Sol-gel synthesis has been used to disperse an emissive chromophore within a porous TiO2 matrix, leading to xerogels and aerogels doped with tethered and unbound pyrenyl groups. Steady-state fluorescence was used to probe the interactions of neighboring pyrene groups within the gel matrix. Changes in the relative intensity of the monomer (I-1) emission peak as a function of chromophore concentration indicated a local interaction between included dyes for both tethered and unbound pyrene groups, likely through pi stacking. Partial matrix methylation or phenylation failed to produce a significant effect on the relative intensity of the I-1 signal in either the xerogel or the aerogel. Changes in the relative intensity of excimer emission with changes in matrix composition, however, do suggest that the presence of either phenyl or methyl groups within the TiO2 matrix impedes pi stacking between pairs of tethered pyrenyl groups. Compared with strong excimer emission in the xerogels containing pyrenyl groups at relatively high concentrations, excimer formation was inhibited in the corresponding aerogels, for which BET analysis indicated a broad pore size distribution in the mesoporous range, ca. 100 Angstrom.