Preparation, Structural, Electrochemical and Photocatalytic Studies of Cadmium Sulfide Quantum Dots

We report the preparation, structural, electrochemical and photocatalytic studies of monodispersed cadmium sulphide quantum dots from didecylaminyl dithiocarbamate and 4-chloro-3-(trifluoromethyl) anilinyl dithiocarbamate cadmium(II) complexes. Powder X-ray diffraction pattern confirms hexagonal crystalline phases for the as-preapred CdS quantum dots irrespective of the precursor used with particle size of 3.39-5.51 nm. Optical absorption band edges of 515 nm were observed for the cadmium sulfide quantum dots with energy band gaps estimated from the Tauc plots of 1.97 eV for OLM-CdS1 prepared from Cd(II) didecylaminyl dithiocarbamate and 1.92 eV for OLM-CdS2 prepared from Cd(II) 4-chloro-3-(trifluoromethyl) anilinyl dithiocarbamate. These energy band gaps are blue shifted with respect to the bulk cadmium sulphide. The calculated electrochemical band gap of 2.34 V and 3.30 V are higher than band gap energy. The as-prepared CdS quantum dots were used as photocatalysts for the photocatalytic decomposition of methylene blue (MB) with efficiency of 61 % and 55 %.