As the temperature was increased, the color of the reaction solution changed gradually from yellow to red, dark red, and black, indicating the nucleation and growth of Cd–CIS NCs. Small amounts of the reaction solution (0.1–0.2 mL) were collected using a syringe at different time intervals and injected into hexane in clean vials to terminate growth of NCs. All solutions collected from the experiment were diluted in a glass cuvette with hexane for UV–Vis absorbance and photoluminescence (PL) measurements. Purification of Cd–CIS NCs was performed using hexane and ethanol.