Synthesis of copper nanoparticles mediated by photogenerated free radicals: catalytic role of chloride anions.

The photodecomposition of ketones by the Norrish Type I reaction, leading to the efficient release of reducing ketyl or alpha-amino alkyl radicals, provides a facile route for the synthesis of copper nanoparticles (CuNP) in both aqueous and organic solvents. The role of different counterions (especially halides) and surfactants has been used to 'tune' the morphology and size of the nanostructures formed. In aqueous solutions chloride ions catalyze the disproportionation that mediates the Cu(I) --> Cu(0) --> CuNP conversion. This article concentrates on spherical nanoparticles and offers some insights into the routes to other nanostructures.