Influence of gold nanoparticles on the up-conversion fluorescence in Sm³⁺

Fluorescence spectra of gold colloid containing samarium ions have been recorded and analyzed at room temperature. For gold colloids, two fluorescence emission peaks are observed at 443 nm and 745 nm, respectively when the corresponding excitation wavelength is fixed at 595 nm. When amount of Sm ³⁺ are added to gold colloids, the up-conversion emission peak at 443 nm increased greatly. Furthermore, increasing the gold colloids addition leads to the up-conversion luminescent intensity increases in the early stage and then decreased. We believe the enhanced up-conversion are due to the energy transferred from the fluorescence from gold nanoparticles to Sm³⁺, and make the excited state absorption (ESA) in Sm³⁺ takes place.