Green Synthesis Of Gold Nanoparticles Using Camellia Sinensis And Kinetics Of The Reaction

Department of Chemistry, Gauhati University, Guwahati 781014, Assam, India

Adv. Mater. Lett., 2012, 'ICNANO 2011', 3 (6), pp 481-486

DOI: 10.5185/amlett.2012.icnano.103

Publication Date (Web): Sep 23, 2012

Copyright © IAAM-VBRI Press

E-mail: sontarak.boruah@gmail.com

Abstract

In this paper we report the green synthesis of gold nanoparticles (AuNPs) by using a simple, faster, low cost, eco-friendly technique. The green synthesis of AuNPs was done by using fresh young leaves and leaf buds of tea (Camellia Sinensis). Reduction of HAuCl₄ by polyphenols present in young leaves and leaf buds of tea extract at room temperature provides AuNPs (Au³⁺→Au⁰).The UV-Visible absorption spectrum of AuNPs in tea extract shows two bands at around 534 and 752 nm, which results from transverse and longitudinal surface plasmon resonance (SPR) respectively. In fluorescence spectroscopy study, AuNPs in tea extract shows fluorescence emission at 450 and 705 nm when excited at 350 nm. The kinetics of the reaction rate (Au³⁺ →Au⁰) with respect to time was studied with the help of UV-Visible and fluorescence spectroscopy. The reaction rate evaluated with the help of UV-Visible and fluorescence spectroscopy was found to be almost similar in results. The kinetics of the reaction also suggests that the reaction was fast and completed in 28 minutes. The amount of tea extract determines the core size of the AuNPs. The core size of the AuNPs decreases as the amount of tea extract increases and it causes the blue-shift of SPR band. The physical properties, particle size and morphology of AuNPs were characterized using X-ray diffractometer (XRD), field emission scanning electron microscope (FESEM) and high resolution-transmission electron microscopy (HR-TEM) techniques. The AuNPs size in the range ~2.94-45.58 nm with an average of 13.14 nm.

Keywords

Gold nanoparticles, Camellia Sinensis, green synthesis, surface plasmon.