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Among various parameters of 3D CNTs as a conductive sulfur host material in LSB cathodes, high surface area, high porosity, and small pore size distribution, among others, are the most critical parameters, enhancing LSB performance.

The overall performance of polymer composites depends on not only the intrinsic properties of the polymer matrix and inorganic filler but also the quality of interfacial adhesion. Although many reported approaches have been focused on the chemical treatment for improving interfacial adhesion, the examination of ultimate mechanical performance and long-term properties of polymer composites has been rarely investigated. Herein, we report carbon fiber (CF)/epoxy composites with improved interfacial adhesion by covalent bonding between CFs and the epoxy matrix. This leads to the improved ultimate mechanical properties and enhanced thermal aging performance. Raman mapping demonstrates the formation of an interphase region derived from the covalent bonding between CFs and the epoxy matrix, which enables the uniform fiber distribution and eliminates phase separation during thermal cycling. The covalent attachment of the CF to the epoxy matrix suppresses its migration during temperature fluctuations, preserving the mechanical performance of resulting composites under the thermal aging process. Furthermore, the finite elemental analysis reveals the effectiveness of the chemical treatment of CFs in improving the interfacial strength and toughness of silane-treated CF/epoxy composites. The insight into the mechanical improvement of CF/epoxy composites suggests the high potential of surface modification of inorganic fillers toward polymer composites with tunable properties for different applications.

The advancement of ion transport applications will require the development of functional materials with a high ionic conductivity that is stable, scalable, and micro-patternable. We report unusually high ionic conductivity of Li+, Na+, and K+ in 2D MoS2 nanofilm exceeding 1 S/cm, which is more than 2 orders of magnitude higher when compared to that of conventional solid ionic materials. The high ion conductivity of different cations can be explained by the mitigated activation energy via percolative ion channels in 2H-MoS2, including the 1D ion channel at the grain boundary, as confirmed by modeling and analysis. We obtain field-effect modulation of ion transport with a high on/off ratio. The ion channel is large-scale patternable by conventional lithography, and the thickness can be tuned down to a single atomic layer. The findings yield insight into the ion transport mechanism of van der Waals solid materials and guide the development of future ionic devices owing to the facile and scalable device fabrication with superionic conductivity.

Piezoelectricity in two-dimensional (2D) transition-metal dichalcogenides (TMDs) has attracted significant attention due to their unique crystal structure and the lack of inversion centers when the bulk TMDs thin down to monolayers. Although the piezoelectric effect in atomic-thickness TMDs has been reported earlier, they are exfoliated 2D TMDs and are therefore not scalable. Here, we demonstrate a superior piezoelectric effect from large-scale sputtered, asymmetric 2D MoS2 using meticulous defect engineering based on the thermal-solvent annealing of the MoS2 layer. This yields an output peak current and voltage of 20 pA and 700 mV (after annealing at 450 °C), respectively, which is the highest piezoelectric strength ever reported in 2D MoS2. Indeed, the piezoelectric strength increases with the defect density (sulfur vacancies), which, in turn, increases with the annealing temperature at least up to 450 °C. Moreover, our piezoelectric MoS2 device array shows an exceptional piezoelectric sensitivity of 262 mV/kPa with a high level of uniformity and excellent performance under ambient conditions. A detailed study of the sulfur vacancy-dependent property and its resultant asymmetric structure-induced piezoelectricity is reported. The proposed approach is scalable and can produce advanced materials for flexible piezoelectric devices to be used in emerging bioinspired robotics and biomedical applications.

Atomically thin two-dimensional transition metal dichalcogenides (2D TMDs) are of interest for neuromorphic computing due to their extraordinary properties such as low power consumption, robustness...

Recently, aqueous Zn-ion rechargeable batteries have drawn increasing research attention as an alternative energy storage system relative to the current Li-ion batteries due to their intrinsic properties of high safety, low cost, and high theoretical volumetric capacity. Nevertheless, unwanted dendrite growth on the Zn anode and unstable cathode materials restrict their practical application. In this study, a unique 2D MoS2 coating on a Zn anode using an electrochemical deposition method has been developed for preventing dendrite growth and intricate side reactions. The coated MoS2 layer is a vertically oriented structure that makes the flow of Zn ions easy with a uniform electric field distribution on the anode, resulting in a uniform stripping and plating of Zn2+. In addition, the MoS2 coating enhances anodic diffusion of Zn ions and reduces the series resistance as confirmed by EIS analysis and therefore improves the overall battery performance. The full cell assembled with the MoS2-Zn anode and MnO2 cathode exhibits an excellent reversible specific capacity of 638 mAh/g at 0.1 A/g and stable cycle performance over 2000 cycles with no dendrite formation at the Zn electrode. The presented MoS2 coating on Zn is a facile, scalable, and promising technology for practical Zn-ion batteries with a long life cycle and high safety.

Rapidly increasing markets for electric vehicles (EVs), energy storage for backup support systems and high-power portable electronics demand batteries with higher energy densities and longer cycle lives. Among the various electrochemical energy storage systems, lithium–sulfur (Li–S) batteries have the potential to become the next generation rechargeable batteries because of their high specific energy at low cost. However, the development of practical Li–S batteries for commercial products has been challenged by several obstacles, including unstable cycle life and low sulfur utilization. Only a few studies have considered the importance of low electrolyte and high sulfur loading to improve the overall energy densities of Li–S cells. This article reviews the recent developments of Li–S batteries that can meet the benchmarks of practical parameters and exceed the practical energy density of lithium-ion batteries (LIBs) including areal sulfur loading of at least 4 mg cm−2, electrolyte to sulfur ratio of less than 10 μL mg−1, and high cycling stability of over 300 cycles. This review presents the advancements in each component in Li–S batteries, including the enhancement of the electrochemical properties of sulfur cathodes, lithium anodes, or electrolytes. Also identified are several important strategies of nanoengineering and how they address the practical limitations of Li–S batteries to compete against LIBs. Additionally, perspectives on fundamentals, technology, and materials are provided for the development of Li–S batteries based on nanomaterials and nanoengineering so that they can enter the market of high energy density rechargeable storage systems.

Lithium–sulfur batteries present unique polysulfide chemistry and exhibit a high theoretical energy density of 2600 W h kg−1. However, soluble lithium polysulfides (LiPSs) tend to shuttle during battery cycling and corrode the Li anode; this leads to an eventual performance fading in the Li–S battery. This shuttle effect can be reduced by accelerating the conversion of dissolved polysulfides to insoluble LiPSs and back to sulfur. Herein, a novel 2D Mo0.5W0.5S2 alloy with a 2H (semiconducting)-1T (metallic) mixed-phase is synthesized on carbon nanotubes (CNTs) by a two-step process of co-sputtering and sulfurization. The cathode comprising 2D Mo0.5W0.5S2–CNTs exhibits the synergistic effect of accelerated electron transfer, a higher LiPS binding effect, and good catalytic performance, as confirmed by our electrochemical analysis. As a result, the Li–S battery cell assembled with the 2D Mo0.5W0.5S2/CNT/S cathode shows a high specific capacity of 1228 mA h g−1 at 0.1C and a much higher cycling stability as compared to the pristine cathodes. Our results confirm that the 2D Mo0.5W0.5S2 alloy catalyst deposited on the CNTs can effectively prevent polysulfide shuttling and offer a viable solution to overcome the technical challenges in the development of practical Li–S batteries.

Recent developments in electric vehicles (EVs) and portable electronics, lithium-sulfur (Li-S) battery has emerged as a promising candidate due to its high theoretical energy density. To achieve the practical high energy density (~500 Wh kg-1) in Li-S battery, high active material (sulfur) loading (> 6 mg cm-2), effective sulfur utilization, and low electrolyte-to-sulfur (E:S) ratio (-1) should be achieved. Primarily, high sulfur loading, low E:S ratio, high sulfur content, and an optimum current rate are needed to achieve high energy and power density. In this work, we experimentally investigate polysulfide conversion mechanism that takes place in Li-S battery under extreme, both electrochemical and operating, conditions. An extreme threshold with respect to maximum and minimum sulfur loading and E:S ratio of below 3 or close to zero are thoroughly investigated. It is observed that the underlying polysulfide conversions altered when cell was operated at extreme conditions (e.g. E:S ratio). Furthermore, this work is expected to provide a critical scientific insight through advanced characterization techniques (e.g. in-situ Raman spectroscopy) to mechanistically understand the reaction kinetics in Li-S battery.

The advancement of ion transport applications will require the development of functional materials with a high ionic conductivity that is stable, scalable, and micro-patternable. We report unusually high ionic conductivity of Li

Piezoelectricity in two-dimensional (2D) transition-metal dichalcogenides (TMDs) has attracted significant attention due to their unique crystal structure and the lack of inversion centers when the bulk TMDs thin down to monolayers. Although the piezoelectric effect in atomic-thickness TMDs has been reported earlier, they are exfoliated 2D TMDs and are therefore not scalable. Here, we demonstrate a superior piezoelectric effect from large-scale sputtered, asymmetric 2D MoS

Piezoelectric materials are widely used as electromechanical couples for a variety of sensors and actuators in nanoscale electronic devices. The majority of piezoelectric devices display lateral patterning of counter electrodes beside active materials such as two-dimensional transition metal dichalcogenides (2D TMDs). As a result, their piezoelectric output response is strongly dependent on the lattice orientation of the 2D TMD crystal structure, limiting their piezoelectric properties. To overcome this issue, we fabricated a vertical sandwich design of a piezoelectric sensor with a conformal contact to enhance the overall piezoelectric performance. In addition, we enhanced the piezoelectric properties of 2D WS

Recently, aqueous Zn-ion rechargeable batteries have drawn increasing research attention as an alternative energy storage system relative to the current Li-ion batteries due to their intrinsic properties of high safety, low cost, and high theoretical volumetric capacity. Nevertheless, unwanted dendrite growth on the Zn anode and unstable cathode materials restrict their practical application. In this study, a unique 2D MoS

Wood-derived carbon is a neoteric self-supporter electrode material for supercapacitors or batteries. To improve the electrochemical characteristics, polyaniline (PANI) was deposited on wood carbon (WC) by an in-situ polymerization method. The sandwich-like symmetrical solid-state supercapacitor was developed by preparing WC/PANI composites and their electrochemical properties were examined. The device showed an excellent capacity retention and displayed the maximum specific capacitance of $$22.5\,\hbox {mF cm}^{-2}$$ at a scan rate of $$10~\hbox {mV s}^{-1}$$ . It was also demonstrated an excellent electrical conductivity and an outstanding retention of $${\sim }82\%$$ . It was suggested that the PANI accommodated into WC without any significant morphological change during the charge–discharge cycling of the hybrid WC-based composites. The microstructure and chemical structure of WC/PANI composites were also characterized by the Fourier-transform infrared, Raman spectroscopy and X-ray diffraction techniques.

Two-dimensional (2D) MoS2 has recently emerged as an efficient hydrogen evolution reaction (HER) catalyst due to its unique atomic layered structure and stability in harsh acidic environment. However, the high electrochemical performance of MoS2 is still limited to edges of its 2D layers. Here, we report the synthesis of highly porous MoS2 films exhibiting a large density of edge sites by using a direct sputter deposition method. Interestingly, the as-deposited MoS2 films resulted into a 3R phase with nano porous structure which is attributed to the lattice relaxation and high energy of sputtered ions. The as-synthesized porous MoS2 nanostructures demonstrate an excellent electrocatalytic performance with a low HER onset potential of ∼0.2 V, long-term cycling stability, and a low Tafel slope in the range of ∼80–90 mV/decade at a high cathodic current density.

Alloying two-dimensional transition metal dichalcogenides (2D TMDs) is a promising avenue for band gap engineering. In addition, developing a scalable synthesis process is essential for the practical application of these alloys with tunable band gaps in optoelectronic devices. Here, we report the synthesis of optically uniform and scalable single-layer Mo1- xW xS2 alloys by a two-step chemical vapor deposition (CVD) method followed by a laser thinning process. The amount of W content ( x) in the Mo1- xW xS2 alloy is systemically controlled by the co-sputtering technique. The post-laser process allows layer-by-layer thinning of the Mo1- xW xS2 alloys down to a single-layer; such a layer exhibits tunable properties with the optical band gap ranging from 1.871 to 1.971 eV with variation in the W content, x = 0 to 1. Moreover, the predominant exciton complexes, trions, are transitioned to neutral excitons with increasing W concentration; this is attributed to the decrease in excessive charge carriers with an increase in the W content of the alloy. Photoluminescence (PL) and Raman mapping analyses suggest that the laser-thinning of the Mo1- xW xS2 alloys is a self-limiting process caused by heat dissipation to the substrate, resulting in spatially uniform single-layer Mo1- xW xS2 alloy films. Our findings present a promising path for the fabrication of large-scale single-layer 2D TMD alloys and the design of versatile optoelectronic devices.

Among the candidates to replace Li-ion batteries, Li–S cells are an attractive option as their energy density is about five times higher (~2,600 Wh kg−1). The success of Li–S cells depends in large part on the utilization of metallic Li as anode material. Metallic lithium, however, is prone to grow parasitic dendrites and is highly reactive to several electrolytes; moreover, Li–S cells with metallic Li are also susceptible to polysulfides dissolution. Here, we show that ~10-nm-thick two-dimensional (2D) MoS2 can act as a protective layer for Li-metal anodes, greatly improving the performances of Li–S batteries. In particular, we observe stable Li electrodeposition and the suppression of dendrite nucleation sites. The deposition and dissolution process of a symmetric MoS2-coated Li-metal cell operates at a current density of 10 mA cm−2 with low voltage hysteresis and a threefold improvement in cycle life compared with using bare Li-metal. In a Li–S full-cell configuration, using the MoS2-coated Li as anode and a 3D carbon nanotube–sulfur cathode, we obtain a specific energy density of ~589 Wh kg−1 and a Coulombic efficiency of ~98% for over 1,200 cycles at 0.5 C. Our approach could lead to the realization of high energy density and safe Li-metal-based batteries. An ~10-nm-thick MoS2 layer stabilizes lithium metal anodes and the composite can be used in full-cell Li–S batteries with enhanced performances.

The high theoretical specific capacity of nickel oxide (NiO) makes it attractive as a high-efficiency electrode material for electrochemical energy storage. However, its application is limited due to its inferior electrochemical performance and complicated electrode fabrication process. Here, we developed an in situ fabrication of a graphene-coated, three-dimensional (3D) NiO–Ni structure by simple chemical vapor deposition (CVD). We synthesized NiO layers on Ni foam through a thermal oxidation process; subsequently, we grew graphene layers directly on the surface of NiO after a hydrogen-assisted reduction process. The uniform graphene coating renders high electrical conductivity, structural flexibility and high elastic modulus at atomic thickness. The graphene-coated 3D NiO–Ni structure delivered a high areal density of ∼23 mg cm−2. It also exhibits a high areal capacity of 1.2 mA h cm−2 at 0.1 mA cm−2 for its Li-ion battery performance. The high capacity is attributed to the high surface area of the 3D structure and the unique properties of the graphene layers on the NiO anode. Since the entire process is carried out in one CVD system, the fabrication of such a graphene-coated 3D NiO–Ni anode is simple and scalable for practical applications.

3D printing of fiber-reinforced composites has been receiving increasing attention as an efficient additive approach enabling lightweight, functional, and high-performance components required for industrial applications. The properties of fiber composites significantly depend on internal microstructures, including fiber orientation, distribution, and degree of alignment. Although multiple strategies have been introduced for controlling the fiber composites microstructures, these strategies are mostly active approaches relying on additional control of mechatronics parts, external forces, or intentionally introduced unstable flows inside narrow nozzles. These methods suffer from higher risk of nozzle clogging and requiring extra parts in 3D printing. Here, we introduce helicoid channels into extrusion system as a passive approach to control the fiber alignment without any additional moving parts in direct-write 3D printing. The helicoid channels automatically guide the composite inks and align fibers before flowing into narrow nozzle space, avoiding clogging and improving printability. The analyses indicate that both helicoid surface to volume ratio and helix angle affect the pre-alignment of fibers, leading to tunable mechanical properties of printed fiber-reinforced composites with increased stiffness and strength up to 77.6% and 47.8%, respectively.

Despite of high theoretical energy density, the practical application of Li–S battery (LSB) is limited by its intrinsic hurdles such as lithium polysulfides (LiPSs) shuttling effect and limited sulfur loading and its utilization in cathode. Here, we develop a defect engineered MoxW1-xS2-y alloy catalyst (D-MoWS) deposited on carbon nanofiber (CNF) via a facile hydrothermal synthesis followed by a thermal-solvent vapor etching method to expedite the LiPSs redox kinetics and resolve the limit of sulfur utilization in LSB. The LSB cells assembled using the D-MoWS–CNF–S cathode show the highest specific capacity of 1586 mAh g−1 and excellent areal capacity up to 13.5 mAh cm−2 at high areal sulfur loading of 10 mg cm−2, resulting in the highest energy density of 1090 Wh kg−1 (w.r.t total weight of anode and cathode). Our mechanistic study and ex-situ SEM analysis prove that D-MoWS catalyst accelerates the LiPSs conversion, prevents the shuttling effect and Li-metal corrosion, therefore, effectively reduces the negative/positive electrode capacity (N/P) ratio to the lowest reported value of 1.7.

Lithium-sulfur batteries (LSBs) represent a promising energy storage technology with a potential for next-generation high-energy storage systems due to their high specific capacity, abundant resources, low cost, non-toxicity, and environmentally friendly characteristics. However, due to many critical limitations such as insulating nature of elemental sulfur, poor lithium polysulfide (LiPS) conversion kinetics, polysulfide shuttle effect resulting in capacity fading, and low cyclic stability, commercialization of LSBs are far from realization. One of the most essential strategy to mitigate the issues with LSBs is to prevent polysulfide shuttling thereby maximizing the sulfur utilization and enhance the overall Li-S battery performance. In this work, we develop a binder free three-dimensional hybrid cathode for Li-S battery using multiwall carbon nanotubes (CNTs) and molybdenum sulfide (MoS2) as a catalyst, collectively enhancing LiPS conversion and ion transport ability and hence increased energy density, both gravimetric and volumetric. Different uniform mixtures of CNTs, MoS2, and conductive carbon black are prepared and loaded with high sulfur loading of ~6 mg cm-2. Various electrochemical performance parameters influencing cathode performance with respect to both gravimetric and volumetric energy densities are studied. Parameters that help improve the overall battery performance are identified and discussed.

The increasing demand for clean and efficient energy storage in portable electronics, electric vehicles, and smart energy grid has spurred attention to develop advanced battery systems. Complementing the high theoretical specific capacity of sulfur cathode (∼1672 mAh/g), environmentally benign, and low-cost, Li-S batteries can meet the myriad needs of inexpensive and high energy density energy storage. However, the intrinsic drawbacks of poor cycle life and low charge efficiency in conventional Li-S batteries hinder the advancement of this alluring technology. Here, we propose a novel and facile synthesis of binder-free three-dimensional carbon nanotubes (3D CNTs)/sulfur (S) hybrid composite as an electrode material, where 3D CNTs provide a high conduction path and short diffusion length for Li-ions, while confining soluble poly-sulfides within the structure for high cycling performance. The unique binder free cathode design results in one of the highest sulfur loading of 8.33 mg/cm2 (∼55 wt% S in the cathode electrode) with excellent areal and specific capacity of 8.89 mAh/cm2 and 1068 mAh/g at 0.1C rate (∼1.4 mA/cm2) offering coulombic efficiency of greater than 95% for 150 cycles. The novel cell exhibits maximum specific energy of ∼1233 Wh/kg with a specific power of ∼476 W/kg, with respect to the mass of the cathode.

The effect of gamma-ray (γ-ray) irradiation on the material characteristics of nanometre scale films of molybdenum disulphide (MoS2) has been investigated. 3.2, 4.5, and 5.2 nm thick MoS2 films (measured by atomic force microscopy) were grown on Si by using a two-step synthesis method (sputtering of Mo, followed by sulphurisation). The samples were subsequently exposed to γ-ray irradiation (dose of 120 MRad). Dramatic chemical changes in the MoS2 films after irradiation were characterised by micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and optical microscopy. Micro-Raman spectroscopy showed the disappearance of the E 2g 1 and A 1g modes after irradiation. XPS revealed that the MoS2 crystal structure was converted to molybdenum oxide (MoO x ). It is hypothesised that S vacancies are formed due to the γ-ray irradiation, which subsequently transforms MoS2 to MoO x .

Recent advances in atomically thin two-dimensional transition metal dichalcogenides (2D TMDs) have led to a variety of promising technologies for nanoelectronics, photonics, sensing, energy storage, and opto-electronics, to name a few. This article reviews the recent progress in 2D materials beyond graphene and includes mainly transition metal dichalcogenides (TMDs) (e.g. MoS2, WS2, MoSe2, and WSe2). These materials are finding niche applications for next-generation electronics and optoelectronics devices relying on ultimate atomic thicknesses. Albeit several challenges in developing scalable and defect-free TMDs on desired substrates, new growth techniques compatible with traditional and unconventional substrates have been developed to meet the ever-increasing demand of high quality and controllability for practical applications. The fabrication of novel 2D TMDs that exhibit exotic functionalities and fundamentally new chemistry is highlighted. And finally, in parallel with the electronics, the considerable effort devoted to using these materials for energy and sensing applications is discussed in detail.

The lithium sulfur (Li-S) battery is an energy storage device beyond Li-ion batteries which presents unique polysulfide chemistry resulting in high theoretical capacity of 2,600 Wh/kg. However, the unwanted shuttling of soluble lithium polysulfides (LiPSs) such as Li2S8 and Li2S6, corrodes the Li anode by forming an inactive sulfide layer and limit the life cycle of the Li-S battery. In previous studies, pristine 2D materials were used as the catalyst to anchor the polysulfides in cathodes and prevent the shuttling effect. The weight loading and concentration of catalysts in cathode was too high for the practical application in Li-S battery. In our study, we synthesized novel lightweight 2D Mo0.5W0.5S2 catalyst on CNT paper as a sulfur host cathode to efficiently catalyze the polysulfide reactions. Our catalyst shows mixed 2H-1T phase resulting in enhanced polysulfide binding, conversion and electron transfer resulting in improved specific capacity of 1,228 mAh/g at 0.1 C. The accelerated transformation of the dissolved polysulfides to the insoluble LiPSs resulted in an improved cyclic stability upto 400 cycles, as compared to 100 cycles for pristine cathode. Our study shows novel approach with binder-free ultra-light weight catalytic cathodes for practical application of Li-S battery.

Self-activation is an ecological friendly and inexpensive process for the fabrication of large scale activated carbon (AC), which precludes the use of activating agents and takes advantage of the emitted gases from the simple pyrolysis of pine wood to stimulate the converted carbon. The tailoring of process parameters such as dwelling time assists in optimizing the pore size distribution comprised of meso- and micropores, offering favorable physical properties including specific surface area of 2738 m2 g−1 and specific pore volume of 2.209 cm3 g−1 for superior electrochemical performance of Li-ion batteries. The AC-based anode shows a high cycling stability with a reversible specific capacity of 384 mAh g−1 at 1C after 200 cycles, which is close to the theoretical specific capacity of graphite. The finding suggests that the self-activation process, a green, scalable, and efficient process, has great potential to be developed into next-generation high-performance electrode materials for electrochemical energy storage devices.

Layered molybdenum disulfide (MoS2) has attracted great attention owing to its unique properties. However, synthesizing large area thin film with high crystal quality and uniformity remains a challenge. The present study explores large scale MoS2 growth methods, i.e., two-step method of sputtering-chemical vapor deposition and direct sputtering method, and applies them to fabricate field effect transistors and supercapacitors, respectively. The thickness modulated MoS2 films by two-step method exhibited high field effect mobility [∼12.24 cm2/(V s)] and current on/off ratio (∼106). The direct sputtering of MoS2 demonstrated excellent electrochemical performance with a high capacitance (∼30 mF/cm2) and cyclic stability upto 5000 cycles. Our growth methods reported here for the large scale MoS2 with high uniformity can trigger the development of several important technologies in two-dimensional materials.

Carbon nanotubes (CNTs) have been considered as a potential anode material for next generation Lithium-ion batteries (LIBs) due to their high conductivity, flexibility, surface area, and lithium-ion insertion ability. However, the low mass loading and bulk density of carbon nanomaterials hinder their use in large-scale energy storage because their high specific capacity may not scale up linearly with the thickness of the electrode. To address this issue, a novel three-dimensional (3D) architecture is rationally designed by stacking layers of free-standing CNTs with the increased areal density to 34.9 mg cm −2 , which is around three-times higher than that of the state-of-the-art graphitic anodes. Furthermore, a thermal compression process renders the bulk density of the multi-stacked 3D CNTs to be increased by 1.85 g cm −3 , which yields an excellent volumetric capacity of 465 mAh cm −3 at 0.5C. Our proposed strategy involving the stacking of 3D CNT based layers and post-thermal compression provides a powerful platform for the utilization of carbon nanomaterials in the advanced LIB technology.

Alloying two-dimensional transition metal dichalcogenides (2D TMDs) is a promising avenue for band gap engineering. In addition, developing a scalable synthesis process is essential for the practical application of these alloys with tunable band gaps in optoelectronic devices. Here, we report the synthesis of optically uniform and scalable single-layer Mo

Two-dimensional transition metal dichalcogenides (2D TMDs) have gained great interest due to their unique tunable bandgap as a function of the number of layers. Especially, single-layer tungsten disulfides (WS2) is a direct band gap semiconductor with a gap of 2.1 eV featuring strong photoluminescence and large exciton binding energy. Although synthesis of MoS2 and their layer dependent properties have been studied rigorously, little attention has been paid to the formation of single-layer WS2 and its layer dependent properties. Here we report the scalable synthesis of uniform single-layer WS2 film by a two-step chemical vapor deposition (CVD) method followed by a laser thinning process. The PL intensity increases six-fold, while the PL peak shifts from 1.92 eV to 1.97 eV during the laser thinning from few-layers to single-layer. We find from the analysis of exciton complexes that both a neutral exciton and a trion increases with decreasing WS2 film thickness; however, the neutral exciton is predominant in single-layer WS2. The binding energies of trion and biexciton for single-layer WS2 are experimentally characterized at 35 meV and 60 meV, respectively. The tunable optical properties by precise control of WS2 layers could empower a great deal of flexibility in designing atomically thin optoelectronic devices.

Two dimensional (2D) Molybdenum disulfide (MoS2) has evolved as a promising material for next generation optoelectronic devices owing to its unique electrical and optical properties, such as band gap modulation, high optical absorption, and increased luminescence quantum yield. The 2D MoS2 photodetectors reported in the literature have presented low responsivity compared to silicon based photodetectors. In this study, we assembled atomically thin p-type MoS2 with graphene to form a MoS2/graphene Schottky photodetector where photo generated holes travel from graphene to MoS2 over the Schottky barrier under illumination. We found that the p-type MoS2 forms a Schottky junction with graphene with a barrier height of 139 meV, which results in high photocurrent and wide spectral range of detection with wavelength selectivity. The fabricated photodetector showed excellent photosensitivity with a maximum photo responsivity of 1.26 AW(-1) and a noise equivalent power of 7.8 × 10(-12) W/√Hz at 1440 nm.

Two dimensional (2D) layered materials have recently attracted significant research interest owing to their unique physical and chemical properties for efficient electrochemical energy storage devices. Here, we present a neoteric approach to fabricate high performance MoS2 thin film supercapacitor electrodes by using a direct magnetron sputtering technique. The novel three-dimensional (3D) porous structure of the MoS2 film exhibits an excellent capacitance of ∼330 F cm−3 along with a high volumetric power and energy density of 40–80 W cm−3 and 1.6–2.4 mW h cm−3, respectively. Moreover, the optimized MoS2 electrode shows an outstanding cyclic stability, yielding capacitance retention over 97% after 5000 cycles of charging/discharging. The contemporary approach to MoS2 supercapacitor electrode fabrication will enable new opportunities in flexible electronic and energy devices.

Two-dimensional MoS2 is a promising material for next-generation electronic and optoelectronic devices due to its unique electrical and optical properties including the band gap modulation with film thickness. Although MoS2 has shown excellent properties, wafer-scale production with layer control from single to few layers has yet to be demonstrated. The present study explored the large-scale and thickness-modulated growth of atomically thin MoS2 on Si/SiO2 substrates using a two-step sputtering–CVD method. Our process exhibited wafer-scale fabrication and successful thickness modulation of MoS2 layers from monolayer (0.72 nm) to multilayer (12.69 nm) with high uniformity. Electrical measurements on MoS2 field effect transistors (FETs) revealed a p-type semiconductor behavior with much higher field effect mobility and current on/off ratio as compared to previously reported CVD grown MoS2-FETs and amorphous silicon (a-Si) thin film transistors. Our results show that sputter–CVD is a viable method to synthes...

Among the candidates to replace Li-ion batteries, Li-S cells are an attractive option as their energy density is about five times higher (~2,600 Wh kg

Various approaches to improve the efficiency of Lithium ion batteries (LiB) by using Si have been suggested because Si has the highest known lithium capacity. Although Si is more than ten times higher capacity than existing graphite anodes, Si anodes have limited applications due to its high volume change during cycling. Here we demonstrated graphene/Si–CuO quantum dots (Gr/Si–CuO QD) layered structure as an efficient LiB anode which prevents large volume expansion of Si due to the presence of CuO–Cu3Si. By Electrophoresis Deposition technique, the multi-layer of graphene and Si–CuO QD has been successfully fabricated followed by annealing process to form Cu3Si interlayer as confirmed by High Resolution Transmission Electron Microscope-Energy Dispersive Spectroscopy, X-ray diffraction and Raman analyses. The annealed Gr/Si–CuO QD exhibit the initial gravimetric specific capacity of 2869 mAh g−1 which is five times higher than that of annealed graphene at 0.5C. After 100 cycles at 1C rate the capacity retains ∼71% and the excellent rate capability even at high C rate reveals controlled volume expansion owing to the multi layered architecture and the Cu3Si inter layer. The layered structure of Gr/Si–CuO QD electrode could be applied in next generation micro power sources.

Recent advances in atomically thin two-dimensional (2-D) materials have led to a variety of promising future technologies for post-CMOS nanoelectronics and energy generation. This review is an attempt to thoroughly illustrate the current status and future prospects for 2-D materials other than graphene (e.g., BN nanosheets, MoS2, NbSe2, WS2, etc.), which have already been contemplated for both low-end and high-end technological applications. An overview of the different synthesis techniques for 2-D materials is presented here, with an exploration of the potential for developing methods of controllable large scale synthesis. Furthermore, we summarize the underlying theories which correlate the structural and physical properties of 2-D materials with their state-of-the-art applications. Finally, we show that utilizing the unprecedented properties arising from these materials would lead to innovative devices. Such devices would significantly reduce both device dimensions and power consumption, as necessary f...