材料科学最新文献

Nanophotonic metamaterials exhibit application potential in micro/nano-optics owing to their unique optical properties. However, achieving dual-band perfect absorption with high quality factor remains a challenge. This study proposes a metamaterial featuring symmetry-broken silicon nanodisk arrays, which enables dual-band high-Qperfect absorption by transforming bound states in the continuum (BIC) into quasi-BIC and exciting an anapole mode. Numerical simulations demonstrate that the structure achieves absorption rates of 99.19% and 99.76% at wavelengths of 1068.55 nm and 1106.17 nm, respectively, with narrow linewidths of 1.08 nm and 0.84 nm, corresponding toQ-factors as high as 989 and 1316. Due to the polarization sensitivity of BIC, the absorption peaks can be switched on and off by adjusting the incident light polarization angle, offering a novel strategy for optical switching. Furthermore, as a dual-channel refractive index sensor, the metamaterial exhibits excellent sensing performance, with sensitivities of 81.9 nmRIU-1and 139.5 nmRIU-1, and figures of merit of 75.83RIU-1and 166.1RIU-1. This work not only provides a new design route for ultra-high-Qdual-band perfect absorbers, but also offers technical support for cutting-edge applications such as dual-frequency channel sensor and photonic switching.

All-inorganic cesium lead halide perovskite quantum dots, CsPbX₃(X = Cl, Br, I), exhibit exceptional potential in nonlinear optical (NLO) applications. This is due to their outstanding optoelectronic properties, including high photoluminescence quantum yield, tunable band gaps, and strong absorption coefficients. However, their practical utility is severely limited by their environmental instability against ambient air and moisture. In this study, CsPbBr₃QDs were encapsulated in a SiO₂matrix using a sol-gel method to fabricate CsPbBr₃/SiO₂gel-glass composites. Structural characterization (transmission electron microscopy, x-ray diffraction, and Fourier transform infrared) confirmed the uniform dispersion and complete encapsulation of the QDs within the amorphous SiO₂network. Optical analyses revealed that the composites retained the intrinsic absorption and emission characteristics of the CsPbBr₃QDs (bandgap: 2.29 eV; fluorescence peak: 510 nm), while exhibiting tunable linear transmittance (50%-82%).Z-scan measurements under 532 nm picosecond pulsed laser excitation revealed significant nonlinear absorption coefficients (β) of up to 0.85 cm GW^-1and a low optical limiting threshold (OL) of 0.22 J cm^-2. Importantly, SiO₂encapsulation markedly enhanced the environmental stability of the CsPbBr₃QDs, and their NLO properties remained stable after 365 d of storage under ambient air conditions. This work provides a viable strategy for realizing halide perovskite-based OL devices and establishes a promising platform for further development. Future device-level integration and cycling tests will be essential for practical deployment.

The electrochemical reduction of CO₂ to formate provides a dual-purpose pathway to mitigate emissions and generate valuable fuels and chemicals. In this work, halide doping strategies (Cl^-, Br^-, and I^-) were employed to prepare Bi₂WO₆ nanosheets with tunable oxygen vacancy (O_v) concentrations for the electrocatalytic reduction of CO₂. The bromine-doped Bi₂WO₆ nanosheets (BWO-Br) achieve a Faradaic efficiency for formate (FE_formate) exceeding 90% over a wide potential window in an H-cell and reach a high current density of 496 mA cm^-2 in a flow cell. Density functional theory calculations reveal that bromine synergizes with O_v to generate electron-rich bismuth sites, thereby weakening the Bi-O bonds. In situ ATR-SEIRAS and Raman spectroscopy investigations further demonstrate that Br doping induces a rapid and favorable reconstruction during the reaction. This accelerated reconstruction process generates substantial tensile strain in the catalyst structure, which significantly enhances the adsorption of the *OCHO intermediate and ultimately boosts the performance of electrocatalytic CO₂ reduction to formate. This work provides valuable insights into the reconstruction dynamics jointly guided by Br and O_v, offering a rational principle for the design of high-performance CO₂ reduction electrocatalysts.

Although poly(vinyl alcohol) (PVA) has attracted much attention owing to its high strength, good processability, and excellent transparency, the application of PVA materials is still limited due to their intrinsically poor toughness. Herein, a strategy is addressed to construct a PVA-based composite film that simultaneously achieves high strength, transparency, and excellent toughness. Herein, cross-linkable poly(butyl acrylate-co-methyl methacrylate-co-3-(trimethoxysilyl)propyl methacrylate) (PBMM) nanoparticle emulsion was synthesized via one-step emulsion polymerization. By directly blending and drying the PBMM emulsion and PVA aqueous solution, the PVA-based film was obtained. The incorporation of 8.33 wt % PBM₂₅₀M₁ could significantly improve the toughness of the PVA film by 11.26 times, achieving the highest value of 158.7 MJ/m³. Furthermore, the resulting composite film maintained a high strength of 94.8 ± 4.8 MPa (even higher than that of PVA). Such excellent properties were ascribed to the chemical reaction and strong interfacial adhesion between PVA and the PBMM latex nanoparticles. This work paves a feasible avenue of manufacturing PVA-based composites with both high mechanical and desirable optical performance, which is still challenging in current industrial technologies.