Localized Surface Plasmon Resonance Sensor of Gold Nanoplates for Detection of Boric Acid Marlia Morsin 1,a , Muhamad Mat Salleh 1,b , Akrajas Ali Umar 1,c and Muhammad Yahaya 2,d 1 Institute of Microengineering and Nanoelectronics (IMEN), Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia. 2 School of Applied Physics, Faculty of Science and Techonolgy, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia. a marlia@uthm.edu.my, b mms@ukm.my, c akrajas@ukm.my, d myahya@ukm.my Keywords: Localized Surface Plasmon Resonance (LSPR), optical sensor, gold nanoplates, boric acid Abstract. Localized surface plasmon resonance (LSPR) peak wavelength of nanostructures metallic materials, such as gold and silver, is very sensitive to the dielectric environment of the materials; hence widely used as sensors to detect various types of chemicals. In this study, high - yield gold nanoplates ca. 63% have been grown on the quartz substrate using the seed - mediated growth method. The grown gold nanoplates exhibit variety of shapes such as triangular, hexagonal, truncated hexagonal and flat rod. The LSPR spectrum of Au nanoplates sample has two absorption bands; centring at 543 nm and 710 nm, which are associated with transverse SPR (t-SPR) and longitudinal SPR (l-SPR) respectively. The intensities and peaks position of these two bands were found to linearly change with the concentration of boric acid solutions. Introduction Surface plasmon is oscillations of free electron system of the metal surfaces with the electric field of light. The plasmonic is very sensitive to the dielectric surrounding medium [1], thus potential for sensing applications. The surface plasmon characteristics will be more unique when it is confined in nanoscale regime such as metallic nanoparticles, promising enhanced sensitivity to the change of surrounding medium due to strong dependency of plasmon on shape [2,3], further improve the performance and applications. Gold nanostructures have attracted researchers because of their unique surface plasmon resonance (SPR) properties and its potential applications in SERS, photoelectronic devices and biomedical applications [4]. As plasmon shape influence the SPR, synthesis of metallic nanostructures chemical method is actively demonstrated. Typical technique for synthesis nanogold is wet chemical method [3]. The gold (Au) nanoplates have been grown on the surface and SPR sensing properties was studied with the presence of boric acid. Boric acid is a non - permitted preservatives used in various food processing such as noodles, seafood and meat products especially by small scale producers. Thus, this sensor system can detect boric acid as low as 0.01 mM and this technique can be alternative method for in food quality control. Experiments Materials and Chemicals. The chemicals used for this synthesis were hydrogen tetrachloroaurate (HAuCl 4 .3H 2 O), trisodium citrate (C 6 H 5 Na 3 O 7 ), sodium tetraborohydride (NaBH 4 ), ascorbic acid, cethyltrimethyl ammonium boromide (CTAB) and poly (vinyl pyrrolidone) (PVP). These chemicals were purchased from Sigma-Aldrich except for trisodium citrate, sodium tetraborohydride and ascorbic acid which were obtained from Wako Pure Chemical Ltd. All these chemicals were used as Key Engineering Materials Vol. 605 (2014) pp 356-359 Online available since 2014/Apr/03 at www.scientific.net © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/KEM.605.356 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 103.31.34.2, Universiti Kebangsaan Malaysia (UKM), Bangi, Malaysia-25/09/14,04:09:08)