Mesostructured Arrays of Nanometer-spaced Gold Nanoparticles for Ultrahigh Number Density of SERS Hot Spots

Autor: Jhe-Wei Chang, Wei-Tsung Chuang, Ying-Jen Shiu, Chun-Jen Su, Michitoshi Hayashi, Hu-Cin Jeng, U-Ser Jeng, Chiao-Cheng Huang, Chung-Yuan Mou, Shiaw-Woei Chen, An-Chung Su, Ying-Huang Lai, Yao-Chang Lee
Rok vydání: 2014
Předmět:
Zdroj: Advanced Functional Materials. 24:2544-2552
ISSN: 1616-301X
DOI: 10.1002/adfm.201303724
Popis: A novel one-trough synthesis via an air-water interface is demonstrated to provide hexagonally packed arrays of densely spaced metallic nanoparticles (NPs). In the synthesis, a mesostructured polyoxometalate (POM)-silicatropic template (PSS) is first self-assembled at the air-water interface; upon UV irradiation, anion exchange cycles enable the free-floating PSS film to continuously uptake gold precursors from the solution subphase for diffusion-controlled and POM-site-directed photoreduction inside the silica channels. NPs ≈ 2 nm can hence be homogeneously formed inside the silica-surfactant channels until saturation. As revealed via X-ray diffraction, small-angle X-ray scattering (SAXS), grazing incidence SAXS, and transmission electron microscopy, the Au NPs directed by the PSS template are arrayed into a 2D hexagonal lattice with inter-channel spacing of 3.2 nm and a mean along-channel NP spacing of 2.8 nm. This corresponds to an ultra-high number density (≈1019 NPs cm−3) of narrowly spaced Au NPs in the Au-NP@PSS composite, leading to 3D densely deployed hot-spots along and across the mesostructured POM-silica channels for surface-enhanced Raman scattering (SERS). Consequently, the Au-NP@PSS composite exhibits prominent SERS with 4-mercaptobenzoic acid (4-MBA) adsorbed onto Au NPs. The best 4-MBA detection limit is 5 nm, with corresponding SERS enhancement factors above 108.
Databáze: OpenAIRE
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