Solvent effect on light-emitting property of Si nanocrystals

Using ultrasonic vibrations of as-made porous silicon in water, benzene, chloroform, and toluene solvent, four groups of suspensions of Si nanocrystals are prepared for exploring the influence of solvents on the light-emitting properties of Si nanocrystals. Photoluminescence (PL) spectral examinations show that the strongest PL spectrum appears in the toluene suspension with the smallest HOMO/LUMO gap. This result is explained on the basis of the frontier orbital theory and toluene chemisorption model. In addition, shift of the PL peak was also observed in different suspensions. This behavior is considered to be due to the influence of the solvent polarity.