Superelastic carbon aerogels with anisotropic and hierarchically-enhanced cellular structure for wearable piezoresistive sensors.

Elastic carbon aerogels have promising applications in the field of wearable sensors. Herein, a new strategy for preparing carbon aerogels with excellent compressive strength and strain, shape recovery, and fatigue resistance was proposed based on the structure design and carbonization optimization of nanocellulose-based precursor aerogels. By the combination of directional freezing and zinc ion cross-linking, bacterial cellulose (BC)/alginate (SA) composite aerogels with high elasticity and compressive strength were first achieved. The existance of zinc ions also significantly improved the carbon retention rate and inhibited structural shrinkage, thus making the carbon aerogels retain ultra-high elasticity and fatigue resistance after compression. Moreover, the carbon aerogel possessed excellent piezoresistive pressure sensing performance with a wide detection range of 0-7.8 kPa, high sensitivity of 11.04 kpa-1, low detection limit (2 % strain), fast response (112 ms), and good durability (over 1,000 cycles). Based on these excellent properties, the carbon aerogel pressure sensors were further successfully used for human motion monitoring, from joint motion to and speech recognition.

Frost-resistant nanocellulose-based organohydrogel with high mechanical strength and transparency.

Improving mechanical strength and frost-resistance is an important research direction in the field of hydrogel materials. Herein, using bacterial nanocellulose (BC) as a reinforcing agent and polyvinyl alcohol (PVA) as a polymer matrix, a frost-resistant organohydrogel was constructed via the freezing-thawing method in a new binary solvent system of N, N-dimethylformamide and water (DMF-H2O), which was designed according to the Hansen Solubility Parameter. Owing to the solvent-induced crystallization effect that led to the enhanced 3D hydrogen bonding network during the freezing-thawing process, the optimal organohydrogel achieved excellent mechanical properties with the tensile strength of 2,974 kPa and the stretchability of 277 % at room temperature, respectively. In the visiblelight range, the organohydrogel demonstrated high transmittance. Moreover, the presence of a DMF-H2O binary solvent endows it with frost-resistance, retaining the tensile strength of 508 kPa and a stretchability of 190 % even at -70 °C, respectively. This kind of transparent, frost-resistant organohydrogel has potential uses in harsh settings due to its great mechanical strength.

Nanocellulose-based membranes with pH- and temperature-responsive pore size for selective separation.

Smart gating membranes have drawn much attention due to the controllable pore structure. Herein, a smart gating membrane with dual responsiveness was prepared from bacteria cellulose (BC) grafted with pH- and temperature-responsive polymers. By external stimulation, the average pore size of the membrane can be controlled from 33.75 nm to 144.81 nm, and the pure water flux can be regulated from 342 to 2118 L·m-2·h-1 with remarkable variation in the pH range of 1-11 and temperature range of 20-60 °C. The adjustability of pore size is able to achieve the gradient selective separation of particles and polymers with different sizes. In addition, owing to the underwater superoleophobicity and the nanoscale pore structure, the membrane separation efficiencies of emulsified oils are higher than 99 %. Moreover, the controllable pore size endows the membrane with good self-cleaning performance. This nanocellulose-based smart gating membrane has potential applications in the fields of controllable permeation, selective separation, fluid transport, and drug/chemical controlled release systems.

In situ growth of Ag2S quantum dots on cellulose nanocrystals and their near-infrared bioimaging performance.

Elongated nanoparticles show distinct advantages over spherical nanoparticles in bioimaging because of surface area-to-volume, rate of clearance from the body and elimination mechanism. In this work, we investigated the fluorescence emission properties of the hybrid system by decorating silver sulfide quantum dots (Ag2S QDs) in situ on the surface of cellulose nanocrystal (CNC) with unique rod shape, modifiability and biocompatibility. This water-dispersible fluorescent probe has both absorption and fluorescence in near-infrared (NIR) region. By varying the amount of surface ligands, uniformly dispersed Ag2S QDs with different crystalline states but similar sizes were prepared due to the anchoring effect of CNC. The fluorescence quantum yield of fluorescent probes can be improved up to 109-fold (from 0.04 % to 4.36 %). In addition, the CNC-restricted interparticle spacing of Ag2S QDs (< 10 nm), in combination with the overlap of wide fluorescence emission and ultraviolet absorption, significantly enhanced the 1070 nm emission in the NIR-II region via fluorescence resonance energy transfer (FRET). Further conjugation of these CNC probes with folic acid-polyethylene glycol-amino (FA-PEG-NH2) enables in vitro bioimaging of Hela cells, which are potentially applicable for in vivo cancer detection system. The synthetic strategy provides a new way for one-pot preparation of fluorescent probes with both high NIR-I absorption and NIR-II fluorescence.

Superelastic chitin nanofibril/chitosan aerogel for effective circulating and continuous oil-water separation.

Elastic and hydrophobic aerogels have received a lot of attention in dealing with the increasing oil pollution due to their recyclable properties. Herein, we present an ultralight and superelastic aerogel with highly oriented polygon structure based on chitin nanofibril (ChNF) and chitosan (CS) by directional freezing. The chemical cross-linking enables good mechanical strength at low aerogel density. After 500 compression-release cycles, the aerogel can retain the deformation recovery rate of 88 % in air, demonstrating the excellent resilience. The bio-based aerogel has high absorption capacity (52-114 g/g) for various oils and organic solvents, and it is able to achieve the absorption retention of 90 % even after 20 absorption-extrusion cycles. Moreover, owing to the good elasticity, the pore size of the aerogel can be adjusted by compression to selectively separate water-in-oil emulsions of different particle sizes with separation efficiencies higher than 99.5 %. The bio-based aerogel with good cycle performance has broad application prospects in the field of oil-water separation.

A smart gating nanocellulose membrane showing selective separation and self-cleaning performance.

A smart gating membrane based on thermal-sensitive poly (N-isopropyl acrylamide) (PNIPAM)-grafted nanocellulose and carbon nanotube (CNT) was prepared. The presence of PNIPAM shell on cellulose nanofibrils (CNFs) endow the composite membrane with thermal responsiveness. By external stimulation, an increase temperature from 10 °C to 70 °C allows the average pore size of the membrane to be controlled from 28 nm to 110 nm, as well as the water permeance from 440 L·m-2·h-1·bar-1 to 1088 L·m-2·h-1·bar-1. The gating ratio of the membrane can reach 2.47. The photothermal effect of CNT rapidly warms up the membrane to the lowest critical solution temperature in the water, avoiding the constraint that the whole water phase cannot be heated throughout the practical use process. The membrane can precisely control the nanoparticles to concentrate at 25.3 nm, 47.7 nm or 102 nm by adjust the temperature. In addition, the water permeance can be restored to 370 L·m-2·h-1·bar-1 by washing the membrane under light. The smart gating membrane has a wide application in substance multi-stage separation and selective separation, and it can realize self-cleaning.

Classification and Prediction of Skyrmion Material Based on Machine Learning.

The discovery and study of skyrmion materials play an important role in basic frontier physics research and future information technology. The database of 196 materials, including 64 skyrmions, was established and predicted based on machine learning. A variety of intrinsic features are classified to optimize the model, and more than a dozen methods had been used to estimate the existence of skyrmion in magnetic materials, such as support vector machines, k-nearest neighbor, and ensembles of trees. It is found that magnetic materials can be more accurately divided into skyrmion and non-skyrmion classes by using the classification of electronic layer. Note that the rare earths are the key elements affecting the production of skyrmion. The accuracy and reliability of random undersampling bagged trees were 87.5% and 0.89, respectively, which have the potential to build a reliable machine learning model from small data. The existence of skyrmions in LaBaMnO is predicted by the trained model and verified by micromagnetic theory and experiments.

A Recognition Method of Truck Drivers' Braking Patterns Based on FCM-LDA2vec.

Taking truck drivers' braking patterns as the research objects, this study used a large amount of truck running data. A recognition method of truck drivers' braking patterns was proposed to determine the distribution of braking patterns during the operation of trucks. First, the segmented data of braking behaviors were collected in order to extract 25 characteristic parameters. Additionally, seven main correlation factors were obtained by dimensionality reduction. The FCM clustering algorithm and CH scores were used to identify nine categories of truck drivers' braking behaviors. Then the LDA2vec model was used to identify the distribution of different braking behavior words in braking patterns, and three categories of truck drivers' braking patterns were identified. The test results showed that the accuracy of the truck drivers' braking pattern recognition model based on LDA2vec was higher than 85%, and braking patterns of drivers in the daily operation process could be mined from vehicle operation data. Furthermore, through the monitoring and pre-warning of the braking patterns and targeted training of drivers, traffic accidents could be avoided. At the same time, this paper's results can be used to protect human life and health and reduce environmental pollution caused by traffic congestion or traffic accidents.

SERS-active nanocellulose substrate via in-situ photochemical synthesis.

Surface-enhanced Raman scattering spectroscopy (SERS) is a highly-sensitive technology to detect trace target analytes. Herein, a series of flexible SERS substrate for the detection of malachite green (MG) bactericide were developed via in situ photochemical synthesis of silver nanoparticles (AgNPs) based on two dimentional (2D) nanocellulose film without additional reducing agent. For the first time, silver nanocubes (AgNCs) with sharp edges and corners, which are conductive to the formation of hot spots, were successfully prepared and uniformly loaded on the nanocellulose film by controlling the reaction conditions. The obtained composite SERS substrate showed high sensitivity to Rhodamine 6G (R6G) and MG with limit of detection (LOD) of 4.7 × 10-12 and 1.2 × 10-8 g/L, respectively. In addition, the relative standard deviation (RSD) was calculated lower than 15 %, demonstrating the good detection reproducibility. The nanocellulose-based 2D SERS substrate shows the potential as a detection platform in the rapid and sensitive identification of various toxic and harmful pollutants.

Multifunctional cellulose paper-based materials and their application in complex wastewater treatment.

The rapid and efficient treatment of complex wastewater remains challenging. Herein, green paper-based materials with high wet strength, good oil-water separation property and high heavy metal ion adsorption capacity were prepared via a facile, cost-effective process. The introduction of amphoteric functional groups not only met the requirements for heavy metal ion adsorption, but also maintained the stable underwater superoleophobic properties of materials a wide pH range. The covalent crosslinking between cellulose fibers induced by polyethyleneimine and citric acid significantly improved the wet strength (up to 26.0 Nm/g) and the porosity. The membrane flux was increased up to 3515 L/(m2·h) and the separation efficiencies were higher than 98%. Moreover, the theoretical maximum adsorption capacities for Cd(II) and Pb(II) reached 73.29 and 93.75 mg/g, respectively. Combined with filtration technology, the materials can realize the continuous and efficient purification of complex wastewater.

Flexible 2D nanocellulose-based SERS substrate for pesticide residue detection.

Nanocellulose holds considerable promise as an effective surface-enhanced Raman scattering (SERS) substrate for sensitive detection of trace targets. Flexible and high-sensitivity two-dimensional (2D) SERS substrates based on nanocrystalline cellulose (CNC) film were successfully developed via self assembly of two plasma nanoparticles: gold nanoflowers (AuNFs) and silver-coated gold nanocubes (Au@AgNCs). The loading process allows the precise control of nanoparticle distribution density and uniformity on CNC film, which are closely related to the plasma coupling effect between particles. The obtained CNC/Au@AgNC flexible two-dimensional substrate could sensitively detect pesticide residues on apple surface, and the detection limits (LOD) of dimethoate and acetamiprid were 4.1 and 10.7 µg/L, respectively. In addition, Raman signal intensity showed a good linear relationship with pesticide concentration in the range of 10-100 µg/L, which provided great potential for high sensitivity and field detection of dangerous targets.

Charge transport and extraction of PTB7:PC71BM organic solar cells: effect of film thickness and thermal-annealing.

Charge carrier transport in the active layer and charge extraction at the electrode have significant impact on the performance of solar cells. In this study, the effect of active layer thickness and thermal-annealing treatment on the charge transport and extraction performance of PTB7:PC71BM organic solar cells was studied comprehensively. Thin films of active layer couldn't utilize enough sunlight, while thick films could bring about large bulk resistance and deteriorate carrier transport. There is a trade-off between active layer thickness and carrier transport. The optimized active layer thickness is about 100 nm for the PTB7:PC71BM bulk heterojunction organic solar cells. Thermal-annealing could improve the morphology of the active layer, and facilitate charge transport in the active layer and charge collection at the electrode. The improved carrier transport and extraction were verified by the transient photocurrent/transient photovoltage and photo-induced charge carrier extraction by linearly increasing voltage measurements. The optimal power conversion efficiency was obtained as 8.28% for the device with an active layer thickness of 100 nm and treated with 90 °C thermal-annealing.