Facile fabrication of branched gold nanoparticles by reductive hydroxyphenol derivatives.

In nature, polyphenol is one of the most important chemicals in many reductive biological reactions widely found in plants and animals. In this study, we demonstrated that hydroxyphenol compounds and their derivatives could be used as versatile reducing agents for facile one-pot synthesis of gold nanoparticles with diverse morphological characters by reducing precursor Au(III) ions into a gold crystal structure via a biphasic kinetically controlled reduction process. We found that the biphasic reduction of hydroxyphenols generated single-crystalline branched gold nanoparticles having high-index facets on their surface. The kinetically controlled self-conversion of hydroxyphenols to quinones was mainly responsible for the generation of morphologically different branches on the gold nanoparticles. Different hydroxyphenol derivatives with additional functional groups on the aromatic ring could produce totally different nanostructures such as nanoprisms, polygonal nanoparticles, and nanofractals possibly by inhibiting the self-conversion or by inducing self-polymerization. In addition, polymeric hydroxyphenol derivatives generated stably polymer-coated spherical gold nanoparticles with controlled size, usefully applicable for biomedical applications.