Highly efficient bifunctional mesoporous silica nanodevice coupling optical imaging with photodynamic therapy (PDT) was successfully prepared by using Rhodamine B as contrast agent and Verteporfin as photosensitizer. The precise localization and high dispersion of the contrast agent in the nanoparticles is the key point to get higher fluorescent quantum yields with respect to the fluorophore in solution. To achieve this information photoluminescence spectroscopy coupled with fluorescence lifetime measurement was used, due to its high sensitivity. The bifunctional nanodevice showed good performances both in terms of quantum yield of the anchored Rhodamine B (ΦRhB=0.55) and in the singlet oxygen delivery efficiency for PDT applications.