Fluctuation in Surface Enhanced Raman Scattering intensity due to plasmon related heating effect Dinish U. S ∗1 , Chit Yaw Fu 1 , Kiang Wei Kho 2 , Praveen Thoniyot 1 , Ajay Agarwal 3 , Malini Olivo g 1,2,4 1 Bio Optical Imaging Group, Singapore Bioimaging Consortium, Agency for Science Technology and Research (A*STAR), 11 Biopolis Way, Singapore 138667 2 Division of Medical Science, National Cancer Centre Singapore, 11 Hospital Drive, Singapore 169610 3 Institute of Microelectronics, Agency for Science Technology and Research (A*STAR), Science Park Road, Singapore Science Park 2, Singapore 117685 4 Department of Pharmacy, National University of Singapore, 18 Science Drive 4, Singapore 117543 ABSTRACT Temporal changes in signal intensity of Surface Enhanced Raman Scattering (SERS) upon laser excitation is an interesting phenomenon in plasmonics. In-depth understanding of the phenomena is highly important especially when developing a SERS sensor based on the intensity variation of particular Raman peak/band. One of the main challenges in such a technique is the intensity reduction at a given location upon consecutive measurements. Previously, signal loss in SERS measurement was attributed to the electric-field induced roughness relaxations in the SERS active surface. In such cases, as the surface is smoothened out, signals are completely lost. In our observation, the reduction in the spectral intensity is irreversible but never completely lost and a major part of it can be attributed to the plasmon induced heating effect. Here, we experimentally demonstrate this effect by studying the SERS signal from four different Raman active molecules adsorbed onto substrates that contain uniform nano-roughened bi-metallic silver/gold coating. Possible mechanism that leads to irreversible signal loss is explained. Moreover, solutions for minimising such plasmonic heating when developing a biosensor are also discussed. Keywords: Surface Enhanced Raman Scattering, plasmonic heating, bi-metallic SERS substrates 1. INTRODUCTION About thirty years ago, Van Duyne et al. and Creighton’s et al. discovered the Surface-enhanced Raman scattering (SERS) when studying the Raman scattering of molecules adsorbed onto roughened metallic surfaces [1-2]. Since then many theories were proposed to explain the mechanism of this tremendous enhancement of the Raman scattering intensity [3-8]. Later, it was concluded that there are two contributing factors to enhancement, which are electromagnetic (EM) and chemical in origin. Light-induced localised surface plasmon resonance (LSPR) on the metallic surfaces is the determining factor for the EM enhancement while chemical enhancement is due to the charge transfer between the adsorbed molecule and metal surface. In most cases, EM enhancement predominates over chemical enhancement and its contribution from chemical enhancement may be of the order of 10 2 [9-11]. Moreover, unlike EM, chemical enhancement depends both on the excitation wavelength and the surface potential. EM enhancement as a result of LSPR will create the ‘hot’ electric field spots at nanoprotrusions of the nanoroughened metal surface. Consequently, molecules that are trapped within or situated in close proximity to these ‘hot spots’ would experience a strong excitation field and in turn result in enhanced Raman Corresponding authors: ∗ Dinish U. S; email: dinish@sbic.a-star.edu.sg g Malini Olivo; email: dmsmcd@nccs.com.sg Plasmonics: Metallic Nanostructures and Their Optical Properties VII, edited by Mark I. Stockman, Proc. of SPIE Vol. 7394, 73940T · © 2009 SPIE · CCC code: 0277-786X/09/$18 · doi: 10.1117/12.827234 Proc. of SPIE Vol. 7394 73940T-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 04/17/2015 Terms of Use: http://spiedl.org/terms