Creating high-energy facets on the surface of catalyst nanocrystals represents a promising method for enhancing their catalytic activity. Herein we show that crystal etching as the reverse process of crystal growth can directly endow nanocrystal surfaces with high-energy facets. The key is to avoid significant modification of the surface energies of the nanocrystal facets by capping effects from solvents, ions, and ligands. Using Cu nanocubes as the starting material, we have successfully demonstrated the creation of high-energy facets in metal nanocrystals by controlled chemical etching. The etched Cu nanocrystals with enriched high-energy {110} facets showed significantly enhanced activity toward CO2 reduction. We believe the etching-based strategy could be extended to the synthesis of nanocrystals of many other catalysts with more active high-energy facets.

In this study, we design a homogeneous system consisting of Ag nanoprisms and glucose oxidase (GOx) for simple, sensitive, and low-cost colorimetric sensing of glucose in serum. The unmodified Ag nanoprisms and GOx are first mixed with each other. Glucose is then added in the homogeneous mixture. Finally, the nanoplates are etched from triangle to round by H2O2 produced by the enzymatic oxidation, which leads to a more than 120 nm blue shift of the surface plasmon resonance (SPR) absorption band of the Ag nanoplates. This large wavelength shift can be used not only for visual detection (from blue to mauve) of glucose by naked eyes but for reliable and convenient glucose quantification in the range from 2.0 × 10(-7) to 1.0 × 10(-4) M. The detection limit is as low as 2.0 × 10(-7) M, because the used Ag nanoprisms possess (1) highly reactive edges/tips and (2) strongly tip sharpness and aspect ratio dependent SPR absorption. Owing to ultrahigh sensitivity, only 10-20 μL of serum is enough for a one-time determination. The proposed glucose sensor has great potential in the applications of point-of-care diagnostics, especially for third-world countries where high-tech diagnostics aids are inaccessible to the bulk of the population.

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A new benzoxazole-modified [PhSiO 1.5 ] 8 (OPS) benzoxazine (OPS−Bz) was synthesized and used to prepare polyhedral oligomeric silsesquioxane (POSS)/ polybenzoxazine (PBz) nanocomposites. Fourier transform infrared spectroscopy (FTIR), 1 H NMR, 29 Si NMR, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the structure of OPS−Bz. The high resolution transmission electron microscopy images of POSS/PBz(30/70) nanocomposites showed a well separated nanostructure of POSS with a typical phase size of 3−10 nm. POSS was highly dispersed in the polymer matrix because of the benzoxazole groups around the OPS molecular, in which the rigid benzoxazole groups increased the distance among the POSS molecules and reduced the aggregation of POSS nanoparticles. The TGA study showed these nanocomposites possess good thermal stability. Moreover, the dielectric constants and dielectric loss of these POSS/PBz nanocomposites were low and changed slightly at room temperature in the frequency range of 10 Hz to 1 MHz.

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The (Nb + In) co-doped TiO2 ceramics were synthesized by conventional solid-state sintering (CSSS) and spark plasma sintering (SPS) methods. The phases and microstructures were studied by X-ray diffraction, Raman spectra, field-emission scanning electron microscopy and transmission electron microscopy, indicating that both samples were in pure rutile phase while showing significant difference in grain size. The dielectric and I–V behaviors of SPS and CSSS samples were investigated. Though both possess colossal permittivity (CP), the SPS samples exhibited much higher dielectric permittivity/loss factor and lower breakdown electric field when compared to their CSSS counterparts. To further explore the origin of CP in co-doped TiO2 ceramics, the I–V behavior was studied on single grain and grain boundary in CSSS sample. The nearly ohmic I–V behavior was observed in single grain, while GBs showed nonlinear behavior and much higher resistance. The higher dielectric permittivity and lower breakdown electric field in SPS samples, thus, were thought to be associated with the feature of SPS, by which reduced space charges and/or impurity segregation can be achieved at grain boundaries. The present results support that the grain boundary capacitance effect plays an important role in the CP and nonlinear I–V behavior of (Nb + In) co-doped TiO2 ceramics.

Structural defects have been proven to determine many of the materials' properties. Here, we demonstrate a unique approach to the creation of Ag nanowires with high-density defects through controllable nanoparticles coalescence in one-dimensional pores of mesoporous silica. The density of defects can be easily adjusted by tuning the annealing temperature during synthetic process. The high-density defects promote the adsorption and activation of more reactants on the surface of Ag nanowires during catalytic reactions. As a result, the as-prepared Ag nanowires exhibit enhanced activities in catalyzing dehydrogenative coupling reaction of silane in terms of apparent activation energy and turnover frequency (TOF). We show further that the silane conversion rate can be enhanced by maximizing the defect density and thus the number of active sites on the Ag nanowires, reaching a remarkable TOF of 8288 h(-1), which represents the highest TOF that has been achieved by far on Ag catalysts. This work not only proves the important role of structural defects in catalysis but also provides a new and general strategy for constructing high-density defects in metal catalysts.

Designing the electrocatalysts that are stable and active for extensively adaptable water splitting is highly desirable for developing hydrogen based energy. IrO2 is a promising and widely used catalyst for the oxygen evolution reaction in commercial applications, but is rarely used for the hydrogen evolution reaction (HER), due to the high Gibbs free energy for hydrogen adsorption (ΔGH*). Herein, an approach to modify the electronic structure of IrO2 via cyclic voltammetry is proposed. In this process, Ir(+4) is partially reduced and trace Pt is simultaneously deposited on IrO2, which greatly lowers the ΔGH* and thus accelerates the reaction kinetics. The as‐prepared Pt–IrO2/CC with low noble metal loading (36.6 µg cm−2(Ir+Pt)) exhibits excellent HER activity with overpotentials of 5, 22, and 26 mV at 10 mA cm−2 in 0.5 m H2SO4, 1 m KOH, and 1 m phosphate buffer solution, respectively, making it possible to organize an all‐IrO2 based water electrolyzer. The Pt–IrO2/CC||IrO2/CC couple exhibits a promising activity and stability in pH‐universal conditions as well as natural seawater for H2 production. Density function theory calculations reveal that the optimized electronic structure of IrO2 balances the ΔGH*, resulting in a much enhanced HER performance.