We report the formation of monomeric and J-aggregated 1,1 ' ,3,3 ' -tetraethyl-5,5 ' ,6,6 ' -tetrachlorobenzimidazolocarbocyanine (referred to as TTBC) encapsulated within an aluminosilicate mesostructure, specifically MCM-41, under different pH conditions. It was necessary to stabilize the synthesized MCM-41 through use of a silylation reagent, (aminopropyl)triethoxysilane, which cross-links oxygen on the surface (thus thickening the walls of the mesoporous material) and functionalizes the interface for proper guest-host interaction. XRD, UV-vis absorption and fluorescence measurements are used as spectroscopic tools to characterize the various products. The composite consisting of J-aggregated TTBC and the aluminosilicate represents a new fluorescent nanomaterial that possesses the properties of the aggregate, yet avoids the essentially unfettered topography and physical length accompanying the formation of an aggregate in solution or adsorbed onto an interface.