A water-insoluble porphyrin derivative was studied in Triton X-100 micelles by steady-state spectroscopy and picosecond photolysis. The porphyrin in micelles formed J aggregates, and, consequently, the excited state lifetime of such a porphyrin was very short. After the addition of colloidal SiO2, the B-band absorption blue-shifted, forming a broad absorption peak. This peak can be ascribed to the monomer-dominated absorption of porphyrin. The photolysis experiment showed that the dynamic curve of the porphyrin with SiO2 exhibited a rapid recovery plus an offset resulting from the S-1 state absorption. The long lifetime part constituted about half of the total absorption. Such a long-lifetime component could be ascribed to the absorption of monomeric porphyrin. The fluorescence near-field scanning optical microscopy showed that the porphyrin in the presence of SiO2 exhibited stronger fluorescence images compared with that in the absence of SiO2, though the topography images of the these samples were similar. The monomeric dispersion of porphyrin in SiO2 solution may be due to its inset in the fragmented bilayers on the surface of the SiO2 particles, assisted by the hydrogen bond between the amino group and the ionized silanol Of SiO2. The prolonged excited lifetime can be greatly beneficial to the application of porphyrin in heterogeneous photosensitization or photocatalysis.