Chapter 5 - Fluorescence, thermoluminescence, and photostimulated luminescence of nanoparticles

Abstract

This chapter reviews the fluorescence, thermoluminescence, and photostimulated luminescence of nanoparticles. The quantum-size and surface effects and their influence on the exciton oscillator strength, absorption, and fluorescence were also discussed. The photoluminescence excitation spectra and the excitation energy dependence of fluorescence of nanoparticles were illustrated. Photoluminescence excitation spectrum is better than absorption spectrum in the detection of splitted levels by quantum-size effect and has become a standard technique to obtain quantum dot absorption features, while the size selectively excited PL technique provides a good method to study the size dependence of the photoluminescence of nanoparticles in only one sample. The fluorescence process in nanoparticles is very complex and is not clear even at present, but it is agreed that surface states are involved and play an important role in the luminescence of nanoparticles. Thermoluminescence from semiconductor nanoparticles was observed and was discussed. The appearance of thermoluminescence of nanoparticles before any irradiation demonstrates the pre-existed trapped carders and the little change of the glow peak upon size indicates that the trap depth of surface states is not sensitive to particle size. Based on the thermoluminescence, a model proposed may explain the size dependence of the trapped luminescence from surface states of nanoparticles reasonably.