Showing papers by "Yanshan University published in 2020"

Variable-Temperature Electron Transport and Dipole Polarization Turning Flexible Multifunctional Microsensor beyond Electrical and Optical Energy.

Abstract: Humans are undergoing a fateful transformation focusing on artificial intelligence, quantum information technology, virtual reality, etc., which is inseparable from intelligent nano-micro devices. However, the booming of "Big Data" brings about an even greater challenge by growing electromagnetic radiation. Herein, an innovative flexible multifunctional microsensor is proposed, opening up a new horizon for intelligent devices. It integrates "non-crosstalk" multiple perception and green electromagnetic interference shielding only in one pixel, with satisfactory sensitivity and fast information feedback. Importantly, beneficial by deep insight into the variable-temperature electromagnetic response, the microsensor tactfully transforms the urgent threat of electromagnetic radiation into "wealth," further integrating self-power. This result will refresh researchers' realization of next-generation devices, ushering in a new direction for aerospace engineering, remote sensing, communications, medical treatment, biomimetic robot, prosthetics, etc.

Lithium whisker growth and stress generation in an in situ atomic force microscope–environmental transmission electron microscope set-up

Abstract: Lithium metal is considered the ultimate anode material for future rechargeable batteries1,2, but the development of Li metal-based rechargeable batteries has achieved only limited success due to uncontrollable Li dendrite growth3–7. In a broad class of all-solid-state Li batteries, one approach to suppress Li dendrite growth has been the use of mechanically stiff solid electrolytes8,9. However, Li dendrites still grow through them10,11. Resolving this issue requires a fundamental understanding of the growth and associated electro-chemo-mechanical behaviour of Li dendrites. Here, we report in situ growth observation and stress measurement of individual Li whiskers, the primary Li dendrite morphologies12. We combine an atomic force microscope with an environmental transmission electron microscope in a novel experimental set-up. At room temperature, a submicrometre whisker grows under an applied voltage (overpotential) against the atomic force microscope tip, generating a growth stress up to 130 MPa; this value is substantially higher than the stresses previously reported for bulk13 and micrometre-sized Li14. The measured yield strength of Li whiskers under pure mechanical loading reaches as high as 244 MPa. Our results provide quantitative benchmarks for the design of Li dendrite growth suppression strategies in all-solid-state batteries. Lithium whisker growth and mechanical properties can be studied in situ using a combination of two microscopies.

Platinum single atoms on tin oxide ultrathin films for extremely sensitive gas detection

Abstract: Single atom Pt functionalized SnO2 ultrathin films are synthesized by atomic layer deposition (ALD) for application as sensing layers in resistive gas sensors. Here it is shown that the electronic conductivity of the SnO2 ultrathin films is very sensitive to the exposure to triethylamine (TEA), and that the thickness of the SnO2 films (from 4 to 18 nm) has a crucial effect on the sensor response. The 9 nm thick SnO2 film shows the best response to TEA, while a further decrease in the film thickness, i.e., 4 nm, leads to a very weak response due to the two orders of magnitude lower carrier concentration. Single atom Pt catalysts deposited on the 9 nm SnO2 film result in an unexpectedly high enhancement in the sensor response and also a decrease of the sensor working temperature. Consequently, Pt/SnO2 thin film sensors show the highest response of 136.2 to 10 ppm TEA at an optimal temperature of 200 °C (that of a pristine SnO2 film sensor is 260 °C), which is improved by a factor of 9 compared to that of pristine SnO2. Moreover, the Pt/SnO2 sensor exhibits an ultrahigh sensitivity of 8.76 ppm−1 and an extremely low limit of detection (LOD) of 7 ppb, which to our best knowledge are far superior to any previous report. Very fast response and recovery times (3/6 s) are also recorded, thus making our sensor platform highly suitable for highly-demanding applications. Mechanistic investigations reveal that the outstanding sensing performances originate from the synergistic combination of the optimized film thickness comparable to the Debye length of SnO2 and the spillover activation of oxygen by single atom Pt catalysts, as well as the oxygen vacancies in the SnO2 films.

Multifunctional Antimicrobial Biometallohydrogels Based on Amino Acid Coordinated Self-Assembly.

Abstract: There is a real need for new antibiotics against self-evolving bacteria. One option is to use biofriendly broad-spectrum and mechanically tunable antimicrobial hydrogels that can combat multidrug-resistant microbes. Whilst appealing, there are currently limited options. Herein, broad-spectrum antimicrobial biometallohydrogels based on the self-assembly and local mineralization of Ag+ -coordinated Fmoc-amino acids are reported. Such biometallohydrogels have the advantages of localized delivery and sustained release, reduced drug dosage and toxicity yet improved bioavailability, prolonged drug effect, and tunable mechanical strength. Furthermore, they can directly interact with the cell walls and membrane, resulting in the detachment of the plasma membrane and leakage of the cytoplasm. This leads to cell death, triggering a significant antibacterial effect against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria in cells and mice. This study paves the way for developing a multifunctional integration platform based on simple biomolecules coordinated self-assembly toward a broad range of biomedical applications.

Trilemma assessment of energy intensity, efficiency, and environmental index: evidence from BRICS countries

Abstract: This paper provides an assessment of energy density and energy efficiency and creates an important indicator of environmental performance. This article applied two mathematical models and econometric techniques to obtain detailed and specific results. The DEA and the non-normative account aggregation mean a collective aggregation to form a mathematical aggregation tool to create an environmental index for the BRICS countries (Brazil, Russia, India, China, and South Africa) based on available data from 2011 to 2016. The advantage of the proposed approach is to manage the irregularities of the data and follow the desired properties of the index number. The current paper is relevant for the broad scope of construction, the environmental index, and the evolution of the rankings of countries based on multiple indicators. Our results indicate that Brazil and Russia have the highest values of the Environmental Performance Index, which range between 67.44 and 60.70, respectively. India has a minimum value of 30.57 of the environmental index. The analysis shows that Brazil, Russia, and South Africa have the best scores and that these countries have the best results, while China and India also have the best results. This study can help form a valuable political tool for the development and development of the country's politics.

Single-site pyrrolic-nitrogen-doped sp 2 -hybridized carbon materials and their pseudocapacitance

Abstract: Integrating nitrogen species into sp2-hybridized carbon materials has proved an efficient means to improve their electrochemical performance. Nevertheless, an inevitable mixture of nitrogen species in carbon materials, due to the uncontrolled conversion among different nitrogen configurations involved in synthesizing nitrogen-doped carbon materials, largely retards the precise identification of electrochemically active nitrogen configurations for specific reactions. Here, we report the preparation of single pyrrolic N-doped carbon materials (SPNCMs) with a tunable nitrogen content from 0 to 4.22 at.% based on a strategy of low-temperature dehalogenation-induced and subsequent alkaline-activated pyrolysis of 3-halogenated phenol-3-aminophenol-formaldehyde (X-APF) co-condensed resins. Additionally, considering that the pseudocapacitance of SPNCMs is positively dependent on the pyrrolic nitrogen content, it could be inferred that pyrrolic nitrogen species are highly active pseudocapacitive sites for nitrogen-doped carbon materials. This work gives an ideal model for understanding the contribution of pyrrolic nitrogen species in N-doped carbon materials. A mixture of nitrogen species in carbon materials typically hinders the precise identification of electrochemically active nitrogen configurations for specific reactions. Here the authors show single-site pyrrolic-nitrogen-doped sp2-hybridized carbon materials and their pseudocapacitive properties.

Hierarchically structured diamond composite with exceptional toughness

Abstract: The well known trade-off between hardness and toughness (resistance to fracture) makes simultaneous improvement of both properties challenging, especially in diamond The hardness of diamond can be increased through nanostructuring strategies1,2, among which the formation of high-density nanoscale twins - crystalline regions related by symmetry - also toughens diamond2 In materials other than diamond, there are several other promising approaches to enhancing toughness in addition to nanotwinning3, such as bio-inspired laminated composite toughening4-7, transformation toughening8 and dual-phase toughening9, but there has been little research into such approaches in diamond Here we report the structural characterization of a diamond composite hierarchically assembled with coherently interfaced diamond polytypes (different stacking sequences), interwoven nanotwins and interlocked nanograins The architecture of the composite enhances toughness more than nanotwinning alone, without sacrificing hardness Single-edge notched beam tests yield a toughness up to five times that of synthetic diamond10, even greater than that of magnesium alloys When fracture occurs, a crack propagates through diamond nanotwins of the 3C (cubic) polytype along {111} planes, via a zigzag path As the crack encounters regions of non-3C polytypes, its propagation is diffused into sinuous fractures, with local transformation into 3C diamond near the fracture surfaces Both processes dissipate strain energy, thereby enhancing toughness This work could prove useful in making superhard materials and engineering ceramics By using structural architecture with synergetic effects of hardening and toughening, the trade-off between hardness and toughness may eventually be surmounted

A universal and facile approach to suppress dendrite formation for a Zn and Li metal anode

Abstract: To solve the poor cycling stability of zinc ion batteries (ZIBs) caused by the growth of zinc (Zn) dendrites, a novel method of separator modification is proposed. Herein, graphene oxide (GO), which has many outstanding properties, is applied as a modified material to a glass fiber (GF) separator using a simple vacuum filtration method. A stable and dendrite-free Zn anode can be obtained after 500 cycles in a Zn//Zn symmetrical battery when using a modified separator (GF/GO1), which is mainly owing to the preferential growth of the non-protruding crystal planes of the zinc metal and the uniform nucleation of zinc ions under the action of GO. As proof of concept, full Zn//MnO2 batteries with a GF/GO1 separator exhibited a high specific capacity of 126 mA h g−1 at 0.1 A g−1, a high energy density of 327.5 W h kg−1 (power density of 0.517 W kg−1), and a high power density of 20.8 kW kg−1 (energy density of 253.8 W h kg−1), demonstrating significant improvements compared with the unmodified GF separator. Meanwhile, ZIBs with a GF/GO1 separator exhibited excellent long-term stability with less than 25% capacity fade over 500 cycles at a current density of 0.5 A g−1. ZIBs with a GF separator retain only 37% of their initial capacity after 100 cycles. Furthermore, the GF/GO1 separator can also help to improve the cycle performance and rate performance of lithium metal batteries and to achieve a dendrite-free lithium anode. Full batteries of Li//GF/GO1//LiCoO2 show improved rate and cycling capabilities. A higher energy density of 537.1 W h kg−1 at 0.04 kW kg−1 and higher power density of 1.4 kW kg−1 at 264.6 W h kg−1 can be achieved with a GF/GO1 separator, which is better than many Li metal batteries. This modification of the separator provides an effective approach to designing next-generation batteries exhibiting excellent rate and cycling capabilities, and high energy and power densities.

Vanadium-Based Oxide on Two-Dimensional Vanadium Carbide MXene (V2Ox@V2CTx) as Cathode for Rechargeable Aqueous Zinc-Ion Batteries

Abstract: Rechargeable aqueous zinc-ion batteries (AZIBs) are considered for emerging cutting-edge energy storage technologies as an alternative to the existing nonaqueous lithium-ion batteries (LIBs) owing ...

Facile preparation of self-assembled MXene@Au@CdS nanocomposite with enhanced photocatalytic hydrogen production activity

Abstract: Photocatalytic hydrogen production is considered a promising approach to generating clean sustainable energy. However, the conventional co-catalyst (e.g., Pt) used in photocatalytic hydrogen production is high-cost and difficult to obtain. Here, we designed and prepared a ternary nanocomposite MXene@Au@CdS, which can be used in the field of efficient and excellent photocatalytic hydrogen production. The MXene@Au@CdS has a hydrogen production rate of 17,070.43 μmol g−1 h−1 (tested for 2 h), which is 1.85 times that of pure CdS nanomaterials. The improved hydrogen production performance of the MXene@Au@CdS is attributed to: (i) MXene provides more active adsorption sites and reaction centers for Au and CdS nanoparticles; (ii) the synergistic effect of Au’s strong surface plasmon resonance expands the optical response range of CdS. Therefore, this work solves the problem of the solid connection between the surface functional groups of photocatalyst, and achieves rapid interface charge transfer and long-term stability during the hydrogen production.

NiMn Layered Double Hydroxide Nanosheets In-situ Anchored on Ti3C2 MXene via Chemical Bonds for Superior Supercapacitors

Abstract: The poor conductivity, unsatisfactory stability, and severe aggregation of nanosheets have been recognized as the main reasons that limit the electrochemical performance of layered double hydroxide...

Facile Preparation of Self-Assembled Black Phosphorus-Dye Composite Films for Chemical Gas Sensors and Surface-Enhanced Raman Scattering Performances

Abstract: The research studies on the functionalization of two-dimensional (2D) materials (such as black phosphorus) are essential for the development of self-assembled nanomaterials. In this work, the compo...

The role of fixed capital formation, renewable and non-renewable energy in economic growth and carbon emission: a case study of Belt and Road Initiative project

Abstract: Economic integration in the form of Belt and Road Initiative project opens many opportunities and hazards, especially of the participating nations’ environment. The current study attempted to empirically test the economic and energy usage (renewable and non-renewable) impact on some selected countries of belt and road projects. For this purpose, the panel data set of twenty-four emerging economies of belt and road projects was selected from 1995 to 2014. The autoregressive distributed lags technique of econometric applied to determine the effect of renewable and non-renewable energy, GDP and GDP2 for EKC, and gross fixed capital formation on carbon emission in the selected countries of Belt and Road Initiative project. The outcomes of this study confirm the existence of EKC in these underlined countries. Here, fossil fuel-based energy consumption is a source of environmental degradation, while renewable and clean energy usage can help sustain environmental conditions without affecting economic growth progress. Capital fixed formation in these economies can enhance economic growth and help to sustainable environmental conditions in the belt and road countries. Thus, based on these empirical outcomes, this study suggests economic and financial assistance in green renewable energy sources and clean technological innovation to enhance economic benefits of Belt and Road Initiative project without compromising the environmental conditions of the region.

Atomically Dispersed Co Catalyst for Efficient Hydrodeoxygenationof Lignin-Derived Species and Hydrogenation of Nitroaromatics

Abstract: Single-atom catalysts (SACs) have attracted much attention due to their outstanding catalytic performance in heterogeneous catalysis. Here, we report a template sacrificial method to fabricate an a...