Aggregation of Gold Nanoparticles Induced by Halide Salts

Metal nanoparticles exhibit unique optical properties due to their interaction with electromagnetic fields, known as Surface Plasmon Resonance (SPR). This is dependent on the environment as well as their size, shape and aggregation state [1]. Gold nanoparticles (Au NPs) have been proposed for applications in a wide range of fields including sensing, medicine, photonics and many others. Their SPR can be tuned by changing their shape into e.g. nanorods, nanoplates or nanostars. Alternatively, SPR can be tuned by controlling their aggregation. In this study, we present the controlled aggregation of Au NP prepared by laser ablation in liquids (LAL) by addition of halide salts. We observe that adding a halide salts induces the formation of a new SPR band that is significantly red-shifted from the initial one (see figure 1), due to the formation of Au NP aggregates, as observed by electron microscopies, and supported by Finite-difference time-domain simulations. We investigated a broad range of factors influencing the kinetics and the extent of the aggregation process, such as initial NP concentration, halide concentration, temperature, and presence of oxygen. The surface composition of such aggregates will be investigated.