| Sample name | Absorption Peak (nm) | Eg value (eV) (n = 3) |
| S1 (pH 3) | 363 | 3.43 ± 0.1 |
| S2 (pH 5) | 363 | 3.43 ± 0.1 |
| S3 (pH 8) | 360 | 3.40 ± 0.1 |
| S4 (pH 10) | 362 | 3.43 ± 0.1 |
| S5 (pH 12) | 363 | 3.43 ± 0.1 |