Mussel-Inspired Architecture of High-Flux Loose Nanofiltration Membrane Functionalized with Antibacterial Reduced Graphene Oxide-Copper Nanocomposites

Design of MOF-Based Solar Evaporators With Hierarchical Microporous/Nanobridged/Nanogranular Structures for Rapid Interfacial Solar Evaporation and Fresh Water Collection

Interfacial solar evaporation (ISE) holds considerable promise to solve fresh water shortage, but it is challenging to achieve high evaporation rate (Reva) and fresh water yield in close system. Here, we report design and preparation of MOF-based solar evaporators with hierarchical microporous/nanobridged/nanogranular structures for rapid ISE and fresh water collection in close system. The evaporators are fabricated by growing silicone nanofilaments with variable length as nanobridges on a microporous silicone sponge followed by grafting with polydopamine nanoparticles and Cu-MOF nanocrystals. Integration of the unique structure and excellent photothermal composites endows the evaporators with high Reva of 3.5-20 wt % brines (3.60-2.90 kg m-2 h-1 in open system and 2.38-1.44 kg m-2 h-1 in close system) under simulated 1 sun, high Reva under natural sunlight, excellent salt resistance and high fresh water yield, which surpass most state-of-the-art evaporators. Moreover, when combined with a superhydrophilic cover, the evaporators show much higher average Reva of real seawater, remarkable fresh water yield and excellent long-term stability over one month continuous ISE under natural sunlight. The findings here will promote the development of advanced evaporators via microstructure engineering and their real-world ISE applications.

Preparation of a CPVC composite loose nanofiltration membrane based on plant polyphenols for effective dye wastewater treatment

The textile industry's high-salinity wastewater presents a significant difficulty for fractioning salts and dyes. To fractionate the dyes and salts, a high-performance CPVC composite loose nanofiltration membrane (LNM) was fabricated by interfacial polymerization. The organic phase was obtained by crosslinking polyethylenimine (PEI) with tannic acid (TA) and gallic acid (GA) using TMC. The resultant composite LNM performance was enhanced by adjusting the coating parameters, which included TA and GA concentrations as well as coating time. The study examined the effects of the total content of TA/PEI and GA/PEI concentrations on the chemical structure, surface roughness, and microstructure of the selective layer of LNM using SEM, AFM, FTIR, and water contact angle measurements. It also investigated the filtration performance of the membrane's selective layer, including pure water flux, PEG800 rejection rate, and membrane fouling analysis. However, the resultant membrane treated simulated reactive black 5 (RB5) dye wastewater. When the total content of TA/PEI is 4 kg L-1, the permeability of pure water flux is high at 7.5 L per m2 per h per bar when the total content of GA/PEI is 14 kg L-1 and the pure water flux is high at 8.8 L per m2 per h per bar. The overall PEG800 rejection rates were 97-98.98%. The optimal TA : PEI ratios reached a good pure water permeability up to 6.4 L per (m2 per h per bar) with a high rejection rate of 99.69% for a ratio 1/3 to dye, and GA : PEI ratios reached a good water permeability at 5.5 and 6.5 L per (m2 per h per bar) with rejection rates of 99.21% and 98.88% for ratio 1/3 and 3.5/10.5 for simulated RB5 dye, and the NaCl retention rate gradually decreased from 4% to 3%. The resultant LNM demonstrated promising applications in dye and salt fractionation.

Low Fouling Polyelectrolyte Layer-by-Layer Self-Assembled Membrane for High Performance Dye/Salt Fractionation: Sequence Effect of Self-Assembly

Layer-by-layer (LbL) self-assembly of oppositely charged polyelectrolytes (PEs) is usually performed on a conventional ultrafiltration base substrate (negative zeta potential) by depositing a cationic PE as a first layer. Herein, we report the facile and fast formation of high performance molecular selective membrane by the nonelectrostatic adsorption of anionic PE on the polyvinylidene fluoride (PVDF, zeta potential -17 mV) substrate followed by the electrostatic LbL assembly. Loose nanofiltration membranes have been prepared via both concentration-polarization (CP-LbL, under applied pressure) driven and conventional (C-LbL, dipping) LbL self-assembly. When the first layer is poly(styrene sodium) sulfonic acid, the LbL assembled membrane contains free -SO3- groups and exhibits higher rejection of Na2SO4 and lower rejection of MgCl2. The reversal of salt rejection occurs when the first layer is quaternized polyvinyl imidazole (PVIm-Me). The membrane (five layers) prepared by first depositing PStSO3Na shows higher rejection of several dyes (97.9 to >99.9%), higher NaCl to dye separation factor (52-1800), and higher dye antifouling performance as compared to the membrane prepared by first depositing PVIm-Me (97.5-99.5% dye rejection, separation factor ∼40-200). However, the C-LbL membrane requires a longer time of self-assembly or higher PE concentration to reach a performance close to the CP-LbL membranes. The membranes exhibit excellent pressure, pH (3-12), and salt (60 g L-1) stability. This work provides an insight for the construction of low fouling and high-performance membranes for the fractionation of dye and salt based on the LbL self-assembly sequence.

Surface Bioengineering of Mo2Ga2C MAX Phase to Develop Blended Loose Nanofiltration Membranes for Textile Wastewater Treatment

The potential of blended loose nanofiltration membranes (LNMs) to fractionate dyes and inorganic salts in textile wastewater has become a focus of attention in recent years. In this research work, we fabricated LNMs based on polysulfone (PSf) membranes blended with l-histidine amino acid-functionalized Mo2Ga2C MAX phase (His-MAX). Scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), contact angle, ζ-potential, porosity, and pore size analyses were employed to characterize the LNMs. Blending 0.75 wt % of His-MAX additive with the PSf tailored the LNM's features by making it more water-friendly, increasing its porosity, enlarging its pores, and making its surface smoother. The pure water flux of 127.6 L/m2 h was achieved by LNM containing 0.75 wt % His-MAX, which was 2.5 times greater than the bare one. The mentioned LNM displayed a flux recovery ratio (FRR) of 68.27 and 98.57, 98.31, and 99.7% rejections for Direct red 23, Acid brown 75, and Reactive blue 21 solutions (100 mg/L), respectively. The 0.75 wt % His-MAX LNM could reject 99.1% of dye and 11.5% of salt while maintaining an FRR of 91.19% after four cycles of filtering a binary mixture solution containing Reactive blue 21 and Na2SO4. These findings highlight the potential of the fabricated LNM for desalinating dye solutions.

Covalent Organic Network Membranes with Tunable Nanoarchitectonics from Macrocycle Building Blocks for Graded Molecular Sieving

Traditional piperazine-based polyamide membranes usually suffer from the intrinsic trade-off relationship between selectivity and permeance. The development of macrocycle membranes with customized nanoscale pores is expected to address this challenge. Herein, we introduce 1,4-diazacyclohexane (2N), 1,4,7-triazacyclononane (3N), and 1,4,8,11-tetraazacyclotetradecane (4N) as molecular building blocks to construct the nanoarchitectonics of polyamide membranes prepared from interfacial polymerization (IP). The permeance of covalent organic network membranes follows the trend of 4N-TMC > 3N-TMC > 2N-TMC, while the molecular weight cutoff (MWCO) also follows the same trend of 4N-TMC > 3N-TMC > 2N-TMC, according to their nanopore size of the membranes. The microporosity, orientation, and surface chemistry of covalent organic network membranes can be rationally designed by macrocycle building units. The ordered nanoarchitectonics allows the membranes to attain an excellent performance in graded molecular sieving. Importantly, the novel covalent organic network membranes with tunable nanoarchitectonics prepared from macrocycle building units exhibited high water permeance (32.5 LMH/bar) and retained long-term stability after 100 h of test and bovine serum albumin fouling. These results reveal the enormous potential of 3N-TMC and 4N-TMC membranes in saline textile wastewater treatments and precise molecular sieving.

Transforming Dye Molecules into Electrochemical Allies: Direct Red 80 as a Dual-Functional Electrolyte Additive for Dendrite-Free Aqueous Zinc-Ion Batteries

Despite the numerous advantages of abundant zinc resources, low redox potential, and affordability, aqueous zinc-ion batteries (AZIBs) currently face limitations due to dendritic growth and side reactions. This study explores the use of low-cost and efficient anionic dyes, specifically Direct Red 80 (DR80) as dual-functional electrolyte additives to enhance the electrochemical performance of AZIBs and facilitate the reuse of dye wastewater. Experimental and theory calculation results all demonstrate that the DR80 molecules readily adsorb onto the surface of the zinc anode, creating a stable and robust solid electrolyte interphase layer. This layer acts as a protective barrier, effectively mitigating H+ attacks and reducing both hydrogen evolution and corrosion reactions. Additionally, it covers any initial protrusions on the zinc anode, preventing the occurrence of the "tip-effect" phenomenon and limiting access of water to the zinc anode, thereby minimizing water decomposition. Moreover, the sulfonic acid groups of DR80 molecules displace some water molecules in [Zn(H2O)6]2+, disrupting the original solvent sheath and reducing water decomposition. Especially, using the DR80 additive, the Zn/Zn cell reaches an impressive cycle life of 1500 h at 2 mA cm-2@1 mAh cm-2. Given the low cost and widespread availability, this additive shows great potential in the future practical implementation of AZIBs.

Size Effect of Cu Nanoparticles in Cu/g-C3N4 Composites on Properties for Highly Efficient Photocatalytic Reduction of CO2 to Methanol

The main goal of this work is to develop cheap photocatalysts for the efficient photocatalytic reduction of CO2 to methanol with water. A series of composites of Cu/g-C3N4 were prepared via a solvothermal method. Copper nanoparticle (Cu NP) size in Cu/g-C3N4 can be easily controlled by adjusting the synthesis temperature. The Cu/g-C3N4 material with the proper size of Cu NP (CuCN-100) had the best photocatalytic property (675 μmol·g-1·h-1) in reducing the amount of CO2 to methanol at room temperature under normal pressure. The particle size of Cu NPs is the key factor to improve the catalytic activity and stability because of the improved transfer and separation of photogenerated charges with the small Cu NPs. Although the sample with large Cu NPs (CuCN-200) initially gave a better activity than that of CuCN-100 due to the formation of double heterojunction, its activity was thoroughly lost after two runs resulting from the continuous photocorrosion. This work provides a valuable insight for preparing efficient semiconductor-metal photocatalysts.

Verma S, Panda PK, Jerman I. Boosting Copper Biocidal Activity by Silver Decoration and Few-Layer Graphene in Coatings on Textile Fibers

The outbreak of the Coronavirus disease 2019 (COVID-19) pandemic has highlighted the importance of developing antiviral surface coatings that are capable of repelling pathogens and neutralizing them through self-sanitizing properties. In this study, a novel coating design based on few-layer graphene (FLG) is proposed and silver-decorated micro copper flakes (CuMF) that exhibit both antibacterial and antiviral properties. The role of sacrificial anode surfaces and intrinsic graphene defects in enhancing the release of metal ions from CuMF embedded in water-based binders is investigated. In silico analysis is conducted to better understand the molecular interactions of pathogen-repelling species with bacterial or bacteriophage proteins. The results show that the optimal amount of CuMF/FLG in the coating leads to a significant reduction in bacterial growth, with reductions of 3.17 and 9.81 log for Staphylococcus aureus and Escherichia coli, respectively. The same coating also showed high antiviral efficacy, reducing bacteriophage phi6 by 5.53 log. The antiviral efficiency of the coating is find to be doubled compared to either micro copper flakes or few-layer graphene alone. This novel coating design is versatile and can be applied to various substrates, such as personal protective clothing and face masks, to provide biocidal activity against both bacterial and viral pathogens.

Essential Oil Nanoemulsion Hydrogel with Anti-Biofilm Activity for the Treatment of Infected Wounds

The formation of a bacterial biofilm on an infected wound can impede drug penetration and greatly thwart the healing process. Thus, it is essential to develop a wound dressing that can inhibit the growth of and remove biofilms, facilitating the healing of infected wounds. In this study, optimized eucalyptus essential oil nanoemulsions (EEO NEs) were prepared from eucalyptus essential oil, Tween 80, anhydrous ethanol, and water. Afterward, they were combined with a hydrogel matrix physically cross-linked with Carbomer 940 (CBM) and carboxymethyl chitosan (CMC) to prepare eucalyptus essential oil nanoemulsion hydrogels (CBM/CMC/EEO NE). The physical-chemical properties, in vitro bacterial inhibition, and biocompatibility of EEO NE and CBM/CMC/EEO NE were extensively investigated and the infected wound models were proposed to validate the in vivo therapeutic efficacy of CBM/CMC/EEO NE. The results showed that the average particle size of EEO NE was 15.34 ± 3.77 nm with PDI ˂ 0.2, the minimum inhibitory concentration (MIC) of EEO NE was 15 mg/mL, and the minimum bactericidal concentration (MBC) against S. aureus was 25 mg/mL. The inhibition and clearance of EEO NE against S. aureus biofilm at 2×MIC concentrations were 77.530 ± 7.292% and 60.700 ± 3.341%, respectively, demonstrating high anti-biofilm activity in vitro. CBM/CMC/EEO NE exhibited good rheology, water retention, porosity, water vapor permeability, and biocompatibility, meeting the requirements for trauma dressings. In vivo experiments revealed that CBM/CMC/EEO NE effectively promoted wound healing, reduced the bacterial load of wounds, and accelerated the recovery of epidermal and dermal tissue cells. Moreover, CBM/CMC/EEO NE significantly down-regulated the expression of two inflammatory factors, IL-6 and TNF-α, and up-regulated three growth-promoting factors, TGF-β1, VEGF, and EGF. Thus, the CBM/CMC/EEO NE hydrogel effectively treated wounds infected with S. aureus, enhancing the healing process. It is expected to be a new clinical alternative for healing infected wounds in the future.

Tuning CO2 Hydrogenation Selectivity through Reaction-Driven Restructuring on Cu-Ni Bimetal Catalysts

Tuning the selectivity of CO2 hydrogenation is of significant scientific interest, especially using nickel-based catalysts. Fundamental insights into CO2 hydrogenation on Ni-based catalysts demonstrate that CO is a primary intermediate, and product selectivity is strongly dependent on the oxidation state of Ni. Therefore, modifying the electronic structure of the nickel surface is a compelling strategy for tuning product selectivity. Herein, we synthesized well dispersed Cu-Ni bimetallic nanoparticles (NPs) using a simple hydrothermal method for CO selective CO2 hydrogenation. A detailed study on the monometallic (Ni and Cu) and bimetallic (CuxNi1-x) catalysts supported on γ-Al2O3 was performed to increase CO selectivity while maintaining the high reaction rate. The Cu0.5Ni0.5/γ-Al2O3 catalyst shows a high CO2 conversion and more CO product selectivity than its monometallic counterparts. The surface electronic and geometric structure of Cu0.5Ni0.5 bimetallic NPs was studied using ambient pressure X-ray photoelectron spectroscopy (AP-XPS) and in situ diffuse reflectance infrared Fourier-transform spectroscopy under reaction conditions. The Cu core atoms migrate toward the surface, resulting in the restructuring of the Cu@Ni core-shell structure to a Cu-Ni alloy during the reaction and functioning as the active site by enhancing CO desorption. A systematic correlation is obtained between catalytic activity from a continuous fixed-bed flow reactor and the surface electronic structural details derived from AP-XPS results, establishing the structure-activity relationship. This investigation contributes to providing a strategy for controlling CO2 hydrogenation selectivity by modifying the surface structure of bimetallic NP catalysts.

Ultrathin Graphene Oxide-Based Nanocomposite Membranes for Water Purification

Two-dimensional graphene oxide (GO)-based lamellar membranes have been widely developed for desalination, water purification, gas separation, and pervaporation. However, membranes with a well-organized multilayer structure and controlled pore size remain a challenge. Herein, an easy and efficient method is used to fabricate MoO₂@GO and WO₃@GO nanocomposite membranes with controlled structure and interlayer spacing. Such membranes show good separation for salt and heavy metal ions due to the intensive stacking interaction and electrostatic attraction. The as-prepared composite membranes showed high rejection rates (˃70%) toward small metal ions such as sodium (Na⁺) and magnesium (Mg²⁺) ions. In addition, both membranes also showed high rejection rates ˃99% for nickel (Ni²⁺) and lead (Pb²⁺) ions with good water permeability of 275 ± 10 L m^-2 h^-1 bar^-1. We believe that our fabricated membranes will have a bright future in next generation desalination and water purification membranes.

Graphene materials: Armor against nosocomial infections and biofilm formation - A review

Graphene has revolutionized the field of energy and storage sectors. Out of the total number of nosocomial infections diagnosed all around the world, the majority of the cases (around 70%) are found to be due to the medical device or assistance utilized while treating the patient. Combating these diseases is vital as they cause a nuisance to the patients and medical practitioners. Coatings of graphene and its derivatives hold the key to the formation of special surfaces that can rupture microbial cells using their sharp edges, ultimately leading to nuclear and cellular fragmentation. Their incorporation as a whole or as a part in the hospital apparel and the medical device has aided medical practitioners to combat many nosocomial diseases. Graphene is found to be highly virulent with broad-spectrum antimicrobial activity against nosocomial strains and biofilm formation. Their alternate mode of action like trapping and charge transfer has also been discussed well in the present review. The various combinational forms of graphene with its conjugates as a suitable agent to combat nosocomial infections and a potential coating for newer challenges like COVID-19 infections has also been assessed in the current study. Efficiency of graphene sheets has been found to be around 89% with a reaction time as less as 3 h. Polymers with graphene seem to have a higher potency against biofilm formation. When combined with graphene oxide, silver nanoparticles provide 99% activity against nosocomial pathogens. In conclusion, this review would be a guiding light for scientists working with graphene-based coatings to unfold the potentials of this marvelous commodity to tackle the present and future pandemics to come.

Sonochemical synthesis of a copper reduced graphene oxide nanocomposite using honey and evaluation of its antibacterial and cytotoxic activities

The combination of graphene-based materials and inorganic nanoparticles for the enhancement of the nanomaterial properties is extensively explored nowadays. In the present work, we used a sonochemical method to synthesize a copper/reduced graphene oxide (Cu/RGO) nanocomposite using Australian honey and vitamin C as capping and reducing agents, respectively. The honey-mediated copper/reduced graphene oxide (H/Cu/RGO) nanocomposite was then characterized through UV-visible, XRD, HRTEM, and FTIR analysis. The copper nanoparticles (Cu-NPs) in the nanocomposite formed uniform spherical shapes with a size of 2.20 ± 0.70 nm, which attached to the reduced graphene oxide (RGO) layers. The nanocomposite could suppress bacterial growth in both types of bacteria strains. However, in this study, the nanocomposite exhibited good bactericidal activity toward the Gram-positive bacteria than the Gram-negative bacteria. It also showed a cytotoxic effect on the cancer colorectal cell line HCT11, even in low concentrations. These results suggested that the H/Cu/RGO nanocomposite can be a suitable component for biomedical applications.

Ganzoury M, Zhang N, de Lannoy CF. Nanocomposite Polymeric Membranes for Organic Micropollutant Removal: A Critical Review

The prevalence of organic micropollutants (OMPs) and their persistence in water supplies have raised serious concerns for drinking water safety and public health. Conventional water treatment technologies, including adsorption and biological treatment, are known to be insufficient in treating OMPs and have demonstrated poor selectivity toward a wide range of OMPs. Pressure-driven membrane filtration has the potential to remove many OMPs detected in water with high selectivity as a membrane's molecular weight cutoff (MWCO), surface charge, and hydrophilicity can be easily tailored to a targeted OMP's size, charge and octanol-water partition coefficient (Kow). Over the past 10 years, polymeric (nano)composite microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) membranes have been extensively synthesized and studied for their ability to remove OMPs. This review discusses the fate and transport of emerging OMPs in water, an assessment of conventional membrane-based technologies (NF, reverse osmosis (RO), forward osmosis (FO), membrane distillation (MD) and UF membrane-based hybrid processes) for their removal, and a comparison to the state-of-the-art nanoenabled membranes with enhanced selectivity toward specific OMPs in water. Nanoenabled membranes for OMP treatment are further discussed with respect to their permeabilities, enhanced properties, limitations, and future improvements.

Biofouling-Resistant Ultrafiltration Membranes via Codeposition of Dopamine and Cetyltrimethylammonium Bromide with Retained Size Selectivity and Water Flux

Biofouling is a serious problem in ultrafiltration (UF) membrane applications. Modifying the surface of membranes with low molecular weight, commercially available antibacterial chemistries is an excellent strategy to mitigate biofouling. Herein, we report a new strategy to impart antibacterial and anti-biofouling behavior without changing the support membrane's size selectivity and pure water permeance (PWP). To this end, a strong antibacterial agent, cetyltrimethylammonium bromide (CTAB), was codeposited with dopamine onto commercial polyethersulfone (PES) UF membranes in the presence of nitrogen (N₂) gas backflow. The PWP and pore size of the support membrane did not change with codeposition, confirming the benefit of N₂ backflow in mitigating the solution intrusion phenomenon. X-ray photoelectron spectroscopy (XPS), surface ζ potentials, and contact angle measurements confirmed the successful codeposition of polydopamine (PDA) and CTAB onto the membrane. Among three different CTAB concentrations systematically investigated, the membrane functionalized with CTAB at the critical micelle concentration (CMC) provided the best anti-biofouling activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria and retained its surface ζ potential after being stored in 1 M NaCl (pH = 6.8) for 3 months. Our results demonstrate the potential of using a facile, one-step approach to modify commercial UF membranes without compromising their pore size or flux, while simultaneously endowing antibacterial activity.

Graphene-Based Functional Hybrid Membranes for Antimicrobial Applications: A Review

Graphene-based nanomaterials have shown wide applications in antimicrobial fields due to their accelerated rate of pathogen resistance and good antimicrobial properties. To apply graphene materials in the antimicrobial test, the graphene materials are usually fabricated as two-dimensional (2D) membranes. In addition, to improve the antimicrobial efficiency, graphene membranes are modified with various functional nanomaterials, such as nanoparticles, biomolecules, polymers, etc. In this review, we present recent advances in the fabrication, functional tailoring, and antimicrobial applications of graphene-based membranes. To implement this goal, we first introduce the synthesis of graphene materials and then the fabrication of 2D graphene-based membranes with potential techniques such as chemical vapor deposition, vacuum filtration, spin-coating, casting, and layer-by-layer self-assembly. Then, we present the functional tailoring of graphene membranes by adding metal and metal oxide nanoparticles, polymers, biopolymers, metal–organic frameworks, etc., with graphene. Finally, we focus on the antimicrobial mechanisms of graphene membranes, and demonstrate typical studies on the use of graphene membranes for antibacterial, antiviral, and antifungal applications. It is expected that this work will help readers to understand the antimicrobial mechanism of various graphene-based membranes and, further, to inspire the design and fabrication of functional graphene membranes/films for biomedical applications.

Surface-Decorated Graphene Oxide Sheets with Copper Nanoderivatives for Bone Regeneration: An In Vitro and In Vivo Study Regarding Molecular Mechanisms, Osteogenesis, and Anti-infection Potential

It has been previously reported that graphene oxide/copper nanoderivative (GO/Cu)-incorporated chitosan/hyaluronic acid scaffolds might be promising wound dressings for the management of infected wound healing. The aim of the present research is to deeply explore the potential antimicrobial mechanisms and synergistic osteogenic activity, as well as the in vivo anti-infective behavior of GO/Cu nanocomposites, making them possible candidates for establishing implantable biomaterials for the repair of infected bone defects. The antibacterial mechanisms of the nanocomposites were explored through the examination of membrane integrity, oxidative stress, and metabolic enzyme activities. Then, the cytocompatibility with bone mesenchymal stem cells (rBMSCs) and osteogenic potential were confirmed, and a subcutaneous bacterial infection model in rats was also established to verify the in vivo anti-infective property and biosafety of the nanocomposites. It was found that leakage of adenosine triphosphate, proteins, and reducing sugars from the bacterial cells, indicative of damaged permeability of bacterial membranes, and promoted production of reactive oxygen species and disordered metabolic enzyme activities in response to oxidative stress were possible molecular mechanisms responsible for the synergistic antibacterial effects of the GO/Cu nanocomposites. Additionally, good cytocompatibility with rBMSCs and promoted osteogenic differentiation were found in GO/Cu nanocomposites (mass ratio = 2:1), which also demonstrated satisfactory in vivo anti-infective performance, reduced inflammation, and acceptable biosafety. Based on our results, damaged bacterial membranes, increased ROS production, and disorders of crucial enzyme metabolism were the main antibacterial mechanisms involved in the bacterium-killing events caused by the GO/Cu nanocomposites, which also showed enhanced osteogenic activity, in vivo anti-infective capability, and acceptable cytocompatibility and biosafety. Therefore, GO/Cu (2:1) nanocomposites are a potential strategy for improving the biological performance of current bone substitutes used for combating bacterial-contaminated bone defects.

Modification strategies of membranes with enhanced Anti-biofouling properties for wastewater Treatment: A review

This review addresses composite membranes used for wastewater treatment, focusing heavily on the anti-biofouling properties of such membranes. Biofouling caused by the development of a thick biofilm on the membrane surface is a major issue that reduces water permeance and reduces its lifetime. Biofilm formation and adhesion are mitigated by modifying membranes with two-dimensional or zero-dimensional carbon-based nanomaterials or their modified substituents. In particular, nanomaterials based on graphene, including graphene oxide and carbon quantum dots, are mainly used as nanofillers in the membrane. Functionalization of the nanofillers with various organic ligands or compositing the nanofiller with other materials, such as silver nanoparticles, enhances the bactericidal ability of composite membranes. Moreover, such membrane modifications reduce biofilm adhesion while increasing water permeance and salt/dye rejection. This review discusses the recent literature on developing graphene oxide-based and carbon quantum dot-based composite membranes for biofouling-resistant wastewater treatment.

Tailored design of nanofiltration membranes for water treatment based on synthesis-property-performance relationships

Tailored design of high-performance nanofiltration (NF) membranes is desirable because the requirements for membrane performance, particularly ion/salt rejection and selectivity, differ among the various applications of NF technology ranging from drinking water production to resource mining. However, this customization greatly relies on a comprehensive understanding of the influence of membrane fabrication methods and conditions on membrane properties and the relationships between the membrane structural and physicochemical properties and membrane performance. Since the inception of NF, much progress has been made in forming the foundation of tailored design of NF membranes and the underlying governing principles. This progress includes theories regarding NF mass transfer and solute rejection, further exploitation of the classical interfacial polymerization technique, and development of novel materials and membrane fabrication methods. In this critical review, we first summarize the progress made in controllable design of NF membrane properties in recent years from the perspective of optimizing interfacial polymerization techniques and adopting new manufacturing processes and materials. We then discuss the property-performance relationships based on solvent/solute mass transfer theories and mathematical models, and draw conclusions on membrane structural and physicochemical parameter regulation by modifying the fabrication process to improve membrane separation performance. Next, existing and potential applications of these NF membranes in water treatment processes are systematically discussed according to the different separation requirements. Finally, we point out the prospects and challenges of tailored design of NF membranes for water treatment applications. This review bridges the long-existing gaps between the pressing demand for suitable NF membranes from the industrial community and the surge of publications by the scientific community in recent years.

A Comprehensive Review of Polymeric Wastewater Purification Membranes

Synthetic membranes are currently employed for multiple separation applications in various industries. They may have been prepared from organic or inorganic materials. Present research majorly focuses on polymeric (i.e., organic) membranes because they show better flexibility, pore formation mechanism, and thermal and chemical stability, and demand less area for installation. Dendritic, carbon nanotube, graphene and graphene oxide, metal and metal oxide, zwitter-ionic, and zeolite-based membranes are among the most promised water treatment membranes. This paper critically reviews the ongoing developments to utilize nanocomposite membranes to purify water. Various membranes have been reported to study their resistance and fouling properties. A special focus is given towards multiple ways in which these nanocomposite membranes can be employed. Therefore, this review provides a platform to develop the awareness of current research and motivate its readers to make further progress for utilizing nanocomposite membranes in water purification.

Immobilization of Cu (II) via a graphene oxide-supported strategy for antibacterial reutilization with long-term efficacy

The past several decades have witnessed tremendous research to discover ways for controlling heavy metal pollution, but most of the strategies do not involve reuse of the captured heavy metals. Herein, we propose a graphene oxide -based strategy for the effective removal of Cu²⁺ ions from water, coupled with their reuse as an antibacterial agent. Using GO nanosheets as an adsorbent and nanosupport, the Cu²⁺ ions were effectively extracted from water (>99.9%) and reduced in situ to copper nanoparticles (Cu NPs) containing both crystalline Cu and Cu₂O. The as-captured Cu NPs showed efficient in vitro antibacterial ability against Escherichia coli, reducing the bacteria from 10⁹ to 10¹ CFU mL^-1 by using ¹ mg mL^-1 Cu NPs/GO NSs for 1 h. The minimum inhibitory concentration determined to be only 16 μg mL^-1. For practical applications, Cu recovered from wastewater could reduce bacteria by 8 log CFU in 1 h. The recovered Cu was still able to reduce the bacteria by 7 log CFU after 2 months of storage in an argon atmosphere. This strategy of extracting heavy metals and subsequently reutilizing to kill bacteria will be of great significance for environmental remediation and public healthcare.

Graphene-Based Antimicrobial Biomedical Surfaces

Biomedical application of graphene derivatives have been intensively studied in last decade. With the exceptional structural, thermal, electrical, and mechanical properties, these materials have attracted immense attention of biomedical scientists to utilize graphene derivatives in biomedical devices to improve their performance or to achieve desired functions. Surfaces of graphene derivatives including graphite, graphene, graphene oxide and reduce graphene oxide have been demonstrated to pave an excellent platform for antimicrobial behavior, enhanced biocompatibility, tissue engineering, biosensors and drug delivery. This review focuses on the recent advancement in the research of biomedical devices with the coatings or highly structured polymer nanocomposite surfaces of graphene derivatives for antimicrobial activity and sterile surfaces comprising an entirely new class of antibacterial materials. Overall, we aim to highlight on the potential of these materials, current understanding and knowledge gap in the antimicrobial behavior and biocompatibility to be utilized of their coatings to prevent the cross infections.

Copper-Modified Polymeric Membranes for Water Treatment: A Comprehensive Review

In the last decades, the incorporation of copper in polymeric membranes for water treatment has received greater attention, as an innovative potential solution against biofouling formation on membranes, as well as, by its ability to improve other relevant membrane properties. Copper has attractive characteristics: excellent antimicrobial activity, high natural abundance, low cost and the existence of multiple cost-effective synthesis routes for obtaining copper-based materials with tunable characteristics, which favor their incorporation into polymeric membranes. This study presents a comprehensive analysis of the progress made in the area regarding modified membranes for water treatment when incorporating copper. The notable use of copper materials (metallic and oxide nanoparticles, salts, composites, metal-polymer complexes, coordination polymers) for modifying microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), forward osmosis (FO) and reverse osmosis (RO) membranes have been identified. Antibacterial and anti-fouling effect, hydrophilicity increase, improvements of the water flux, the rejection of compounds capacity and structural membrane parameters and the reduction of concentration polarization phenomena are some outstanding properties that improved. Moreover, the study acknowledges different membrane modification approaches to incorporate copper, such as, the incorporation during the membrane synthesis process (immobilization in polymer and phase inversion) or its surface modification using physical (coating, layer by layer assembly and electrospinning) and chemical (grafting, one-pot chelating, co-deposition and mussel-inspired PDA) surface modification techniques. Thus, the advantages and limitations of these modifications and their methods with insights towards a possible industrial applicability are presented. Furthermore, when copper was incorporated into membrane matrices, the study identified relevant detrimental consequences with potential to be solved, such as formation of defects, pore block, and nanoparticles agglomeration during their fabrication. Among others, the low modification stability, the uncontrolled copper ion releasing or leaching of incorporated copper material are also identified concerns. Thus, this article offers modification strategies that allow an effective copper incorporation on these polymeric membranes and solve these hinders. The article finishes with some claims about scaling up the implementation process, including long-term performance under real conditions, feasibility of production at large scale, and assessment of environmental impact.

High-Throughput Zwitterion-Modified MoS2 Membranes: Preparation and Application in Dye Desalination

Although loose nanofiltration membranes have been extensively studied for dye desalination, high-throughput membranes with antifouling and antibacterial properties are still highly needed. In this study, a zwitterion-modified molybdenum disulfide (MoS₂) dual-layer loose nanofiltration membrane was prepared with the integration of antibacterial, antifouling, and high-flux properties. To be specific, MoS₂ nanosheets were loaded on a polyacrylonitrile ultrafiltration membrane through pressure-assisted self-assembly. Then, poly (sulfobetaine methacrylate) (PSBMA) was coated on the surface of the MoS₂ membrane via a simple polydopamine (PDA)-assisted one-step codeposition to prepare PSBMA/PDA/MoS₂ nanofiltration membranes. Elemental and morphological analyses confirmed the formation of the MoS₂ layer and PSBMA/PDA coating. In addition, the effect of the PSBMA amount and codeposition time on surface properties and membrane performances was investigated. Under optimum conditions, the as-prepared membrane showed excellent water permeance of 262 LMH/bar with good dye rejection (99.8% for methylene blue) and salt permeability, as well as excellent antifouling and antibacterial properties benefiting from the synergy of PSBMA/PDA coating layers and MoS₂ layers.

Bio-inspired co-deposited preparation of GO composite loose nanofiltration membrane for dye contaminated wastewater sustainable treatment

The fully separation of dye/salt through loose nanofiltration membranes is of great significance for the sustainable development paradigm of textile wastewater. However, the current loose nanofiltration membranes suffer low separation efficiency and complex preparation. Herein, by one-step co-deposition, we develop graphene oxide (GO) composite loose nanofiltration membranes with low negatively charged surface. Our membrane possesses unconventional high pure water permeation of 71.7 LMH/bar, 92.9 % rejection for Methyl blue (MB) and 98.8 % rejection for Congo red (CR). Benefiting from the large interlayer distance of GO nanosheets and low negatively charged surface, membrane achieves high dyes/salts separation with satisfactory permeation to salts (94.3 % of Na₂SO₄, 97.6 % of MgSO₄, 98.3 % of MgCl₂ and 99.0 % of NaCl). The CR/salt mixed solutions exhibit similar removal rates to their constituents' single dye or salt solutions (CR rejection is up to more than 97 % and the permeations of all salts are above 93 %). At the same time, binary dyes mixtures (Congo red and Methyl orange) can also be effectively separated. Furthermore, the membrane shows a relatively desirable antifouling property. The flux recovery still remains at 85.9 % after three cycling filtrations. This study provides a facile approach to prepare highly-efficient loose nanofiltration membranes for wastewater sustainable remediation.

Antibacterial rGO-CuO-Ag film with contact- and release-based inactivation properties

To reduce the high operational costs of water treatment because of membrane biofouling, next-generation materials are being developed to counteract microbial growth. These modern anti-biofouling strategies are based on new membrane materials or membrane surface modifications. In this study, antimicrobial films comprising rGO, rGO-CuO, rGO-Ag, and rGO-CuO-Ag were synthesized, evaluated, and tested for potential biofouling control using Pseudomonas aeruginosa PAO1 as the model bacterium. The combined rGO-CuO-Ag film displayed enhanced reduction (10-log reduction) in biofouling in comparison to the rGO film (control), followed by the rGO-Ag film (8-log reduction) and rGO-CuO film (0-log reduction). This demonstrated that the use of mixed antimicrobial agents is more effective in reducing biofouling than that of a single agent. The rGO-CuO-Ag film exhibited consistent, controlled, and moderate release of silver (Ag) ions. The release of Ag ions produced a long-lasting antimicrobial effect. These results underscore the potential applications of combined antimicrobial surface-based agents in practice and further research.

Graphene Oxide/Copper Nanoderivatives-Modified Chitosan/Hyaluronic Acid Dressings for Facilitating Wound Healing in Infected Full-Thickness Skin Defects

PURPOSE

Wound healing, especially of infected wounds, remains a clinical challenge in plastic surgery. This study aimed to manufacture a novel and multifunctional wound dressing by combining graphene oxide/copper nanocomposites (GO/Cu) with chitosan/hyaluronic acid, providing significant opportunities for the therapy of wound repair in wounds with a high risk of bacterial infection.

METHODS

In this study, GO/Cu-decorated chitosan/hyaluronic acid dressings (C/H/GO/Cu) were prepared using sodium trimetaphosphate (STMP) crosslinking and the vacuum freeze-drying method, and chitosan/hyaluronic acid dressings (C/H) and GO-incorporated chitosan/hyaluronic acid dressings (C/H/GO) served as controls. The surface characterization, in vitro degradation under various pH values, antimicrobial potential, cytocompatibility and in vivo therapeutic efficacy in a bacteria-infected full-thickness skin defect model were systematically evaluated.

RESULTS

Our experimental results indicated that the acidic environment facilitated the release of copper (CuNPs and Cu2+) from the dressings, and prepared C/H/GO/Cu dressings exhibited significant in vitro antimicrobial activities against the two tested bacterial strains (ATCC35984 and ATCC25923). All three dressings showed satisfactory cytocompatibility with mouse fibroblasts (NIH/3T3-L1). Moreover, remarkably accelerated wound healing was found in the C/H/GO/Cu group, with controlled inflammatory infiltration and improved angiogenesis in granulation tissues. In addition, no pathological damage was noted in the tissue structures of the tested organs (heart, lung, liver and kidney) in any of the four groups.

CONCLUSION

Collectively, GO/Cu-incorporated chitosan/hyaluronic acid dressings suggested a synergistic antimicrobial efficacy and acceptable biocompatibility both in vitro and in vivo, as well as a significantly accelerated healing process of bacteria-infected wounds. Thus, the multifunctional C/H/GO/Cu composite is expected to be a potential alternative for wound dressings, especially for the management of intractable wounds caused by bacterial infection.

Custom-Tailoring Loose Nanofiltration Membrane for Precise Biomolecule Fractionation: New Insight into Post-Treatment Mechanisms

Loose nanofiltration (NF) membranes with diverse selectivity can meet the great demands in various bioseparation applications. Thus, a facile strategy to tune the properties such as pore size, surface charge, and hydrophilicity of the NF membrane is required to produce tailor-made loose NF membranes without changing the existing production line. Herein, we systematically investigated the post-treatment of the nascent poly(piperazine amide) NF membranes using different reagents (organic acids, weak bases, organic solvents and ionic liquid (IL)). Various characterizations revealed that the skin/separation layer became looser and permeance was promoted with the decrease of salt rejection in varying degrees. It was found that the O/N ratio did not rigorously represent the cross-linking degree of the skin layer, because besides the hydrolysis of the residual acyl chloride impeding the amido bond formation, the breaking of existing amido bonds and the grafting of free trimesoyl chloride molecules on the nascent membranes could also increase the O/N ratio during post-treatments. Then three mechanisms including hydrolysis, swelling rearrangement and capping reaction effects were proposed to better understand the membrane properties variations. All these effects resulted in larger pore size of the NF membrane, and the hydrolysis/capping effect might increase negative charge and hydrophilicity on the membrane, while the swelling rearrangement could produce less defective skin structure. These three effects might be involved together during a single treatment. Finally, the NF membrane post-treated by N-hexane could efficiently separate antibiotics and NaCl with the highest permeate flux, whereas the one post-treated by ionic liquid outperformed others for the decoloration of cane molasses (much more efficient than NF270, DL, and NTR7450 membranes). The long-term operating stability of the post-treated membranes selected was also confirmed by a continuous crossflow filtration for 15 h with regular alkaline cleaning.