Photophysical and photocatalytic properties of histidine-stabilized CdS quantum dots in the presence of indole

The fluorescence band of the histidine-stabilized CdS quantum dots was found to be blue-shifted as well as enhanced in intensity in the presence of indole. Irradiation of the reaction mixture containing CdS and indole using visible light resulted in the formation of indigo and isatin as the products of the photocatalytic reaction. The presence of adenine was found to enhance the photocatalytic activity of the CdS quantum dots. Time-resolved fluorescence measurements indicated that adenine enhanced the lifetime of the photogenerated electron–hole pair thereby allowing more indole molecules to undergo reaction with the hole.