Continuous synthesis of gold nanoparticles in a microreactor.

A continuous flow microreactor was used for the synthesis of gold nanoparticles (5 to 50 nm) directly from a gold salt (HAuCl(4)) and a reducing agent (ascorbic acid). Experimental parameters were optimized to obtain narrow size distributions, which were at average two times narrower than those obtained in a conventional synthesis. Additionally, two approaches, i.e., elevation of pH during reaction and hydrophobization of internal reactor surfaces were tested to suppress reactor fouling.