Continuous-wave laser-induced welding and giant photoluminescence enhancement of Au nanospheres

Photoluminescence (PL) of Au nanoparticles is appealing for various biological applications, owing to their unique advantages. However, widespread applications are still limited by their extremely low quantum yield. Here, we report on the giant PL enhancement of aggregated Au nanospheres by continuous-wave (CW) laser irradiation. Our studies show that the laser-induced PL enhancement is influenced by the wavelength and power density of irradiation laser, as well as the size of Au nanospheres. The averaged intensity of Au nanospheres after irradiation by 405 nm CW laser at power density of 6 MW/cm2 is 75 times that of the as-prepared sample, where the highest enhancement of 150 folds is obtained. The giant PL enhancement is attributed to laser-induced photothermal welding and reshaping of adjacent Au nanospheres, which will dramatically enhance the incidence light field in the crevices around the welding areas by surface plasmon resonance. These studies not only declare that Au nanospheres are expected to find many new applications in PL-based biosensing and bioiamging, but also suggest that CW laser can be used as a versatile tool to weld and reshape the Au nanospheres in order to build up functionalized electronic and optoelectronic devices.