Optical and photochemical properties of sodium dodecylbenzenesulfonate (DBS)-capped TiO2 nanoparticles dispersed in nonaqueous solvents

TiO2 nanoparticles capped with sodium dodecylbenzenesulfonate (DBS) have been synthesized so that they can be dispersed in many organic and nonaqueous solvents. It has been found that DBS-capped TiO2 nanoparticles have a significant red shift of the optical absorption band edge and clear photoluminescence at room temperature in contrast to that of bare TiO2 nanoparticles. The results obtained indicate that the surface structure, that is, the capping group and the defect states, plays an important role in the electronic states of TiO2 nanoparticles. The recombination dynamics of the photoexcited charge carriers (electron and hole pairs) of DBS-capped TiO2 as studied by picosecond transient absorption spectroscopy is found to be much slower as compared to that of bare TiO2 nanoparticles as reported earlier.