Visible photoluminescence of gold nanoparticles prepared by sputter deposition technique in a room-temperature ionic liquid

Photoluminescence (PL) is observed for gold nanoparticles prepared by using sputter deposition technique and stably dispersed in a room-temperature ionic liquid of 1-butyl-3-methylimidazolium hexafluorophosphate. PL spectrum in the visible region depends on the excitation wavelength; the spectrum is shifted to longer wavelengths, as the excitation wavelength becomes longer, which probably comes from the size distribution of nanoparticles. Decay profiles as well as quantum yields of PL are measured at different excitation wavelengths. PL intensity shows a multiexponential decay, and the average lifetime, which depends on the excitation wavelength, is shorter than 3 ns.