Boosting solar steam generation by photothermal enhanced polydopamine/wood composites

Robust mussel-inspired superhydrophobic sponge with eco-friendly photothermal effect for crude oil/seawater separation

Frequent oil spills have significant implications for the preservation of ecological balance. However, conventional superhydrophobic materials are limited to organic solvent separation, lacking the ability to undergo thermal conversion. In response to these challenges, photothermal materials have emerged as a promising, environmentally friendly, and cost-effective solution. These materials utilize solar energy as a constant power source to effectively reduce the viscosity of crude oil without the need for additional energy input. This work presents the self-assembly of titanium nitride/polydopamine (TiN/PDA) nanoparticles using hydrolytic methyltrimethoxysilane (MTMS) on the polyurethane (PU) sponge and subsequently dip-coats this sponge with polydimethylsiloxane (PDMS). The TiN nanoparticles act as a photothermal medium, while the PDA coating exhibits a photothermal synergistic effect on TiN nanoparticles. Additionally, the PDA coating demonstrates strong adhesion on the PU sponge through chemical bonding with MTMS, as confirmed by density functional theory (DFT). Furthermore, the superhydrophobic sponges process exceptional mechanical or chemical stability in harsh environments, thanks to the dual protective mechanisms provided by MTMS and PDMS. Particularly important, the excellent photothermal conversion efficiency of this material results in a maximum temperature of 99.4 °C being achieved within 3 min and a stable heating performance of over 99.0 °C across 10 cycles under a standard sunlight intensity. These superhydrophobic sponges can be effectively utilized for continuous vacuum-assisted separation of crude oil/seawater, enabling rapid adsorption and purification in oceanic environments.

Optimizing physico-chemical properties of hierarchical ZnO/TiO2 nano-film by the novel heating method for photocatalytic degradation of antibiotics and dye

The design of semiconductor catalysts with excellent photocatalytic properties, stability, recyclability, and good separation for the treatment of polluted water is still challenging. In this paper, the ZnO/TiO2 nano-thin films were fabricated using the magnetron sputtering technique and then heating the underlying ZnO layer and the upper TiO2 layer for their respective optimal heating time, i. e. heating ZnO for 3 h and heating TiO2 for 2 h. The as-prepared films were characterized. The results show that the preferred growth of TiO2 grains along the [001] axis, relatively large specific surface area, and increased amounts of surface oxygen vacancies (OVs) were induced to the heterojunction catalysts through this optimized heating strategy, which boosts the photocatalytic activity of ZnO/TiO2 nano-film. The degradation experiment inndicates that the ciprofloxacin (CIP) removal efficiency can reach 97.3% in 2 h duration, which was higher than that of the samples annealed for the same periods. Meanwhile, the prepared ZnO/TiO2 photocatalytic film exhibited favorable stability of 95.5% degradation efficiency after the fourth run and general applicability for the photodegradation of various contantains, whih removed 99.5% of ofloxacin (OFX) and 77.6% of tetracycline (TC) in 2 h and 94.1% of Rhodamine B (RhB) in 1 h. This work is expected to yields a novel insight into the production of heterojunction photocatalysts with excellen ability for photocatalytic degradation of pollutants in the practical industry.

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.

Development of Active Antibacterial CEO/CS@PLA Nonwovens and the Application on Food Preservation

The biodegradable activity antibacterial materials have been widely applied on food preservation because they not only protect foods from pathogenic attacks but also relieve environmental pollution. Biodegradable melt-blown nonwovens (MB) have several advantages over the other materials in terms of a simpler and more environmentally friendly fabrication process, higher specific surface area, and lower cost. Herein, polylactic acid (PLA) MB is first modified by polydopamine (PDA) to activate the surface. Then, chitosan (CS) and cinnamon essential oil (CEO) are used to decorate the surface of the modified PLA MB via a simple one-pot method to prepare CEO/CS@PLA MB with different CEO contents. Compared with PLA MB, CEO/CS@PLA MB had a rougher surface and larger average fiber diameter, while the average pore diameter and air permeability reduced. The input of CEO led to a decrease in the tensile strength of CEO/CS@PLA MB and an obvious increase in the elongation at break. The combination of CS and CEO shows excellent synergistic antibacterial effect. The antibacterial efficiencies of CEO/CS@PLA MB against Escherichia coli and Staphylococcus aureus enhance with the increase of the CEO content. When the weight ratio of CS to CEO is 1:2, the antibacterial efficiencies of CEO2/CS@PLA MB against E. coli and S. aureus are 99.98 and 99.99%, respectively. When being applied to the preservation of fresh strawberry, CEO2/CS@PLA MB can effectively inhibit the microbial growth in strawberry and reduce decay, which extends the shelf time of strawberry.

Nanocellulose-based composite aerogels toward the environmental protection: Preparation, modification and applications

Nanocellulose aerogel has the advantages of porosity, low density and high specific surface area, which can effectively realize the adsorption and treatment of wastewater waste gas. The methods of preparing nanocellulose mainly include mechanical, chemical and biological methods. Nanocellulose is formed into nanocellulose aerogel after gelation, solvent replacement and drying processes. Based on the advantages of easy modification of nanocellulose aerogels, nanocellulose aerogels can be functionalized with conductive fillers, reinforcing fillers and other materials to give nanocellulose aerogels in electrical, mechanical and other properties. Through functionalization, the properties of nanocellulose composite aerogel such as hydrophobicity and adsorption are improved, and the aerogel is endowed with the ability of electrical conductivity and electromagnetic shielding. Through functionalization, the applicability and general applicability of nanocellulose composite aerogel in the field of environmental protection are improved. In this paper, the preparation and functional modification methods of nanocellulose aerogels are reviewed, and the application prospects of nanocellulose composite aerogels in common environmental protection fields such as dye adsorption, heavy metal ion adsorption, gas adsorption, electromagnetic shielding, and oil-water separation are specifically reviewed, and new solutions are proposed.

Amyloid Fibers Increase Free Radicals of Synthetic Melanin

Functional amyloid fibers are crucial in melanogenesis, but their roles are incompletely understood. In particular, their relationship with intrinsic spin characters of melanin remains unexplored. Here, we show that adding an amyloid scaffold greatly augments the spin density in synthetic melanin. It also brings about concurrent alterations in water dispersibility, bandgaps, and radical scavenging properties of the synthetic melanin, which facilitates its applications in solar water remediation and protection of human keratinocytes from UV irradiation. This work provides implications in the unrevealed role of functional amyloid in melanogenesis and in the origin of the superiority of natural melanin toward its synthetic variants in terms of the spin-related properties.

D-A Structured High-Performance Photothermal/Photodynamic Thionin-Synthetic Melanin Nanoparticles for Rapid Bactericidal and Wound Healing Effects

Synthesized melanin nanoparticles (SMNPs) are used as advanced photothermal materials. However, their internal structures are complex and disordered, and tuning the photothermal performance of nanoparticles is still a hot spot of concern. This article presents thionin (Th)-doped SMNPs, namely Th-SMNPs, which are the first SMNPs formed using the one-pot polymerization of Th with Levodopa. Th can undergo Michael addition and Schiff base reaction between indole dihydroxy/indolequinone and their oligomers to form donor-acceptor pairs in the structure to modulate the photothermal performance of SMNPs. Structural and spectroscopic analyses and density functional theory simulations further confirm the existence of the donor-acceptor structure. Th-SMNPs exhibit excellent total photothermal efficiency (34.49%) in the near-infrared region (808 nm), which is a 60% improvement compared to SMNPs. This allows Th-SMNPs to exhibit excellent photothermal performance at low power 808 nm laser irradiation. Meanwhile, Th not only enhances the photothermal properties of SMNPs, but also imparts photodynamic effects to SMNPs. Th-SMNPs can produce 1 O2 under 660 nm laser irradiation. A dual-function photothermal and photodynamic textile named Th-SMNPs@cotton is constructed based on Th-SMNPs, which can act as a rapid photothermal/photodynamic sterilization and is promising for wound healing treatment of bacterial infections under low-power dual laser irradiation.

Inspired by Wood: Thick Electrodes for Supercapacitors

The emergence and development of thick electrodes provide an efficient way for the high-energy-density supercapacitor design. Wood is a kind of biomass material with porous hierarchical structure, which has the characteristics of a straight channel, uniform pore structure, good mechanical strength, and easy processing. The wood-inspired low-tortuosity and vertically aligned channel architecture are highly suitable for the construction of thick electrochemical supcapacitor electrodes with high energy densities. This review summarizes the design concepts and processing parameters of thick electrode supercapacitors inspired by natural woods, including wood-based pore structural design regulation, electric double layer capacitances (EDLCs)/pseudocapacitance construction, and electrical conductivity optimization. In addition, the optimization strategies for preparing thick electrodes with wood-like structures (e.g., 3D printing, freeze-drying, and aligned-low tortuosity channels) are also discussed in detail. Further, this review presents current challenges and future trends in the design of thick electrodes for supercapacitors with wood-inspired pore structures. As a guideline, the brilliant blueprint optimization will promote sustainable development of wood-inspired structure design for thick electrodes and broaden the application scopes.

Oxidation of cellulose molecules toward delignified oxidated hot-pressed wood with improved mechanical properties

Wooden building materials have advantages in terms of biodegradability, non-toxicity, pollution-free and recycling. Currently, applications of natural wood are extremely limited because of low density, low strength and toughness. Therefore, we reported an effective modification strategy with nano-scale cellulose nanofibrils design to prepare a synergistically enhanced cellulosic material. Via three steps: i) the secondary alcohol hydroxyl groups in C₂, C₃ position were cut; ii) oxidize the hydroxyl group at C₂, C₃ position to achieve dialdehyde cellulose; and iii) oxidized again to obtain dicarboxylic cellulose. Subsequently, thanks to the regulation of the average moisture content, the moisture content in the wood surface and subsurface increased in a short time. The wood softening layer contributes to the hotpressing treatment of the wood. The mechanical properties and dimensionality have been greatly improved. The obtained delignified oxidated hot-pressed wood with 0.55 mmol/g carboxyl group content demonstrates excellent strength of 328.8 ± 7.43 MPa and Young's modulus of 8.1 ± 0.14 GPa, which is twice than that of natural wood. Delignified oxidated hot-pressed wood also shows exceptional toughness of 8.3 ± 0.28 MJ/m³. Other than that, the shore hardness indicates 0.55 mmol/g carboxylic group, which could increase the hardness at the wood surface hardness to 72.5 ± 4.29°.

High Value Utilization of Waste Wood toward Porous and Lightweight Carbon Monolith with EMI Shielding, Heat Insulation and Mechanical Properties

With the increasing pollution of electromagnetic (EM) radiation, it is necessary to develop low-cost, renewable electromagnetic interference (EMI) shielding materials. Herein, wood-derived carbon (WC) materials for EMI shielding are prepared by one-step carbonization of renewable wood. With the increase in carbonization temperature, the conductivity and EMI performance of WC increase gradually. At the same carbonization temperature, the denser WC has better conductivity and higher EMI performance. In addition, due to the layered superimposed conductive channel structure, the WC in the vertical-section shows better EMI shielding performance than that in the cross-section. After excluding the influence of thickness and density, the specific EMI shielding effectiveness (SSE/t) value can be calculated to further optimize tree species. We further discuss the mechanism of the influence of the microstructure of WC on its EMI shielding properties. In addition, the lightweight WC EMI material also has good hydrophobicity and heat insulation properties, as well as good mechanical properties.

A melanin-inspired robust aerogel for multifunctional water remediation

Solar-driven vapor generation has emerged as a promising wastewater remediation technology for clean water production. However, the complicated and diversified contaminants in wastewater still restrict its practical applications. Herein, inspired by the melanin in nature, a robust aerogel was facilely fabricated for multifunctional water remediation via a one-pot condensation copolymerization of 5,6-dihydroxyindole and formaldehyde. Benefiting from the superhydrophilicity, underwater superoleophobicity, and synergistic coordination effects, the resulting aerogel not only showed excellent performances in underwater oil resistance and oil-water separation ability, but also removed organic dyes and heavy metal ions contaminants in wastewater simultaneously. Moreover, owing to its admirable light harvesting capacity and porous microstructure for fast water transportation, the aerogel-based evaporator exhibited an excellent evaporation rate of 1.42 kg m^-2 h^-1 with a 91% evaporation efficiency under 1 sun illumination, which can be reused for long-term water evaporation. Note that such a stable evaporation rate could be maintained even in wastewater containing complex multicomponent contaminants. Outdoor evaporation experiments for lotus pond wastewater under natural sunlight also proved its great potential in practical applications. All those promising features of this all-in-one melanin-inspired aerogel may provide new strategies for the development of robust photothermal devices for multifunctional solar-driven water remediation.

Collaboration of two-star nanomaterials: The applications of nanocellulose-based metal organic frameworks composites

Nanocellulose, as the star nanomaterial in carbohydrate polymers, has excellent mechanical properties, biodegradability, and easy chemical modification. However, further practical applications of nanocellulose are limited by their inadequate functionalization. Metal-organic frameworks (MOFs), as the star nanomaterial in functional polymers, have a large surface area, high porosity, and adjustable structure. The collaboration of nanocellulose and MOFs is a desirable strategy to make composites especially interesting for multifunctional and multi-field applications. What sparks will be produced by the collaboration of two-star nanomaterials? In this review article, we highlight an up-to-date overview of nanocellulose-based MOFs composites. The sewage treatment, gas separation, energy storage, and biomedical applications are mainly summarized. Finally, the challenges and research trends of nanocellulose-based MOFs composites are prospected. We hope this review may provide a valuable reference for the development and applications of carbohydrate polymer composites soon.

Remotely Controlled Light/Electric/Magnetic Multiresponsive Hydrogel for Fast Actuations

As a kind of soft smart material, hydrogel actuators have extensive development prospects, but it is still difficult for these actuators to integrate multiresponsiveness, multiple remote actuation, high strength, fast responsiveness, and programmable complex deformation. Herein, we have explored an anisotropic bilayer hydrogel actuator with an Fe3O4/co-poly(isopropylacrylamide-4-benzoylphenyl acrylate) [Fe3O4/P(NIPAM-ABP)] active layer and an isotropic conductive adhesive (ICAs) passive layer based on the layer-by-layer method. Benefiting from the fibrosis and porosity of the Fe3O4/P(NIPAM-ABP) hydrogel, the ICAs-Fe3O4/P(NIPAM-ABP) hydrogel actuator has excellent mechanical strength (tensile strength of 3.1 ± 0.3 MPa) and response speed (temperature (45 °C): bending speed of 2400.3°/s; near-infrared (NIR) light: bending speed of 356.4°/s; electricity (2 V): bending speed of 180°/s; water (10 °C): recovery speed of 30.0°/s). In addition, the good photothermal properties and magnetic conductivity of Fe3O4 nanoparticles provide precise remotely controllable light- and magnetic-actuated properties for the hydrogel actuator. The Ag microsheets with excellent conductivity (1.4 × 104 S/cm) provide remotely controllable electrical-actuated property for the hydrogel actuator. Combined with the responsiveness of P(NIPAM-ABP), the actuator can achieve short-range actuation including temperature-, ethanol-, and salt-responses. More importantly, it can achieve remote actuation including light, electrical, and magnetic responses. Finally, the Fe3O4/P(NIPAM-ABP) fibers can provide excellent anisotropic structures for the actuator to achieve precise deformational programmability. Inspired by some phenomena in nature, several actuating devices with the above characteristics have been successfully developed. This study can provide a general method for multifunctional anisotropic hydrogel actuators and will provide a new strategy for exploring smart materials suitable for complex bioinspired systems.

Waste sawdust-based composite as an interfacial evaporator for efficient solar steam generation

Interfacial evaporation is the technology of localizing heat energy at the air-water interface and is used for getting potable water from salty or seawater effectively. In this work, we introduce a novel interfacial evaporator by blending different weight ratios of waste sawdust (1 g, 2 g, 3 g and 4 g) with bisphenol-A epoxy resin (LY556) and triethyltetramine hardener (HY951). The fabricated epoxy hardener sawdust (EHS) composite material was subjected to various characterizations for the possibility of using it in solar steam generation. Consequently, EHS displayed high light absorption, amorphous structure, functional groups, and large number of pores. The main objective of the study was to investigate interfacial solar steam generation with and without interfacial evaporators (EHS-1g, EHS-2g, EHS-3g, and EHS-4g) under indoor conditions. The maximum mass loss of water, evaporation rate and evaporation efficiency were found to be 4.5 g, 1.398 kg m^-2 h^-1, and 92.99%, respectively, for the EHS-4g evaporator. The salinity of the distilled condensed water was measured and was below the WHO standards. The results are due to (i) the large number of cross-linked porous structures used to permeate water at the evaporative surface by capillary action, (ii) low thermal conductivity of the composite that offers an efficient broad and strong light absorption, and (iii) existence of a larger hydraulic diameter and small tortuosity of pores, which reduces the salt ion penetration distance and dispatch back to bulk water.

A robust and 3D-printed solar evaporator based on naturally occurring molecules

The interfacial solar desalination has been considered a promising method to address the worldwide water crisis without sophisticated infrastructures and additional energy consumption. Although various advanced solar evaporators have been developed, their practical applications are still restricted by the unsustainable materials and the difficulty of precise customization for structure to escort high solar-thermal efficiency. To address these issues, we employed two kinds of naturally occurring molecules, tannic acid and iron (III), to construct a low-cost, highly efficient and durable interfacial solar evaporator by three-dimensional (3D) printing. Based on a rational structural design, a robust and 3D-printed evaporator with conical array surface structure was developed, which could promote the light harvesting capacity significantly via the multiple reflections and anti-reflection effects on the surface. By optimizing the height of the conical arrays, the 3D-printed evaporator with tall-cone structure could achieve a high evaporation rate of 1.96 kg m^-2 h^-1 under one sun illumination, with a photothermal conversion efficiency of 94.4%. Moreover, this evaporator was also proved to possess excellent desalination performance, recycle stability, anti-salt property, underwater oil resistance, as well as adsorption capacity of organic dye contaminants for multipurpose water purification applications. It was believed that this study could provide a new strategy to fabricate low-cost, structural regulated solar evaporators for alleviating the dilemma of global water scarcity using abundant naturally occurring building blocks.

Plasma Meets MOFs: Synthesis, Modifications, and Functionalities

As a porous and network materials consisting of metals and organic ligands, metal-organic frameworks (MOFs) have become one of excellent crystalline porous materials and play an important role in the era about materials science. Plasma, as a useful tool for stimulating efficient reactions under many conditions, and the plasma-assisted technology gets more attractions and endows MOFs more properties. Based on its feature, the research about the modifications and functionalities of MOFs have been developing a certain extent. This review contains a description of the methods for plasma-assisted modification and synthesis of MOFs, with specifically focusing on the plasma-assisted potential for modifications and functionalities of MOFs. The different applications of plasma-assisted MOFs were also presented.

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.

Conjugated photothermal materials and structure design for solar steam generation

With the development of solar steam generation (SSG) for clean water production, conjugated photothermal materials (PTMs) have attracted significant interest because of their advantages over metallic and inorganic PTMs in terms of high light absorption, designable molecular structures, flexible morphology, and solution processability. We review here the recent progress in solar steam generation devices based on conjugated organic materials. Conjugated organic materials are processed into fibers, membranes, and porous structures. Therefore, nanostructure design based on the concept of nanoarchitectonics is crucial to achieve high SSG efficiency. We discuss the considerations for designing SSG absorbers and describe commonly used conjugated organic materials and structural designs.

Size Regulation of Polydopamine Nanoparticles by Boronic Acid and Lewis Base

Size regulation of polydopamine nanoparticles (PDA NPs) is vital to melanin-inspired materials. The general strategy usually focuses on tuning of the reaction parameters which could affect the dopamine (DA) monomer polymerization process, such as pH, temperature, monomer concentration, etc. The reaction between boronic acids and catechols to form boronic esters has been widely applied in many fields, but little attention has been paid in the size regulation of PDA NPs. Here, it is speculated that the fine size regulation of PDA NPs can be directly achieved by using boronic acids and Lewis base molecules. It is found that these issues could indeed significantly affect the stability of the boronic esters formed by boronic acids and DA, which may further inhibit the monomer polymerization kinetics and tune the particle size of the resulting PDA NPs. It is also found that the several intrinsic properties of PDA NPs such as the free radical scavenging ability, UV spectral absorption, photothermal behavior, and structural color all change with the particle size. It is believed that this work can provide new opportunities for fabricating melanin-inspired PDA NPs with well controlled size and properties.

Maple Leaf Inspired Conductive Fiber with Hierarchical Wrinkles for Highly Stretchable and Integratable Electronics

Stretchable and durable conductors are significant to the development of wearable devices, robots, human-machine interfaces, and other artificial intelligence products. However, the desirable strain-insensitive conductivity and low hysteresis are restricted by the failure of stretchable structures and mismatch of mechanical properties (rigid conductive layer and elastic core substrate) under large deformation. Here, based on the principles of fractal geometry, a stretchable conductive fiber with hierarchical wrinkles inspired by the unique shape of the maple leaf was fabricated by combining surface modification, interfacial polymerization, and improved prestrain finishing methods to break through this dilemma. The shape and size of wrinkles predicted by buckling analysis via the finite element method fit well with that of actual wrinkles (30-80 μm of macro wrinkles and 4-6 μm of micro wrinkles) on the fabricated fiber. Such hierarchically wrinkled conductive fiber (HWCF) exhibited not only excellent strain-insensitive conductivity denoted by the relative resistance change ΔR/R₀ = 0.66 with R₀ the original resistance and ΔR the change of resistance after the concrete strain reaching up to 600%, but also low hysteresis (0.04) calculated by the difference in area between stretching and releasing curve of the ΔR/R₀ strain under 300% strain and long-term durability (>1000 stretching-releasing cycles). Furthermore, the elastic conductive fiber with such a bionic structure design can be applied as highly stretchable electrical circuits for illumination and monitors for the human motion under large strains through tiny and rapid resistance changes as well. Such a smart biomimetic material holds great prospects in the field of stretchable electronics.

Fabrication of Textile Waste Fibers Aerogels with Excellent Oil/Organic Solvent Adsorption and Thermal Properties

In recent years, the treatment of textile waste has attracted more and more attention around the world. The reuse of textile waste can contribute to the reduction of carbon emissions and the sustainable development of the economy. Herein, we proposed a facile and cost-effective approach to fabricating aerogel by using textile waste fibers as the matrix and polyvinyl alcohol (PVA) and glutaraldehyde (GA) as crosslinking agents. After being modified with methyltrimethoxysilane (MTMS) via chemical vapor deposition, both the interior and exterior of the textile waste aerogels exhibit a hydrophobic property with a water contact angle of up to 136.9° ± 2.3°. A comprehensive investigation of the structure, thermal properties, mechanical properties and oil absorption capacity of this aerogel shows its potential for building insulation and oil spill cleanup. The textile waste fibers aerogels have low density and high porosity, good thermal stability and outstanding heat insulation properties (K_avg. = 0.049–0.061 W/m·K). With a maximum oil absorption value of 26.9 ± 0.6 g/g and rapid and effective oil/water mixture separation, the aerogel exhibits competitive commercial application value.

Robust and multifunctional natural polyphenolic composites for water remediation

The scarcity of clean water has become a global environmental problem which constrains the development of public health, economy, and sustainability. In recent years, natural polyphenols have drawn increasing interests as promising platforms towards diverse water remediation composites and devices, owing to their abundant and renewable resource in nature, highly active surface chemistry, and multifunctionality. This review aims to summarize the most recent advances and highlights of natural polyphenol-based composite materials (e.g., nanofibers, membranes, particles, and hydrogels) for water remediation, by focusing on their structural and functional features, as well as their diversified applications including membrane filtration, solar distillation, adsorption, advanced oxidation processes, and disinfection. Finally, the future challenges in this field are also prospected. It is anticipated that this review will provide new opportunities towards the future development of natural polyphenols and other kinds of naturally occurring molecules in water purification applications.

Fe3O4/Diatomite-Decorated Cotton Evaporator for Continuous Solar Steam Generation and Water Treatment

Improving the evaporation rate of solar steam generation (SSG) has always been a research hotspot to solve the shortage of water resources. Using cotton, Fe₃O₄, polyvinyl alcohol (PVA) and diatomite (DM) as raw materials, DM/PVA/Fe₃O₄@cotton composites with both firmness and hydrophilicity were prepared. Fe₃O₄ has a wide range of light absorption characteristics and good photothermal conversion performance, and is an ideal photothermal conversion material. PVA enhances the adhesion between Fe₃O₄, cotton and DM and enhances the hardness of the sample and the internal porous structure. The existence of DM greatly improves the hydrophilicity of the sample, ensuring that the water in the lower layer can be continuously transported to the surface of the sample, and DM makes the surface of the sample rough, which reduces the reflection of sunlight and improves the efficiency of light heat conversion. Under one-sun irradiation, the temperature of the sample surface increases by 52.6 °C, the evaporation rate can reach 1.32 kg m^-2 h^-1 and the evaporation efficiency is 82.9%. Using this sample as the photothermal conversion layer of the SSG device, the removal rate of salt ions in seawater is more than 98% and the removal rate of heavy metal ions in sewage is close to 100%. This work provides a new idea and design method for SSG in the field of seawater desalination and sewage treatment.

Reviewing wood-based solar-driven interfacial evaporators for desalination

Solar‒driven interfacial water evaporation is a convenient and efficient strategy for harvesting solar energy and desalinating seawater. However, the design and fabrication of solar evaporators still challenge reliable evaporation and practical applications. Wood-based solar-driven interfacial water evaporation emerge as a promising and environmentally friendly approach for water desalinating as it provides renewable and porous structures. In recent years, surface modifications and innovative structural designs to prepare high performance wood-based evaporators is widely explored. In this review, we firstly describe the superiority of wood for the fabrication of wood-based solar evaporators, including the pore structure, chemical structure and thermal insulation. Secondly, we summarize the recent developments in wood-based evaporators from surface carbonization, decoration with photothermal materials, bulk modification and structural design, and discuss from the aspects of water transportation capacity, thermal conductivity and photothermal efficiency. Finally, based on these previous results and analysis, we highlight the remaining challenges and potential future directions, including the selection of high-efficient photothermal materials, heat and mass transfer mechanism in wood-based evaporators including large-scale production at a low cost.

Modification of Thin Film Composite Membrane by Chitosan-Silver Particles to Improve Desalination and Anti-Biofouling Performance

Reverse osmosis (RO) desalination is a technology that is commonly used to mitigate water scarcity problems; one of its disadvantages is the bio-fouling of the membranes used, which reduces its performance. In order to minimize this problem, this study prepared modified thin film composite (TFC) membranes by the incorporation of chitosan-silver particles (CS-Ag) of different molecular weights, and evaluated them in terms of their anti-biofouling and desalination performances. The CS-Ag were obtained using ionotropic gelation, and were characterized by Fourier transform infrared spectroscopy (FTIR), high-resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA) and dynamic light scattering (DLS). The modified membranes were synthetized by the incorporation of the CS-Ag using the interfacial polymerization method. The membranes (MCS-Ag) were characterized by Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and contact angle. Bactericidal tests by total cell count were performed using Bacillus halotolerans MCC1, and anti-adhesion properties were confirmed through biofilm cake layer thickness and total organic carbon (%). The desalination performance was defined by permeate flux, hydraulic resistance, salt rejection and salt permeance by using 2000 and 5000 mg L^-1 of NaCl. The MCS-Ag-L presented superior permeate flux and salt rejection (63.3% and 1% higher, respectively), as well as higher bactericidal properties (76% less in total cell count) and anti-adhesion capacity (biofilm thickness layer 60% and total organic carbon 75% less, compared with the unmodified membrane). The highest hydraulic resistance value was for MCS-Ag-M. In conclusion, the molecular weight of CS-Ag significantly influences the desalination and the antimicrobial performances of the membranes; as the molecular weight decreases, the membranes' performances increase. This study shows a possible alternative for increasing membrane useful life in the desalination process.

Facile Electrodeposition of NiCo2O4 Nanosheets on Porous Carbonized Wood for Wood-Derived Asymmetric Supercapacitors

Multichannel-porous carbon derived from wood can serve as a conductive substrate for fast charge transfer and ion diffusion, supporting the high-theory capacitance of pseudocapacitive materials. Herein, NiCo₂O₄ nanosheets, which are hierarchically porous, anchored on the surface of carbonized wood via electrodeposition for free-binder high-performance supercapacitor electrode materials, were proposed. Benefiting from the effectively alleviated NiCo₂O₄ nanosheets accumulation and sufficient active surface area for redox reaction, a N-doped wood-derived porous carbon-NiCo₂O₄ nanosheet hybrid material (NCNS–NCW) electrode exhibited a specific electric capacity of 1730 F g⁻¹ at 1 A g⁻¹ in 1 mol L⁻¹ KOH and splendid electrochemical firmness with 80% capacitance retention after cycles. Furthermore, an all-wood-based asymmetric supercapacitor based on NCNS–NCW//NCW was assembled and a high energy density of 56.1 Wh kg⁻¹ at a watt density of 349 W kg⁻¹ was achieved. Due to the great electrochemical performance of NCNS–NCW, we expect it to be used as an electrode material with great promise for energy storage equipment.

Boosting Low-Temperature Resistance of Energy Storage Devices by Photothermal Conversion Effects

While flexible supercapacitors with high capacitance and energy density is highly desired for outdoor wearable electronics, their application under low-temperature environments, like other energy storage devices, remains an urgent challenge. Solar thermal energy converts solar light into heat and has been extensively applied for solar desalination and power generation. In the present work, to address the failure problem of energy storage devices in a cold environment, solar thermal energy was used to improve flexible supercapacitor performance at low temperature. As a proof of concept presented here, a typical all-solid-state supercapacitor composed of activated carbon electrodes and gel polymer electrolyte was coated by a carbonized melamine sponge. Due to the ability of photothermal conversion of carbonized melamine sponge, the capacitance of the supercapacitor was greatly enhanced, which could be further improved by adding surface plasmonic nanomaterials, for example, Ag nanowires. Compared with the device without photothermal conversion layers, the specific capacitance increased 3.48 times at -20 °C and retained 87% capacitance at room temperature and the specific capacitance increased 6.69 times at -50 °C and retained 73% capacitance at room temperature. The present work may provide new insights on the application of solar energy and the design of energy storage devices with excellent low-temperature resistance.

Multiscale Mechanical Performance of Wood: From Nano- to Macro-Scale across Structure Hierarchy and Size Effects

This review describes methods and results of studying the mechanical properties of wood at all scales: from nano- to macro-scale. The connection between the mechanical properties of material and its structure at all these levels is explored. It is shown that the existing size effects in the mechanical properties of wood, in a range of the characteristic sizes of the structure of about six orders of magnitude, correspond to the empirical Hall-Petch relation. This “law” was revealed more than 60 years ago in metals and alloys and later in other materials. The nature, as well as the particular type of the size dependences in different classes of materials can vary, but the general trend, “the smaller the stronger”, remains true both for wood and for other cellulose-containing materials. The possible mechanisms of the size effects in wood are being discussed. The correlations between the mechanical and thermophysical properties of wood are described. Several examples are used to demonstrate the possibility to forecast the macromechanical properties of wood by means of contactless thermographic express methods based on measuring temperature diffusivity. The research technique for dendrochronological and dendroclimatological studies by means of the analysis of microhardness and Young’s modulus radial dependences in annual growth rings is described.

Hierarchically Designed Three-Dimensional Composite Structure on a Cellulose-Based Solar Steam Generator

The emerging water purification technology represented by solar water evaporation has developed rapidly in recent years and is widely used in seawater desalination. However, the high reflectivity of sunlight and low efficiency of photothermal conversion greatly hinder its application prospects. In this paper, the hierarchical structure of the film was designed and optimized by the addition of carbon materials in the process of bacterial cellulose culture. A cellulose-based composite film material with a microporous structure was obtained, which can improve the photothermal evaporation rate and photothermal conversion efficiency from the structural principle to improve the stability of floating on the water. Bacterial cellulose (BC) as a three-dimensional carrier was combined with one-dimensional and two-dimensional (1D/2D) compounds of carbon nanotubes (CNT) and reduced graphene oxide (RGO) to form composite films for solar evaporation. By the addition of CNT-RGO (21.8 wt %), the composite showed prominent photothermal evaporation rate and photothermal conversion efficiency properties. Through in situ culture of BC, not only a tight structure can be obtained but also the surface of BC contains a large number of hydroxyl groups, which have many active sites to load photothermal materials. BC nanofibers, CNT, and RGO cooperate to form a porous network structure, which provides continuous double channels for the rapid transmission of water molecules and light paths, so as to form an excellent photothermal layer. The photothermal conversion efficiency is 90.2%, and the photothermal evaporation rate is 1.85 kg m^-2 h^-1 to achieve efficient solar interface evaporation. This is a high level of photothermal properties in a cellulose-based solar steam generator. The superior photothermal performance of this hybrid film possesses scalability and desalination ability.

Thermally Conductive and Superhydrophobic Polyurethane Sponge for Solar-Assisted Separation of High-Viscosity Crude Oil from Water

The rapid and effective separation of high-viscosity heavy crude oil from seawater is a worldwide challenge. Herein, an ultralow density, photothermal, superhydrophobic, and thermally conductive polyurethane/polyaniline/hexagonal boron nitride@Fe₃O₄/polyacrylic-oleic acid resin sponge (PU/PANI/h-BN@Fe₃O₄/AR) was fabricated with a water contact angle (WCA) of 158°, thermal conductivity of 0.76 W m^-1 K^-1, density of 0.038 g cm^-3, limited oxygen index (LOI) of 28.82%, and porosity of 97.97% and used for solar-assisted separation of high-viscosity crude oil from water. Photothermal components were composed of PANI and Fe₃O₄, while h-BN particles were used as thermally conductive and flame retardant fillers. Therefore, the illuminated sunlight irradiation on the modified sponge was converted to heat due to the activity of photothermal components. The produced heat was rapidly transferred to the environment due to the presence of h-BN for increasing the temperature of the high-viscosity crude oil and reducing oil viscosity that helped to promote its fluidity and effective absorption. The crude oil absorption capacity of this sponge increased from 4 to 57 g g^-1 under irradiation of a sunlight simulator (power: 1 sun: 1 kW m^-2) for 17 min due to oil viscosity reduction from 2.46 × 10⁴ to below 100 mPa s followed by an increase in the surface temperature from 26 to 89 °C. Also, the oil absorption capacity was evaluated in a static state (172 g g^-1 for chloroform), under different external magnetic fields (140.7 g g^-1 for gasoline), and in a continuous state, which was 65,100 times of its own weight in the gasoline filtration process. The PU/PANI/h-BN@Fe₃O₄/AR sponge exhibited excellent stability against 20 times of reusing, mechanical compression, abrasion, immersing in various pH solutions, seawater, and high temperature. In all, the results confirmed that the prepared sponge is an excellent absorbent for organic solvents and highly viscous crude oil in the absence and presence of sunlight irradiation.

The emerging development of solar evaporators in materials and structures

To tackle the increasingly severe freshwater resource scarcity problem, desalination using solar evaporators is potentially an effective approach. This article reviews the research progress of solar evaporators in recent years, including materials, structures, and performance evaluations. In terms of material research, this article introduces the mechanism of photothermal conversion of metallic, semiconductor, polymeric, and carbon-based materials and their applications in the research of solar evaporators. The structure design of solar evaporators that can improve the photothermal conversion efficiency and water transport efficiency are summarized in detail. Regarding the evaluation of the evaporator performance, common evaluation methods for steam efficiency and environmental benefits of solar evaporators were introduced. Finally, this article analyzes the current problems of evaporators and proposes a prospect for the development of new types of high-efficiency evaporators.

Metal-free functionalized carbonized cotton for efficient solar steam generation and wastewater treatment

Water desalination via solar steam generation is one of the most important technologies to address the increasingly pressing global water scarcity. Materials for solar photothermal energy conversion are highly sought after for their cost savings, environmental friendliness and broad utility in many applications including domestic water heating and solar-driven desalination. Herein, we report the successful development of metal-free, low weight and cost effective functionalized carbonized cotton (CC) fibers for efficient solar water desalination and wastewater treatment. The CC fibers with nearly full solar spectrum absorption, efficient photo-thermal conversion and low-cost could provide excellent alternatives to the high-cost plasmonic-based materials for solar water desalination. We also report on a novel and simple device to mitigate the issues associated with conductive heat loss by utilizing the economically viable carbonized cotton materials as an irradiation surface placed on a low-density polyethylene foam that floats on the surface of seawater. The CC solar steam generation device exhibits average water evaporation rates of 0.9, 6.4 and 10.9 kg m^-2 h^-1 with impressive solar-to-vapor efficiencies of 59.2, 88.7 and 94.9% under 1, 5 and 8 sun illumination, respectively. Moreover, the device displays excellent durability showing stable evaporation rates over 10 steam generation cycles under 5 sun of solar intensity. Furthermore, the applicability of the CC device for the removal of organic dyes from contaminated water through solar steam generation is also demonstrated. The low-cost, simple design, high solar thermal evaporation efficiency, excellent stability and long-term durability make this CC device a perfect candidate for applications in seawater desalination and wastewater treatment by solar steam generation.

Polydopamine-Bi2WO6-Decorated Gauzes as Dual-Functional Membranes for Solar Steam Generation and Photocatalytic Degradation Applications

The dual-functional Bi2WO6/polydopamine (PDA)-modified gauze membrane has been developed for applications in photocatalytic degradation and solar steam generation. Two types of membrane were prepared by changing the growth sequence of Bi2WO6 nanomaterials and PDA on gauze substrates. The spatial distribution of Bi2WO6 and polydopamine has a great influence on light absorption, photocatalytic degradation, and solar steam generation performances. Bi2WO6 photocatalysts can absorb short-wavelength light for the photocatalytic decoloration of organic dyes. The photothermal polydopamine can convert light into heat for water evaporation. Besides, the gauze substrate provides water transport channels to facilitate water evaporation. The morphology, surface chemistry, and optical properties of Bi2WO6-PDA modified gauzes were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and diffuse reflectance spectra. The photothermal properties, wetting properties, and solar steam generation rates of the composite films were also studied. Degradation of 96% of indigo carmine was achieved after being irradiated for 120 min in the presence of G/PDA/BWNP. The water evaporation rates of the G/BWP/PDA sample under the irradiation of an Xe lamp (light intensity = 1000 W/m2) reached 1.94 kg·m-2·h-1.

Enhanced Photothermal Performance by Carbon Dot-Chelated Polydopamine Nanoparticles

Polydopamine (PDA) has been widely used in biomedical applications including imaging contrast agents, antioxidants, UV protection, and photothermal therapy due to its biocompatibility, metal-ion chelation, free-radical scavenging, and wideband absorption, but its low photothermal efficiency still needs to be improved. In this study, we chelated near-infrared (NIR) sensitive carbon quantum dots on the surface of polydopamine (PDA-PEI@N,S-CQDs) to increase its near-infrared absorption. Surprisingly, although only 4% (w/w) of carbon quantum dots was conjugated on the PDA surface, it still increased the photothermal efficiency by 30%. Moreover, PDA-PEI@N,S-CQDs could also be used as the drug carrier for loading 60% (w/w) of the DOX and achieved stimuli-responsive drug release under lysosomal pH (pH 5.0) and 808 nm laser illumination. For in vitro therapeutic experiment, PDA-PEI@N,S-CQDs showed the remarkable therapeutic performance under 808 nm laser irradiation for killing 90% of cancer cells compared with 50% by pure PDA nanoparticles, and the efficacy was even higher after loading DOX owing to the synergistic effect by photothermal therapy and chemotherapy. This intelligent and effective therapeutic nanosystem based on PDA-PEI@N,S-CQDs showed enhanced photothermal behavior after chelating carbon dots and promoted the future development of a nanoplatform for stimuli-responsive photothermal/chemo therapy.

Hydrogen-Bonding-Aided Fabrication of Wood Derived Cellulose Scaffold/Aramid Nanofiber into High-Performance Bulk Material

Preparing a lightweight yet high-strength bio-based structural material with sustainability and recyclability is highly desirable in advanced applications for architecture, new energy vehicles and spacecraft. In this study, we combined cellulose scaffold and aramid nanofiber (ANF) into a high-performance bulk material. Densification of cellulose microfibers containing ANF and hydrogen bonding between cellulose microfibers and ANF played a crucial role in enhanced physical and mechanical properties of the hybrid material. The prepared material showed excellent tensile strength (341.7 MPa vs. 57.0 MPa for natural wood), toughness (4.4 MJ/m³ vs. 0.4 MJ/m³ for natural wood) and Young’s modulus (24.7 GPa vs. 7.2 GPa for natural wood). Furthermore, due to low density, this material exhibited a superior specific strength of 285 MPa·cm³·g⁻¹, which is remarkably higher than some traditional building materials, such as concrete, alloys. In addition, the cellulose scaffold was infiltrated with ANFs, which also improved the thermal stability of the hybrid material. The facile and top-down process is effective and scalable, and also allows one to fully utilize cellulose scaffolds to fabricate all kinds of advanced bio-based materials.