Coupling room-temperature phosphorescence carbon dots onto active layer for highly efficient photodynamic antibacterial chemotherapy and enhanced membrane properties

Abstract

Biofouling has become a concerning issue in developing thin-film composite (TFC) forward osmosis (FO) membranes. The attachment of microorganisms onto the TFC FO membrane surface seriously influenced the membrane life span, resulting in the increased operation and maintenance costs. Herein, room-temperature phosphorescence (RTP) carbon dots using isophthalic acid (IPA) as a carbon source (IPA-C-dots) and nanocomposites by conjugation of IPA-C-dots with polylysine (PLL) (IPA-C-dots/PLL) were synthesized. The TFC FO membranes were coupled with nothing, PLL and IPA-C-dots/PLL to prepare control membrane (Control-M), PLL one (PLL-M), and IPA-C-dots/PLL one (IPA-C-dots/PLL-M), respectively. Due to the excellent hydrophilicity and smoothness of the membrane surface, the IPA-C-dots/PLL-M shows much higher water permeability, lower structural parameter, and acceptable salt rejection, resulting in enhanced membrane properties. What is more, the static and dynamic bio-fouling resistant tests indicate IPA-C-dots/PLL-M possesses a significant anti-biofouling property. The reason for this observation lay in the coupled IPA-C-dots can generate singlet oxygen (1O2) through energy transfer from excited triplet state to dissolved triplet oxygen under light irradiation, which can be served as a photodynamic antibacterial chemotherapy reagent, bettering the biofouling resistance properties. The conjugation of RTP C-dots onto TFC FO membranes opened up a promising door for the high efficient inhibition of bacterial proliferation and the enhancement of membrane properties.