Preparation of glycine mediated graphene oxide/g-C3N4 lamellar membranes for nanofiltration

3D Printing MXene-Based Electrodes for Supercapacitors

3D printing, as an advanced and promising strategy for processing electrode for energy storage devices, such as supercapacitors and batteries, has garnered considerable interest in recent decades. The interest in 3D printed electrodes stems from its exceptional performance and manufacturing features, including customized sizes and shapes and the layer-by-layer processing principle, etc., especially integrating with MXene which allows the manufacturing of electrodes from different raw materials and possessing desired electrochemical properties. Herculean challenges, such as material compatibility of the printing inks, nondurable interfacial or bulk mechanical strength of the printed electrodes, and sometimes the low capacitance, lead to inferior electrochemical performance and hinder the practical applications of this promising technology. In this review, we firstly summarize the representative 3D printing methods, then, review the MXene-based 3D printing electrodes made from different materials, and last, provide electrochemical performance of 3D printing MXene-based electrodes for supercapacitors. Furthermore, based on a summary on the recent progress, an outlook on these promising electrodes for sustainable energy devices is provided. We anticipate that this review could provide some insights into overcoming the challenges and achieving more remarkable electrochemical performance of 3D printing supercapacitor electrodes and offer perspectives in the future for emerging energy devices.

Defect Engineering in GO Membranes - Tailoring Size and Oxidation Degree of Nanosheet for Enhanced Pore Channels

Graphene Oxide (GO) membrane has been extensively applied in the field of water purification and membrane separation processes. While the solute molecule transport in GO membranes encompasses interlayer channels, edge defects, and in-plane crack-like holes, the significance of edge defects or crack-like pores in ultrathin membranes is often overlooked. In our study, we focused on the construction of short-range channel GO membranes with varied defect structures by modulating the transverse size of the porous nanosheets. GO nanosheets with different sizes were procured through high-energy γ-irradiation combined with centrifugation. Notably, the large-sized porous GO nanosheets (L-pGO) exhibit a consistent structure, and numerous in-plane defects. In contrast, the smaller counterparts (S-pGO) present a fewer in-plane defects. The performance metrics revealed that L-pGO exhibited a water flux of 849.25 L m-2  h-1  bar-1 , while S-pGO demonstrated nearly 100 % dye rejection capacity. These findings underscore the potential of defect engineering as a powerful strategy to enhance the efficiency of two-dimensional membranes.

Synthesis and applications of graphitic carbon nitride (g-C3N4) based membranes for wastewater treatment: A critical review

Semiconducting membrane combined with nanomaterials is an auspicious combination that may successfully eliminate diverse waste products from water while consuming little energy and reducing pollution. Creating an inexpensive, steady, flexible, and diversified business material for membrane production is a critical challenge in membrane technology development. Because of its unusual structure and high catalytic activity, graphitic carbon nitride (g-C3N4) has come out as a viable material for membranes. Furthermore, their great durability, high permanency under challenging environments, and long-term use without decrease in flux are significant advantages. The advanced material techniques used to manage the molecular assembly of g-C3N4 for separation membrane were detailed in this review work. The progress in using g-C3N4-based membranes for water treatment has been detailed in this presentation. The review delivers an updated description of g-C3N4 based membranes and their separation functions and new ideas for future enhancements/adjustments to address their weaknesses in real-world situations. Finally, the ongoing problems and promising future research directions for g-C3N4-based membranes are discussed.

Enhancing the Dye-Rejection Efficiencies and Stability of Graphene Oxide-Based Nanofiltration Membranes via Divalent Cation Intercalation and Mild Reduction

Laminar graphene oxide (GO) membranes have demonstrated great potential as next-generation water-treatment membranes because of their outstanding performance and physicochemical properties. However, solute rejection and stability deterioration in aqueous solutions, which are caused by enlarged nanochannels due to hydration and swelling, are regarded as serious issues in the use of GO membranes. In this study, we attempt to use the crosslinking of divalent cations to improve resistance against swelling in partially reduced GO membranes. The partially reduced GO membranes intercalated by divalent cations (i.e., Mg2+) exhibited improved dye-rejection efficiencies of up to 98.40%, 98.88%, and 86.41% for methyl orange, methylene blue, and rhodamine B, respectively. In addition, it was confirmed that divalent cation crosslinking and partial reduction could strengthen mechanical stability during testing under harsh aqueous conditions (i.e., strong sonication).

Recent developments in architecturing the g-C3N4 based nanostructured photocatalysts: Synthesis, modifications and applications in water treatment

Water pollution is becoming an inevitable problem in today's world. Tons and tons of wastewater with hazardous pollutants are getting discharged into the clean water bodies every day. In this regard, photocatalytic environmental remediation using nanotechnology such as the use of organic, metal and non-metal based semiconductor photocatalysts for photodegradation of pollutants has gained enormous attention in the past few decades. This review is focused particularly on graphitic carbon nitride (g-C₃N₄) which is a cheap, metal-free, polymeric photoactive compound and it is used as a potential photocatalyst in wastewater treatment. Though, pristine g-C₃N₄ is a good photocatalyst, it has certain drawbacks such as poor visible light absorption capacity, quicker recombination of photoelectrons and holes, delayed mass and charge transfer, etc. As a result, the pristine g-C₃N₄ catalyst is modified into novel 0D, 1D, 2D and 3D morphologies such as nano-quantum dots, nanorods, nanotubes, nanowires, nanosheets, nanoflakes, nanospheres, nanoshells, etc. It was also tailored into novel composites along with various compounds through doping, metal deposition, heterojunction formation, etc., to enhance the photocatalytic property of pure g-C₃N₄. The modified catalysts showed promising photocatalytic performance such as degradation of majority of pollutants in the environment. It also showed excellent results in the removal or reduction of heavy metals. This review provides a detailed record of g-C₃N₄ and its diverse photocatalytic applications in the past years and it provides knowledge for the development of such similar novel compounds in the future.

Biocompatible 2D Cu-TCPP Nanosheets Derived from Cu2O Nanocubes as Multifunctional Nanoplatforms for Combined Anticancer Therapy

Two-dimensional (2D) metal-organic frameworks (MOFs) could serve as multifunctional nanoplatforms to load small-molecule drugs and enzyme-mimicking nanoparticles (NPs) with a high efficiency for combined cancer therapy. Herein, we have prepared novel 2D Cu-tetrakis (4-carboxyphenyl) porphyrin (TCPP) nanosheets with an average thickness of 1.2 ± 0.1 nm using Cu₂O nanocubes (50 nm) as a template and solid copper ion supplier. Cu₂O nanocubes can be consumed and hybridized with the obtained Cu-TCPP, depending on the molar ratio of Cu₂O and TCPP linker. The resultant Cu₂O/Cu-TCPP could serve as nanoplatforms for co-loading of Pt and Au NPs to construct multifunctional Cu₂O/Cu-TCPP/(Pt-Au) nanomedicines, which showed a superior anticancer effect via multiple therapeutic modes. For instance, Cu(II)-TCPP can produce ¹O₂ in the presence of acidic H₂O₂ by the Russell mechanism and the intrinsic Cu(I) ions (derived from the residual Cu₂O) could mediate a Fenton-like reaction in tumorous tissues to generate toxic hydroxyl radicals (•OH). Moreover, the loaded Pt NPs with catalase (CAT)-mimic activity could decompose hydrogen peroxide (H₂O₂) into O₂ within the tumor cells, increasing the local O₂ concentration, modulating the tumorous hypoxia atmosphere, and promoting the O₂-dependent glucose oxidation reaction. Furthermore, Au NPs with glucose oxidase (GOx)-mimic activity could accelerate the consumption of glucose and cut nutrient supply to induce starvation therapy. Consequently, our designed 2D MOF-based therapeutic nanomedicines would be a promising candidate for future smart and combined cancer therapy.

High-Performance Boron Nitride Based Membranes for Water Purification

In recent years, nanotechnology-based approaches have resulted in the development of new alternative sustainable technologies for water purification. Two-dimensional (2D) nanomaterials are an emerging class of materials for nanofiltration membranes. In this work, we report the production, characterisation and testing of a promising nanofiltration membrane made from water-exfoliated boron nitride (BN) 2D nanosheets. The membranes have been tested for water purification and removal of typical water-soluble dyes such as methyl orange, methylene blue and Evans blue, with the water-exfoliated BN membranes achieving retention values close to 100%. In addition, we compared the performance of membranes made from water-exfoliated BN with those produced from BN using sonication-assisted liquid exfoliation in selected organic solvents such as 2-propanol and N-methyl-2-pyrrolidone. It was found that membranes from the water-exfoliated BN showed superior performance. We believe this research opens up a unique opportunity for the development of new high-performance environmentally friendly membranes for nanofiltration and new sustainable separation technologies.

Novel Perylene-3, 4, 9, 10-tetracarboxylic dianhydride modified Zr-MOFs/Graphene oxide membrane for dye wastewater treatment

A new type of composite membrane was prepared through the vacuum filtration self-assembly, in which, graphene oxide (GO) was the basic material, and the horizontal insertion material is product of perylene-3, 4, 9, 10-tetracarboxylic dianhydride (PTCDA) and UiO-66-NH₂ (PTCDA-UiO-66-NH₂). The leading role of Π-Π conjugate, auxiliary effect of hydrogen bonding during membrane preparation have been confirmed through Fourier transform infrared spectroscopy (FTIR), UV-visible spectrophotometer, Raman spectroscopy, and X-ray diffraction (XRD). The prepared GO@PTCDA-UiO-66-NH₂ membrane had new nodular structure compared to GO membrane by scanning electron microscopy (SEM) and atomic force microscopy (AFM), which promoted the water transport. In addition, the insertion of PTCDA-UiO-66-NH₂ narrowed the actual filtration spacing between GO sheets, and PTCDA-UiO-66-NH₂ could also adsorbed dye laterally. Experiments showed that the permeance of GO@PTCDA-UiO-66-NH₂ membrane was 1.7 times of GO membrane, and the removal of methyl blue, congo red, crystal violet and disperse black 9 was close to 100%. Under extreme pH, high salt concentration and multiple recycling, its separation ability was still excellent. The GO@PTCDA-UiO-66-NH₂ membrane constituted a unique synergistic structure of vertical-screening and horizontal-adsorption, which successfully overcame the trade-off effect and obtained excellent stability of structure and performance. Therefore, GO@PTCDA-UiO-66-NH₂ membrane had great potential in practical applications.

Semiconducting graphitic carbon nitride integrated membranes for sustainable production of clean water: A review

Semiconducting membranes integrated with nanomaterials have placed themselves in new emerging researches tremendously for seawater desalination, oil-water separation, disinfection, removal of inorganic as well as organic pollutants. Howbeit, only nanoparticles unified membranes show quite a lot lags in their performance, although some of these particles associated with the demerits of high cost. In contrast, graphitic carbon nitride incorporated membranes offered improved aforementioned properties corresponding to absolute essential qualities such as cost-effective, environmentally friendly, easy-to-operate, green manufacturing, anti-fouling, and low energy consumption. Moreover, their high mechanical strength, high stability against harsh environment and long-term utilization without flux reduction are strong plus. Even though there are some undeniable downsides of these membranes in real world applications as bulk synthesis, consistent dispersion of graphitic carbon nitride, low photocatalytic efficiency etc. Accordingly, in the present article, these frailties of the membranes having graphitic carbon nitride as a filler and their respective synthesis procedures and properties are discussed. A comprehensive analysis over the application of semiconducting graphitic carbon nitride incorporated membranes with and without special surface modification; and exploration of the future challenges and difficulties associated to these membranes are also reviewed. Consequently, the current article provides brief overview about graphitic carbon nitride integrated composite membranes as well as their applications, and it finished up with new thoughts of further improvements/modifications to overcome their shortcomings in actual environmental conditions.

A review on graphitic carbon nitride (g-C3N4) based hybrid membranes for water and wastewater treatment

Graphitic carbon nitride (g-C₃N₄) has gained enormous attention for water and wastewater treatment. Compared with g-C₃N₄ nanopowders, g-C₃N₄ based hybrid membranes have demonstrated great potential for its superior practicability. This review outlines the preparation and characterization of g-C₃N₄ based hybrid membranes and presents their representative applications in water and wastewater treatment (e.g., removal of organic dyes, phenolic compounds, pharmaceuticals, salt ions, heavy metals, and oils). Meanwhile, g-C₃N₄ based films for the removal of contaminants through photocatalytic degradation is also summarized. In addition, the corresponding mechanisms and relevant findings are discussed. Finally, the challenges and research needs in the future and application of g-C₃N₄ based hybrid membranes are highlighted.

Microscopically tuning the graphene oxide framework for membrane separations: a review

Membrane-based separations have been widely applied in gas, water and organic solvent purifications to reduce energy consumption and minimize environmental pollution. In recent years, graphene oxide (GO) membranes have attracted increasing attention due to their self-assembly ability and excellent stability. In this review, publications within the last 3 years on microscopically tuning the GO framework are summarized and reviewed. Various materials, including organic molecules, polymers, inorganic particles, ions and 2D materials, have been deployed to intercalate with GO nanosheets. Due to the varied interlayer spacing and packing structure, the developed GO composites exhibit enhanced stabilities and separation performances. In addition, designing horizontal GO membranes and functionalizing GO nanosheets have also been reported to improve the performance. This review sheds light on the techniques to microscopically tune the GO framework and the resulting macroscopic changes in membrane properties and performances.

Analysis of Mg2+/Li+ separation mechanism by charged nanofiltration membranes: visual simulation

The mechanism of the nanofiltration (NF) membrane separation of Mg²⁺ and Li⁺ needs to be further investigated, but some commonly used model theories are abstract, which makes them difficult to understand. More importantly, the relationship between the membrane charge and separation performance of Mg²⁺ and Li⁺ cannot be quantitatively analyzed. It is worth studying these challenges and providing a performance boost for Mg²⁺/Li⁺ filtration applications of NF membranes. Here, various NF membranes, with the membrane volumetric charge density increasing from -4.69 to 7.02 mol · m^-3, were fabricated via interfacial polymerization. For these membranes, the separation factor S _Mg,Li was decreased from 0.41 to 0.20. Importantly, the visual simulation results were consistent with the experimental results as a whole. The separation factor S _Mg,Li decreased with the increase of volumetric charge density, and the minimum separation factor S _Mg,Li of the NF membranes was 0.20 (experiment) and 0.17 (simulation), respectively. This meant that the performance of the positively charged NF membrane was not fully developed. Furthermore, we analyzed the relationship between the membrane charge and separation performance, and visualized the simulation of the NF membrane filtration and separation.

Emerging Chemical Functionalization of g-C3N4: Covalent/Noncovalent Modifications and Applications

Atomically 2D thin-layered structures, such as graphene nanosheets, graphitic carbon nitride nanosheets (g-C₃N₄), hexagonal boron nitride, and transition metal dichalcogenides are emerging as fascinating materials for a good array of domains owing to their rare physicochemical characteristics. In particular, graphitic carbon nitride has turned into a hot subject in the scientific community due to numerous qualities such as simple preparation, electrochemical properties, high adsorption capacity, good photochemical properties, thermal stability, and acid-alkali chemical resistance, etc. Basically, g-C₃N₄ is considered as a polymeric material consisting of N and C atoms forming a tri-s-triazine network connected by planar amino groups. In comparison with most C-based materials, g-C₃N₄ possesses electron-rich characteristics, basic moieties, and hydrogen-bonding groups owing to the presence of hydrogen and nitrogen atoms; therefore, it is taken into account as an interesting nominee to further complement carbon in applications of functional materials. Nevertheless, g-C₃N₄ has some intrinsic limitations and drawbacks mainly related to a relatively poor specific surface area, rapid charge recombination, a limited light absorption range, and a poor dispersibility in both aqueous and organic mediums. To overcome these shortcomings, numerous chemical modification approaches have been conducted with the aim of expanding the range of application of g-C₃N₄ and enhancing its properties. In the current review, the comprehensive survey is conducted on g-C₃N₄ chemical functionalization strategies including covalent and noncovalent approaches. Covalent approaches consist of establishing covalent linkage between the g-C₃N₄ structure and the chemical modifier such as oxidation/carboxylation, amidation, polymer grafting, etc., whereas the noncovalent approaches mainly consist of physical bonding and intermolecular interaction such as van der Waals interactions, electrostatic interactions, π-π interactions, and so on. Furthermore, the preparation, characterization, and diverse applications of functionalized g-C₃N₄ in various domains are described and recapped. We believe that this work will inspire scientists and readers to conduct research with the aim of exploring other functionalization strategies for this material in numerous applications.