Effects of morphologies on acetone-sensing properties of tungsten trioxide nanocrystals

In this work, triclinic WO₃ nanoplates and WO₃ nanoparticles were comparatively investigated as sensing materials to detect acetone vapors. Single-crystalline WO₃ nanoplates with large side-to-thickness ratios were synthesized via a topochemical conversion from tungstate-based inorganic-organic hybrid nanobelts, and the WO₃ nanoparticles were obtained by calcining commercial H₂WO₄ powders at 550 °C. The acetone-sensing properties were evaluated by measuring the change in electrical resistance of the WO₃ sensors before and after exposure to acetone vapors with various concentrations. The WO₃ nanoplate sensors showed a high and stable sensitive response to acetone vapors with a concentration range of 2-1000 ppm, and the sensitivity was up to 42 for 1000 ppm of acetone vapor operating at 300 °C. The response and recovery times were as short as 3-10 s and 12-13 s, respectively, for the WO₃ nanoplate sensors when operating at 300 °C. The acetone-sensing performance of the WO₃ nanoplate sensors was more excellent than that of the WO₃ nanoparticle sensors under a similar operating condition. The enhancement of the WO₃ nanoplate sensors in the acetone-sensing property was attributed to the poriferous textures, single-crystalline microstructures and high surface areas of the aggregates consisting of WO₃ nanoplates, which were more favorable in rapid and efficient diffusion of acetone vapors than the WO₃ nanoparticles.     

Effect of the stirring rate on physical and electrochemical properties of LiMnPO4 nanoplates prepared in a polyol process

In a polyol approach to make olivine-typed LiMnPO₄ nanoplates, the effect of the stirring rate on physical and electrochemical properties of the obtained sample has been symmetrically investigated for the first time. The as-prepared powders exhibit well crystalline olivine structure as presented by X-ray diffraction analysis. The secondary particles with a size of 2–3 μm are composed of aggregated nanoplates as verified by particle size analysis and field emission scanning electron microscopy measurement. Transmission electron microscopy presents that the nanoplate is about 18 nm thick along a-axis. The discharge capacity of the sample prepared under a stirring rate of 700 rpm reaches 150 mAh g⁻¹ when cycled at 0.05C after a few cycles.     

A simulation study of thin film tandem solar cells with a nanoplate absorber bottom cell

A tandem thin film solar cell with a nanoplate absorber bottom cell that can solve the trade-off between light absorption and carrier transport in thin film solar cell is investigated. This structure has an n-type microcrystalline silicon nanoplate array on the substrate, and the p- and i-layers are sequentially grown along the surface of each n-type microcrystalline silicon nanoplate for bottom cell. After above bottom cell is fabricated, a similar process is used to fabricate an amorphous Si p-i-n top cell. High-aspect-ratio width/height nanoplates allow for the use of a material with sufficient thickness to obtain good optical absorption while simultaneously providing short collection lengths for excited carriers perpendicular to light absorption. The power conversion efficiency of nanoplate solar cells with 15,000 nm plate height is around 10%, which is an approximately 40% enhancement over a planar solar cell with a similar layer stack.     

Nanoplates of α-SnWO4 and SnW3O9 prepared via a facile hydrothermal method and their gas-sensing property

Nanoplates of α-SnWO₄ and SnW₃O₉ were selectively synthesized in large scale via a facile hydrothermal reaction method. The final products obtained were dependent on the reaction pH and the molar ratio of W⁶⁺ to Sn²⁺ in the precursors. The as-prepared nanoplates of α-SnWO₄ and SnW₃O₉ were characterized by X-ray powder diffraction (XRD), N₂-sorption BET surface area, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The XPS results showed that Sn exists in divalent form (Sn²⁺) in SnW₃O₉ as well as in α-SnWO₄. The gas-sensing performances of the as-prepared α-SnWO₄ and SnW₃O₉ toward H₂S and H₂ were investigated. The hydrothermal prepared α-SnWO₄ showed higher response toward H₂ than that prepared via a solid-state reaction due to the high specific surface area. The gas-sensing property toward H₂S as well as H₂ over SnW₃O₉ was for the first time reported. As compared to α-SnWO₄, SnW₃O₉ exhibits higher response toward H₂S and its higher response can be well explained by the existence of the multivalent W (W⁶⁺/W⁴⁺) in SnW₃O₉.     

A facile aqueous-phase route for the synthesis of silver nanoplates

A new seed-mediated method for the synthesis of silver nanoplates is reported, in which tannin (C₇₆H₅₂O₄₆) is used to reduce silver salt in aqueous solution. This synthesis is performed at room temperature, and doesn't need any surfactant or polymer to direct the anisotropic growth. The obtained nanoplates exhibit polygonal morphologies and their size can be tuned through adjusting the amounts of seeds. Due to the anisotropic shape feature, the absorption spectra of the nanoplates prove to be quite different from that of spherical nanoparticles.     

Buckling analysis of micro-/nano-scale plates based on two-variable refined plate theory incorporating nonlocal scale effects

This article presents the buckling analysis of isotropic nanoplates using the two variable refined plate theory and nonlocal small scale effects. The two variable refined plate theory takes account of transverse shear effects and parabolic distribution of the transverse shear strains through the thickness of the plate, hence it is unnecessary to use shear correction factors. Nonlocal governing equations of motion for the nanoplate are derived from the principle of virtual displacements. The closed-form solution for buckling load of a simply supported rectangular nanoplate subjected to in-plane loading has been obtained by using the Navier’s method. Numerical results obtained by the present theory are compared with available exact solutions in the literature. The effect of nonlocal scaling parameter, mode numbers and aspect ratios of the nanoplates on buckling load are investigated and discussed in detail in the present work. It can be concluded that the present theory, which does not require shear correction factor, is not only simple but also comparable to the first-order and higher order shear deformable theory.     

基于纳米石墨烯整理的棉织物防紫外线性能分析

研究纳米石墨烯涂层整理棉织物的防紫外线性能。采用石墨烯纳米片(GNP)作为紫外线吸收剂,水溶性聚氨酯(WPU)为黏合助剂,通过轧-烘-焙方法对棉织物进行涂层整理并研究其性能。通过扫描电子显微镜和傅里叶红外分析光谱表征分析改性棉织物的表观形态和内部结构;采用紫外线防护系数(UPF)评估其防紫外线性能。结果表明:经石墨烯处理后的棉织物展现出较强的紫外线防护性能,当石墨烯添加量为0.4%(质量分数)时,其UPF值达到356.74,是未处理织物的10倍。认为:整理后的织物可以应用于紫外线防护服装和可穿戴设备等。     

Influence of cobalt dopant in NiFe2-xCoxO4 (0≤x≤2) on electrochemical catalytic properties

Environmental pollution has increased owing to the excessive consumption of fossil fuels. Thus, the combustion of which does not emit pollutants, has attracted attention for as an alternative fuel in various energy application systems. Using hydrogen energy has considered as an environmentally friendly solution to significantly reduce the dependency on fossil fuels and it can be produced by electrochemical water splitting. However, the sluggish kinetic reaction of the oxygen evolution reaction (OER) during electrochemical water splitting reduces the efficiency of hydrogen energy. Therefore, an excellent electrochemical catalyst with superior electrochemical activity in OER is required to increase the energy conversion efficiency. In this study, a NiFe_2-xCo_xO₄ (0 ≤ x ≤ 2) electrochemical catalyst was prepared by hydrothermal synthesis by controlling the amount of Co dopant. The influence of Co doping on the electrochemical catalytic activity of the prepared sample was evaluated by comparing the oxygen vacancies, bandgap, macroporosity and active surface area. Previous research have reported that abundant oxygen vacancies can improve the electrochemical catalytic activity. However, NiCo₂O₄ with the least number of oxygen vacancies exhibited excellent bifunctional catalytic activity for OER/oxygen reduction reaction (ORR) owing to the development of macropore, large active surface areas, and lower bandgap. Therefore, the bandgap and porosity such as macroporosity, large surface area, are an important factor that exert a greater influence than oxygen vacancies in electrochemical catalysts.     

Effect of nitrate ion on formation of TiO2 nanoplate structure in hydrothermal solution

Nanoplate structure of TiO₂ was synthesized by surfactant-assisted hydrothermal method. The existence of nitrate ion with a high concentration prohibited the rolling of the nanosheets and played the key role on the formation of nanoplates of titanate. After calcinations, the titanate was transformed into TiO₂ nanoplates (anatase) of micrometer-size with 20-30 nm in thickness.     

Facile size and shape control of templated Au nanoparticles under microwave irradiation

In this work we prepared icosahedral gold particles and gold nanoplates using potassium tetrachloroaurate as precursor and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers as both reductant and capping agent under microwave irradiation. The products were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The size and shape of the resultant nanoparticles could be tuned by changing the chloride ion dosage and reaction temperature. With lower dosage of chloride ion, a lower proportion of irregular shaped nanoparticles and smaller gold decahedra and icosahedra were observed. Increasing the molecular ratio of [AuCl₄]/[Cl⁻] and reaction temperature could increase the proportion of gold nanoplates in the final product. Typically when the reaction proceeded at 120 °C with [AuCl₄]/[Cl⁻] = 10, > 90% of the product was nanoplatelets.