2D layered materials with sensitive surfaces are promising materials for use in chemical sensing devices, owing to their extremely large surface‐to‐volume ratios. However, most chemical sensors based ...on 2D materials are used in the form of laterally defined active channels, in which the active area is limited to the actual device dimensions. Therefore, a novel approach for fabricating self‐formed active‐channel devices is proposed based on 2D semiconductor materials with very large surface areas, and their potential gas sensing ability is examined. First, the vertical growth phenomenon of SnS2 nanocrystals is investigated with large surface area via metal‐assisted growth using prepatterned metal electrodes, and then self‐formed active‐channel devices are suggested without additional pattering through the selective synthesis of SnS2 nanosheets on prepatterned metal electrodes. The self‐formed active‐channel device exhibits extremely high response values (>2000% at 10 ppm) for NO2 along with excellent NO2 selectivity. Moreover, the NO2 gas response of the gas sensing device with vertically self‐formed SnS2 nanosheets is more than two orders of magnitude higher than that of a similar exfoliated SnS2‐based device. These results indicate that the facile device fabrication method would be applicable to various systems in which surface area plays an important role.
A novel approach for fabricating self‐formed active‐channel devices based on 2D semiconductor materials with very large surface areas is proposed and their potential gas sensing ability is examined. The device exhibits extremely high response values and this novel fabrication method is expected to find use in various applications where surface area plays an important role in function.
NbN coatings were deposited by multi-arc ion plating at different nitrogen partial pressure (PN) to improve the corrosion resistance and conductivity of metallic bipolar plates. With increasing PN, ...the phase composition of the coating transformed from a mixture of β-Nb2N and δ’-NbN to δ-NbN, which was accompanied by grain refinement. The coating deposited at a relatively high PN (3.5 Pa) exhibited the lowest ICR and corrosion current density of 12.75 mΩ·cm2 and 2.619 × 10−6 A/cm2, respectively. The influence of the phase composition, microstructure, and surface morphology on the anti-corrosion behavior and conductivity of the coating were analyzed in detail.
•NbN coatings were deposited by multi-arc ion plating at various nitrogen partial pressures.•The NbN coating deposited at a relatively high nitrogen partial pressure possessed better properties.•The influence of the phase composition, microstructure, and morphology on the properties of the coated-SS were analyzed.
Transparent electrodes have been widely used in electronic devices such as solar cells, displays, and touch screens. Highly flexible transparent electrodes are especially desired for the development ...of next generation flexible electronic devices. Although indium tin oxide (ITO) is the most commonly used material for the fabrication of transparent electrodes, its brittleness and growing cost limit its utility for flexible electronic devices. Therefore, the need for new transparent conductive materials with superior mechanical properties is clear and urgent. Ag nanowire (AgNW) has been attracting increasing attention because of its effective combination of electrical and optical properties. However, it still suffers from several drawbacks, including large surface roughness, instability against oxidation and moisture, and poor adhesion to substrates. These issues need to be addressed before wide spread use of metallic NW as transparent electrodes can be realized. In this study, we demonstrated the fabrication of a flexible transparent electrode with superior mechanical, electrical and optical properties by embedding a AgNW film into a transparent polymer matrix. This technique can produce electrodes with an ultrasmooth and extremely deformable transparent electrode that have sheet resistance and transmittance comparable to those of an ITO electrode.
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•NiCo nanoparticles and single-atoms confined by nitrogen doped carbon nanotubes are synthesized.•NiCo-N-CNTs-900 requires lower overpotential at 10 mA cm−2 in OER and HER than the ...Ni-N-CNTs-900 and Co-N-CNTs-900.•Highly dispersed NiCo nanoalloys and Ni/Co single-atoms structure boost OER and HER.•A water electrolyzer using NiCo-N-CNTs-900 exhibits low cell voltage than the Pt/C//RuO2 couple.
Finding robust, high-efficiency, noble-metal-free electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) particularly at a low overpotential is a crucial endeavor for water electrolyzer-based green H2 harvesting, but challenges remain. Fortunately, atomically dispersed metal catalysts hold great potential for OER and HER owing to the exclusive electronic structure and maximized atom utilization, however, the insufficient population of reactive sites and unfortunate electrical conductivity seriously limit their performance. Herein, we rationally designed and synthesized a single-atom catalyst consisting of atomic Co and Ni with NiCo alloys encapsulated nitrogen-doped carbon nanotubes (N-CNTs). The NiCo-N-CNTs catalyst annealed at 900 °C (NiCo-N-CNTs-900) displays ultralow overpotential of 210 mV and 54 mV at 10 mA/cm2 for OER and HER, respectively, which are attributed to the robust synergistic effects of Ni/Co single atoms and NiCo nanoalloys. Furthermore, NiCo-N-CNTs-900 electrode exhibits higher mass activity of 2188 A/gNiCo and 468.75 A/gNiCo and turnover frequency of 0.679 O2 s−1 and 0.285 H2 s−1 for OER and HER, respectively, which is much better than those of commercial RuO2 and Pt/C catalysts. We further employed the NiCo-N-CNTs-900 as both anode and cathode catalyst for constructing a two-electrode electrolyzer, generating a current density of 10 mA/cm2 at a low cell voltage of 1.483 V, surpassing the benchmark Pt/C//RuO2 pair. This work not only provides a robust and effective non-precious metal catalyst but also a facile, efficient method to fabricate atomically dispersed metal atoms integrated with alloys for clean hydrogen production and beyond.
Here, we report that Nb doping of two-dimensional (2D) MoSe2 layered nanomaterials is a promising approach to improve their gas sensing performance. In this study, Nb atoms were incorporated into a ...2D MoSe2 host matrix, and the Nb doping concentration could be precisely controlled by varying the number of Nb2O5 deposition cycles in the plasma enhanced atomic layer deposition process. At relatively low Nb dopant concentrations, MoSe2 showed enhanced device durability as well as NO2 gas response, attributed to its small grains and stabilized grain boundaries. Meanwhile, an increase in the Nb doping concentration deteriorated the NO2 gas response. This might be attributed to a considerable increase in the number of metallic NbSe2 regions, which do not respond to gas molecules. This novel method of doping 2D transition metal dichalcogenide-based nanomaterials with metal atoms is a promising approach to improve the performance such as stability and gas response of 2D gas sensors.
High‐performance electrocatalysts, especially those consisting of earth abundant elements with low cost, are highly desirable for oxygen reduction reaction (ORR). However, design of well‐dispersed ...ORR catalysts that are efficient in both acidic and alkaline media remains challenging. Herein, we report a phosphate‐regulated synthesis with phytic acid, by dispersing the active sites in the carbon nanosheets to obtain Fe2P/FeP nanoparticles encapsulated in P, N‐doped carbon (PNC). The active sites of Fe2P/FeP particles and P, N‐doping sites have a synergistic effect on the ORR reaction. The Fe2P/FeP‐PNC catalyst exhibits good ORR performance and stability in alkaline media. The half‐wave potential (0.85 V), and 5 mV shift after 5000 cycles of stability test for Fe2P/FeP‐PNC catalyst exceed those of commercial Pt/C (E1/2=0.84 V, 20 mV shift) under alkaline condition. The catalyst presents a half‐wave potential of 0.70 V and limited current density of 5.31 mA cm−2 in acidic media. We demonstrate a Zn‐air battery and a PEMFC with the Fe2P/FeP‐PNC as the cathodes, showing a high power density of 156.68 mW cm−2 and 144 mW cm−2 respectively in either the alkaline or acidic electrolytes.
Fe2P/FeP nanoparticles dispersed on P, N co‐doped carbon nanosheets with a balance between graphitization and defects present good ORR activity and durability in both alkaline and acidic conditions.
White-light-emitting single molecules are promising materials for use in a new generation of displays and light sources because they offer the possibility of simple fabrication with perfect color ...reproducibility and stability. To realize white-light emission at the molecular scale, thereby eliminating the detrimental concentration- or environment-dependent energy transfer problem in conventional fluorescent or phosphorescent systems, energy transfer between a larger band-gap donor and a smaller band-gap acceptor must be fundamentally blocked. Here, we present the first example of a concentration-independent ultimate white-light-emitting molecule based on excited-state intramolecular proton transfer materials. Our molecule is composed of covalently linked blue- and orange-light-emitting moieties between which energy transfer is entirely frustrated, leading to the production of reproducible, stable white photo- and electroluminescence.
Small machines are highly promising for future medicine and new materials. Recent advances in functional nanomaterials have driven the development of synthetic inorganic micromachines that are ...capable of efficient propulsion and complex operation. Miniaturization and large‐scale manufacturing of these tiny machines with true nanometer dimension are crucial for compatibility with subcellular components and molecular machines in operation. Here, block copolymer lithography is combined with atomic layer deposition for wafer‐scale fabrication of ultrasmall coaxial TiO2/Pt nanotubes as catalytic rocket engines with length below 150 nm and a tubular reactor size of only 20 nm, leading to the smallest man‐made rocket engine reported to date. The movement of the nanorockets is examined using dark‐field microscopy particle tracking and dynamic light scattering. The high catalytic activity of the Pt inner layer and the reaction confined within the extremely small nanoreactor enable highly efficient propulsion, achieving speeds over 35 µm s−1 at a low Reynolds number of <10−5. The collective movements of these nanorockets are able to efficiently power the directional transport of significantly larger passive cargo.
Atomic layer deposition is combined with block copolymer lithography for wafer‐scale fabrication of ultrasmall coaxial TiO2/Pt nanotubes as catalytic nanorockets, leading to the smallest man‐made rocket engines reported to date. The high catalytic activity of the Pt inner layer and the reaction confined within the 20 nm nanoreactor enable an efficient propulsion at a low Reynolds number of <10−5.
Hybrid tandem solar cells comprising an inorganic bottom cell and an organic top cell have been designed and fabricated. The interlayer combination and thickness matching were optimized in order to ...increase the overall photovoltaic conversion efficiency. A maximum power conversion efficiency of 5.72% was achieved along with a Voc of 1.42 V, reaching as high as 92% of the sum of the subcell Voc values.
We report the successful synthesis of surface defective small size (SS) SnO₂ nanoparticles (NPs) by adopting a low temperature surfactant free solution method. The structural properties of the NPs ...were analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The presence of surface defects, especially oxygen vacancies, in the sample were characterized using micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and photoluminescence emission. The Brunauer⁻Emmet⁻Teller (BET) nitrogen adsorption⁻desorption isotherms demonstrated the superior textural properties (high surface area and uniform pore size) of SS SnO₂ compared to large size (LS) SnO₂. A comparable study was drawn between SS SnO₂ and LS SnO₂ NPs and a significant decrease in the concentration of surface defects was observed for the LS sample. The results showed that surface defects significantly depend upon the size of the NPs. The surface defects formed within the band gap energy level of SnO₂ significantly participated in the recombination process of photogenerated charge carriers, improving photochemical properties. Moreover, the SS SnO₂ showed superior photoelectrochemical (PEC) and photocatalytic activities compared to the LS SnO₂. The presence of a comparatively large number of surface defects due to its high surface area may enhance the photochemical activity by reducing the recombination rate of the photogenerated charges.
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