Integration of nitrogen-doped carbon dots onto active layer of forward osmosis membrane for highly efficient antibacteria and enhanced membrane performances

Biofouling severely hampered the development of thin-film composite (TFC) forward osmosis (FO) membrane. Herein, novel nitrogen-doped carbon dots (N-C-dots) with fluorescence and long-lived afterglow dual-emission were fabricated using Na2EDTA and urea as co-precursors. The N-C-dots aqueous solution can synchronously produce superoxide anion radical (O2-ˑ) and singlet oxygen (1O2) under light irradiation, exhibiting immense nanoenzyme activities. The membranes (PEI-M and N-C-dots/PEI-M) were prepared by grafting PEI and N-C-dots/polyethyleneimine nanocomposites (N-C-dots/PEI) onto the active layer of pristine TFC FO membrane (Control-M), respectively. The N-C-dots/PEI-M exhibited much better hydrophilicity and smoothness than Control-M and PEI-M, resulting in a higher water permeability. Most significantly, N-C-dots/PEI-M possessed a unique dual-mode biofouling resistance, which responded to the potentials of N-C-dots as oxidase mimic and photosensitizer. In dynamic sewage treatment test, N-C-dots/PEI-M displayed much lower reduction in water flux and much better anti-biofouling behavior. Results above demonstrated that the modification strategy with N-C-dots/PEI is highly effective, pioneering a new horizon for the highly efficient inhibition of biofilm growth and biofouling development under visible light. •Preparation of N-doped C-dots with fluorescence and phosphorescence emission.•N-doped C-dots exhibited oxidase-like and oxygen photosensitization activities.•The physicochemical properties of modified membranes were greatly improved.•N-C-dots/PEI-M showed a dual-mode antibacteria and boosted FO properties.