In Situ Reduction of Silver Nanoparticles/Urushiol-Based Polybenzoxazine Composite Coatings with Enhanced Antimicrobial and Antifouling Performances.

Marine anti-fouling coatings represent an efficient approach to prevent and control the marine biofouling. However, a significant amount of antifouling agent is added to improve the static antifouling performance of the coatings, which leads to an issue whereby static antifouling performance conflicts with eco-friendly traits. Herein, this work reports an in situ reduction synthesis of silver nanoparticles (AgNPs) within polymers to produce composite coatings, aiming to solve the aforementioned issue. Firstly, urushiol-based benzoxazine monomers were synthesized by the Mannich reaction, using an eco-friendly natural product urushiol and n-octylamine and paraformaldehyde as the reactants. Additionally, AgNPs were obtained through the employment of free radicals formed by phenolic hydroxyl groups in the urushiol-based benzoxazine monomers, achieved by the in situ reduction of silver nitrate in benzoxazine. Then, the urushiol-based benzoxazine/AgNPs composite coatings were prepared by the thermosetting method. AgNPs exhibit broad-spectrum and highly efficient antimicrobial properties, with a low risk to human health and a minimal environmental impact. The composite coating containing a small amount of AgNPs (≤1 wt%) exhibits effective inhibition against various types of bacteria and marine microalgae in static immersion, thereby displaying outstanding antifouling properties. This organic polymer and inorganic nanoparticle composite marine antifouling coating, with its simple preparation method and eco-friendliness, presents an effective solution to the conflict between static antifouling effectiveness and environmental sustainability in marine antifouling coatings.

Designed Synthesis of Fe/Zr Bimetallic Organic Framework to Enhance the Selective Conversion of H2S to Sulfur.

The development of stable and effective catalysts to convert toxic H2S into high value-added sulfur is essential for production safety and environmental protection. However, the inherent defects of traditional iron- and zirconium-based catalysts, such as poor activity, high oxygen consumption, and low sulfur selectivity, limit their further developments and applications. Herein, the Fe-Zr bimetallic organic framework FeUIO-66(x) with different cubic morphologies was synthesized via a facile solvothermal method. The results indicate that the introduction of Fe not only increases the specific surface area and weak L-sites of the catalyst without changing its crystal structure, which provides enough reaction space and more active sites for the adsorption and activation of H2S, but also reduces the activation energy of the reaction, significantly promoting the selective oxidation of H2S. As a result, the as-obtained FeUIO-66(1) catalyst exhibits the highest desulfurization activity and superior durability and water resistance stability, and its H2S conversion and sulfur selectivity within 50 h are 100 and 88%, respectively. More importantly, the structure of the catalyst after the desulfurization reaction is consistent with that of the fresh counterpart. The study offers new insights into the development of effective and stable bimetallic catalysts to eliminate H2S and recycle sulfur.

Synthesis of Guanine/Vermiculite Two-Dimensional Nanocomposites for Wireless Humidity Sensing in Nut Storage Environment.

Two-dimensional (2D) nanostructures have the advantages of high specific surface area, easy surface functionalization, abundant active sites, and good compatibility with device integration and can be assembled into three-dimensional structures, which are key to the development of high-performance gas sensors. In this study, 2D vermiculite (VMT) nanosheets and guanine (G), two renewable resources with unique chemical structures, were organically combined to fully use the specificity of their molecular structures and functional activities. Driven by the regulation of 2D VMT nanosheets, guanine/vermiculite (G/VMT)-based 2D nanocomposites with controllable pore structure, multiple binding sites, and unobstructed mass transfer were designed and synthesized. The G/VMT nanocomposite material was used as a quartz crystal microbalance (QCM) electrode-sensitive film material to build a QCM-based humidity sensor. G/VMT-based QCM humidity sensor had good logarithmic linear relation (0.9971), high sensitivity (24.49 Hz/% relative humidity), low hysteresis (1.75% RH), fast response/recovery time (39/6 s), and good stability. Furthermore, with a QCM sensor and a specially designed wireless circuit, a wireless humidity detection system transmitting via Wi-Fi allows real-time monitoring of nut storage. This study presents an environmentally friendly, high-performance, miniature 2D nanocomposite sensor strategy for real-time monitoring.

Sustainable Coating Based on Zwitterionic Functionalized Polyurushiol with Antifouling and Antibacterial Properties.

Zwitterionic polymer coatings facilitate the formation of hydration layers via electrostatic interactions on their surfaces and have demonstrated efficacy in preventing biofouling. They have emerged as a promising class of marine antifouling materials. However, designing multifunctional, environmentally friendly, and natural products-derived zwitterionic polymer coatings that simultaneously resist biofouling, inhibit protein adhesion, exhibit strong antibacterial properties, and reduce algal adhesion is a significant challenge. This study employed two diisocyanates as crosslinkers and natural urushiol and ethanolamine as raw materials. The coupling reaction of diisocyanates with hydroxyl groups was employed to synthesize urushiol-based precursors. Subsequently, sulfobetaine moieties were introduced into the urushiol-based precursors, developing two environmentally friendly and high-performance zwitterionic-functionalized polyurushiol antifouling coatings, denoted as HUDM-SB and IPUDM-SB. The sulfobetaine-functionalized polyurushiol coating exhibited significantly enhanced hydrophilicity, with the static water contact angle reduced to less than 60°, and demonstrated excellent resistance to protein adhesion. IPUDM-SB exhibited antibacterial efficacy up to 99.9% against common Gram-negative bacteria (E. coli and V. alginolyticus) and Gram-positive bacteria (S. aureus and Bacillus. sp.). HUDM-SB achieved antibacterial efficacy exceeding 95.0% against four bacterial species. Furthermore, the sulfobetaine moieties on the surfaces of the IPUDM-SB and HUDM-SB coatings effectively inhibited the growth and reproduction of algal cells by preventing microalgae adhesion. This zwitterionic-functionalized polyurushiol coating does not contain antifouling agents, making it a green, environmentally friendly, and high-performance biomaterial-based solution for marine antifouling.

Tannic Acid-Induced Gelation of Aqueous Suspensions of Cellulose Nanocrystals.

Nanocellulose hydrogels are a crucial category of soft biomaterials with versatile applications in tissue engineering, artificial extracellular matrices, and drug-delivery systems. In the present work, a simple and novel method, involving the self-assembly of cellulose nanocrystals (CNCs) induced by tannic acid (TA), was developed to construct a stable hydrogel (SH-CNC/TA) with oriented porous network structures. The gelation process is driven by the H-bonding interaction between the hydroxyl groups of CNCs and the catechol groups of TA, as substantiated by the atoms in molecules topology analysis and FTIR spectra. Interestingly, the assembled hydrogels exhibited a tunable hierarchical porous structure and mechanical moduli by varying the mass ratio of CNCs to TA. Furthermore, these hydrogels also demonstrate rapid self-healing ability due to the dynamic nature of the H-bond. Additionally, the structural stability of the SH-CNC/TA hydrogel could be further enhanced and adjusted by introducing coordination bonding between metal cations and TA. This H-bonding driven self-assembly method may promote the development of smart cellulose hydrogels with unique microstructures and properties for biomedical and other applications.

Ultrastrong and Tough Urushiol-Based Ionic Conductive Double Network Hydrogels as Flexible Strain Sensors.

Ionic conductive hydrogels have attracted increasing research interest in flexible electronics. However, the limited resilience and poor fatigue resistance of current ionic hydrogels significantly restrict their practical application. Herein, an urushiol-based ionic conductive double network hydrogel (PU/PVA-Li) was developed by one-pot thermal initiation polymerization assisted with freeze-thaw cycling and subsequent LiCl soaking. Such a PU/PVA-Li hydrogel comprises a primary network of covalently crosslinked polyurushiol (PU) and a secondary network formed by physically crosslinked poly(vinyl alcohol) (PVA) through crystalline regions. The obtained PU/PVA-Li hydrogel demonstrates exceptional mechanical properties, including ultrahigh strength (up to 3.4 MPa), remarkable toughness (up to 1868.6 kJ/m3), and outstanding fatigue resistance, which can be attributed to the synergistic effect of the interpenetrating network structure and dynamic physical interactions between PU and PVA chains. Moreover, the incorporation of LiCl into the hydrogels induces polymer chain contraction via ionic coordination, further enhancing their mechanical strength and resilience, which also impart exceptional ionic conductivity (2.62 mS/m) to the hydrogels. Based on these excellent characteristics of PU/PVA-Li hydrogel, a high-performance flexible strain sensor is developed, which exhibits high sensitivity, excellent stability, and reliability. This PU/PVA-Li hydrogel sensor can be effectively utilized as a wearable electronic device for monitoring various human joint movements. This PU/PVA-Li hydrogel sensor could also demonstrate its great potential in information encryption and decryption through Morse code. This work provides a facile strategy for designing versatile, ultrastrong, and tough ionic conductive hydrogels using sustainable natural extracts and biocompatible polymers. The developed hydrogels hold great potential as promising candidate materials for future flexible intelligent electronics.

Urushiol-Based Benzoxazine Containing Sulfobetaine Groups for Sustainable Marine Antifouling Applications.

Benzoxazine resins are new thermosetting resins with excellent thermal stability, mechanical properties, and a flexible molecular design, demonstrating promise for applications in marine antifouling coatings. However, designing a multifunctional green benzoxazine resin-derived antifouling coating that combines resistance to biological protein adhesion, a high antibacterial rate, and low algal adhesion is still challenging. In this study, a high-performance coating with a low environmental impact was synthesized using urushiol-based benzoxazine containing tertiary amines as the precursor, and a sulfobetaine moiety into the benzoxazine group was introduced. This sulfobetaine-functionalized urushiol-based polybenzoxazine coating (poly(U-ea/sb)) was capable of clearly killing marine biofouling bacteria adhered to the coating surface and significantly resisting protein attachment. poly(U-ea/sb) exhibited an antibacterial rate of 99.99% against common Gram negative bacteria (e.g., Escherichia coli and Vibrio alginolyticus) and Gram positive bacteria (e.g., Staphylococcus aureus and Bacillus sp.), with >99% its algal inhibition activity, and it effectively prevented microbial adherence. Here, a dual-function crosslinkable zwitterionic polymer, which used an "offensive-defensive" tactic to improve the antifouling characteristics of the coating was presented. This simple, economic, and feasible strategy provides new ideas for the development of green marine antifouling coating materials with excellent performance.

Two-dimensional lamellar polyimide/cardanol-based benzoxazine copper polymer composite coatings with excellent anti-corrosion performance.

The economic loss and environmental damage caused by metal corrosion is irreversible. Thus, effective methods, such as coating technologies are used to protect metal surfaces from corrosion. In this work, cardanol-based benzoxazine (CB) was synthesized by a solvent-free method using cardanol, paraformaldehyde and n-octylamine. A cardanol-based benzoxazine copper polymer (CBCP) with good mechanical properties was then prepared by CuCl2 catalysis and can be cured at room temperature. Subsequently, polyimide corrosion inhibitors with a two-dimensional sheet structure (pyromellitic dianhydride polyimide (PDPI) and 1,4,5,8-naphthalene tetracarboxylic dianhydride polyimide (NDPI)) were designed and prepared. Lastly, PDPI or NDPI was mixed with CBCP to obtain two-dimensional lamellar polyimide/cardanol-based benzoxazine copper polymer composite coatings. The Tafel curves and electrochemical impedance spectroscopy (EIS) measurements showed composite coatings with good corrosion resistance in different corrosive media. Compared to CBCP coating, the anticorrosion performance of the composite coatings improved obviously, especially the coating obtained with 0.5 wt% PDPI. It exhibits a high polarization resistance (3.874 × 109 Ω), a high protection efficiency (99.99% and 97.98%) and low corrosion rate (3.376 × 10-6 mm year-1). This work suggested a facile and eco-friendly strategy for preparing bio-based anticorrosive composite coatings from low cost and abundant cardanol and polyimide corrosion inhibitors, which will significantly promote their application in metal anticorrosion.

Bimetallic Metal-Organic Frameworks MIL-53(xAl-yFe) as Efficient Catalysts for H2S Selective Oxidation.

Catalytic oxidation of H2S is a crucial green pathway that can fully convert H2S into value-added elemental S for commercial use. However, achieving high catalytic stability and S selectivity by traditional-metal-based catalysts still remain a major challenge. Herein, a facile one-step solvothermal strategy is designed for the fabrication of bimetallic MIL-53(xAl-yFe) catalysts. The as-synthesized MIL-53(1Al-5Fe) possesses ample coordinatively unsaturated metal sites, which served as efficient catalytic sites for the selective oxidation of H2S. As a result, the representative MIL-53(1Al-5Fe) achieves a S yield of nearly 100% at 100-160 °C with almost no obvious decrease of catalytic stability in the run of 30 h. Under the defined reaction conditions, the bimetallic metal-organic frameworks are obviously superior to MIL-53(Al) (49.3%) and MIL-53(Fe) (70.5%) in S yield. This study suggests that the introduction of elemental Al into MIL-53(xAl-yFe) could effectively modulate the electronic properties and spatial configuration of the catalysts, further conducing the adsorption and activation of H2S and thus accelerating the dissociation of H2S into a key intermediate S* and improving their catalytic performance.

A bioinspired hydrogen bond crosslink strategy toward toughening ultrastrong and multifunctional nanocomposite hydrogels.

Developing physical hydrogels with advanced mechanical performance and multi-functionalities as alterative materials for load-bearing soft tissues remains a great challenge. Biological protein-based materials generally exhibit superior strength and toughness owing to their hierarchical structures via hydrogen-bonding assembly. Inspired by natural biological protein materials, tannic acid (TA) is exploited as a molecular coupling bridge between cellulose nanocrystals (CNCs) and poly(vinyl alcohol) (PVA) chains for the fabrication of a bio-based advanced physical hydrogel via strong multiple H-bonds. When exposed to mechanical stress, the sacrificial H-bonds can dissipate energy effectively on the molecular scale via dynamic rupture and reformation, endowing these biomimetic hydrogels with remarkable toughness, ultrahigh strength, large elongation, and good self-recoverability, which are much superior to those of most hydrogen bond-based hydrogels. Moreover, the characteristics of TA endow these biomimetic hydrogels with versatile adhesiveness and good antibacterial properties. This work presents an innovative biomimetic strategy for robust biocompatible hydrogels with superior mechanical strength and functionalities, which holds great promise for applications in tissue engineering and biomedical fields.

Removal of bisphenol A from aqueous solution via host-guest interactions based on beta-cyclodextrin grafted cellulose bead.

ß-CD grafted cellulose bead had been successfully prepared via dropping method, following by cross-linking reaction under mild conditions. The efficient grafting of ß-CD on the cellulose bead made it promising adsorbent toward BPA, which combined the inclusion complexation property of ß-CD and advantages of cellulose bead. The structure of the grafted cellulose bead was characterized by FTIR, XRD and 13C NMR, which confirmed the covalent bonding between cellulose bead and ß-CD. The SEM and BET analysis revealed that the grafting of ß-CD on the cellulose bead maintained the highly porous morphology of cellulose bead, meanwhile enhanced its specific surface area. Thus, the resulting modified cellulose bead presented much higher adsorption capacity toward BPA than pristine cellulose bead, since the presence of ß-CD facilitated the formation of inclusion complexes via host-guest interactions. It was found that the maximum BPA adsorption capacity of grafted cellulose bead was 30.77 mg/g. The adsorption process fitted well with the Langmuir isotherm model and the pseudo-second-order kinetic model. Further studies of ad/desorption experiments revealed that the ß-CD grafted cellulose bead could be regenerated easily in methanol. Based on these results, the adsorbents prepared here can be potentially used in the treatment of micropollutants in water.

Microfibrillated cellulose enhancement to mechanical and conductive properties of biocompatible hydrogels.

A combination of conductive polymer with natural biomass is an ideal alternative to the classical conductive materials. In this study, PPy/SA/TOMFC composite hydrogels were fabricated by incorporation of TEMPO-oxidized microfibrillated cellulose (TOMFC) into the alginate-based matrix along with the in situ polymerization of pyrrole monomer. It was found that the mechanical and conductive properties of the composite hydrogels were associated with the concentration of TOMFC, which facilitated the formation of more compact 3D network structures and the growing of PPy conductive network. The mechanical properties of the synthesized hydrogels were significantly enhanced by incorporation of higher amount of TOMFC. In addition, with the introduction of 5.0 wt% TOMFC, the electrical conductivity of composite hydrogels could be ten times higher than that of PPy/SA hydrogels. Moreover, the obtained PPy/SA/TOMFC hydrogels exhibited tunable swelling properties and good biocompatibility, making them promising candidates for the use as biomaterial.

One-pot construction of cellulose-gelatin supramolecular hydrogels with high strength and pH-responsive properties.

Inspired by the supramolecular structure of cellulose, cellulose-gelatin supramolecular hydrogels with high strength and pH-sensitivity were constructed in a basic-based solvent system, ethylene diamine/potassium thiocyanate (EDA/KSCN) with the aid of cyclic freezing-thawing. The investigation on the characteristics of supramolecular hydrogels revealed that repeated freezing-thawing cycles played an important role in the formation of the physical cross-linked supramolecular network structure between cellulose and gelatin. The mechanical properties of supramolecular hydrogels were much higher than pure cellulose and gelatin hydrogel, and the compressive strength was 9.6 times higher than that of pure gelatin hydrogel. The synergistic effect between hydrogen-bonding interaction and the reinforcement of regenerated cellulose nanofibrils (CNF) contributed to the superior mechanical performance. Furthermore, the swelling kinetics tests showed that the supramolecular hydrogels exhibited excellent pH-responsibility, indicating potential applications in biomedical fields. Thus, a straightforward route to construct natural polymer-based hydrogels with supramolecular structure through physical crosslinking strategy without employing hazardous crosslinking agents was developed, paving the way for the design of new types of hydrogels.

Effect of silicone oil heat treatment on the chemical composition, cellulose crystalline structure and contact angle of Chinese parasol wood.

The effect of silicone oil heat treatment (SOTH) on the chemical composition, cellulose crystalline structure, thermal degradation and contact angle of Chinese parasol wood were examined in this study. Samples were heated at 150°C, 180°C and 210°C for 2h and 8h, after SOHT chemical composition, fourier transformed infrared (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) of the treated samples were evaluated. Results showed that the chemical components of the wood were affected after SOHT particularly when treated at 210°C for 8h. Changes in the chemical components was due to the degradation of biopolymer components of the wood during SOHT. The crystallinity index of cellulose and contact angle of the SOHT samples was increased. The findings demonstrate the potential of SOHT for modification of wood. Thus an economical and eco-friendly approach to thermally modified wood was achieved in this study.