Synthesis of Water-Soluble, Thiolate-Protected Gold Nanoparticles Uniform in Size.

By a modification of the method of Brust et al., water-soluble, thiolate-protected gold nanoparticles that are uniform in size were synthesized with no requirement for purification. The modification of the method was equilibration in the first step, which proved crucial for achieving size homogeneity. The thiol-to-gold ratio controlled the size of the particles, and the choice of thiol controlled the reactivity of the particles toward thiol exchange.