The weak stiffness, huge thickness, and low specific capacitance of commonly utilized flexible supercapacitors hinder their great electrochemical performance. Learning from a biomimetic interface strategy, we design flexible film electrodes based on functional intercalated structures with excellent electrochemical properties and mechanical flexibility. A composite film with high strength and flexibility is created using graphene (reduced graphene oxide (rGO)) as the plane layer, layered double metal hydroxide (LDH) as the support layer, and cellulose nanofiber (CNF) as the connection agent and flexible agent. The interlayer height can be adjusted by the ion concentration. The highly interconnected network enables excellent electron and ion transport channels, facilitating rapid ion diffusion and redox reactions. Moreover, the high flexibility and mechanical properties of the film achieve multiple folding and bending. The CNF-rGO-NiCoLDH film electrode exhibits high capacitance performance (3620.5 mF cm-2 at 2 mA cm-2), excellent mechanical properties, and high flexibility. Notably, flexible all-solid assembled CNF-rGO-NiCoLDH//rGO has an extremely high area energy density of 53.5 mWh cm-2 at a power density of 1071.2 mW cm-2, along with cycling stability of 89.8% retention after 10 000 charge-discharge cycles. This work provides a perspective for designing high-performance energy storage materials for flexible electronics and wearable devices.

Solar -thermal conversion is an efficient and convenient method that utilizes solar energy and has attracted significant attention. In this study, efficient TEMPO -oxidized nanocellulose/antimonene (TOCNF/Sb) photothermal composite films were successfully fabricated using a TOCNF layer -by -layer self -assembly strategy during vacuum -assisted filtration. TOCNF substantially improved the mechanical properties of the few -layer antimonene nanosheet film, yielding an excellent tensile strength of 302.89 MPa and toughness of 18.27 MJ/m 3 . The temperature of the TOCNF/Sb composite films reached 80.3 degrees C under 1 sun irradiation, and the maximum temperature was achieved within 80 s. Owing to the photothermal properties of the TOCNF/Sb composites film, the solar thermoelectric generator with the TOCNF/Sb composite film could generate a voltage of 86 mV under outdoor solar irradiation, demonstrating the feasibility in the field of solar power generation.

Via rational molecular structure design and using gallic acid (GA) for hydrophobic modification of cellulose nanofibers (CNF), the "polymer dipole" CNF-GA with hydrophilic main chains and hydrophobic side chains was prepared, which improved the poor piezoelectric properties of CNF used for preparing pressure sensors. Due to the appearance of the side chains, the elongation at break of the CNF-GA-2, compared with CNF, was enhanced by 186 %, and the excellent tensile strength, puncture load, and tearing strength were displayed. Moreover, the significant glass transition temperature (Tg) near the human body temperature was exhibited for CNF-GA, making it possible to be applied in temperature sensing. Most importantly, the CNF-GA-2 showed the maximum hydrophobicity, with a contact angle of 76.77°. Finally, the CNF-GA-2/MXene nanocomposite film was prepared by the CNF-GA-2 with MXene through vacuum filtration. The results indicated that the film had excellent piezoelectric properties (d33 = 63.283), the generated stable induced voltage (125.6 mV), the preferable piezoresistive performance (ΔR/R0 = 2.15), the fast response/recovery time (48/61 ms), which could achieve dynamic and static responses. Moreover, this film could be used for real-time detection of limb movements (such as wrists).

Noncovalent interactions are vitally important to understand the structural stability and molecular assembly of cellulose and its analog molecules. Using density functional theory in conjunction with three popular generations of dispersion correction (D2, D3, D4), we systematically estimate the strength of inter-chain interaction for several β-1,4-linked crystalline polysaccharides (cellulose Iα, Iβ, II, IIII, α-chitin, β-chitin, chitosan) and their building block monomers (glucose, cellobiose). Switching on and off dispersion correction and combining the calculation of condensed and isolated chains allow the extraction of the intra- and inter-chain London dispersion interactions and the inter-chain electrostatic interaction. Regardless of the generations of dispersion correction and allomorphs, the estimated inter-chain London dispersion interaction is 45 74 kJ/mol per pyranose ring comparable to the inter-chain electrostatic interaction (47 88 kJ/mol). The upper limit of the strength of inter- or intra-chain hydrogen bonds is estimated to be 27 50 or 21 53 kJ/mol, respectively, based on energy profiles of hydroxy rotation. Our work quantitatively highlights that it is the London dispersion interaction rather than the hydrogen bonding interaction dominating in the tight assembly of polymer chains for β-1,4-linked crystalline polysaccharides, regardless of the crystal allomorph and types as well as the generations of dispersion correction of DFT. Thus, London dispersion interaction should be preferentially considered during their deconstruction, defibrillation, or dissolution processes.

Due to the rising need for clean and renewable energy, green materials including biochar are becoming increasingly popular in the field of energy storage and conversion. However, the lack of highly active and stable electrode materials hinders the development of stable energy supplies and efficient hydrogen production devices. Herein, we fabricated stable, conductive, and multifunctional chitosan microspheres by a facile emulsion crosslinking solution growth and hydrothermal sulphuration methods as multifunctional electrodes for overall water splitting driven by supercapacitors. This material possessed three-dimensional layered conductors with favorable heterojunction interface, ample hollow and porous structures. It presented remarkably enhanced electrochemical and catalytic activity for both supercapacitors and overall water electrolysis. The asymmetric supercapacitors based on chitosan biochar microsphere achieved high specific capacitance (260.9 F g−1 at 1 A g−1) and high energy density (81.5W h kg−1) at a power density of 978.4 W kg−1. The chitosan biochar microsphere as an electrode for electrolyze only required a low cell voltage of 1.49 V to reach a current density of 10 mA cm−2, and achieved excellent stability with 30 h continuous test at 20 mA cm−2. Then, we assembled a coupled energy storage device and hydrogen production system, the SCs as a backup power source availably guaranteed the continuous operation of overall water electrolysis. Our study provides valuable perspectives into the practical design of both integrated biochar-based electrode materials and coupled energy storage devices with energy conversion and storage in practical.

A green electrode material with dual conductive networks via electrospinning with carbonization and coprecipitation method is constructed. Nitrogen-based carbon nanofiber network (CCP-N) is used as the inner-conductive, electrochemical-active substrate and flexible skeleton. The Co Ni layered double hydroxide (Co Ni LDH) nanosheets and flower-like nanospheres, which randomly and closely covering the surface of CCP-N, respectively, just as the fungus grow on trunks in nature, is regarded as outer-conductive and active substance collector in order to provide abundant active centers, sufficient reaction interface to advance fast electrolyte ions diffusion and electrons transport. Furthermore, the growth process of Co Ni LDH on CCP-N is observed by controlling growth time and the Co/Ni ratio of the precursor solution. It is found that the optimal Co/Ni ratio was 2:1, while that optimal growth time is 12 h. The specific capacitance of Co Ni LDH@CCP-N electrode reaches 1319.4 F g-1 at 1 A g-1. The assembled asymmetric supercapacitor device (CCP-N @ Co Ni LDH//CCP-N) possesses a high energy density of 48.1 W h kg-1 at power density of 576.8 W kg-1, excellent cycling stability of 82.2% retention after 10,000 cycles. The results clearly indicate the Co Ni LDH@CCP-N materials have enormously potential in energy storage. This work puts forward a novel strategy for the design and fabrication of green and advanced supercapacitors materials with high power density and energy density.

Corn straw core (CSC) is considered as a promising biodegradable packaging material, owing to good ultraviolet (UV) and water vapor barrier properties. Nonetheless, if CSC will be used for packaging materials, some challenges, such as no mechanical strength (not-forming), poor water resistance, and lack of antimicrobial properties, still exist. To overcome these limitations, novel cellulose nanofibers (CNF)/CSC nanocomposites were developed, characterized, and demonstrated for potential food packaging applications. The reaction between CSC and CNF and the structures of CNF/CSC films were analyzed by FTIR, XRD, SEM, TG and DMA. Compared with CNF, polypropylene (PP), poly (butylene adipate-co-terephthalate) (PBAT) or poly (butanediol sebacate - butanediol terephthalate) (PBSeT), the tensile strength of CNF/CSC-100 film was advanced by 0.63 times, 1.25 times, 4.71 times or 8.04 times, respectively; the tearing strength of CNF/CSC-100 film, compared with PP, low density polyethylene or PBSeT, was improved by 19.79%, 66.96% or 49.61%, respectively; moreover, water vapor barrier property of CNF/CSC-100 film was enhanced by 57.69% or 46.59% than CNF and PBAT, respectively. The CNF/CSC films were also presented a superior UV barrier (UPF of 47.91–101.15) and wonderful bacteria blocking properties. In the bacteria blocking test, the growth of microorganisms using CNF/CSC-100 film was restricted to 12 days. In practical packaging tests with fresh garlic and milk, the weight loss and spoilage by external influences were effectively prevented by CNF/CSC films, which indicated the potential as food-packaging.

Flexible electrode materials have achieved great breakthroughs during the past decades. However, many challenges remain such as how to overcome the frangibility and enhance the flexibility, and advance the high specific capacitance. We fabricated a free-standing, foldable, and conductive cellulose acetate (CA)-based metal-organic framework (MOF) composites by facile electrospinning carbonization and co-precipitation method. The sustainable cellulose derivative provides a flexible matrix, which contains hierarchically porous and ample redox activities. The intermolecular interaction is enhanced for coordination between exposed hydroxyl on deacetylated CA and metal ions, thus reduce the fracture of the CA nanofibers. Importantly, multi-layer heterojunction structure and honeycomb-like MOF nanosheets with reversibly flexible deformation create interlamellar pathways to improve the bending resistance of nanofibers. The controlled Co/Zn ion concentration could effectively modulate spatial distribution of Co/Zn MOF to thus generate different conductive channels. The asymmetric flexible supercapacitor based on Ni/Co LDH@ Co/Zn NC@CDCP-N electrode material gives high specific capacitance (175.2 F g-1 at 1 A g-1) and outstanding energy density (54.8 W h kg-1) at high power density (985.5W kg-1). Our work paves a way to facile fabrication of flexible and free-standing electrode materials for practical flexible energy storage, such as artificial electronic skin and soft wearable electronics.

Due to the growing demand for clean and renewable energy, the effective utilization of renewable resources in energy storage and has been concerned. And high specific capacitance and stable electrochemistry for energy storage devices are challenging to develop. Learning from unique structure of goniastrea coral, we design to construct three-dimensional layered conductive electrodes material made of MoS2@chitosan carbon spheres (MNCCS) composite. The NiCoLDH nanosheets construct on the surface of conductive chitosan carbon spheres to effectively form open permeable channels and rich conductive networks, improves the efficient energy storage and electrochemical stability. MoS2 is strongly coupled with NiCoLDH nanosheets through heterointerface, which resembles tentacles on the surface of coral, exposing more active sites to efficiently trap ions. Besides, the obtained material possesses favorable heterojunction interface and defects, which provide sufficient available electroactive sites and numerous storage charge area. Hence, The MNCCS presents an outstanding specific capacitance of 2605.9 F g-1 at 1 A g-1. Notably, a supercapacitor fitted with MNCCS electrode and CCS electrode achieves high specific capacitance (234.4 F g-1 at 1 A g-1), the maximum energy density of 77.0W h kg-1 at highest power density of 667.4W kg-1 , along with the excellent cycling stability of 90.8% retention over 10,000 cycles. This work provides a new perspective for fabricating high-performance and stable supercapacitors electrode material for clean energy storage.

Porous carbon aerogels derived from abundant biomass, which possess a unique structure, a high specific surface area and heteroatom doping, are a promising electrodes material for supercapacitors (SCs). In this study, an innovative hierarchical porous material comprising cobalt decorated porous carbons derived from cellulose nanofiber / graphene / Zn/Co ZIF carbon aerogels (CRZCs) has been successfully synthesized by directional freeze drying and carbonization methods. Cellulose nanofibers (CNFs) and graphene (rGO) layers play not only a supporting role, but also an internal storage site for electrolytes, contributing to the diffusion of electrolytes to the surface of active substances, at the same time enhance hydrophilicity of the aerogel and contribute to uniformly disperse Zn/Co ZIF. What's more important is that the carbon aerogels possess hierarchical porous involving micropores, mesopores and macropores, which further aid electrolyte penetration and ion storage. Furthermore, benefiting from the synergetic effect of hierarchical porous, high surface area, high conductivity, the prepared CRZC electrode obtains a high specific capacitance (364.6 F g(-1) at 1 A g(-1)), an extraordinary capacitance retention rate (83.4 % at 10 A g(-1)). Simultaneously, the assembled supercapacitor by CRZC 900 exhibits a high specific capacitance (121.4 F g(-1) at 0.5 A g(-1)), good charging/ discharging rates, and remarkable cycling stability (78.9 % capacitance retention over 10000 cycles). The energy density up to 18.9 Wh kg(-1) is achieved at power density of 288.4 W kg(-1), indicating its comprehensive applicability in energy storage. Finally, our results provide a general approach to construct hierarchical porous carbon aerogels for high-performance supercapacitors. (C) 2022 Published by Elsevier B.V.

Exploring and fabricating smart actuating materials that strike the perfect balance between humidity response and mechanical integrity (especially wet tensile strength) via reasonable structural design and simple yet low-cost preparation is critical for biomimetic devices, soft robotics, artificial muscles and generators, but it remains challenging. Herein, inspired by the structure of natural nacre, we demonstrated a robust yet highly sensitive composite film-based humidity actuator composed of carboxymethyl cellulose (CMC), MXene nano-sheets, and multivalent aluminum ions (Al3+) via a facile evaporation-induced self-assembly method. The synergistic reinforcing effects of MXene nanosheets and Al3+ through hydrogen and ionic bonding as well as the densely hierarchical microstructure endow the composite film with both an ultrahigh mechanical strength (273.6 MPa), a desirable toughness (7.95 MJ/m(3)) and even an impressive wet tensile strength (154.2 MPa) at 97 % humidity. Interestingly, the unique laminated structure and water-induced swelling effect of CMC and MXene synergistically enable the composite film with large shape deformation, sensitive actuation (less than 2.3 s) and exceptional cycling stability (over 1500 cycles) upon exposure to humidity gradients. Based on the above merits, the composite film actuator can be well constructed to simulate a flying dragonfly, human finger, artificial muscle, and has also been preliminarily employed as a moist-electric generator, which provides new insight for designing comprehensive composite film-based actuators and reveals their extensive applications.

Intermolecular hydrogen bond, a kind of basic van der Waals bonds, commonly exists in biological systems. As a fundamental step in biological metabolism, the disassembly process of hydrogen bond is necessary to be given more attention. Here, we have demonstrated the disassembly of intermolecular hydrogen bond by scanning electrochemical microscopy. The intermolecular hydrogen bond was designed between the hydroxyl of ferrocenemethanol (FcCH(2)OH) and the carboxyl group of 3-mercaptopropionic acid (3-MPA), and FcCH(2)OH was bonded on 3-MPA self-assembled monolayermodified electrode surface. Cation (Mg2+, Ca2+ or Ba2+), as an external stimulus, induced the disassembly of hydrogen bond by forming ion-pairwith terminal carboxylate anion. Furthermore, the inducing capability of cation wasMg(2+) < Ca2+ < Ba2+ in order based on the strength of ion-pairs between cation and carboxylate anion. The degree of disassembly was effectively regulated by the different ratio of additional mixed cations. According to the positive induction of cation on disassembly of intermolecular hydrogen bond, a practicable and effective approach was provided for field application of molecular recombination and medical bioengineering. (C) 2020 Elsevier B.V. All rights reserved.

Defects on self-assembled monolayers (SAMs) could have detrimental impact on their functionalities; thus, to optimize performances, researchers seek to manipulate the defects of SAMs. In this work, we functionalized the defects of 1-undecanethiol SAMs using a zwitterion, cysteine. This modification with cysteine endowed the defects with a specific behavior of charge reversal. Scanning electrochemical microscopy and cyclic voltammetry both fully exhibited this charge reversal behavior. This peculiar ability of charge reversal at the defects would endow the SAMs specific functions: the SAMs have reversible electrochemical response to charged molecules. On the basis of this principle, the functionalized SAMs could be applied in specific amino acids recognition. This work supplied a practical way to take advantage of the defects of SAMs and offers some contribution to the fields of defect engineering and molecular recognition.

Controllable release of dopamine (DA) is worth studying for its significant in physiological metabolic process. β-cyclodextrin/11-mercaptoundecanoic acid self-assembled monolayer (β-CD/MUA SAM) based on hydrogen bonds network was constructed as simulated enzyme-containing biomembrane. DA interacted with β-CD based on intermolecular hydrogen bond and formed inclusion complexes in SAM, namely DA@β-CD/MUA SAM. The desorption process of DA from DA@β-CD/MUA SAM revealed the release behavior of DA from enzyme-containing biomembrane at molecular level. Positive biased potential as external stimulus was applied at DA@β-CD/MUA SAM, reducing the negative charge density of SAM. The decrease of negative charge density of SAM resulted in the weakening of hydrogen bond between DA and β-CD, which in turn caused DA to be released. Using scanning electrochemical microscopy, positive biased potential not only had specificity induction for the release of DA, but also was able to monitor the release quantitatively in real time. These results showed that positive biased potential as external stimulus was favorable for the controllable release of DA, suggesting the possible application of biased potential in controllable regulation field.

Probing a switch on biomimic membrane surfaces would offer some references to the research on permeability of cytomembranes. In this work, a mixed 11-mercaptoundecanoic acid/1-undecanethiol self-assembled monolayer (MUA/UT SAM) was constructed as a model of a biomembrane. In this mixed SAM, the MUA molecules work as functional parts for the switch and the UT molecules work as diluents. The surface coverage, wetting property, and pK(a) of this mixed SAM all have been well-inspected. The mixed SAM exhibits excellent switchable properties for cations, which is well-monitored by scanning electrochemical microscopy. When the pH of a solution is higher than the pK(a), protons would stimulate a shift of dissociation equilibrium of terminal carboxyl groups. The dissociated carboxylate ions would lead to a switch on the state of the SAM. Otherwise, the SAM shows an off state when the pH is lower than the pK(a). In addition, the repeatability, applicability, and the mechanism of the switch all have been well-evaluated.

The preferential solvation of water plays an important role in ferrocene research which is a subject of current interest. Voltammetric investigations were carried out for Au electrode in acetonitrile/water, showing preferential solvation of water. In our work, the preferential solvation of water in acetonitrile/water was studied by electrochemical methods including cyclic volitammetry, electrochemical impedance spectra and double-step chronoamperometry. Ferrocenemethanol (FcCH(2)OH) molecules as a solute spontaneously adsorb on the electrode surface in anhydrous acetonitrile, resulting from acetonitrile molecules tend to form an acetonitrile solvent layer on the surface of the electrode and acetonitrile solvent layer has a lower energy barrier than the aqueous solvent layer, which has been obtained by modeling solvation. The solvent strongly influences electrochemical behavior of solute. Once there is an amount of water in acetonitrile solvent, FcCH(2)OH that adsorbed on the electrode surface desorb. This is because water preferentially solvate with FcCH(2)OH in term of intermolecular forces between solvent and solute. Moreover, hydrogen bond between water molecules and FcCH(2)OH molecules is stronger than dipole-dipole interaction between acetonitrile molecules and FcCH(2)OH molecules in solvation effect. Through electrochemical behavior of FcCH(2)OH changing, preferential solvation of water is analyzed by electrochemical methods.

The topic of intermolecular interactions enhancing electron tunneling between protein residues on biofilm surface has been investigated by some theoretical studies. However, few of experimental studies could confirm this viewpoint. In this work, the Mercaptopropionic acid self-assembled monolayer (MPA SAM) with terminal carboxyl groups was constructed, as a simplified model for functionalized biomimic membrane. The electron tunneling rate constant of ferrocenylmethanol redox process on SAM was obtained from experimental results of scanning electrochemical microscopy. It is found that the electron tunneling across MPA SAM is faster than that of contrastive Methyl mercaptopropionate SAM. This result is attributed to the intermolecular interactions between the redox and MPA molecules. The conditions of lower pH and weaker ion pair effect all benefit the formation of the intermolecular interactions, resulting the enhancement of electron tunneling more obvious. Based on this, this kind of intermolecular interaction is inferred to be intermolecular hydrogen bond. Our work may have contributions to exploring electron tunneling between protein residues on biofilm surface.