Molecular Reaction Kinetics inside Channel Pores: Delayed Fluorescence of Naphthalene in Methanol

A one-dimensional, diffusion-controlled, reaction is followed in time by phosphorescence (monitoring reactant) and delayed fluorescence (moniloring product). The triplet (excited) naphthalene molecules move in a methanol solution, confined inside the cylindrical channels of a channel-pore polycarbonate membrane. The reaction product is a transient photodimer or excimer, giving delayed fluorescence. In large radius (1 pm) channel-pore membranes, the reaction kinetics are classical, with a heterogeneity exponent h=O. However, in the small radius (0.025 pm) channel-pore membranes the kinetics approach that of a onedimensional environment, h = l/2. For membranes with intermediate channel radius (0.1 pm), the reaction exhibits a “crossover” behavior which can be approximated via “fractal-like” kinetics.