The aim is to employ contrast variation CV-SANS to investigate structure in novel systems used to generate metal-containing nanoparticles on organic solvents by UV irradiation. These systems contain photo-reactive surfactants (PRSs), being organometallic complexes which allow reduction of the metal through UV absorption via ligand-to-metal charge transfer (LMCT). Control over final particle size with these PRSs can be obtained by doping them into inert water-in-oil (w/o) microemulsions (no need for added inorganic salt reagents), overcoming many of the inherent limitations of standard microemulsion synthesis of nanoparticles. SANS is the only way to obtain this structural information.