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The completely selective oxidation of toluene to benzaldehyde with dioxygen, without the need to use H2O2, halogens, or any radical initiators, is a reaction long desired but never previously successful. Here, we demonstrate the enzyme-like mechanism of the reaction over hexadecylphosphate acid (HDPA)-bonded nano-oxides, which appear to interact with toluene through specific recognition. The active sites of the catalyst are related to the ability of HDPA to change its bonding to the oxides between monodentate and bidentate during the reaction cycle. This greatly enhances the mobility of the crystal oxygen or the reactivity of the catalyst, specifically in toluene transformations. The catalytic cycle of the catalyst is similar to that of methane monooxygenase. In the presence of catalyst and through O2 oxidation, the conversion of toluene to benzaldehyde is initiated at 70 dC. We envision that this novel mechanism reveals alternatives for an attractive route to design high-performance catalysts with bioinspired structures.

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 production of functionalized anilines by chemoselective hydrogenation of nitroarenes occupies an important position in the chemical industries. Recently, cobalt and nitrogen codoped carbon (Co–...

Methanol is one of the most desirable C1 products in the electrocatalytic CO2 reduction reaction (CO2RR). The intricate nature of the reaction pathway involving six-electron transfer, however, makes the process highly challenging. In this work, we report a ternary heterostructural catalyst CoO/CN/Ni, with cobalt as catalytic centers supported on N-doped carbon with underlying nickel, which presents a remarkably promoted Faraday efficiency (70.7%) and current density (10.6 mA/cm2) towards methanol, compared with CoO/CN. It appears that the nickel underneath plays an essential role by donating electrons to outer CN layer and thus changes the electronic state of surface and then of the cobalt species which act as catalytic centers. Notably, the unique catalyst shows not only high electrocatalytic activity and selectivity to CH3OH, but also suppression of H2 formation and well-preserved catalytic performance during the long-term test of reaction. Simultaneously, isotropic labeling and electrochemical experiment prove the carbon source.

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.

The majority of the protein structures have been elucidated under equilibrium conditions. The aim herein is to provide a better understanding of the dynamic behavior inherent to proteins by fabricating a label-free nanodevice comprising a single-peptide junction to measure real-time conductance, from which their structural dynamic behavior can be inferred. This device contains an azobenzene photoswitch for interconversion between a well-defined cis, and disordered trans isomer. Real-time conductance measurements revealed three distinct states for each isomer, with molecular dynamics simulations showing each state corresponds to a specific range of hydrogen bond lengths within the cis isomer, and specific dihedral angles in the trans isomer. These insights into the structural dynamic behavior of peptides may rationally extend to proteins. Also demonstrated is the capacity to modulate conductance which advances the design and development of bioinspired electronic nanodevices.

Summary Here, we report a high-performance catalyst Cu@Na-Beta, prepared via a unique method to embed 2∼5 nm Cu nanoparticles in crystalline particles of Na-Beta zeolite, for CO2 hydrogenation to ethanol as the only organic product in a traditional fixed-bed reactor. The ethanol yield in a single pass can reach ∼14% at 300°C, ∼12,000 mL·gcat−1·h−1, and 2.1 MPa, corresponding to a space-time yield of ∼398 mg·gcat−1·h−1. The key step of the reaction is considered as the rapid bonding of CO2∗ with surface methyl species at step sites of Cu nanoparticles to CH3COO∗ that converts to ethanol in following hydrogenation steps. The points of the catalyst seemed to be that the irregular copper nanoparticles stuck in zeolitic frameworks offer high density of step sites and the intimate surrounding of zeolitic frameworks strongly constrain the CO2 reactions at the copper surface and block by-products, such as methanol, formic acid, and acetyl acid.

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.

To study the effect of adjacent hydroxyl to the active sites, several acid catalysts, i.e. substituted benzoic acids with adjacent carboxyl are employed in the fructose dehydration to 5-hydroxymethylfurfural (HMF). Experimental results reveal that Bronsted acid sites with adjacent carboxyl present higher catalytic ability than isolated ones. Computational results suggest that the adjacent sites lead to co-interaction on fructose, corresponding more stable transition state and faster HMF formation rate. Based on the enhancement from the adjacent sites, a novel ordered mesoporous carbon (OMC) full of carboxyls in surface is prepared and turns out to be an effective solid catalyst for HMF production from fructose derived from biomass.

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.

Heterogeneous interfaces that are ubiquitous in optoelectronic devices play a key role in the device performance and have led to the prosperity of today's microelectronics. Interface engineering provides an effective and promising approach to enhancing the device performance of organic field-effect transistors (OFETs) and even developing new functions. In fact, researchers from different disciplines have devoted considerable attention to this concept, which has started to evolve from simple improvement of the device performance to sophisticated construction of novel functionalities, indicating great potential for further applications in broad areas ranging from integrated circuits and energy conversion to catalysis and chemical/biological sensors. In this review article, we provide a timely and comprehensive overview of current efficient approaches developed for building various delicate functional interfaces in OFETs, including interfaces within the semiconductor layers, semiconductor/electrode interfaces, semiconductor/dielectric interfaces, and semiconductor/environment interfaces. We also highlight the major contributions and new concepts of integrating molecular functionalities into electrical circuits, which have been neglected in most previous reviews. This review will provide a fundamental understanding of the interplay between the molecular structure, assembly, and emergent functions at the molecular level and consequently offer novel insights into designing a new generation of multifunctional integrated circuits and sensors toward practical applications.

A series of hexadecylphosphate acid (HDPA) terminated mixed-oxide nanoparticles have been investigated to catalyze the oxidation of toluene exclusive to benzaldehyde under mild conditions in an emulsion of toluene/water with the catalysts as stabilizers. With the HDPA-Fe2O3/Al2O3 as the basic catalyst, a series of transition metals, such as Mn, Co, Ni, Cu, Cr, Mo, V, and Ti, was respectively doped to the basic catalyst to modify the performance of the catalytic system, in expectation of influencing the mobility of the lattice oxygen species in the oxide catalysts. Under normally working conditions of the catalytic system, the nanoparticles of catalysts located themselves at the interface between the oil and water phases, constituting the Pickering emulsion. Both the doped iron oxide and its surface adsorbed hexadecylphosphate molecules were essential to the catalytic system for excellent performances with high toluene conversions as well as the exclusive selectivity to benzaldehyde. Under optimal conditions, ∼83% of toluene conversion and >99% selectivity to benzaldehyde were obtained, using molecular oxygen as oxidant and HDPA-(Fe2O3-NiO)/Al2O3 as the catalyst. This process is green and low cost to produce high quality benzaldehyde from O2 oxidation of toluene.

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.

International audience; The aim of molecular electronics is to miniaturize active electronic devices and ultimately construct single-molecule nanocircuits using molecules with diverse structures featuring various functions, which is extremely challenging. Here, we realize a gate-controlled rectifying function (the on/off ratio reaches ∼60) and a high-performance field effect (maximum on/off ratio >100) simultaneously in an initially symmetric single-molecule photoswitch comprising a dinuclear ruthenium-diarylethene (Ru-DAE) complex sandwiched covalently between graphene electrodes. Both experimental and theoretical results consistently demonstrate that the initially degenerated frontier molecular orbitals localized at each Ru fragment in the open-ring Ru-DAE molecule can be tuned separately and shift asymmetrically under gate electric fields. This symmetric orbital shifting (AOS) lifts the degeneracy and breaks the molecular symmetry, which is not only essential to achieve a diode-like behavior with tunable rectification ratio and controlled polarity, but also enhances the field-effect on/off ratio at the rectification direction. In addition, this gate-controlled symmetry-breaking effect can be switched on/off by isomerizing the DAE unit between its open-ring and closed-ring forms with light stimulus. This new scheme offers a general and efficient strategy to build high-performance multifunctional molecular nanocircuits.

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.

An oxide catalyst plays an important role in environmental catalysis. Metal chlorides are widely used as precursors in the preparation of oxide catalysts. However, residual chlorine usually influen...

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...

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.

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.

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.

An electric field promotes an unprecedented stepwise Diels-Alder cycloaddition reaction mechanism., Precise time trajectories and detailed reaction pathways of the Diels-Alder reaction were directly observed using accurate single-molecule detection on an in situ label-free single-molecule electrical detection platform. This study demonstrates the well-accepted concerted mechanism and clarifies the role of charge transfer complexes with endo or exo configurations on the reaction path. An unprecedented stepwise pathway was verified at high temperatures in a high-voltage electric field. Experiments and theoretical results revealed an electric field–catalyzed mechanism that shows the presence of a zwitterionic intermediate with one bond formation and variation of concerted and stepwise reactions by the strength of the electric field, thus establishing a previously unidentified approach for mechanistic control by electric field catalysis.

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.

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.

Two-dimensional (2D) materials have attracted great attention due to their unique physical and chemical properties derived from the dimensionality effect and modulation in their band structure. Herein, an important industrial catalytic material, gamma alumina (γ-Al2O3) with well-defined two-dimensional nanosheet structure was fabricated by a designed crown ether induced assembly approach. The obtained γ-Al2O3 nanosheets with a thickness of ∼4 nm possess high surface area (351 m2/g) and 16% pentacoordinate Al3+ sites which are the main catalytic active sites for ethanol dehydration to ethylene, compared to almost no pentacoordinate Al3+ sites for the commercial γ-Al2O3 nanoparticles. Furtherly, systematical investigation reveals that the crown ether plays the key role in the assembly of nanosheet structure. As a catalyst for ethanol dehydration to ethylene, the obtained alumina nanosheets with easily-accessible surface and more active sites, exhibit a superior catalytic performance to the commercial alumina with a much higher yield at large space velocity.

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.

The present work investigated the effect of reduction-oxidation(R-O) pretreatment on the CO oxidation activity of Co3O4/Al2O3 catalyst. After the reduction-oxidation treatment, the crystalline size of Co3O4 supported on the Al2O3 decreased and it exposed more Co3+, resulting in the improvement of CO oxidation activity. Compared with the as-prepared conventional Co3O4/Al2O3 catalyst, the Co3O4/Al2O3-R-O catalyst is easy to be reduced at lower temperature. The surface reconstruction occurred during the reduction-oxidation pretreatment accounting for the improvement of the catalytic activity. This study reveals the importance of R-O pretreatment as a strategy for the improvement of supported metal oxide catalyst with advanced catalytic performance.

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...

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.

Ni30 Pd70 nanoparticles supported on nitrogen-doped graphene (NG) acts as a catalyst for the hydrodehalogenation of halogenated aromatics under mild reaction conditions. It reduces mono- or dichloroarenes to the corresponding dehalogenated arenes in >90 % yield in 10 % aqueous isopropanol solvent at or below 50 °C within 5 h. Tests on a variety of substrates containing various functional groups show that the catalyst is selective for reduction of C-Cl and C-Br bonds. In addition, this catalyst completely hydrodehalogenates high-concentration solutions of dioxin, polychlorinated biphenyls, chloroaromatic constituents of the defoliant agent orange, and polybrominated diphenyl ethers in 12 h. The catalyst is reusable and shows no morphological or compositional changes after 5 cycles. This methodology offers a powerful, low-cost, and safe technology for the degradation of polyhalogenated aromatics, and may be useful for preventing proliferation of these toxins in the environment from causing serious health issues.

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.

Color-tuned long lasting phosphorescent composite PMMA/RECC@SrAl2O4:Eu2+,Dy3+ (SAOED) with warm-toned phosphorescent color and excellent afterglow properties were prepared by coating PMMA and a red light-emitting coumarin fluorescent dye color converter (RECC) and PMMA on the surface of the green emitting long lasting phosphor SAOED. X-ray diffraction (XRD) patterns show that the crystal lattice of the PMMA/RECC@SAOED samples are identical to the uncoated SAOED. The photoluminescence (PL) emission spectra of the PMMA/RECC@SAOED consist of two broad band ranging from 450 to 575 nm and 576–700 nm, and the spectra intensity in the range of 576–700 nm increased gradually with the increment of RECC. The CIE chromaticity coordinates and the luminescence images of the PMMA/RECC@SAOED samples indicate that the emitting color of PMMA/RECC@SAOED is composed of the phosphorescent color of SAOED and the fluorescent color of RECC, and it exhibits a reddish emitting color with color purity of 0.8726 when the concentration of the RECC was added to 0.9%. Even though the coating layer of RECC has a negative influence on the quantum yield (QY) and afterglow brightness of PMMA/RECC@SAOED, the afterglow curves of PMMA/RECC@SAOED are similar in shape with the uncoated SAOED, both of them are fitted well with a third-order exponential equation.

The hydrogen bond represents a fundamental interaction widely existing in nature, which plays a key role in chemical, physical and biochemical processes. However, hydrogen bond dynamics at the molecular level are extremely difficult to directly investigate. Here, in this work we address direct electrical measurements of hydrogen bond dynamics at the single-molecule and single-event level on the basis of the platform of molecular nanocircuits, where a quadrupolar hydrogen bonding system is covalently incorporated into graphene point contacts to build stable supramolecule-assembled single-molecule junctions. The dynamics of individual hydrogen bonds in different solvents at different temperatures are studied in combination with density functional theory. Both experimental and theoretical results consistently show a multimodal distribution, stemming from the stochastic rearrangement of the hydrogen bond structure mainly through intermolecular proton transfer and lactam–lactim tautomerism. This work demonstrates an approach of probing hydrogen bond dynamics with single-bond resolution, making an important contribution to broad fields beyond supramolecular chemistry., Hydrogen-bonds are widely found in many systems, such as DNAs and supramolecular assemblies, but it remains challenging to detect their dynamics at a molecular level. Here, Zhou et al. study the stochastic arrangement of hydrogen bonds using single-molecule junctions connected to graphene electrodes.

Heteroatom doping is a very important approach to improve the performances of carbon-based electrode materials applied in the energy storage and conversion field. Herein, a strategy based on the design of faradaic redox active sites has been developed to synthesize nitrogen and oxygen co-doped carbon foam with a hierarchical porous structure. By a facile two-step method of incipient impregnation and carbonization, the quinone-amine polymer (PAQ) precursor can be in situ polymerized and carbonized on the surface of a nanosized MgO template to obtain carbon foam after removal of MgO with acetic acid. The obtained carbon foam possesses a high content of heteroatoms (total 12.26 at%) as well as faradaic active sites including nitrogen- and oxygen-containing functional groups, which not only enhance the wettability of the electrode material surface to electrolyte but also impart high pseudo-capacitance to the carbon-based skeleton. In addition, the hierarchical micro–meso–macro porous structure provides a large specific surface area (1215 m2 g−1) and a mediated pathway for electrolyte ion diffusion. Serving as a symmetric supercapacitor electrode material in aqueous electrolyte, the co-doped carbon foam yields excellent performance, delivering a high specific capacitance of 321 F g−1 at 1 A g−1, a superior energy density of 15.91 W h kg−1 at a power density of 0.4 kW kg−1, and excellent long-term stability, retaining 98% of its initial capacitance after 15 000 cycles at 5 A g−1.

MoO3/C nanocomposites are synthesized by first intercalating alkylamines into layered MoO3 and then in situ carbonization at high temperature. The possible arrangements of alkylamines in the interlayers of MoO3 and the interaction between the inorganic host and the organic guest are discussed. The resulting MoO3/C nanocomposite with a high degree of graphitization exhibits a high specific capacitance of 335 F g−1 at a current density of 1 A g−1 and an excellent rate performance (70% capacitance retained 70% capacitance retained from 1 A g−1 to 10 A g−1). In addition, the obtained nanocomposite can be matched well with expanded graphite to maximize the specific capacitance and also to extend the potential window, giving rise to an increased energy density of the cell. The assembled MoO3/C//expanded graphite asymmetric supercapacitor can be cycled reversibly between 0 and 1.6 V with a specific capacitance of 88 F g−1 at 1 A g−1 and an energy density of 31.3 W h kg−1 at a power density of 838.4 W kg−1. Moreover, this supercapacitor exhibits a good cycling behavior with no more than 13.5% capacitance loss after 5000 cycles at 1 A g−1. The excellent performance is mainly attributed to two aspects. On the one hand, opening up MoO3 layers with conductive carbon can provide more redox sites for Faradaic reaction and promote transportation of electrons. On the other hand, MoO3 and intercalated carbon layers form a sandwich-type hybrid nanostructure, which facilitates the penetration and diffusion of electrolyte ions. This work may pave the way for fabricating active electrode materials for high performance energy storage devices through intercalation and in situ carbonization.

Small molecule solar cells have made great progress in recent years. Herein, we synthesized a novel small molecule donor NDTR with naphtho[1,2-b:5,6-b′]dithiophene (NDT) units as the building blocks. NDTR exhibited complementary absorption for both fullerene acceptor PC71BM and non-fullerene acceptor IDIC. Meanwhile, NDTR possessed a HOMO energy level of −5.23 eV and a LUMO energy level of −3.50 eV, which matched well with these two kinds of acceptors. When mixed with PC71BM, a high power conversion efficiency (PCE) of 7.75% was obtained, while the NDTR:IDIC system presented a PCE of 6.60%. The results indicated that NDTR was an all-round small molecule donor which can work well in both fullerene and non-fullerene systems.

The electrostatic field of a dielectric cavity is powerful for modulating many aspects of confined metal clusters. Here we report that the catalytic properties of Ptn clusters confined in X-zeolite cages are strongly tuned by altering the zeolitic field, which is achieved by using different cations (Na+, Cs+, Ca2+ or La3+) to balance the negative framework of the zeolite. Compared with Ptn@LaX, for example, Ptn@CsX shows a surprising ∼5500% enhancement in TOF value for phenol hydrogenation to cyclohexanol. Electrostatic field modulation leads to gradual changes of electronic properties such as the Fermi levels/d-band centers of the Ptn clusters, as revealed by DFT calculations and experimental characterizations. The decreases in Fermi levels of the Ptn clusters benefit the hydrogenation of –CCH groups (phenylacetylene and acetylene) and –NO2 groups (nitrobenzene, o-nitroanisole and o-chloronitrobenzene) but are detrimental for aromatic ring hydrogenation (phenol). These findings are important for the design of high performance catalysts.

Using nanoparticles (NPs) to catalyze multiple chemical reactions in one-pot and to achieve high-yield syntheses of functional molecules/materials is an important direction in NP chemistry, catalysis and applications. In this article, we report a nanocomposite of AgPd NPs anchored on WO2.72 nanorods (NRs) (denoted as AgPd/WO2.72) as a general catalyst for formic acid dehydrogenation and transfer hydrogenation from Ar-NO2 to Ar-NH2 that further reacts with aldehydes to form benzene-fused heterocyclic compounds. The AgPd/WO2.72 catalysis is Ag/Pd dependent and Ag48Pd52 is the most active composition for the multiple chemical reactions. The high activity of AgPd/WO2.72 arises from strong interfacial interaction between AgPd and WO2.72, resulting in AgPd lattice expansion and electron polarization from AgPd to WO2.72. The syntheses proceed in one-pot reactions among formic acid, 2-nitrophenol (or 2-nitroaniline, or 2-nitrothiophenol) and aldehydes in dioxane/water (2/1 v/v) at 80–90 °C, leading to one-pot syntheses of benzoxazoles, benzimidazoles and benzothiazoles that are key ring structures present in functional compounds for pharmaceutical, optical and polymer applications.

Pairs of electrodes with nanometer gap, termed as nano-gapped electrodes, are fundamental building blocks for the fabrication of nanometer-sized devices and are essential for the examination of molecular properties and extreme nano-optics. Although modern fabrication techniques make it feasible to fabricate nanometer gaps, it is still a formidable challenge to fabricate adjustable gaps arrays with angstrom precision. Here, we demonstrate that in-situ adjustable nanogaps (arrays) with sub-angstrom precision can be fabricated via laser irradiation on the substrate which supports the electrode pairs. We further demonstrate that atomic-level metal contacts can be switched and the direction of the switching can be selectively controlled by the laser irradiation position. By varying the laser power gradually, the nanogap’s size can be continuously changed, providing a reliable break junction technique to address the properties of single-molecule junctions. The small spatial focus size of the laser beam makes it feasible to realize addressable on-chip molecular junction arrays.

We report a facile method for assembly of a monolayer array of nitrogen-doped graphene (NG) and nanoparticles (NPs) and the subsequent transfer of two layers onto a solid substrate (S). Using 3 nm NiPd NPs as an example, we demonstrate that NiPd-NG-Si (Si=silicon wafer) can function as a catalyst and show maximum NiPd catalysis for the hydrolysis of ammonia borane (H3NBH3, AB) with a turnover frequency (TOF) of 4896.8 h−1 and an activation energy (Ea) of 18.8 kJ mol−1. The NiPd-NG-S catalyst is also highly active for catalyzing the transfer hydrogenation from AB to nitro compounds, leading to the green synthesis of quinazolines in water. Our assembly method can be extended to other graphene and NP catalyst materials, providing a new 2D NP catalyst platform for catalyzing multiple reactions in one pot with maximum efficiency.