RESEARCH ARTICLE Copyright © 2013 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Nanoscience and Nanotechnology Vol. 13, 1–9, 2013 Stable Silver/Biopolymer Hybrid Plasmonic Nanostructures for High Performance Surface Enhanced Raman Scattering (SERS) Jaya Sundaram 1 ∗ , Bosoon Park 1 , and Yongkuk Kwon 2 1 Russell Research Center, United States Department of Agriculture, Agricultural Research Service, Russell Research Center, 950 College Station Road, Athens, GA, 30605, USA 2 Animal, Plant and Fisheries Quarantine and Inspection Agency, Anyang, South Korea Silver/biopolymer nanoparticles were prepared by adding 100 mg silver nitrate to 2% polyvinyl alco- hol solution and reduced the silver nitrate using 2% trisodium citrate for high performance Surface Enhanced Raman Scattering (SERS) substrates. Optical properties of nanoparticle were measured using UV/VIS spectroscopy and hyperspectral imaging microscopy. Nanoparticle morphology was analyzed using transmission electron microscopy. Substrate reproducibility and repeatability was checked by measuring SERS signals of trans-1,2-bis(4-pyridyl)ethylene (BPE) and Rhodamine 6G. Keywords: Surface Enhanced Raman Scattering, Silver Biopolymer Nanoparticle, Substrate, Optical Properties. 1. INTRODUCTION Raman spectroscopy gives inelastic light scattering to char- acterize various properties of analytes molecules. In prac- tice Raman scattering is very weak and it needs to be enhanced to get detectable spectral signals. To get enhanced Raman scattering, creation of patterned rough- ened surface substrates is needed. These substrates give significantly higher orders of scattering intensity. It provides spectral information furnished by molecular vibrations that are provided by both mid-infrared and near-infrared spectra. Molecular bonds directly affect the vibrational spectra and give specific fingerprints in Raman scattering to characterize analytes. 1–3 Plasmon is the elec- tron excitation of a metal conductor. If this excitation is restricted on the conductor metal surface it is called sur- face Plasmon. This surface Plasmon can either propagate on grating/rough surface or localize on spherical parti- cle surface. So, it is necessary to have surface rough- ness/grating or curvature for surface Plasmonic excitation under light. 4–8 SERS effect is characterized by two dif- ferent mechanisms such as excitation of surface Plasmon which creates local electromagnetic field enhancement and adsorption of component of analytes molecules on the sub- strate surface. Based on the mechanism of electromag- netic theory, SERS signal enhancement depends on many ∗ Author to whom correspondence should be addressed. factors such as excitation wavelength, optical properties of substrate and its surface morphology. Surface Plasmon on the roughened metal surface allows a part of the plasma energy applied through excitation wavelength to radiate and enhance the scattered signals; whereas smooth sur- faces loose the excitation energy as heat and do not pro- vide signal enhancement. 8–12 There are several methods have been employed in fabrication of metal substrates with features of surface roughness to get maximum signal enhancement such as electrochemical oxidation reduction cycles, chemical etch- ing, and metal film deposition. 13–16 All the methods has their own advantages and disadvantages to fullfill all the requirements of an substrate properties such as optical properties, reproducibility, surface morphology, stability and signal enhancement factors etc. 17 Metals such as sil- ver, gold and copper have been identified as suitable for SERS substrate; however, silver has been identified as universal substrates metal due to the following reasons. Silver metal has broad plasmon resonance in visible, near- infrared region and higher stability than other metals. Also it was found though many experiments that the most intense Raman scattered signals were obtained using silver metal. 17–20 Several forms of silver nano structures are being used in SERS research such as silver nanorod, dendrite, nanowire, silver colloidal nanoparticle etc., fabricated through vac- uum evaporation, lithography, laser ablation, electrode J. Nanosci. Nanotechnol. 2013, Vol. 13, No. xx 1533-4880/2013/13/001/009 doi:10.1166/jnn.2013.7737 1