Figure 5. Fluorescence quenching of tryptophan-related chromophores in EPS caused by ZnONPs and SiO₂NPs.

(A) Stern-Volmer plot; (B) plot of log [(F₀−F)/F] vs. log [Q]. This result was obtained via the aforementioned micro-titration experiments (see Materials and Methods). The changes in the fluorescence intensity of tryptophan-related chromophores in the EPS located at EX/EM = 278 nm/339 nm were recorded during the ZnONP/SiO₂NP titration. The statistical parameters are A: ZnONPs, R² = 0.91, p < 0.01; SiO₂NPs: R² = 0.83, p < 0.01; B: ZnONPs, R² = 0.95, p < 0.01; SiO₂NPs: R² = 0.58, p = 0.14.