Highly Anisotropic, Highly Transparent Wood Composites

Highly transparent cellulose-based phosphorescent materials with tunable afterglow colors and white emission

Room temperature phosphorescence (RTP) materials with wood as framework are highly desirable due to their extended afterglow, high haze and good mechanical properties, which is highly desired in lighting materials. However, it remains challenging to obtain wood-based RTP materials that possess on-demand afterglow colors while maintaining high transparency across the entire visible spectrum. In this study, long-persistent phosphorescent transparent composite with tunable afterglow color is fabricated by infiltrating delignified wood with phosphors (including carbazole, naphthalene, and pyrene) doped polymethyl methacrylate (PMMA). Such RTP woods indicate remarkable transparency, over 70 %, and an extended afterglow duration of up to 8 s. Here, PMMA serves as rigid surrounding to suppress the non-radiative transition of phosphors to ensure phosphorescence, and to fulfill in the wood lumen to match the refractive index of cellulose for transparency. By formulating phosphors with different types and concentration ratios, transparent woods with diverse phosphorescence colors, and white emission, are successfully achieved. Furthermore, the RTP woods demonstrate dynamically tunable afterglow colors over time based on the varied phosphorescent lifetimes. Characterized by their high transparency and tunable colors, these natural wood-based RTP materials have great potentials for application in the fields of LED materials, optics, and building materials.

Processing natural bamboo into white bamboo through photocatalyzed lignin oxidation

Scalable and highly efficient bamboo whitening remains a great challenge. Herein, an effective bamboo whitening strategy is proposed based on photocatalyzed oxidation, which involves H2O2 infiltration and UV illumination. The as-prepared white bamboo well maintains the nature structure of natural bamboo and demonstrates high whiteness and superior mechanical properties. The absorbance value is significantly decreased to 3.5 and the transmittance is increased to 0.04 % in UV-visible wavelength range due to the removal of light-absorbing chromospheres of lignin, resulting in a high whiteness when the UV illumination time is 8 h. In addition, the white bamboo displays a high tensile strength of 30 MPa and a high flexural strength of 36 MPa due to the well-preserved lignin units (lignin preservation is about 89 %). XRD patterns and analysis show that photocatalyzed oxidation has no effect on the crystal parameters of cellulose. Compared with the traditional bamboo whitening technology, our photocatalyzed oxidation strategy demonstrates significant advantage including chemical and time conservation, high efficiency, environment friendliness, and mechanical robustness. This highly efficient and environmentally friendly photocatalyzed oxidation strategy for the fabrication of white bamboo may pave the way of bamboo-based energy-efficient structural materials for engineering application.

Pore-Forming Toxin-Driven Recovery of Peroxidase-Mimicking Activity in Biomass Channels for Label-Free Electrochemical Bacteria Sensing

The development of sensitive, selective, and rapid methods to detect bacteria in complex media is essential to ensuring human health. Virulence factors, particularly pore-forming toxins (PFTs) secreted by pathogenic bacteria, play a crucial role in bacterial diseases and serve as indicators of disease severity. In this study, a nanochannel-based label-free electrochemical sensing platform was developed for the detection of specific pathogenic bacteria based on their secreted PFTs. In this design, wood substrate channels were functionalized with a Fe-based metal-organic framework (FeMOF) and then protected with a layer of phosphatidylcholine (PC)-based phospholipid membrane (PM) that serves as a peroxidase mimetic and a channel gatekeeper, respectively. Using Staphylococcus aureus (S. aureus) as the model bacteria, the PC-specific PFTs secreted by S. aureus perforate the PM layer. Now exposed to the FeMOF, uncharged 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) molecules in the electrolyte undergo oxidation to cationic products (ABTS•+). The measured transmembrane ionic current indicates the presence of S. aureus and methicillin-resistant S. aureus (MRSA) with a low detection limit of 3 cfu mL-1. Besides excellent specificity, this sensing approach exhibits satisfactory performance for the detection of target bacteria in the complex media of food.

Molecular-caged metal-organic frameworks for energy management

Metal-organic frameworks (MOFs) hold great promise for diverse applications when combined with polymers. However, a persistent challenge lies in the susceptibility of exposed MOF pores to molecule and polymer penetration, compromising the porosity and overall performance. Here, we design a molecular-caged MOF (MC-MOF) to achieve contracted window without sacrificing the MOF porosity by torsional conjugated ligands. These molecular cages effectively shield against the undesired molecule penetration during polymerization, thereby preserving the pristine porosity of MC-MOF and providing outstanding light and thermal management to the composites. The polymer containing 0.5 wt % MC-MOF achieves an 83% transmittance and an exceptional haze of 93% at 550 nanometers, coupled with remarkable thermal insulation. These MC-MOF/polymer composites offer the potential for more uniform daylighting and reduced energy consumption in sustainable buildings when compared to traditional glass materials. This work delivers a general method to uphold MOF porosity in polymers through molecular cage design, advancing MOF-polymer applications in energy and sustainability.

Modulation of Electronic Synergy to Enhance the Intrinsic Activity of Fe5Ni4S8 Nanosheets in Restricted Space Carbonized Wood Frameworks for Efficient Oxygen Evolution Reaction

Modulation of electronic structure and composition is widely recognized as an effective strategy to improve electrocatalyst performance. Herein, using a simple simultaneous carbonization and sulfidation strategy, NiFe double hydroxide-derived Fe5Ni4S8 (FNS) nanosheets immobilized on S-doped carbonized wood (SCW) framework by taking benefit of the orientation-constrained cavity and hierarchical porous structure of wood is proposed. Benefiting from the synergistic relationships between bimetal ions, the spatial confinement offered by the wood cavity, and the enhanced structural effects of the nanosheets array, the FNS/SCW exhibit enhanced intrinsic activity, increased accessibility of catalytically active sites, and convection-facilitated mass transport, resulting in an excellent oxygen evolution reaction (OER) activity and durability. Specifically, it takes a low overpotential of 230 mV at 50 mA cm-2 and potential increase is negligible (3.8%) at 50 mA cm-2 for 80 hours. Density functional theory (DFT) calculations further reveal that the synergistic effect of bimetal can optimize the electronic structure and lower the reaction energy barrier. The FNS/SCW used as the cathode of zinc-air battery shows higher power density and excellent durability relative to commercial RuO2, exhibiting a good application prospect. Overall, this research offers proposals for designing and producing effective OER electrocatalysts using sustainable resources.

Mismatched Refractive Index Strategy for Fabricating Laser-Driven Wood Diffusers from Bulk Wood for Illumination Applications

Laser-diode-based solid-state lighting is primarily used in state-of-the-art illumination systems. However, these systems rely on light-converting inorganic phosphors, which have low quantum efficiencies and complex manufacturing conditions. In this study, a mismatched refractive index strategy is proposed to directly convert natural bulk wood into a laser-driven wood diffuser using a simple delignification and polymer infiltration method. The resulting material has the potential to be used in laser-driven diffuse illumination applications. The optical performance of the laser-driven wood diffuser is optimized by changing the density of natural wood. The optimal coefficient of illuminance variation of the wood diffuser is as low as 17.7%, which is significantly lower than that of commercial diffusers. The illuminance uniformity is larger than 0.9, which is significantly higher than the ISO requirements for indoor workplace lighting. The laser damage threshold is 7.9 J cm-2, which is considerably higher than those of the substrates of commercially available phosphors. Furthermore, the optimized wood diffuser exhibits outstanding mechanical properties, excellent thermal stability, tolerance to harsh environmental conditions, and low speckle contrast. These results show that the laser-driven wood diffuser is a promising laser-color converter that is suitable for indoor, long-distance outdoor, undersea, and other high-luminance laser lighting applications.

Tunable evaporation-induced surface morphologies on chitosan film for light management

The surface morphologies of polymer films have been used to improve the performance or enable new applications of films, such as controllable adhesion, shape morphing and light management. However, complicated and destructive methods were applied to produce surface morphologies on chitosan (CS) film. To overcome this challenge, we report an evaporation-induced self-assembly to form the tunable morphologies on the surface of short-chain chitosan film by varying the evaporation rates that influence the aggregation behavior of polymer chains between order and disorder. It enables the simple, tunable and scalable fabrication of surface morphologies on CS film (CS solution concentration: 2 wt%, drying from room temperature (RT) to 80 °C) that provides controllable haze (3-74 %) and high transmittance (>85 %) for the production of hazy and transparent window coatings. This simple approach to producing tunable surface morphologies could inspire the synthesis of multifunctional polymer films with different surface structures, whose applications can be extended to cell culture interfaces, flexible bioelectronic and optoelectronic devices.

Nanotechnology in wood science: Innovations and applications

Application of nanomaterials is gaining tremendous interest in the field of wood science and technology for value addition and enhancing performance of wood and wood-based composites. This review focuses on the use of nanomaterials in improving the properties of wood and wood-based materials and protecting them from weathering, biodegradation, and other deteriorating agents. UV-resistant, self-cleaning (superhydrophobic) surfaces with anti-microbial properties have been developed using the extraordinary features of nanomaterials. Scratch-resistant nano-coatings also improve durability and aesthetic appeal of wood. Moreover, nanomaterials have been used as wood preservatives for increasing the resistance against wood deteriorating agents such as fungi, termites and borers. Wood can be made more resistant to ignition and slower to burn by introducing nano-clays or nanoparticles of metal-oxides. The use of nanocellulose and lignin nanoparticles in wood-based products has attracted huge interest in developing novel materials with improved properties. Nanocellulose and lignin nanoparticles derived/synthesized from woody biomass can enhance the mechanical properties such as strength and stiffness and impart additional functionalities to wood-based products. Cellulose nano-fibres/crystals find application in wide areas of materials science like reinforcement for composites. Incorporation of nanomaterials in resin has been used to enhance specific properties of wood-based composites. This review paper highlights some of the advancements in the use of nanotechnology in wood science, and its potential impact on the industry.

Programmable and Shape-Color Synchronous Dual-Response Wood with Thermal Stimulus

Stimuli-responsive materials exhibit huge potential in sensors, actuators, and electronics; however, their further development for reinforcement, visualization, and biomass-incorporation remains challenging. Herein, based on the impregnation of thermochromic microcapsule (TCM)-doped dynamic covalent vitrimers, a programmable shape-color dual-responsive wood (SRW-TC) was demonstrated with robust anisotropic structures and exchangeable covalent adaptable networks. Under mild conditions, the resultant SRW-TC displays feasible shape memorability and programmability, resulting from the rigidity-flexibility shift induced by the glass-transition temperature (34.99 °C) and transesterification reaction triggered by the topology freezing transition temperature (149.62 °C). Furthermore, the obtained SRW-TC possesses satisfactory mechanical performance (tensile strength of 45.70 MPa), thermal insulation (thermal conductivity of 0.27 W/m K), anisotropic light management, and benign optical properties (transmittance of 51.73% and haze of 99.67% at 800 nm). Importantly, the incorporation of compatible TCM enables SRW-TC to visualize shape memory feasibility and rigidity/flexibility switching and respond to the external thermal stimulus through the thermal-induced shape-color synchronous dual-responsiveness, which successfully demonstrates the applications of sensing temperature, grasping objects, encrypting/decoding icon messages, and so on. The proposed facile and highly effective strategy could serve as a guideline for developing high-performance multifunctional wood composite with promising intelligent applications in performance visualization, environmental sensing, materials interactivity, information dual-encryption, local precision shape and color regulation, etc.

A Novel Flame-Retardant, Smoke-Suppressing, and Superhydrophobic Transparent Bamboo

Silica glass, known for its brittleness, weight, and non-biodegradable nature, faces challenges in finding suitable alternatives. Transparent wood, made by infusing polymers into wood, shows promise but is hindered by limited availability of wood in China and fire risks associated with its use. This study explores the potential of utilizing bamboo, which has a shorter growth cycle, as a valuable resource for developing flame-retardant, smoke-suppressing, and superhydrophobic transparent bamboo. A 3-layered flame-retardant barrier, composed of a top silane layer, an intermediate layer of SiO2 formed through hydrolysis-condensation of Na2SiO3 on the surface, and an inner layer of Na2SiO3, has been confirmed to be effective in reducing heat release, slowing flame spread, and inhibiting the release of combustible volatiles, toxic smoke, and CO. Compared to natural bamboo and other congeneric transparent products, the transparent bamboo displays remarkable superiority, with the majority of parameters being notably lower by an entire order of magnitude. It achieves a long ignition time of 116 s, low total heat release (0.7 MJ/m2), low total smoke production (0.063 m2), and low peak CO concentration (0.008 kg/kg). Moreover, when used as a substrate for perovskite solar cells, the transparent bamboo displays the potential to act as a light management layer, leading to a marked efficiency enhancement of 15.29%. The excellent features of transparent bamboo make it an enticing choice for future advancements in flame-retardant glasses and optical devices.

Facile and Widely Applicable Route to Self-Adaptive Emissivity Modulation: Energy-Saving Demonstration with Transparent Wood

The cooling power provided by radiative cooling is unwanted during cold hours. Therefore, self-adaptive regulation is desired for radiative cooling, especially in all-weather applications. However, current routes for radiative cooling regulation are constrained by substrates and complicated processing. Here, self-adaptive radiative cooling regulation on various potential substrates (transparent wood, PET, normal glass, and cement) was achieved by a Fabry-Perot structure consisting of a silver nanowires (AgNWs) bottom layer, PMMA spacer, and W-VO2 top layer. The emissivity-modulated transparent wood (EMTW) exhibits an emissivity contrast of 0.44 (ε8-13-L = ∼0.19 and ε8-13-H = ∼0.63), which thereby yields considerable energy savings across different climate zones. The emissivity contrast can be adjusted by varying the spinning parameters during the deposition process. Positive emissivity contrast was also achieved on three other industrially relevant substrates via this facile and widely applicable route. This proves the great significance of the approach to the promotion and wide adoption of radiative cooling regulation concept in the built environment.

Controllable hydrophilic/superhydrophobic patterned coatings for optical information encryption/decryption based on water-triggered opaque to translucent transition

Anti-counterfeiting technologies are crucial for securing the authenticity and proof of commodities, in which the optical information encryption/decryption has attracted extensive attention for its overriding advantages of visibility and convenience. Inspired by the unique transparency transformation phenomenon of Diphylleia grayi petals, a controllable hydrophilic/superhydrophobic patterned coating with water-triggered opaque to translucent transition is proposed through the construction of a superhydrophobic coating, subsequent air plasma etching under a mask, and final hydrophilic modification to introduce stable invisible patterns. The superhydrophobic region exhibits great water repellency with a water contact angle (WCA) at 157°, while the hydrophilic region quickly absorbs water with a WCA at 61°. The patterned coating presents an opaque state for the serious light scattering induced by the rough microstructure and large refractive index difference between the coating and air, while the hydrophilic patterns on the coating transform to translucent after water infiltration for the reduced roughness and close refractive indexes of the coating and water. The information revealing is rapid and reversible, and demonstrates heat and long-term stability and great reusability. The findings conceivably stand out as a new methodology to fabricate controllable superwettable coatings with optical information encryption/decryption capability for application in anti-counterfeiting.

Bioinspired structural hydrogels with highly ordered hierarchical orientations by flow-induced alignment of nanofibrils

Natural structural materials often possess unique combinations of strength and toughness resulting from their complex hierarchical assembly across multiple length scales. However, engineering such well-ordered structures in synthetic materials via a universal and scalable manner still poses a grand challenge. Herein, a simple yet versatile approach is proposed to design hierarchically structured hydrogels by flow-induced alignment of nanofibrils, without high time/energy consumption or cumbersome postprocessing. Highly aligned fibrous configuration and structural densification are successfully achieved in anisotropic hydrogels under ambient conditions, resulting in desired mechanical properties and damage-tolerant architectures, for example, strength of 14 ± 1 MPa, toughness of 154 ± 13 MJ m-3, and fracture energy of 153 ± 8 kJ m-2. Moreover, a hydrogel mesoporous framework can deliver ultra-fast and unidirectional water transport (maximum speed at 65.75 mm s-1), highlighting its potential for water purification. This scalable fabrication explores a promising strategy for developing bioinspired structural hydrogels, facilitating their practical applications in biomedical and engineering fields.

Mechanically strong, hydrostable, and biodegradable all-biobased transparent wood films with UV-blocking performance

Petroleum-based plastics are useful but they pose a great threat to the environment and human health. It is highly desirable yet challenging to develop sustainable structural materials with excellent mechanical and optical properties for plastic replacement. Here, we report a simple and efficient method to manufacture high-performance all-biobased structural materials from cellulosic wood skeleton (WS) and gelatin via oxidation and densification. Specifically, gelatin was grafted to the oxidized cellulose wood skeletons (DAWS) and then physically crosslinked via Tannic acid (TA), resulting in a significant enhancement of the material properties. Notably, only a mild pressure was applied during the drying process to form a densified TA/Gelatin/transparent wood film(TWF). The developed TA/Gelatin/TWF (thickness:100 ± 12 μm) exhibited a desirable combination of high strength (∼154.59 MPa), light transmittance (86.2 % at 600 nm), low haze (16.7 %), high water stability (wet strength: ∼130.13 MPa) and ultraviolet blocking efficacy which surpass most of the petroleum-based plastics. In addition, due to the all bio-based origins (wood and gelatin), TA/Gelatin/TWF are easily biodegradable under natural conditions, leading to less impact on the environment. These findings would hold promises for exploring high-quality all bio-based wood composites as eco-friendly alternatives to substitute plastics with wide applications, e.g. anti-counterfeiting, UV protection, and flexible electricals.

Coloration and Fire Retardancy of Transparent Wood Composites by Metal Ions

Transparent wood composites (TWs) offer the possibility of unique coloration effects. A colored transparent wood composite (C-TW) with enhanced fire retardancy was impregnated by metal ion solutions, followed by methyl methacrylate (MMA) impregnation and polymerization. Bleached birch wood with a preserved hierarchical structure acted as a host for metal ions. Cobalt, nickel, copper, and iron metal salts were used. The location and distribution of metal ions in C-TW as well as the mechanical performance, optical properties, and fire retardancy were investigated. The C-TW coloration is tunable by controlling the metal ion species and concentration. The metal ions reduced heat release rates and limited the production of smoke during forced combustion tests. The potential for scaled-up production was verified by fabricating samples with a dimension of 180 × 100 × 1 (l × b × h) mm3.

Farming on the Ocean via Desalination (FOOD)

Today, agricultural irrigation consumes the largest amount of freshwater globally, while humans are threatened by water scarcity. To eliminate the trade-off between hunger and thirst, here, we show off-grid maritime agriculture based on a floating solar-driven agro-desalination wooden dome. In this dome, part of the visible light is transmitted for photosynthesis, and the remaining solar energy drives solar desalination, providing enough water (>4 mm day-1) for irrigation. Based on this water-food synergy, the stages of germination and growth are demonstrated. This technology can, to a large extent, support food security and sustainable agriculture and, in principle, be used to create self-circulation systems at sea to help humans survive weather extremes such as floods and droughts.

Research Advances in Wood Composites in Applications of Industrial Wastewater Purification and Solar-Driven Seawater Desalination

In recent years, the ecosystem has been seriously affected by sewage discharge and oil spill accidents. A series of issues (such as the continuous pollution of the ecological environment and the imminent exhaustion of freshwater resources) are becoming more and more unmanageable, resulting in a crisis of water quality and quantity. Therefore, studies on industrial wastewater purification and solar-driven seawater desalination based on wood composites have been widely considered as an important development direction. This paper comprehensively analyzes and summarizes the applications of wood composites in the fields of solar-driven seawater desalination and polluted water purification. In particular, the present situation of industrial wastewater containing heavy metal ions, microorganisms, aromatic dyes and oil stains and related problems of solar-driven seawater desalination are comprehensively analyzed and summarized. Generally, functional nanomaterials are loaded into the wood cell wall, from which lignin and hemicellulose are selectively removed. Alternatively, functional groups are modified on the basis of the molecular structure of the wood microchannels. Due to its three-dimensional (3D) pore structure and low thermal conductivity, wood is an ideal substrate material for industrial wastewater purification and solar-driven seawater desalination. Based on the study of objective conditions such as the preparation process, modification method and selection of photothermal conversion materials, the performances of the wood composites in filtration, adsorption and seawater desalination are analyzed in detail. In addition, this work points out the problems and possible solutions in applying wood composites to industrial wastewater purification and solar-driven seawater desalination.

Perovskite-Coated Thermochromic Transparent Wood: A Novel Material for Smart Windows in Energy-Efficient and Sustainable Buildings

Transparent wood (TW) has emerged as a sustainable alternative to conventional glass as an energy-efficient window glazing material owing to its exceptional optical transparency and superior mechanical and thermal performances. However, it is challenging to develop the TW-based color-switching smart windows with both high optical performance and mechanical strengths. In this work, an optically switchable and mechanically robust perovskite-coated thermochromic transparent wood (PTTW) is developed for use as smart windows to achieve an effective solar modulation and thermal management. PTTW exhibits a substantial solar modulation ability Δτsol of 21.6% and a high clear-state luminous transmittance τlum of 78.0%, which enable an efficient thermal regulation while ensuring high visual clarity. PTTW also offers enhanced mechanical properties (i.e., tensile strength σtens = 71.4 MPa and flexural strength σflex = 93.1 MPa) and improved thermal properties [i.e., thermal conductivity K = 0.247 W/(m·K) and heat capacity C = 1.69 J/(g·°C)] compared to glass-based smart windows, as well as excellent performance stability (i.e., 200 heating-cooling cycles), manifesting its applicability in real building scenarios. In addition, PTTW also demonstrates a remarkable thermal-regulating performance (i.e., 5.44 °C indoor air temperature regulation) and an energy-saving potential (i.e., 12.9% heating, ventilation, and air conditioning energy savings) in Hong Kong. Overall, this study contributes to the progression toward energy-efficient and sustainable buildings.

From Biological Source to Energy Harvesting Device: Surface Protective Ionic Liquid Coatings for Electrical Performance Enhancement of Wood-Based Electronics

This study explores task-specific ionic liquids (TSILs) in smart floor systems, highlighting their strong electrical rectification abilities and previously established wood preservative properties. Two types of TSILs, featuring a "sweet" anion and a terpene-based cation, were used to treat selected wood samples, allowing for a comparison of their physical and electrical performance with untreated and commercially treated counterparts. Drop shape analysis and scanning electron microscopy were employed to evaluate the surface treatment before and after coating. Near-IR was used to confirm the presence of a surface modifier, and thermogravimetric analysis (TGA) was utilized to assess the thermal features of the treated samples. The different surface treatments resulted in varied triboelectric nanogenerator (TENG) parameters, with the molecular structure and size of the side chains being the key determining factors. The best results were achieved with TSILs, with the instantaneous voltage increasing by approximately five times and the highest voltage reaching 300 V under enhanced loading. This work provides fresh insights into the potential application spectrum of TSILs and opens up new avenues for directly utilizing tested ionic compounds in construction systems.

Transparent wood composite prepared from two commercially important tropical timber species

Transparent wood (TW) has garnered significant global attention due to its unique properties. In this study, TW composites were fabricated using two timber species of different density classes: Ailanthus triphysa (common name: Ailanthus wood) and Hevea brasiliensis (common name: Rubberwood). Sodium hydroxide (NaOH) and Hydrogen peroxide-based alkali method was used to modify the lignin in these veneer samples, producing a white cellulose template with a fully intact hierarchical cell structure. Subsequently, a cost-effective thermosetting unsaturated polyester resin (UPR) was infiltrated into the redesigned framework and polymerized to create rigid nanostructured transparent composites. High optical haze (of 94% and 89%) and favourable light transmittance of 59 and 55 percent were exhibited by the UPR-TW composites made from rubberwood and ailanthus wood, respectively. TW was characterised using Scanning electron microscopy and Fourier-transform infrared spectroscopy. The mechanical properties of TW were measured and compared with those of natural wood and pure-polymer. Furthermore, the anisotropic light diffusion behaviour displayed by TW in accordance with the fibre orientation indicates the utility of material as a potential light shaping device. Therefore, a cost-effective and commercially viable strategy to fabricate multipurpose TW composites using a combination of lesser-known timber species (LKTS) and UPR resin was successfully demonstrated.

Insulative Biobased Glaze from Wood Laminates Obtained by Self-Adhesion

The combination of optical transparency and mechanical strength is a highly desirable attribute of wood-based glazing materials. However, such properties are typically obtained by impregnation of the highly anisotropic wood with index-matching fossil-based polymers. In addition, the presence of hydrophilic cellulose leads to a limited water resistance. Herein, this work reports on an adhesive-free lamination that uses oxidation and densification to produce transparent all-biobased glazes. The latter are produced from multilayered structures, free of adhesives or filling polymers, simultaneously displaying high optical clarity and mechanical strength, in both dry and wet conditions. Specifically, high values of optical transmittance (≈85.4%), clarity (≈20% with low haze) at a thickness of ≈0.3 mm, and highly isotropic mechanical strength and water resistance (wet strength of ≈128.25 MPa) are obtained for insulative glazes exhibiting low thermal conductivity (0.27 W m-1 K-1 , almost four times lower than glass). The proposed strategy results in materials that are systematically tested, with the leading effects of self-adhesion induced by oxidation rationalized by ab initio molecular dynamics simulation. Overall, this work demonstrates wood-derived materials as promising solutions for energy-efficient and sustainable glazing applications.

Degradation performance of methylene blue in metal nanoparticle modified 3D mesoporous wood microchannels

Wood has a rich three-dimensional pore structure and many bottom-up nanochannels. However, the structure of wood itself has limited ability to adsorb dyes, so the effective combination of the unique structure of wood and Pd NPs was studied to achieve efficient degradation of dyes. First, the three-dimensional structure of natural wood is optimized by combining the complex pore structure of wood with Pd NPs to improve the contact process between the dye and Pd NPs. Then, Pd (II) ion can be well reduced to Pd NPs by wood lignin. In addition, Pd NPs can be fixed by hydroxyl groups on cellulose in wood. The flow state inside Pd NPs/wood film and the contact area between catalyst and dye were discussed in detail by hydrodynamic simulation, which filled the gap. It provides reference for composite structure. When Pd NPs/wood membrane was used to treat methylene blue (MB), the degradation efficiency was up to 96.7%, which was 90% higher than that of natural wood. Its TOF value was 1.82 molMB molPd-1min-1, which was higher than that in the previous literature. Therefore, the novelty of this study is that the mechanism of catalytic degradation of MB by Pd nanoparticles/wood composites is reported for the first time. The internal flow mode and contact condition of the new material are understood, which has a good application prospect.

Algal-based wood as a green and sustainable alternative for environmentally friendly & flexible electronic devices membrane bioreactor

Electronic are usually constructed from non-renewable, non-biodegradable, and hazardous materials. Due to the frequent upgrading or discarding of electronic devices, which contributes significantly to environmental pollution, there is a high demand for electronics made from renewable and biodegradable materials with less harmful components. To this end, due to their flexibility, strong mechanical, and optical properties, wood-based electronics have become very appealing as substrates especially for flexible electronics and optoelectronics. However, incorporating numerous features including high conductivity and transparency, flexibility, and mechanical robustness into an environmentally friendly electronic device remains very challenging. Herein, authors have provided the techniques used to fabricate sustainable wood based flexible electronics coupled with their chemical, mechanical, optical, thermal, thermomechanical, and surface properties for various applications. Additionally, the synthesis of a conductive ink based on lignin and the development of translucent wood as a substrate are covered. Future developments and broader applications of wood-based flexible materials are discussed in the final section of the study, with an emphasis on their potential in fields including wearable electronics, renewable energy, and biomedical devices. This research improves upon prior efforts by demonstrating new ways to simultaneously attain better mechanical and optical qualities and environmental sustainability.

Robust, Fire-Retardant, and Water-Resistant Wood/Polyimide Composite Aerogels with a Hierarchical Pore Structure for Thermal Insulation

The use of energy-saving materials is an effective strategy for decreasing energy consumption and carbon emission. Wood is a type of biomass material with a natural hierarchical structure, which results in its high thermal insulation. It has been widely used in construction. However, developing wood-based materials without flammability and dimensional instability is still a challenge. Herein, we developed a wood/polyimide composite aerogel with a well-preserved hierarchical pore structure and dense hydrogen bonds inside, resulting in its excellent chemical compatibility and strong interfacial interactions between its two components. This novel wood-based composite was fabricated by removing most hemicellulose and lignin from natural wood, followed by the fast impregnation using an 'in situ gel' process. The introduction of polyimide into delignified wood substantially improved its mechanical properties, with the compression resistance being improved by over five times. Notably, the thermal conductivity coefficient of the developed composite was approximately half that of natural wood. Furthermore, the composite exhibited excellent fire-retardancy, hydrophobicity, thermal insulation, and mechanical properties. This study provides a novel method for wood modification, which not only aids interfacial compatibility between wood and polyimide but also retains the properties of the two components. The developed composite can effectively reduce energy consumption, making it promising for practical and complex thermal insulation applications.

Advances in Sol-Gel-Based Superhydrophobic Coatings for Wood: A Review

As the focus of architecture, furniture, and other fields, wood has attracted extensive attention for its many advantages, such as environmental friendliness and excellent mechanical properties. Inspired by the wetting model of natural lotus leaves, researchers prepared superhydrophobic coatings with strong mechanical properties and good durability on the modified wood surface. The prepared superhydrophobic coating has achieved functions such as oil-water separation and self-cleaning. At present, some methods such as the sol-gel method, the etching method, graft copolymerization, and the layer-by-layer self-assembly method can be used to prepare superhydrophobic surfaces, which are widely used in biology, the textile industry, national defense, the military industry, and many other fields. However, most methods for preparing superhydrophobic coatings on wood surfaces are limited by reaction conditions and process control, with low coating preparation efficiency and insufficiently fine nanostructures. The sol-gel process is suitable for large-scale industrial production due to its simple preparation method, easy process control, and low cost. In this paper, the research progress on wood superhydrophobic coatings is summarized. Taking the sol-gel method with silicide as an example, the preparation methods of superhydrophobic coatings on wood surfaces under different acid-base catalysis processes are discussed in detail. The latest progress in the preparation of superhydrophobic coatings by the sol-gel method at home and abroad is reviewed, and the future development of superhydrophobic surfaces is prospected.

Transparent Wood Biocomposite of Well-Dispersed Dye Content for Fluorescence and Lasing Applications

Aggregation-induced quenching often restricts emissive performance of optically active solid materials with embedded fluorescent dyes. Delignified and nanoporous wood readily adsorbs organic dyes and is investigated as a host material for rhodamine 6G (R6G). High concentration of R6G (>35 mM) is achieved in delignified wood without any ground-state dye aggregation. To evaluate emissive performance, a solid-state random dye laser is prepared using the dye-doped wood substrates. The performance in terms of lasing threshold and efficiency was improved with increased dye content due to the ability of delignified wood to disperse R6G.

Wood xerogel for fabrication of high-performance transparent wood

Optically transparent wood has been fabricated by structure-retaining delignification of wood and subsequent infiltration of thermo- or photocurable polymer resins but still limited by the intrinsic low mesopore volume of the delignified wood. Here we report a facile approach to fabricate strong transparent wood composites using the wood xerogel which allows solvent-free infiltration of resin monomers into the wood cell wall under ambient conditions. The wood xerogel with high specific surface area (260 m² g^-1) and high mesopore volume (0.37 cm³ g^-1) is prepared by evaporative drying of delignified wood comprising fibrillated cell walls at ambient pressure. The mesoporous wood xerogel is compressible in the transverse direction and provides precise control of the microstructure, wood volume fraction, and mechanical properties for the transparent wood composites without compromising the optical transmittance. Transparent wood composites of large size and high wood volume fraction (50%) are successfully prepared, demonstrating potential scalability of the method.

Strong, flexible and UV-shielding composite polyvinyl alcohol films with wood cellulose skeleton and lignin nanoparticles

The development of high-performance composite films using biomass materials have become a sought-after direction. Herein, a green method to fabricate strong, flexible and UV-shielding biological composite film from wood cellulose skeleton (WCS), lignin nanoparticles (LNPs) and polyvinyl alcohol (PVA) was described. In the work, WCS and LNPs were prepared by chemical treatment of wood veneer and Enzymatic lignin, respectively. Then, WCS was infiltrated with the LNPs/PVA mixtures and dried to obtain composite films. WCS enhanced the mechanical properties of the composite films, the tensile stress reached to 85.8 MPa and the tensile strain reached to 6.39 %. The composite films with LNPs blocked over 98 % of UV-light, the water absorption decreased by 30 %, and the thermal stabilities were also improved. These findings would provide some references for exploring high quality biological composite films.

H2O2 Solution Steaming Combined Method to Cellulose Skeleton for Transparent Wood Infiltrated with Cellulose Acetate

Hydrogen peroxide (H2O2) steaming, a green and highly efficient delignification method, has been demonstrated to provide a wood skeleton with a very low content of residual lignin in the manufacturing of transparent wood. It usually requires a long reaction time and a large amount of H2O2 because the piece of wood is treated using steaming equipment. Herein, a H2O2 solution steaming method was developed for the highly efficient removal of lignin from wood. Specifically, several wood samples were simultaneously immersed in a hot H2O2 solution to obtain delignified wood with a relatively high content of residual lignin, which provided a high strength and preserved the cellulose skeleton. Subsequently, the delignified wood with a relatively high content of residual lignin was further treated with H2O2 steam to obtain a very low lignin delignified wood. Compared with the previous H2O2 steaming method, the reaction time and used H2O2 volume of the H2O2 solution steaming method was reduced by 37.3% and 52.7%, respectively. All-biomass transparent wood could be obtained by infiltrating the delignified wood with cellulose acetate, which showed both a high transmittance of 83.0% and a low thermal conductivity of 0.30 Wm−1K−1.

A comprehensive review of the synthesis strategies, properties, and applications of transparent wood as a renewable and sustainable resource

The uncertainties of the environment and the emission levels of nonrenewable resources have compelled humanity to develop sustainable energy savers and sustainable materials. One of the most abundant and versatile bio-based structural materials is wood. Wood has several promising advantages, including high toughness, low thermal conductivity, low density, high Young's modulus, biodegradability, and non-toxicity. Furthermore, while wood has many ecological and structural advantages, it does not meet optical transparency requirements. Transparent wood is ideal for use in various industries, including electronics, packaging, automotive, and construction, due to its high transparency, haze, and environmental friendliness. As a necessary consequence, current research on developing fine wood is summarized in this review. This review begins with an explanation of the history of fine wood. The concept and various synthesis strategies, such as delignification, refractive index measurement methods, and transparent lumber polymerization, are discussed. Approaches and techniques for the characterization of transparent wood are outlined, including microscopic, Fourier transform infrared (FTIR), and X-ray diffraction (XRD) analysis. Furthermore, the characterization, physical properties, mechanical properties, optical properties, and thermal conductivity of transparent wood are emphasized. Eventually, a brief overview of the various applications of fine wood is presented. The present review summarized the first necessary actions toward future transparent wood applications.

Emerging Engineered Wood for Building Applications

The building sector, including building operations and materials, was responsible for the emission of ∼11.9 gigatons of global energy-related CO₂ in 2020, accounting for 37% of the total CO₂ emissions, the largest share among different sectors. Lowering the carbon footprint of buildings requires the development of carbon-storage materials as well as novel designs that could enable multifunctional components to achieve widespread applications. Wood is one of the most abundant biomaterials on Earth and has been used for construction historically. Recent research breakthroughs on advanced engineered wood products epitomize this material's tremendous yet largely untapped potential for addressing global sustainability challenges. In this review, we explore recent developments in chemically modified wood that will produce a new generation of engineered wood products for building applications. Traditionally, engineered wood products have primarily had a structural purpose, but this review broadens the classification to encompass more aspects of building performance. We begin by providing multiscale design principles of wood products from a computational point of view, followed by discussion of the chemical modifications and structural engineering methods used to modify wood in terms of its mechanical, thermal, optical, and energy-related performance. Additionally, we explore life cycle assessment and techno-economic analysis tools for guiding future research toward environmentally friendly and economically feasible directions for engineered wood products. Finally, this review highlights the current challenges and perspectives on future directions in this research field. By leveraging these new wood-based technologies and analysis tools for the fabrication of carbon-storage materials, it is possible to design sustainable and carbon-negative buildings, which could have a significant impact on mitigating climate change.

Robust flexural performance and fracture behavior of TiO2 decorated densified bamboo as sustainable structural materials

High-performance, fast-growing natural materials with sustainable and functional features currently arouse significant attention. Here, facile processing, involving delignification, in situ hydrothermal synthesis of TiO₂ and pressure densification, is employed to transform natural bamboo into a high-performance structural material. The resulting TiO₂-decorated densified bamboo exhibits high flexural strength and elastic stiffness, with both properties more than double that of natural bamboo. Real-time acoustic emission reveals the key role of the TiO₂ nanoparticles in enhancing the flexural properties. The introduction of nanoscale TiO₂ is found to markedly increase the degree of oxidation and the formation of hydrogen bonds in bamboo materials, leading to extensive interfacial failure between the microfibers, a micro-fibrillation process that results in substantial energy consumption and high fracture resistance. This work furthers the strategy of the synthetic reinforcement of fast-growing natural materials, which could lead to the expanded applications of sustainable materials for high-performance structural applications.

Research Progress on the Improvement of Flame Retardancy, Hydrophobicity, and Antibacterial Properties of Wood Surfaces

Wood-based materials are multifunctional green and environmentally friendly natural construction materials, and are widely used in decorative building materials. For this reason, a lot of research has been carried out to develop new and innovative wood surface improvements and make wood more appealing through features such as fire-retardancy, hydrophobicity, and antibacterial properties. To improve the performance of wood, more and more attention is being paid to the functioning of the surface. Understanding and mastering technology to improve the surface functionality of wood opens up new possibilities for developing multifunctional and high-performance materials. Examples of these techniques are ion crosslinking modification and coating modification. Researchers have been trying to make wooden surfaces more practical for the past century. This study has gradually gained popularity in the field of wood material science over the last 10 years. This paper provides an experimental reference for research on wood surface functionalization and summarizes the most current advancements in hydrophobic, antibacterial, and flame-retardant research on wood surfaces.

Flame-Retardant and Form-Stable Phase-Change Composites Based on Phytic Acid/ZnO-Decorated Surface-Carbonized Delignified Wood with Superior Solar-Thermal Conversion Efficiency and Improved Thermal Conductivity

In order to efficiently exploit solar-thermal energy, it is essential to develop form-stable phase-change material (PCM) composites simultaneously with superior solar-thermal storage efficiency, excellent flame retardancy, and improved thermal conductivity. Herein, phytic acid (PA)-modified, zinc oxide-deposited, and surface-carbonized delignified woods (PZCDWs) were constructed by alkaline boiling, PA modification, ZnO deposition, and surface carbonization. Then, novel form-stable PCMs (PZPCMs) with superior solar-thermal storage efficiency, excellent flame retardancy, and improved thermal conductivity were fabricated by impregnating n-docosane into PZCDWs under vacuum. The PZCDW aerogels can well support the n-docosane and overcome liquid leakage owing to their superior surface tension and strong capillary force. Differential scanning calorimetry results showed that PZPCMs possessed superior n-docosane encapsulation yield and high phase-change enthalpy (185.2-213.1 J/g). Decorating delignified wood by surface carbonization and ZnO deposition significantly improved the solar-thermal conversion efficiency (up to 86.2%) and thermal conductivity (193.3% increased) of PCM composites. Furthermore, with the introduction of PA into PZPCMs, the peak heat release rate and total heat release of the PCM composites decreased considerably, indicating the enhanced flame retardancy of PZPCMs. In conclusion, the novel renewable wood-based PCM composites demonstrate promising potential in solar energy harnessing and thermal modulation technologies.

Research and Application of Biomass-Based Wood Flame Retardants: A Review

Wood is widely used as a construction material due to its many advantages, such as good mechanical properties, low production costs, and renewability. However, its flammability limits its use in construction. To solve the problem of wood flammability, the most common method to improve the fire safety of wood is to modify the wood by deep impregnation or surface coating with flame retardants. Therefore, many researchers have found that environmentally friendly and low-cost biomass materials can be used as a source of green flame retardants. Two aspects of biomass-based intumescent flame retardants are summarized in this paper. On the one hand, biomass is used as one of the three sources or as a flame-retardant synergist in combination with other flame retardants, which are called composite biomass intumescent flame retardants. On the other hand, biomass is used alone as a feedstock to produce all-biomass intumescent flame retardants. In addition, the potential of biomass-based materials as an environmentally friendly and low-cost FR source to produce high-performance biomass-based flame retardants with improved technology was also discussed in detail. The development of biomass-based intumescent flame retardants represents a viable and promising approach for the efficient and environmentally friendly production of biomass-based flame retardants.

Flexible Wood Enhanced Poly(acrylic acid-co-acrylamide)/Quaternized Gelatin Hydrogel Electrolytes for High-Energy-Density Supercapacitors

Hydrogels with good flexibility and strong hydrophilicity can be candidates for excellent flexible electrolyte materials. However, the poor structural stability, uncontrollable swelling, and lower potential window of hydrogel electrolytes need to be improved. This work combined quaternized gelatin with cross-linked poly(acrylic acid-co-acrylamide) to form a semi-interpenetrating network and gelatinized in situ in a flexible porous wood skeleton. The flexible wood (FW) skeleton enhances the hydrogel and limits the swelling of the hydrogel. In addition, quaternary ammonium groups and FW act synergistically to provide the composite hydrogel electrolyte with a high ionic conductivity of 5.57 × 10^-2 S cm^-1. The composite hydrogel electrolyte can enable the flexible supercapacitor to operate safely in a potential window of 0-2 V. The optimized supercapacitor has a high specific capacitance of 286.74 F g^-1 and provides an outstanding energy density of 39.09 W h kg^-1. The flexible supercapacitor shows a capacitance retention of up to 94.6% after 10,000 charge-discharge cycles, indicating dramatic cycling stability. Simultaneously, a capacitance retention of nearly 90% can be maintained by the flexible supercapacitor after 180° bends for 1000 times. A viable idea for developing high-performance hydrogel electrolytes and flexible supercapacitors is provided in this research.

Potential new material for optical fiber: Preparation and characterization of transparent fiber based on natural cellulosic fiber and epoxy

In order to reduce the dependence on fossil energy products, natural fiber/polymer hybrid composites have been increasingly researched. The high price of the quartz optical fibers and glass optical fibers has greatly inspired researchers to engage in the research on polymer optical fibers. Herein, transparent fibers based on plant fibers were innovatively prepared for the first time by delignification and impregnating epoxy diluted with acetone. The epoxy improved the thermal stability of the fiber without deteriorating its mechanical properties, and also endowed the fiber with the property of transparency. The tensile strength of transparent fibers of three diameters were 34.5, 58.6 and 100.3 MPa, respectively and the corresponding Young's modulus reached 1.1, 1.7 and 2.3 GPa, respectively. In addition, the light-conducting properties of transparent fibers were displayed with a green laser and the fibers displayed good light transmission along the fiber growth direction. Transparent fibers are expected to be used in optical fibers because of their high thermal stability, good mechanical properties and light-conducting properties.

Flexible Janus wood membrane with asymmetric wettability for high-efficient switchable oil/water emulsion separation

Janus membranes have attracted much attention for switchable oil/water separation because they have opposite wetting behavior on each side. However, it remains a challenge to fabricate Janus membranes with asymmetric wettability from biomass by simple methods. Herein, we prepared a flexible Janus wood (JW) membrane by cutting the natural wood along the longitudinal direction, followed by a facile top-down approach. The hydrophobic lignin was removed from the wood to prepare a highly porous and superhydrophilic wood (SW) with underwater superoleophobicity. Then, one side of the SW was sprayed with a mixture of 1H,1H,2H,2H-perfluorooctyltrichlorosilane/SiO2 nanoparticles to form a superhydrophobic surface that hardly affected the wettability of the other side. The obtained JW membrane maintains its selective wettability in harsh environments owing to its durability and stability. Furthermore, it has a switchable, high separation efficiency of >99% for both oil-in-water and water-in-oil emulsions, which can be attributed to the unique wettability and hierarchical micro/nano structure of the JW membrane. Notably, the three-dimensional interconnected micro/nanochannels (pits and nanopores) of the JW membrane are beneficial to the size-sieving effect during emulsion separation. At the same time, the layered channels (tracheids and vessels) enable multiple separations. JW membrane is sustainable, inexpensive, stable, and easy to manufacture, providing more implications for the innovation of biomass-based Janus separation materials in industrial wastewater treatment.

Multilayer Transparent Wood with Log Color Composed of Different Tree Species

In this experiment, a multilayer transparent wood with different surface and core layers of tree species was prepared, which has log color. The purpose is to explore the feasibility of preparing multilayer transparent wood from different tree species as raw materials. The experiment first removed partial lignin from the veneers to obtain the wood templates. Then, tree species with rich texture and color as the surface layer wood and tree species with less texture as the core and bottom wood were selected. Finally, the resin-impregnated wood templates were laminated and dried to obtain samples. The results show that wood fiber and resin have good coordination, and the laminated structure is conducive to weakening the anisotropy of transparent wood. Transparent wood has better mechanical property and hydrophobicity than original wood. The above shows that this transparent wood has a large elastic mechanism for the selection of tree species, and the thickness optics can be adjusted according to tree species and wood layers. It has good application prospects in interior decoration or as outdoor structural material.

Transparent Wood-Based Materials: Current State-of-the-Art and Future Perspectives

Human history is largely characterized by the massive use of wood, the most well-known natural composite material, possessing unique thermal, mechanical, and environmental features that make it suitable for several applications, ranging from civil engineering, art, and household uses, to business uses (including furniture, stationery, shipbuilding, and fuel). Further, as a renewable and recyclable biomass, wood perfectly matches the current circular economy concept. However, because of its structure and composition, wood is not transparent: therefore, the possibility of removing the embedded lignin, hence limiting the light-scattering phenomena, has been investigated over the last ten to fifteen years, hence obtaining the so-called "transparent wood (TW)". This latter represents an up-to-date key material, as it can be utilized as obtained or further functionalized, combining the transparency with other features (such as flame retardance, energy storage ability, and environmental protection, among others), which widen the potential (and practical) applications of wood. The present manuscript aims at summarizing first the current methods employed for obtaining transparent wood, and then the latest achievements concerning the properties of transparent wood, providing the reader with some perspectives about its novel functionalizations and applications.

Ultrathin and Ultrastrong Kevlar Aramid Nanofiber Membranes for Highly Stable Osmotic Energy Conversion

An ion-selective membrane can directly convert the osmotic energy to electricity through reverse electrodialysis. However, developing an advanced membrane that simultaneously possesses high power density, excellent mechanical strength, and convenient large-scale production for practical osmotic energy conversion, remains challenging. Here, the fabrication of ultrathin and ultrastrong Kevlar aramid nanofiber (KANF) membranes with interconnected three-dimensional (3D) nanofluidic channels via a simple blade coating method is reported. The negatively charged 3D nanochannels show typical surface-charge-governed nanofluidic ion transport and exhibit excellent cation selectivity. When applied to osmotic energy conversion, the power density of the KANF membrane-based generator reaches 4.8 W m^-2 (seawater/river water) and can be further increased to 13.8 W m^-2 at 328 K, which are higher than most of the state-of-the-art membranes. Importantly, a 4-µm-thickness KANF membrane shows ultrahigh tensile strength (565 MPa) and Young's modulus (25 GPa). This generator also exhibits ultralong stability over 120 days, showing great potential in practical energy conversions.

Effect of Lignin Removal on the Hygroscopicity of PMMA/Wood Composites

Wood delignification can provide a wood-based template with sufficient pore volume for polymer/wood composites. At the same time, delignification is conducive to the penetration of polymer into the wood cell wall, which is of great significance to improve the function and performance of composites. However, lignin is the main chemical component in wood. The removal of lignin will inevitably lead to the change of the wood’s physical properties, including the hygroscopicity of the wood. In this study, prepolymerized methyl methacrylate (MMA) impregnated delignified wood (DW) was used to obtain polymerized methyl methacrylate/delignified wood (PMMA/DW) composites with different lignin removal. The effect of lignin removal on the hygroscopicity of the composites is discussed. The results of nitrogen adsorption showed that the DW could adsorb more nitrogen than the original wood, and the amount of nitrogen adsorption gradually increased with the improvement of the processing degree. After filling with PMMA, the adsorption amount of nitrogen was greatly reduced. The results of the BET analysis showed that delignification promoted the distribution of PMMA in the pores of the wood cell wall. When lignin was almost completely removed, all mesopores in the cell wall were filled with PMMA. The results of the moisture absorption analysis isotherm curve showed that the moisture absorption content of the wood was positively correlated with the amount of lignin removed, and the moisture absorption content of the PMMA/DW composite was negatively correlated with the amount of lignin removed. The hygroscopic data were further analyzed using the Hailwood–Horrobin model. The results showed that the mole number of adsorbable or hydratable sites of the DW increased with the increase of lignin removal, and the situation of the PMMA/DW composites was just the opposite. In addition, after delignification, the dissolved water content and hydrated water content of the DW increased, and the increase was related to the delignification strength. The increase of dissolved water content indicates that the removal of lignin promotes the production of more volume in the cell wall, which provides space for the adsorption of multilayer water. After MMA in situ polymerization, the hydration and dissolved water content of the PMMA/DW decreased significantly, and the dissolved water content decreased even more significantly. The fitting curves of the H-H model and GDW model for the experimental data points of the differently treated samples were similar. The removal of lignin led to the increase of the w value, indicating that the ratio of water molecules adsorbed in the first layer of DW to the second layer increased, and the removal of lignin resulted in the enhancement of wood hygroscopicity; the opposite was true for the PMMA/DW.

Ultraviolet-Assisted Modified Delignified Wood with High Transparency

The substrate of solar cells with high haze, transparent, flexible, green and low coatings will be needed in the future. This paper reports a method for ultraviolet-assisted delignification of wood in an alkaline solution environment to improve the transmittance of “transparent wood”. Scanning electron microscope (SEM), X-ray diffraction image (XRD), Fourier transform infrared (FTIR) spectroscopy and transmittance-haze and chemical composition analysis were used to explore the mechanisms underlying the effect of ultraviolet-assisted lignin modification on the optical properties of “transparent wood”. The results show that UV-assisted delignification accelerates the rate of removal of lignin and chromogenic groups, which in turn improves the optical properties of the “transparent wood”, with UV-assisted lignin modification for 2 h increasing the light transmission of the “transparent wood” by 20%. UV-assisted delignification for 4 h and impregnation resulted in “transparent wood” with a transparency of 71% and a haze of 90%. This report provides a rapid and easy method to prepare high-quality “transparent wood”. The “transparent wood” with high transmittance and high haze is a potential candidate for transparent solar substrates. Meanwhile, this method is enlightening for high quality, fast and green preparation of other derived functional materials based on lignin wood.

Review of Wood Modification and Wood Functionalization Technologies

Wood modifications are becoming popular as a way to enhance the performance of wood, either to make it more durable, improve the performance of wood, or give it new functionality as a multifunctional or smart material. While wood modifications have been examined since the early 1900s, the topic has become a dominant area of study in wood science over the past decade. This review summarizes recent advances and provides future perspective on a selection of wood modifications, i.e., the methods that are currently commercialized (acetylation, furfurylation, and thermal modification), a rediscovered ancient practice (charring), a family of polymerization modifications that have so far made it to the pilot scale, and examples of novel wood-based functional materials explored at laboratory scale.

Changes in Chemical and Thermal Properties of Bamboo after Delignification Treatment

Bamboo delignification is a common method for studying its functional value-added applications. In this study, bamboo samples were delignified by treatment with sodium chlorite. The effects of this treatment on the bamboo’s microstructure, surface chemical composition, and pyrolysis behaviour were evaluated. Field-emission scanning electron microscopy (FE-SEM), Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were conducted to evaluate these parameters. The FTIR results demonstrated that the lignin peak decreased or disappeared, and some hemicellulose peaks decreased, indicating that sodium chlorite treatment effectively removed lignin and partly decomposed hemicellulose, although cellulose was less affected. The XPS results showed that, after treatment, the oxygen-to-carbon atomic ratio of delignified bamboo increased from 0.34 to 0.45, indicating a lack of lignin. XRD revealed increased crystallinity in delignified bamboo. Further pyrolysis analysis of treated and untreated bamboo showed that, although the pyrolysis stage of the delignified bamboo did not change, the maximum thermal degradation rate (R_max) and its corresponding temperature (from 353.78 to 315.62 °C) decreased significantly, indicating that the pyrolysis intensity of the bamboo was weakened after delignification. Overall, this study showed that delignified bamboo develops loose surfaces, increased pores, and noticeable fibres, indicating that alkali-treated bamboo has promising application potential due to its novel and specific functionalities.

Utilization of Wood Flour from White Oak Branches as Reinforcement in a Polypropylene Matrix: Physical and Mechanical Characterization

Compared to other fibrous materials, plant fibers can act as a reinforcement in plastics due to their relatively high strength and rigidity, low cost, low density, biodegradability, and renewability. In this context, this study examines the effect of the particle size and content of white oak wood flour (Quercus laeta Liemb), obtained from its branches, on the properties of commercial polypropylene. In Mexico, wood from the branches of Quercus laeta Liemb is barely utilized despite its abundance and viability. The main objective of this study is to demonstrate that this waste material can be exploited to prepare useful materials, in this case composites with competitive properties. Tensile and flexural tests, as well as impact strength and melt flow index were evaluated. In addition, density and water absorption capacity were also tested. Results showed that the water absorption increased with the incorporation of wood particles. Mechanical properties were strongly influenced by particle content. A reduction in elongation and strength was observed, while Young’s modulus and flexural modulus increased with the incorporation of wood particles. Impact strength increased with particle size and particle content.