Dispersion Of Nanosheets Research Articles

Improved tribological properties of MXene nanosheet filler-modified PPO composites

MXenes, a class of two-dimensional (2D) nanomaterials, exhibit exceptional properties such as outstanding mechanical and thermal stability, along with diverse surface characteristics, making them highly promising in the tribology. However, their tendency to aggregate within the polymeric matrix adversely affects the tribological performance of the polymer. In this study, glass fiber (GF) surfaces were modified with polydopamine (PDA), allowing smaller MXene nanosheets to adhere to the GF surface, whereas the larger MXene nanosheets were dispersed throughout the matrix. This approach effectively enhanced the dispersion of MXene nanosheets in the polymeric matrix, facilitating the preparation of polyphenylene oxide (PPO)/MXene composite materials. Compared with the pure PPO sample, the results showed that the average friction coefficient and wear rate of the PPO/MXene composites were reduced by 46.25% and 98.34%, respectively, due to the distinct roles of different MXene nanosheet sizes in the polymeric matrix. Furthermore, a uniform lubricating film was formed during the friction of the polymer composite, enhancing its tribological performance. This study proposes a novel design strategy to enhance MXene nanosheet dispersion and optimize their lubricating properties.

Inclusion of 2D nanosheets on ZnSb matrix as a unique approach to improve its thermoelectric performance

Enhancing the thermoelectric performance has been made possible by the strategy of introducing an additional phase to the thermoelectric (TE) material. ZnSb: MoS2 nanocomposites are successfully prepared using the solid-state method and sintering. Structural and morphology analysis confirms the inclusion of MoS2 in the ZnSb matrix. The phonon scattering is greatly improved in nanocomposites with newly designed ZnSb: MoS2 interfaces without impairing electron transport. Homogeneous dispersion of MoS2 nanosheets in the ZnSb matrix modulates the carrier effective mass, which is aided by a considerably greater interfacial barrier. The energy filtering effect leads to a significantly higher Seebeck coefficient with strongly reduced phonon conductivity. The addition of MoS2 nanosheets improves the TE power factor (PF) of ZnSb over the temperature of 300 K–673 K. For the ZnSb: MoS2 nanocomposite with 10 wt% of MoS2 achieves a maximum PF of 419.67 μW/mK2 at 673 K, a value that is much greater than pristine ZnSb. It has been shown that zT can be significantly improved by enhancing power factor values and reducing thermal conductivity. A high value of 0.65 is achieved at 673 K for ZnSb:15 % MoS2, which is higher than that for pristine ZnSb. This study lays the path for enhancing the thermoelectric efficiency of p-type ZnSb using interfacial additive of 2D MoS2 nanosheets.

Co-sorption of arsenic and fluoride using the hierarchical Mg-La-Fe nanosheets derived from layered double oxides

Considering the prevalent natural occurrence of arsenic and fluoride with a higher concentration gradient in groundwater, in this study, a novel MgLaFe layered double oxide material in the form of highly dispersed curly nanosheets (MLF-NS) was prepared using an urea hydrothermal method and low-temperature hydrogen peroxide exfoliation, applying to purity the contaminants of arsenic and fluoride. The prepared MLF-NS possesses exceptional co-sorption properties for As(III), As(V), and F− and the maximum co-sorption capacities (Qm) of As(III), As(V), and F− reach 36.95 mg g−1, 98.70 mg g−1, and 387.68 mg g−1, respectively, which is superior to those of most similar adsorbents. MLF-NS also exhibits excellent stability and reusability which can effectively regenerate and preserve their high adsorption capacity after four adsorption–desorption cycles. The mechanism investigation reveals the expansion of the interlayers due to the adsorbed arsenic ions, combining with the synergistic effect of motherboard cation coordination and exchanging with anions in the interlayer, plays a crucial role in enhancing the adsorption for both arsenic and fluoride. Meanwhile, the well-dispersed MLF-NS overcome the aggregation disadvantage, and thus exposes more adsorption sites to improve the co-removal efficiency of As(III), As(V), and F−. The collaborative analysis of mean adsorption free energy, FT-IR, AFM, XPS, adsorption energy, and CDD support the findings. Overall, the unique properties of MLF-NS make it a promising solution for effective removal of As(III), As(V), and F− in wastewater treatment.

Molten salt-assisted controlled synthesis of two-dimensional molybdenum carbide

The present investigation examines the carbothermal reduction synthesis of two-dimensional molybdenum carbide (2D Mo2C) using sodium carbonate (Na2CO3) as a molten salt diffusion promoter and sodium sulfide (Na2S) as a solid-state intercalation agent. Raw molybdenum disulfide (MoS2) powder undergoes carbothermal reduction facilitated by activated carbon and Na2CO3 above 800 °C to produce 2D Mo2C layers intercalated by Na2S. The diffusion of Na2S can be enhanced by the fluidity of molten salt Na2CO3, leading to the expansion of the Mo2C layer spacing to 29 nm under the influence of the temperature field. Na2S intercalation prevents layer shrinkage during cooling while molten Na2CO3 directs 2D growth, yielding 10 nm-thick sheets. The product maintains hexagonal β-Mo2C structure up to 950 °C with microflowers of accordion-shaped nanosheets. Ultrasonication exfoliates the weakly bound Mo2C layers into uniform, freely suspended flakes around 10–100 nm in lateral size. This work demonstrates the tuning of 2D Mo2C morphology in high-temperature reactions by utilizing molten salts. The principal results are the synthesis of micrometer-sized Mo2C sheets with controlled nanoscale thickness and uniform nanosheet dispersions, enabled by molten salt-directed diffusion of intercalated species. The major conclusion drawn is that solid-liquid synergistic diffusion can guide precision synthesis of layered nanomaterials.

An efficient Au/ZnO catalyst for the photocatalytic conversion of methane to formaldehyde

The photocatalytic oxidation of methane to value-added chemical products under mild conditions is crucial for resource utilization and environmental protection. However, inefficient generation of reactive oxygen species partially limits methane activation. To tackle this issue, we have developed highly dispersed Au-modified ZnO nanosheets through photo-deposition method for the photocatalytic oxidation of methane to formaldehyde. The optimized Au0.1/ZnO catalyst (0.1 wt% Au on ZnO) achieves a HCHO yield of 19.14 μmol h−1 with a selectivity of 87.94 %. Electron paramagnetic resonance, Raman, X-ray photoelectron spectroscopy and density functional theory show that Au enhances the concentration of oxygen vacancies (OVs) in ZnO. This enhancement is attributed to a strong interaction between Au and ZnO, which facilitates the transfer of electrons from the ZnO surface to Au. Under irradiation, Au and OVs function as hole and electron acceptors, respectively. This interaction promotes carrier separation, reduces charge recombination, enhances oxygen adsorption, and effectively generates reactive oxygen species, such as ·OH. Subsequently, CH4 is oxidized to ·CH3 by holes from Au. Concurrently, O2 is reduced by electron from OVs, following the pathways O2 → OOH→H2O2 → ·OH. The rapid oxidation of CH3OH by ·CH3 and ·OH results in the formation of HCHO.

Evaluating Optical Properties of Mixed-Phase 2D MoSe2/Poly(vinyl alcohol) Nanocomposite Film.

Highly solar light-absorbing poly(vinyl alcohol) (PVA) nanocomposite films have garnered wide attention in fields such as flexible optoelectronics, solar energy harvesting, and photothermal therapy. However, fabricating PVA nanocomposite films with a broad spectrum of solar absorption using cost-effective and non-toxic nanofillers remains challenging. Herein, nanocomposite films of PVA incorporating various concentrations of mixed-phase 2D MoSe2 nanosheets (i.e., a combination of the 2H and 1T phase) were prepared using a solution casting technique. Scanning electron microscopy (SEM) shows homogenous dispersion of MoSe2 nanosheets in the PVA matrix even at higher concentrations, while atomic force microscopy (AFM) reveals increasing surface roughness with increasing MoSe2 content, reaching a plateau after 20 wt%. With the increase in the concentration of MoSe2, the nanocomposite films exhibit interesting light absorption characteristics reaching their highest absorption (average 94.9%) at 40 wt% MoSe2. The incorporated mixed-phase MoSe2 nanosheets induce a significant change in the energy levels of the PVA matrix, which is reflected in the reduced optical band gap energy (2.63 eV) at 40 wt% MoSe2 against pure PVA (5.28 eV). The excellent light absorption of PVA nanocomposite films across the entire range from 250 nm to 2500 nm is attributed to the thin 2D structure of MoSe2 and the presence of its mixed phase.

Fabrication and properties of conductive films based on bacterial cellulose and poly-N-isopropylacrylamide-modified graphene oxide

A conductive film (PNIPAM-rGO/BC) was fabricated combining bacterial cellulose (BC) with poly-N-isopropylacrylamide-modified graphene oxide (PNIPAM-GO) through vacuum filtration and steam reduction techniques. The conductivity and performance of PNIPAM-GO composite and the resulting conductive film were studied. The key findings revealed that PNIPAM-GO composite exhibited a reversible temperature-sensitive behavior. Specifically, the lower critical solution temperature (LCST) increased upon the introduction of graphene oxide (GO). Detailed analyses confirmed uniform dispersion of GO nanosheets within the BC matrix. The incorporation of 10.0 % PNIPAM-GO (containing 7.0 % GO) led to a remarkable 19.6 % increase in tensile strength and approximately 37.0 % enhancement in elongation at break for the conductive film (PNIPAM-rGO/BC) compared to BC. After steam reduction, the electrical conductivity of PNIPAM-rGO/BC exhibited significant improvement over BC. Furthermore, the conductive film demonstrated temperature-dependent conductivity, with a resistivity value approximately 5.2 ± 0.2 KΩ at 25 °C. As the test temperature above the LCST of PNIPAM-GO composite, the resistance decreased. These intriguing temperature-sensitive conductive properties position PNIPAM-rGO/BC as a promising material for smart switches.

Collaborative intercalation and reduction of graphene oxide for highly stable and efficient nanofiltration membranes

Two-dimensional (2D) materials, known for their atomically thin profiles and micrometer transverse dimensions, have garnered considerable attentions in membrane technology. Despite their potential, 2D membranes comprising stacked nanosheets often suffer from low permeability and poor stability. Addressing these challenges, we applied collaborative intercalation and reduction strategies to enhance permeability and stability of graphene oxide (GO)-based membranes. We intercalated 2-hydroxypropyl-β-cyclodextrin (2β-CD) into the GO nanosheet dispersion under heat treatment and employed vacuum assisted self-assembly to fabricate the 2β-CD intercalated reduced GO (CD-rGO) membrane. During this process, GO nanosheets underwent reduction, facilitating the formation of hydrogen bonds between 2β-CD and GO. The resulting CD-rGO membrane exhibited markedly improved water permeance at 96.9 L m−2 h−1 bar−1 and an impressive rejection rate at 99.5 % towards Congo red, alongside enhanced stability under a 20 min ultrasonic test at 180 W, and pressure and long-term stability under the cross-flow filtrate tests. The introduction of 2β-CD during heat treatment not only increased the interlayer distance but also utilized the intrinsic pores of 2β-CD and enhanced surface hydrophilicity, contributing to superior separation performance These collaborative strategies offer a facile and promising approach towards high-performance 2D laminated GO-based membranes.

Highly Efficient, Flexible, and Self-Healable Moisture-Driven Energy Harvester Based on 2D Vanadium Pentoxide Nanosheets

The ubiquitous source of atmospheric moisture brought about a fascinating research avenue of extracting atmospheric water to generate sustainable electricity. Energy may be extracted from ambient moisture with obvious and substantial advantages. This point-of-use technology provides a decentralized alternative to meet the energy needs in isolated off-grid places. Unlike traditional energy generators which predominantly rely upon fossil fuel, moisture-induced energy generators can extract energy from moisture in a sustainable and eco-friendly way. Herein, we demonstrated a self-healable moist electric generator (MEG) based on vanadium pentoxide (V2O5) 2D nanosheet membranes. Lamellar membranes of V2O5 nanosheets have been shown to be excellent cation conductors and excellent materials for harvesting energy from ambient moisture. Ultra-thin 2D nanosheets of V2O5 was obtained by treatment of bulk V2O5 crystals with hydrogen peroxide. V2O5 nanosheet membrane was fabricated by vacuum-assisted filtration of 2D V2O5 nanosheets dispersion over a PTFE support membrane. The V2O5 membrane was easily peeled off from the support membrane on drying to obtain a flexible and freestanding V2O5 membrane. The V2O5 membrane consisting of percolated nanofluidic channels was sandwiched between a bottom solid copper foil and a perforated copper foil as the bottom electrode. The top electrode is perforated for exposure to atmospheric humidity. As the atmospheric water molecules come in contact with the V2O5 surface, an open-circuit voltage of 0.5 Volts and a short-circuit current of 0.3 microamperes is generated. The generated voltage and current is attributed to the preferential flow of cations through the V2O5 nanochannels. The exposed surface and edges of V2O5 nanosheets have a high negative surface charge which results in the splitting of water molecules into H3O+ and OH- ions. An electrical double layer (EDL) is established at the V2O5/water interface which selectively permits H3O+ ions through the channels. The mobile ions of the EDL transport through the nanofluidic channels creating a gradient between the two electrodes, resulting in a constant potential difference between the top and bottom electrodes which is harvested as electric current. The MEGs can be easily connected in parallel or series to enhance the current and voltage respectively. We demonstrate ten MEGs connected in series to power small electronic devices such as calculators and humidity meters. One of the key features of the V2O5 MEG is its ability to repair any physical damage to the active material owing to the water-assisted healing characteristics V2O5 membrane. Figure 1

Biobased photothermal responsive shape memory polythioether/MXene nanocomposites with self-extinguishing performance

Thermosetting shape memory polymers (TS-SMPs) have a higher shape fixity ratio (Rf) and shape recovery (Rr) due to their structure integrity and thermal stability, and the glass transition temperature (Tg) usually influences the transition temperature (Ttrans) of TS-SMPs. Therefore, it is significant to tailor the Tg range and mechanical properties for TS-SMPs. In this work, the inherently flame-retarding bio-based MXene-reinforced polythioether nanocomposites with excellent shape memory performance, driven by photothermal response, were designed. Firstly, a photopolymerizable MXene nanomonomer (MPS-MXene) was obtained by introducing 3-(methacryloxy) propyltrimethoxysilane onto the surface of the MXene monolayer. Then, the bis(4-allyl-2-methoxyphenyl) phenyl phosphonate (BEP) was synthesized by eugenol (a lignin derivative) with phenyl phosphonic dichloride. The polythioether/MXene composites (BEP-T-xM) were synthesized through in-situ thiol-ene photopolymerization of MPS-MXene, BEP, and tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate. Surprisingly, compared with neat polythioether, the Tg of BEP-T-0.2 M composite increased from 19.6 to 34.6 °C, when only 0.2 wt% MPS-MXene was added. The photothermal conversion efficiency (η = 73.8 %) and shape memory performance with Rr (>98 %) were greatly improved. Consequently, the interesting phenomena such as “sunflowers growing towards the sunlight” and “thermal shrinkage” can be observed. Meanwhile, the tensile strength and Young’s modulus increased significantly by 141 % and 91 %, respectively, due to the good dispersion of rigid MPS-MXene nanosheets. Furthermore, all the polythioether/MXene composites showed self-extinguishing performance. This study will provide a novel strategy for designing biobased photothermal-responsive TS-SMPs.

Study on the charge transport behaviour of mxene- polymer nanocomposite-based self-assembled floating films at the air-liquid interface

This study explores the fabrication and charge transport behavior of MXene-polymer nanocomposite-based self-assembled floating films at the air-liquid interface. Utilizing ultrasonic dispersion of MXene nanosheets was integrated into a DPP-TTT polymer matrix, significantly enhancing the alignment and crystallization of the polymer chains. The films were fabricated using a unidirectional floating film transfer method (UFTM), which proved to be both simple and cost-effective. UV–visible and grazing incidence X-ray diffraction (GIXD) analyses confirmed increased π–π stacking and improved structural arrangement within the nanocomposites. Organic field-effect transistors (OFETs) fabricated from these films demonstrated that a 3% MXene inclusion resulted in the highest mobility, measuring 3.1 cm2V-1s-1 with an on-off ratio in the order of 104, compared to 1.3 cm2V-1s-1 in pristine DPP-TTT films. However, further increases in MXene content reduced mobility, emphasizing the importance of precise compositional tuning.

Scalable synthesis of Co2C-covered NiTe (Co2C-NiTe) nanosheets as an efficient electrocatalyst for HER & OER in an alkaline medium

To tackle global carbon conditions, renewable energy-powered electrochemical water splitting is a promising energy conversion device that can enhance the sustainable hydrogen output of the next generation. Regarding large-scale water splitting, novel non-noble metal-based heterostructures focus on constructing highly efficient electrocatalysts with unique interfaces toward hydrogen and oxygen evolution reactions. In this work, to facilitate the limited number of defects in the pure Co2C and NiTe electrocatalysts, we report that NiTe nanoflakes are coupled with a dispersed nanosheet network of the Co2C to develop a Co2C-NiTe composite by interface engineering strategy using a hydrothermal approach. XRD, IV, BET, TEM, XPS, and EDX mapping technologies investigated the 3D structure of as-grown Co2C-NiTe/SS. Electrochemical test results revealed that our best-performing electrocatalyst delivers a 10 mAcm−2 with low overpotentials of 279 mV and 227 mV for oxidation and reduction reactions, respectively. Remarkably, this catalyst achieves good stability, reaching up to 90 h in one mol alkaline medium. We showed that this excellent activity of Co2C-NiTe is primarily due to the abundant interfacial area and stable anchoring sites, which improve the adsorption–desorption energy for hydroxide/oxyhydroxide species and thereby provide a fast electron transfer rate for OER/HER. In addition, a synergistic effect of Co2C with NiTe presents high electrical conductivity over counterpart electrocatalysts.

An Ultra‐Smooth rGO Nano‐Thin Film from a Homogeneous Thin Liquid Film Confined by a Conical Fiber Array: Toward the Highly Sensitive Pressure Sensor

AbstractReduced graphene oxide (rGO) thin films have demonstrated various advantages in flexible electronics. So far, solution processes are widely used for making rGO thin films for their mild operation conditions and low cost. However, wrinkles are frequently formed due to the capillary contraction during drying, which severely deteriorates the conductivity and the transparency of rGO thin films. Here, an ultra‐smooth rGO nano‐thin film, featuring wrinkle‐free and a rather low surface roughness of 1.38 nm is developed, which is attributable to a steady and homogeneous thin liquid film confined by a conical fiber array. The thin liquid film facilitates both in‐plane stacking of nanosheets and reducing the buried solvent under nanosheets. Notably, with the capillary flow replenishing the tri‐phase contact line evaporation, a semi‐dry film near the tri‐phase contact line is produced, that enables the force equilibrium of multi‐directional capillary forces on dispersed nanosheets for depositing a wrinkle‐free nanofilm. The as‐prepared rGO nanofilm gives a low sheet resistance of 8.3 kΩ sq−1 and a high transmittance of 91.9%, showing better performances than other reported rGO nanofilms. On this basis, it is demonstrated that a high‐sensitive pressure sensor with a detection limit as low as 0.02 Pa, highlighting the solution‐processed innovative ultra‐smooth 2D nanomaterial thin films, and devices.

Algorithm for Reproducible Analysis of Semiconducting 2D Nanomaterials Based on UV‐VIS Spectroscopy

AbstractRapid and reliable analysis of liquid dispersions of 2D materials is essential for fully harnessing their potential, allowing size and quality validation before subsequent processing or device fabrication. Existing UV‐VIS extinction spectroscopy‐based metrics, particularly those related to thickness, have shown promise but rely on manual data processing, which can introduce irreproducibility and user errors. To address this challenge and enable uniform analysis across laboratories, a freely available program is developed for the reproducible analysis of nanosheet dispersions. Specifically, a smoothing routine is applied to the spectral data, takes the second derivative, and use integral areas to find the wavelength of exciton transitions. This program enables rapid measurement of nanosheet concentration, length, and thickness by UV‐VIS spectroscopy and thickness metrics are refined for eight common 2D nanomaterials. The program and methodology are freely available for use and allow metrics for new materials to be implemented easily in the future.

Dispersion of polyacrylamide and graphene oxide nano-sheets for enhanced oil recovery

Hydrolysed polyacrylamide (HPAM) is widely used in enhancing oil production during tertiary flooding processes by improving the sweep efficiency . However, HPAM faces many challenges under high-temperature and high-salinity conditions mainly caused by the degradation. To overcome these challenges, incorporation of approprioate nanoparticles into HPAM solutions have been recently suggested to enhance its performance during the enhanced oil recovery (EOR) process. The current study specifically investigated the potential of amphiphilic graphene oxide (GO) in enhanicng the performance of HPMA. Its influences on HPAM in terms of the surface activity at the oil-water interface, the mobility behaviour, and the effectiveness in oil recovery were examined. The results revealed that adding up to 0.8 wt% of GO into HPAM reduced the oil-water interfacial tension (IFT) from 62.54 mN/m to 42.78 mN/m, and the contact angle (CA) from 71.08º to 68.84º, while in the mean time increasing the viscosity from 9.07 mPas to 16.49 mPas. Furthermore, the pilot core-flooding study demonstrated that with an addition of 0.8 wt% GO, HPAM achieved higher oil recovery rate (i.e., 76.83 %) than that of the pure HPAM (i.e., 67.39 %). The improved oil recovery performance was attributed to a better mobility ratio, resulting from the increased viscosity of the composite and reduced IFT, which was facilitated by the amphiphilic behaviour of GO, as supported by the desirability model.

The colloidal stability of molybdenum disulfide nanosheets in different natural surface waters: Combined effects of water chemistry and light irradiation

With the increasing production and application, more molybdenum disulfide (MoS2) nanosheets could be released into environment. The aggregation and dispersion of MoS2 nanosheets profoundly impact their transport and transformation in the aquatic environment. However, the colloidal stability of MoS2 remains largely unknown in natural surface waters. This study investigated the colloidal stability of MoS2 nanosheets in six natural surface waters affected by both light irradiation and water chemistry. Compared to that of the pristine MoS2 nanosheets, the colloidal stability of MoS2 photoaged in ultrapure water declined. Light irradiation induced the formation of Mo-O bonds, the release of SO42− species, and the decrease in 1T/2H ratio, which reduced negative charge and enhanced hydrophobicity. However, the colloidal stability of MoS2 photoaged in natural surface waters was increased relative to that in ultrapure water not only for the smaller extent of photochemical transformation but more importantly the surface modification by water chemistry. Furthermore, the colloidal stability of MoS2 photoaged in natural surface waters followed the order of sea water > lake water > river water. The abundant cations (e.g., Ca2+ and Mg2+) in sea water facilitated the covalent grafting (S-C bonds) of more dissolved organic matter (DOM) on MoS2 via charge screening and cation bridging, thus inducing stronger electrostatic repulsion and steric effect to stabilize nanosheets. The crucial role of the covalent grafting of DOM was further confirmed by the positive correlation between the critical coagulation concentration values and S-C ratios (R2 = 0.82, p < 0.05). Our results highlighted the dominant role of water chemistry than light irradiation in dictating the colloidal stability of MoS2 photoaged in natural surface waters, which provided new insight into the environmental behavior of MoS2 in aquatic environment.

Incorporating covalent organic framework nanosheets via solvent-exchange strategy boosted hybrid membrane dehydration performance

The uniform dispersion of fillers within the polymer matrix is crucial for the fabrication of hybrid membranes. In this study, we proposed a facile solvent-exchange strategy for developing a hybrid membrane based on a covalent organic framework (COF, TpPa-1), specifically designed to enhance filler distribution in in the membrane towards pervaporation dehydration of butanol/water mixtures. The TpPa-1 nanosheets prepared via a glycerol-mediated method and their hybrid membranes were characterized using SEM, TGA, XPS, BET, FT-IR, and XRD techniques. Molecular dynamics (MD) results revealed that the solvent-exchange strategy significantly enhanced COF nanosheets (CONs) dispersion by removing glycerol. Pervaporation dehydration performance demonstrated significant improvements in total flux and separation factor when TpPa-1 nanosheets and sodium alginate (SA) were integrated, compared to a pure SA membrane. The optimized COF-SA hybrid membrane achieved a total flux of 1753 g/m2·h and a dehydration separation factor of 4687 at 40 °C for 90 wt% butanol/water mixtures. This study not only highlights a viable approach for membrane solvent dehydration but also provides a design strategy for creating hybrid membranes with uniform filler dispersion.

Enhancing the protective performance of anti-impact, corrosion resistant and flame retardant polyurea coatings using bio-based supramolecular decorated montmorillonite

Developing bio-based nano-additives for enhancing mechanical strength, corrosion resistance, and flame retardancy in polyurea (PUA) coatings at low loading levels is crucial for human well-being and environmental preservation. In this study, montmorillonite (MMT) was first exfoliated by ball milling with the aid of chitosan, and then further co-assembled with phytic acid and urea to form a nanohybrid (CPN@MMT). The resulting CPN@MMT nanohybrid exhibited good compatibility and dispersibility within matrix and endowed PUA composites with improved anti-impact, corrosion resistant and flame retardant properties. Remarkably, the addition of CPN@MMT improved the mechanical and impact protection properties of PUA coatings. Electrochemical and salt spray tests confirmed that the excellent anti-corrosion performance of PUA composite coating stemmed from the dispersed nano-sheets forming a protective nano-barrier. CPN@MMT in the PUA matrix formed a compact char layer, reducing heat release and smoke by inhibiting heat diffusion and volatile gas evaporation, as evidenced by cone calorimeter and TG-FTIR tests. The enhanced fire safety was primarily attributed to the physical barrier, catalytic charring and dilution effect of CPN@MMT. Hence, a green and feasible method was developed to create bio-based nano-additive in PUA coatings with anti-impact, corrosion resistant and flame retardant performance.

Transport and separation behaviors of crosslinked GO/PVA sponge with high porosity

Separation materials (technology) with high efficiency and high precision is a goal that researchers are relentlessly pursuing. Here, crosslinked graphene oxide and polyvinyl alcohol (GO/PVA) sponges with high porosity are reported, which were constructed by crosslinking a dilute solution of GO/PVA. The structure and transport characteristics of the sponges were investigated. It was found that it took 150 days for 30 mg/L methylene blue (MB) to diffuse from the side of crosslinked GO/PVA sponge (10 mm thickness) to the other side (breakthrough) even though the porosity of sponge was up to 92.9 %, while it needed only 2 days in PVA sponge and 13 days for methyl orange (MO) in the sponge. Hence, the transport and separation behaviors of more substances were explored and it is found that not only a precise separation of more than 99 % was achieved for MB/MO (similar molecular weight) mixed solution due to the extremely wide difference of transport rate, but also a water permeability of (4.3 × 105 L·m−2·h−1·Mpa-1) was reached under 10 cm height of water column pressure (0.01 bar), which is three orders of magnitude higher than that of nanofiltration membrane. The extremely high selectivity and efficiency to MB are attributed to the structural features of the sponge, i.e., the fully dispersed GO nanosheets and their crosslinking structure with PVA. Thus, the adsorption amount, adsorption rate, and adsorption strength to MB were greatly improved due to a synergistic effect of GO and PVA, and the highly efficient, precise, and rapid separation of MB was realized. In addition, the structural characteristics of the sponges favor the slow transport of many substances, which will extend their applications to the controlled release field.

Atomically dispersed magnesium enhancing reactive oxygen species generation over g-C3N4 nanosheets for efficient photocatalytic NO removal

Photoinduced reactive oxygen species (ROSs)-involving nitrogen oxide (NOx) abatement offers a green way to mitigate environmental air pollution. Developing cost-effective photocatalysts remains challenging yet crucial. Herein, an atomically dispersed Mg-modified g-C3N4 nanosheet photocatalyst (xMg-CN) with excellent photoactivity is developed. The 1.0Mg-CN sample delivers a high NO removal rate of 52.3% under visible light irradiation within 30 min, far surpassing the Mg-free analog (CN, 41.2%). Moreover, a suppressed NO2 by-product discharge can be achieved. The introduction of Mg single atoms (SAs) alters the charge density distribution on the triazine ring plane of g-C3N4, inducing the formation of a built-in electric field, which improves the photoexcited charge carrier separation. Additionally, Mg SAs contribute to the adsorption and activation of O2 molecules, resulting in enhanced ROSs production, as evidenced by the experiments and theoretical simulations. The findings shed light on the role of SAs in designing highly efficient g-C3N4-based photocatalysts for air purification.