title: Influence of electric field on SERS: frequency effects, intensity changes, and susceptible bonds.
abstract: The fundamental mechanism proposed to explain surface-enhanced Raman scattering (SERS) relies on electromagnetic field enhancement at optical frequencies. In this work, we demonstrate the use of microfabricated, silver nanotextured electrode pairs to study, in situ, the influence of low frequency (5 mHz to 1 kHz) oscillating electric fields on the SERS spectra of thiophenol. This applied electric field is shown to affect SERS peak intensities and influence specific vibrational modes of the analyte. The applied electric field perturbs the polar analyte, thereby altering the scattering cross section. Peaks related to the sulfurous bond which binds the molecule to the silver nanotexture exhibit strong and distinguishable responses to the applied field, due to varying bending and stretching mechanics. Density functional theory simulations are used to qualitatively verify the experimental observations. Our experimental and simulation results demonstrate that the SERS spectral changes relate to electric field induced molecular reorientation, with dependence on applied field strength and frequency. This demonstration creates new opportunities for external dynamic tuning and multivariate control of SERS measurements.
authors.affiliation: Microplatforms Research Group, School of Electrical and Computer Engineering, RMIT University, Melbourne, Australia. sharath.sriram@gmail.com
authors.forename: Sharath
authors.initials: S
authors.lastname: Sriram
authors.forename: Madhu
authors.initials: M
authors.lastname: Bhaskaran
authors.forename: Shijian
authors.initials: S
authors.lastname: Chen
authors.forename: Sasani
authors.initials: S
authors.lastname: Jayawardhana
authors.forename: Paul R
authors.initials: PR
authors.lastname: Stoddart
authors.forename: Jefferson Z
authors.initials: JZ
authors.lastname: Liu
authors.forename: Nikhil V
authors.initials: NV
authors.lastname: Medhekar
authors.forename: Kourosh
authors.initials: K
authors.lastname: Kalantar-Zadeh
authors.forename: Arnan
authors.initials: A
authors.lastname: Mitchell