The photocatalytic reduction of methylene blue was recognized as an economical and effective way for dye removal. To enhance photocatalytic activity under visible-light condition, fluorine and graphene synergistically modified TiO₂ (F-TiO₂/rGO) nanocomposites were successfully prepared by sol–gel method. Characterization results showed F ions played an essential role in the formation of TiO₂ nanoparticles. Between the fluorine sources selected, NH₄F was more optimal than NaF doping on the grounds that the existence of Na⁺ ion was an inevitable factor for the production of brookite. F-TiO₂/rGO nanocomposite obtained by adding 5%at NH₄F significantly narrowed the bandgap energy from approximately 3.17 to 2.41 eV. Box–Behnken design was adopted to optimize the MB photo-degradation process by F_(5%NH4F)-TiO₂/rGO nanocomposites under different reaction conditions. Moreover, the antibacterial behaviour of this novel material was also investigated by Escherichia coli (E. coli) bacteria under visible light. The morphology changes of E. coli cells were directly observed by field emission scanning electron microscope and further confirmed that the excellent sterilization of F-TiO₂/rGO nanocomposites resulted from the active species. The outstanding photocatalytic performance and antibacterial behaviour of F-TiO₂/rGO nanocomposite was attributed to the synergistic effect of photocatalytic redox reaction and adsorption. These results indicated F_(5%NH4F)-TiO₂/rGO nanocomposite was a promising antibacterial photo-adsorbent for wastewater treatment improvement. GRAPHICAL ABSTRACT

Ambient particles contribute to occupant exposure as they infiltrate indoor environments through building envelope cracks, impacting indoor air quality. This study investigates the impact of indoor air humidity on the infiltration of ambient particles, highlighting humidity’s crucial role in influencing particle dynamics in indoor environments. Employing a controlled chamber system, we conducted experiments to quantify the infiltration of size-resolved particles under varying relative humidity (RH) conditions. Both the total number and the mass concentration of particles increased with RH in the experimental chamber. The smallest particles (0.3–0.4 μm) experienced reduced infiltration at higher RH levels due to hygroscopic growth, while intermediate-sized particles showed increased infiltration, resulted from coagulation effects. Large particles (>1.0 μm) demonstrated reduced infiltration factors, caused by lower penetration and higher deposition rates, with minimal impact from RH changes. Our findings reveal that RH influences particle hygroscopic growth, deposition rate, and coagulation process, thereby affecting indoor particle size distribution and concentration.