Cross-linked cellulose nano-sponges: a small angle neutron scattering (SANS) study Abstract Cellulose nano-sponges (CNS), obtained by cross-linking TEMPO oxidized and ultra-sonicated cellulose nano-fibers (TOUS-CNFs) with branched polyethyleneimine (bPEI), underwent here a systematic small angle neutron scattering investigation, by varying the amount of cross-linker and the water content. The aim was to provide experimental evidence of nano-porosity in the TOUS-CNF network of these nano-sponges (CNSs) by investigating the water nano-confinement geometries in the adsorbent material. Moreover, we also verified how the breaking/reformation of specific intermolecular hydrogen bond interactions between water and the chemical groups present in the architecture of the CNSs could contribute to regulate the water adsorption process observed at macroscopic level. The analysis of the experimental data, performed in terms of the correlation length model, allowed us to extract the short-range correlation length ξ, interpreted as a very first indirect estimation of the effective nano-dimension of the cavities produced by the cross-linking of the reticulated cellulose nano-fibers. From the model, power-law (n) and Lorentzian (m) exponents have been also obtained, associated with the density of TOUS-CNFs at high (larger than hundreds of Å) and low (~ 10–100 Å) spatial scales, respectively. These parameters were all sensitive to the structural variations induced by the progressive uptake of water on the bPEI/TOUS-CNF sponges with different bPEI:TOUS-CNF (w/w) ratios. Finally, we investigated the effect of the addition of citric acid in the CNS formulation, confirming its role in increasing cross-linking density and sponge rigidity. The obtained results appear crucial in order to rationalize the design of these sponges and to track the changes in the ability of the final products as efficient nano-confinement systems for water. Graphic abstract

Correction to: Hydrothermally induced changes in the properties of MFC and characterization of the low molar mass degradation products In the original publication, the less than symbol (<) was mistakenly processed as greater than symbol (>) in Tables 2 and 4.

Highly reversible photochromism in composite WO 3 /nanocellulose films Abstract Reversible photochromic hybrid organic–inorganic films containing nanocrystalline cellulose as a matrix and tungsten oxide as a photochromic component (CNC/WO3) were obtained via a simple and quick solvent casting method. The films were studied by scanning electron microscopy, together with element mapping, FT-IR spectroscopy and X-ray diffraction, confirming successful incorporation of WO3 nanoparticles into a nanocellulose matrix. Thermal analysis data indicated that the modification of a nanocellulose matrix with WO3 increases its thermal stability. The CNC/WO3 films showed a quick coloration-bleaching transition with good reversibility within 20 min, without notable degradation of photochromic properties after 10 cycles. The synthetic method proposed allows for scalable preparation of highly efficient low-cost WO3-based photochromic materials. Graphic abstract

2D nitrogen-doped porous carbon nanosheets derived from cellulose nanofiber/silk fibroin nanohybrid cellular monoliths with promising capacitive performance Abstract 2D nitrogen-doped porous carbon nanosheets are prepared from cellulose nanofiber/silk fibroin nanohybrid cellular monoliths via unidirectional freeze-shaping technique, carbonization, and CO2 activation processes. The micromorphology of the cellulose nanofiber/silk fibroin nanohybrid cellular monoliths can be effectively controlled by simply changing the content of silk fibroin. The 2D nitrogen-doped porous carbon nanosheets (NPCN-X, X represents the content of silk fibroin), inherited from different cellular monolith, show a distinct micromorphology. The NPCN-50 exhibits the best electrochemical performance due to its 2D nanostructure, abundant multi-scale through pores, high specific surface area (about 1882 m2 g−1), and appropriate surface N/O-doping. The largest gravimetric capacitance value is about 329.9 F g−1 at a current density of 0.25 A g−1. The energy density reaches as high as 37.5 Wh kg−1 at a power density of 186.3 W kg−1. The NPCN-50 also exhibits excellent electrochemical cycling stability. Graphic abstract

Development of mechanically durable hydrophobic lanolin/silicone rubber coating on viscose fibers Abstract We report on a simple technique for the production of mechanically durable water-repellent layer on viscose fibers via spray-coating of a lanolin-silicon rubber solution in petroleum ether. Depending on the silicon rubber solution concentration, it was achievable to gain surfaces with hierarchical morphology. Extracted lanolin was admixed with a mixture of a room temperature vulcanizing silicon rubber and petroleum ether to afford the silicon rubber-lanolin formulation, which was applied successfully onto viscose fabrics employing spray-coat procedure. The surface characteristics of the spray-coated viscose fibers were studied by scanning electron microscope, energy dispersive X-ray analysis, and static water contact and sliding angle measurements. The alteration in the chemical composition of viscose-treated fabric was studied using Fourier-transform infrared spectroscopy. The wetting behavior was found to be a function of silicon rubber concentration in ether solution affording coatings with high static water contact angle and low sliding angle values. The treated viscose fabric exhibited excellent ultraviolet protection and enhanced hydrophobicity without adverse effect on its inherent physico-mechanical properties. The comfort characteristics of spray-coated viscose fibers were also evaluated by studying their air-permeability and stiffness. The results displayed durable water-repellent properties of the treated viscose, introducing a good opportunity for a large-scale manufacture of water-repellent textiles for a diversity of industrial purposes.

Morphological study of cellulosic hydrogel nanofiber for biomedical application Abstract In this work, water-insoluble and biocompatible hydrogel nanoweb was prepared via electrospinning. Sodium carboxymethyl cellulose (CMCNa), the cellulose derivative with water solubility and biocompatibility, was electrospun with help of building polymer, poly(ethylene oxide) (PEO). After removal of PEO, the CMCNa in the nanoweb was ionically crosslinked by FeCl3. The viscosity of the mixed solution was decreased with the increase of PEO content mainly due to the smaller molecular size of PEO comparing to CMCNa. The reduced interaction resulted from small molecular size decreased the viscosity with the increase of PEO content. The PEO also improved the spinnability of the solution by screening repulsive force between the CMCNa molecules. As a result, the increase of PEO content resulted in the decreases of the viscosity and the fiber diameter simultaneously. After extraction of PEO, the diameter was significantly reduced. The surface of the nanowebs became bumpy after crosslinking and fiber diameter increased with the increase of crosslinking time. The chemical structure changes of the nanowebs during the process were analyzed by FT-IR spectra. The cytotoxicity of the nanoweb was also assessed using MTT assay. Furthermore, the drug release behaviors of the nanowebs were evaluated using UV–Vis spectrometer. The nanoweb with increased fiber diameter showed more sustained release behavior because of its low specific surface area.

Editable and bidirectional shape memory chitin hydrogels based on physical/chemical crosslinking Abstract Advances in soft robotics have enabled rapid progress in shape memory hydrogels, including unidirectional, bidirectional and multidirectional shape memory hydrogels. However, shape memory hydrogels with editable feature have hardly been reported. Here, chitin based bilayer hydrogels were prepared based on alkali/urea aqueous system. Due to the different swelling properties of the two layers, namely physical crosslinking layer and chemical crosslinking layer, the hydrogels can bend toward opposite direction in water and ethanol, showing a bidirectional shape memory behavior. Meanwhile, this bidirectional shape memory hydrogels can be programmed to different shapes with external force after immerging in alkali solution as a result of the hydrogen bond breakage and reformation via hydroxyl ion, displaying an editable feature. We believe that the editable and bidirectional shape memory chitin bilayer hydrogels have great potential in soft robotics. Graphic abstract

Chitosan-assisted synthesis of wearable textile electrodes for high-performance electrochemical energy storage Abstract Through a facile “dipping and drying” process, reduced graphene oxide, here simply referred to as “graphene”, was successfully coated onto a commercial textile substrate, resulting in a high-performance supercapacitor electrode with excellent flexibility and stretchability. With the assistance of difunctional chitosan (for dispersing and gluing), a high graphene loading amount of 5.5 mg cm−2 was achieved on cotton textile within 10 soaking times. The graphene@cotton-10 had a low sheet resistance of 1.75 Ohm sq−1, which merely increased 0.51 and 0.78 Ohm sq−1 when being bent at 180° and stretched with 100% strain, respectively. In a three-electrode configuration, the areal specific capacitance of the graphene@cotton-10 reached up to 232 mF cm−2 at the current density of 1 mA cm−2, which was superior to most of the carbon@textile flexible electrodes reported so far. The resulting graphene@cotton-10 symmetrical supercapacitor had a decent energy density of 4.38 μWh cm−2 at 5 mW cm−2. Cycling test revealed the supercapacitor had more than 80% retention of its initial capacitance after 5000 cycles at 5 mA cm−2, demonstrating an outstanding long-term durability. Furthermore, the synthesis methodology established in this study is simple, efficient and environment-friendly, which possesses a great potential for large-scale practical applications.

Enhanced photovoltaic properties of perovskite solar cells by the addition of cellulose derivatives to MAPbI 3 based photoactive layer Abstract In this study, chlorodeoxyhydroxyethylcellulose (CDHC) was synthesized from hydroxyethylcellulose (HEC) through chlorination and then both HEC and CDHC were applied individually as additives within the methylammonium lead iodide (CH3NH3PbI3, MAPbI3) layers of perovskite solar cells (PVSCs). The architecture of the PVSCs was indium tin oxide/poly(3,4-ethylenedioxythiophene):polystyrenesulfonate/MAPbI3:cellulose derivative/[6,6]-phenyl-C61-butyric acid methyl ester/Ag. The photovoltaic (PV) properties of the HEC- and CDHC-incorporated PVSCs were superior to those of the corresponding pristine PVSC prepared without an additive, a result of decreases in the number of grain boundary defects as well as increases in the crystal grain sizes, crystallinities, and absorption intensities of the modified perovskite films. Moreover, the polymer chains of CDHC, presenting chlorine atoms, were particularly beneficial for enhancing the crystal size and crystallinity of the MAPbI3 film, resulting in the highest absorbance and PV performance in this study being those of a CDHC-doped PVSC. Indeed, this CDHC-incorporated PVSC displayed a short-circuit current density of 17.73 mA cm−2, an open-circuit voltage of 0.96 V, a fill factor of 0.61, and a power conversion efficiency of 10.38%. Graphic abstract

A kinetic study on the hydrolysis of corncob residues to levulinic acid in the FeCl 3 –NaCl system Abstract Levulinic acid (LA) production from corncob acid hydrolysis residues (CAHR) using FeCl3 as Lewis acid catalyst in green solutions of salt was investigated. The reaction kinetic relationships were determined in the temperature range of 160–180 °C, with FeCl3 concentrations of 0.12–0.36 M, and a reaction time of 0–60 min. The maximum LA concentration of 59.0 mol% (24.5 g/L) was achieved at 170 °C in a 30% NaCl solution containing 0.24 M FeCl3. A pseudo first-order kinetic model was proposed to describe the cellulose deconstruction to LA. The model agreed perfectly with the evolution in the concentrations of the major compounds such as glucose, 5-hydroxymethylfurfural and LA during the CAHR hydrolysis. The kinetic model developed for CAHR was in good agreement with that previously developed for other lignocellulosic systems. Based on our kinetic model and reaction system, the LA yield is increased at the lower end of the temperature range with the higher acid concentrations. The results indicated that the concentrated seawater after desalination could be a green solvent in the biorefinery.