Thermally Stable Silicone Elastomer Composites Based on MoS2@Biomass-Derived Carbon with a High Dielectric Constant and Ultralow Loss for Flexible Microwave Electronics.

With the miniaturization and integration of electronic components in wireless communication and wearable devices, the demand for low-cost flexible composites with temperature-stable high dielectric constant and low loss has substantially increased. However, such comprehensive properties are fundamentally difficult to combine for conventional conductive and ceramic composites. Here, we develop silicone elastomer (SE) composites based on hydrothermally grown MoS2 on tissue paper-derived cellulose carbon (CC). Such design promoted the formation of microcapacitors, multiple interfaces, and defects reinforcing interfacial and defect polarizations and resulting in a high dielectric constant of 9.83 at 10 GHz with low filler loading of 15 wt %. Unlike highly conductive fillers, MoS2@CC with low conductivity ensured a very low loss tangent of 7.6 × 10-3, which was also influenced by the filler dispersion and adhesion to the matrix. Apart from breaking the typical conflict between high dielectric constant and low losses of traditional conductive composites, MoS2@CC SE composites were highly flexible with temperature-stable dielectric properties making them attractive as flexible substrates in microstrip antenna applications and extreme environment electronics. Moreover, recycling from waste tissue paper makes them potential candidates as low-cost and sustainable dielectric composites.

Design of highly sensitive and selective ethanol sensor based on α-Fe2O3/Nb2O5 heterostructure.

The introduction of heterostructures is a new approach in gas sensing due to their easy and quick transport of charges. Herein, facile hydrothermal and solid-state techniques are employed to synthesize an α-Fe2O3/Nb2O5 heterostructure. The morphology, microstructure, crystallinity and surface composition of the synthesized heterostructures are investigated by scanning electron microscope, transmission electron microscope, x-ray diffraction, x-ray photoelectron spectroscopy and Brunauer-Emmett-Teller analyses. The successful fabrication of the heterostructures was achieved via the mutual incorporation of α-Fe2O3 nanorods with Nb2O5 interconnected nanoparticles (INPs). A sensor based on the α-Fe2O3(0.09)/Nb2O5 heterostructure with a high surface area exhibited enhanced gas-sensing features, maintaining high selectivity and sensitivity, and a considerable recovery percentage towards ethanol gas. The sensing response of the α-Fe2O3(0.09)/Nb2O5 heterostructure at lower operating temperature (160 °C) is around nine times higher than a pure Nb2O5 (INP) sensor at 180 °C with the flow of 100 ppm ethanol gas. The sensors also show excellent selectivity, good long-term stability and a rapid response/recovery time (8s/2s, respectively) to ethanol. The superior electronic conductivity and upgraded sensitivity performance of gas sensors based on the α-Fe2O3(0.09)/Nb2O5 heterostructure are attributed due to its unique structural features, high specific surface area and the synergic effect of the n-n heterojunction. The promising results demonstrate the potential application of the α-Fe2O3(0.09)/Nb2O5 heterostructure as a good sensing material for the fabrication of ethanol sensors.

A Potential Checkmate to Lead: Bismuth in Organometal Halide Perovskites, Structure, Properties, and Applications.

The remarkable optoelectronic properties and considerable performance of the organo lead-halide perovskites (PVKs) in various optoelectronic applications grasp tremendous scientific attention. However, the existence of the toxic lead in these compounds is threatening human health and remains a major concern in the way of their commercialization. To address this issue, numerous nontoxic alternatives have been reported. Among these alternatives, bismuth-based PVKs have emerged as a promising substitute because of similar optoelectronic properties and extended environmental stability. This work communicates briefly about the possible lead-alternatives and explores bismuth-based perovskites comprehensively, in terms of their structures, optoelectronic properties, and applications. A brief description of lead-toxification is provided and the possible Pb-alternatives from the periodic table are scrutinized. Then, the classification and crystal structures of various Bi-based perovskites are elaborated on. Detailed optoelectronic properties of Bi-based perovskites are also described and their optoelectronic applications are abridged. The overall photovoltaic applications along with device characteristics (i.e., V OC, J SC, fill factor, FF, and power conversion efficiency, PCE), fabrication method, device architecture, and operational stability are also summarized. Finally, a conclusion is drawn where a brief outlook highlights the challenges that hamper the future progress of Bi-based optoelectronic devices and suggestions for future directions are provided.

Development of high-performance sensor based on NiO/SnO2 heterostructures to study sensing properties towards various reducing gases.

In this work, we report the spontaneous formation of NiO nanoparticles-decorated onto smooth SnO2 nanofibers, which is an inexpensive and scalable method for yielding a high composite surface area via a simple two-step synthesis process based on electrospinning and the hydrothermal method. A Nickel Oxide proton-conducting electrolyte is deposited homogeneously over a large surface area in a transparent solution, mixed and decorated onto Tin dioxide nanofibers, as evidenced by cross sectional imaging of the electrospun nanofibers. The composite based on nanoparticle-decorated fibers enlarges the surface area of the exposed electrolyte, which fundamentally improves the overall gas sensing performance. The crystal structure, morphology, and physio-chemical surface state of the NiO/SnO2-based specimen are comprehensively examined using XRD, SEM, TEM, HRTEM, EDX, and photoelectron (XPS) spectroscopy. The composite based on NiO/SnO2 nanoparticle-decorated fibers exhibits an optimistic mesoporous nature with a huge specific area, which is key for superior gas sensors. The result reveals that NiO/SnO2 nanoparticle-decorated fibers with an average size of 180-260 nm in diameter, where the average length of fibers was about 1.5 µm. The composite-based heterojunction of NiO/SnO2 nanoparticle-decorated fibers enhances the adsorption of oxygen molecules, which show fast response, good selectivity and quick recovery speed against ethanol gas at an optimal temperature of about 160 °C. The maximum sensitivity response of the sensor-based composite NiO/SnO2 nanoparticle-decorated fibers was 23.87 in respect of 100 ppm ethanol gas at a low temperature of 160 °C; this is approximately about 7.2 times superior to that of pure SnO2 nanofibers. The superior gas sensing capabilities of a composite based on NiO/SnO2 nanoparticle-decorated fibers may be attributable to the enhanced catalytic effect of the small sized NiO nanoparticles on smooth SnO2 nanofibers, together with the p/n heterojunction effects between NiO and SnO2 heterostructures.

A novel ethanol gas sensor based on α-Bi2Mo3O12/Co3O4 nanotube-decorated particles.

A novel composite based on α-Bi2Mo3O12/Co3O4 nanotube-decorated particles was successfully synthesized using a highly efficient and facile two step system using electrospinning and hydrothermal techniques. The small size Co3O4 nanoparticles were uniformly and hydrothermally developed on the electrospun α-Bi2Mo3O12 nanotubes. The pure α-Bi2Mo3O12 nanofibers and composite based on α-Bi2Mo3O12/Co3O4 were examined using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) analyses. From the BET measurements, the composite based on α-Bi2Mo3O12/Co3O4 exhibits a large specific surface area of 54 m2 g-1 with mesopore diameter ranges of 2-10 nm, which is mainly attributed to the remarkable and dominant enhancement in gas sensing as compared to that of the pure α-Bi2Mo3O12 nanofibers (38 m2 g-1) and Co3O4 nanoparticles (32 m2 g-1), respectively. In this work, the novel composite based on α-Bi2Mo3O12/Co3O4 presented a high sensitivity of 30.25 with a quick response/recovery speed towards 100 ppm ethanol at an optimal working temperature of 170 °C, as compared to the pure α-Bi2Mo3O12 nanofibers and Co3O4 nanoparticles, which display a sensitivity of 13.10 and 2.99 at an optimal working temperature of 220 °C and 280 °C. The sensing performance of the composite based on the α-Bi2Mo3O12/Co3O4 sensor exhibits a superior sensing performance towards ethanol, which might be owed to the enormous number of superficial oxygen species, the small size catalytic effect of the Co3O4 nanoparticles and the interfacial effect formed between the n-type α-Bi2Mo3O12 and p-type Co3O4 leading to a high charge carrier concentration. This is a novel investigation of a composite based on an α-Bi2Mo3O12/Co3O4 sensor in the gas sensing era, which might be of vital importance in applications in the advanced gas sensing field.

Two-Dimensional SnSe2 /CNTs Hybrid Nanostructures as Anode Materials for High-Performance Lithium-Ion Batteries.

Tin diselenide (SnSe2 ), as an anode material, has outstanding potential for use in advanced lithium-ion batteries. However, like other tin-based anodes, SnSe2 suffers from poor cycle life and low rate capability due to large volume expansion during the repeated Li+ insertion/de-insertion process. This work reports an effective and easy strategy to combine SnSe2 and carbon nanotubes (CNTs) to form a SnSe2 /CNTs hybrid nanostructure. The synthesized SnSe2 has a regular hexagonal shape with a typical 2D nanostructure and the carbon nanotubes combine well with the SnSe2 nanosheets. The hybrid nanostructure can significantly reduce the serious damage to electrodes that occurs during electrochemical cycling processes. Remarkably, the SnSe2 /CNTs electrode exhibits a high reversible specific capacity of 457.6 mA h g-1 at 0.1 C and 210.3 mA h g-1 after 100 cycles. At a cycling rate of 0.5 C, the SnSe2 /CNTs electrode can still achieve a high value of 176.5 mA h g-1 , whereas a value of 45.8 mA h g-1 is achieved for the pure SnSe2 electrode. The enhanced electrochemical performance of the SnSe2 /CNTs electrode demonstrates its great potential for use in lithium-ion batteries. Thus, this work reports a facile approach to the synthesis of SnSe2 /CNTs as a promising anode material for lithium-ion batteries.

A Case Of Metabolic Syndrome.

This case report illustrates a 40-year-old woman who presented with chest discomfort that was subsequently diagnosed to have metabolic syndrome. Metabolic syndrome is a common condition associated with increased cardiovascular morbidity and mortality. As primary care providers, we should be detect this condition early, intervene and prevent appropriately before complications occur.