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ZnO-based catalysts have been intensively studied because of their extraordinary performance in lower olefin synthesis, methanol synthesis and water–gas shift reactions. However, how ZnO catalyzes these reactions are still not well understood. Herein, we investigate the activations of CO2, O2 and CO on single crystalline ZnO polar surfaces at room temperature, through in-situ near-ambient-pressure X-ray photoelectron spectroscopy (NAP-XPS). It is revealed that O2 and CO2 can undergo chemisorption on ZnO polar surfaces at elevated pressures. On the ZnO ( 0001 ) surface, molecular CO2 (O2) can chemically interact with the top layer Zn atoms, leading to the formation of C O 2 δ - ( O 2 δ - ) or partially dissociative atomic oxygen ( O - ) and hence the electron depletion layer in ZnO. Therefore, an apparent upward band-bending in ZnO ( 0001 ) is observed under the CO2 and O2 exposure. On the ZnO ( 000 1 ¯ ) surface, the molecular chemisorbed CO2 (O2) mainly bond to the surface oxygen vacancies, which also results in an upward band-bending in ZnO ( 000 1 ¯ ). In contrast, no band-bending is observed for both ZnO polar surfaces upon CO exposure. The electron-acceptor nature of the surface bounded molecules/atoms is responsible for the reversible binding energy shift of Zn 2p3/2 and O 1s in ZnO. Our findings can shed light on the fundamental understandings of CO2 and O2 activation on ZnO surfaces, especially the role of ZnO in heterogeneous catalytic reactions.

Polyethylene oxide (PEO)-based electrolytes have obvious merits such as strong ability to dissolve salts (e.g., LiTFSI) and high flexibility, but their applications in solid-state batteries is hindered by the low ion conductance and poor mechanical and thermal properties. Herein, poly(m-phenylene isophthalamide) (PMIA) is employed as a multifunctional additive to improve the overall properties of the PEO-based electrolytes. The hydrogen-bond interactions between PMIA and PEO/TFSI− can effectively prevent the PEO crystallization and meanwhile facilitate the LiTFSI dissociation, and thus greatly improve the ionic conductivity (two times that of the pristine electrolyte at room temperature). With the incorporation of the high-strength PMIA with tough amide-benzene backbones, the PMIA/PEO-LiTFSI composite polymer electrolyte (CPE) membranes also show much higher mechanical strength (2.96 MPa), thermostability (419 °C) and interfacial stability against Li dendrites (468 h at 0.10 mA cm‒2) than the pristine electrolyte (0.32 MPa, 364 °C and short circuit after 246 h). Furthermore, the CPE-based LiFePO4/Li cells exhibit superior cycling stability (137 mAh g−1 with 93% retention after 100 cycles at 0.5 C) and rate performance (123 mAh g−1 at 1.0 C). This work provides a novel and effective CPE structure design strategy to achieve comprehensively-upgraded electrolytes for promising solid-state battery applications.

The rapid development of additive manufacturing techniques in the field of tissue regeneration offers unprecedented success for artificial tissue and organ fabrication. However, some limitations still remain for current bioinks, such as the compromised cell viability after printing, the low cross-linking efficiency leading to poor printing resolution and speed due to the relatively slow gelation rate, and the requirement of external stimuli for gelation. To address these problems, herein, a biocompatible and printable instant gelation hydrogel system has been developed based on a designed hyperbranched poly(ethylene glycol) (PEG)-based multihydrazide macro-cross-linker (HB-PEG-HDZ) and an aldehyde-functionalized hyaluronic acid (HA-CHO). HB-PEG-HDZ is prepared by the postfunctionalization of hyperbranched PEG-based multivinyl macromer via thiol-ene chemistry. Owing to the high functional group density of HB-PEG-HDZ, the hydrogel can be formed instantly upon mixing the solutions of two components. The reversible cross-linking mechanism between the hydrazide and aldehyde groups endows the hydrogel with shear-thinning and self-healing properties. The minimally toxic components and cross-linking chemistry allow the resulting hydrogel to be a biocompatible niche. Moreover, the fast sol-to-gel transition of the hydrogel, combining all of the advanced characteristics of this platform, protects the cells during the printing procedure, avoids their damage during extrusion, and improves the transplanted cell survival.

Cellobiose is usually preferred as model compound of cellulose to explore its conversion mechanism, in which the first challenge is to acquire the molecular solvation mechanism. The interactions of β-cellobiose with the hydrated Na+ cation and Cl− anion in aqueous solution have been theoretically investigated, using quantum chemical calculations at LC-ωPBE/6-311++G(d,p), aug-cc-pVTZ level under a polarized continuum model (PCM-SMD), together with molecular dynamics stimulation. In aqueous solution, the most stable form of β-cellobiose is syn-ϕ/syn-φ (CB2), including the exocylcic hydroxyl groups and three intramolecular H-bonds. The favorite solvation structure of NaCl is concerned with [Na(H2O)3]+···Cl− ion pair. The Cl− anion interacts with β-cellobiose, favorably affording $$[\eta_{{\text{H}}6,{\text{H}}2^{\prime}}^2{-}{\text{CB}}2){\text{Cl}}{]^- }$$ and $$[\eta_{{\text{H}}3^{\prime},{\text{H}}4^{\prime}}^2{-}{\text{CB}}2){\text{Cl}}{]^- }$$ with a bridge of OH···Cl···HO interaction. Alternatively, the [Na(H2O)3]+ cation interacts with β-cellobiose, preferably yielding $$[\eta_{{\text{O}}3,{\text{O}}5^{\prime},{\text{O}}6^{\prime}}^3{-}{\text{CB}}2){\text{Na}}{]^+ }$$ . Additionally, the [Na(H2O)3]+···Cl− ion-pair interacts cooperatively with β-cellobiose, preferentially producing $$[\eta_{{\text{O}}3,{\text{O}}5^{\prime},{\text{O}}6^{\prime},{\text{H}}6,{\text{H}}2^{\prime}}^3{-}{\text{CB}}2){\text{Na}}{\left( {{{\text{H}}_2}{\text{O}}} \right)_1}]{\text{Cl}}$$ . For CB2, the reactive sites for the nucleophilic and electrophilic reactions locate at the O5 atom on the reducing end and the H6′ atom on the non-reducing end, respectively. Alternatively, for $$[\eta_{{\text{O}}3,{\text{O}}5^{\prime},{\text{O}}6^{\prime},{\text{H}}6,{\text{H}}2^{\prime}}^3{-}{\text{CB}}2){\text{Na}}{\left( {{{\text{H}}_2}{\text{O}}} \right)_1}]{\text{Cl}}$$ , the O5 and H6′ atoms should no longer be characteristic of nucleophilicity and electrophilicity. Moreover, [Na(H2O)3]+···Cl− ion-pair can break some intramolecular H-bonds of CB2, which may promote the solvation of β-cellobiose in aqueous solution. It also shields the glycosidic bond by steric effect, which make CB2 not readily hydrated at the glycosidic bond. These functions would alter the reaction pathway in the further degradation of β-cellobiose. This study may advance on the novel design for sustainable conversion system of cellulose into high-added value chemicals.

The practical application of solid polymer electrolytes in high-energy Li metal batteries is hindered by Li dendrites, electrochemical instability and insufficient ion conductance. To address these issues, flexible composite polymer electrolyte (CPE) membranes with three dimensional (3D) aramid nanofiber (ANF) frameworks are facilely fabricated by filling polyethylene oxide (PEO)-lithium bis(trifluoromethylsulphonyl)imide (LiTFSI) electrolyte into 3D ANF scaffolds. Because of the unique composite structure design and the continuous ion conduction at the 3D ANF framework/PEO-LiTFSI interfaces, the CPE membranes show higher mechanical strength (10.0 MPa), thermostability, electrochemical stability (4.6 V at 60°C) and ionic conductivity than the pristine PEO-LiTFSI electrolyte. Thus, the CPEs display greatly improved interfacial stability against Li dendrites (≥1000 h at 30°C under 0.10 mA cm−2 ), compared with the pristine electrolyte (short circuit in 13 h). The CPE-based all-solid-state LiFePO4/Li cells also exhibit superior cycling performance (e.g., 130 mA h g−1 with 93% retention after 100 cycles at 0.4 C) than the ANF-free cells (e.g., 82 mA h g−1 with 66% retention). This work offers a simple and effective way to achieve high-performance composite electrolyte membranes with 3D nanofiller framework for promising solid-state Li metal battery applications.

Auxetic architectures with a negative Poisson's ratio have attracted increasing attention due to their intriguing physical properties and numerous promising applications and recent advancements in manufacturing techniques. However, fabrication of three-dimensional (3D) polymeric auxetic architectures with a tailored hierarchically porous structure and desired physical/mechanical properties remains challenging. Herein, 3D nanofibrous Kevlar aerogel architectures with porosity at multiple scales have been designed and fabricated through a new additive manufacturing strategy, i.e., integration of direct ink writing and freeze-casting with non-toxic solvent-based inks followed by special drying techniques. The highly porous 3D nanofibrous Kevlar aerogel architectures achieve excellent mechanical properties with an ultralow density (down to 11.9 mg cm−3) and large specific surface area (up to 350 m2 g−1). The Poisson's ratio is tunable in a wide range, spanning from −0.8 to 0.4, by adjusting the spatial arrangement of the designed pattern struts. Finally, these nanofibrous Kevlar aerogel architectures have been further functionalized into hydrophobic, luminescent and thermoresponsive architectures by using fluorocarbon resin, functional dyes and organic phase-change materials respectively. The multi-functional auxetic aerogel architectures demonstrate potential for a broad range of applications.

In addition to conventional linear, branched, crosslinked and dendritic polymers, single chain cyclized/knotted polymers (SCKPs) have emerged as a new class of polymer structure showing unique properties. Here, we report the development of bacterial resistant SCKPs and investigate how the single chain cyclized/knotted structure affects the performance of polymer materials in bacterial resistance. Four SCKPs were synthesized by reversible addition fragmentation chain transfer (RAFT) homopolymerization of multivinyl monomers (MVMs) and then crosslinked by ultraviolet (UV) light to form SCKP films. Regardless of MVM types, the four SCKP films always showed much higher bacterial resistance ability, and up to 75% of bacterial attachment and biofilm formation were reduced in comparison with the corresponding non‐SCKP films which are directly made from the polymerization of MVMs. These results highlight the critical role of the single chain cyclized/knotted structure in enhancing the bacterial resistance of polymeric materials. Further mechanistic studies revealed that the surface morphology and altered hydrophobicity induced by the single chain cyclized/knotted structure could account for the enhanced bacterial resistant performance of the SCKP films.

Cu(0)-mediated reversible deactivation radical polymerization (Cu(0)-mediated RDRP) has been demonstrated as an excellent technique to control the polymerization of multiple vinyl monomers (e.g., acrylates, methacrylates, and styrene). However, the complexity of the reaction mechanism and multi-component system nature make it challenging to choose the appropriate conditions and consider the factors of achieving controllable polymerization when switching from one monomer to others with different reactivities. Herein, by polymerizing two examplary monomers: methyl methacrylate (MMA) and styrene via Cu(0)-mediated RDRP under different conditions, we have found that the reaction parameters (e.g., initiator, ligand, solvent, and deactivator) play a crucial role in regulating two equilibriums: (i) mutual conversion of different copper species which determines the relative concentration of Cu(I) and Cu(II), and (ii) polymerization equilibrium which is the combination of activation/deactivation, propagation and termination processes. We have demonstrated that by taking both the mutual conversion of different copper species and the polymerization equilibrium into account, the optimal reaction conditions could be selected, and the well-controlled Cu(0)-mediated RDRPs of methyl methacrylate and styrene were achieved with narrow molecular weight distributions and predicted molecular weight.

It is still not clear at the molecular level how the acidic silanol and basic alkylamine bifunctional groups over SBA-15 zeolite exert catalytic functions in aldol condensation of 5-hydroxymethylfu...

Phase change materials offer enormous potential for thermal energy storage due to their high latent heat and chemical stability. Researchers have developed numerous innovative strategies to overcome the leakage of organic phase change materials and enhance thermal performance. However, the manufacture of form-stable, free-standing energy storage films based on phase change materials with high latent heat remains difficult. Therefore, the present study focused on the production of free-standing, form-stable energy storage films with high phase-change enthalpy and thermally stimulant multiresponsiveness from the simple composite of paraffin with a polytetrafluoroethylene/silica (PTFE/SiO

Mo-Containing catalysts exhibit good catalytic performance toward the selective oxidation of platform chemicals from biomass. However, for the aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF), the development of an environmentally-friendly and promising catalytic system remains a significant challenge to date. In the present study, on the pore surface of MCM-41, two kinds of active sites, which are, –(SiO)2Mo(O)2 ([Mo-4]) and –(SiO)3Mo(OH)(O) ([Mo-5]), have been theoretically designed, over which the catalytic mechanisms for the aerobic oxidation of HMF to DFF have been theoretically examined, combining the hybrid quantum mechanics and molecular mechanics calculations. Over both [Mo-4] and [Mo-5] active sites, the oxidative reaction includes two main reaction steps, the O–H and C–H bond cleavages of HMF, in which the crucial reaction step is associated with the C–H bond cleavage of the CH2 group of the first HMF. Over the –(O)4–MoO active site on the Keggin heteropolyacid ([Mo-HPA]), [Mo-4] and [Mo-5] active sites, the MoO group is responsible for the O–H bond activation in the HMF moiety, and the Mo–OH group is in charge of the C–H bond activation in the HMF moiety, both of which take a synergic catalytic effect. The catalytic activity decreases as [Mo-5] > [Mo-4] > [Mo-HPA]. Based on the activation strain analysis, the lowering activation energy stems mainly from the lowering activation strain of the active site, which correlates positively with the corresponding HOMO–LUMO gap. These findings provide deep insight for the rational design of a recyclable catalyst to activate both C–H and O–H bonds at low temperatures, especially for some typical platform molecules from biomass.

Lightweight, robust, and thin aerogel films with multifunctionality are highly desirable to meet the technological demands of current society. However, fabrication and application of these multifunctional aerogel films are still significantly underdeveloped. Herein, we demonstrate a multifunctional aerogel film composed of strong aramid nanofibers (ANFs), conductive carbon nanotubes (CNTs), and hydrophobic fluorocarbon (FC) resin. The obtained hybrid aerogel film exhibits large specific surface area (232.8 m2·g-1), high electrical conductivity (230 S·m-1), and excellent hydrophobicity (contact angle of up to 137.0°) with exceptional Joule heating performance and supreme electromagnetic interference (EMI) shielding efficiency. The FC coating renders the hydrophilic ANF/CNT aerogel films hydrophobic, resulting in an excellent self-cleaning performance. The high electrical conductivity enables a low-voltage-driven Joule heating property and an EMI shielding effectiveness (SE) of 54.4 dB in the X-band at a thickness of 568 μm. The specific EMI SE is up to 33528.3 dB·cm2·g-1, which is among the highest values of typical metal-, conducting-polymer-, or carbon-based composites. This multifunctional aerogel film holds great promise for smart garments, electromagnetic wave shielding, and personal thermal management systems.

It is well known that free radical (co)polymerization of multivinyl monomers (MVMs) leads to insoluble gels even at a low monomer conversion, and the gelation point can be predicted by Flory–Stockmayer theory (F–S theory) based on two assumptions: (1) equal reactivity of all vinyl groups and (2) the absence of intramolecular cyclization. This theory has been experimentally studied and verified with conventional free radical (co)polymerization (FRP) of several MVMs (e.g., divinylbenzene, DVB). However, it is still debatable whether this theory is applicable for the polymerization of MVMs using reversible deactivation radical polymerization (RDRP) approaches, such as atom transfer radical polymerization (ATRP). Herein, Monte Carlo simulations using two statistical models—with cyclization (w.c.) and without cyclization (wo.c., corresponding to F–S theory)—and dynamic lattice liquid (DLL) models were conducted to study ATRP of divinyl monomers. The simulated gel points using w.c. and wo.c. models were compare...

Multifunctional hyperbranched poly(poly(ethylene glycol) diacrylate) (HB-PEGDA) polymers with well-defined composition, structure, and functionality are proposed in this work as photonic hydrogel scaffolds. By taking advantage of its unique transparency, low intrinsic viscosity, and high amount of vinyl groups, the HB-PEGDA can effectively penetrate inside the colloidal photonic crystal (CPC) substrate and be cross-linked with thiolated hyaluronic acid very quickly. This photonic hydrogel shows not only an unexpected protective effect to the untreated CPC substrate, but also nonswelling characteristics attributed to its relatively compacted network structure, which leads to robust structural integrity and credible, consistent optical performance under complex physiological conditions. Moreover, this photonic hydrogel shows good biocompatibility and can be easily modified to introduce specific functions (e.g., cell attachment), providing novel insights into the photonic hydrogel design toward diverse bio-o...

Porous copper (Cu) films were facilely and greenly fabricated by low-current electrical field-induced assembly of ~ 3 nm Cu nanoparticles (NPs) in several minutes using generated hydrogen bubbles as dynamic negative templates. The porous films had open three-dimensionally (3D) interconnected nanopores and uniform pore size distribution and exhibited a hierarchical structure composed of supraparticles that were further composed of the Cu NPs. Lattice-to-lattice connectivity in the self-assembly of the NPs in the 3D structures enables fast charge transport. The structure/morphology of the porous Cu materials can be tuned by adjusting the concentration of the additives, applied potential/current densities and assembly time. A growth mechanism of the porous films was reasonably proposed for the field-induced assembly of the Cu NPs. The porous Cu film-supported Si electrode showed high capacity of 1173 mAh g−1 and retention rate of 87% after 10 cycles at 1 C. Our research sheds a light on preparing 3D nanoporous structures especially for suitable electrodes in electrochemical energy storage devices.

Bulk graphene aerogels with high electrical conductivity, ultralow density, and high specific surface area have attracted significant attention because of their fascinating performances in energy storage, catalysis, absorption, sensor, electromagnetic shielding, etc. However, graphene aerogel microgranules (i.e., reducing the size of the bulk aerogels into microscale) and their performances in the electromagnetic field have been ignored. Herein, we report a new strategy to make floatable graphene aerogel microgranules with high hydrophobicity (137°), low density (13.5 mg/cm3), and high specific surface area (516 m2/g). These microgranules were synthesized initially from reduced graphene oxide (rGO) hydrogel microparticles and then in situ-modified by silica nanoparticles. Further investigations have demonstrated that the resulting silica-modified rGO aerogel microgranules possess highly efficient static electromagnetic screening (average 30.3 dB in 8–18 GHz) and dynamic infrared shielding (higher than 10 ...

The practical implementation of nanomaterials in high capacity batteries has been hindered by the large mechanical stresses during ion insertion/extraction processes that lead to the loss of physical integrity of the active layers. The challenge of combining the high ion storage capacity with resilience to deformations and efficient charge transport is common for nearly all battery technologies. Layer-by-layer (LBL/LbL) engineered nanocomposites are able to mitigate structural design challenges for materials requiring the combination of contrarian properties. Herein, we show that materials engineering capabilities of LBL augmented by self-organization of nanoparticles (NPs) can be exploited for constructing multiscale composites for high capacity lithium ion anodes that mitigate the contrarian nature of three central parameters most relevant for advanced batteries: large intercalation capacity, high conductance, and robust mechanics. The LBL multilayers were made from three function-determining components...

Carbon catalyst is regarded as an efficient and environment-friendly material for the direct oxidation of benzene to phenol. However, the essence and detailed performances of the active sites are still unclear at the molecular level. In the present study, the role of typical defect sites on carbon for benzene hydroxylation to phenol with hydrogen peroxide as the oxidant was theoretically investigated at M06-2x/6-311++G(d, p) level in acetonitrile solution. The carbon with defect sites was modeled with armchair and zigzag edges. The turnover frequency analysis indicated that the rate-controlling step was associated with the HO–OH bond cleavage in the H2O2 moiety for the formation of hydroxyl radical. For both the armchair and zigzag edges on carbon material, the defect site plays an essential role in the hydroxyl radical formation from H2O2. In the presence of water, the defect site of carbon could readily be hydrated, where the zigzag defect site could be more easily hydrated to hydroquinone than the defect armchair site. Furthermore, the zigzag defect carbon exhibits better catalytic performance than the armchair defect carbon. Based on activation strain analysis, there is a stronger stabilizing transition state interaction in the zigzag defect carbon than that in the defect armchair carbon, which arises from a narrower HOMO–LUMO gap. The present study could shed some light on the essence and function of active sites on carbon for the benzene hydroxylation to phenol.

The conventional free radical polymerization (FRP) of multivinyl monomers (MVMs) inevitably leads to gelation even at low monomer conversion resulting in difficulties to control and monitor the reaction process. Flory and Stockmayer (F-S theory) studied it based on two fundamental assumptions: (1) independent and equivalent vinyl groups; (2) no intramolecular cyclization. However, until now its applicability to FRP of MVMs (especially regarding the extent of intramolecular cyclization) is still controversial. In this paper, Monte Carlo simulations are used to study FRP of divinyl monomers by two kinetic models: with/without cyclization models. The results of the simulations are compared with the calculated gel points based on F-S theory and the experimental data. It is found that the intramolecular cyclization has a negligible impact on the polymerization process and the gel point before gelation, which are in agreement with the prediction by F-S theory, but the effect becomes significant above the gel points.

Using a combined synthesis approach comprising reversible addition-fragmentation transfer polymerization and ring opening reaction, a series of poly glycidyl methacrylate (polyGMA) polymers were designed and synthesized for gene delivery. These polymers characterized by low cationic charge respective to established gene delivery vectors such as PEI were studied to further elucidate the key structure-activity parameters that mediate efficient and biocompatible gene delivery. Compared to PEI, these brushlike polymers facilitated markedly improved safety and gene delivery efficiency.

This paper presents a "turn-on" fluorescence biosensor based on graphene quantum dots (GQDs) and molybdenum disulfide (MoS2) nanosheets for rapid and sensitive detection of epithelial cell adhesion molecule (EpCAM). PEGylated GQDs were used as donor molecules, which could not only largely increase emission intensity but also prevent non-specific adsorption of PEGylated GQD on MoS2 surface. The sensing platform was realized by adsorption of PEGylated GQD labelled EpCAM aptamer onto MoS2 surface via van der Waals force. The fluorescence signal of GQD was then quenched by MoS2 nanosheets via fluorescence resonance energy transfer (FRET) mechanism. In the presence of EpCAM protein, the stronger specific affinity interaction between aptamer and EpCAM protein could detach GQD labelled EpCAM aptamer from MoS2 nanosheets, leading to the restoration of fluorescence intensity. By monitoring the change of fluorescence signal, the target EpCAM protein could be detected sensitively and selectively with a linear detection range from 3nM to 54nM and limit of detection (LOD) around 450pM. In addition, this nanobiosensor has been successfully used for EpCAM-expressed breast cancer MCF-7 cell detection.

The product inspection process with measurement uncertainty as a quality indicator is researched. Based on the product quality control information and the design and processing precision, the relationship between the misjudgement probability and measurement uncertainty of conformance testing is established. In view of the limitation of uncertainty evaluation based on the single piece in product inspection, the method for evaluating uncertainty fusing multiple product measurement information in a fully integrated batch is proposed. The uncertainty components caused by the measurement repeatability and reproducibility of the whole test work are evaluated based on the conjugate Bayesian estimation method. The test results show that there is a certain false positive rate in the whole test of the product under the condition of uncertainty. Research results show that the misjudgement probability caused by the measurement uncertainty cannot be ignored. In the product test, batch detection information should be fully integrated to improve the representation of uncertainty evaluation results.

Aerogel with low density, high porosity, and large surface area is a promising structure for the next generation of high-performance thermal insulation fibers and textiles. However, aerogel fibers suffer from weak mechanical properties or complex fabricating processes. Herein, a facile wet-spinning approach for fabricating nanofibrous Kevlar (KNF) aerogel threads ( i.e., aerogel fibers) with high thermal insulation under extreme environments is demonstrated. The aerogel fibers made from nanofibrous Kevlar render a high specific surface area (240 m2/g) and wide-temperature thermal stability. The flexible and strong KNF aerogel fibers are woven into textiles to illustrate the excellent thermal insulation property under extreme temperature (-196 or +300 °C) and at room temperature. COMSOL simulation is applied to calculate the thermal conductivity of a single aerogel fiber and find an effective way to improve the thermal insulation property of the aerogel fiber. Furthermore, a series of functionalized fibers or textiles based on KNF aerogel fibers, such as phase-change fibers, conductive fibers, and hydrophobic textiles, have been prepared. Such KNF aerogel fibers represent a promising direction for the next generation of high-performance fibrous thermal-insulation materials.

The selective removal of oxygen from 5-hydroxymethylfurfural (HMF) is challenging for the effective utilization of biomass. The catalytic mechanisms of palladium acetate toward the conversion of HMF to furfuryl alcohol (FFA), 5-methylfurfural (5-MF) and 2,5-dihydroxymethyl furan (DHMF) have been theoretically investigated. The decarbonylation of HMF to FFA includes (i) migratory extrusion, (ii) metal-acetate-co-assisted deprotonation, (iii) decarbonylation, (iv) metal-assisted deprotonation, and (v) migratory extrusion and catalyst regeneration. Both hydrogenation and deoxidation of HMF with HCOOH as the H-source involve (i) migratory extrusion, (ii) oxidative addition, (iii) reductive elimination, (iv) metal-assisted deprotonation, and (v) migratory extrusion and catalyst regeneration. The C–H bond cleavage is the crucial reaction step, in which the metal-acetate-co-assisted deprotonation is kinetically more preferable than the oxidative addition. Both FFA and DHMF are kinetically superior to 5-MF. In terms of selectivity, increasing the temperature is beneficial to decarbonylation and decreasing the temperature is advantageous to hydrogenation. The present finding provides molecular-level insight into the functions of both the metal-center and coordinated-ligand in the Pd(OAc)2 catalyst, which may drive the novel design of catalytic systems toward both decarbonylation and hydrogenation reactions.

Infrared (IR) stealth is essential not only in high technology and modern military but also in fundamental material science. However, effectively hiding targets and rendering them invisible to thermal infrared detectors have been great challenges in past decades. Herein, flexible, foldable, and robust Kevlar nanofiber aerogel (KNA) films with high porosity and specific surface area were fabricated first. The KNA films display excellent thermal insulation performance and can be employed to incorporate with phase-change materials (PCMs), such as polyethylene glycol, to fabricate KNA/PCM composite films. The KNA/PCM films with high thermal management capability and infrared emissivity comparable to that of various backgrounds demonstrate high performance in IR stealth in outdoor environments with solar illumination variations. To further realize hiding hot targets from IR detection, combined structures constituted of thermal insulation layers (KNA films) and ultralow IR transmittance layers (KNA/PCM) are proposed. A hot target covered with this combined structure becomes completely invisible in infrared images. Such KNA/PCM films and KNA-KNA/PCM combined structures hold great promise for broad applications in infrared thermal stealth.

Rapidly evolving fields of biomedical, energy, and (opto)electronic devices bring forward the need for deformable conductors with constantly rising benchmarks for mechanical properties and electronic conductivity. The search for conductors with improved strength and strain have inspired the multiple studies of nanocomposites and amorphous metals. However, finding conductors that defy the boundaries of classical materials and exhibit simultaneously high strength, toughness, and fast charge transport while enabling their scalable production, remains a difficult materials engineering challenge. Here, composites made from aramid nanofibers (ANFs) and gold nanoparticles (Au NPs) that offer a new toolset for engineering high strength flexible conductors are described. ANFs are derived from Kevlar macrofibers and retain their strong mechanical properties and temperature resilience. Au NPs are infiltrated into a porous, free-standing aramid matrix, becoming aligned on ANFs, which reduces the charge percolation threshold and facilitates charge transport. Further thermal annealing at 300 °C results in the Au-ANF composites with an electrical conductivity of 1.25 × 104 S cm−1 combined with a tensile strength of 96 MPa, a Young's modulus of 5.29 GPa, and a toughness of 1.3 MJ m−3. These parameters exceed those of most of the composite materials, and are comparable to those of amorphous metals but have no volume limitations. The plasmonic optical frequencies characteristic for constituent NPs are present in the composites with ANFs enabling plasmon-based optoelectronic applications.

Polymer matrices with excellent mechanical properties, thermal stability and other features are highly demanded for the effective utilization within nanocomposites. Here, we fabricate free-standing aramid nanofiber films via spin coating of an aramid nanofiber/dimethyl sulfoxide solution. Compared with traditional film fabrication methods, this process is time-saving and also able to easily tune the thickness of the films. The resultant films show greatly improved stretchability than that of Kevlar threads and relatively high mechanical strength. Typically, these films with a thickness of 5.5 µm show an ultimate strength of 182 MPa with an ultimate tensile strain of 10.5%. We also apply a finite element modeling to simulate the strain and strength distributions of the films under uniaxial tension, and the results of the simulation are in accordance with the experimental data. Furthermore, the aramid nanofiber films exhibit outstanding thermostability (decomposition at ~ 550 °C under N2 atmosphere and ~ 500 °C in air) and chemical inertness, which would endure acid and alkali. The simple method demonstrated here provides an important way to prepare high-performance aramid nanofiber films for designing new composite systems.

Tin (Sn) has long been considered to be a promising replacement anode material for graphite in next-generation lithium-ion batteries (LIBs), because of its attractive comprehensive advantages of high gravimetric/volumetric capacities, environmental benignity, low cost, high safety, etc. However, Sn-based anodes suffer from severe capacity fading resulting mainly from their large volume expansions/contractions during lithiation/delithiation and subsequent pulverization, coalescence, delamination from current collectors, and poor Li+/electron transport. To circumvent these issues, a number of extraordinary architectures from nanostructures to anchored, layered/sandwich, core-shell, porous and even integrated structures have been exquisitely constructed to enhance the cycling performance. To cater for the rapid development of Sn-based anodes, we summarize the advances made in structural design principles, fabrication methods, morphological features and battery performance with focus on material structures. In addition, we identify the associated challenges and problems presented by recently-developed anodes and offer suggestions and perspectives for facilitating their practical implementations in next-generation LIBs.

Conventional biochemical methods for foodborne pathogen detection are time-consuming, labor-intensive and can only be used for single type bacteria detection with one sample. There is always an urgent need for fast, accurate and easy to handle devices for identification and monitoring of multiple foodborne pathogens at the same time. Herein, we present a non-biofouling polyethylene glycol (PEG) based microfluidic chip integrated with functionalized nanoporous alumina membrane for simultaneous electrochemical detection of two types of bacteria Escherichia coli O157:H7 and Staphylococcus aureus from the mixed samples. The experimental results demonstrated the specificity for target bacteria detection and the low cross-binding of non-target bacteria. The simultaneous detection of mixed bacteria sample of E. coli O157:H7 and S. aureus was also demonstrated. This sensor has a linear detection range from 102 CFU/mL to 105 CFU/mL with the limit of detection (LOD) around 102 CFU/mL.

Using lanthanum-doped graphene as nanofiller and poly(methyl methacrylate) as matrix, the electromagnetic shielding effectiveness and thermal stability of La-graphene/poly(methyl methacrylate) composites were studied. The temperature of maximum pyrolysis rate and electromagnetic shielding effectiveness of specimens obviously increased under low nanofiller loadings, whose peak value of shielding effectiveness is ca. 29 dB over the frequency range of 8.2–12.4 GHz.

Satisfactory ionic conductivity and mechanical stability are the prerequisites for the applications of solid polymer electrolytes in Li-ion batteries. Herein, by using aramid nanofibers (ANFs) as multifunctional nano-additives, comprehensively-upgraded polyethylene oxide (PEO)-LiTFSI electrolytes with 3D ANF network frames are achieved through the hydrogen-bond interactions between the 1D ANFs. The hydrogen-bond interactions between the ANFs and the PEO chains and TFSI‒ anions can greatly prevent the ANF agglomeration, suppress the PEO crystallization, facilitate the LiTFSI dissociation, and prolong the ion transport paths at the 3D ANF framework/PEO-LiTFSI interfaces. Thus, the ANF-modified electrolytes show superior room-temperature conductivity of 8.8 × 10−5 S cm−1. The ANF-containing composite electrolytes also display greatly-enhanced mechanical strength, thermostability, electrochemical stability and interfacial resistance against Li dendrites, attributed to the 3D ANF framework. In consequence, the composite electrolyte-based LiFePO4/Li cells exhibit better rate performance and cycling stability (e.g., 135 mAh g−1 after 100 cycles at 0.4 C). This work offers a novel and effective strategy to comprehensively upgrade polymer electrolytes by employing organic nanofillers in the composite electrolyte design and revealing the ion transport mechanism for promising all-solid-state Li-ion battery applications.

It is unclear at the molecular level why HY (HY = RSH, or ROH, or RNH2) with HPPh2 additives kinetically affects the reaction pathway to the formation of different monomers (Ph2P-SeCd-Y or Ph2P-SeCdSe-Y) in the systhesis of semiconductor nanocrystals. In the present work, it was found that in a [Cd(OA)2 + Se[double bond, length as m-dash]P(C8H17)3 + HPPh2 + HY] mixture, HY behaves as a mediator for the formation of the initial kind of monomer, besides as a hydrogen/proton donor in the release of oleic acid and as an accelerant in the Se-P bond cleavage, which follows the mechanism of hydrogen-shift/nucleophilic-attack. The capability of the HY additive to provide a H-source decreases in the order SePPh2H > RSH > HPPh2 > ROH > RNH2, while the performance of HY to accelerate Se-P bond cleavage decreases in the order HPPh2 > RSH > RNH2 > ROH. The capacity of HY to promote the formation of the Ph2P-SeCd-Y monomer decreases in the order RSH > HPPh2 > ROH > RNH2, while the effect of HY to drive the formation of the Ph2P-SeCdSe-Y monomer decreases in the order HPPh2 > RSH > RNH2 > ROH. The activation strain energy plays a key role in both the Se-P and H-Y bond cleavage, which correlates negatively to the size of the coordinated atom radius. When only HPPh2 is present without other HY species (HY = RNH2, or RSH, or ROH), Ph2P-SeCdSe-PPh2 is preferentially formed. Alternatively, when both HY (HY = RNH2, or RSH, or ROH) and HPPh2 are present, Ph2P-SeCd-Y is favorably formed. For the formation of Ph2P-SeCd-Y (Y = -PPh2, -SR, -OR, and -NHR), SePPh2H embodies the catalytic performance, while HPPh2 serves as the catalyst for the formation of Ph2P-SeCdSe-Y (Y = -NHR or -OR). Our study brings a molecular-level insight into the relationship between the CdSe monomer and the phosphorous-containing side-product, which may advance the rational design and synthesis of quantum dots.

Large area multilayered graphene films were prepared by chemical vapour deposition using copper foils as substrate. We found that reaction temperature seriously affected the defects of the film but did not change the size, while reaction time dominated the defects and size. We further explained the surface deposition growth of the graphene film, and ascribed the growth of amorphous carbon to the reduction of copper catalysis. In addition, the graphene film showed improved electrocatalytic effect on hydrogen peroxide. This study opens an avenue for large area preparation of high quality graphene film for its electrochemical applications.

Silicon has been considered as one of the most promising anode material alternates for next-generation lithium-ion batteries, because of its high theoretical capacity, environmental friendliness, high safety, low cost, etc. Nevertheless, silicon-based anode materials (especially bulk silicon) suffer from severe capacity fading resulting from their low intrinsic electrical conductivity and great volume variation during lithiation/delithiation processes. To address this challenge, a few special constructions from nanostructures to anchored, flexible, sandwich, core–shell, porous and even integrated structures, have been well designed and fabricated to effectively improve the cycling performance of silicon-based anodes. In view of the fast development of silicon-based anode materials, we summarize their recent progress in structural design principles, preparation methods, morphological characteristics and electrochemical performance by highlighting the material structure. We also point out the associated problems and challenges faced by these anodes and introduce some feasible strategies to further boost their electrochemical performance. Furthermore, we give a few suggestions relating to the developing trends to better mature their practical applications in next-generation lithium-ion batteries.

In the past decades, Forster resonance energy transfer (FRET) has been applied in many biological applications to reveal the biological information at the nanoscale. Recently, graphene and graphene-like two-dimensional (2D) nanomaterials started to be used in FRET assays as donors or acceptors including graphene oxide (GO), graphene quantum dot (GQD), graphitic-carbon nitride nanosheets (g-C3N4) and transition metal dichalcogenides (e.g. MoS2, MnO2, and WS2). Due to the remarkable properties such as large surface to volume ratio, tunable energy band, photoluminescence and excellent biocompatibility, these 2D nanomaterials based FRET assays have shown great potential in various biological applications. This review summarizes the recent development of graphene and graphene-like 2D nanomaterials based FRET assays in applications of biosensing, bioimaging, and drug delivery monitoring.

Materials that are both stretchable and electrically conductive enable a broad spectrum of applications in sensing, actuating, electronics, optics and energy storage. The materials engineering concept of stretchable conductors is primarily based on combining nanowires, nanoribbons, nanoparticles, or nanocarbons with rubbery polymers to obtain composites with different abilities to transport charge and alter their nanoscale organization under strain. Although some of these composites reveal remarkably interesting multiscale reconfigurability and self-assembly phenomena, decreasing conductance with increased strain has restricted their widespread implementation. In a broader physical sense, the dependence of conductance on stress is undesirable because it requires a correlated change of electrical inputs. In this paper, we describe highly conductive and deformable sheets with a conductivity as high as 230 000 S cm−1, composed of silver nanoparticles, infiltrated within a porous aramid nanofiber (ANF) matrix...