Tunable 3D Plasmonic Cavity Nanosensors for Surface-Enhanced Raman Spectroscopy with Sub-femtomolar Limit of Detection

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• 作者：Mohammadali Tabatabaei ; Mohamadreza Najiminaini ; Kieffer Davieau ; Bozena Kaminska ; Mahi R. Singh ; Jeffrey J. L. Carson ; Fran莽ois Lagugn茅-Labarthet
• 刊名：ACS Photonics
• 出版年：2015
• 出版时间：June 17, 2015
• 年：2015
• 卷：2
• 期：6
• 页码：752-759
• 全文大小：617K
• ISSN：2330-4022

文摘

Metallic nanohole arrays (NHAs) with a high hole density have emerged with potential applications for surface-enhanced Raman spectroscopy (SERS) including the detection of analytes at ultralow concentrations. However, these NHA structures generally yield weak localized surface plasmon resonance (LSPR), which is a prerequisite for SERS measurements. In this work, a compact three-dimensional (3D) tunable plasmonic cavity with extraordinary optical transmission properties serves as a molecular sensor with sub-femtomolar detection. The 3D nanosensor consists of a gold film containing an NHA with an underlying cavity and a gold nanocone array at the bottom of the cavity. These nanosensors provide remarkable surface plasmon polariton (SPP) and LSPR coupling, resulting in a significantly improved detection performance. The plasmonic tunability is evaluated both experimentally and theoretically. A SERS limit of detection of 10^鈥?6 M for 4-nitrothiophenol is obtained along with distribution mapping of the molecule on the 3D plasmonic nanosensor. This results in an improved SERS enhancement factor of 10⁷ obtained from a femtoliter plasmonic cavity volume. The tunability of these sensors can give rise to a potential opportunity for use in optical trapping while providing SERS sensing of a molecule of interest.