Facile synthesis of concentrated gold nanoparticles with low size-distribution in water: temperature and pH controls
State Key Laboratory Base of Eco-Chemical Engineering, Lab of Colloids and Interfaces, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, China
Nanoscale Research Letters 2011, 6:440 doi:10.1186/1556-276X-6-440Published: 6 July 2011
The citrate reduction method for the synthesis of gold nanoparticles (GNPs) has known advantages but usually provides the products with low nanoparticle concentration and limits its application. Herein, we report a facile method to synthesize GNPs from concentrated chloroauric acid (2.5 mM) via adding sodium hydroxide and controlling the temperature. It was found that adding a proper amount of sodium hydroxide can produce uniform concentrated GNPs with low size distribution; otherwise, the largely distributed nanoparticles or instable colloids were obtained. The low reaction temperature is helpful to control the nanoparticle formation rate, and uniform GNPs can be obtained in presence of optimized NaOH concentrations. The pH values of the obtained uniform GNPs were found to be very near to neutral, and the pH influence on the particle size distribution may reveal the different formation mechanism of GNPs at high or low pH condition. Moreover, this modified synthesis method can save more than 90% energy in the heating step. Such environmental-friendly synthesis method for gold nanoparticles may have a great potential in large-scale manufacturing for commercial and industrial demand.