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The microstructure of primary Mg 2 Si and the interface of Mg 2 Si / α -Mg modified by Sn and Sb elements in an as-cast Mg-5Sn-2Si-1.5Al-1Zn-0.8Sb (wt.%) alloy were investigated. In the primary Mg 2 Si phase not only the Si atoms but also the Mg atoms could be substituted by Sn and Sb atoms, resulting in the slightly reduced lattice constant a of 0.627 nm. An OR of Mg 2 Si phase and α -Mg in the form of [ 001 ] Mg 2 Si ∥ [ 01 1 ¯ 1 ] α , ( 220 ) Mg 2 Si ∥ ( 0 1 ¯ 12 ) α was discovered. Between primary Mg 2 Si phase and α -Mg matrix two transitional nano-particle layers were formed. In the rim region of primary Mg 2 Si particle, Mg 2 Sn precipitates sizing from 5 nm to 50 nm were observed. Adjacent to the boundary of primary Mg 2 Si particle, luxuriant columnar crystals of primary Mg 2 Sn phase with width of about 25 nm and length of about 100 nm were distributed on the α -Mg matrix. The lattice constant of the Mg 2 Sn precipitate in primary Mg 2 Si particle was about 0.756 nm. Three ORs between Mg 2 Sn and Mg 2 Si were found, in which the Mg 2 Sn precipitates had strong bonding interfaces with Mg 2 Si phase. Three new minor ORs between Mg 2 Sn phase and α -Mg were found. The lattice constant of primary Mg 2 Sn phase was enlarged to 0.813 nm owing to the solution of Sn and Sb atoms. Primary Mg 2 Sn had edge-to-edge interfaces with α -Mg. Therefore, the primary Mg 2 Si particle and α -Mg were united and the interfacial adhesion was improved by the two nano-particles layers of Mg 2 Sn phase.

A single-molecule field-effect transistor (FET) is the key building block of future electronic circuits. At the same time, a single-molecule FET is also a unique platform for studying physical mechanisms at the single-molecule level. How to construct single-molecule FETs and how to efficiently control the charge transfer characteristics of the devices are two core issues in the development of single-molecule FETs. In this review, we introduce the research progresses of single-molecule FETs with solid or liquid gates. Strategies to design single-molecule FETs are emphasized, including the design of functional molecules, the construction of gate electrodes and the control of molecule-electrode interface coupling. These single-molecule FETs provide a basis for practical applications and the exploration of physical laws. Specifically, the physical mechanisms of single-molecule FETs, especially those related to interfacial coupling, are explained, such as energy level shift, Coulomb blockade effect, Kondo effect and electron-phonon coupling. The applications of single-molecule FETs are summarized, including the regulation of quantum interference, spin, thermoelectric effect and superconductivity. Finally, the current opportunities and challenges in the field of single-molecule FETs are proposed, aiming to promote the future development of single-molecule electronics.

Conventional analytic techniques that measure ensemble averages and static disorder provide essential knowledge of the reaction mechanisms of organic and organometallic reactions. However, single-molecule junctions enable the in situ, label-free and non-destructive sensing of molecular reaction processes at the single-event level with an excellent temporal resolution. Here we deciphered the mechanism of Pd-catalysed Suzuki-Miyaura coupling by means of a high-resolution single-molecule platform. Through molecular engineering, we covalently integrated a single molecule Pd catalyst into nanogapped graphene point electrodes. We detected sequential electrical signals that originated from oxidative addition/ligand exchange, pretransmetallation, transmetallation and reductive elimination in a periodic pattern. Our analysis shows that the transmetallation is the rate-determining step of the catalytic cycle and clarifies the controversial transmetallation mechanism. Furthermore, we determined the kinetic and thermodynamic constants of each elementary step and the overall catalytic timescale of this Suzuki-Miyaura coupling. Our work establishes the single-molecule platform as a detection technology for catalytic organochemistry that can monitor transition-metal-catalysed reactions in real time.

Summary Conventional mechanistic studies based on detection of species concentration reveal the basic laws of matter conversion, but inherently display ensemble averages. Single-molecule detection provides a solution and direct visualization of reaction pathway rather than only detection of species. Here, we establish an in situ label-free electrical detection platform and report universal single-molecule electrical spectroscopy (SMES) of organocatalysis to decipher the intrinsic mechanism of a benzoin reaction. This SMES is capable of monitoring each event in a simple (homo-condensation) or complex (cross-condensation) system. Both experimental and theoretical results consistently revealed accuracy of the spectroscopic attribution and proved its reliability. Furthermore, the correlation of adjacent events in the spectroscopy indicated the local repeated interaction between a catalyst and a substrate. Through a new thermodynamic and kinetic model, the inventory of substrates around the single-molecule catalyst can be reversely deduced, which enables quantitative analysis of the target single molecule.

Development of high-performance and cost-effective catalysts for electrocatalytic hydrogen evolution reaction (HER) play crucial role in the growing hydrogen economy. Recently, the atomically dispersed metal catalysts have attracted increasing attention due to their ultimate atom utilization and great potential for highly cost-effective and high-efficiency HER electrocatalyst. Herein, we propose a high-temperature treatment strategy to furtherly improve the HER performance of atomically dispersed Pt-based catalyst. Interestingly, after appropriate high-temperature treatment on the atomically dispersed Pt0.8@CN, the Pt species on the designed N-doped porous carbon substrate with rich defect sites can be re-dispersed to single atom state with new coordination environment. The obtained Pt0.8@CN-1000 shows superior HER performance with overpotential of 13 mV at 10 mA cm−2 and mass activity of 11,284 mA/mgPt at −0.1 V, much higher than that of the pristine Pt0.8@CN and commercial Pt/C catalyst. The experimental and theoretical investigations indicate that the high-temperature treatment induces the restructuring of coordination environment and then the optimized Pt electronic state leads to the enhanced HER performances. This work affords new strategy and insights to develop the atomically dispersed high-efficiency catalysts.

Charge transport in a single-molecule junction is extraordinarily sensitive to both the internal electronic structure of a molecule and its microscopic environment. Two distinct conductance states of a prototype terphenyl molecule are observed, which correspond to the bistability of outer phenyl rings at each end. An azobenzene unit is intentionally introduced through atomically precise side-functionalization at the central ring of the terphenyl, which is reversibly isomerized between trans and cis forms by either electric or optical stimuli. Both experiment and theory demonstrate that the azobenzene side-group delicately modulates charge transport in the backbone via a single-molecule stereoelectronic effect. We reveal that the dihedral angle between the central and outer phenyl ring, as well as the corresponding rotation barrier, is subtly controlled by isomerization, while the behaviors of the phenyl ring away from the azobenzene are hardly affected. This tunability offers a new route to precisely engineer multiconfigurational single-molecule memories, switches, and sensors.

High energy density and enhanced rate capability are highly sought-after for supercapacitors in today’s mobile world. In this work, polyaniline/titanium carbide (MXene) (PANI/Ti3C2Tx) nanohybrid is synthesized through a facile and cost-effective self-assembly of one-dimensional (1D) PANI nanofibers and two-dimensional (2D) Ti3C2Tx nanosheets. PANI/Ti3C2Tx delivers greatly improved specific capacitance, ultrahigh rate capability (67% capacitance retention from 1 to 100 A·g−1) as well as good cycle stability. Electrochemical kinetic analysis reveals that PANI/Ti3C2Tx is featured with surface capacitance-dominated process and has a quasi-reversible kinetics at high scan rates, giving rise to an ultrahigh rate capability. By using PANI/Ti3C2Tx as positive electrode, an 1.8 V aqueous asymmetric supercapacitor (ASC) is successfully assembled, showing a maximum energy density of 50.8 Wh·kg−1 (at 0.9 kW·kg−1) and a power density of 18 kW·kg−1 (at 26 Wh·kg−1). Moreover, an 3.0 V organic ASC is also elaborately fabricated by using PANI/Ti3C2Tx, achieving an ultrahigh energy density of 67.2 Wh·kg−1 (at 1.5 kW·kg−1) and a power density of 30 kW·kg−1 (at 26.8 Wh·kg−1). The present work not only improves fundamental understanding of the structure-property relationship towards ultrahigh rate capability electrode materials, but also provides valuable guideline for the rational design of high-performance energy storage devices with both high energy and power densities.

The function of proteins depends on their structural flexibility and conformational change. By utilizing silicon-nanowire-based single-molecule electrical circuits, here we present a label-free real-time measurement method that can directly monitor conformational changes of a photosynthetic LH1-RC complex, reaching the ultimate goal of analytic chemistry. These results manifest that the conformation of the LH1-RC complex vibrates among four conformations with strong temperature dependence. At the optimal temperature, States 2 and 3 occupy the main conformations of the LH1-RC complex, and its conformational variation mostly emerges as anharmonic vibration modes, which contributes to photon acquisition and heat transmission. The influence of light activation on occurrence percentage is observed, resulting from light-driven quivering of pigments. Therefore, this avenue proves to be an efficient platform for revealing the fundamental mechanisms of various biological processes in vitro.

The microstructures and mechanical properties of as-cast Mg-5Sn-1Si magnesium alloy modified with trace elements Y, Bi, Sb and Sr were investigated and compared. Results show that the microstructure of the as-cast Mg-5Sn-1Si alloy consists of α-Mg, Mg2Si, Mg2Sn and Mg2(SixSn1-x) phases. After adding 0.8wt.% Y, 0.3wt.% Bi, 0.9wt.% Sb and 0.9wt.% Sr, respectively into the Mg-5Sn-1Si magnesium alloy, Mg24Y5, Mg3Bi2, Mg3Sb2 and Mg2Sr phases are precipitated accordingly. Trace elements can refine α-Mg grain and Chinese scriptshaped Mg2Si phase. Refinement efficiency of different trace elements on α-Mg grain and Mg2Si phase is varied. Sr element has the best refinement effect, followed by Sb and Bi, while Y has the least refinement effect. Mg-5Sn- 1Si-0.9Sr alloy has higher tensile properties than the other three modified alloys. The refinement mechanism of Y, Bi and Sr elements on Mg-5Sn-1Si magnesium alloy can be explained by the growth restriction factors and the solute undercooling. For Mg-5Sn-1Si-0.9Sb alloy, the heterogeneous nuclei of Mg3Sb2 phase is the main reason for the refinement of grains and second phases.

Coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, has rapidly spread and caused a severe global pandemic. Because no specific drugs are available for COVID-19 and few vaccines are available for SARS-CoV-2, accurate and rapid diagnosis of COVID-19 has been the most crucial measure to control this pandemic. Here, we developed a portable bifunctional electrical detector based on graphene fieldeffect transistors for SARS-CoV-2 through either nucleic acid hybridization or antigen-antibody protein interaction, with ultra-low limits of detection of ~0.1 and ~1 fg mL−1 in phosphate buffer saline, respectively. We validated our method by assessment of RNA extracts from the oropharyngeal swabs of ten COVID-19 patients and eight healthy subjects, and the IgM/IgG antibodies from serum specimens of six COVID-19 patients and three healthy subjects. Here we show that the diagnostic results are in excellent agreement with the findings of polymerase chain reaction-based optical methods; they also exhibit rapid detection speed (~10 min for nucleic acid detection and ~5 min for immunoassay). Therefore, our assay provides an efficient, accurate tool for high-throughput point-of-care testing. Electronic Supplementary Material Supplementary material is available in the online version of this article at 10.1007/s40843-020-1577-y.

Nitrogen doping is usually adopted in carbon based supercapacitor to enhance its relatively low energy density by providing extra pseudocapacity. However, the improvement of energy density is normally limited because the content of the introduced nitrogen species is not high and meanwhile only part of them is electrochemically active. Herein, we designed and fabricated a class of hierarchical nitrogen-rich porous carbons (HNPCs) possessing not only very high nitrogen content (up to 21.7 atom%) but also fully electrochemically active nitrogen species (i.e., pyridinic N, pyrrolic N and oxidized N). Especially, in the synthesis of HNPCs, graphitic carbon nitride (g-C3N4) was used in situ not only as a nitrogen source but also as a catalyst to facilitate the polymerization of phenol and formaldehyde (as carbon precursor) and as a template to create the hierarchical porous structure. As electrodes for aqueous symmetric supercapacitor, the HNPCs with full faradaic-active nitrogen functionalities exhibit excellent supercapacitor performance: high energy density of 36.8 Wh/kg at 2.0 kW/kg (maintaining 25.7 Wh/kg at 38 kW/kg), superior rate capability with 78% capacitance retention from 1.0 to 20 A/g and excellent cycling stability with over 95% capacitance retention after 10 000 cycles, indicating their promising application potential in electrochemical energy storage. This novel carbon material with high-content and full electrochemically active nitrogen species may find extensive potential applications in the energy storage/conversion, catalysis, adsorption, and so on.

The crystal-facet effect of catalytic supports plays a crucial role in tailoring the physicochemical properties of active sites and the surface chemically bonded polymer can also regulate the local...

Lithium-ion capacitors (LICs) could combine the virtues of high power capability of conventional super-3capacitors and high energy density of lithium-ion batteries. However, the lack of high-performance electrode materials and the kinetic imbalance between the positive and negative electrodes are the major challenge. In this study, Fe3O4 nanoparticles encapsulated in nitrogen-rich carbon (Fe3O4@NC) were prepared through a self-assembly of the colloidal FeOOH with polyaniline (PANI) followed by pyrolysis. Due to the well-designed nanostructure, conductive nitrogen-rich carbon shells, abundant micropores and high specific surface area, Fe3O4@NC-700 delivers a high capacity, high rate capability and long cycling stability. Kinetic analyses of the redox reactions reveal the pseudocapacitive mechanism and the feasibility as negative material in LIC devices. A novel LIC was constructed with Fe3O4@NC-700 as the negative electrode and expanded graphene (EGN) as the positive electrode. The well-matched two electrodes effectively alleviate the kinetic imbalance between the positive and negative electrodes. As a result, Fe3O4@NC-700//EGN LIC exhibits a wide operating voltage window, and thus achieves an ultrahigh energy density of 137.5 W h kg−1. These results provide fundamental insights into the design of pseudocapacitive electrode and show future research directions towards the next generation energy storage devices.

Trace explosives can be detected with the help of a portable device using a flexible active self-assembled monolayer (SAM). 9,10-diphenyl anthracene with aggregation-induced emission enhancement (AIEE) properties is selected as the fluorophore. Phosphoric acid as the anchor group is linked to the fluorophore through an alkyl chain and able to self-assemble into a dense monolayer on the HfO

Discrete nanosheets of silicon-doped AlPO4 molecular sieves (SAPO-34) with a thickness of ≈7 nm have been prepared through morphology-reserved synthesis with a lamellar aluminum phosphate as precursor. Cages of the nanosheets are in situ incorporated with copper oxide clusters. The CuO@SAPO-34 nanosheets exhibit a large external surface area with a high number of (010) channel pores on the surface. Due to the thin morphology, copper oxide clusters occupy the outmost cages with a probability >50 %. The distinctive configuration facilitates a new concept of pore mouth catalysis, i.e., reactant molecules larger than the pores cannot enter the interior of the molecular sieves but can interact with the CuO clusters at "the mouth" of the pore. In heterogeneous catalysis, CuO@SAPO-34 nanosheets have shown top performance in one-pot oxidation of cyclohexane to adipic acid by O2 , a key compound for the manufacture of nylon-66, which is so far produced using non-green nitric acid oxidation.

Device fabrication with organic single crystals is an important method for high device performance. High-quality organic semiconductor crystals are usually grown by a lab solution method, by which it is difficult to fabricate crystal arrays on the substrate, let alone achieve industrial production. Therefore, in this work, oriented single crystal arrays have been prepared by epitaxial growth. As an example, 2,7-dioctyl[1]benzothieno[3,2-b]benzothiophene (C8-BTBT) was spin-coated on the surface of a highly oriented melt-drawn isotactic polypropylene (iPP) film on 300 nm SiO2 substrates as an auxiliary dielectric layer, and highly oriented arrays of C8-BTBT single crystals are obtained by epitaxial growth in the solvent vapor annealing (SVA) approach. The devices based on the thus prepared C8-BTBT array have a yield of up to 81%, an average mobility of 2.5 cm2 V−1 s−1, a maximum mobility of 9.3 cm2 V−1 s−1 and an on/off ratio of 107. Hence, our method facilitates the large-scale fabrication of highly oriented single crystal arrays with high quality, which will promote further industrial application.

Single‐molecule electrical and spin switches have been one of the main research focuses in molecular electronics and spintronics because they may form the most important elements for the future information technology, thus attracting great attention in the scientific community and witnessing significant progresses benefiting from the combination of physics, chemistry, materials, and engineering. The key issue of constructing single‐molecule switches is the development of stimulus‐responsive systems that provide bistable or multiple states. In this review, we summarize the recent advances of this field in terms of the external stimulus that induces the switching. A variety of external stimuli, such as light, electric field, magnetic field, mechanical force, and chemical stimulus, have been successfully employed to activate the reversible switching in single‐molecule junctions by manipulating molecular structures, conformations, electronic states, and spin states. As a burgeoning field, we finally put forward the challenges in molecular electronics and spintronics that need to be solved, which will initiate intense research.

Developing an efficient approach of transforming biomass waste to functional carbon-based electrode materials applied in supercapacitor offers an important and high value-added practical application due to the abundance and considerable low price of biomass wastes. Herein, a hierarchical carbon functionalized with electrochemical-active oxygen-containing groups was fabricated by microwave treatment from the biomass waste of camellia oleifera. The obtained mesoporous carbon (MAC) owns nanosheet morphology, rich mesoporosity, large surface area (1726 m2/g) and very high oxygenic functionalities (16.2 wt%) with pseudocapacitive activity. Prepared electrode of supercapacitor and tested in 2.0 M H2SO4, the MAC exhibits an obvious pseudocapacitive activity and achieved a superior supercapacitive performance to that of directly activated carbon (DAC-800) including high specific capacitance (367 F/g vs. 298 F/g) and better rate performance (66% vs. 44%). The symmetrical supercapacitor based on MAC shows a high capacity of 275 F/g, large energy density of 9.55 Wh/kg (at power density of 478 W/kg) and excellent cycling stability with 99% capacitance retention after 10000 continuous charge-discharge, endowing the obtained MAC a promising functional material for electrochemical energy storage.

Summary Using nanoparticles (NPs) to catalyze chemical reactions for the formation of functional polymers with controlled polymerization is an important field of chemical research. In this article, we report an AuPd NP system as an active and stable catalyst to catalyze one-pot reaction of formic acid, 1,5-diisopropoxy-2,4-dinitrobenzene, and terephthaldehyde, leading to the controlled polymerization and the formation of polybenzoxazole (PBO) (Mw = 3.6 kDa). The one-pot reaction is AuPd NP size and composition dependent, and 8-nm Au39Pd61 NPs are the best catalyst for the polymerization. The highly pure PBO shows excellent thermal stability up to 600°C and improved chemical and mechanical stability under challenging environmental conditions compared with commercial PBO (Zylon, Mw = 40 kDa). The reported NP-catalyzed one-pot reaction to polymerization is not limited to the formation of PBO but can be extended as a general approach to rigid polymers that are important for ballistic fiber, anti-flame, and smart-textile applications.

Understanding the Cu-catalyzed electrochemical CO2 reduction reaction (CO2RR) under ambient conditions is both fundamentally interesting and technologically important for selective CO2RR to hydroca...

In this study, a reciprocating extrusion process (REP) was employed on Mg-5Sn-1Si-0.8Y magnesium alloy and the effect of the REP temperature (in the range of 340 °C to 400 °C) and number of REP passes (in the range of 2 to 8 at 340 °C) on the microstructural evolution of the alloy were investigated. The results show that the microstructure observed varied from edge to centre on the cross and longitudinal sections of the specimen. Upon increasing the extrusion temperature from 340 °C to 400 °C, the grain size distribution became uneven; the Mg2Si phase was concentrated at the grain boundaries, and the amount of Mg2Sn precipitated was reduced. In comparison with changing temperature, increasing the number of REP passes was more effective for improving the homogeneity of the alloy. With an increasing number of extrusion passes, the distributions for the grain size and second phases became increasingly uniform. In this study, an alloy subject to 8-REP passes and extrusion at 340 °C showed the finest and most homogeneous microstructure. Finally, a quantitative relationship between the REPed grain size and the Zener–Hollomon parameter was obtained.

The increasing need for clean and sustainable energy inspires researchers to explore low-cost nonprecious metal electrocatalysts for advanced energy storage and conversion. Herein, we develop a rea...

Molecular self-assembly into crystallised films or wires on surfaces produces a big family of motifs exhibiting unique optoelectronic properties. However, little attention has been paid to the fundamental mechanism of molecular crystallisation. Here we report a biomimetic design of phosphonate engineered, amphiphilic organic semiconductors capable of self–assembly, which enables us to use real-time in-situ scanning probe microscopy to monitor the growth trajectories of such organic semiconducting films as they nucleate and crystallise from amorphous solid states. The single-crystal film grows through an evolutionary selection approach in a two-dimensional geometry, with five distinct steps: droplet flattening, film coalescence, spinodal decomposition, Ostwald ripening, and self-reorganised layer growth. These sophisticated processes afford ultralong high-density microwire arrays with high mobilities, thus promoting deep understanding of the mechanism as well as offering important insights into the design and development of functional high-performance organic optoelectronic materials and devices through molecular and crystal engineering., Little attention has been paid to the fundamental mechanism of molecular self-assembly into crystallised films or wires on surfaces. Here the authors use real time in-situ scanning probe microscopy to monitor the growth trajectories of organic semiconducting films as they crystallize from an amorphous solid state under ambient conditions.

The modification effects of Sb on the morphologies of reinforcements Mg2Si and Mg2(Si,Sn) in Mg-4Si and Mg-5Sn-xSi(x = 1,4) alloys were investigated and the ideal adhesion works (Wad) between substrate (Mg3Sb2) and crystallization phases (Mg2Si, Mg2Sn and Mg2(Si,Sn)) were calculated using first principles calculations. The results indicate that the primary α-Mg matrix is significantly refined by the modification of Sb. For the eutectic mixture, the arm spacing of the intermetallics of Mg2Si or/and Mg2(Si,Sn) is decreased. For the primary Mg2Si or/and Mg2(Si,Sn) which in coarse angular bulk forms without any modification was rounded and distributed uniformly on the α-Mg matrix after modification. The primary Mg2Si in octahedrons morphology without modification grows in tetrakaidecahedron mode in Sb modified Mg-4%Si alloys. The clearly straight edges and the sharp corners of the primary Mg2Si become ambiguity, and tend to being spheroidized. Primary Mg2Si, Mg2Sn and Mg2(Si,Sn) were refined because Mg3Sb2 precipitated during solidification could act as their nuclei. When some Sn atoms replace equivalent Si from Mg2Si phase, the interfaces adhesion work (Wad) values between substrate and new crystal will increase. Moreover, the interface cohesive strength of Sb-Mg-Si(/Sn/Si-Sn) or Sb-Mg-Mg-Si(/Sn/Si-Sn) will be stronger than the others.

Mg-6Zn-xCe (x = 0, 0.6, 1.0, 2.0) alloy ingots with diameter of 50 mm were extruded into bars with diameter of 12 mm at 300 °C. The microstructures were analyzed by X-ray diffraction, optical microscopy, scanning electron microscopy and transmission electron microscopy, and mechanical properties were tested at room temperature. The results showed that major intermetallic composition in as-cast Mg-6Zn and Mg-6Zn-0.6Ce alloys was Mg4Zn7 phase, during extrusion Mg4Zn7 phase was dissolved into matrix and then precipitated as MgZn2. In as-cast and as-extruded Mg-6Zn-1Ce and Mg-6Zn-2Ce alloys the major intermetallic composition was T phase. The microstructure of as-extruded alloy was refined due to complete dynamic recrystallization, the average grain size decreased with increasing Ce content, which were 12.1, 11.7, 11.0 and 10.0 mm, respectively. High density MgZn2 precipitated in Mg-6Zn and Mg-6Zn-0.6Ce alloys. The broken T phase particles were distributed linearly along extrusion direction. Mg-6Zn-0.6Ce alloy exhibited a high yield strength of 226.3 MPa that was about 24 MPa higher than Mg-6Zn alloy. However, with increasing Ce contents, the strengths were decreased slightly because the effects of precipitation strengthening of MgZn2 and solid solute strengthening of Zn were weakened though the strengthening effect of T phase was enhanced.

Summary We report here a supercatalyst for oxygen reduction of Pt/CNx/Ni in a unique ternary heterostructure, in which the Pt and the underlying Ni nanoparticles are separated by two to three layers of nitrogen-doped carbon (CNx), which mediates the transfer of electrons from the inner Ni to the outer Pt and protects the Ni against corrosion at the same time. The well-engineered low-Pt catalyst shows ∼780% enhanced specific mass activity or 490% enhanced specific surface activity compared with a commercial Pt/C catalyst toward oxygen reduction. More importantly, the exceptionally strong tune on the Pt by the unique structure makes the catalyst superbly stable, and its mass activity of 0.72 A/mgPt at 0.90 V (well above the US Department of Energy's 2020 target of 0.44 A/mgPt at 0.90 V) after 50,000 cyclic voltammetry cycles under acidic conditions is still better than that of the fresh commercial catalyst., Graphical Abstract, Highlights • Matched band structures among Pt/CNx/Ni enable electron transfer from Ni to Pt • Enhanced Pt-CNx interaction by underlying Ni prevents Pt from coalescence and oxidation • Encapsulated Ni is protected from corrosion and maintains the structure stability of THS, Catalysis; Electrochemical Energy Conversion; Energy Materials

A noncrystalline Ni–B alloy in the shape of nanotubes has demonstrated its superior catalytic performance for some hydrogenation reactions. Remarkable synergistic effects have been observed in many reactions when bimetallic catalysts were used; however, bimetallic noncrystalline alloy nanotubes are far less investigated. Here, we report a simple acetone-assisted lamellar liquid crystal approach for synthesizing a series of bimetallic Ni–Co–B nanotubes and investigate their catalytic performances. The dilution effect of acetone on liquid crystals was characterized by small-angle X-ray diffraction (SAXRD) and scanning electron microscopy (SEM). The Ni/Co molar ratio of the catalyst was varied to study the composition, porous structure, electronic interaction, and catalytic efficiency. In the liquid-phase hydrogenation of p-chloronitrobenzene, the as-prepared noncrystalline alloy Ni–Co–B nanotubes exhibited higher catalytic activity and increased stability as compared to Ni–B and Co–B alloy nanotubes due to electronic interactions between the nickel and cobalt. The excellent hydrogenation performance of the Ni–Co–B nanotubes was attributed to their high specific surface area and the characteristic confinement effects, compared with Ni–Co–B nanoparticles.

Supramolecular assembly is a promising bottom-up approach for producing materials that behave as charge transporting components in electronic devices. Although extensive advances have been made during the past two decades, formidable challenges exist in controlling the local randomness present in supramolecular assemblies. Here, a temperature-triggered supramolecular assembly strategy using heat to heal defects and disorders is reported. The central concept of the molecular design-named the "Tetris strategy" in this research-is to: i) increase the rotational freedom of the molecules through thermal perturbation, ii) induce conformation-fitting of adjacent molecules through two different kinds of intermolecular [π···π] interactions, and finally iii) lock the nearby molecules in inactive co-conformations. Experimentally, upon heating to 57 °C, amorphous solid-state films undergo spontaneous assembly, leading to the growth of uniform and highly ordered microwire arrays. Temperature-triggered supramolecular assembly provides an approach closer to the precision control of assembled structures and presents with a broad canvas to work on in approaching a new generation of supramolecular electronics. Tetris is a registered trademark of Tetris Holding, LLC, used with permission.

A single-molecule electrical method is developed for precisely realizing amino acid detection and chirality recognition., One of the ultimate goals of analytic chemistry is to efficiently discriminate between amino acids. Here we demonstrate this ability using a single-molecule electrical methodology based on molecular nanocircuits formed from stable graphene-molecule-graphene single-molecule junctions. These molecular junctions are fabricated by covalently bonding a molecular machine featuring a permethylated-β-cyclodextrin between a pair of graphene point contacts. Using pH to vary the type and charge of the amino acids, we find distinct multimodal current fluctuations originating from the different host-guest interactions, consistent with theoretical calculations. These conductance data produce characteristic dwell times and shuttling rates for each amino acid, and allow accurate, statistical real-time, in situ measurements. Testing four amino acids and their enantiomers shows the ability to distinguish between them within a few microseconds, thus paving a facile and precise way to amino acid identification and even single-molecule protein sequencing.

The spindle characteristic signal (forces and vibrations) at different friction stir lap welding (FSLW) parameters were studied. The result indicated that the spindle force and vibration have different trends with the change of welding parameters. For further study, the spindle dynamic performance evaluation model by means of the Technique for Order Preference by Similarity to the Ideal Solution (TOPSIS method) was established. The model was used to calculate the relative approach degree B under different welding process parameters. The correlation between the characteristic signal and the joint properties was obtained. The model was validated by mechanical performance testing and microscopic observation. The results showed that the model evaluations were consistent with the experimental results.

Molecule-based field-effect transistors (FETs) are of great significance as they have a wide range of application prospects, such as logic operations, information storage and sensor monitoring. This account mainly introduces and reviews our recent work in molecular FETs. Specifically, through molecular and device design, we have systematically investigated the construction and performance of FETs from macroscale to nanoscale and even single molecule. In particular, we have proposed the broad concept of molecular FETs, whose functions can be achieved through various external controls, such as light stimulation, and other physical, chemical or biological interactions. In the end, we tend to focus the discussion on the development challenges of single-molecule FETs, and propose prospects for further breakthroughs in this field.

An efficient CuPd nanoparticle (NP) catalyst (3 nm CuPd NPs deposited on carbon support) is designed for catalyzing electrochemical allylic alkylation in water/isopropanol (1:1 v/v) and 0.2 m KHCO3 solution at room temperature. The Pd catalysis was Pd/Cu composition-dependent, and CuPd NPs with a Pd/Cu ratio close to one are the most efficient catalyst for the selective cross-coupling of alkyl halides and allylic halides to form C-C hydrocarbons with product yields reaching up to 99 %. This NP-catalyzed electrochemical allylic alkylation expands the synthetic scope of cross-coupling reactions and can be further extended to other organic reaction systems for developing green chemistry electrosynthesis methods.

Uniform single-crystalline hydroxyapatite nanotubes with hexagonal facets are synthesized via a distinctive organoamines-assisted biomimetic route. These novel HA nanotubes exhibit exceptional performance in stimulating osteoblast proliferation, which gives them intriguing potential for bone repair.

Water electrolysis, especially the one in alkaline liquid electrolyte, offers an attractive strategy for hydrogen production as well as plays key role in many industrial energy conversion processes, such as chlor-alkali electrolyzer, water-alkali electrolyzer, and metal-O2 batteries. In this chapter, the working principles of water electrolysis in alkaline electrolyte, recent progress on several kinds of crucial catalysts for cathode hydrogen evolution reaction (HER) and anode oxygen evolution reaction (OER), and the related cell components have been introduced and summarized. Especially, the specific discussions from the aspects of HER and OER electrocatalysts design and the enhancement of catalytic stability have been presented. Perspectives of some directions for the future research are put forward as well. It is expected that this chapter will provide a better understanding of water electrolysis in alkaline liquid electrolyte for the general readers, and gives a guidance for the further study in energy conversion fields.

The past two decades have witnessed increasingly rapid advances in the field of single-molecule electronics, which are expected to overcome the limitation of the miniaturization of silicon-based microdevices, thus promoting the development of device manufacturing technologies and characterization means. In addition to this, they can enable us to investigate the intrinsic properties of materials at the atomic- or molecular-length scale and probe new phenomena that are inaccessible in ensemble experiments. In this perspective, we start from a brief introduction on the manufacturing method of graphene-molecule-graphene single-molecule junctions (GMG-SMJs). Then, we make a description on the remarkable functions of GMG-SMJs, especially on the investigation of single-molecule charge transport and dynamics. Finally, we conclude by discussing the main challenges and future research directions of molecular electronics.

Fiber-forming polymer polyethylene terephthalate chips were blended with Eu2+ and Dy3+ co-doped SrAl2O4 (SAOED) to afford luminous fiber with long and persistent afterglow. A dynamical model was set up to study the afterglow process in order to correlate the afterglow characteristics with the trap levels of SAOED and luminous fiber. The results indicated that the illustration of initial afterglow for luminous fiber was obviously lower than that of SAOED, but its decay process was moderately slow and therefore longer than that of SAOED. Compared with SAOED, the thermo-luminescence peak of the fiber shifted to the higher temperature, and its intensity was lower than that of SAOED. With the time extension of delay time after excitation, the depth of trap level for luminous fiber in our studies did not show any significant change. The afterglow decay behavior can be best fit by using I = I0/(1 + bt)2; the fitting showed that the afterglow decay process followed the second order dynamics.

The construction of earth-abundant and non-noble-metal-based oxygen evolution reaction (OER) electrocatalysts that could work effectively with long-term stability in alkaline electrolyte is of prim...

Benefiting from the development of molecular electronics and molecular plasmonics, the interplay of light and electronic transport in molecular junctions has attracted growing interest among researchers in both fields, leading to a new research direction of “single-molecule optoelectronics”. Here, we review the latest developments of photo-modulated charge transport, electroluminescence and Raman spectroscopy from single-molecule junctions, and suggest future directions for single-molecule optoelectronics.

Graphene with atomically smooth and configuration-specific edges plays the key role in the performance of graphene-based electronic devices. Remote hydrogen plasma etching of graphene has been proven to be an effective way to create smooth edges with a specific zigzag configuration. However, the etching process is still poorly understood. In this study, with the aid of a custom-made plasma-enhanced hydrogen etching (PEHE) system, a detailed graphene etching process by remote hydrogen plasma is presented. Specifically, we find that hydrogen plasma etching of graphene shows strong thickness and temperature dependence. The etching process of single-layer graphene is isotropic. This is opposite to the anisotropic etching effect observed for bilayer and thicker graphene with an obvious dependence on temperature. On the basis of these observations, a geometrical model was built to illustrate the configuration evolution of graphene edges during etching, which reveals the origin of the anisotropic etching effect. By further utilizing this model, armchair graphene edges were also prepared in a controlled manner for the first time. These investigations offer a better understanding of the etching process for graphene, which should facilitate the fabrication of graphene-based electronic devices with controlled edges and the exploration of more interesting properties of graphene.

Developing earth-abundant, highly active, and durable electrocatalysts for the oxygen evolution reaction (OER) is very important for many renewable energy conversion processes. Herein, we report a novel OER electrocatalyst of NiCo layered double hydroxide@NiCo-hydroxysulfide (NiCo-LDH@HOS) nanosheet arrays, which are prepared by a rapid room-temperature sulfurization of the surface of NiCo-LDH nanosheets grown on Ni foam. The surface sulfurization exerts important influences/changes on the structure, composition, surface properties and chemistry of NiCo-LDH. After surface sulfurization, the resulted NiCo-hydroxysulfide layer armor improved electrical conductivity and chemical resistance to alkaline electrolyte, delivers a stable current density of 10.0 mA cm–2 at a low overpotential of 293 mV in 0.1 M KOH solution, maintaining high stability during a 62 h test. The achieved enhanced oxygen evolution activity and improved durability are superior to those of NiCo-LDH nanosheets and benchmark commercial RuO2...

Two kinds of warm-toned (yellow/orange-emitting) long-lasting phosphorescent composites, namely, SiO2/red-emitting color converter@SrAl2O4:Eu2+, Dy3+ (SiO2/RECC@SAOED) and PMMA/red-emitting color converter@SrAl2O4:Eu2+, Dy3+ (PMMA/RECC@SAOED), were prepared in this study. Their morphological and luminescent properties were compared with those of the uncoated SAOED phosphor and analyzed in detail. SiO2/RECC@SAOED and PMMA/RECC@SAOED particles presented a coarse surface with an increased diameter of 12 µm. In addition to the first emission peak at 525 nm similar to that of the uncoated SAOED, an emission peak occurred in the emission spectra of SiO2/RECC@SAOED and PMMA/RECC@SAOED at 610 and 612 nm, respectively. The chromaticity coordinates of SiO2/RECC@SAOED and PMMA/RECC@SAOED moved to the yellow (x = 0.3769, y = 0.5006) and orange (x = 0.4647, y = 0.4671) areas compared with those of the uncoated SAOED in the green area (x = 0.2781, y = 0.5777). The afterglow decay curve revealed that the afterglow property of SiO2/RECC@SAOED was better than that of PMMA/RECC@SAOED.

为了满足传统硅基电子器件日益微型化的需求, 科学家们前瞻性地提出了将单个分子或者分子聚集体夹在电极之间制备分子电子器件的前沿研究方向. 分子电子器件功能化的实现需要从分子工程、界面工程以及材料工程的角度综合考虑. 本文总结了近期利用外界环境来调控分子电子器件功能的最新进展. 鉴于化学刺激所引起的显著效果, 作者展望了分子电子器件在单分子化学反应动力学中的应用前景以及未来的发展方向.

We present a robust approach to fabricate stable single-molecule junctions at room temperature using single-layer graphene as nanoelectrodes. Molecular scale nano-gaps in graphene were generated using an optimized fast-speed feedback-controlled electroburning process. This process shortened the time for creating a single nano-gap to be less than one minute while keeping a yield higher than 97 %. To precisely control the gap position and minimize the effects of edge defects and the quantum confinement, extra-narrow grooves were pre-patterned in the graphene structures with oxygen plasma etching. Molecular junctions were formed by bridging the nano-gaps with amino-functionalized hexaphenyl molecules by taking advantage of chemical reactions between the amino groups at the two ends of the molecules and the carboxyl groups at the edges of graphene electrodes. Electronic transport measurements and transition voltage spectroscopy analysis verified the formation of single-molecule devices. First-principles quantum transport calculations show that the highest occupied molecular orbital of hexaphenyl is closer to the Fermi level of the graphene electrodes and thus the devices exhibit a hole-type transport characteristics. Some of these molecular devices remained stable up to four weeks, highlighting the potential of graphene nano-electrodes in the fabrication of stable single-molecule devices at room temperature.

With the successful preparation of γ-alumina with high-energy external surfaces such as {111} facets, the crystal-facet effect of γ-Al2O3 on surface-loaded CrOx has been explored for semihydrogenat...

In this work, a series of Pt nanocrystallines (Pt NCs) supported on TiO2 substrate with controlled thickness of carbon layers (C-Pt/TiO2) were synthesized. Well-dispersed Pt NCs were facilely synthesized at room temperature by a photo-reduction process in lytropic liquid crystal (LCs). Surface tuning of the carbon layers on Pt/TiO2 catalysts was achieved by varying the calcination atmospheres (in argon, air, and oxygen) and characterized by XPS and HRTEM. The influence of the coated carbon layers on the catalytic activity of catalysts is investigated by CO oxidation reaction which presented the following ranks: C-Pt/TiO2-O2 > C-Pt/TiO2-Air > C-Pt/TiO2-Ar. It is found that the carbon layer coating can stabilize the Pt NCs and enable them anti-sintering at high temperature. This finding provides new insight into understanding the C-Pt/TiO2 ternary system for tuning their catalytic performance.

Biomass-derived carbon (BDCs) materials are receiving extensive attention as electrode materials for energy storage because of the considerable economic value offering possibility for practical applications, but the electrochemical capacitance of BDCs are usually relatively low resulted from limited electric double layer capacitance. Herein, an oxygen-rich porous carbon (KMAC) was fabricated through a rapid and convenient microwave assisted carbonization and KOH activation of camellia oleifera shell. The obtained KMAC possesses three-dimensional porous architecture, large surface area (1229 m2/g) and rich oxygen functionalities (C/O ratio of 1.66). As the electrode materials for supercapacitor, KMAC exhibits superior supercapacitive performances as compared to the activated carbon (KAC) derived from direct carbonization/KOH activation method in 2.0 M H2SO4 (315 F/g vs. 202 F/g) and 6.0 M KOH (251 F/g vs. 214 F/g) electrolyte due to the rich oxygen-containing functional groups on the surface of porous carbon resulted from the developed microwave-assisted carbonization/activation approach.

To test and clarify the stability of afterglow performance of luminescent fibers can accelerate the step of the commercialized application on luminescent textiles. This work investigated the possible effects of a number of working conditions on the afterglow characteristics of luminous fibers. The fibers in our studies did not show any significant change in their afterglow brightness and duration after storage for 12 months under conditions of constant temperature and humidity, after 5 hours of light exposure, or soaking in water for 4 hours. The insignificant decay appears to follow the same mechanism. Thermal perturbation seemed to cause some changes to the initial brightness and decay time with the best performance being observed at about 80°C. Moreover, contact with acid or base for 5 minutes only resulted in slight reduction of the afterglow brightness. Our studies thus indicate a high degree of stability of the afterglow performance of the luminous fibers used.