Dual-functional membranes of CQDs/TiO₂ @PI/PES nanofibers for the high filter efficiency of ultrafine particles and photocatalytic activity

The carbon quantum dot/titanium dioxide (CQDs/TiO2), fabricated on highly porous polyimide (PI)/polyether sulfone (PES) nanofiber via electrospinning process, called the dual-functional CQD/TiO2 @PI/PES membrane, was developed and evaluated for its performance, including both removal of volatile organic compounds (VOCs) and ultrafine particulate matters (PM0.1). The photocatalytic activity of synthesized CQD/TiO2 @PI/PES membranes with 5% CQD loading on the decomposition of acetone was significantly enhanced compared with that of TiO2(P25)@PI/PES. The comprehensive results of photoluminescence emission, X-ray photoelectron spectroscopy, and photocatalytic experiments suggest that up-conversion properties of CQD can enhance the absorption of visible light on TiO2 and reduce the reorganization of electron-hole pairs. Further, the optimized CQD/TiO2 @PI/PES membrane could effectively photodegrade of acetone (>94.5%) and also maintained a good PM0.1 filtration efficiency (> 99%) and a differential pressure of 0.34 Pa for creating level 3 medical face masks as per the standards of ASTM F2299 and EN 14683. Therefore, the dual-functional CQD/TiO2 @PI/PES membrane could be applied as a promising photocatalytic filter for air purification that simultaneously and remarkably filters PM0.1 and decompose VOCs.