High-Strength, High-Swelling-Resistant, High-Sensitivity Hydrogel Sensor Prepared with Wood That Retains Lignin.

Wood-derived hydrogels possess satisfactory longitudinal strength but lack excellent swelling resistance and dry shrinkage resistance when achieving high anisotropy. In this study, we displayed the preparation of highly dimensional stable wood/polyacrylamide hydrogels (wood/PAM-Al3+). The alkali-treated wood retains lignin as the skeleton of the hydrogel. Second, Al ions were added to the metal coordination with lignin. Finally, by employing free radical polymerization, we construct a conductive electronic network using polyaniline within the wood/PAM-Al3+ matrix to create the flexible sensor. This approach leverages lignin's integrated structure within the middle lamella to provide enhanced swelling resistance and stronger binding strength in the transverse direction. Furthermore, coordination between lignin and Al ions improves the mechanical strength of the wood hydrogel. Polyaniline provides stable linear pressure and temperature responses. The wood/PAM-Al3+ exhibits a transverse swelling ratio of 3.90% while achieving a longitudinal tensile strength of 20.5 MPa. This high-strength and high-stability sensor is capable of monitoring macroscale human behavior. Therefore, this study presents a simple yet innovative strategy for constructing tough hydrogels while also establishing an alternative pathway for exploring lignin networks in new functional materials development.

Natural organic-inorganic hybrid structure enabled green biomass adhesive with desirable strength, toughness and mildew resistance.

Plant based proteins are green, sustainable, and renewable materials that show the potential to replace traditional formaldehyde resin. High performance plywood adhesives exhibit high water resistance, strength, toughness, and desirable mildew resistance. Adding petrochemical-based crosslinkers is not economically viable or environmentally benign; this chemical crosslinking strategy makes the imparted high strength and toughness less attractive. Herein, a green approach based on natural organic-inorganic hybrid structure enhancement is proposed. The design of soybean meal-dialdehyde chitosan-amine modified halloysite nanotubes (SM-DACS-HNTs@N) adhesive with desirable strength and toughness enhanced by covalent bonding (Schiff base) crosslinking and toughened by surface-modified nanofillers is demonstrated. Consequently, the prepared adhesive showed a wet shear strength of 1.53 MPa and work of debonding of 389.7 mJ, which increased by 146.8 % and 276.5 %, respectively, due to the cross-linking effect of organic DACS and toughening effect of inorganic HNTs@N. The introduction of DACS and Schiff base generation enhanced the antimicrobial property of the adhesive and increased the mold resistance of the adhesive and plywood. In addition, the adhesive has good economic benefits. This research creates new opportunities for developing biomass composites with desirable performance.

Biomimetic cellulose-nanocrystalline-based composite membrane with high flux for efficient purification of oil-in-water emulsions.

The massive discharge of oily wastewater and oil spills are causing serious pollution to water resources. It is urgent to require clean and efficient method of purifying oily emulsions. Although the separation membranes with selective wettability have been widely used in the efficient purification of oil/water emulsions. It is still very challenging to develop functional films that are environmentally friendly, fouling resistant, inexpensive, easy to prepare, easy to scale, and highly efficient. Cellulose nanocrystalline-based composite membranes (CCM) were prepared by surface-initiated atom transfer radical polymerization (SATRP) and vacuum self-assembly. The prepared CCM is superhydrophilic and superoleophobic underwater due to the hydrophilic nature of the modified cellulose-nanocrystalline and the micro-nano surface structure. The CCM shows high separation efficiency (> 99.9 %), high flux (16,692 L-1·m-2·h-1·bar-1) for surfactant-stabilized oil-in-water emulsions, good cycle stability and anti-fouling performance. This biomass-derived membrane is green, cheap, easy to manufacture, scalable, super-wettability, and durability, it promises to be an alternative to separation membranes in today's market.

Ultra-Thin Wood-Based Acoustic Diaphragms Fabricated via an Environmentally Friendly Strategy.

An acoustic diaphragm is a crucial component that regulates sound quality in earphones and loudspeakers. Natural wood with inherent good acoustic resonance and vibration spectrum is widely used in sound devices. However, using natural wood to produce an acoustic diaphragm is still a big challenge because making ultra-thin wood is hard and it warps easily. Therefore, this study introduces a new method for preparing ultra-thin wood acoustic diaphragms less than 10 µm in thickness, relying on delignification, sulfonation, and densifying techniques. The innovative sulfonation process increased the intermolecular hydrogen bond force, which significantly improved the tensile strength and Young's modulus of the wood diaphragm, up to 195 MPa and 27.1 GPa, respectively. Compared with the commonly used diaphragms in the market, this wood diaphragm exhibits an excellent specific dynamic elastic modulus up to 95.1 GPa/g cm3, indicating better acoustic properties. Also, the resonance frequency was up to 1240 Hz, 4.5 times higher than the titanium diaphragm among high-end products. Besides, the drying shrinkage rate of the ultra-thin wood diaphragm is only 1.2%, indicating excellent dimensional stability. This high-quality wood acoustic diaphragm has a very high application prospect and outstanding attributes for promoting the development of acoustic devices. Moreover, the reaction reagent can be recycled after preparation, and the selected reagents are green and environmentally friendly.

A biomimetic adhesive with high adhesion strength and toughness comprising soybean meal, chitosan, and condensed tannin-functionalized boron nitride nanosheets.

Soybean meal (SM)-based adhesive can solve the issues of formaldehyde emission and over-reliance of aldehyde-based resins but suffers from poor water resistance, weak adhesion strength, and high brittleness. Herein, a high-performance adhesive inspired by lobster cuticular sclerotization was developed using catechol-rich condensed tannin-functionalized boron nitride nanosheets (CT@BNNSs), amino-containing chitosan (CS), and SM (CT@BNNSs/CS/SM). The oxidative crosslinking between the catechol and amino, initiated by oxygen at high temperatures, formed a strengthened and water-resistant interior network. These strong intermolecular interactions induced by phenol-amine synergy accompanied by the reinforcement of uniformly dispersed BNNSs improved the load transfer and energy dissipation capacity, endowing the adhesive with great cohesion strength. Given these synergistic effects, the biomimetic CT@BNNSs/CS/SM adhesive caused noticeable improvements in water tolerance, mechanical strength, and toughness over the neat SM adhesive, e.g., enhanced wet shear strength (1.46 vs. 0.66 MPa, respectively), boiling water shear strength (0.92 vs. 0.43 MPa, respectively), and debonding work (0.368 vs. 0.113 J, respectively). Thus, this study provided a green and low-cost bionic strategy for the preparation of high-performance biomass adhesives.

Photocatalytic degradation of surface-coated tourmaline-titanium dioxide for self-cleaning of formaldehyde emitted from furniture.

Formaldehyde emission is an intrinsic property derived from aldehyde-based resin that is used in wood-based composites. To reduce formaldehyde emission from plywood, the composite catalyst of tourmaline-titanium dioxide (T-TiO2) was fabricated by the sol-gel method. Furthermore, the impregnated paper loaded with the T-TiO2 composite catalyst was used to decorate the surface of 5-layer poplar plywood. The physicochemical structure, photocatalytic activity of T-TiO2 composite catalyst and its mechanism of degrading gaseous formaldehyde and generating air negative ions were assessed. The results discovered that the synergistic influence of the tourmaline and TiO2 anatase nanocrystals achieved good photodegradation of the gaseous formaldehyde. The neat T(20%)-TiO2 catalyst offered a higher formaldehyde removal efficiency (92.2%) than other catalysts, possessing 800 ions/cm3 of air negative ions concentration after 10-h visible light irradiation. The poplar plywood with a load of 3% T(20%)-TiO2 catalyst can stably induce the degradation formaldehyde into air negative ions with a concentration of 1200 ions/cm3 in visible light. The impregnation process of paper was feasible to be industrialized and the decorated wood-based composites can be widely applied in the furniture industry.

A One Pot Method for Preparing an Antibacterial Superabsorbent Hydrogel with a Semi-IPN Structure Based on Tara Gum and Polyquaternium-7.

An antibacterial superabsorbent polymer was prepared by graft polymerization of acrylic acid onto tara gum polysaccharide, by adding N,N-dimethyl-N-2-propenyl-2-propen-1-aminium chloride and a polymer with 2-propenamide (polyquaternium-7, PQ7) as an antibacterial agent. The effects of the amount of PQ7 in the hydrogel on its swelling ratio were investigated and maximum swelling ratios of 712 g/g and 68 g/g, in distilled water and 0.9 wt % NaCl solution were attained with 0.5 g PQ7 per gram of tara gum. The superabsorbent hydrogel was characterized by using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermal gravimetric analysis. The results showed that poly (acrylic acid) was successfully grafted onto tara gum and a three-dimensional network structure formed with PQ7 chains penetrated in the networks. The antibacterial properties of these superabsorbent hydrogels against Staphylococcus aureus and Escherichia coli improved with increasing PQ7 content. This study demonstrates a method of preparing novel functional superabsorbent hydrogels.

In-Situ pH-Sensitive Fibers via the Anchoring of Bromothymol Blue on Cellulose Grafted with Hydroxypropyltriethylamine Groups via Adsorption.

In-situ pH-sensitive cellulose fibers (IS-pH-SCF) were prepared by anchoring bromothymol blue (BTB) onto cellulose fibers (CF) modified with hydroxypropyltriethylamine (HPTTL) groups. Fourier transform infrared and X-ray photoelectron spectrum analyses demonstrated that the HPTTL groups were grafted onto the CF. X-ray diffraction proved that cellulose I in the CF transformed into cellulose II after quaternization. Scanning electron microscopy suggested that the quaternized CF (QCF) surface was clean and uniformly ridged. The adsorption of BTB onto QCF was carried out via batch adsorption experiments. A kinetic study illustrated that the adsorption was a spontaneous process and described well by pseudo-second-order, Freundlich and Temkin isotherms. The activation energy for the BTB adsorption onto QCF was 52.89 kJ/mol, which proved that the BTB adsorption onto QCFs was chemically controlled. The pH response demonstrated that the IS-pH-SCF was highly sensitive to pH, with an obvious color change for pH 4 to 8. The release tests showed that BTB was anchored on QCFs and that no BTB was released. IS-pH-SCF has a potential use for indicating pH changes in food.

Preparation of heterostructured WO3/TiO2 catalysts from wood fibers and its versatile photodegradation abilities.

A facile route was adopted to synthesize heterostructured WO3/TiO2 photocatalysts from wood fibers through a two-steps hydrothermal method and a calcination process. The prepared WO3/TiO2-wood fibers were used as photocatalysts under UV irradiation for photodegradation of rhodamine B, methylene blue and methyl orange. In calcination process, the wood fibers acted as carbon substrates to prepare the WO3/TiO2 photocatalysts with high surface area and unique morphology. Thus, the significant enhanced photodegradation efficiency of the organic pollutants with the WO3/TiO2-wood fibers under UV irradiation was obtained. The photodegradation rates are measured which confirms the highest performance of the WO3/TiO2-wood fibers after calcination in comparison to the TiO2-wood fibers after calcination and the pure WO3/TiO2 after calcination. Moreover, the photodegradation efficiency of the WO3/TiO2-wood fibers after calcination under visible light is high. Our results demonstrated that the WO3/TiO2-wood fibers after calcination are a promising candidate for wastewater treatment in practical application.

Negative Oxygen Ions Production by Superamphiphobic and Antibacterial TiO2/Cu2O Composite Film Anchored on Wooden Substrates.

According to statistics, early in the 20th century, the proportion of positive and negative air ions on the earth is 1 : 1.2. However, after more than one century, the equilibrium state of the proportion had an obvious change, which the proportion of positive and negative air ions became 1.2 : 1, leading to a surrounding of positive air ions in human living environment. Therefore, it is urgent to adopt effective methods to improve the proportion of negative oxygen ions, which are known as "air vitamin". In this study, negative oxygen ions production by the TiO2/Cu2O-treated wood under UV irradiation was first reported. Anatase TiO2 particles with Cu2O particles were doped on wooden substrates through a two-step method and further modification is employed to create remarkable superamphiphobic surface. The effect of Cu2O particles dopant on the negative oxygen ions production of the TiO2-treated wood was investigated. The results showed that the production of negative oxygen ions was drastically improved by doping with Cu2O particles under UV irradiation. The wood modified with TiO2/Cu2O composite film after hydrophobization is imparted with superamphiphobicity, antibacterial actions against Escherichia coli, and negative oxygen ions production under UV irradiation.