PHOTOLUMINESCENCE OF COLLOIDAL CADMIUM-SULFIDE IN THE PRESENCE OF ANILINE - STUDY OF CDS-SENSITIZED PHOTOCATALYTIC REACTION

Aniline quenches the photoluminescence of colloidal cadmium sulphide and suppresses its photoanodic dissolution. The addition of 0.025 mM of aniline at pH 3.7 and 0.15 mM of aniline at pH 10.6 to a colloidal solution of CdS reduces its emission intensity by about 50%. The degree of quenching depends largely on the extent of adsorption of the substrate on the surface of the colloid. The addition of aniline prior to the precipitation of CdS produces a surface-modified catalyst with different electronic properties from bulk CdS. The absorption band edge and emission band of the catalyst are gradually blue shifted with increasing aniline concentration. An aniline concentration of 0.015 M moves the onset of absorption and the luminescence peak to higher energy (by 0.12 eV and 0.06 eV respectively). The CdS-photosensitized reaction of aniline results in the formation of azobenzene with a quantum efficiency of 0.15. A mechanism for this reaction is proposed.