A nanohybrid xerogel (XDPN) was obtained from a tetraethyl orthosilicate (TEOS) condensation reaction in the presence of N,N'-bis(2-phosphonoethyl)-1,4,5,8-naphthalenediimide (DPN). Physical and chemical characterization of the materials revealed that the XDPN morphology is quite different from that of xerogel without DPN (X). Photochemical and photophysical studies of the hybrid material showed that XDPN is efficient in promoting the photosensitization of tryptophan radical formation, and the radical species are stabilized due to the presence of DPN aggregates in the material. Radical stabilization can also be observed for DPN in solution but only for concentrations in the millimolar range.