Two Photon Induced Luminescence of BSA Protected Gold Clusters

In this short letter, we have synthesized the BSA protected Au₂₅ nanoclusters and studied their two photon luminescence behavior. We demonstrate that BSA Au₂₅ nanoclusters can be used as a probe with two photon excitation capability. Our results show a quadratic relation between excitation power and emission intensity whereas with one photon excitation shows a linear dependence. The emission spectrum of BSA Au₂₅ nanoclusters with one photon and two photon excitation shows no appreciable change. Due to its long wavelength emission (650 nm) and two photon excitation, BSA Au₂₅ can be potentially used as a probe for deep tissue imaging.