SERS of Individual Nanoparticles on a Mirror: Size Does Matter, but so Does Shape

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• 作者：Felix Benz ; Rohit Chikkaraddy ; Andrew Salmon ; Hamid Ohadi ; Bart de Nijs ; Jan Mertens ; Cloudy Carnegie ; Richard W. Bowman ; Jeremy J. Baumberg
• 刊名：The Journal of Physical Chemistry Letters
• 出版年：2016
• 出版时间：June 16, 2016
• 年：2016
• 卷：7
• 期：12
• 页码：2264-2269
• 全文大小：539K
• 年卷期：0
• ISSN：1948-7185

文摘

Coupling noble metal nanoparticles by a 1 nm gap to an underlying gold mirror confines light to extremely small volumes, useful for sensing on the nanoscale. Individually measuring 10 000 of such gold nanoparticles of increasing size dramatically shows the different scaling of their optical scattering (far-field) and surface-enhanced Raman emission (SERS, near-field). Linear red-shifts of the coupled plasmon modes are seen with increasing size, matching theory. The total SERS from the few hundred molecules under each nanoparticle dramatically increases with increasing size. This scaling shows that maximum SERS emission is always produced from the largest nanoparticles, irrespective of tuning to any plasmonic resonances. Changes of particle facet with nanoparticle size result in vastly weaker scaling of the near-field SERS, without much modifying the far-field, and allows simple approaches for optimizing practical sensing.