Hierarchically Assembled Graphene Oxide Composite Membrane with Self-Healing and High-Efficiency Water Purification Performance

Lanthanide ion-based metal-organic framework as an effective tri-mode nanoprobe for alcoholic content detection

A lanthanide ion-based metal-organic framework (Eu-TATAB nanorods) was designed and synthesized as an effective tri-mode nanoprobe for sensitive and portable detection of ethanol content in a water-ethanol mixture. The assay was based on the responsive properties of Eu-TATAB nanorods to ethanol stimulus and their adaptive encapsulation capability towards optically active lanthanides. With the addition of ethanol to the Eu-TATAB nanorods, the structure was destroyed, resulting in a decrease in luminescence, electrochemiluminescence, and ultraviolet-visible spectrophotometric signals by perturbing energy transfer in the Eu-TATAB nanorods. According to the degree of the decrease in three luminescence intensities, the ethanol content could be quantitatively detected. Based on this, the rapid detection of alcohol content in different types of spirits and alcoholic beverages was further realized. This method is simple, convenient, and sensitive, and has good application prospects and development potential.

Study of Low Temperature-Treated Aldolized Cellulose Nanocrystals for Enhancing Dye Separation and Self-Healing Properties of Graphene Oxide Membranes

Graphene oxide (GO) membranes with a 2D layered structure and nanoscale channels have great application prospects for dye wastewater purification. In this paper, ethylenediamine (EDA) was grafted onto the surface of GO nanosheets at 70 °C and aldolized cellulose nanocrystals (ICNC) were introduced to form EDA-ICNC hydrogel structures between the GO nanosheets by Schiff base reaction. The interlayer structure of the membrane was determined by adjusting the amount of ICNC added and the degree of aldolization, and the EGOICNC-24 membrane with the best performance was prepared. The water flux is not only 12 times higher than that of GO membrane but also has a good separation ability for dye molecules with a molecular weight around 300. Following the EDA-ICNC-24 hydrogel cross-linking process, the tensile strength of the EGOICNC-24 membrane exhibited a 173% increase relative to that of the GO membrane. Additionally, the dye rejection rate reached 97.16% after 130 h of dye separation. When the surface of the membrane was damaged, it was self-healed by regulating the repair temperature and adding a very small amount of ICNC to undergo a dynamic Schiff base reaction and a synergistic effect of hydrogen bonding.

Nanoarchitectonics Design Strategy of Metal-Organic Framework and Bio-Metal-Organic Framework Composites for Advanced Wastewater Treatment through Adsorption

Freshwater depletion is an alarm for finding an eco-friendly solution to treat wastewater for drinking and domestic applications. Though several methods like chlorination, filtration, and coagulation-sedimentation are conventionally employed for water treatment, these methods need to be improved as they are not environmentally friendly, rely on chemicals, and are ineffective for all kinds of pollutants. These problems can be addressed by employing an alternative solution that is effective for efficient water treatment and favors commercial aspects. Metal organic frameworks (MOFs), an emerging porous material, possess high stability, pore size tunability, greater surface area, and active sites. These MOFs can be tailored; thus, they can be customized according to the target pollutant. Hence, MOFs can be employed as adsorbents that effectively target different pollutants. Bio-MOFs are a kind of MOFs that are incorporated with biomolecules, which also possess properties of MOFs and are used as a nontoxic adsorbent. In this review, we elaborate on the interaction between MOFs and target pollutants, the role of linkers in the adsorption of contaminants, tailoring strategy that can be employed on MOFs and Bio-MOFs to target specific pollutants, and we also highlight the effect of environmental matrices on adsorption of pollutants by MOFs.

Introducing self-healing properties to polyethersulfone (PES) membrane via poly(vinyl alcohol)/ polyacrylic acid (PVA/PAA) surface coating

During membrane filtration, it is inevitable that a membrane will experience physical damage, leading to a loss of its integrity and a decrease in separation efficiency. Hence, the development of a water-responsive membrane capable of healing itself autonomously after physical damage is significantly important in the field of water filtration. Herein, a water-enabled self-healing composite polyethersulfone (PES) membrane was synthesized by coating the membrane surface using a mixed solution composed of poly (vinyl alcohol) and polyacrylic acid (PVA-PAA). The self-healing efficiency of the coated PES membrane was examined based on the changes in water flux at three stages which are pre-damaged, post-damaged, and post-healing. The self-healing process was initiated by the swelling of the water-responsive PVA and PAA, followed by the formation of reversible hydrogen bonds, completing the self-healing process. The coated PES membrane with three layers of PVA-PAA coatings (at 3:1 ratio) demonstrated high water flux and remarkable self-healing efficiency of up to 98.3%. The self-healing capability was evidenced by the morphology of the membrane observed via scanning electron microscope (SEM). The findings of this investigation present a novel architecture approach for fabricating self-healing membranes using PVA-PAA, in addition to other relevant parameters as reported.

A fire resistant MXene-based flexible film with excellent Joule heating and electromagnetic interference shielding performance

Flexible films with thermal management capability and efficient electromagnetic interference (EMI) shielding performance are highly needed for electronic devices. Moreover, it remains difficult to integrate fire safety performance into the multifunctional film. Thus, a facile multi-interfacial engineering strategy was proposed to prepare a fire resistant MXene-based flexible film with excellent Joule heating and EMI Shielding performance. Specifically, the neighboring and interlayer MXene sheets were respectively bridged by graphene oxide and carbon nanotube via multiple physical and chemical interactions, thus formed a optimized hierarchical microstructure. The resultant film possessesd outstanding Joule heating performance including wide electrical-to-thermal temperature and sensitive conversion ability. Simultaneously, the film exhibited high EMI shielding efficiency (99.97%). Most significantly, after being burned up to 60 min, the film still maintained its flexibility and multifunctional perfprmance benefiting from a large expanded protective layer. The excellent fire resistance and multi-functions endowed the film wide application prospects in advanced electronics.

A critical review on graphene oxide membrane for industrial wastewater treatment

An important way to promote the environmental industry's goal of carbon reduction is to promote the recycling of resources. Membrane separation technology has unique advantages in resource recovery and advanced treatment of industrial wastewater. However, the great promise of traditional organic membrane is hampered by challenges associated with organic solvent tolerance, lack of oxidation resistance, and serious membrane fouling control. Moreover, the high concentrations of organic matter and inorganic salts in the membrane filtration concentrate also hinder the wider application of the membrane separation technology. The emerging cost-effective graphene oxide (GO)-based membrane with excellent resistance to organic solvents and oxidants, more hydrophilicity, lower membrane fouling, better separation performance has been expected to contribute more in industrial wastewater treatment. Herein, we provide comprehensive insights into the preparation and characteristic of GO membranes, as well as current research status and problems related to its future application in industrial wastewater treatment. Finally, concluding remarks and future perspectives have been deduced and recommended for the GO membrane separation technology application for industrial wastewater treatment, which leads to realizing sustainable wastewater recycling and a nearly "zero discharge" water treatment process.

Cross-Linked and Doped Graphene Oxide Membranes with Excellent Antifouling Capacity for Rejection of Antibiotics and Salts

Graphene oxide (GO) membranes have suffered from the instability of water permeability and low rejection of pollutant separation. In this paper, a reasonable modification protocol for GO nanosheets at the molecular level was proposed. A molecular cross-linking strategy was adopted to regulate the interlayer spacing of GO nanosheets, and nanofiltration membranes with high water stability and excellent antifouling capacity were prepared, which could effectively reject antibiotics and salts. The GO₁-MPD_0.5 (the mass ratio of GO nanosheets to MPD is 1:0.5) and GO/GO₁-MPD_0.5-0.25 (the doping ratio of GO₁-MPD_0.5 is 25%) membranes had stable water permeability of 4.22 ± 0.06 and 3.65 ± 0.11 L m^-2 h^-1 bar^-1, and the rejection rates for ciprofloxacin (CIP) and ofloxacin (OFX) were 93.35 ± 3.62 and 95.48 ± 2.97 and 85.89 ± 6.52 and 88.21 ± 3.67%, respectively. Molecular dynamics simulations well explained the high water stability of membranes, and the cross-linked hydrophobic benzene ring played a role in the rejection of pollutant molecules. Moreover, the GO₁-MPD_0.5 membrane showed excellent antifouling capacity and the flux recovery ratio (FRR) was more than 98%. This paper provides a new idea for the design of nanofiltration membranes with high stability and good rejection permeability at the molecular level and provides a prospect for the application of nanofiltration membranes in practical water treatment and water purification.

Self-Healing Superwetting Surfaces, Their Fabrications, and Properties

The research on superwetting surfaces with a self-healing function against various damages has progressed rapidly in the recent decade. They are expected to be an effective approach to increasing the durability and application robustness of superwetting materials. Various methods and material systems have been developed to prepare self-healing superwetting surfaces, some of which mimic natural superwetting surfaces. However, they still face challenges, such as being workable only for specific damages, external stimulation to trigger the healing process, and poor self-healing ability in the water, marine, or biological systems. There is a lack of fundamental understanding as well. This article comprehensively reviews self-healing superwetting surfaces, including their fabrication strategies, essential rules for materials design, and self-healing properties. Self-healing triggered by different external stimuli is summarized. The potential applications of self-healing superwetting surfaces are highlighted. This article consists of four main sections: (1) the functional surfaces with various superwetting properties, (2) natural self-healing superwetting surfaces (i.e., plants, insects, and creatures) and their healing mechanism, (3) recent research development in various self-healing superwetting surfaces, their preparation, wetting properties in the air or liquid media, and healing mechanism, and (4) the prospects including existing challenges, our views and potential solutions to the challenges, and future research directions.

Graphene-Based Metal-Organic Framework Hybrids for Applications in Catalysis, Environmental, and Energy Technologies

Current energy and environmental challenges demand the development and design of multifunctional porous materials with tunable properties for catalysis, water purification, and energy conversion and storage. Because of their amenability to de novo reticular chemistry, metal-organic frameworks (MOFs) have become key materials in this area. However, their usefulness is often limited by low chemical stability, conductivity and inappropriate pore sizes. Conductive two-dimensional (2D) materials with robust structural skeletons and/or functionalized surfaces can form stabilizing interactions with MOF components, enabling the fabrication of MOF nanocomposites with tunable pore characteristics. Graphene and its functional derivatives are the largest class of 2D materials and possess remarkable compositional versatility, structural diversity, and controllable surface chemistry. Here, we critically review current knowledge concerning the growth, structure, and properties of graphene derivatives, MOFs, and their graphene@MOF composites as well as the associated structure-property-performance relationships. Synthetic strategies for preparing graphene@MOF composites and tuning their properties are also comprehensively reviewed together with their applications in gas storage/separation, water purification, catalysis (organo-, electro-, and photocatalysis), and electrochemical energy storage and conversion. Current challenges in the development of graphene@MOF hybrids and their practical applications are addressed, revealing areas for future investigation. We hope that this review will inspire further exploration of new graphene@MOF hybrids for energy, electronic, biomedical, and photocatalysis applications as well as studies on previously unreported properties of known hybrids to reveal potential "diamonds in the rough".

MOF-assisted antifouling material: application in rapid determination of TB gene in whole-serum specimens

Biofouling is a nuisance in the practical applications of biosensors, which seriously affects the reliability and accuracy of detection. The utilization of antifouling interface materials is a promising option for mitigating biofouling. Only highly accumulated antifouling polymeric surfaces tend to offer "zero" nonspecific protein adsorption. Herein, superior antifouling coatings based on chondroitin sulfate (CS) were prepared by the NH₂-MIL-53 (Al) assisted strategy. This is a novel design to improve the antifouling property of material by taking advantage of the high specific surface area of the three-dimensional MOF to increase the accumulation degree of antifouling functional groups per unit area. And the related chemical technology is simple and easy to operate. As expected, this novel CS-loaded MOF demonstrated an excellent antifouling performance in various biological samples, even in 100% goat serum. Only 8.48% changes of differential pulse voltammetry (DPV) were found. Furthermore, this antifouling interface material is successfully applied for the specific detection of the tuberculosis (TB) gene in undiluted biofluids. This developed TB biosensor showed a high analytical performance with a wide linear range (1.00 × 10^-16 M to 1.00 × 10^-11 M) and a low detection limit, indicating that it may open new avenues for direct biosensing of disease markers for clinical samples.

Recent advances in chitosan-based layer-by-layer biomaterials and their biomedical applications

In recent years, chitosan-based biomaterials have been continually and extensively researched by using layer-by-layer (LBL) assembly, due to their potentials in biomedicine. Various chitosan-based LBL materials have been newly developed and applied in different areas along with the development of technologies. This work reviews the recent advances of chitosan-based biomaterials produced by LBL assembly. Driving forces of LBL, for example electrostatic interactions, hydrogen bond as well as Schiff base linkage have been discussed. Various forms of chitosan-based LBL materials such as films/coatings, capsules and fibers have been reviewed. The applications of these biomaterials in the field of antimicrobial applications, drug delivery, wound dressings and tissue engineering have been comprehensively reviewed.

Dual-functional calcium alginate hydrogel beads for disinfection control and removal of dyes in water

For the decontamination of both pathogenic microorganism and toxic dye from wastewater, new type of materials should be exploited to fabricate more cost-effective, eco-friendly biosorbent. Herein, a promising hydrogel beads based on the incorporation of nano‑silver/diatomite into calcium alginate (named as Ag-DE@CAH) was designed to disinfect water and remove methylene blue (MB). Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM), etc. were utilized for characterization analysis. Compared with nano‑silver/diatomite (Ag-DE), the novel Ag-DE@CAH beads displayed a better sustained release profile for Ag⁺, and it noteworthy that the concentration of Ag⁺ in aqueous media is below the limit of the World Health Organization (WHO) standard (100 ppb) for a 30-days release experiment. It was found that Ag-DE@CAH beads exhibited better disinfection ability towards Escherichia coli (E. coli) than Staphylococcus aureus (S. aureus), and the maximum adsorption capacities of Ag-DE@CAH for MB was 128.21 mg/g. In addition, the as-prepared Ag-DE@CAH beads showed superior and reusable performance in the process of adsorption experiments for MB. Overall, the study indicates that the materials with both excellent disinfection and adsorption properties have potential application prospects for water purification.

Graphene-Based Materials Immobilized within Chitosan: Applications as Adsorbents for the Removal of Aquatic Pollutants

Graphene and its derivatives, especially graphene oxide (GO), are attracting considerable interest in the fabrication of new adsorbents that have the potential to remove various pollutants that have escaped into the aquatic environment. Herein, the development of GO/chitosan (GO/CS) composites as adsorbent materials is described and reviewed. This combination is interesting as the addition of graphene to chitosan enhances its mechanical properties, while the chitosan hydrogel serves as an immobilization matrix for graphene. Following a brief description of both graphene and chitosan as independent adsorbent materials, the emerging GO/CS composites are introduced. The additional materials that have been added to the GO/CS composites, including magnetic iron oxides, chelating agents, cyclodextrins, additional adsorbents and polymeric blends, are then described and discussed. The performance of these materials in the removal of heavy metal ions, dyes and other organic molecules are discussed followed by the introduction of strategies employed in the regeneration of the GO/CS adsorbents. It is clear that, while some challenges exist, including cost, regeneration and selectivity in the adsorption process, the GO/CS composites are emerging as promising adsorbent materials.

Fabrication of flexible composite film based on xylan from pulping process for packaging application

To realize the application of xylan based film in food and drug packaging, the poor mechanical property and film-forming property of xylan based film must be overcome. Herein, a good oxygen barrier composite film with desired mechanical properties was prepared based on carboxymethly xylan (CMX), chitosan (CS), and graphene oxide (GO). The results of scanning electron microscope revealed the composite film had a dense and continuous structure, which will endow the composite film with excellent mechanical property. As expected, the composite film with the 0.5% mass fraction of GO exhibited best mechanical property, among which the tensile stress, tensile strain, and Young's modulus of the composite film reached 50.81 MPa, 47.61%, and 1.39 GPa, respectively. The oxygen barrier properties of the composite films significantly increased with the addition of graphene oxide due to the dense, stacked multilayer structure. In addition, these composite films exhibited good antibacterial properties. Therefore, these films show great promise in the field of food packaging and wound dressing due to their excellent mechanical, oxygen barrier and antibacterial properties.

Stable Forward Osmosis Nanocomposite Membrane Doped with Sulfonated Graphene Oxide@Metal-Organic Frameworks for Heavy Metal Removal

A sulfonated graphene oxide@metal-organic framework-modified forward osmosis nanocomposite (SGO@UiO-66-TFN) membrane was developed to improve stability and heavy metal removal performance. An in situ growth method was applied to uniformly distribute UiO-66 nanomaterial with a frame structure on SGO nanosheets to form SGO@UiO-66 composite nanomaterial. This nanomaterial was then added to a polyamide layer using interfacial polymerization. The cross-linking between SGO@UiO-66 and m-phenylenediamine improved the stability of the nanomaterial in the membrane. Additionally, the water permeability was improved because of additional water channels introduced by SGO@UiO-66. SGO, with its lamellar structure, and UiO-66, with its frame structure, made the diffusion path of the solute more circuitous, which improved the heavy metal removal and salt rejection performances. Moreover, the hydrophilic layer of the SGO@UiO-66-TFN membrane could block contaminants and loosen the structure of the pollution layer, ensuring that the membrane maintained a high removal rate. The water flux and reverse solute flux of the SGO@UiO-66-TFN membrane reached 14.77 LMH and 2.95 gMH, and compared with the thin-film composite membrane, these values were increased by 41 and 64%, respectively. The membrane also demonstrated a good heavy metal ion removal performance. In 2 h, the heavy metal ion removal rate (2000 ppm Cu²⁺ and Pb²⁺) was greater than 99.4%, and in 10 h the removal rate was greater than 97.5%.

Synthesis of Graphene-Based Biopolymer TiO2 Electrodes Using Pyrolytic Direct Deposition Method and its Catalytic Performance

The traditional methods used to synthesize graphene layers over semiconductors are chemical-based methods. In the present investigation, a novel photoelectroactive electrode was synthesized using a chitosan biopolymer without the usage of chemicals. A chitosan-biopolymer layer over the surface of TiO2 was generated by electrodeposition. Furthermore, the pyrolysis method was used for the conversion of a biopolymer into graphene layers. The catalytic activity of the fabricated electrodes was investigated by the photo-electro-Fenton (PEF) process to oxidize chloramphenicol and nadolol pharmaceutical drugs in wastewater, remove metals (scandium, neodymium, and arsenic) and degrade real municipal wastewater. The PEF operational parameters (pH, voltage, reaction time, and Fenton catalytic dose) were optimized for the overall degradation of chloramphenicol and nadolol pharmaceutical drugs in wastewater. It was observed that at the optimum process operational parameters it took 40 min to degrade chloramphenicol and nadolol pharmaceutical drugs in wastewater. It was proved that biopolymer-based photoelectroactive novel electrodes render good catalytic activity. Furthermore, the reusability study of fabricated electrodes showed excellent storage and self-healing properties.

Recent Development in Composite Membranes for Flow Batteries

Flow batteries (FBs) are one of the most attractive candidates for stationary energy storage and vital in realizing the wide application of renewable energies. Membranes play an important role in isolating redox couples while transporting ions to close the internal electrical circuit. Therefore, membranes with high selectivity and conductivity are highly important. Among different membranes, a composite membrane with independent design of support layer and thin selective top layer becomes one of the most promising candidates to break the trade-off between selectivity and conductivity. In this Review, recent studies on composite membranes for FBs and the principles of membrane design in different systems are discussed and summarized. Finally, the future direction on membrane design for different FBs is presented, which will provide an extensive, comprehensive reference to design and construct high-performance composite membranes for FBs.