Masson Jean-Francois, Wallace Gregory Q, Asselin Jérémie, Ten Andrey, Hojjat Jodaylami Maryam, Faulds Karen, Graham Duncan, Biggins John S, Ringe Emilie
Département de chimie, Quebec center for advanced materials, Regroupement québécois sur les matériaux de pointe, and Centre interdisciplinaire de recherche sur le cerveau et l'apprentissage, Université de Montréal, C.P. 6128 Succ. Centre-Ville, Montréal, QC Canada, H3C 3J7.
Centre for Molecular Nanometrology, Department of Pure and Applied Chemistry, Technology and Innovation Centre, University of Strathclyde, 99 George Street, Glasgow G1 1RD, U.K.
ACS Appl Mater Interfaces. 2023 Oct 4;15(39):46181-46194. doi: 10.1021/acsami.3c07880. Epub 2023 Sep 21.
Surface curvature can be used to focus light and alter optical processes. Here, we show that curved surfaces (spheres, cylinders, and cones) with a radius of around 5 μm lead to maximal optoplasmonic properties including surface-enhanced Raman scattering (SERS), photocatalysis, and photothermal processes. Glass microspheres, microfibers, pulled fibers, and control flat substrates were functionalized with well-dispersed and dense arrays of 45 nm Au NP using polystyrene--poly-4-vinylpyridine (PS--P4VP) and chemically modified with 4-mercaptobenzoic acid (4-MBA, SERS reporter), 4-nitrobenzenethiol (4-NBT, reactive to plasmonic catalysis), or 4-fluorophenyl isocyanide (FPIC, photothermal reporter). The various curved substrates enhanced the plasmonic properties by focusing the light in a photonic nanojet and providing a directional antenna to increase the collection efficacy of SERS photons. The optoplasmonic effects led to an increase of up to 1 order of magnitude of the SERS response, up to 5 times the photocatalytic conversion of 4-NBT to 4,4'-dimercaptoazobenzene when the diameter of the curved surfaces was about 5 μm and a small increase in photothermal effects. Taken together, the results provide evidence that curvature enhances plasmonic properties and that its effect is maximal for spherical objects around a few micrometers in diameter, in agreement with a theoretical framework based on geometrical optics. These enhanced plasmonic effects and the stationary-phase-like plasmonic substrates pave the way to the next generation of sensors, plasmonic photocatalysts, and photothermal devices.
表面曲率可用于聚焦光线并改变光学过程。在此，我们表明半径约为5μm的曲面（球体、圆柱体和圆锥体）可产生最大的光等离子体特性，包括表面增强拉曼散射（SERS）、光催化和光热过程。玻璃微球、微纤维、拉制纤维以及对照平面基底用聚苯乙烯 - 聚4 - 乙烯基吡啶（PS - P4VP）功能化，形成分散良好且密集排列的45nm金纳米颗粒（Au NP）阵列，并使用4 - 巯基苯甲酸（4 - MBA，SERS报告分子）、4 - 硝基苯硫酚（4 - NBT，对等离子体催化有反应）或4 - 氟苯基异氰化物（FPIC，光热报告分子）进行化学修饰。各种曲面基底通过在光子纳米射流中聚焦光线并提供定向天线来提高SERS光子的收集效率，从而增强了等离子体特性。光等离子体效应使SERS响应提高了多达1个数量级，当曲面直径约为5μm时，光催化将4 - NBT转化为4,4'-二巯基偶氮苯的转化率提高了5倍，光热效应也有小幅增加。综上所述，这些结果证明曲率增强了等离子体特性，并且对于直径约为几微米的球形物体，其效果最为显著，这与基于几何光学的理论框架一致。这些增强的等离子体效应以及类似固定相的等离子体基底为下一代传感器、等离子体光催化剂和光热器件铺平了道路。
