Optical Properties of Silver and Gold Tetrahedral Nanopyramid Arrays Prepared by Nanosphere Lithography
Optical Properties of Silver and Gold Tetrahedral Nanopyramid Arrays Prepared by Nanosphere Lithography
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DOI：
10.1021/jp405125c
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发表时间：
2013-07-18
影响因子：
3.7
通讯作者：
Lagugne-Labarthet, Francois
中科院分区：
文献类型：
--
作者：
Tabatabaei, Mohammadali;Sangar, Alexandre;Lagugne-Labarthet, Francois
在ITO/玻璃表面制备了由银和金制成的四面体纳米金字塔。我们的方案是基于纳米球光刻（NSL）与沉积较厚的金属层。在去除NSL工艺中使用的微球后，形成了高度约为350- 400nm的金属四面体纳米结构阵列。报道的程序避免使用任何稳定表面活性剂分子，这些分子通常是将单个颗粒分离到表面上所必需的。我们在此重点研究这些等离子体表面的光学和物理性质，使用近场光谱结合电场的时域有限差分（FDTD）建模。时域有限差分法表明，局部表面等离子体共振被限制在平行于碰撞激发激光偏振方向的两个面向金字塔的边缘所形成的平面内。与通常的纳米三角形阵列相反，两个相邻金字塔边缘之间的可变间隙显示出更宽的局部表面等离子体和更大的比表面。通过在纳米锥体表面涂覆光敏偶氮聚合物薄膜，研究了等离子体表面电场的局部增强。辐照后，原子力显微镜可以观察到表面形貌的变形，这表明这些三维纳米金字塔具有近场增强的潜力。最后一个特征被表面增强拉曼散射测量清楚地证实了4-亚硝基苯酚分子沉积在金字塔平台上。这种三维纳米结构在等离子体和表面光谱学方面的潜力因此得到了清楚的证明。
Tetrahedral nanopyramids made of silver and gold over ITO/glass surfaces are fabricated. Our protocol is based on nanosphere lithography (NSL) with the deposition of thicker metal layers. After removing the microspheres used in the NSL process, an array of metallic tetrahedral nanostructures of similar to 350-400 nm height is formed. The reported procedure avoids the use of any stabilizing surfactant molecules that are generally necessary to segregate the individual particles onto surfaces. We focus here on the optical and the physical properties of these plasmonic surfaces using near-field spectroscopy in conjunction with finite difference time domain (FDTD) modeling of the electric field. Remarkably, FDTD shows that the localized surface plasmon resonance is confined in the plane formed by the edges of two facing pyramids that is parallel to the polarization of the impinging excitation laser. The variable gap between the edges of two adjacent pyramids shows a broader localized surface plasmon and a larger specific surface as opposed to the usual nanotriangle array. Localized enhancement of the electric field is experimentally investigated by coating the plasmonic surface with a thin film of photosensitive azopolymer onto the surface of the nanopyramids. Upon irradiation, the deformation of the surface topography is visualized by atomic force microscopy and suggests the potentiality of these 3D nanopyramids for near-field enhancement. This last feature is clearly confirmed by surface-enhanced Raman scattering measurement with 4-nitrothiophenol molecules deposited on the pyramid platforms. The potentiality of such 3D nanostructures in plasmonics and surface spectroscopy is thus clearly demonstrated.