Sustainable Functional Materials Research Articles

Nature-Inspired Helicoidal Nanocellulose-Based Multi-Compartment Assemblies with Tunable Chiroptical Properties.

Cellulose-based nanocomposites are highly appealing for the development of next-generation sustainable functional materials. Although many advances have been made in this direction, the true potential of fibrillar nanocomposites has yet to be realized because available fabrication approaches are inadequate for achieving precise structural control at the sub-micrometer scale. Here a spray-assisted alignment methodology of cellulose nanofibrils is combined with the layer-by-layer assembly into an additive manufacturing process in which the alignment direction of each cellulose layer is rationally selected to achieve thin films with a helicoidal arrangement of the nanofibrils. The helicoidal structure of the films is verified by measuring the circular dichroism (CD) of the samples. The sign and position of the structural CD peak show that the handedness and the pitch of the chiral structures can be easily tuned by deliberately selecting simple parameters, such as the number of consecutive cellulose layers sprayed in the same direction, and the angle of rotation between successive stacks of layers. To the authors' knowledge, this approach is unique as it offers the possibility to prepare complex nanocomposite architectures with various nanoscale-controlled sub-structures from different anisometric objects, which is enabling novel designs of composite films with damage-resistant and/or optical filtering functionalities.

A bionic strong nanostructured soy protein-based adhesive enabled antistatic and self-extinguishing wood-based composites

Wood composites represent one kind of sustainable functional materials for interior decoration and packaging, but their tendency to generate static electricity poses discomfort and potential fire hazards. To address this huge challenge, we herein report a strong, conductive, nanostructured formaldehyde-free soy protein-based adhesive by mixing nanocellulose and tannic acid functionalized MXene, and soy protein, which is then used to create antistatic and fire-extinguishing wood composites. The resulted soy protein-based adhesive exhibited an exceptional bonding capability due to its bionic organic-inorganic hybridized crosslinking structure. With this soy protein-based adhesive, as-prepared wood composites achieved a static flexural strength of 14.08 MPa, meeting the demanding interior use requirement. Because of the presence of both MXene and quaternary ammonium salt in the adhesive, the resultant wood composite shows an electrical resistance of 3.123 × 109 Ω·cm, satisfying the antistatic requirements for wood-based composites, and a desired self-extinguishing ability. This work offers a promising strategy to create strong nanostructured bio-adhesive, which can be used for producing multifunctional wood composites as decoration and packaging materials.

Facile preparation of environmental benign LED white light active humic acid nanolayer coated titanium dioxide photocatalyst for bisphenol A degradation

Natural organic matter is a mixture of microbial decomposition products widely found in surface and groundwater. These organic materials have great potential as carbon-based precursors for chemical synthesis. This work demonstrated the development of a green photocatalyst via a facile adsorption process that combined colloidal titanium dioxide (TiO2) with humic acid. The resulting photocatalyst was visible light active and able to completely degrade 5 mg/L of BPA within 6 h under the irradiation of energy-efficient LED white light. The first-order kinetic rate constant of the reaction was determined to be 1.7 × 10−2 min−1. The enhanced photocatalytic activity was attributed to the decreased band gap energy and effective charge separation that limits the photogenerated electron-hole recombination. The outcome of this research opened an opportunity for the development of sustainable functional materials using natural organic matter.

Injectable, thermo-sensitive and self-adhesive supramolecular hydrogels built from binary herbal small molecules towards reusable antibacterial coatings.

Herbal hydrogels as a new class of sustainable functional materials have attracted extensive attention. However, the development of herbal hydrogels is significantly hindered due to their poor hydrogel performances and the lack of universal preparation methods. In this study, four herbal hydrogels composed of phytochemical polyphenols and stevioside compounds are prepared through a facile heating-cooling process, where multiple hydrogen bonding interactions between two monomers provide the main driving force for gelation. These herbal hydrogels exhibit thermo-sensitivity and good reversibility (25-90 °C), robust adhesion behaviours on hydrophilic and hydrophobic surfaces (maximum adhesion strength of 591.7 kPa), and outstanding antibacterial properties (100% bacteriostatic ratio). Profiting from these intriguing characteristics, they are demonstrated to show great potential as natural antibacterial coatings by depositing thin hydrogel layers onto diverse substrates. More importantly, the hydrogel coatings could be easily recycled by thermal regelation and reused at least 5 times. This work proposes a simple and universal strategy for preparing functional hydrogels based on binary herbal small molecules, which also sheds light on the development of reusable hydrogel coatings.

Elucidating the Bulk Morphology of Cellulose‐Based Conducting Aerogels with X‐Ray Microtomography

AbstractConducting cellulose composites are promising sustainable functional materials that have found application in energy devices, sensing and water purification. Herein, conducting aerogels are fabricated based on nanofibrillated cellulose and poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate, using the ice templating technique, and their bulk morphology is characterized with X‐ray microtomography. The freezing method (−20 °C in a freezer vs liquid nitrogen) does not impact the mean porosity of the aerogels but the liquid‐N2 aerogels have smaller pores. The integration of carbon fibers as addressing electrodes prior to freezing results in increased mean porosity and pore size in the liquid‐N2 aerogels signifying that the carbon fibers alter the morphology of the aerogels when the freezing is fast. Spatially resolved porosity and pore size distributions also reveal that the liquid‐N2 aerogels are more inhomogeneous. Independent of the freezing method, the aerogels have similar electrochemical properties. For aerogels without carbon fibers, freezer‐aerogels have higher compression modulus and are less stable under cycling compression fatigue test. This can be explained by higher porosity with larger pores in the center of liquid‐N2 aerogels and thinner pore walls. This work demonstrates that micro‐CT is a powerful tool for characterizing the morphology of aerogels in a non‐destructive and spatially resolved manner.

Advanced and sustainable functional materials for potassium-ion batteries

Rechargeable potassium-ion batteries (PIBs) have gained attention as sustainable, environmentally friendly, and cost-effective large-scale stationary energy storage technology. However, although this technology was assumed to perform in a manner similar to that of its monovalent counterparts, huge anode volume expansion and sluggish kinetics are posing challenges in up-scaling it. Apart from the efforts to develop and optimise electrode materials, recent research endeavours have also focussed on the essential role of sustainability. These attempts have often relied on bio-derived and bio-inspired materials to mimic the effectiveness of nature. Furthermore, the use of materials with self-healing properties can alleviate electrode degradation after cycling and augment its electrochemical performance. This review summarises the development of smart materials with self-healing properties that aid in overcoming the present issues of PIBs and highlights the relevance of the interphases. In addition, state-of-the-art design strategies for bio-derived and bio-inspired materials are presented and discussed. The incorporation of recycled and sustainable materials into the manufacturing of PIBs is expected to contribute towards the ultimate goal of achieving truly circular economy ecosystems. Finally, perspectives for further advancements are provided to kindle new ideas and open questions regarding the use of new-generation materials in the development of PIBs.

Upcycling Wool Waste into Keratin Gel-Based Nanofibers Using Deep Eutectic Solvents.

Millions of tons of wool waste are produced yearly by textile industries, which may become a serious environmental hazard in the near future. Given this concern, it is crucial to explore strategies to reduce the amount of wool waste generated worldwide and adopt more sustainable practices for dissolving and regenerating wool keratin (WK) from textile waste. Most traditional methods involve the use of expensive, toxic, harmful, and poorly biodegradable compounds. To overcome these limitations and facilitate the reuse of wool waste through a cascade valorization strategy, researchers have started testing the use of deep eutectic solvents (DES) as a more sustainable and eco-friendly alternative for WK dissolution and regeneration. In this study, the potential of two different DES mixtures, Choline chloride (ChCl): Urea and L-Cysteine (L-Cys): Lactic acid (LA), was explored for dissolving wool waste. Subsequently, the gels obtained based on DES-WK were blended with polyvinyl alcohol (PVA) in different ratios to produce nanofibers using the electrospinning technique. The PVA/L-Cys: LA DES-WK proved to be the most effective DES mixture for fabricating WK gel-based nanofibers. Furthermore, their antioxidant and antimicrobial abilities were evaluated, thus confirming their bioactivity. The results obtained revealed that this approach to valorizing textile waste offers a unique avenue for the development of sustainable functional materials with potential applications in various biomedical and industrial fields.

Urushi as a Green Component for Thermally Curable Colloidal Lignin Particles and Hydrophobic Coatings.

Colloidal lignin nanoparticles are promising building blocks for sustainable functional materials. However, their instability in organic solvents and aqueous alkali limits their applicability. Current stabilization methods require nonrenewable and toxic reagents or tedious workup procedures. Here we show a method to prepare hybrid nanoparticles using only natural components. Urushi, a form of black oriental lacquer, and lignin are coaggregated to form hybrid particles, with Urushi acting as a sustainable component that stabilizes the particles via hydration barrier effect and thermally triggered internal cross-linking. The weight fractions of the two components can be adjusted to achieve the desired level of stabilization. Hybrid particles with Urushi content >25 wt % undergo interparticle cross-linking that produces multifunctional hydrophobic protective coatings that improve the water resistance of wood. This approach provides a sustainable and efficient method for stabilizing lignin nanoparticles and opens up neoteric possibilities for the development of lignin-based advanced functional materials.

High-Performance Sustainable Electrochromic Devices Based on Carrageenan Solid Polymer Electrolytes with Ionic Liquid.

The development of sustainable functional materials with strong potential to be applied in different areas has been growing and gaining increasing interest to address the environmental impact of current materials and technologies. In this scope, this work reports on sustainable functional materials with electrochromic properties, based on their increasing interest for a variety of applications, including sensing technologies. The materials have been developed based on a natural derived polymer, carrageenan, in which different amounts of the ionic liquid (IL) 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]) were blended. It is shown that the addition of different amounts of IL to the carrageenan matrix does not affect the properties of the samples in terms of morphology or physicochemical and thermal properties, the most significant difference being the increase of the ionic conductivity with increasing IL content, ranging from 2.3 × 10-11 S·cm-1 for pristine carrageenan to 4.6 × 10-4 S·cm-1 for the samples with 5 and 60 wt % IL content, respectively. A electrochromic device has been developed based on the different IL/carrageenan samples as electrolyte and poly(3,4-ethylenedioxythiophene) polystyrenesulfonate (PEDOT:PSS) as electrodes. Spectroelectrochemistry testing demonstrates functional devices at low voltages between 0.3 and -0.9 V. Among the different samples, the one with 15 wt % IL content presents the best conditions for application, presenting an oxidation time of 6 s, a reduction time of 8 s, and a charge density of 1150 and 1050 μC·cm-2 for oxidation and reduction, respectively. The same sample also presents excellent optical density as a function of load density, presenting an optical switch (Δ%Tx) of 99%. Thus, it is demonstrated that it is possible to develop high efficiency and sustainable electrochromic devices based on natural polymers and ionic liquids.

Biomolecular Fishing: Design, Green Synthesis, and Performance of l-Leucine-Molecularly Imprinted Polymers.

Biopurification is a challenging and growing market. Despite great efforts in the past years, current purification strategies still lack specificity, efficiency, and cost-effectiveness. The development of more sustainable functional materials and processes needs to address pressing environmental goals, efficiency, scale-up, and cost. Herein, l-leucine (LEU)-molecularly imprinted polymers (MIPs), LEU-MIPs, are presented as novel biomolecular fishing polymers for affinity sustainable biopurification. Rational design was performed using quantum mechanics calculations and molecular modeling for selecting the most appropriate monomers. LEU-MIPs were synthesized for the first time by two different green approaches, supercritical carbon dioxide (scCO2) technology and mechanochemistry. A significant imprinting factor of 12 and a binding capacity of 27 mg LEU/g polymer were obtained for the LEU-MIP synthesized in scCO2 using 2-vinylpyridine as a functional monomer, while the LEU-MIP using acrylamide as a functional monomer synthesized by mechanochemistry showed an imprinting factor of 1.4 and a binding capacity of 18 mg LEU/g polymer, both systems operating at a low binding concentration (0.5 mg LEU/mL) under physiological conditions. As expected, at a higher concentration (1.5 mg LEU/mL), the binding capacity was considerably increased. Both green technologies show high potential in obtaining ready-to-use, stable, and low-cost polymers with a molecular recognition ability for target biomolecules, being promising materials for biopurification processes.

Biomaterials and Their Potentialities as Additives in Bitumen Technology: A Review.

The carbon footprint reduction mandate and other eco-friendly policies currently in place are constantly driving the trend of the synthesis and application of sustainable functional materials. The bitumen industry is not an exception to this trend and, every day, new technologies that facilitate safer, cost effective and more sustainable industrial processes and road paving operations are being researched and brought to light. A lot of research is currently ongoing to improve bitumen's properties due to its use as a binder in road paving processes. Over the years, the most common method to improve bitumen's properties has been with the use of additives. The major drawback in the use of these additives is the fact that they are substances of strong chemical nature which are either too acidic, too basic or emit toxic fumes and volatile organic compounds into the environment. In the long run, these chemicals are also toxic to the road pavement personnel that carry out the day to day industrial and paving operations. This led researchers to the initiative of synthesizing and applying biomaterials to be used as additives for bitumen. In this light, several studies have investigated the use of substances such as bio-oils, natural waxes, gum, polysaccharides and natural rubber. This literature review is aimed at classifying the different bio-based materials used to improve bitumen's properties and to provide a deeper knowledge of the application of these biomaterials in bitumen technology. In general, we highlight how the research efforts elaborated herein could potentially foster safer, sustainable, eco-friendly approaches to improving bitumen's properties while also promoting a circular economy.

Tuning material properties via disorder: From crystalline alloy to metallic glass

Pathways to tune the electronic, chemical, mechanical, and optical properties of solids without modifying their composition represent a new paradigm in the design of functional and sustainable materials. The level of structural disorder - from perfectly crystalline to fully amorphous – for example, induces remarkable changes in material properties. Typically, disorder is introduced by altering the composition of a material, adding to the misconception that these two properties cannot be decoupled. Here, we demonstrate that striking differences in the optical, electronic, and corrosion properties of CuZr are achieved by deliberately and reproducibly engineering the level of structural disorder in pulsed laser deposited thin films of a constant composition. This approach allows tuning the structure of CuZr from polycrystalline to fully amorphous, switching the nature of charge transport from metallic to semiconductor-like, the optical properties in the visible regime from opaque to transparent, and the corrosion behavior in air from mixed oxidation to the formation of a protective Zr oxide overlayer. Our results highlight the tunability of structural disorder in alloys and its remarkable effect on material properties, providing the opportunity to design sustainable functional materials based on customizing properties beyond their composition.

Arylboronic acids catalyzed upgrade of glucosamines for deoxyfructosazine and insights on reaction mechanism

Chitin is the most abundant N-containing polysaccharide in nature and d-glucosamine is one of the most successful commercial monomer products in the current market. Here we reported an arylboronic acids catalyzed upgrade of glucosamines in aqueous solution for deoxyfructosazine which is an important high-value compound in pharmaceutical and food industries, as well as a promising bio-based platform molecule for speciality chemicals and sustainable functional materials. Such direct integration of deoxyfructosazine into development of renewable chemicals/functional materials might be a practical way for utilization of chitin as a renewable nitrogen source. A mechanism focusing on a catalytic cycle of arylboronic acid via a boron transfer was also proposed.

Advanced functional materials based on bamboo cellulose fibers with different crystal structures

Degradable and sustainable materials are needed to reduce pollution and energy consumption. Bamboo, an inexpensive and abundant resource, can be used to develop such materials. To this end, we demonstrate two types of bamboo-fiber-based functional materials. The first can be used as structural materials with outstanding anti-mildew properties (ultra-high tensile strength: 571 MPa; compressive strength: 191 MPa; surface hardness: 227 MPa) and is produced with long and aligned bamboo cellulose I fibers mixed with epoxy. The second is suitable for electrodes in wearable devices (areal capacitance: 2032 mF cm−2; linear capacitance: 670 F cm−1; energy density: 139.3 µWh cm−2; power density: 80.4 µW cm−2) and uses nickel-coated bamboo cellulose II fibers. The design strategies of bamboo-fiber-based functional materials demonstrated in this study provide new insights for novel degradable and sustainable functional materials.

Sustainable and Superhydrophobic Lignocellulose-Based Transparent Films with Efficient Light Management and Self-Cleaning.

Light-management (LM) films that can regulate transmitted light are significant to diverse fields, such as optoelectronics and energy-efficient buildings. However, for conventional LM films made from petroleum-based polymers, the nonbiodegradability and complicated fabrication process remain a challenge. Herein, we prepare sustainable lignocellulose-based films with excellent light-management capability by facile dissolution and regeneration of wood pulp and the corncob residue from xylitol production (CRXP). The obtained films exhibit high transparency (78%), high haze (61%), and especially remarkable UV-blocking performance (99.94% for UVB and 98.04% for UVA). They achieve consistent indoor light distribution and UV radiation shielding by light management for the application of smart buildings. Furthermore, by spray-coating with SiO2 nanoparticles to construct hierarchical networks, the films are endowed with a superhydrophobic surface with a self-cleaning function to mitigate dust accumulation. Our work provides novel insights into the conversion of lignocellulosic waste to desirable and sustainable functional materials.

Dedicate to commemorate of Prof. Lina Zhang

Dedicate to commemorate of Prof. Lina Zhang

Environment-friendly utilization of squid pen with water: Production of β-chitin nanofibers and peptides for lowering blood pressure

Chitin, an abundant biopolymer on Earth, represents a resource for sustainable functional materials. However, traditional β-chitin production methods involve alkaline treatment at approximately 90 °C for its separation from the protein, thus not suitable as a functional peptide, as it is mixed with an alkaline aqueous solution. This study examined the conversion of squid pen into solid β-chitin and water-soluble peptides using only water at temperatures of 150–250 °C for 30–120 min. Solid β-chitin was converted to its nanofiber form and the physicochemical properties of the β-chitin nanofibers were almost the same as those produced by the traditional method. Because this method uses only water, the protein in the squid pen may also be a functional peptide for lowering blood pressure, by inhibiting the Angiotensin-1 converting enzyme. High-temperature water treatment is a promising environment-friendly technique for complete utilization of squid pen components, including β-chitin and protein.

Lignosulfonate/diblock copolymer polyion complexes with aggregation-enhanced and pH-switchable fluorescence for information storage and encryption

Employing natural polymers as building blocks is favorable to construct sustainable functional materials and realize biomass utilization. Here we developed a series of supramolecular polyion complexes (PICs) composed of lignosulfonate and double-hydrophilic diblock copolymer poly(ethylene oxide-b-N, N-dimethylaminoethyl methacrylate) (PEO114-b-PDMAEMA24), which performed a blue emission with quenching-enhancing tendency and copolymer distribution inversion-involved assembling transformation at pH 5.6 and monotonic greenish-blue fluorescence promotion at pH 9.5 by increasing PEO114-b-PDMAEMA24 contents. Electrostatic interactions and multiple hydrogen bonds were revealed controlled the assembling behavior and affected the emission via altering the restriction of molecular motion, through-space conjunction, and non-luminous complexation. The multiple interacting sites and special topology of diblock copolymer contributed to the efficient fluorescence regulation. Information writing-erasing and encryption-decryption systems were established by utilizing emission intensity regulation and pH-responsive emission chromism. This work paved a new way to enhance lignin fluorescence and broadened potential applications of lignin composites in realms of sensing, imaging, monitoring, and anticounterfeiting.

Identification of a Grotthuss proton hopping mechanism at protonated polyhedral oligomeric silsesquioxane (POSS) – water interface

The attachment and dissociation of a proton from a water molecule and the proton transfers at solid–liquid interfaces play vital roles in numerous biological, chemical processes and for the development of sustainable functional materials for energy harvesting and conversion applications. Using first-principles computational methodologies, we investigated the protonated forms of polyhedral oligomeric silsesquioxane (POSS-H+) interacting with water clusters (Wn, where n = 1–6) as a model to quantify the proton conducting and localization ability at solid–liquid interfaces. Successive addition of explicit water molecules to POSS-H+ shows that the assistance of at least three water molecules is required to dissociate the proton from POSS with the formation of an Eigen cation (H9O4+), whereas the presence of a fourth water molecule highly favors the formation of a Zundel ion (H5O2+). Reaction pathway and energy barrier analysis reveal that the formation of the Eigen cation requires significantly higher energy than the Zundel features. This confirms that the Zundel ion is destabilized and promptly converts in to Eigen ion at this interface. Moreover, we identified a Grotthuss-type mechanism for the proton transfer through a water chain close to the interface, where symmetrical and unsymmetrical arrangements of water molecules around H+ of protonated POSS-H+ are involved in the conduction of proton through water wires where successive Eigen-to-Zundel and Zundel-to-Eigen transformations are observed in quick succession.

Smart recycling of PET to sorbents for insecticides through in situ MOF growth

The continually growing level of ecotoxicants generates a request for principal new strategies to safeguard the environment. In this contribution, we proposed a comprehensive approach to solving two emerging problems: recycling polyethylene terephthalate wastes (PET) and removing toxic insecticides from water. The developed technology consumed PET bottles as the source and support for the growth of UiO-66 frameworks and were further applied for the removal of imidacloprid from water. The prepared material was characterized by a range of microscopic and spectroscopic techniques confirming the high loading and homogenous distribution of UiO-66 across the PET support. The sorbent (PET@UiO-66) delivered considerable technical advantages beyond the convenient sorbents: sustainable and cheap preparation; high adsorption capacity and rate; stability and recyclability; 100 times enhanced permeability compared to UiO-66 powder; and applicability in fixed-bed columns. We believe that the proposed design and technological relevance will be a basis for the further developing of the smart utilization of wastes for sustainable functional materials.