Laser-assisted generation of gold nanoparticles and nanostructures in liquid and their plasmonic luminescence

Nanoparticles (NPs) and surface nanostructures (NS) are produced via laser ablation of a bulk gold target in liquid using second harmonics of 10 ps Nd:YAG laser (532 nm) with repetition rate of 50 kHz. The morphology and plasmon photoluminescence (PL) properties of obtained nanoscale objects are described. Transmission electron microscopy and field emission scanning electron microscopy are used for morphology characterization of NPs and NS, respectively. Plasmon PL of both gold NPs and NS is experimentally studied using the third harmonics of the Nd:YAG picosecond laser (355 nm) as a pump. The wavelength of intensity maximum of PL of Au NPs colloidal solution virtually coincides with the position of Au NPs plasmon absorption peak. Real-time excitation of both plasmon PL and Raman scattering of surrounding liquid by picosecond laser pulses in aqueous colloidal solution is also investigated. The efficient cross section of plasmon PL of Au NPs colloid is evaluated using Raman scattering of water as a comparative parameter. The results are in good agreement with values obtained in previous works. Plasmon PL from self-organized NS on the Au surface produced via laser ablation is observed for the first time. Its spectrum is compared to PL spectra of both aqueous colloidal solutions of NPs and of NPs deposited on a Si wafer. The obtained experimental data are discussed with reference to the band structure of bulk Au.