Antifouling PVDF Membrane by Surface Covalently Anchoring Functionalized Graphene Quantum Dots

Abstract

To construct antifouling polyvinylidene fluoride (PVDF) membranes, L-aspartic acid (L-asp)-modified graphene quantum dots (AGQDs) were covalently anchored on the PVDF membrane surface via a three-step modification method. The pristine PVDF membrane was first dehydrofluorinated to generate internal double bonds under the alkali solution. Then diamine (EDA) and two types of hyperbranched polyethyleneimines (HPEI) were grafted on the alkali-treated surfaces through the Michael addition reaction. Finally, the as-synthesized AGQDs were chemically immobilized on the amine-grafted surfaces via an amidation reaction. The surface morphologies and surface properties of the pristine and modified PVDF membranes were comprehensively characterized by X-ray photoelectron spectroscopy, ATR-FTIR, scanning electron microscope, atomic force microscope, and dynamic antifouling experiments. Meanwhile, the grafting efficiency of AGQDs were found to be strongly dependent on the type of amine used. Compared with EDA and HPEI L , HPEI H with a high molecular weight preferred to be grafted on membrane surfaces rather than membrane pores because of its larger steric hindrance, which facilitate the covalent anchorage of AGQDs on the HPEI H -grafted surface. Thanks to the high grafting efficiency of AGQDs, the resulting PVDF-HPEI H -AGQDs membrane possessed the excellent hydrophilicity (water contact angle as low as 58.7°). Most importantly, this membrane demonstrated superior antifouling performance over the pristine PVDF membrane in the presence of either the positively charged foulant (e.g., lysozyme) or the negatively charged foulant (e.g., bovine serum albumin). This novel membrane fabrication approach developed in this study provides a promising solution to covalently anchor hydrophilic nanoparticles on the PVDF membrane surface for antifouling enhancement.

Electrostatic and Covalent Binding of an Antibacterial Polymer to Hydroxyapatite for Protection against Escherichia coli Colonization

“…It can be inferred that, like the polymer-coated glass surfaces, covalent attachment of the polymer to PIIID-HA discs does not inhibit the nascent antibacterial activity of the polymer. It is also a possibility that covalently coating PIIID-HA disc and PIIID-glass surfaces with the polymer makes these surfaces bacteria repellent, and consequently, the number of bacteria that colonize the surfaces are much smaller compared to the corresponding control surfaces [ 77 , 78 ]. The data from the contact angle measurements performed on PIIID-glass surfaces coated with the polymer certainly hint towards changes in the surface energy of the materials upon covalent attachment of the polymer [ 79 , 80 ].…”

Integration of Hydrated Antimony Pentoxide in Poly(vinylidene fluoride) Films for Enhanced Energy Storage and Harvesting

“…The F 1s peak position (687.60 eV) of PVDF/HAP has recorded a minor shift from the F 1s peak of pure PVDF (687.75 eV). The deviation can be ascribed to the intermolecular interaction to the highly polarized backbone’s (−H δ+ –C δ+ –F δ− – dipoles) hydrogen atom of PVDF and −OH of HAP. , The zoom-in of the C 1s peak position in PVDF and PVDF/HAP shows that the C 1s spectrum is showing three peaks corresponding to −CH 2 and −CF 2 of the PVDF backbone at the positions of 290.9 and 286.6 eV, respectively; the third shoulder peak is related to the nonoxygenated carbon (−C x H y −) at the position 284.6 eV. In PVDF/HAP, the C 1s positions corresponding to −CH 2 and −CF 2 are shifted to higher binding energy caused by the presence of oxygenated carbon.…”

“…As a result, the binding energy of the lattice oxygen corresponds to 530.04, 531.31, and 532.41 eV, which are corresponding to the adsorbed oxygen, surface hydroxyl oxygen, and lattice oxygen, respectively.The F 1s peak position (687.60 eV) of PVDF/HAP has recorded a minor shift from the F 1s peak of pure PVDF (687.75 eV). The deviation can be ascribed to the intermolecular interaction to the highly polarized backbone's (−H δ+ −C δ+ −F δ− − dipoles) hydrogen atom of PVDF and −OH of HAP 40,41. The zoom-in of the C 1s peak position in PVDF and PVDF/HAP shows that the C 1s spectrum is showing three peaks corresponding to −CH 2 and −CF 2 of the PVDF backbone at the positions of 290.9 and 286.6 eV, respectively; the third shoulder peak is related to the nonoxygenated carbon (−C x H y −) at the position 284.6 eV.…”

Advances in Integrating Carbon Dots With Membranes and Their Applications

“…PVDF has many excellent properties, so it is a popular membrane material. Shao et al [50] . covalently anchored ACDs on the surface of PVDF membranes.…”