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 photoluminesce nce (PL) intensity of the semiconductor particle relative to its value in p ure ethanol solvent. The enhancement is in the order 1,4-dimethyl-N > 1-chl oro-N greater than or equal to N greater than or equal to 1-fluoro-N greate r than or equal to 1-methyl-N greater than or equal to 1-bromo-N and quench ing is in the order 1-nitro-N > 2-carboxy-N. This order is understandable b ased on the electron-donating or electron-accepting abilities of the indivi dual 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. 1 0(3) M-1.