Koneti Siddardha, Borges Joel, Roiban Lucian, Rodrigues Marco S, Martin Nicolas, Epicier Thierry, Vaz Filipe, Steyer Philippe
Université Lyon, INSA-Lyon, MATEIS UMR CNRS 5510 , 21 Avenue Jean Capelle , 69621 Villeurbanne Cedex , France.
Centro de Física , Universidade do Minho , Campus de Gualtar , 4710 057 Braga , Portugal.
ACS Appl Mater Interfaces. 2018 Dec 12;10(49):42882-42890. doi: 10.1021/acsami.8b16436. Epub 2018 Nov 28.
Plasmonic Au nanoparticles (AuNPs) embedded into a TiO dielectric matrix were analyzed by combining two-dimensional and three-dimensional electron microscopy techniques. The preparation method was reactive magnetron sputtering, followed by thermal annealing treatments at 400 and 600 °C. The goal was to assess the nanostructural characteristics and correlate them with the optical properties of the AuNPs, particularly the localized surface plasmon resonance (LSPR) behavior. High-angle annular dark field-scanning transmission electron microscopy results showed the presence of small-sized AuNPs (quantum size regime) in the as-deposited Au-TiO film, resulting in a negligible LSPR response. The in-vacuum thermal annealing at 400 °C induced the formation of intermediate-sized nanoparticles (NPs), in the range of 10-40 nm, which led to the appearance of a well-defined LSPR band, positioned at 636 nm. Electron tomography revealed that most of the NPs are small-sized and are embedded into the TiO matrix, whereas the larger NPs are located at the surface. Annealing at 600 °C promotes a bimodal size distribution with intermediate-sized NPs embedded in the matrix and big-sized NPs, up to 100 nm, appearing at the surface. The latter are responsible for a broadening and a redshift, to 645 nm, in the LSPR band because of increase of scattering-to-absorption ratio. Beyond differentiating and quantifying the surface and embedded NPs, electron tomography also provided the identification of "hot-spots". The presence of NPs at the surface, individual or in dimers, permits adsorption sites for LSPR sensing and for surface-enhanced spectroscopies, such as surface-enhanced Raman scattering.
通过结合二维和三维电子显微镜技术，对嵌入TiO介电基质中的等离子体金纳米颗粒（AuNP）进行了分析。制备方法是反应磁控溅射，随后在400和600°C下进行热退火处理。目的是评估纳米结构特征，并将其与AuNP的光学性质相关联，特别是局域表面等离子体共振（LSPR）行为。高角度环形暗场扫描透射电子显微镜结果表明，在沉积的Au-TiO薄膜中存在小尺寸的AuNP（量子尺寸范围），导致LSPR响应可忽略不计。400°C的真空热退火诱导形成了10-40nm范围内的中等尺寸纳米颗粒（NP），这导致了位于636nm处的明确定义的LSPR带的出现。电子断层扫描显示，大多数NP是小尺寸的，并嵌入TiO基质中，而较大的NP位于表面。600°C退火促进了双峰尺寸分布，其中中等尺寸的NP嵌入基质中，大尺寸的NP（高达100nm）出现在表面。由于散射与吸收比的增加，后者导致LSPR带变宽并红移至645nm。除了区分和量化表面和嵌入的NP外，电子断层扫描还提供了“热点”的识别。表面上单个或二聚体形式的NP的存在允许LSPR传感和表面增强光谱学（如表面增强拉曼散射）的吸附位点。
