Spectroscopy property of Ag nanoparticles.

Three silver nanoparticles of different size characterized by the UV-vis absorbance spectra and TEM images were prepared by citrate reduction and laser ablation with excitation of 532 and 248 nm. It is proved that all of them are effective SERS-active substrates, whereas, enhancement effect of silver colloids has not too much relation with the size and shape of the Ag nanoparticles. However, different photoluminescence spectra were observed from these three particles, indicating that the photoluminescence property of silver nanoparticles is dependent on the size. The spectra shift to higher energies with decreasing particle size. In addition, we also tentatively give the assignment of the luminescence bands.