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The rapid development of flexible triboelectric nanogenerators (TENGs) has become an alternative to batteries for wearable devices. Stretchable, multifunctional, and low-cost are the primary development directions for these wearable devices based on TENG. Herein, a stretchable triboelectric generator with coplanar integration was designed for energy harvesting and force sensing. The industrial conductive silicone and silicone were used to fabricate the TENG with a thickness of less than 0.9 mm. When the elongation was less than 150%, TENG exhibited excellent linear characteristics in the resistance-tensile strain correspondence, and the coefficient of determination was 0.99. This stretchable TENG with a sufficient contact area of 9 cm2 could generate a short-circuit current of 2 µA when it was in contact with the skin. Lastly, an intelligent tension monitoring wearable device that can effectively measure the tensile force was developed. Such a stretchable, coplanar integration-based, and low-cost wearable device has excellent applicability in wearable electronics.

Photothermal therapy (PTT) has inherent advantages in the treatment of hypoxic tumors due to its optically controlled selectivity on tumor ablation and oxygen-independent nature. The subcellular organelle-targeting capability and photothermal conversion efficiency (PCE) at near-infrared (NIR) wavelength are the key parameters in the assessment of the photothermal agent (PTA). Here, we report that carbon dots (CDs) prepared by the hydrothermal treatment of coronene derivatives show a high PCE of 54.7% at 808 nm, which can be attributed to the narrow band gap and the presence of amounts of continuous energy bands on CDs. Moreover, the vibrations in the layered graphite structures of the CDs also increase the rate of nonradiative transition and thus enhance the PCE. Furthermore, the CDs also possess excellent photostability, biocompatibility, and cell penetration capability and could mainly accumulate in the lysosomes. These experiment results have proved that the CDs are suitable as an efficient NIR light-triggered PTA for efficient PTT against cancer.

Owing to the storage and transportation problems of hydrogen fuel, exploring new methods of the real-time hydrogen production from ammonia becomes attractive. In this paper, non-thermal arc plasma (NTAP) combining with NiO/Al2O3 catalyst is developed to produce hydrogen from ammonia with high efficiency and large scale. The effects of ammonia gas flow rate and discharge power on the gas temperature, electron density, the hydrogen production rate, and energy efficiency were investigated. Experimental results show that the optical emission spectrum of NTAP working with pure ammonia medium was dominated by the atom spectrum of H α , H β , and molecular spectrum of NH component. Under the optimum experimental condition of plasma discharge, the highest energy efficiency of hydrogen production reached 783.4 L/kW ⋅ h at NH3 gas flow rate of 30 SLM. When the catalyst was added, and heated by the NTAP simultaneously, the energy efficiency further increased to 1080.0 L/kW ⋅ h.

Non-noble-metal-based electrocatalysts with superior oxygen reduction reaction (ORR) activity to platinum (Pt) are highly desirable but their fabrications are challenging and thus impeding their applications in metal-air batteries and fuel cells. Here, we report a facile molten salt assisted two-step pyrolysis strategy to construct carbon nanosheets matrix with uniformly dispersed Fe3N/Fe nanoparticles and abundant nitrogen-coordinated Fe single atom moieties (Fe@FeSA-N-C). Thermal exfoliation and etching effect of molten salt contribute to the formation of carbon nanosheets with high porosity, large surface area and abundant uniformly immobilized active sites. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) image, X-ray absorption fine spectroscopy, and X-ray photoelectron spectroscopy indicate the generation of Fe (mainly Fe3N/Fe) and FeSA-N-C moieties, which account for the catalytic activity for ORR. Further study on modulating the crystal structure and composition of Fe3N/Fe nanoparticles reveals that proper chemical environment of Fe in Fe3N/Fe notably optimizes the ORR activity. Consequently, the presence of abundant FeSA-N-C moieties, and potential synergies of Fe3N/Fe nanoparticles and carbon shells, markedly promote the reaction kinetics. The as-developed Fe@FeSA-N-C-900 electrocatalyst displays superior ORR performance with a half-wave potential (E1/2) of 0.83 V versus reversible hydrogen electrode (RHE) and a diffusion limited current density of 5.6 mA cm−2. In addition, a rechargeable Zn-air battery device assembled by the Fe@FeSA-N-C-900 possesses remarkably stable performance with a small voltage gap without obvious voltage loss after 500 h of operation. The facile synthesis strategy for the high-performance composites represents another viable avenue to stable and low-cost electrocatalysts for ORR catalysis.

A mathematical model is necessary to analyze sensor performance and optimize its design. However, most of the existing models of piezoelectric micro-machined hydrophones are incomplete and too complex to understand. There has been no mathematical model for the sensitivity of piezoelectric hydrophones. To address this shortcoming, this paper proposes a mathematical model of a piezoelectric micro-machined hydrophone. The stresses in the piezoelectric layer and static displacement of the diaphragm under uniform sound pressure are derived. In addition, the resonant frequency and sensitivity of the hydrophone are analyzed. The finite element simulation is used to verify the validity of the proposed mathematical model. On the basis of the mathematical model and simulation, the diaphragm radius, top electrode area, and piezoelectric film thickness are optimized. Furthermore, the hydrophone is fabricated, and its morphology is observed. The impedance-frequency spectrum of the hydrophone is measured by HIOKI IM3536 LCR impedance analyzer. The tested resonant frequency is 0.5 MHz, which is relatively close to the calculated result of 0.537 MHz, so the validity of the proposed mathematical model is further validated. Also, the reason why the test result is less than the calculated result is explained. The effective electromechanical coupling coefficient derived from the impedance curve is 7.5%. The developed mathematical model can provide a useful guide for designing high performance piezoelectric micromachined hydrophone and make preliminary predictions of its characteristics.

Owing to the high theoretical capacity, metal sulfides have emerged as promising anode materials for potassium-ion batteries (PIBs). However, sluggish kinetics, drastic volume expansion, and polysulfide dissolution during charge/discharge result in unsatisfactory electrochemical performance. Herein, we design a core-shell structure consisting of an active bismuth sulfide core and a highly conductive sulfur-doped carbon shell (Bi2S3@SC) as a novel anode material for PIBs. Benefiting from its unique core-shell structure, this Bi2S3@SC is endowed with outstanding potassium storage performance with high specific capacity (626 mAh·g−1 under 50 mA·g−1) and excellent rate capability (268.9 mAh·g−1 at 1 A·g−1). More importantly, a Bi2S3@SC//KFe[Fe(CN)6] full cell is successfully fabricated, which achieves a high reversible capacity of 257 mAh·g−1 at 50 mA·g−1 over 50 cycles, holding great potentials in practical applications. Density functional theory (DFT) calculations reveal that potassium ions have a low diffusion barrier of 0.54 eV in Bi2S3 due to the weak van der Waals interactions between layers. This work heralds a promising strategy in the structural design of high-performance anode materials for PIBs.

Direct alcohol fuel cells represent a promising green and sustainable route for chemical to electrical energy conversion; however, designing highly efficient electrocatalysts for the electro-oxidat...

The development of wireless monitoring is currently restricted by the short lifetime of batteries, requiring frequent replacement. Utilization of abundant mechanical energy from the surrounding environment has attracted increasing attention in real-time monitoring. Herein, a coil-levitated hybrid generator was developed for the efficient harvesting of mechanical energy from mechanical motion. The novel coil-levitated structure adapted to the metal and magnetic environment. The output currents were systematically analyzed at different operation modes based on the unique combination of triboelectrification, electromagnetic induction, and piezoelectric effect. Under the excitation of vibration frequency and amplitude of 8 Hz and 5 mm respectively, the as-constructed triboelectric nanogenerator delivered a peak power density of 11.40 W/m3 at 10 MΩ. Meanwhile, the middle electromagnetic part and bottom piezoelectric generator provided peak power densities of 6.97 and 79.93 W/m2 at 10000 Ω, respectively. More importantly, the battery charging experiment was verified, in which a 30 mA h Li-ion battery can be charged from 2.57 to 3.27 V in about 90 min. In sum, a self-powered temperature and vibration monitoring system was successfully developed based on hybrid generator, promising for realizing wireless monitoring of mechanical equipment without any external power supply.

Microwave (MW) antenna is a key element in microwave ablation (MWA) treatments as the means that energy is delivered in a focused manner to the tumor and its surrounding area. The energy delivered results in a rise in temperature to a lethal level, resulting in cell death in the ablation zone. The delivery of energy and hence the success of MWA is closely dependent on the structure of the antennas. Therefore, three design criteria, such as expected ablation zone pattern, efficiency of energy delivery, and minimization of the diameter of the antennas have been the focus along the evolution of the MW antenna. To further improve the performance of MWA in the treatment of various tumors through inventing novel antennas, this article reviews the state-of-the-art and summarizes the development of MW antenna designs regarding the three design criteria.

The development of graphene oxide/rare earth complexes luminescent materials is limited due to the strong quenching ability of graphene oxide. However, the hybrid materials with pyromellitic acid (PMA) as ligand not only have better performance, but also have stronger luminescence intensity. Herein we tested the effect of the carboxylic acid structure of PMA on the luminescence intensity of graphene oxide/rare earth complexes hybrid materials. Phthalic acid (PA), Isophthalic acid (i-PA) and Terephthalic acid (p-PA) are selected as test ligand, representing the o-position, meta-position and para-position effects of PMA. By comparing the luminescence intensity, we found that o-position effect is helpful for the ligand to sensitize rare earth ions, and meta-position and para-position effects are helpful for the graphene oxide sheets (GOSs) to improve the luminescence intensity of hybrid materials and inhibit the quenching effect of the GOSs. Furthermore, we speculate on the relationship between the distance of π-π stacking of GOSs and rare earth complexes and luminescence intensity of hybrid materials. This work provides an important reference for the design of graphene oxide/rare-earth aromatic carboxylic acid hybrid luminescent materials.

Electrocatalytic CO2 reduction reaction is regarded as an intriguing route for producing renewable chemicals and fuels, but its development is limited by the lack of highly efficient and stable electrocatalysts. Herein, we propose the pipet-like bismuth (Bi) nanorods semifilled in nitrogen-doped carbon nanotubes (Bi-NRs@NCNTs) for highly selective electrocatalytic CO2 reduction. Benefited from the prominent capillary and confinement effects, the Bi-NRs@NCNTs act as nanoscale conveyors that can significantly facilitate the mass transport, adsorption,and concentration of reactants onto the active sites, realizing rapid reaction kinetics and low cathodic polarization. The spatial encapsulation and separation by the NCNT shells prevents the self-aggregation and surface oxidation of Bi-NRs, increasing the dispersity and stability of the electrocatalyst. As a result, the Bi-NRs@NCNTs exhibit high activity and durable catalytic stability for CO2-to-formate conversion over a wide potential range. The Faradaic efficiency for formate production reaches 90.9% at a moderate applied potential of -0.9 V vs reversible hydrogen electrode (RHE).

Catalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) have garnered great attention as the key character in metal-air batteries. Herein, we developed a superior nonprecious bifunctional oxygen electrocatalyst, fabricated through spatial confinement of Fe/Fe3C nanocrystals in pyridinic N and Fe-Nx rich carbon nanotubes (Fe/Fe3C-N-CNTs). During ORR, the resultant electrocatalyst exhibits positive onset potential of 1.0 V (vs. RHE), large half-wave potentials of 0.88 V (vs. RHE), which is more positive than Pt/C (0.98 V and 0.83 V, respectively). Remarkably, Fe/Fe3C-N-CNTs exhibits outstanding durability and great methanol tolerance, exceeding Pt/C and most reported nonprecious metal-based oxygen reduction electrocatalysts. Moreover, Fe/Fe3C-N-CNTs show a markedly low potential at j =10 mA/cm2, small Tafel slopes and extremely high stability for OER. Impressively, the Fe/Fe3C-N-CNTs-based Zn-air batteries demonstrate high power density of 183 mW/cm2 and robust charge/discharge stability. It is revealed that the spatial confinement effect can impede the aggregation and corrosion of Fe/Fe3C nanocrystals. Meanwhile, Fe/Fe3C and Fe-Nx play synergistic effect on boosting the ORR/OER activity, which provides an important guideline for construction of inexpensive nonprecious metal-carbon hybrid nanomaterials.

Light utilization is one of the key factors for the improvement of photocatalytic performance. Herein, we design C-TiO2 hollow nanoshells with strong Mie resonance for enhanced photocatalytic hydrogen evolution in a dye-sensitized system under visible light irradiation (λ ≥ 420 nm). By tuning the inner diameters of hollow nanoshells, the Mie resonance in hollow nanoshells is adjusted for better excitation of dye molecules, which thus greatly enhances the light utilization in visible light region. This work shows the potential of Mie resonance in nanoshells can be an alternative strategy to increase the light utilization for photocatalysis.

Advanced anti-counterfeiting materials have great research significance in the fields of economy, safety and human health. Compared with independent color mixed anti-counterfeiting materials, ultraviolet (UV) excitation wavelength-dependent discoloration, which can realize the change of the emission peak shape and color under different excitation wavelengths, is more attractive. In this work, the Sb-doped Cs2ZrCl6 vacancy-ordered double perovskite was designed and synthesized for anti-counterfeiting materials. Due to the singlet and triplet transitions of Sb3+ ions and self-trapping exciton (STE) emission of the Cs2ZrCl6 host, the material showed emission variability from blue to orange-yellow color. In addition, room temperature synthesis and excellent air and humidity stability further enhanced the potential of Sb-doped Cs2ZrCl6 for application.

Conventional photodetectors are usually “color blind” and require additional dispersive components or complicated structures to recognize colors. In this work, an organic photodetector (OPD) is designed with a layer of molybdenum(VI) oxide (MoO3) stacked on an organic donor/acceptor charge transfer interface. The band structure of the OPD is designed with multiple charge separation channels that can be activated/deactivated under reverse and forward biases. The combination of a high or low photocurrent under reverse and forward biases determines the colors of the received light, and that forms the heart of “non-color blind” ability to recognize light colors in the OPD. The energy structure and charge collection pathways in the OPD are investigated with biased external quantum efficiency (EQE), ultraviolet photoelectron spectroscopy (UPS) and current density–voltage (J–V) studies. The OPD with the ability of color and wavelength determination demonstrates its potential to recognize colors without using additional components and the dual mode operation enables it to work under different conditions via switching its detection ranges with bias voltages. This design principle can be utilized to fabricate multifunctional devices by simply selecting different donor–acceptor materials according to the desired detection ranges.

A water-soluble Eu(III) hybrid composite based-on DPA and Phen as ligands, graphene oxide sheets (GOSs) as inorganic matrix, and Eu3+ as luminescence center has been synthesized, namely, Eu–DPA–Phen/GOSs. Compared with single Eu(III) complexes named Eu–DPA–Phen, Eu–DPA–Phen/GOSs not only retains the high luminescence intensity but also shows better solubility, higher stability, and longer fluorescence lifetime. It can be used as a fluorescent probe to detect Cu2+ ions in liquid medium and mixed with polyvinyl alcohol (PVA) to produce a self-supporting film with high luminescence intensity, good stability, mechanical properties. This film is also sensitive to Cu2+ ions and convenient to carry. Thus, it has a great potential in the field of flexible and foldable luminescent devices and fluorescence sensing.

NaMnF3:Yb,Er and NaMnF3:Yb,Er@NaGdF4:xEu (x = 0, 0.3, 0.6, and 0.9) samples were synthesized by a simple hydrothermal method. The as-obtained NaMnF3:Yb,Er particles show a single red emission under the irradiation of infrared light (980 nm), due to the energy exchange transfer process between Mn2+ ions and Er3+ ions. Notably, further growth of NaGdF4:Eu on the basis of NaMnF3:Yb,Er enhanced the green up-conversion luminescence of Er3+ ions, which gradually shifted from red to green with the increase of the Gd3+ ion doping amount. In addition, NaMnF3:Yb,Er@NaGdF4:Eu exhibits red color under ultraviolet excitation (397 nm). These results provide a possible means for controlling the luminescence properties of the lanthanide doped up-conversion system. The luminescent film synthesized with NaMnF3:Yb,Er@NaGdF4:Eu can show different luminescent colors under different light irradiation (near infrared and ultraviolet), which indicates that they have potential applications in multi-mode anti-counterfeiting.

Organo–mineral interactions have long been the focus in the fields of biomineralization and geomineralization, since such interactions not only modulate the dynamics of crystal nucleation and growth but may also change crystal phases, morphologies, and structures. The utilization of an atomic force microscopy (AFM)-based dynamic force spectroscopy (DFS) technique makes it possible to quantify the single-molecule scale organo–mineral binding free energy (ΔGb) correlated with interfacial free energy (γ) and the nucleation energy barrier (ΔG). In this highlight, we briefly review theories of force spectroscopy (FS) and DFS, indicating that single-molecule force spectroscopy (SMFS) can be distinguished with the worm-like chain (WLC) model, and linear and nonlinear DFS data can be analyzed with the Bell–Evans and Friddle–Noy–De Yoreo models to derive noncovalent binding information through the introduction of detailed procedures for DFS experiments from AFM tip modification to FS collection. Moreover, we present some application cases of DFS in unraveling the mechanisms underlying organo-modified nucleation rates, nucleus critical sizes, and phase transformations as well as facet-dependent organo–mineral interactions. The use of an AFM-based DFS technique will improve the fundamental understanding of organo–mineral interactions that affect organo-modified crystal nucleation and growth in both biomineralization and geomineralization processes.

Metal–organic frameworks (MOFs) are a platform with multiple luminescent centers resulting from the multifaceted nature of their structure. Herein, via a facile postsynthetic modification method ap...

The interface material is an indispensable part of perovskite solar cells (PSCs) because of its special functions. In this work, a conjugated polyelectrolyte, PTPADT-SO3Na, was synthesized and intr...

Graphene is electrochemically inert toward the oxygen evolution reaction (OER) owing to the zero-band property, nevertheless doping it with heteroatoms could modulate its electronic structure and increase its chemical reactivity. Notwithstanding the achieved progress, the overpotential of heteroatom doped graphene is still very large. Herein, we coat FeNiIr nanoalloys by nitrogen-doped graphene with core-shell structure (FeNiIr@NG) to further boost the OER activity on graphene surface. Because of the unique core-shell structure, FeNiIr@NG delivers high electrocatalytic OER activity and durability, even exceeding that of commercial IrO2 electrocatalyst. Density functional theory calculations demonstrate that the nanoalloys core could transfer electron to outer graphene shells, which optimizes the electronic structure of graphene and balances the adsorption strength of OER intermediates, thereby triggering OER activity on the graphene surface.

The microstructure evolution and tensile properties of laser directed energy deposition (LDED) 300 M steel with isothermal heat treatment at 320 ℃ for different holding time were investigated in this paper. The results showed that the microstructure of the as-deposited LDED 300 M steel consisted of martensite and bainite. After heat treatment, the microstructure of the LDED 300 M steel is still the mixture of martensite, bainite and retained austenite, while the size of the lower bainite significantly decreased. As the increasing holding time, the content of martensite gradually decreased, while the content of bainite and austenite gradually increased. When the holding time of LDED 300 M steel increased from 20 min to 40 min, the number and size of austenite increased slightly. However, when the holding time was 60 min, the number and size significantly increased. As holding time continuously increase, it contributes little to the number and size of austenite. With regard to the hardness of the LDED 300 M steel, it was 464 HV when the holding time was 20 min. With the increment of holding time, the hardness gradually decreased until 428 HV when the holding time was 80 min. While holding time had less effect on the tensile strength and yield strength. To be specific, the tensile strength decreased from 1348 MPa to 1332 MPa, and yield strength decreased from 853 MPa to 759 MPa. The elongation gradually increased, and it increases to 33 % when the holding time was 80 min, which was higher than that of the forged 300 M steel standard (15 %). Effect of various factors, like microstructure, dislocation density and e-carbides precipitated in the bainite on the ductility of the LDED 300 M steel with isothermal heat treatment was also studied.

The problems of stability and controllability of the finite deformation are investigated for a pre-stressed hyperelastic cylindrical tube subjected to the axial compression. The tube is assumed to be composed of an incompressible neo-Hookean material. Based on the theory of small deformation superposed on large elastic deformation, the mathematical model is formulated by a system of incremental equilibrium equations and incremental boundary conditions. Moreover, the general solutions describing the finite deformation of the tube are obtained by the form of Bessel functions. Finally, the system of nonlinear equations governing the stability of the tube are given, the criteria of the stability discussed in terms of the corresponding numerical simulations.

A novel cubic boron nitride (cBN)-coated silicon nitride(Si3N4) cutting tool was fabricated via the diamond interlayers by electron cyclotron resonance (ECR) microwave plasma chemical vapor deposition (MPCVD) technique. The cutting performance of cBN-coated tools was evaluated by dry turning of hardened ductile iron in comparison with the commercially available titanium aluminum nitride (TiAlN)-coated tools. The effects of cutting parameters on the cutting force and cutting temperature were studied. The results showed that the cutting forces increased with the increase of depth of cut but decreased with the increase of cutting speed, while the cutting temperature increased with the increase of cutting speed. Compared to the TiAlN-coated tools under identical turning conditions, the cBN-coated tools had lower cutting force and cutting temperature, and smaller tool wear. The cBN-coated tools delivered excellent cutting performance and prolonged tool life. Furthermore, the wear patterns and wear mechanisms of cBN-coated tools were investigated. It was found that the dominant wear patterns were crater wear on rake face and flank wear land, and the wear mechanisms were demonstrated to be abrasion wear and diffusion wear. The cutting experiments verified that the cBN-coated tools had attractive potentials in the applications for dry turning of refractory metals and hardened ferrous materials.

Regularly assembled structures of nanowires, such as aligned arrays, junctions and interconnected networks, have great potential for the applications in logical circuits, address decoders, photoelectronic devices and transparent electrodes. However, for now it is still lack of effective approaches for constructing nanowire bifurcated junctions and crosslinked networks with ordered orientations and high quality. Herein, we report the controlled growth of Bi2S3 semiconductor nanowire bifurcated junctions and crosslinked networks with well-aligned directions and high crystalline degree by utilizing the proportional lattice match between nanowires and substrates. Taking advantages of the “tip-to-stem splice” assembly of individual nanowires, the precise orientation alignments of Bi2S3 semiconductor nanowire bifurcated junctions and crosslinked networks were successfully realized. The controlled growth mechanism and structural evolution process have been elucidated by detailed atomic structure characterizations and modeling. The highly crystal quality and direct energy bandgap of as-assembled photodetectors based on individual bismuth sulfide nanowires enabled high photoresponsivity and fast switch time under light illumination. The three-terminal devices based on nanowire bifurcated junctions present rapid carrier transport across the junction. The flexible photodetectors based on nanowire crosslinked networks show very minimal decay of photocurrent after long-term bending test. This work may provide new insights for the guided construction and regular assembly of low-dimensional ordered functional nanostructures towards advanced nanotechnologies.

The shuttle effect of polysulfide (Li2Sn, 2 < n ≤ 8) and the sluggish reaction kinetics seriously hinder the development of lithium–sulfur (Li–S) batteries. Regulating the electronic structure of s...

Polydimethylsiloxane (PDMS) has been the most widely used material in microfluidic systems, especially for cell biology applications. However, the antibacterial performance of PDMS in flow conditions has never been reported in the literature. In this paper, we analyzed the effects of contact angle (CA), adhesion force (work), and surface free energy on the antibacterial activities of PDMS by varying the ratio of curing agents (crosslinking degree) and surface modification with oxygen plasma. The results show that the Young's modulus has no particular effects on bacterial adhesion compared to the CAs of samples. For the first time, we analyzed the adhesion work (AW) effect on biofilm formation, and we found that biofilms tend to form on the surface with less AW. Furthermore, we analyzed the dual effect of hydrophilicity and shear force induced by fluid flow on the bacterial adhesion in PDMS microfluidic systems. We found that at low flow rates in microfluidic conditions, the adhesion of the bacteria on the PDMS surface is inhibited when the fluid flow exceeds a certain value. It required higher shear force to inhibit bacterial adhesion on the hydrophilic surface than on the hydrophobic surface. Therefore, hydrophilicity might be the dominant factor affecting bacterial adhesion.

This paper presents a new approach to formulating an analytical model for the underfill process in flip-chip packaging to predict the flow front and the filling time. The new approach is based on the concept of surface energy along with the energy conservation principle. This approach avoids the need of modeling the flow path to predict the flow front and the filling time, and thus it is suitable to different configurations of solder bumps, including different shapes and arrangements of solder bumps in flip-chip packaging. An experiment along with the computational fluid dynamics simulation was performed based on a proprietarily developed testbed to verify the effectiveness of this approach. Both the experimental and simulation results show that the proposed approach along with its model is accurate for flip-chip packages with different configurations besides the configuration of a regular triangle arrangement of solder bumps and a spherical shape of the solder bump.

Single matrix white luminescent materials are relatively rare. Here, we report an excitation wavelength-dependent Cs2HfCl6:xSb (CHC:xSb) vacancy-ordered double perovskite where, by adjusting the excitation wavelength, different types of white light emission can be obtained.

Hyaluronic acid (HA)-based hydrogels are widely used in biomedical applications due to their excellent biocompatibility and enzymatic degradability. In this paper a photo-crosslinking double-network hyaluronic acid-based hydrogel dressing was proposed. Hyaluronic acid can be UV-crosslinked by modification with methacrylic anhydride (HA-MA) and disulfide-crosslinked by modification with 3,3'-dithiobis (propionylhydrazide) (DTP) (HA-SH). The mixings of these two materials at different ratios were produced. All the samples can be quickly gelled at 365 nm for 10 s. The rheological tests show that the storage modulus (G') of the double network (HA-SH/HA-MA) hydrogel is increased with the increase of HA-SH content. The HA-SH/HA-MA hydrogel has porous structure, high swelling ratio and Controlled degradation rate. In vitro degradation tests show that the ratio of HA-SH/HA-MA ratio was 9:1 (S9M1) in 100 U/ml hyaluronidase (Hase) degraded by 89.91±2.26% at 11d. The cytocompatibility of HA-SH/HA-MA hydrogels was proved by Live/Dead stainings and CCK-8 assays in the human dermis fibroblasts (HDF) cells test. All these results highlight the biological potential of the HA-SH/HA-MA hydrogels for DFU intervention.

Microfluidics has great control over the size and uniformity of microspheres, which has been widely used in fabrication of different types of microspheres such as core-shell microbubbles. Gelatin Methacrylate (GelMa) as a biodegradable material that is closely resemble to native extracellular matrix (ECM). Photocrosslinked GelMa microspheres have gained numerous concerns in biomedical applications especially in three-dimensional cell culture and tissue engineering. In this article, we presented a suitable core-shell cell carrier based on biocompatible GelMa microbubbles. Highly monodispersed microbubbles were fabricated using a non-planar flow focusing microfluidic device. Both intact and collapsed microbubbles morphology were characterized through scanning electron microscopy (SEM), where clear hollow structures were found resulting from the gas core collapsing during the manipulation process. Furthermore, human umbilical vein endothelial cells (HUVEC) were seeded in the existence of microbubbles. Cells adhesion, migration and proliferation were observed in one week. It was notable that cells maintained high level of cell viability throughout the experiment. GelMa microbubble surface was also covered with cells, which became a facile carrier for cell culturing and targeted cell delivery.

Vanadium oxides are a class of promising anode candidates for sodium-ion batteries (SIBs) with high theoretical capacity and low cost. However, their practical application has been impeded by the low electronic conductivity, sluggish ionic transport and large volume change upon sodiation. Herein, a novel, high-performance anode for SIBs based on an oxygen-deficient vanadium oxide (VO/V2O3) heterostructure embedded in porous nitrogen-doped carbon (denoted as VNC) derived by a very simple and localized phase transition from a vanadium glycolate precursor has been demonstrated. The strong synergy of the hierarchically porous framework, VO/V2O3 phase heterojunctions with oxygen vacancy defects, and interfacial coupling with N-doped carbon (NC) efficiently promotes the electron/ion transport and alleviates the volume change during the sodiation/de-sodiation process. Electrochemical evaluation reveals that this novel VNC anode material manifests high sodium-ion storage capability and stability. Ex situ X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses show that (a portion of) the vanadium oxides can be converted into vanadium metal and sodium oxides. First-principles density functional theory (DFT) calculations reveal that coupling with NC effectively enhances the interfacial interactions and charge transfer between vanadium oxides and carbon, as well as the conversion reaction kinetics during sodiation/desodiation. The present work offers a viable strategy for the rational design and exploration of novel heterostructure composite electrodes for a wide array of beyond-lithium-ion batteries.

Perovskite is emerging as a novel emitter in solution-processed light-emitting diodes (LEDs). In these LEDs, morphology, especially the grain size of perovskite, plays a key role in determining electroluminescence performance. Several studies have shown that sizes of the perovskite grains can be controlled by the contact angle between the perovskite solution and the substrate. In this work, we found that in the quasi-two-dimensional (2D) system, the perovskite grain size can be substantially refined when there are hydrogen bonding between the perovskite's organic spacer and the substrates. In fact, for quasi-2D perovskite, with the presence of such hydrogen bond, its effects on the perovskite grain size overshadow the contact angle's effect. We demonstrated that perovskite with refined grains can form amine- or carbazole-based polymers which can form N···H hydrogen bonding with the perovskite's organic spacer. Using these polymers as hole-transporting layers on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate, external quantum efficiency of CsPbBr3-based LEDs can be enhanced from 1.5 to 10.0% without passivation treatment. This work suggests that bonding between perovskite precursors and the substrate can have significant influence on the morphology of the final perovskite grains and their optoelectronic performance.

The electrocatalytic nitrogen reduction reaction (e-NRR), an eco-friendly and economical approach to convert nitrogen to ammonia under mild conditions, has received widespread attention in recent years. Defect engineering has been illustrated to be an effective strategy to improve the catalytic activity and selectivity of electrocatalysts via changing the electronic states as well as creating additional active sites for reduction reactions. Thus far, various approaches have been adopted to tune the physical and chemical properties of catalyst materials by means of inducing defects of different types and varying their concentrations or locations in host materials. In this review, the mechanisms and design principles of defective electrocatalysts for the NRR are introduced, and the refined synthesis and characterization techniques of defect engineering are systematically summarized. Based on the recent advances in defect engineering of electrocatalysts for the NRR, the roles of various defect states, such as vacancies and the amorphous phase, in the catalytic enhancement mechanism are comprehensively discussed. Finally, perspectives on the challenges and opportunities in developing new cost-effective and high-efficiency NRR catalysts for practical applications are outlined.

Hole transporting materials (HTMs) play a critical role in ameliorating the performance of perovskite solar cells (PSCs). Dedicated HTMs can improve not only the hole extraction and efficiency but also the stability. Herein, PFDT-COOH and its fluorinated derivative, PFDT-2F-COOH, are introduced as dopant-free HTMs for inverted PSCs. Compared to PFDT-COOH, PFDT-2F-COOH exhibits a deeper highest occupied molecular orbital (HOMO) level, a higher work function on indium tin oxide electrodes, and an elevated built-in potential in the device. The PFDT-COOH device based on FA1−xMAxPbI3 mixed-cation perovskite exhibits a champion power conversion efficiency (PCE) of 20.64%, while the PFDT-2F-COOH device exhibits a champion PCE of 21.68%, which is close to the highest value (21.7%) attained in inverted single-junction PSCs. The elevated efficiency is attributed to reduction of carrier recombination and enhancement of carrier extraction via the fluorination strategy. In addition, the two devices also show excellent operational and thermal stabilities. Therefore, our work offers a feasible strategy for preparing high efficiency and stable inverted PSCs.

Bismuth (Bi) is a promising alloy-type material for potassium-ion batteries (KIBs). However, its large volume variation during the cycling process remains a great challenge to its practical application. Here, a one-step approach was developed to synthesize a novel Bi-based composite structure comprising Bi nanorod networks confined in a N, S co-doped carbon matrix (Bi∈NS–C). As an anode, the Bi∈NS–C structure successfully integrated the merits of the micro-sized N, S co-doped carbon matrix, which functioned concurrently as a conductive framework and a robust buffer for large volume variation, and the network structure of Bi nanorods which enhanced the reaction kinetics and accommodated the large strain originating from the alloying/dealloying process. As a result, the Bi∈NS–C electrodes exhibited an excellent overall performance, i.e., high rate capabilities of 338 mA h g−1 and 289 mA h g−1 at current densities of 0.5 and 6 A g−1, respectively, and outstanding long-term cycling stability with 91% capacity retention at 5 A g−1 after 1000 cycles. Furthermore, a full KIB with hexacyanoferrate as the cathode and Bi∈NSC as the anode was assembled, which was demonstrated to be able to deliver a decent energy density of 295 W h kg−1 and superior cycling stability with 83% capacity retention after 800 cycles.

The amount and uniformity of carbon nanotubes (CNT) interfacial surface area are one of the key aspects limiting the usage of CNT in composite materials. We report a simple methodology to quantitatively determine the amount and uniformity of CNT interfacial surface area (i.e. level of space filling) using fractal dimension calculation based on scanning electron microscopy images. In this way, we clarified the relationship between the level of space filling of CNT interfacial surface area (fractal dimension) and the properties of rubber and plastic composites to directly relate the dispersion to the composite properties. Our results showed that the electrical conductivity and the tensile strength of composites increased exponentially and linearly with the increased level of space filling of CNT interfacial surface area, respectively within our experimental range. Importantly, these relationships were general, that is, independent of dispersion methods, CNT concentration, CNT types and kinds of matrix (such as rubber, plastic). Taken together, these results serve as a general map to increase the level of space filling of interfacial surface area through controlling various dispersion conditions during CNT dispersion, which is of great significance to the fabrication of CNT composites.

Heteroatom doping and three-dimensional (3D) porous structures are critical to the performance of graphene supercapacitor electrode materials. However, the conventional methods, such as chemical vapor deposition (CVD) and hydrothermal synthesis, require tedious processes and harsh conditions. In this work, we describe a very simple and efficient approach to fabricate a 3D nitrogen/sulfur-co-doped porous graphene hydrogel (3DNS-GH). It is found that thiourea can reduce graphene oxide (GO) obtaining 3DNS-GHs at low temperature and atmospheric pressure by adjusting the pH value, because the reducibility of thiourea significantly increases in acidic or alkaline media. Furthermore, the amount of nitrogen and sulfur doping and nano-pore structure varies with the pH value of solution. The 3DNS-GH exhibits uniform pore structure and can be directly used as electrode materials without additive binder. The binder-free electrode based on the optimum operating conditions (3DNS-GH-12) exhibit a high specific capacitance of 259.2 F g−1 and retain 96.0% of its initial capacitance after 10,000 cycles in 2 M KOH solution at 10 A g−1. Additionally, the symmetrical supercapacitor assembled by the 3DNS-GH-12 showed an impressive energy density of 6.08 W h kg−1 and a high power density of 7.51 kW kg−1. Therefore, these materials demonstrate excellent performance, indicating this route possess potential applied value in the production of supercapacitor electrode materials.

Designing high efficient and noble metal-free bifunctional electrocatalysts for both hydrogen and oxygen generation is still critical and challenged. In this study, hierarchical dodecahedral-structured CoP/CN@MoS2 is prepared through a two-step calcination treatment and a solvothermal approach. The metal-organic framework of ZIF-67 is chosen to serve as the template and for providing Co sources, in which ZIF-67 is first transformed to Co nanoparticles embedded in nitrogen-doped carbon polyhedrons and then transformed to CoP/CN. MoS2 nanosheets are further grown on the surface of dodecahedral-structured CoP/CN with a solvothermal method. Benefiting from the synergistic coupling effect of CoP and MoS2 and the nitrogen-doped carbon matrix, advanced hydrogen evolution reaction (HER) both in acid and alkaline solution as well as splendid oxygen evolution reaction (OER) performance in alkaline aqueous were achieved. Moreover, the coupling effect of CoP/CN and MoS2 is disclosed theoretically by density functional theory calculations to validate the increased HER activity. The as-prepared hybrid CoP/CN@MoS2 not only exhibits decent HER activity in acidic (η10 = 144 mV) and alkaline solutions (η10 = 149 mV), but also exhibits splendid OER activity (η10 = 289 mV) in 1.0 M KOH. This work represents a solid step toward boosting the electrocatalytic kinetics of nonprecious catalysts.

Strain sensors for human health monitoring are of paramount importance in wearable medical diagnostics and personal health monitoring. Despite extensive studies, strain sensors with both high durability and stretchability are still desired, particularly with the stability for different environmental conditions. Here, we report a series of strain sensors possessing the graphene network with a high density of intermittent physical interconnections, which produces the relative resistance change by varying the overlap area between the neighboring graphene sheets under stretching and releasing, analogous to the slide rheostat working in electronics. Our in‐situ transmission electron microscope observation reveals the full recoverability of the structure from large deformation upon unloading for ensuring the exceptional cycle stability of our material on monitoring full‐range body movements. The stable response is also demonstrated over wide temperature range and frequency range, because the peculiar dynamic structure can be maintained through the self‐adjustment to the thermal expansion of the bulk material. Based on the working mechanism of graphene “slide rheostat,” the sensing properties of the strain sensor are tailored by tuning the graphene network structure with different mass densities using different concentrations of graphene oxide dispersion, while the stretchability and sensitivity can be separately optimized for different application requirements.

Pt-SnO2 catalysts supported on modified carbon fibers were prepared by an electrospinning method with polyacrylonitrile (PAN) as the carrier and polyvinylidene fluoride (PVDF) as the pore-forming agent. The physical-chemical property and catalytic performance of the as-synthesized composites were characterized by XRD, SEM, BET, Chronoamperometry and AC impedance. The results showed that the porous structure in the carbon fibers was formed after calcination at 800 °C in the presence of PVDF. When the weight ratio of PAN/PVDF was 1:0.8, the porous carbon fibers had the largest surface area of 374.85 m2 g−1, which was 3.3 times of carbon fibers prepared without PVDF. The in-situ formed porous structure in carbon fibers can provide more active sites for the catalytic reaction. Therefore, the porous carbon fiber supported Pt-SnO2 catalysts exhibited the best catalytic performance with the ethanol oxidation peak current value of 140.14 mA cm−2 and the electrochemical active area up to 54.296 m2 g−1. DEFC performance showed that the best potential was 0.7 V and the maximum of power density was 18.1 mW cm−2 when the oxygen flow rate and the temperature were 100 mL min−1 and 80 °C, respectively.

A series of carbon nanoparticles (CNPs) with emission wavelength ranging from 483 to 525 nm were prepared by hydrothermal treatment of poly-3-thiopheneacetic acid (PTA) and NaOH. The emission wavelength and surface oxidation degree of CNPs were shown to be controllable by simply adjusting NaOH concentration. These CNPs presented obvious fluorescence spectral response toward copper ions (Cu2+) through static quenching caused synergistically by electron transfer and inner filter effect. The O- and S-containing groups on the surface of CNPs were demonstrated to be responsible for their outstanding sensing performance. Based on that, a CNPs-based ratiometric fluorescent probe for Cu2+ with a high fluorescence quenching rate constant of 1.4 × 105 L/mol and a short response time (10 s) was developed. Their practical applications in detecting Cu2+ in pond water and living cells were also demonstrated.

The ceramics of Sr3-xBaxSn2O7 (0 ≤ x ≤ 0.6) were synthesized by solid-state reaction method. The lattice constants of Sr3-xBaxSn2O7 increase with increasing of Ba doping. With increasing of the Ba2+ concentration from x = 0 to x = 0.2, the phase transition temperature reduces by 73 K. The vibration modes related to the phase transitions are strongly related to the tilting and rotation of SnO6 octahedra. The doping of Ba significantly aggravates the anharmonic effect and increases the Raman activity of the vibration mode A 2 ( 5 ) , and reduces the phonon lifetime and the Raman activity of the vibration mode A 1 17 .

Besides high quality perovskites, a precisely designed interface is always necessary to achieve top performance perovskite solar cells. However, this inevitably introduces complexity for fabricatio...

Optical loss is one of the main factors that restrict the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Anti-reflective coating and light-trapping structure is one of the effective methods to enhance light capture and thus improve PCE. Through the finite-difference time-domain (FDTD) method, polydimethylsiloxane (PDMS) anti-reflection coatings with different light-trapping structures were introduced in the air–glass interface of planar heterojunction-based PSCs. Calculating the optical absorption, the inverted-pyramid structure had the best anti-reflection performance. On this basis, in order to further improve photon absorption of perovskite layers, an optical coupling structure with double-decker inverted pyramids are designed by inserting an inverted pyramid structure between perovskite layer and TiO2. According to the cross-sectional | E | 2 distribution of the EM wave inside the device, three different marshalling patterns of the optical coupling structure are proposed and studied to select the best one for PSCs. This kind of marshalling pattern can highly enhance light harvesting of perovskite solar cells, thus increasing the generation rate of charge carrier in perovskite layers and improving the PCE.

A novel inclined excitation method for eddy current thermography was proposed to eliminate the “fuzzy effect” together with the wavelet singularity-based image segmentation that effect adversely the crack detection level, especially for non-ferromagnetic materials. The efficiency of crack detection with parallel and inclined excitation was numerically investigated at different heating periods, crack depths and widths. The inclined excitation was shown to effectively enhance the detection effect and increase the heating period to 6 s that can reduce the impact of the “proximity effect” of the coil and make the detection results clear-cut. The inclined excitation method was adequate for cracks of different depths. The discontinuity point detection method was proposed for the quantitative identification of crack widths. Aluminum specimens with penetrating cracks were tested using the inclined excitation, and the detection results were processed based on the wavelet singularity detection method. Crack temperature variations under the inclined excitation are similar to those of numerical simulation, and the crack can be followed more closely and accurately, thus the combination of inclined excitation and wavelet singularity can effectively improve thermographic images.