Modeling of the emission red-shift in organic-inorganic di-ureasil hybrids

The red-shift of the emission maximum intensity as the excitation energy decreases is modeled for organic/inorganic hybrids formed by a siliceous skeleton covalently grafted to oligopolyether chains by means of urea bridges (named di-ureasils). A new model of thermal relaxation within localized states based on the extended multiple trapping framework is derived and values for the energy gap and for the density of localized states are reported. The temporal dynamics that governs the emission is explicitly accounted assuming an effective energy independent lifetime.