Fig. 4. (a–c) UV-Vis spectra and (d–f) Tauc plots: (a, d) variation of the concentration of the precursor solution (pH: 7; reaction time: 15 min; stirring: 100 rpm), (b, e) variation of the pH of the precursor solution (concentration of solution: 0.01 M; reaction time: 15 min; stirring: 100 rpm), and (c, f) variation of the reaction time of precursor solution (pH: 10; concentration of solution: 0.01 M; stirring: 100 rpm).
