Influence of the naphthalene derivative on the luminescence properties of CdS particles prepared by the sol-gel method

Adsorption from an ethanol solution of naphthalene (N) derivatives onto the surface of CdS particles encapsulated into silica glasses prepared by the sol-gel method quenches or enhances the yellow-green and red photoluminescence (PL) intensity of the semiconductor particle relative to its value in pure ethanol solvent. The enhancement is in the order 1,4-dimethyl-N > 1-chloro-N greater than or equal to N greater than or equal to 1-fluoro-N greater than or equal to 1-methyl-N greater than or equal to 1-bromo-N and quenching is in the order 1-nitro-N > 2-carboxy-N. This order is understandable based on the electron-donating or electron-accepting abilities of the individual naphthalene derivatives. The changes in the PL intensity depend on the concentration and give good fits to the Langmuir adsorption isotherm model, yielding equilibrium constants for adduct formation on the order of ca. 10(3) M-1.