The effect of local environment on photoluminescence: A time-dependentdensity functional theory study of silanone groups on the surfaceof silica nanostructures

摘要

The optical absorption spectrum and lowest photoluminescence (PL) signal for silanone terminatedsilica nanostructures are studied using time-dependent density functional theory calculations on arange of realistic low energy silica nanocluster models. We show that the broad experimentalabsorption spectrum for silanone centers [V. A. Radtsig and I. M. Senchenya Russ. Chem. Bull. 45,1849 (1996)] is most likely the result of a synergetic combination of inhomogeneous broadening,thermal broadening and the small energy differences between different excitations. We furtherdemonstrate that upon relaxation of the excited state the excited electron and hole localize on onlyone silanone center, and that there is a clear and distinct link between the local environment of asilanone center and its absorption and PL spectra. Finally, we provide strong evidence that thesilanone center does not have a double bond between the constituent silicon and oxygen atoms butrather can be probably more aptly described as the =Si~+-O~- charge-transfer species.