Figure indicates the PL spectra of TiO2, SnO2, and g-C3N4; the spectra undergo Gaussian peak fitting to find component peaks. Figure (a) indicates that TiO2 has 3 peaks at 1.82, 2.26, and 2.91 eV accounting for 20.4 %, 71.8 %, and 7.8 %, respectively. While the PL peak fitting of SnO2 (Figure (b)) has 3 peaks at 1.79 eV, 2.03 eV, and 2.86 eV accounting for 41.2 %, 55.9 %, and 2.9 %, respectively. According to previous studies, these peaks of both TiO2 and SnO2 correspond to their instinct oxygen vacancies, which impact the charge carrier's separation resulting in a better photocatalytic performance .