[Ultraviolet and blue-violet photoluminescence of gold nanoparticles]

Suspended gold nanoparticles (size range 20-30 nm) have been synthesized via electrochemical method. The emission spectra of gold colloidal nanoparticles were studied at room temperature. Fluorescence occurs at ultraviolet and blue-violet wavelengths. Two emission peaks were observed at 377 nm and 459 nm, respectively, when the corresponding excitation wavelength was at 220 nm. The emission peak at 377 nm increases with increasing particle density or excitation intensity, whereas the emission peak at 459 nm decreases with decreasing excitation intensity or increasing the particle density, and disappears below the threshold. With increasing the slit width, the intensity difference between these two emission peaks decreases and the ratio approaches 1. All these observed results are in agreement with the theory of self-organized random micro-cavity. It is indicated that the fluorescence emissions in ultraviolet and blue-violet wavelength regions are induced by the multiple scattering in a disordered gold nanoparticles system. And these photoluminescence features suggest the possible future applications in the areas of optical data storage and full color display.