Wen-Ze Qiu

Co-deposition of catechol/polyethyleneimine on porous membranes for efficient decolorization of dye water

Mussel-inspired chemistry has been broadly exploited for multifunctional coatings in the surface modification of applied materials. Polyphenols are ubiquitous in plant tissues and far less expensive than polydopamine for mussel-inspired chemistry. Herein, we report a facile and effective method to modify porous membranes via the co-deposition of catechol (CCh) and polyethyleneimine (PEI). The membrane structures and properties were investigated by ATR/FTIR, XPS, FESEM, zeta potential, water contact angle and pure water flux measurements. The results reveal that the membranes deposited with a CCh–PEI mass ratio of 1:0.25 show excellent hydrophilicity, ultrahigh water permeation flux and distinguished surface charges. These membranes were used to decolorize anionic dye solutions during filtration with superior removal efficiencies of over 99%. Moreover, they have good reusability over repeated operations with a simple regeneration process.

Nanocomposite Membranes via the Codeposition of Polydopamine/Polyethylenimine with Silica Nanoparticles for Enhanced Mechanical Strength and High Water Permeability

A defect-free and stable selective layer is of critical significance for thin film composite membrane with excellent separation performance and service durability. We report a facial strategy for fabricating thin film nanocomposite (TFN) nanofltration membranes (NFMs) based on the codeposition of polydopamine, polyetheylenimine, and silica nanoparticles. Tripled water flux can be obtained from the TFN NFMs as compared with those NFMs without silica nanoparticles. This is ascribed to the improved wettability of the membrane surfaces and the enlarged pore sizes of the selective layer. The interfacial compatibility of the inorganic fillers and the polymer matrices can be enhanced by the electrostatic interactions of silica nanoparticles with polyethylenimine and the adhesive characteristics of polydopamine, resulting in a defect-free selective layer and then good rejection for both bivalent cations and neutral solutes. The rigid silica nanoparticles also improve the surface mechanical strength of the TFN NFMs effectively and lead to structural stability and compaction resistance during the long-term filtration process.

Polydopamine Coatings with Nanopores for Versatile Molecular Separation

The demand for highly efficient and multifunctional membranes in various separation processes is increasing. Recently, mussel-inspired polydopamine (PDA) has provided a promising way to meet these requirements because of its surface-adhesive property and film-forming ability. However, traditional PDA coatings usually suffer from the disadvantages of nonuniformity, incompactness, and instability, leading to poor molecular separation and service performance. Herein, uniform, compact, and robust PDA coatings were fabricated on an ultrafiltration substrate via a reasonable screening of oxidants for the oxidized self-polymerization of dopamine. The as-prepared PDA coatings were nanoporous (0.56 ± 0.04 and 0.93 ± 0.04 nm) with a thickness of ∼75 nm, which endows the composite membranes with a high solute rejection and solvent permeability during molecular separation. They are useful in organic solvent nanofiltration because of their superior structural stability. Moreover, the composite membranes can be used for recycling the nanometer catalyst from organic solvents for the first time, which has significantly broadened the potential applications of these mussel-inspired coatings for versatile separation processes.

Enzyme-triggered coatings of tea catechins/chitosan for nanofiltration membranes with high performance

We report a completely green and one-step protocol to fabricate selective layers for thin film composite nanofiltration membranes via the laccase-triggered co-deposition of natural tea catechins and chitosan. The constructed membranes show around 99% rejection of Na2SO4 with a high water permeation flux of 45 L m−2 h−1 under 0.6 MPa.

Composite nanofiltration membranes via the co-deposition and cross-linking of catechol/polyethylenimine

High performance nanofiltration (NF) membranes are facilely fabricated via the co-deposition of catechol (CCh) and polyethylenimine (PEI) on the surface of a polysulfone (PSf) ultrafiltration membrane, with subsequent cross-linking by glutaraldehyde (GA). The surface properties of the studied membranes have been investigated in detail by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning election microscopy, atomic force microscopy, zeta potential, and water contact angle. The NF performance of the membranes are dependent on the CCh/PEI ratio, co-deposition time and cross-linking condition. Results reveal that the optimum membrane yields a rejection of 88% and a permeation flux of 25 L m−2 h−1 when filtrating the 1000 mg L−1 MgCl2 solution at 0.6 MPa. And the negatively charged membrane surface is related to the following salt rejection sequence: MgSO4 > Na2SO4 > MgCl2 > CaCl2 > NaCl. Meanwhile, the membranes show excellent operation stability during a 240 h consistent filtration test.

Polydopamine-assisted deposition of heparin for selective adsorption of low-density lipoprotein

Low-density lipoprotein (LDL) is the main carrier of blood cholesterol, with elevated levels of LDL increasing the risk of atherosclerosis. Blood purification therapy is an option for serious cardiovascular diseases and familial hyperlipidemia, and the therapeutic effect is largely determined by the LDL adsorbent used. In this study, a facile method is proposed to prepare LDL capture surfaces. Coatings rich in heparin were prepared by co-depositing heparin and dopamine. The mixed coatings were thoroughly characterized by X-ray photoelectron spectroscopy, ellipsometry, atomic force microscopy and water contact angle measurements. Protein adsorption was analyzed by surface plasmon resonance and quartz crystal microbalance with dissipation monitoring, the results indicate that the heparin-incorporated coatings have great adsorption capacity and selectivity for LDL. In addition, the mixed coatings exhibit favorable blood compatibility in platelet adhesion assay. The described polydopamine-assisted heparin deposition process is a simple and universal method for LDL adsorbent preparation.

Dopamine-assisted co-deposition: An emerging and promising strategy for surface modification

Mussel-inspired chemistry based on polydopamine (PDA) deposition has been developed as a facile and universal method for the surface modification of various materials. However, the inherent shortcomings of PDA coatings still impede their practical applications in the development of functional materials. In this review, we introduce the recent progress in the emerging dopamine-assisted co-deposition as a one-step strategy for functionalizing PDA-based coatings, and improving them in the aspects of deposition rate, morphology uniformity, surface wettability and chemical stability. The co-deposition mechanisms are categorized and discussed according to the interactions of dopamine or PDA with the introduced co-component. We also emphasize the influence of these interactions on the properties of the resultant PDA-based coatings. Meanwhile, we conclude the representative potential applications of those dopamine-assisted co-deposited coatings in material science, especially including separation membranes and biomaterials. Finally, some important issues and perspectives for theoretical study and applications are briefly discussed.

Robust Coatings via Catechol–Amine Codeposition: Mechanism, Kinetics, and Application

Bioinspired polyphenol/polyamine codeposition has been demonstrated by the competence for surface modification; however, the reaction processes including mechanism and kinetics remain superficially understood. In this work, the catechol (CA)-amine reaction has been thoroughly investigated by using CA and two amines m-phenylenediamine and piperazine. We verify that both primary and secondary amines are prone to link with CA through Michael addition to form polyphenol/polyamine oligomers under aerobic and mild-alkaline conditions. Molecular simulations indicate that the Michael addition products are dominant for both aromatic and aliphatic amines with CA, which supports the durable chem- and phystability of the codeposited coatings. The aggregation kinetics of polyphenol/polyamine is provided for the first time, and the formed aggregates show high-adhesive properties, which can be deposited as the skin layers for high-performance nanofiltration membranes.