Abstract
Covalent bonding of graphene oxide quantum dots (GOQDs) onto amino modified polyvinylidene fluoride (PVDF) membrane has generated a new type of nano-carbon functionalized membrane with significantly enhanced antibacterial and antibiofouling properties. A continuous filtration test using E. coli containing feedwater shows that the relative flux drop over GOQDs modified PVDF is 23%, which is significantly lower than those over pristine PVDF (86%) and GO-sheet modified PVDF (62%) after 10 h of filtration. The presence of GOQD coating layer effectively inactivates E. coli and S. aureus cells, and prevents the biofilm formation on the membrane surface, producing excellent antimicrobial activity and potentially antibiofouling capability, more superior than those of previously reported two-dimensional GO sheets and one-dimensional CNTs modified membranes. The distinctive antimicrobial and antibiofouling performances could be attributed to the unique structure and uniform dispersion of GOQDs, enabling the exposure of a larger fraction of active edges and facilitating the formation of oxidation stress. Furthermore, GOQDs modified membrane possesses satisfying long-term stability and durability due to the strong covalent interaction between PVDF and GOQDs. This study opens up a new synthetic avenue in the fabrication of efficient surface-functionalized polymer membranes for potential waste water treatment and biomolecules separation.
Highlights
Incorporating biocidal nanostructure materials into membranes has been regarded as an effective way to impart antimicrobial and antibiofouling properties to the membrane
Atomic force microscopy (AFM) image reveals that the topographic height of Graphene oxide quantum dots (GOQDs) is about 0.7 nm (Fig. 1d), which is consistent with the thickness of monolayer graphene
UV-vis absorption spectrum shows that GOQDs aqueous solution possess a broad absorption below 580 nm, and the emission wavelengths are excitation-dependent and exhibit a red shift with increasing excitation wavelengths, which might be due to the different emissive sites of the synthesized GOQDs (Figure S1c)
Summary
Incorporating biocidal nanostructure materials into membranes has been regarded as an effective way to impart antimicrobial and antibiofouling properties to the membrane. Biocidal single-walled carbon nanotubes (SWNTs) and graphene oxide (GO) nanosheets were used to functionalize polyamide membranes by Elimelech’s group[13,15], which show enhanced antibacterial activity. These 1 D or 2 D carbon materials on membranes still cannot be highly efficient in inhibiting the colonization of bacteria. Compared with bulk GO nanosheets, GOQDs exhibit zero-dimensional (0 D) distinctive electronic and optical properties owing to their large edge effects and quantum confinement This results in better peroxidase-like activity than graphene nanosheets because of their unique electron transport property[17,18,19,20]. Its antibacterial activity is superior to previously reported 2 D GO sheets and 1 D carbon nanotube modified polymer membranes[12,13,14,15]
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