Ecofriendly Synthesis of Anisotropic Gold Nanoparticles: A Potential Candidate of SERS Studies

Ecofriendly synthesis of nanoparticles has been inspiring to nanotechnologists especially for biomedical applications. Moreover, anisotropic particle synthesis is an attractive option due to decreased symmetry of such particles often leads to new and unusual chemical and physical behaviour. This paper reports a single-step room-temperature synthesis of gold nanotriangles using a cheap bioresource of reducing and stabilizing agent Piper betle leaf extract. On treating aqueous chloroauric acid solution with Piper betle leaf extract, after 12 hr, complete reduction of the chloroaurate ions was observed leading to the formation of flat and single crystalline gold nanotriangles. These gold nanotriangles can be exploited in photonics, optical coating, optoelectronics, magnetism, catalysis, chemical sensing, and so forth, and are a potential candidate of SERS studies. 1. Introduction The synthesis of metal and semiconductor nanoparticles has innumerable opportunities of research due to their present and future applications in biosensing [1], chemical sensing [2], recording media [3], optoelectronics [4], and catalysis [5]. Masatake has reported [6] gold as a novel catalyst in the 21st century: it’s preparation, working mechanism, and application as the catalyst in CO oxidation. The majority of earlier research has focused on isotropic, that is, spherical particles. However, anisotropic particles are particularly interesting because the decreased symmetry of such particles often leads to new and unusual chemical and physical properties [7]. In this context, ecofriendly biosynthesis protocols are better roadmap to avoid adverse effects of nanomaterials especially in medical applications. Moreover, use of plant extracts as a reducing and capping agent for the synthesis of nanoparticles could be advantageous over other environmentally benign biological processes by eliminating the elaborate process of maintaining cell cultures. It can also be suitably scaled up for the large-scale synthesis of nanoparticles. The biosynthesis of platinum nanoparticles using Diospyros kaki leaf extract [8], silver nanoparticles using leaf extracts [9], silver and gold nanoparticles using phyllanthin [10], Clove extract [11], and within live Alfalfa plants in solid media [12] has been demonstrated. In recent studies, we have reported on the synthesis of gold nanoparticles by the reduction of aqueous ions using Cymbopogon flexuosus [13], Tamarindus indica [2], Emblica officinalis [14], Terminalia catappa [15], Murraya koenigii and Citrus limonum leaf extracts [16]. In the case of