Gopinath Ashwin, Boriskina Svetlana V, Reinhard Björn M, Dal Negro Luca
Department of Electrical and Computer Engineering & Photonics Center, Boston University, 8 Saint Mary's Street,Boston, MA 02446, USA.
Opt Express. 2009 Mar 2;17(5):3741-53. doi: 10.1364/oe.17.003741.
Deterministic Aperiodic (DA) arrays of gold (Au) nanoparticles are proposed as a novel approach for the engineering of reproducible surface enhanced Raman scattering (SERS) substrates. A set of DA and periodic arrays of cylindrical and triangular Au nanoparticles with diameters ranging between 50-110 nm and inter-particle separations between 25-100 nm were fabricated by e-beam lithography on quartz substrates. Using a molecular monolayer of pMA (p-mercaptoaniline) as a Raman reporter, we show that higher values of SERS enhancement factors can be achieved in DA structures compared to their periodic counterparts, and discuss the specific scaling rules of DA arrays with different morphologies. Electromagnetic field calculations based on the semi-analytical generalized Mie theory (GMT) fully support our findings and demonstrate the importance of morphology-dependent diffractive coupling (long-range interactions) for the engineering of the SERS response of DA arrays. Finally, we discuss optimization strategies based on the control of particles sizes and shapes, and we demonstrate that spatially-averaged SERS enhancement factors of the order of approximately 10(7) can be reproducibly obtained using DA arrays of Au nano-triangles. The ability to rigorously design lithographically fabricated DA arrays of metal nanoparticles enables the optimization and control of highly localized plasmonic fields for a variety of chip-scale devices, such as more reproducible SERS substrates, label-free bio-sensors and non-linear elements for nano-plasmonics.
提出将金（Au）纳米颗粒的确定性非周期（DA）阵列作为一种用于制备可重现表面增强拉曼散射（SERS）基底的新方法。通过电子束光刻技术在石英基底上制备了一组直径在50 - 110 nm之间、颗粒间距在25 - 100 nm之间的圆柱形和三角形Au纳米颗粒的DA阵列及周期性阵列。使用对巯基苯胺（pMA）的分子单层作为拉曼报告分子，我们表明与周期性结构相比，DA结构能够实现更高的SERS增强因子，并讨论了不同形态DA阵列的特定缩放规则。基于半解析广义米氏理论（GMT）的电磁场计算完全支持我们的发现，并证明了形态依赖的衍射耦合（长程相互作用）对于设计DA阵列的SERS响应的重要性。最后，我们讨论了基于控制颗粒尺寸和形状的优化策略，并证明使用金纳米三角形的DA阵列可以可重现地获得约10^7量级的空间平均SERS增强因子。精确设计光刻制备的金属纳米颗粒DA阵列的能力能够优化和控制用于各种芯片级器件的高度局域化等离子体场，例如更可重现的SERS基底、无标记生物传感器和用于纳米等离子体的非线性元件。
