Investigation of silica particle growth by incorporation of a pyrene fluorescent probe

The growth of silica particles synthesized by the Stöber method was investigated by the co-condensation of pyrene sulfonyl chloride (PySCl) coupled to (3-aminopropyl)triethoxysilane (APTES). Growth by monomer addition could be distinguished from growth by aggregation based on the intensity of the pyrene excimer emission of the resulting particles. The influence of the base concentration, water/ethanol ratio, solvent, temperature, and type of silica precursor was studied. At high hydrolysis rates, the growth occurred primarily by aggregation, whereas growth by monomer addition was predominant at low hydrolysis rates. The results were confirmed by evaluating the accessibility of the co-condensed pyrene moieties and by determining the porosity of the particles.