Exciton spectra of SnO2 nanocrystals with surficial dipole layer

Experimental results of absorption, luminescence and excitation spectra in both bare and coated SnO2 nanocrystals are given. It is found that when the SnO2 nanocrystals are coated by a layer of organic moleculae, the absorption edge shifts to the longer wavelength direction as the particle size decreases, which is inconsistent with that of bare SnO2 nanocrystals. It is demonstrated that the size and surface situations of nanocrystals have great influence on their spectroscopic properties. The experimental data are discussed in terms of the quantum confinement effects and dielectric confinement effects.