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The use of functional biodegradable wastes to treat environmental problems would create minimal extra burden to our environment. In this paper, we propose a sustainable and practical strategy to turn spent coffee ground (SCG) into a multifunctional palladium-loaded catalyst for water treatment instead of going into landfill as solid waste. Bleached delignified coffee ground (D-SCG) has a porous structure and a good capability to reduce Pd (II) to Pd (0). A large amount of nanocellulose is formed on the surface of SCG after bleaching by H2O2, which anchors and disperses the palladium nanoparticles (Pd NPs). The D-SCG loaded with Pd NPs (Pd-D-SCG) is superhydrophilic, which facilitates water transport and thus promotes efficient removal of organic pollutants dissolved in water. Pd-D-SCG exhibits excellent room temperature catalytic activity for the removal of 4-nitrophenol (4-NP) and methylene blue (MB) in water and shows good chemical stability and recyclability in water, with no obvious decrease even after five repeated cycles.

Ionic skin with a high performance has been extensively explored due to its ability to convert external stimuli into obvious electrical signals for wearable electronics and intelligent detection. H...

Conductive elastomers (CEs) with strong mechanical properties have been fabricated and used in flexible electronics. However, the development of CEs with both super-high mechanical strength and extreme stretchability remains challenging. This paper reports on the development of a series of mechanically strong and tough CEs based on photopolymerizable deep eutectic solvents (PDESs) with dense hydrogen bonding interactions. One of these CEs exhibits the highest reported mechanical performance for elastomers, with tensile strength, strain at break and toughness up to 31.21 MPa, 3645% and 615 MJ m−3, respectively. Notably, this CE tolerates puncture and can lift a 10.5 kg weight (9500 times its own weight) without any failure. In addition, the series of CEs also shows excellent transparency (>94% in the visible range), favorable conductivity (0.007–0.04 S m−1), tunable stretchability (strain from 22% to 6164%) and good self-healing capability (electrical healing efficiency of 99% within 0.26 s). In view of the comprehensive properties of the CEs, we demonstrate the practical suitability of CEs by including them in a strain sensor to detect human motion. Based on their extremely facile preparation process and practical functionalities, we believe that CEs will not only contribute new methods for the development of mechanically strong conductors, but also open up novel avenues for flexible electronics.

Simultaneously achieving transparency, high mechanical strength and self-healing capability in conductive elastomers with simple and green features is a challenge. Here we develop a novel strategy for a tough yet self-healing supramolecular network by introducing Al(III)-carboxyl complexes into photo-polymerizable deep eutectic solvent (PDES). The resulting polymer simultaneously exhibits high transparency, ionic conductivity, and high stretchability. Notably, due to synergetic interactions of the H-bonds and coordination bonds in the polymer matrix, the supramolecular network shows a high stress at break while achieving good self-healing capability. In view of the outstandingly comprehensive properties, we continue to verify the practicability of our prepared materials as strain sensors to monitor external stimuli such as human motions. Our methodology is simple, green and time-saving, and the fundamental design concept derived from the multifunctional PDES will contribute to the development of tough, self-healing transparent materials and flexible electronics.

Ionic conductors are normally prepared from water-based materials in the solid form and feature a combination of intrinsic transparency and stretchability. The sensitivity toward humidity inevitably leads to dehydration or deliquescence issues, which will limit the long-term use of ionic conductors. Here, a novel ionic conductor based on natural bacterial cellulose (BC) and polymerizable deep eutectic solvents (PDESs) is developed for addressing the abovementioned drawbacks. The superstrong three-dimensional nanofiber network and strong interfacial interaction endow the BC-PDES ionic conductor with significantly enhanced mechanical properties (tensile strength of 8 × 105 Pa and compressive strength of 6.68 × 106 Pa). Furthermore, compared to deliquescent PDESs, BC-PDES composites showed obvious mechanical stability, which maintain good mechanical properties even when exposed to high humidity for 120 days. These materials were demonstrated to possess multiple sensitivity to external stimulus, such as strain, pressure, bend, and temperature. Thus, they can easily serve as supersensitive sensors to recognize physical activity of humans such as limb movements, throat vibrations, and handwriting. Moreover, the BC-PDES ionic conductors can be used in flexible, patterned electroluminescent devices. This work provides an efficient strategy for making cellulose-based sustainable and functional ionic conductors which have broad application in artificial flexible electronics and other products.

In this paper, nanochitin was used as an alternative natural nanomaterial to combine with cellulose fibers for fabricating high-strength paper. Two typical chitin nanowhiskers having contrasting sign of surface charge were compared to evaluate the enhancement performance on paper in details. The results show that nanochitin with positive charges on the surface has a significant effect on the strength properties of the prepared paper, especially on wet strength. When the dosage of chitin nanowhiskers was 2%, the wet strength index was increased to 2.48 N·m/g, which is important for paper-based analytical devices with the common use in liquid analysis. Typical colorimetric glucose assays were successfully performed, suggesting the improved analytical performance on these prepared paper.

It is a challenge to synthesize all-in-one molecular networks that are autonomously self-healable over a wide temperature range (from subzero to high), transparent, stretchable, and conductive. Her...

A new type of supramolecular elastomer, photopolymerized from two rationally designed polymerizable deep eutectic solvent (PDES) monomers, was reported. The resultant network was highly transparent, intrinsically conductive, stretchable, and self-healable. In particular, the healing process can even take place in various organic solvents, simultaneously with enhanced adaptability.

Three-dimensional covalent organic frameworks (3D COFs) have gained increasing attention for their attractive features. However, the development of 3D COFs is strongly restricted, mainly due to their synthetic difficulty and complicated structure determination. Post-synthetic modification, which can avoid these problems by incorporating functional moieties into a predetermined framework, provides an alternative way to construct 3D COFs with specific functions. Herein, we report the designed synthesis and characterization of a series of highly crystalline 3D COFs with different loadings of ethynyl groups. Notably, these alkyne-tagged 3D COFs provide a platform for targeted anchoring various specific groups onto the pore walls via click reactions. Moreover, the pore surface engineering can accordingly change their properties, for example, the obtained click products exhibited higher CO2 /N2 selectivity. We describe a simple but powerful strategy to build functional 3D COFs, which will certainly advance them for a ranging of interesting applications in the future.

Stretchable and antifreezing conductive hydrogels, especially prepared from natural polymers, are beneficial for important and rapidly growing stretchable electronic devices. Unfortunately, the pot...

Garnet electrolyte is a promising candidate for the development of all-solid-state Li-metal batteries, because of its safety and stability against Li metal. However, its practical application is limited by the difficulty in production of its high-density thin sheet. In this work, we have fabricated garnet thin sheet electrolytes (Li6.4La3Zr1.4Ta0.6O12, LLZTO) by tape-casting technique. By using Li2O as a liquid-phase sintering additive, a high relative density up to 99% was achieved. Electrochemical results show the LLZTO sheets have an ionic conductivity of 5.2 × 10−4 S cm−1 at 30 °C and good cycling stability against Li metal. Based on the sheets, all-solid-state Li/LLZTO/LiFePO4 batteries exhibit excellent reversible cycles at 60 °C and 0.1C with an initial discharge specific capacity of 125.8 mA h g−1 and a retention of 92.3% after 50 cycles. These results indicate that the tape-casting process demonstrated here provides an effective method of producing high-density garnet thin sheet electrolytes for high-performance all-solid-state Li-metal batteries.

Garnets are promising solid electrolytes for developing solid state Li batteries, owing to their features of relatively high conductivity and stability against lithium metal. However, they show shortcoming of Li penetration through garnets during Li plating and stripping, which limits their practice application. Herein, we present a strategy to solve such problem by coating SnO2 films on the surfaces of the Li6·4La3Zr1·4Ta0·6O12 pellets. Through conversion reaction of SnO2 with Li at 200 °C, the nanocomposite layers consisting of crosslinked LixSn and Li2O are formed between the Li and the Li6·4La3Zr1·4Ta0·6O12 electrolytes. This leads to transition from lithiophobicity to lithiophilicity, thus greatly reducing interfacial resistance from 1100 Ω cm2 to 25 Ω cm2. Furthermore, taking advantage of suppressing volume change of LixSn alloy which is about 260%, the intermediate layers maintain integrity under the current densities of 0.2 mA cm−2 for 650 h cycles. In addition, the critical current density of Li/SnO2-Li6.4La3Zr1·4Ta0·6O12-SnO2/Li can be as high as 1.15 mA cm−2. As a proof-of-concept, this effective interface modification based on conversion reaction method contributes to a useful way of solving the Li/garnet interface problem and promoting the solid state Li batteries development.

Recently, flutter-driven triboelectric nanogenerator (TENG) has shown huge potential in wind energy harvesting from ambient environments. However, almost all the reported devices are based on parallel structure which suffers from a critical problem of insufficient contact between triboelectric surfaces. In this work, we propose an angle-shaped TENG (AS-TENG) with the above issue resolved. The device is based on two Al layers stacked to form an angle shape and a FEP film positioned in between by sharing a common side. Thanks to this design, the FEP film can contact fully and intimately with the Al layers to facilitate the effect of contact electrification and electrostatic induction. Compared with the existing parallel-structured TENG, the AS-TENG shows an overwhelming output performance because of the enhanced contact area. Furthermore, the AS-TENG is introduced a wedge-shaped wind guide channel which can provide a driving force for the flutter and hence lower the start-up wind speed largely. To further enhance the electric output, the AS-TENGs can be facilely integrated into a 360° radial array, showing an enlarged windward area and a high level of integration. The AS-TENG array can be applied to harvest outdoor weak wind and act as a direct power source to charge a capacitor or drive electronic devices. This work provides a design strategy for natural weak wind scavenging which may push forward the practical applications of TENG for wind power.

An accurate quantification method with a wide linearity range is paramount for the development of low-cost, portable and point-of-care sensors. This work reports a new approach to analyze the colorimetric assays on paper-based sensors using the quantification from a light transmission method. Compared to the commonly-developed color intensity measurement on scanned digital images, a portable transmission densitometer is capable of directly quantifying the optical density of colorimetric results. The detection of heavy metals in an aqueous system, including Fe(ii), Cu(ii), and Ni(ii), was carried out to demonstrate the good performance and reliability of this method. Our measurements show that the linear quantification range spans from 0.5-500 mg L-1 for the assays of Cu(ii) and Fe(ii) and from 2-500 mg L-1 for Ni(ii) based on the reading of transmitted light through the assay spot. As a comparison, the linear range is restricted to 0.5-50 mg L-1 for the same assays when analysed by the common reflection method, suggesting a significant improvement in the accuracy and sensitivity of high analyte concentrations from the light transmission method. By expanding the linearity range, this method further streamlines the sampling procedure during analysis and will greatly advance the future development of paper-based analytical sensors.

The structure–property relationship investigation is of prime importance to development of porous MOFs exhibiting better performance. In this work, two regioisomeric diisophthalate ligands, with the only difference being the position of methyl and amino groups with respect to isophthalate moieties, were rationally designed and synthesized, and their corresponding dicopper paddlewheel-based MOFs were successfully fabricated under suitable solvothermal conditions. Single-crystal X-ray diffraction studies showed that they displayed the same network topology of ssa type, thus providing a platform to investigate the impact of the substituent's arrangement on gas adsorption properties. As revealed by gas adsorption studies, the pore textural properties and gas uptake capacities with respect to C2H2, CO2, and CH4 of ZJNU-11 are significantly higher than those of its isomer ZJNU-12 despite their same structures, indicating that the arrangement of functional groups makes a difference to the framework stabilities against desolvation and thus to the gas adsorption properties. In addition, ZJNU-11 is also capable of selectively adsorptive separation of C2H2 and CO2 from CH4, with high C2H2/CH4 (v/v, 1/1) and CO2/CH4 (v/v, 1/1) adsorption selectivities of 36.2 and 5.9 at 298 K and 1 atm. This work not only reported a porous MOF material for highly selective C2H2/CH4 and CO2/CH4 separations, but also demonstrated that the rational arrangement of substituent groups will be favorable to improve the MOF's stabilities and thus gas adsorption properties, which needs to be taken into account upon design and construction of porous MOFs.

The development of porous MOFs with novel structures and functional properties is a key research topic in the MOF chemistry and materials field. In this article, by employing a ligand conformation preorganization strategy, we designed a nonplanar methyl-substituted triisophthalate ligand, which was used to successfully construct a copper–hexacarboxylate framework with a novel topological structure. More importantly, the obtained MOF not only exhibits good hydrolytic stability but also shows utility as an adsorbent for efficient separation and purification of C2H2 and natural gas under ambient conditions. At ambient temperature and atmospheric pressure, the C2H2 and CO2 uptake capacities reach up to 149.1 and 83.1 cm3 (STP) g−1, while the IAST-predicted C2H2/CH4 (50/50, v/v), C2H2/CO2 (50/50, v/v), and CO2/CH4 (50/50, v/v) adsorption selectivities are as high as 22.2, 3.81, and 5.13.

Fiber and textile electronics provide a focus for a new generation of wearable electronics due to their unique lightness and flexibility. However, fabricating knittable fibers from conductive materials with high tensile and transparent properties remains a challenge, especially for applicability in harsh environments. Here, we report a simple photopolymerization approach for the rapid preparation of a new type of a transparent conductive polymer fiber, poly(polymerizable deep eutectic solvent (PDES)) fiber, which exhibits excellent stability at high/low temperature, in organic solvents, especially in dry environments, and overcomes the volatility and freezability of traditional gel materials. A poly(PDES) fiber possesses outstanding mechanical and sensing properties, including negligible hysteresis and creep, fast resilience after a long stretch (10 min), and signal stability during high-frequency cyclic stretching (1 Hz, 10 000 cycles). In addition, the poly(PDES) fibers are knitted into a plain-structured sensor on textile with breathability and high tolerance to damage, enabling stable and accurate monitoring of human stretching, bending, and rotation motions. Furthermore, its dry-cleaning resistance guarantees the feasibility of long-term monitoring, with the electrical signal remaining stable after five dry-cleaning cycles. These promising features of poly(PDES) fibers will promote potential applications in the fields of human movement monitoring, intelligent fibers, and soft robotics.

We report a rapid fabrication strategy of highly transparent piezoresistive balls with excellent pressure-sensitivity and toughness by photopolymerization of polymerizable deep eutectic solvents. By careful design and integration, a number of optoelectronic devices have been constructed with the piezoresistive balls as building blocks.

Recently, ambient energy harvesting has attracted a great deal of attention to develop clean and renewable energy technologies. In this work, a flexible photo-thermoelectric nanogenerator (PTENG) based on MoS2/PU photothermal film and Te/PEDOT thermoelectric layer has been demonstrated for harvesting environmental infrared (IR) light. The MoS2/PU photothermal film is carefully designed to exhibit excellent flexibility, transferability, and photothermal property. By integrating the photothermal layer with a Te/PEDOT thermoelectric device, the PTENG can produce electrical output without a spatial temperature gradient which is necessary for conventional thermoelectric device. Under IR light illumination, a high temperature difference can be generated across the device, and hence a potential difference established between two electrodes based on a coupling of photothermal effect and Seebeck effect. This type of PTENG exhibits numerous advantages, such as flexible, shape-adaptive, light-weight, and simple-fabrication, which may have a great potential of application in photo-thermoelectric energy harvesting for wearable electronics and implantable electronics.

Investigation of the impact of ligand-originated MOF (metal–organic framework) isomerism and ligand functionalization on gas adsorption is of vital importance because a study in this aspect provides valuable guidance for future fabrication of new MOFs exhibiting better performance. For the abovementioned purpose, two NbO-type ligand-originated MOF isomers based on methoxy-functionalized diisophthalate ligands were solvothermally constructed in this work. Their gas adsorption properties toward acetylene, carbon dioxide, and methane were systematically investigated, revealing their promising potential for the adsorptive separation of both acetylene/methane and carbon dioxide/methane gas mixtures, which are involved in the industrial processes of acetylene production and natural gas sweetening. In particular, compared to its isomer ZJNU-58, ZJNU-59 displays larger acetylene and carbon dioxide uptake capacities as well as higher acetylene/methane and carbon dioxide/methane adsorption selectivities despite its lower pore volume and surface area, demonstrating a very crucial role that the effect of pore size plays in acetylene and carbon dioxide adsorption. In addition, the impact of ligand modification with a methoxy group on gas adsorption was also evaluated. ZJNU-58 exhibits slightly lower acetylene and carbon dioxide uptake capacities but higher acetylene/methane and carbon dioxide/methane adsorption selectivities as compared to its parent compound NOTT-103. By contrast, enhanced adsorption selectivities and uptake capacities were observed for ZJNU-59 as compared to its parent compound ZJNU-73. The results demonstrated that the impact of ligand functionalization with a methoxy group on gas adsorption might vary from MOF to MOF, depending on the chosen parent compound. The results might shed some light on understanding the impact of both ligand-originated MOF isomerism and methoxy group functionalization on gas adsorption.

NbO-type MOFs constructed from dicopper paddlewheel secondary building units and diisophthalate ligands not only exhibit great promise for the separation of environment and energy-related gas pairs but also more importantly provide an excellent platform for the fundamental investigation of structure–property relationships. In this work, two NbO-type MOFs (ZJNU-91 and ZJNU-92) derived from linear and zigzag-shaped thieno[3,2-b]thiophene-functionalized diisophthalate ligands were solvothermally prepared and structurally characterized. Their gas adsorption properties with respect to C2H2, CO2, and CH4 were systematically investigated, revealing that they exhibit promising potential for selective adsorptive separation of C2H2–CH4 and CO2–CH4 binary gas mixtures which are associated with acetylene production and natural gas upgrading. In particular, compared to its isomer ZJNU-92, ZJNU-91 displays larger C2H2 and CO2 uptake capacities as well as higher C2H2/CH4 and CO2/CH4 adsorption selectivities under ambient conditions, despite its lower surface area and pore volume. On the basis of structural analyses, the better performance of ZJNU-91 compared to its isomer ZJNU-92 can be ascribed to its more optimized pore size.

Evaluating the effect of the substituents on structural stabilities and gas adsorption properties of MOFs is fundamentally important for rational design and synthesis of new MOFs with better performance. For this purpose, three isoreticular copper-based MOFs (ZJNU-87, ZJNU-88 and ZJNU-89) with ssa-type topology were successfully constructed from bent diisophthalate ligands bearing different substituents. Permanent porosity studies reveal that the substituent has a significant effect on framework stabilities against desolvation. Utilizing nonpolar n-hexane as an activation solvent can give more optimized permanent porosity for nonpolar or less-polar substituent-modified ZJNU-88 and ZJNU-89. Furthermore, their gas adsorption properties with respect to C2H2, CO2 and CH4 were systematically investigated, revealing their promising potential for selective C2H2/CH4 and CO2/CH4 separations. In particular, methoxy-modified ZJNU-89 performs better than the methyl-modified ZJNU-88 in terms of uptake capacity and adsorption selectivity, which might be attributed to more suitable pore space of ZJNU-89.

Manipulation of bubbles in water is of great importance in the mineral industry, oil production and separation, wastewater treatments, boiling processes, biological cell incubations, microfluidics and miniature reactor technologies. Generally, bubbles in an aqueous environment are inclined to stick to the channel walls, resulting in blockage and energy-consuming treatments. Herein, we report the fabrication of low-adhesion graphene-oxide (GO)/gold-nanoparticle (GNP) hybrid films with a good underwater superaerophobicity, which have the ability to arbitrarily manipulate bubbles in water. Owing to the hydrophilic nature of GO nanosheets and hierarchical structures of aggregated GNPs, the GO/GNP hybrid films showed low adhesion towards bubbles in water. Thus, bubbles could be freely manipulated using home-made tools coated with these low-adhesion, underwater superaerophobic GO/GNP hybrid films. The controlled 1D and 2D movements of one bubble and merging/reaction of two bubbles can be achieved. This study provides a new avenue to design new strategies for bubble manipulations, and further extends the application of superwettable 2D materials in interface fields involving gas phases.

We report a green fabrication of conductive paper based on in situ polymerization of polymerizable deep eutectic solvents (PDESs) through a screen printing process. By pre-designed circuit paths and careful integration, on-demand input/output 3D circuits can be achieved, showing its flexibility to origami electronics.

The ligand truncation strategy provides facile access to a wide variety of linkers for the construction of MOFs bearing diverse structures and intriguing properties. In this work, we employed this strategy to design and prepare a novel bent diisophthalate ligand, and used it to successfully construct a copper-based MOF ZJNU-51 with the formula of [Cu2L(H2O)2]·5DMF (H4L = 5,5'-(triphenylamine-4,4'-diyl) diisophthalic acid), which was thoroughly characterized by various techniques including FTIR, TGA, PXRD and single-crystal X-ray diffraction. ZJNU-51 is a two-fold interpenetrated network in which the single network consists of dicopper paddlewheel units connected by the organic ligands and contains open channels as well as six distinct types of metal-organic cages. Furthermore, gas adsorption properties with respect to C2H2, CO2, and CH4 were systematically investigated, demonstrating that ZJNU-51 is a highly promising material for C2H2/CH4 and CO2/CH4 separations. Specifically, the IAST adsorption selectivity at 298 K and 1 atm reaches 35.6 and 5.4 for the equimolar C2H2/CH4 and CO2/CH4 gas mixtures, respectively. More significantly, as revealed by PXRD and N2 adsorption measurements, ZJNU-51 exhibits excellent chemical stability, which lays a good foundation for its practical application.

Solid-state batteries (SSBs) have already attracted significant attention due to their potential to offer high energy density and excellent safety as compared to the currently used lithium-ion batteries with liquid electrolytes. The use of a lithium anode in SSBs is extremely important to realize these advantages. Starting from the synthesis of a highly conductive cubic garnet solid electrolyte (Li6.375La3Zr1.375Nb0.625O12, LLZNO) using Nb as a structure stabilizer, in this study, we demonstrated the resolution of interfacial problems between the garnet electrolyte and lithium anode and the integration of the lithium anode into garnet-based SSBs by modifying the as-synthesized LLZNO with a Sn thin film. Due to the Sn modification, the interfacial resistances between the garnet electrolyte and the lithium anode decreased approximately 20 times to only 46.6 Ω cm2. The fast and reversible lithium plating/stripping under high current densities and the excellent battery performance of Li/Sn-LLZNO/LiFePO4 full cells were achieved. This improvement is ascribed to the formation of a Li–Sn alloy interlayer, which severs as a self-limited stable and conductive interface, bridging the garnet electrolyte and the lithium anode and enabling fast and stable lithium transport. As a proof-of-concept, this effective surface modification method will offer inspirations to researchers for overcoming the interfacial problems and promoting the development of high-performance SSBs.

The electrochemical conversion of the greenhouse gas, carbon dioxide (CO2), to energy fuels and value-added chemicals presents one of the most valuable approaches to harvest pollutants and produce renewable energy. However, the stable molecular structure of CO2 and the sluggish reaction kinetics make CO2 reduction reaction (CO2RR) formidably challenging to achieve reaction rate and selectivity practical in industry. Graphene and its derivatives have been considered a group of intriguing materials to develop advanced CO2RR electrocatalysts due to their large specific surface area, remarkable electron transfer ability, superior stability, and easy tunability of the structure and surface properties. Herein, we comprehensively discuss the state-of-the-art electrocatalysts constructed with graphene and derivatives for active and selective CO2RR within the recent five years, mainly including the electrocatalysts with both metal-based (e.g., noble, non-noble, or combined thereof) and non-metal (e.g., doped, modified, defected, or composited) catalytic sites. To present the versatile, high-performance metal-based CO2RR electrocatalysts constructed with graphene, we further subdivide them according to the sizes, oxidation states, metal species synergies, dimensionalities, and versatility. Finally, we provide the challenges and perspectives in this emerging area of utilising CO2 to produce various carbon-based fuels and chemicals via graphene chemistry.

Ultra-tough transparent conductive elastomers (TCEs) with self-healing performance are of great significance for research in the fields of soft robotics, optical display electronics, wearable electronic equipment and human–computer interaction. However, their limitation, such as the desolventizing process, low polymerization rate or balance between toughness and self-healing performance, cause difficulty in manufacturing by the 3D printing technique. Here, we propose a novel preparation strategy for 3D printed TCEs based on the photopolymerization of maleic acid (MA)/choline chloride (ChCl) and acrylamide (AAm)/choline chloride type polymerizable deep eutectic solvents (PDESs). PDES can polymerize into a tough and rich in hydrogen bonds poly(PDES) in a few seconds without solvent evaporation. The printed TCEs with precision of 10 µm have high transparency (95.6%) and stable electrical signals at 50% compression for 10,000 cycles. In addition, efficient self-healing performance due to the dynamic hydrogen bonds of poly(PDES) provides broad application prospects for 3D printed TCEs in long-term pressure-resistant intelligent applications.

Spent coffee ground (SCG), left over in coffee making, is the most abundant coffee byproduct, of which approximately 70% is made by cellulose and hemicellulose. Herein, we obtained a delignified SCG (D-SCG) by using an aqueous solution of 3 wt% NaOH for 1 h at 90 °C and then an aqueous solution of 3 wt% NaClO2 buffered with acetic acid at pH 4.3 for 2 h at 90 °C, respectively. Next, we used the D-SCG to fabricate holocellulose nanofibers (HCNF) suspension by TEMPO-Mediated oxidation. Finally, HCNF suspension was manufactured into superhydrophobic foams for oil-water separation through freeze-drying and hydrophobic modification. The superhydrophobic foams showed good properties of oil absorption capacity (16 g/g), separation efficiency (98.5%) and continuous separation. This work presents a novel idea for the further application of SCG and provides an eco-friendly and sustainable oil absorbent material to solve oil spill.

Transparent conductive elastomers are an emerging platform for stretchable electronics, attractive due to their ability to sustain high physical deformations while still fulfilling optical/electrical functions. Poly(deep eutectic solvent)s (DESs) can serve as a new type of transparent conductive elastomers as a result of their low cost, green fabrication, non-toxicity and post-treatment-free advantages. Here, we report a 3D patternable (starfish type), transparent (transmittance of ∼81%), stretchable (strain up to 150%), and conductive (∼0.2 S m−1) elastomer based on the photopolymerization of the acrylic-acid/choline-chloride DES. The combination of transparency, elasticity, conductivity and patternability allows the poly(DES) elastomers to serve as flexible tactile/strain sensors. Our methodology has the potential to exploit the new application of poly(DESs), and opens up a new powerful route to fabricate all-organic transparent, conductive elastomers for a myriad of applications in future flexible electronics.

The rational design of high-performance, flexible, transparent, electrically conducting sensor attracts considerable attention. However, these designed devices predominantly utilize glass and plastic substrates, which are expensive and not environmentally friendly. Here, novel transparent and conductive woods (TCWs) were fabricated by using renewable wood substrates and low-cost conductive polymers. Polymerizable deep eutectic solvents (PDES), acrylic-acid (AA)/choline chloride (ChCl), were used as backfilling agents and in situ photopolymerized in the delignified wood, which endowed the materials with high transparency (transmittance of 90%), good stretchability (strain up to 80%), and high electrical conductivity (0.16 S m-1). The retained cellulose orientation and strong interactions between the cellulose-rich template and poly(PDES) endow TCWs with excellent mechanical properties. Moreover, TCWs exhibited excellent sensing behaviors to strain/touch, even at low strain. Therefore, these materials can be used to detect weak pressure such as human being's subtle bending-release activities. This work provides a new route to fabricate functional composite materials and devices which have promising potential for electronics applications in flexible displays, tactile skin sensors, and other fields.

In this paper, UV-curable castor oil-based polyfunctional polyurethane acrylate (COME-PUA) was synthesized via photo-click chemistry and isocyanate polyurethane reaction. Facile and highly efficient side-chain functionalization of castor oil (CO) was first achieved via thiol-ene photo-click chemistry with β-mercaptoethanol (ME). 1 H NMR result indicated that almost 100% conversion of double-bond in CO was observed within 10 min, and the average hydroxyl functionality of the obtained polyol COME was about 6. Next, COME was modified by isocyanate polyurethane reaction with hydroxypropyl acrylate (HPA), isophorone diisocyanate (IPDI) and PEG-200 as the chain extender in order to prepare the resin COME-PUA. Results of both 1 H NMR and FTIR revealed that the targeted COME and COME-PUA were successfully synthesized. Furthermore, UV-curing kinetic of COME-PUA was revealed by real-time FTIR, showing a higher UV-curing rate than the common CO-PUA. Finally, some physical properties of curing films were studied.

It is attractive, though it is very challenging, to synthesize conductive elastomers with high transparency and self-healing ability, simultaneously with facile and environmentally friendly preparation process. Here we demonstrate the fabrication of highly transparent, self-healing conductive elastomers based on synergistic hydrogen bonding interactions between poly(polymerizable deep eutectic solvent) (poly(PDES)) and phytic acid (PA) molecules. The hybrid network elastomers showed a fast self-healing property (within 2 s) without any other external stimuli and excellent self-healing efficiency (91.5%) within 48 h. The poly(PDES)-PA elastomers were highly transparent (an average transmittance of 93%), intrinsically conductive (an ionic conductivity of 7.8 × 10−4 S cm−1) and stretchable (strains up to 1300%). Furthermore, the abilities of healable & conductive poly(PDES)-PA elastomers to monitor the human activities retained no matter before or after being damaged. We believe this kind of dynamic bond manipulation is a powerful strategy to design and synthesize various transparent, self-healing, conductive elastomers for versatile applications.

The development of solid-state lithium-oxygen batteries is currently limited primarily by the high solid-solid interfacial resistance and the lack of efficient assembly of electrolyte and electrode. In this work, noncovalent interactions between the cations of an ammonium ionic liquid and both solid electrolytes and carbon air cathodes are introduced. The ionic liquid-based electrolytes (ILE) are solidified on Li6·40La3Zr1·40Ta0·60O12 (LLZTO) nanoparticles and gelated by multi-wall carbon nanotubes (MWCNTs), respectively, to construct LLZTO@ILE quasi-solid-state electrolyte (QSSE) and MWCNTs-LLZTO/ILE gel cathode (GC). The QSSE exhibits a high ionic conductivity of 1.71 × 10−3 S cm−1 at 60 °C, high Li-ion transference number of 0.56, broad electrochemical window of ~4.8 V and good thermal stability. The GC shows outstanding compatibility with QSSE. Quasi-solid-state Li–O2 batteries are assembled by integrating QSSE and GC films with a facile roll forming method, showing a low total interfacial resistance (~87 Ω cm2), and excellent reversible cycles (70 cycles) with low charge overpotential ( 70%) at 60 °C and 200 mA g−1. A 0.12 Ah pouch-type Li–O2 battery was achieved by this method. These results suggest that the noncovalent interactions initiated by IL cations could be an effective approach to solve the solid-solid interface issue and achieve high discharge capacity in solid-state energy storage devices.

Nanocomposite hydrogels consisting of a synthetic matrix reinforced by nanosized crystalline polysaccharides offer significant potential in various fields. Different from nanocellulose, the combination of nanochitin with synthetic polymers to obtain nanocomposite hydrogels has not been extensively and systematically studied. Herein, a physically and chemically dual crosslinked nanocomposite hydrogel was successfully synthesized, where chitin nanowhiskers (ChNWs) and Zn2+ were incorporated within polyacrylamide (PAAm) matrix. Nanochitin/metal ion dual reinforcement imparts increased elasticity, enhanced mechanical properties, and improved recovery performance to PAAm network. The PAAm/ChNWs/Zn2+ hydrogel could be stretched to over 13 times its original length with tensile strength of 321.9 ± 8.2 kPa, and restore its original shape rapidly even when compressed at a strain of 95% with a corresponding compressive strength of 6.95 ± 0.20 MPa. The multiple crosslinks and interactions among ChNWs, Zn2+ and synthetic polymeric network were investigated. Moreover, the hydrogel was applied in drug release and soft bioelectronics.

Developing green substrates based on cellulose to substitute synthetic plastics meet the requirement for the sustainable future. However, cellulose-based substrates supporting for building electronic devices are usually opaque and highly hydrophilic, which ultimately limits the performance of optoelectronic devices. Herein, we report a new avenue for fabrication of highly transparent, weakly hydrophilic and biodegradable cellulose film. The acquired cellulose film not only has high transparency (over 90%), but also displays weak hydrophilicity (∼79° of initial water-contact angle) and still remains 3.5 MPa of tensile strength after soaking for two days in deionized water. Additionally, the degradation half-life of cellulose film is 20 days, and the cellulose films also have better thermostability. Moreover, the flexible electroluminescent devices have been successfully constructed by using this cellulose film as a green substrate. This novel strategy will greatly enrich the applications of cellulose films for next generation green electronics.

To extend the applications of natural polymer-based hydrogels to wearable sensors, it is both important and a great challenge to improve their mechanical and electrical performance. In this work, highly stretchable, strain-sensitive, and ionic-conductive cellulose-based hydrogels (CHs) were prepared by random copolymerization of allyl cellulose and acrylic acid. The acquired hydrogels exhibit high stretchability (~142% of tensile strain) and good transparency (~86% at 550 nm). In addition, the hydrogels not only demonstrate better sensitivity in a wide linear range (0%&ndash, 100%) but also exhibit excellent repeatable and stable signals even after 1000 cycles. Notably, hydrogel-based wearable sensors were successfully constructed to detect human movements. Their reliability, sensitivity, and wide-range properties endow the CHs with great potential for application in various wearable sensors.

Nanopaper prepared from cellulose nanofibers (CNFs) is a kind of promising substrate for various high-tech devices. However, several drawbacks including poor water stability and weak corrosion resistance still remain, which limit the practical applications of the nanopaper. Herein, we present a simple and low-cost method for fabricating transparent and superhydrophobic nanopaper by spraying fluorinated silica/multi-walled carbon nanotubes (SiO2/MWCNTs) composite on the nanopaper. A series of functional nanopaper were fabricated, which shows excellent performance of water repellency, chemical stability, conductivity, thermostability and self-cleaning property. Among them, the nanopaper modified with the composite containing 0.5 wt% MWCNTs has a water contact angle of about 163°, transparency of 79.96% and the sheet resistance of 3.15 × 106 Ω sq−1. The combination of the promising features in a material offers attractive prospects, and enables our nanopaper could be tailored for emerging applications such as flexible electronics, display protection and intelligent packages.

Interfacial issues arising from the poor interface contact and poor interface stability between the stiff solid-state electrolytes (SSEs) and the electrodes have restricted the development of successful solid-state batteries (SSBs). Herein, we demonstrate that constructing flexible composite cathodes by introducing conductive frameworks consisting of succinonitrile and lithium salt significantly improves the contact performance and interface stability between garnet solid electrolyte and LiFePO4 cathode, enabling the resulted SSBs cycling steadily with high capacity even at room temperature. The introduction of such flexible frameworks not only enables close contact between the cathode and the stiff SSE, but also bridges every electrode and electrolyte particles together forming interconnected three-dimensional ionic conductive paths, reducing the total resistance to one-half of the batteries without such frameworks. On the other hand, the network is flexible enough to accommodate the volume change of LiFeO4 during cycling. These advantages endow that the SSBs of Li/SSE/LiFePO4 with the flexible composite cathodes demonstrate an initial discharge capacity of 149.8 mAh g−1 and the Coulombic efficiency of 99% after 100 cycles at 0.05 C under room temperature. This method demonstrated here to integrate electrodes and stiff electrolytes by introducing flexible components will provides inspirations for people to construct high-performance room-temperature SSBs.

Ssa-type MOFs constructed from dicopper paddlewheels and bent diisophthalate ligands exhibit a promising potential for gas adsorption which benefits from their rich open copper sites and polyhedron-based cages with suitable sizes. However, the rational construction of such types of MOFs is exceedingly challenging because the bent diisophthalate ligands employed are inclined to exhibit various conformations and thus are prone to form MOFs with varied topologies. In this work, by pre-organizing the ligand's conformation, we successfully targeted an ssa-type MOF ZJNU-57 from a bent diisophthalate ligand. More significantly, ZJNU-57 exhibits excellent hydrolytic stability and high C2H2 and CO2 uptake capacities as well as impressive C2H2/CH4 and CO2/CH4 adsorption selectivities, indicating its promising potential for C2H2/CH4 and CO2/CH4 separation, which are relevant to acetylene production and natural gas purification. This work not only provides a rare water-stable MOF based on the Cu2(COO)4 cluster for highly selective adsorption of C2H2 and CO2 from CH4, but also demonstrates that the ligand conformation-controlled assembly strategy may be an efficient approach toward the construction of MOF materials with definite topologies for specific applications.

The paper intended to research the influences of paper in UV ink-jet printer, mainly including the height and glossiness. Results proved that infiltrations had all appeared between three selected substrates of paper, on which the paper roughness and bulkiness had a linear effect. And the infiltration on the first layer of ink was bigger than those on other layers of ink. It is too stable to not be changed by the paper that the infiltrations between two layers of ink. As we knew, paper roughness and bulkiness would reduce the glossiness. There existed ink sticks on the third layer of ink and more, even some ink holes when the infiltrations were too big because of the substrate of paper had a bigger roughness and bulkiness. Therefore, the substrates used for UV ink-jet 3D printing should have a property of tight and smooth, and the first layer of ink must not be calculated in the whole height of model, so that the printing result would be satisfied.

A novel multivalent cations-triggered shape memory hydrogels were synthesized in a one-pot method, and interpenetrating double network was formed by chemically cross-linked polyacrylamide (PAM) network and physically cross-linked sodium carboxymethyl cellulose network. The temporary shape was fixed by complexation between a native biopolymer, sodium carboxymethyl cellulose (CMC), and transition metal ions, specifically Fe3+, Ag+, Al3+, Cu2+, Ni2+, and Mg2+. In particular, CMC-Fe3+ hydrogel exhibits excellent shape fixity ratio (95%). Therefore, we chose PAM/CMC1.0-Fe3+ hydrogel as the model material and further investigated its shape recovery process. It was found that a wide range of molecules and anions could be applied to break off the temporary cross-links between CMC and Fe3+. The PAM/CMC composite hydrogels also exhibited excellent tunable mechanical properties. The mechanical properties of the composite hydrogel can be adjusted by changing the cross-linking densities. The presented strategy could enrich the construction as well as application of biopolymers based shape memory hydrogels.

Conductive paper has low-cost, lightweight, sustainability, easy scale-up, and tailorable advantages, allowing for its promising potential in flexible electronics, such as bendable supercapacitors, solar cells, electromagnetic shields, and actuators. Ionic gels, exhibiting a lower Young’s modulus together with facile manufacturing, can fully serve as the conductive component to prepare conductive paper. Herein we report a low-cost (∼1.3 dollars/m2), continuous, and high-throughput (up to ∼30 m/min) fabrication of reliable and long-term (stable for more than two months) conductive paper. As-prepared conductive paper shows a high electrical durability with negligible bending–recovering signal changes over 5000 cycles. Using this ionic gel paper (IGP) as a key component, we build a variety of proof-of-principle demonstrations to show the capacity of IGP in constructing flexible electroluminescent devices with diverse patterns, including a square, an alphabetic string, and a laughing face. Our methodology has...

Nowadays biosource-based materials have received revitalized interest for their ability to substitute for petrochemical-based materials. In this paper, we report a facile synthetic method of soybean oil-based polyfunctional acrylate (PFA) for UV-curable materials. Specifically, rapid and highly efficient side-chain functionalization of soybean oil was achieved via photoclick thiol-ene reaction, soybean oil-based polycarboxylic acid (PCA) was thus obtained. Next, by DCC (N,N′-dicyclohexylcarbodiimide) catalyzed esterification reaction with hydroxypropyl acrylate, polyfunctional acrylate (PFA) was synthesized at room temperature. Real-FTIR result indicated that almost 100% conversion of double-bond within vegetable oil was observed within 16.7 min, yielding the soybean oil-based polycarboxylic acid quantitatively. Furthermore, the structure of PFA was confirmed by 1 H NMR and FTIR. Finally, the excellent UV-curing rate of PFA was revealed by real-FTIR.

Underwater vibration detection is of great importance in personal safety, environmental protection, and military defense. Sealing layers are required in many underwater sensor architectures, leading to limited working-life and reduced sensitivity. Here, a flexible, superhydrophobic, and conductive tungsten disulfide (WS2) nanosheets-wrapped sponge (SCWS) is reported for the high-sensitivity detection of tiny vibration from the water surfaces and from the grounds. When the SCWS is immersed in water, a continuous layer of bubbles forms on its surfaces, providing the sensor with two special abilities. One is sealing-free feature due to the intrinsic water-repellent property of SCWS. The other is functioning as a vibration-sensitive medium to convert mechanical energy into electric signals through susceptible physical deformation of bubbles. Therefore, the SCWS can be used to precisely detect tiny vibration of water waves, and even sense those caused by human footsteps, demonstrating wide applications of this amphibious (water/ground) vibration sensor. Results of this study can initiate the exploration of superhydrophobic materials with elastic and conductive properties for underwater flexible electronic applications.

In this work, we report on a flexible thermoelectric nanogenerator (NG) based on the MoS2/graphene nanocomposite. The nanocomposite thermoelectric nanogenerator shows enhanced thermoelectric performance, compared with that based solely on MoS2 nanomaterials, which may be due to the enhanced electrical conductivity resulting from the graphene acting as a charge transfer channel in the composites. The NG can be further applied as a self-powered sensor for temperature measurement. This work indicates that the MoS2/graphene nanocomposite is a promising thermoelectric material for harvesting environmental thermal energy.

Liquid-free ionic conductors are very desirable for flexible electronics, because hydrogels and ionic liquid-based ionogels suffer from water evaporation and ionic liquid leakage, respectively. However, the development of liquid-free ionic conductors with both high mechanical strength and stretchability remains challenging. In this work, based on the design concept of a double-network, we first report a series of very mechanically strong and tough liquid-free double-network ionic conductors (LFDNICs), consisting entirely of 1st stretchable poly(AA–ChCl) type supramolecular deep eutectic polymer networks and 2nd brittle polyvinylpyrrolidone (PVP) networks. One of these LFDNICs shows outstanding mechanical performance, with tensile strength, strain at break, and toughness up to 71.3 MPa, 671%, and 268 MJ m−3, respectively. In particular, the LFDNIC can endure puncture and successfully elevate a 10 kg weight (12 500 times its own weight). In addition, the LFDNIC also exhibits promising ionic conductivity (3.1 × 10−4 S m−1), favorable biocompatibility (cell viability up to 97.5%), optimum self-healing properties (electrical healing efficiency of 98% within 0.30 s), and adequate transparency (92% in the visible range). Due to their practical features and exceedingly simple preparation process, we believe that LFDNICs will not only provide an innovative prospect for the development of mechanically-strong ionic conductors, but can also be further researched and used in the fields of advanced sensors and flexible electronic devices.