalyst from the CV solution. Finally, the results of a scavenger-trapping experiment indicated that active holes (h+) were mainly responsible for the photocatalytic reaction, rather than ˙O2− and ˙OH−. Plausible photoreaction mechanisms of photocatalytic degradation and H2 production in aqueous solutions of the WS2/ZrO2 hybrid were elucidated.

Enhanced photoresponse of tungsten disulfide-reduced graphene oxide hybrid for photoelectrochemical photodetectors

In this report, WS2-reduced graphene oxide (WS2-rGO) hybrid was successfully synthesized through a hydrothermal reduction process in which WS2 nanosheets (WS2 NSs) were prepared by a lithium-ion intercalation and exfoliation technique. The photodetection properties of as-synthesized samples have been systematically investigated using a photoelectrochemical (PEC) system, which presents a reproducible photoresponse of WS2-rGO under zero bias, indicating that such hybrid is a promising photoanode for self-powered photodetectors. At a bias of 0.8 V, the photocurrent density of WS2-rGO hybrid was 4.32 μA/cm2, which is approximately 800% of that of the bare WS2 photodetector. Meanwhile, the photoresponsivity of as-prepared WS2-rGO hybrid increases linearly with the irradiation intensity, up to 9.3 μA/W at power density of 30 mW/cm2. In addition, the stability test exhibits no conspicuous degradation after 100 cycles. The enhanced performance of the WS2-rGO hybrid benefits from the high carrier mobility of rGO and the efficient separation of photogenerated carriers at the WS2-rGO interface. This research demonstrates that the WS2-rGO hybrid has a good prospect in PEC-type photodetectors.

CdSe Quantum Dots Doped WS2 Nanoflowers for Enhanced Solar Hydrogen Production

In this paper, a facile method for synthesizing WS2 nanoflowers (NFs) and CdSe quantum dots (QDs) using hydrothermal and hot injection methods, are reported, respectively. Additionally, the photocatalytic activity of a CdSe QDs/WS2 NF nanocomposite is analyzed in a typical three‐electrode electrochemical cell. It is found that the CdSe QDs/WS2 NF hybrid exhibits a current density of −1.12 mA at 0 V and a Tafel slope of 82 mV dec−1, which are superior to the values of bare WS2 NFs (current density of −0.25 mA and Tafel slope of 150 mV dec−1). This improvement of photocatalytic performance is attributed to the wide range of light absorption for e−/h+ generation provided by the CdSe QDs, as well as the large surface area and numerous active sites for hydrogen production provided by WS2 NFs. Therefore, the CdSe QDs/WS2 NF hybrid structure is a promising candidate for highly effective and stable photocatalytic performance under solar light illumination for hydrogen production.

Synthesis of few-layer WS2 by jet cavitation as anode material for lithium ion batteries

In this study, we propose a green, facile, low-cost and scalable industrial method to get good quality tungsten disulfide (WS2) with few-layer structure (Mo-WS2) by jet cavitation process (JC). The characterizations of bare WS2 and as-synthesized Mo-WS2 are carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy (Raman), Brunauer-Emmett-Teller (BET) and atomic force microscopy (AFM) to study its surface morphologies, crystal structure, structural defects and distributions of pore size, lateral and thickness. The average thickness of as-synthesized Mo-WS2 is about 2.4 nm (<10 layers). Finally, we compare electrochemical tests in terms of charge/discharge tests, cyclic voltammetry, cycle life, rate capability and AC impedance for bare WS2 and Mo-WS2. The specific capacity of Mo-WS2 delivered a capacity of 581 mAh g−1 and 257 mAh g−1 at 0.1C and 10C, respectively, which are superior to those of bare WS2. AC impedance data further approve that Li+ diffusion coefficient in WS2 could be improved by JC process. All these results confirm that the as-synthesized Mo-WS2 exhibited good electrochemical performance and excellent rate capability performance compared to bare one. These results demonstrate that Mo-WS2 is a promising anode material for lithium-ion batteries.

Excitation dependent light emission and enhanced photocatalytic response of WS2/C-dot hybrid nanoscale systems

A facile, hydrothermal route has been employed to synthesize two dimensional (2D) WS2 nanosystems, followed by decoration with C-dots derived from the orange juice extract as the source of carbon. Imaging through transmission electron microscopy (TEM) reveals the formation of C-dots on the WS2 sheets, with dot size varying between 2 and 5 nm and d-spacing of 0.31 nm. The WS2/C-dot hybrid nanosystems were found to reveal excitation dependent luminescence response with underlying mechanism attributed to the influence of either surface traps or/and prevalent heteroatoms. Moreover, Raman spectra of the nanohybrid exhibited both in-plane optic and out of plane vibronic modes, positioned at ~352.8 cm−1 (E12 g) and 421.7 cm−1 (A1 g); apart from two additional peaks, assigned to the D and G bands of the graphitic material. Finally, photocatalytic degradation of methyl orange (MO) and malachite green (MG) were studied under visible light illuminations. While exhibiting a comparatively stronger photoactivity, the MG dye yielded degradation efficiency as high as, ~83% and 91% in case of use of bare WS2 nanosheet and WS2/C-dots as nanocatalysts; respectively. The bifunctional candidates would find a special place in advanced material research owing to exhibition of enhanced radiative emission as well as photocatalytic features.