The Impacts of pH and Tryptophan Concentration on Controllable

Synthesis of Gold Nanoparticles

Leilei Dai1, Fang Cai2, Hao Lv1, Jinsheng Sun1*, Jie He1,Xijia Cao1

1 School of Chemical Engineering and Technology, Tianjin University, No. 92 Wei Jin

Road, Tianjin 300072, P. R. China

2 Wuhan Petrochemical Engineering Co.,Ltd, Special No.1 Chang Qing Road, Wuhan

430082, P. R. China
*Corresponding author. Tel. /fax: +86 22 27891755
E-mail addresses: jssun2006@vip.163.com
This article described an easy and efficient method to synthetize gold nanoparticles (GNPs) using tryptophan as reducing/stabling agent in aqueous solution. The important reaction parameters including pH and tryptophan concentration were investigated to examine their influences on the reaction kinetics and the size/shape of the resultant GNPs. Spectrophotometric, kinetic, and transmission electron microscopic (TEM) analyses for the harvested gold GNPs were carried out. Experimental researches find that strong acid or alkaline conditions ( â?¤p1H.5 or pHâ?¥9.5) are unfavorable for the reaction process. The appropriate reaction pH falls between 2.5 and 6.0, with 4.5 the optimal pH condition for the formation of gold nanospheres with relatively high monodispersity. Additionally, tryptophan concentration also has effects on size and shape of the formed nanoparticles to a certain extent. With the increase of tryptophan concentration, the reaction rate speeds up and thus results in smaller and higher spherical nanoparticles.

Keywords: Nanoparticles; Synthesis; Kinetics