Electric-Field Enhanced Molecule Detection in Suspension on Assembled Plasmonic Arrays by Raman Spectroscopy

One of the greatest challenges in surface enhanced Raman scattering (SERS) sensing is to detect biochemicals directly from suspension with ultrasensitivity. In this work, we employed strategically designed longitudinal nanocapsule structures with uniformly surface distributed Ag nanoparticles (Ag NPs) to dually focus and enhance SERS sensitivity of biochemicals in suspension assisted with electric fields. By tuning the reaction conditions, Ag NPs were synthesized and uniformly grown with optimized sizes and junctions on the surface of nanocapsules for well reproducible detection. The Ag NPs can further concentrate molecules from suspension due to induced electrokinetic effects in electric fields. As a result, the signals of Nile blue molecules can be enhanced by 34.4±3.1% at optimal alternating current (AC) frequencies and voltages compared to that without electric fields. This work demonstrates the dual roles of a new type of plasmonic NPs for molecule concentration and detection, which could inspire new Raman sensing devices for applications in microfluidics.