Synthesis of CdS particles: CdS particles were prepared by a simple solvothermal method. Typically, 44.2 mg of Cd(CH3COO)2·2H2O was added into 20 mL of anhydrous ethanol in a 40 mL glass vial and kept reflux at 80 °C under magnetic stirring. Then, 12.4 mg of TAA was added and kept reflux for 10 h.