Two-dimensional materials (2DMS) have emerged as key potential materials for electronic, spintronics, photocatalytic, and energy storage device applications, due to their outstanding intrinsic properties. Additionally, ion irradiation, a technique in which energetic beams of charged particles are exposed on materials, enhances the formation of atomic defects toward changing the materials’ properties significantly even for superior performances over their conventional counterparts. Monolayer MoS2 has shown several potential applications as semiconductor with an intrinsic direct band gap. In this study, we have grown monolayer MoS2 on sapphire substrate via. thermal chemical vapor deposition approach and homogenously irradiated with 100 keV helium ions (1 × 1013–1 × 1016 ions cm−2 fluence) and argon ions (1 × 1013–1 × 1014 ions cm−2 fluence) at room temperature to study the effects of ion beam irradiation specifically on surface morphology, structure, optical, and chemical compositions. Both the micro-Raman and photoluminescence studies confirmed the sequential reduction in sulfur atomic concentration due to preferential sputtering and infusion of associated defects, which provide additional nucleation sites due to sulfur vacancies. Consequently, we observed evolutions of MoS2 nano-island on monolayer MoS2 edges due to well controlled low-energy ion irradiation. The study not only leveraging the better understanding and gain of knowledge on the effects of low-energy ion exposers on monolayer MoS2 but also opening a gateway for generating MoS2 nanostructures having potential applications in 2D electronics, spintronics (once integrated with magnetic impurities), and photocatalytic applications.

Supercapatteries in electronics and automobiles often suffer from low energy density and specific capacities. A novel sponge-like CuO/Co3O4/rGO heterostructures was synthesized using a hydrothermal method and used as an anode in high-performance supercapatteries with an alkaline electrolyte. This material's high surface area enhances electrode-electrolyte contact, promoting rapid reaction kinetics and improved conductivity. The Co3O4/CuO/rGO electrodes showed increased surface area, rate capability, and reaction kinetics due to ample electroactive sites, multiple ion transport pathways, and superior charge collection, aided by graphene oxide (GO). Optimized annealing of Co3O4/CuO further improved redox capability and stability. The Co3O4/CuO/rGO heterostructures achieved an ultra-high specific capacitance of 642 C g-1 at 1 A g-1, excellent rate capability, and 91% capacitance retention after 10,000 cycles at 10 A g-1. In a supercapattery device with Co3O4/CuO/rGO as the anode and activated carbon (AC) as the cathode, it delivered a high specific capacity of 337 C g-1 at 1 A g-1, a power density of 808 W kg- 1, and an energy density of 75 Wh kg-1. The solid-state device maintained excellent rate capability (99%) after 10,000 cycles in PVA-KOH gel electrolytes, with the hierarchical nanostructure providing abundant active sites and shortened ion transport pathways.

The cluster counting method (including all Cs complexes missed out in the usage of single Cs complex per element) has previously been reported to provide a significantly better composition estimate than using a single Cs complex per element, for a D9 steel sample. The current study evaluates this method with a nitrogen-implanted zirconium specimen with high oxygen impurity concentrations. Therefore, this system is prone to experiencing strong matrix effects. Quantified elemental depth profiles of the specimen were obtained using XPS to compare with SIMS results. The study confirms that cluster counting of Cs complexes yields significantly better composition estimates than the single Cs complex approach. While fluorine and chlorine are trace-level impurities, their concentrations dominate the composition estimates in both cluster counted and single Cs-complex approaches because the [Formula: see text] complexes of halogens exhibit orders of magnitude higher sensitivities than those of the other elements. Applying relative sensitivity factors of a few tens for these species renders the concentrations of these impurities insignificant. With this correction, the composition estimates by both Cs complex methods improved towards that provided by XPS. At this stage also, the match of the cluster-counted composition with the XPS estimate remains markedly better than that by the single Cs-complex estimate. Additionally, the sensitivity factor values for all cluster-counted Cs complexes were incorporated and adjusted to ensure that the elemental compositions obtained by SIMS matched exactly with those determined by XPS. These relative sensitivity factors are also provided for academic purposes, aiding future studies on secondary ion and cluster formation. Notably, a comparable match could not be achieved between the single CsX species and the XPS profiles, even when varying the sensitivity factor values for the individual CsX species. Furthermore, the cluster counting method provides a means to estimate the sputter rate at each depth of the depth profile.

The layered structure and atomic thinness of transition metal dichalcogenide (TMD) semiconductors make them attractive for various applications. By precise control of the morphology of these materials on the nanoscale, the material can be engineered for specific functional device applications. The present study represents a systematic growth procedure, wherein a space-confined chemical vapor deposition (CVD) route allowed us to synthesize vertically oriented molybdenum disulfide (MoS2) nanosheets with high phase selectivity. While achieving control over the growth of vertical MoS2 (V-MoS2) within a single growth run has many challenges, we demonstrate vertical growth of MoO2 and its subsequent transformation to either a MoO2/MoS2 core-shell structure or vertical MoS2 nanosheets on a SiO2/Si substrate, by modulating the sulfur concentration during the growth process. As a morphologically rich structure, the edge-enhanced MoS2 flower-like structure offered high selectivity toward triethylamine (TEA) sensing over many other volatile organic chemicals (VOCs) studied. The VOC sensing study showed ultrahigh selectivity and sensitivity (9.35 +/- 1.20) x 10(-4) ppm(-1) toward TEA under ultraviolet light exposure. The vertical MoS2 nanosheets with enhanced hydrophobic property showed excellent ambient stability, suggesting its potential for the development of sensors for room-temperature triethylamine detection at the ppm level.

Three-atom-thick two-dimensional layered transition metal dichalcogenides (TMDs) has shown appreciable capabilities as materials candidate for photocatalytic applications. In particular, atomically-thin tungsten disulfide (WS2) has shown attractive interest towards visible-light photocatalytic activity. In this work, we show that the atomically-thin WS2 films can be used as an effective photocatalyst with Methylene Blue (MB) as a model pollutant, under visible light irradiation. Further, we demonstrate that these WS2 thin film samples can be recovered effortlessly without losing its chemical and structural stability. The bi-layered WS2 films yielded a degradation efficiency of 94

Miniaturization of electronic devices has become the new phase of modern technology. Wearable Thermoelectric Generators (WTEG), being flexible, lightweight, self-sustained, and safe are the only replacement for conventional batteries for mobile applications. Molybdenum Disulfide (MoS2), a graphene akin compound having diverse transport behaviour and low thermal conductivity is one of the most preferable candidates for thermoelectric application. However, limited reports are available on MoS2 for Wearable thermoelectric applications. In this study, we have accomplished successful growth of MoS2 nanostructures on conductive carbon fabric via one step hydrothermal method and the effect of thermal oxidation of MoS2 has been studied at various annealing temperature. The structural and elemental analysis confirms the transformation of MoS2 into MoO3. Annealing creates an MoS2(/)MoO3 interface thus enhancing the carrier mobility resulting in enhancement of power factor (481 nW.m(-1)K(-2)) of the sample annealed at 200 degrees C (M1) by 1.29 times than that of pristine MoS2. The sample possessing high performance has been employed to fabricate a WTEG and its real time output has been measured. The design and operating conditions of the device is studied and optimized to obtain the output open circuit voltage as high as 6.4 mV. This paves a promising route to fabricate self- powered wearable biomedical devices.

The design and development of effective electrocatalysts containing nonprecious materials for oxygen evolution reaction (OER) in seawater splitting remains a significant challenge for large-scale industrial hydrogen production. Nonprecious bimetallic oxide-constructed catalysts are utmost promising candidates to obtain boosting electrochemical water oxidation performance. Herein, a transition bimetallic oxide nanostructure electrocatalyst as NiMoO4 vertically standing nanosheet over the nickel foam substrate (NiMoO4/NF) for electrochemical water oxidation process in alkaline fresh/simulated seawater conditions is presented. NiMoO4 nanostructure on NF substrate is successfully obtained using a straightforward hydrothermal reaction route and thermal annealing processes. The surface morphology with elemental characteristics of the resultant NiMoO4/NF sample exposes highly homogenous vertical standing nanosheets assembled on the NF surface. The electrochemical water oxidation performance of the as-prepared electrodes demonstrates the function of diverse hydrothermal reaction times (3, 6, and 9 h) in fresh and simulated seawater electrolyte conditions. In alkaline seawater electrolyte conditions, optimal hydrothermal reaction time-assisted NiMoO4/NF-6 h electrocatalyst possesses significant OER electrocatalytic actives compared to the other samples. Similarly, NiMoO4/NF-6 h catalyst exhibits a small overpotential of 429 mV to achieve a current density of 50 mA cm-2 with a Tafel slope value of 122 mV dec-1 for OER process. As a result, the resultant superior electrocatalytic performance of the optimal hydrothermal reaction time-aided electrocatalyst (NiMoO4/NF-6 h) is ascribed to highly accessible catalytic active centers and enhanced charge transfer kinetics at the interface for electrochemical reactions. Thus, proposed nanostructure-constructed electrocatalysts could prove to be prospective OER candidates for electrochemical water oxidation.

Multiphase chalcogenides are highly interested candidate in thermoelectric application due to their unique band structure, which enhances electrical conductivity. Even though copper sulfide is a widely reported material for thermoelectrics, there have been no reports addressing its various densification methods to study thermoelectric behavior. This report represents the first promising study aimed at investigating the thermoelectric properties of copper sulfide using different densification methods. Herein, we prepared a multiphase (Cu1.96S + CuS) sample using the hydrothermal method followed by the hot press technique and compared its thermoelectric properties with single-phase (Cu1.81S) sample prepared by the cold press method. XRD confirms the formation of multiphase (Cu1.96S + CuS), and TG/DTA shows the phase transition temperature at which the hot press has been carried out. The multiphase sample exhibits a maximum electrical conductivity of 180 Scm−1 at 653 K, which represents a 55

Understanding the nanoscale elastic-size-effects of atomically thin transition-metal dichalcogenides (TMDs) as a function of thickness underpins the avenue of flexible 2D electronics. In this work, we employed the atomic force acoustic microscopy (AFAM) technique to investigate the thickness-dependent elastic properties of CVD grown 2H-MoS2 films. The monolayer MoS2 exhibited a Young's modulus of 273 +/- 27 GPa. Our systematic analysis from bulk to monolayer suggests that the 2H-MoS2 phase exhibits nanoscale elastic-stiffening behavior with decreasing number of layers (thickness). The Young's modulus increased by a factor of similar to 2.7 for monolayer MoS2 when compared with the bulk. First-principle DFT calculations affirm the nanoscale elastic-stiffening behavior of MoS2 with decreasing number of layers. Our findings suggest that the observed elastic stiffening is due to the interlayer sliding, which may be facilitated by defects in MoS2 layers. The observed elastic stiffening may be of potential importance for understanding TMD based nanomechanical devices.

Donor spins in ZnO NWs have promise for quantum information (QI) applications due to high crystalline quality, narrow excitonic luminescence linewidths, and a direct bandgap of this material. It is important to understand the processes that can lead to inhomogeneous broadening of the excitonic transitions for realization of QI devices. We investigate the effect of Ga dopant concentration on the low temperature photoluminescence (PL) of Ga-doped ZnO nanowires. Spectrometer-resolution-limited donor-bound exciton ((DX)-X-0) PL lines are observed at low concentrations with linewidths of around 0.1 meV. A clear increase in the Ga (DX)-X-0 line is observed as trace amounts of Ga are added. Above a certain concentration threshold, we observe a strong increase in the lateral growth coupled with a significant tail on the low energy side of the (DX)-X-0 emission, which scales linearly with dopant precursor concentration. We have analyzed this behavior using different models, including a model based on a bound exciton wavefunction overlap with neigbhouring donors and a Stark effect model due to random charged impurities. We rule out both of these models based on PL excitation spectroscopy measurements and show that a simple exponential model of the Urbach form gives the best fit and points to disorder in the more heavily doped shells. (c) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

Developing highly efficient transparent thermoelectric oxide thin films is the key for futuristic devices, including ecofriendly portable and sustainable electronic devices. In this paper, we report a large thermoelectric power factor of pulsed laser-deposited ZnO and Ga-doped ZnO thin films. Nearly a 40-fold enhancement in electrical conductivity from 118 S cm(-1) (ZnO) to 5050 S cm(-1) (Zn0.98Ga0.02O) is realized with Ga doping. We show that a thermoelectric power factor as high as similar to 2.8 and 2.1 mW m(-1) K-2 can be achieved for ZnO and Zn0.97Ga0.03O thin films, respectively, at temperatures >= 640 K. Our findings suggest that the observed large thermoelectric power factor is a result of enhanced electrical conductivity due to the presence of substantial native oxygen vacancy defects (V-O) in the Zn1-xGaxO thin films. Our results may facilitate the realization of high-performance transparent solid-state thin film thermoelectric devices.

Atomically thin MoS2 layers have emerged as promising semiconductor photocatalytic materials candidate due to their unique thickness-induced physical properties. In this work, we report on the growth of MoS2 layers on sapphire substrates using a gas-phase chemical vapor deposition (CVD) approach. By tuning the CVD growth parameters, MoS2 monolayers with isolated triangular grains and continuous monolayer samples were obtained. We demonstrate that the MoS2 samples with triangular grains exhibit better photocatalytic degradation efficiency ∼ 95.39

Wearable thermoelectric generators, capable of converting human body heat into electricity are one of the most suitable forms of power source to fabricate self-powered wearable electronic devices. Molybdenum disulfide (MoS2), owing to its large intrinsic bandgap and high carrier mobility is one of the most widely explored materials for thermoelectric application. In this work, 2D MoS2 nanosheets were grown on the conductive carbon fabric (CF) by a binder-free in situ hydrothermal method and the 3D ZnO nanoparticles were decorated on them via a facile dip coating technique, to form a 3D/2D interface. Apart from providing a flexible substrate to the material, the CF aids the MoS2 with higher carrier concentration and mobility. Thus, the pristine MoS2 possesses the highest electrical conductivity (σ) of all the samples at 373 K. The 20-mg ZnO-decorated sample achieved a maximum Seebeck coefficient (S) of 11.7 μV/K at 373 K, which is 1.25 times higher than that of pristine MoS2/CF. This enhancement in S is ascribed to the higher energy filtering effect at the ZnO/MoS2 interface that allows the flow of only high-energy carriers. The 15-mg ZnO-decorated sample with optimum S and σ had the highest power factor (PF) of 311 nW/mK2 at 373 K which is 1.2 times higher than that of the pristine sample. This enhancement in PF is mainly due to the synergistic effect of large σ and an extremely low activation energy of 0.00802 eV. Thus, the optimum concentration of ZnO nanoparticles for an enhanced PF is 15 mg owing to its very low activation energy.

Wearable thermoelectric (TE), enabling direct conversion of human body heat into electricity have become the most promising alternative for conventional batteries on the Internet of Things based wearable electronic de -vices. The prime challenge in fabricating a high-performance wearable thermoelectric material is to combine the non-toxicity with high mechanical flexibility, excellent electrical conductivity and high Seebeck coefficient. This paper proposes a facile approach to fabricate a textile-based wearable thermoelectric generator (WTEG) with outstanding TE properties and exceptional flexibility. Herein, molybdenum disulphide (MoS2) nanosheets were grown on conductive carbon fabric (CF) via in-situ binder-free hydrothermal technique and manganese dioxide (MnO2) nanorods were decorated on it via dip coating, to form a 1D/2D interface. We investigated the in-plane TE properties of MnO2/MoS2/CF and achieved a superior power factor of 548.7 nW/mK2 which is 49.5 % higher than that of the pristine MoS2/CF. Such behaviour can be explained by the selective transmission of high energy carriers at the optimized MnO2/MoS2 interface. Moreover, this study is the first to employ a textile-based contact electrode in fabrication of WTEG that resulted in ultra-low internal resistance of the fabricated device (30-300 omega). The lack of rigid contact electrodes leaves more flexibility, which benefits in enhanced wearability of the device. Owing to minimal internal resistance (29.4 omega), the WTEG comprising of 1 -n/p pair could produce an open circuit voltage, as high as 0.2 mV under the thermal gradient of 15-20 K. Additionally, we demonstrated that increasing the number of modules from 1 pair to 4 pairs systematically improved the device performance. The open circuit voltage and output power generated for WTEG comprising of 4 -n/p pairs is measured to be 1.2 mV and 1 nW, respectively. This work provides a feasible design solution for a low resistance, rigid-free WTEGs with high performance which can significantly support the growth of research in wearable thermoelectrics.

The design and development of bifunctional heterogeneous catalysts via interface engineering are a very promising and necessary strategy for constructing highly efficient water electrolyzers. Nevertheless, it remains a great challenge to devolve active catalyst centers for simultaneous activities of oxygen/hydrogen evolution reactions (OER/HER). Herein, an amorphous FeOOH ultrathin nanosheet is grown over crystalline NiCo2S4/Ni3S2 vertically aligned nanosheets (NS) onto a nickel foam (NF) substrate (denoted as FeOOH/NCS/NS/NF) using facile wet chemical approaches. The developed heterogeneous catalyst exhibits superior bifunctional electrocatalytic activities with the lowest overpotentials of 285 mV (OER) and 226 mV (HER) to realize 50 mA cm(-2) in alkaline conditions. Consequently, coupling of amorphous FeOOH and crystalline NiCo2S4/Ni3S2 promotes the surface adsorption of oxygen intermediate species along with water dissociation on catalytic active centers and mass transport with electron transfer at the interface. In the alkaline electrolyzer system, the obtained heterogeneous electrode delivers a substantial overall water splitting performance with a small cell voltage of 1.55 (1.70) V to reach 10 (50) mA cm(-2), where FeOOH/NCS/NS/NF is used as an anode and cathode. Thus, the proposed heterogeneous catalyst strategy validates the effective pathway to design a competent electrode for water electrolysis applications.

The thermoelectric (TE) performance of Molybdenum disulpide (MoS2) can be improved by the incorporation of nanomaterials. MoS2 has been reported as promising thermoelectric materials due to their large bandgap and low thermal conductivity. In the present work, n-type MoS2 was successfully synthesized by facile hydrothermal route with an excellent thermoelectric performance by introducing rhenium (Re) dopant. The structural and morphological analyses confirmed the incorporation of Re into Mo (Molybdenum) lattice. The thermoelectric results showed that both the electrical conductivity (sigma) and Seebeck coefficient (S) has been increased with the increase in Re content (2.5, 5, 7.5 and 10 at%) and temperature (303 K to 700 K), while the thermal conductivity (kappa) was low. Doping with Re on MoS2 enhances the electrical conductivity through band engineering, improving carrier concentration and shifting the Fermi level to the conduction band. Introducing a heavy atomic element can reduce the total thermal conductivity by facilitating mass fluctuation. The maximum Seebeck coefficient was obtained as-100 mu VK-1 at 500 K for Re 5 at% sample, which is 3.7 times greater than undoped MoS2. In addition, introducing electrons through Re doping induced bipolar conduction. These enhancements have increased the power factor of 8 mu Wm-1K-2 at 650 K.

MoS 2 -based transition metal dichalcogenides (TMDCs) have received extensive attention in thermoelectric devices due to its tunable operating temperature from room temperature to mid-temperature applications. Herein, Se-substituted MoS 2 is synthesized by a hydrothermal method, and the thermoelectric properties are systematically investigated to understand the influence of Se substitution. The X-ray diffraction results confirm the phase purity of the Se-substituted MoS 2 . The Se substitution results in creating flake-like morphology as evidenced by the HRSEM images and the XPS confirming the chemical composition of MoS 2- x Se x . The influence of heavier Se substitution on phonon group velocity was inferred from the variation in cell volume and lattice parameter. The hexagonal crystal structure is sustained at all Se concentrations, where the heavier isovalent Se substitution promotes mass-fluctuation, grain boundary, and point defect phonon scattering. Therefore, a notable reduction in thermal conductivity is observed for Se substitution and highly reduced lattice thermal conductivity of 0.44 Wm −1 K −1 at 563 K.

We report the fabrication of a heterogeneous catalyst through vertically aligned NiCo2S4/Ni3S2 nanosheet with encapsulation of ultrathin NiMn layered double hydroxide over self-standing nickel foam (NM/NCS/NS/NF) via two-step hydrothermal processes. Benefiting from more adequate catalytic active centres and copious interfacial charge transfer channels, NM/NCS/NS/NF electrode demonstrates superior bifunctional activity for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) processes under alkaline fresh/simulated seawater electrolyte conditions. As a result, NM/NCS/NS/NF electrode requires the smallest overpotentials of 282 & 312 mV (OER) and 171 & 204 mV (HER) to attain current densities of 30 & 50 mA cm−2 respectively under alkaline simulated seawater electrolyte conditions. Besides, the presence of amorphous NiMn LDH layers over crystalline NiCo2S4/Ni3S2 catalyst stimulates surface adsorption of oxygen intermediate species, water dissociate ability on catalytic active centres, and mass transport with electron transfer at the interface. Further, the two-electrode configuration assisted electrolyser system delivers an efficient overall water splitting activity with minimum cell voltages of 1.54 V (in 1 M KOH) and 1.56 V (in 1 M KOH+0.5 M NaCl) at a current density of 10 mA cm−2. Besides, a fabricated electrolyser cell provides a more sustained water electrolysis process and robust durability for 20 h which displays NM/NCS/NS/NF electrode is a vibrant and potential candidate for realistic seawater electrolysis. Therefore, our proposed heterogeneous electrocatalyst could open up a new platform for developing efficient large-scale efficient seawater electrolysis.

The thermoelectric (TE) performance of conducting polymers can be improved by the incorporation of carbon nanomaterials. In this work, the impact of carbon black (CB) on polypyrrole (PPy) and polypyrrole/polyaniline (PPy/PANI) binary composite have been investigated. Herein, PPy/PANI binary composite was initially prepared through chemical oxidative polymerization and then solution mixed with CB to form PPy/PANI/CB ternary nanocomposite. The structural and morphological analyses confirmed the formation of composites, and the strong interaction present between polymer matrix and CB. This was further confirmed by theoretical study, which showed strong noncovalent interaction and high complex stability between the materials. The thermoelectric results showed that both the electrical conductivity (σ) and Seebeck coefficient (S) has been increased with the increase in CB content (from 10 wt% to 30 wt%) and temperature (303 K to 373 K), while the thermal conductivity (κ) increase was low. The ternary nanocomposite involving 30 wt% of CB was found to be the most promising material which showed an enhanced power factor (PF) of 0.0251 μW/mK2 and high figure of merit (ZT) of 4.37x10-5 at 370 K. The enhancement in ZT for PPy/PANI/CB ternary composite is 2 times, 316 times, 17.3 times, 3.97 times, 11.7 times, and 6.8 times greater than other samples. The enhancement in power factor and ZT was due to energy filtering effect and strong non-covalent interactions between the homopolymers and CB.