Single bovine serum albumin molecule can hold plural blue-emissive gold nanoclusters: A quantitative study with two-photon excitation

Abstract Two-photon luminescence properties of gold nanoclusters (Au 8 NCs) encapsulated in bovine serum albumin (BSA) were investigated. A new synthesis protocol is reported to control the number of Au 8 clusters in one BSA. Both one- and two-photon excitation of BSA with multiple Au 8 NCs gave an identical blue luminescence. The two-photon absorption (TPA) cross-section value for BSA with one Au 8 NCs was obtained to be 190 GM (Goeppert-Mayer) and 540 GM for BSA with three Au 8 NCs, at 740 nm excitation wavelength. This study shows that BSA with multiple Au 8 NCs may be used as a biocompatible luminescence probe for two-photon in-vivo imaging.