Caging Effect of Unbound Graphene Oxide Nanosheets during Gold Colloid Fragmentation under Electrostatic Repulsion

The laser-induced fragmentation of colloidal nanoparticles represents a well-established method to obtain surfactant-free nanoclusters in liquids. While the typical fragmentation mechanisms for nanosecond and picosecond laser excitation have been linked to photothermal heating–melting evaporation and phase explosion processes (depending on the applied laser energy density), the subsequent growth processes on longer nano- to microsecond time scales and beyond remain mostly elusive. In the past, first insights into the role of electrostatic interactions between the formed nanoclusters mediated by inorganic salts have been highlighted. In this study, we intend to extend this concept toward the role of supporting particles with a high surface area such as graphene oxide to augment or quench growth processes. Compared with the laser fragmentation of gold nanoparticles in the absence of GO, larger final particle sizes of the formed clusters were observed when GO was present. Given the electrostatic repulsion between GO and Au clusters at a given pH value, the GO sheets take part in the fragmentation process by electrostatically confining the fragmented clusters that form during the laser-induced phase explosion of the initial gold nanoparticles. Consequently, larger final cluster sizes were observed in the presence of GO under electrostatically repulsive conditions.