A high-performance C@Na5V12O32 nanowire electrode derived from the reconstruction of carbon quantum dots.

Vanadate electrodes are potential candidates for lithium-ion batteries (LIBs) due to their large theoretical specific capacity. However, their easy dissolution in the electrolyte, large structural changes, low conductivity and capacity decay during cycling hinder their further application. Herein, a lithium-ion battery electrode of Na5V12O32 (NVO) nanowires covered with a carbon film and formed by the reconstruction of carbon quantum dots (CDs) was obtained using an in situ capping strategy. Remarkably, the carbon film could prevent direct contact between the NVO nanowires and the electrolyte, thus slowing down the occurrence of side reactions and avoiding the dissolution of the NVO nanowires. Among the electrodes treated at different temperatures, the C@NVO-400 electrode exhibits high capacity and excellent cycling stability as the electrode of LIBs, with a discharge specific capacity of 779.1 and 315.5 mAh g-1 after 400 and 1000 cycles at a current density of 0.1 and 2 A g-1, respectively. An in situ coating strategy is proposed here to contribute to the further development of coated vanadate electrodes for high-performance LIBs.

Fluorescence sensor based on optimized quantum yield manganese-carbon polymer dots and smartphone-integrated sensing platform for tetracycline detection.

The one-step synthesis of Mn-doped carbon quantum dots (Mn-CPDs) with a high quantum yield (QY = 45%) is reported using the microwave-assisted method. Subsequently, Mn-CPDs were successfully combined with Eu3+ ions to construct an Eu3+@Mn-CPDs fluorescence sensor. The presence of tetracycline (TC) induced a transition of fluorescence emission from blue (434 nm) to red (618 nm), and a robust linear relationship was observed between the ratio of F618 nm / F434 nm and the TC concentration (5 - 50 nmol/L), with a limit of detection (LOD) of 5.76 nmol/L. The underlying mechanism of Eu3+@Mn-CPDs and TC sensing is unveiled as a synergistic effect involving inner filter effect (IFE) and concurrent interactions. Notably, the smartphone-integrated sensing platform based on Eu3+@Mn-CPDs enables rapid and quantitative TC detection within a short time (< 30 s) by monitoring fluorescence color changes, achieving high-detection sensitivities (with a LOD of 6.18 nmol/L). This versatile and efficient sensing platform demonstrates its potential for the determination of TC concentrations in milk, honey, and tap water samples.

Stabilizing Top Interface by Molecular Locking Strategy with Polydentate Chelating Biomaterials toward Efficient and Stable Perovskite Solar Cells in Ambient Air.

The instability of top interface induced by interfacial defects and residual tensile strain hinders the realization of long-term stable n-i-p regular perovskite solar cells (PSCs). Herein, one molecular locking strategy is reported to stabilize top interface by adopting polydentate ligand green biomaterial 2-deoxy-2,2-difluoro-d-erythro-pentafuranous-1-ulose-3,5-dibenzoate (DDPUD) to manipulate the surface and grain boundaries of perovskite films. Both experimental and theoretical evidence collectively uncover that the uncoordinated Pb2+ ions, halide vacancy, and/or I─Pb antisite defects can be effectively healed and locked by firm chemical anchoring on the surface of perovskite films. The ingenious polydentate ligand chelating is translated into reduced interfacial defects, increased carrier lifetimes, released interfacial stress, and enhanced moisture resistance, which should be liable for strengthened top interface stability and inhibited interfacial nonradiative recombination. The universality of the molecular locking strategy is certified by employing different perovskite compositions. The DDPUD modification achieves an enhanced power conversion efficiency (PCE) of 23.17-24.47%, which is one of the highest PCEs ever reported for the devices prepared in ambient air. The unsealed DDPUD-modified devices maintain 98.18% and 88.10% of their initial PCEs after more than 3000 h under a relative humidity of 10-20% and after 1728 h at 65 °C, respectively.

Polydentate Ligand Reinforced Chelating to Stabilize Buried Interface toward High-Performance Perovskite Solar Cells.

The instability of the buried interface poses a serious challenge for commercializing perovskite photovoltaic technology. Herein, we report a polydentate ligand reinforced chelating strategy to strengthen the stability of buried interface by managing interfacial defects and stress. The bis(2,2,2-trifluoroethyl) (methoxycarbonylmethyl)phosphonate (BTP) is employed to manipulate the buried interface. The C=O, P=O and two -CF3 functional groups in BTP synergistically passivate the defects from the surface of SnO2 and the bottom surface of the perovskite layer. Moreover, The BTP modification contributes to mitigated interfacial residual tensile stress, promoted perovskite crystallization, and reduced interfacial energy barrier. The multidentate ligand modulation strategy is appropriate for different perovskite compositions. Due to much reduced nonradiative recombination and heightened interface contact, the device with BTP yields a promising power conversion efficiency (PCE) of 24.63 %, which is one of the highest efficiencies ever reported for devices fabricated in the air environment. The unencapsulated BTP-modified devices degrade to 98.6 % and 84.2 % of their initial PCE values after over 3000 h of aging in the ambient environment and after 1728 h of thermal stress, respectively. This work provides insights into strengthening the stability of the buried interface by engineering multidentate chelating ligand molecules.

Photo-thermal synergistic excitation: Feasible strategy to detect ethanol for wide bandgap ZIF-8 at low work temperature.

Zeolitic Imidazolate Framework-8 (ZIF-8) material was prepared by chemical precipitation method. The microstructure and physical properties of the as-prepared samples were characterized by XRD, BET, FESEM and UV spectrophotometer. The self-made four-channel measurement device was used to test the gas sensitivity of ZIF-8 material toward ethanol gas under photo-thermal synergistic excitation. The results showed that the sample was typical ZIF-8 (Eg = 4.96 eV) with a regular dodecahedron shape and the specific surface is up to 1793 m2/g. The as-prepared ZIF-8 has a gas response value of 55.04 to 100 ppm ethanol at 75°C and it shows good gas sensing selectivity and repeated stability. The excellent gas sensitivity can be attributed to the increase of free electron concentration in the ZIF-8 conduction band by photo-thermal synergistic excitation, and the large specific surface area of ZIF-8 material provides more active sites for gas-solid surface reaction. The reaction mechanism of ZIF-8 material under multi-field excitation was also discussed.

P-doping boosting electronic properties and ionic kinetics of MnV2O6 for high-performance lithium-ion batteries.

Vanadate electrodes are potential candidates for lithium-ion batteries (LIBs) due to their large theoretical specific capacity. However, their practical application suffers from limitations of poor conductivity, inferior ion kinetics, and severe volume changes upon cycling. Herein, a doping strategy is realized to prepare phosphorus (P)-doped MnV2O6 (PMVO) nanosheets to enhance the electrochemical activity and structural stability. On combining experimental and computation results, it is found that the PMVO structure enhances the electrical conductivity, reduces the adsorption energy of lithium ions, increases the structural stability, and facilitates rapid surface diffusion kinetics. As expected, the desirable electrode of PMVO delivers a reversible capacity of 812.7 mA h g-1 at 200 mA g-1 and shows excellent coulombic efficiency, as well as an extraordinary energy density of 472.1 W h kg-1. Meanwhile, an excellent rate performance (from 0.1 to 5.0 and return to 0.1 A g-1; 779.6 to 319.6 and return to 811.9 mA h g-1) could be achieved. The strategy proposed here may aid in further development of doped vanadate electrodes for high-performance LIBs.

Boosting the Cell Performance of the SiO/Cu and SiO/PPy Anodes via In-Situ Reduction/Oxidation Coating Strategies.

Silicon monoxide (SiO) has attracted great attention due to its high theoretical specific capacity as an alternative material for conventional graphite anode, but its poor electrical conductivity and irreversible side reactions at the SiO/electrolyte interface seriously reduce its cycling stability. Here, to overcome the drawbacks, the dicharged SiO anode coated with Cu coating layer is elaborately designed by in-situ reduction method. Compared with the pristine SiO anode of lithium-ion battery (293 mAh g-1 at 0.5 A g-1 after 200 cycles), the obtained SiO/Cu composite presents superior cycling stability (1206 mAh g-1 at 0.5 A g-1 after 200 cycles). The tight combination of Cu particles and SiO significantly improves the conductivity of the composite, effectively inhibits the side-reaction between the active material and electrolyte. In addition, polypyrrole-coated SiO composites are further prepared by in-situ oxidation method, which delivers a high reversible specific capacity of 1311 mAh g-1 at 0.5 A g-1 after 200 cycles. The in-situ coating strategies in this work provide a new pathway for the development and practical application of high-performance silicon-based anode.

Synthesis of high quantum yield rhenium-doped carbonized polymer dots for dual sensing of Fe3+ and Mo6+ and anti-counterfeit ink applications.

The bottom-up approach serves as an efficacious and noteworthy method for the synthesis of carbonized polymer dots (CPDs). In the present investigation, rhenium-doped CPDs (Re-CPDs) were successfully synthesized via a hydrothermal technique employing citric acid, urea, and NH4ReO4. Subsequent to a comprehensive series of characterizations, Re-CPDs demonstrated an average particle size of 2.67 nm, excitation/emission maxima of 377/461 nm, and an elevated quantum yield of 45.36% at 377 nm excitation. Through the selectivity analysis involving various metal ions, Re-CPDs displayed sensitivity towards Fe3+ and Mo6+ ions, with limits of detection (LODs) of 0.02 µM and 0.48 µM, respectively. Furthermore, Re-CPDs exhibited multi-chromatic fluorescence (450-550 nm) under excitation wavelengths (375-430 nm). As a result, by amalgamating Re-CPDs with sucrose, detection patterns capable of generating multi-chromatic fluorescence at excitation wavelengths of 375, 395, and 430 nm, respectively, were successfully devised. In summary, Re-CPDs hold considerable potential as a material for the detection of Fe3+ and Mo6+ ions, as well as for anti-counterfeiting ink applications.

Effects of In-Situ Reaction, Extrusion Ratio and CeO2 on the Performance of Al-Ti-C-(Ce) Grain Refiners for Refining Pure Aluminum Grains.

Al-Ti-C-(Ce) grain refiners were prepared by combining in-situ reaction, hot extrusion, and adding CeO2. The effects of second phase TiC particle size and distribution, extrusion ratio, and Ce addition on the grain-refining performance of grain refiners were investigated. The results show that about 10 nm TiC particles are dispersed on the surface and inside of 100-200 nm Ti particles by in-situ reaction. The Al-Ti-C grain refiners, which are made, by hot extrusion, of a mixture of in-situ reaction Ti/TiC composite powder and Al powder, increase the effective nucleation phase of α-Al and hinder grain growth due to the fine and dispersed TiC; this results in the average size of pure aluminum grains to decrease from 1912.4 µm to 504.8 µm (adding 1 wt.% Al-Ti-C grain refiner). Additionally, with the increase of the extrusion ratio from 13 to 30, the average size of pure aluminum grains decreases further to 470.8 µm. This is because the micropores in the matrix of grain refiners are reduced, and the nano-TiC aggregates are dispersed with the fragmentation of Ti particles, resulting in a sufficient Al-Ti reaction and an enhanced nucleation effect of nano-TiC. Furthermore, Al-Ti-C-Ce grain refiners were prepared by adding CeO2. Under the conditions of holding for 3-5 min and adding a 5.5 wt.% Al-Ti-C-Ce grain refiner, the average size of pure aluminum grains is reduced to 48.4-48.8 µm. The reason for the excellent grain-refining and good anti-fading performance of the Al-Ti-C-Ce grain refiner is presumedly related to the Ti2Al20Ce rare earth phases and [Ce] atoms, which hinder agglomeration, precipitation, and dissolution of the TiC and TiAl3 particles.

A Study of Silver Decoration on Carbon Nanotubes via Ultrasonic Chemical Synthesis and Their Reinforced Copper Matrix Composites.

The homogeneous distribution of carbon nanotubes (CNTs) in the Cu matrix and good interfacial bonding are the key factors to obtain excellent properties of carbon nanotube-reinforced Cu-based composites (CNT/Cu). In this work, silver-modified carbon nanotubes (Ag-CNTs) were prepared by a simple, efficient and reducer-free method (ultrasonic chemical synthesis), and Ag-CNTs-reinforced copper matrix composites (Ag-CNTs/Cu) were fabricated by powder metallurgy. The dispersion and interfacial bonding of CNTs were effectively improved by Ag modification. Compared to CNTs/Cu counterparts, the properties of Ag-CNTs/Cu samples were significantly improved, with the electrical conductivity of 94.9% IACS (International Annealed Copper Standard), thermal conductivity of 416 W/m·k and tensile strength (315 MPa). The strengthening mechanisms are also discussed.

Visualization of X-rays with an Ultralow Detection Limit via Zero-Dimensional Perovskite Scintillators.

X-rays play an extremely significant role in medical diagnosis, safety testing, scientific research, and other practical applications. However, as the main sources of radioactive pollution, the hazard of X-rays to human health and the environment has been a major concern. Herein, the explored perovskite scintillator of Cs2Zr1-xPbxCl6 in this work exhibits an ultrahigh radioluminescence intensity owing to the enhanced X-ray absorption for the introduction of Pb2+ ions. The Cs2Zr1-xPbxCl6 crystals are demonstrated as efficient scintillators with a self-trapped exciton emission and extremely high steady-state light yield (∼101,944 photons meV-1). This fascinating scintillator provides a convenient visual tool for X-ray detection even for an indoor lighting environment, reaching a low detection limit of ∼14.2 nGy·s-1, which is about 1/387 of the typical medical imaging dose (5.5 µGy·s-1). Moreover, X-ray imaging with a high resolution of 16.6 lp·mm-1 is achieved with the as-explored Cs2Zr1-xPbxCl6 scintillator film. Herein, the Cs2Zr1-xPbxCl6 scintillator provides a feasible strategy for X-ray monitoring in the field of biomedicine, high-energy physics, national security, and other applications.

Aging Interfacial Structure and Abnormal Tensile Strength of SnAg3Cu0.5/Cu Solder Joints.

In this study, the interfacial structure and abnormal long-term increase of tensile strength in the interfacial intermetallic compounds (IMCs) between SnAg3Cu0.5 solder and Cu substrates during isothermal aging were investigated. After reflow soldering, the IMC layer at the interface was thin and scallop-type. The interfacial layer became thicker with the increase in aging time. After 200 h of aging at 150 °C, the thickness of the interface gradually increased to 3.93 µm and the interface became smooth. Compared with the unaged Cu-Sn interface, the aged joint interface contained more Cu3Sn. The top of the IMC being reflown was relatively smooth, but became denser and prismatic in shape after 200 h of aging at 150 °C. The tensile strength of the joint, immediately after the reflow, reached 81.93 MPa. The tensile properties of the solder joints weakened and then strengthened as they aged. After 200 h of aging at 150 °C, the tensile strength was 83.86 MPa, which exceeded that of the unaged solder joint interface, because the fracture mode of the solder joints changed during aging.

Recent advances in biomimetic soft robotics: fabrication approaches, driven strategies and applications.

Compared to traditional rigid-bodied robots, soft robots are constructed using physically flexible/elastic bodies and electronics to mimic nature and enable novel applications in industry, healthcare, aviation, military, etc. Recently, the fabrication of robots on soft matter with great flexibility and compliance has enabled smooth and sophisticated 'multi-degree-of-freedom' 3D actuation to seamlessly interact with humans, other organisms and non-idealized environments in a highly complex and controllable manner. Herein, we summarize the fabrication approaches, driving strategies, novel applications, and future trends of soft robots. Firstly, we introduce the different fabrication approaches to prepare soft robots and compare and systematically discuss their advantages and disadvantages. Then, we present the actuator-based and material-based driving strategies of soft robotics and their characteristics. The representative applications of soft robotics in artificial intelligence, medicine, sensors, and engineering are summarized. Also, some remaining challenges and future perspectives in soft robotics are provided. This work highlights the recent advances of soft robotics in terms of functional material selection, structure design, control strategies and biomimicry, providing useful insights into the development of next-generation functional soft robotics.

Interfacial Bonding Improvement through Nickel Decoration on Carbon Nanotubes in Carbon Nanotubes/Cu Composite Foams Reinforced Copper Matrix Composites.

Inhomogeneous structures with carbon nanotubes (CNTs), reinforced with Cu composite foams as the reinforcing skeletons (CNTs/Cuf®Cu), have been designed to overcome the paradox between strength and ductility or conductivity in copper matrix composites. The interface between CNTs and the copper matrix is usually weak, due to poor wettability and interaction. In this study, nickel nanoparticles are decorated onto CNTs to improve interfacial bonding. The broader interface transition area between CNTs and copper with Ni3C interfacial products formed, and a combination of improved electrical conductivity (95.6% IACS), tensile strength (364.9 MPa), and elongation (40.6%) was achieved for the Ni-decorated CNTs/Cuf®Cu (Ni-CNTs/Cuf®Cu). In addition, the strengthening mechanisms are discussed in this study.

Manipulating the Water Dissociation Electrocatalytic Sites of Bimetallic Nickel-Based Alloys for Highly Efficient Alkaline Hydrogen Evolution.

Transition-metal alloys are currently drawing increasing attention as promising electrocatalysts for the alkaline hydrogen evolution reaction (HER). However, traditional density-functional-theory-derived d-band theory fails to describe the hydrogen adsorption energy (ΔGH ) on hollow sites. Herein, by studying the ΔGH for a series of Ni-M (M=Ti, V, Cr, Mn, Fe, Co, Cu, Zn, Mo, W) bimetallic alloys, an improved d-band center was provided and a potential NiCu electrocatalyst with a near-optimal ΔGH was discovered. Moreover, oxygen atoms were introduced into Ni-M (O-NiM) to balance the adsorption/desorption of hydroxyl species. The tailored electrocatalytic sites for water dissociation can synergistically accelerate the multi-step alkaline HER. The prepared O-NiCu shows the optimum HER activity with a low overpotential of 23 mV at 10 mA cm-2 . This work not only broadens the applicability of d-band theory, but also provides crucial understanding for designing efficient HER electrocatalysts.

A Combination of Enhanced Mechanical and Electromagnetic Shielding Properties of Carbon Nanotubes Reinforced Cu-Ni Composite Foams.

Carbon nanotubes (CNTs) reinforced double-layered Cu-Ni composite foams (Cu-Ni/CNT foams) were prepared through chemical plating and electrodeposition, for the purpose of combining enhanced mechanical and electromagnetic shielding properties. The microstructure characterization revealed a quite uniform dispersion of the CNTs embedded in the metal layers, even after heat treatments. The property testing showed the compressive strength, energy absorption capacity and electromagnetic shielding effectiveness (SE) of Cu-Ni/CNTs foams were significantly improved, as compared to Cu-Ni foams. The heat treatments of the composite foams resulted in an interdiffusion of the Cu and Ni layers, causing an increase of compressive strength and a slight decrease of average SE. The possible mechanisms of the property evolution are discussed.

A Highly Stable Photodetector Based on a Lead-Free Double Perovskite Operating at Different Temperatures.

In recent years, considerable breakthroughs have been achieved in the explored photodetectors with improved performance and stability. However, such devices suffer from the drifting parameters (photoresponsivity, response time, and specific detectivity) in the case of evident operating temperature changes. Here, a double perovskite Cs2NaBiCl6-based ultraviolet (UV) photodetector is developed free from thermal disturbance, exhibiting a steady photoresponsivity (≈ 67.98 mA/W) and response time (≈ 16.42 ms) within a wide temperature range (from 273 to 333 K). Further studies demonstrate that the stability of the crystal structure endows the superior photodetection capability. This result unambiguously highlights the great potential of such double perovskite Cs2NaBiCl6 compound as an environmentally friendly alternative for UV photodetectors.

Plant tissue imaging with bipyramidal upconversion nanocrystals by introducing Tm3+ ions as energy trapping centers.

Plant cell imaging is critical for agricultural production and plant pathology study. Advanced upconversion nanoparticles (UCNPs) are being developed as fluorescent probes for imaging cells and tissues in vivo and in vitro. Unfortunately, the thick cellulosic walls as barriers together with hemicelluloses and pectin hinder the entrance of macromolecules into the epidermal plant cell. Hence, realizing satisfactory temporal and spatial resolution with UCNPs remains an arduous task. Here, bipyramidal LiErF4:1%Tm3+@LiYF4 core-shell UCNPs with a super-bright red emission upon 980 nm laser excitation are explored, where the introduction of Tm3+ ions permits alleviation of the energy loss at defective sites and a significant improvement of the upconversion output. The as-obtained bipyramidal UCNPs could readily puncture plant cell walls and further penetrate into cell membranes, facilitating improved tissue imaging of cellular internalization, as demonstrated with the luminescence images obtained by multiphoton laser-scanning microscopy. Hence our work opens up a new avenue for exploring effective upconversion nanoparticles for achieving high resolution imaging of plant tissues.

Simultaneous achievement of high strength and high ductility in copper matrix composites with carbon nanotubes/Cu composite foams as reinforcing skeletons.

Copper matrix composites reinforced by copper foams with uniformly embedded carbon nanotubes (CNTs) were prepared by electrodeposition and spark plasma sintering (SPS). The microstructure and mechanical properties of the composite foams and bulk composites were characterized or tested by Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and tensile tester, respectively. The results show that the CNTs are uniformly dispersed and embedded in the copper foams by electrodeposition, which preserve as reinforcing skeletons in the subsequent SPS sintered composites. Significant improvements of the tensile strength up to 341.32 MPa and the elongation value of 35.59% are obtained for the CNTs/Cu foam reinforced copper composites, showing a simultaneous achievement of high strength and high ductility with such a three-dimensional skeleton reinforced composite structure. The strengthening mechanisms are also discussed.

A Comparison Study of Ag Composites Prepared by Spark Plasma Sintering and Hot Pressing with Silver-Coated CNTs as the Reinforcements.

In this study, carbon nanotube-reinforced silver composites (CNT/Ag) were prepared by the powder metallurgy process via spark plasma sintering (SPS) and hot pressing sintering (HP) with composite powders through an improved electroless plating method assisted by ultrasonic spray atomization. The dispersion of CNTs was effectively improved by ultrasonic spray atomization, and uniform silver layers were deposited on the surface of CNTs by electroless deposition. The property testing results showed significant improvements of the electrical conductivity, hardness, and tensile strength in the samples prepared by SPS, as compared to their HP sintered counterparts. When the volume fraction of CNTs reached 2.5%, the tensile strength reached a maximum value of 221 MPa, which was more than twice that of the pure silver samples. The structural analysis indicated different degrees of CNT agglomeration and matrix mean grain sizes in the composites prepared by SPS and HP, which are responsible for the differences in properties.