Scaling-Up Insights for Zinc-Air Battery Technologies Realizing Reversible Zinc Anodes.

Zinc-air battery (ZAB) technology is considered one of the promising candidates to complement the existing lithium-ion batteries for future large-scale high-energy-storage demands. The scientific literature reveals many efforts for the ZAB chemistries, materials design, and limited accounts for cell design principles with apparently superior performances for liquid and solid-state electrolytes. However, along with the difficulty of forming robust solid-electrolyte interphases, the discrepancy in testing methods and assessment metrics severely challenges the realistic evaluation/comparison and commercialization of ZABs. Here, strategies to formulate reversible zinc anodes are proposed and specific cell-level energy metrics (100-500 Wh kg-1 ) and realistic long-cycling operations are realized. Stabilizing anode/electrolyte interfaces results in a cumulative capacity of 25 Ah cm-2 and Coulomb efficiency of >99.9% for 5000 plating/stripping cycles. Using 1-10 Ah scale (≈500 Wh kg-1 at cell level) solid-state zinc-air pouch cells, scale-up insights for Ah-level ZABs that can progress from lab-scale research to practical production are also offered.

Heterointerface promoted trifunctional electrocatalysts for all temperature high-performance rechargeable Zn-air batteries.

The rational design of wide-temperature operating Zn-air batteries is crucial for their practical applications. However, the fundamental challenges remain; the limitation of the sluggish oxygen redox kinetics, insufficient active sites, and poor efficiency/cycle lifespan. Here we present heterointerface-promoted sulfur-deficient cobalt-tin-sulfur (CoS1-δ/SnS2-δ) trifunctional electrocatalysts by a facile solvothermal solution-phase approach. The CoS1-δ/SnS2-δ displays superb trifunctional activities, precisely a record-level oxygen bifunctional activity of 0.57 V (E1/2 = 0.90 V and Ej=10 = 1.47 V) and a hydrogen evolution overpotential (41 mV), outperforming those of Pt/C and RuO2. Theoretical calculations reveal the modulation of the electronic structures and d-band centers that endorse fast electron/proton transport for the hetero-interface and avoid the strong adsorption of intermediate species. The alkaline Zn-air batteries with CoS1-δ/SnS2-δ manifest record-high power density of 249 mW cm-2 and long-cycle life for >1000 cycles under harsh operations of 20 mA cm-2, surpassing those of Pt/C + RuO2 and previous state-of-the-art catalysts. Furthermore, the solid-state flexible Zn-air battery also displays remarkable performance with an energy density of 1077 Wh kg-1, >690 cycles for 50 mA cm-2, and a wide operating temperature from +80 to -40 °C with 85% capacity retention, which provides insights for practical Zn-air batteries.

Supramolecular Polymer Intertwined Free-Standing Bifunctional Membrane Catalysts for All-Temperature Flexible Zn-Air Batteries.

Rational construction of flexible free-standing electrocatalysts featuring long-lasting durability, high efficiency, and wide temperature tolerance under harsh practical operations are fundamentally significant for commercial zinc-air batteries. Here, 3D flexible free-standing bifunctional membrane electrocatalysts composed of covalently cross-linked supramolecular polymer networks with nitrogen-deficient carbon nitride nanotubes are fabricated (referred to as PEMAC@NDCN) by a facile self-templated approach. PEMAC@NDCN demonstrates the lowest reversible oxygen bifunctional activity of 0.61 V with exceptional long-lasting durability, which outperforms those of commercial Pt/C and RuO2. Theoretical calculations and control experiments reveal the boosted electron transfer, electrolyte mass/ion transports, and abundant active surface site preferences. Moreover, the constructed alkaline Zn-air battery with PEMAC@NDCN air-cathode reveals superb power density, capacity, and discharge-charge cycling stability (over 2160 cycles) compared to the reference Pt/C + RuO2. Solid-state Zn-air batteries enable a high power density of 211 mW cm-2, energy density of 1056 Wh kg-1, stable charge-discharge cycling of 2580 cycles for 50 mA cm-2, and wide temperature tolerance from - 40 to 70 °C with retention of 86% capacity compared to room-temperature counterparts, illustrating prospects over harsh operations.

Modeling Hypoxic Stress In Vitro Using Human Embryonic Stem Cells Derived Cardiomyocytes Matured by FGF4 and Ascorbic Acid Treatment.

Mature cardiomyocytes (CMs) obtained from human pluripotent stem cells (hPSCs) have been required for more accurate in vitro modeling of adult-onset cardiac disease and drug discovery. Here, we found that FGF4 and ascorbic acid (AA) induce differentiation of BG01 human embryonic stem cell-cardiogenic mesoderm cells (hESC-CMCs) into mature and ventricular CMs. Co-treatment of BG01 hESC-CMCs with FGF4+AA synergistically induced differentiation into mature and ventricular CMs. FGF4+AA-treated BG01 hESC-CMs robustly released acute myocardial infarction (AMI) biomarkers (cTnI, CK-MB, and myoglobin) into culture medium in response to hypoxic injury. Hypoxia-responsive genes and potential cardiac biomarkers proved in the diagnosis and prognosis of coronary artery diseases were induced in FGF4+AA-treated BG01 hESC-CMs in response to hypoxia based on transcriptome analyses. This study demonstrates that it is feasible to model hypoxic stress in vitro using hESC-CMs matured by soluble factors.

Heuristic Iron-Cobalt-Mediated Robust pH-Universal Oxygen Bifunctional Lusters for Reversible Aqueous and Flexible Solid-State Zn-Air Cells.

Rechargeable aqueous zinc-air cells (ZACs) promise an extremely safe and high energy technology. However, they are still significantly limited by sluggish electrochemical kinetics and irreversibility originating from the parasitic reactions of the bifunctional catalysts and electrolytes. Here, we report the preferential in situ building of interfacial structures featuring the edge sites constituted by FeCo single/dual atoms with the integration of Co sites in the nitrogenized graphitic carbon frameworks (FeCo SAs@Co/N-GC) by electronic structure modulation approach. Compared to commercial Pt/C and RuO2, FeCo SAs@Co/N-GC reveals exceptional electrochemical performance, reversible redox kinetics, and durability toward oxygen reduction and evolution reactions under universal pH environments, i.e., alkaline, neutral, and acidic, due to synergistic effect at interfaces and preferred charge/mass transfer. The aqueous (alkaline, nonalkaline, and acidic electrolytes) ZACs constructed with a FeCo SAs@Co/N-GC cathode tolerate stable operations, have significant reversibility, and have the highest energy densities, outperforming those of noble metal counterparts and state-of-the-art ZACs in the ambient atmosphere. Additionally, flexible solid-state ZACs demonstrate excellent mechanical and electrochemical performances with a highest power density of 186 mW cm-2, specific capacity of 817 mAh gZn-1, energy density of 1017 Wh kgZn-1, and cycle life >680 cycles with extremely harsh operating conditions, which illustrates the great potential of triphasic catalyst for green energy storage technologies.

Histomorphometric Evaluation of Socket Preservation Using Autogenous Tooth Biomaterial and BM-MSC in Dogs.

This study is aimed at assessing the dimensional alterations occurring in the alveolar bone after premolar extraction in dogs with histomorphometric and histological analysis. After atraumatic premolar extraction, tooth-derived bone graft material was grafted in the extraction socket of the premolar region in the lower jaws of six dogs in two experimental groups. In the second experimental group, BM-MSCs were added together with the graft. The control was left untreated on the opposite side. After twelve weeks, all six animals were sacrificed. Differences in alveolar bone height crests lingually and buccally, and alveolar bone width at 1, 3, and 5 mm infracrestally, were examined. Histologic study revealed osteoconductive properties of tooth biomaterial. A statistically significant difference was detected between the test and control groups. In the test groups, a reduced loss of vertical and horizontal alveolar bone dimensions compared with the control group was observed. Tooth bone graft material may be considered useful for alveolar ridge preservation after tooth extraction, as it could limit the natural bone resorption process.

A Membrane Filter-Assisted Mammalian Cell-Based Biosensor Enabling 3D Culture and Pathogen Detection.

We have developed a membrane filter-assisted cell-based biosensing platform by using a polyester membrane as a three-dimensional (3D) cell culture scaffold in which cells can be grown by physical attachment. The membrane was simply treated with ethanol to increase surficial hydrophobicity, inducing the stable settlement of cells via gravity. The 3D membrane scaffold was able to provide a relatively longer cell incubation time (up to 16 days) as compared to a common two-dimensional (2D) cell culture environment. For a practical application, we fabricated a cylindrical cartridge to support the scaffold membranes stacked inside the cartridge, enabling not only the maintenance of a certain volume of culture media but also the simple exchange of media in a flow-through manner. The cartridge-type cell-based analytical system was exemplified for pathogen detection by measuring the quantities of toll-like receptor 1 (TLR1) induced by applying a lysate of P. aeruginosa and live E. coli, respectively, providing a fast, convenient colorimetric TLR1 immunoassay. The color images of membranes were digitized to obtain the response signals. We expect the method to further be applied as an alternative tool to animal testing in various research areas such as cosmetic toxicity and drug efficiency.

Bipolar Energetics and Bifunctional Catalytic Activity of a Nanocrystalline Ru Thin-Film Enable High-Performance Photoelectrochemical Water Reduction and Oxidation.

Photoelectrochemical (PEC) cells, which represent a promising technology for the production of hydrogen fuel through water splitting reactions, must meet two criteria to achieve high-performance operation: (i) a high thermodynamic open-circuit potential and (ii) a low kinetic overpotential. Herein, we achieved these criteria in both an oxygen-evolving n-Si photoanode and hydrogen-evolving p-Si photocathode by simple electrodeposition of a nanocrystalline thin film of Ru. The bifunctional electrocatalytic activity of the nanocrystalline Ru led to low overpotentials in both the acidic oxygen evolution reaction (0.27 V) and alkaline hydrogen evolution reaction (0.04 V). In addition, the nanocrystalline Ru/Si junctions influenced the interface energetics via the induction of an extrinsic electrochemical potential on the surface of the Ru nanocrystals through a redox reaction rather than the chemical potential of the electrons (work function) of bulk Ru. The nanocrystalline Ru film exhibited bipolar applicability, enabling both Ru/n-Si and Ru/p-Si junctions with high Voc values of 0.63 and 0.5 V, respectively. As a result, the n-Si photoanode in the acidic electrolyte and the p-Si photocathode in the alkaline electrolyte generated a photocurrent of 10 mA/cm2 at record values of 0.87 and 0.42 V versus the reversible hydrogen electrode, respectively. These results provide insight into the development of high-performance PEC cells based on a nanocrystalline electrocatalyst.

Effect of autoclave sterilization on cyclic fatigue and torsional fracture resistance of NiTi rotary instruments.

The purpose of this study is to assess the effect of autoclave sterilization on the cyclic fatigue and torsional fracture resistance of ProTaper Universal (PTU), K3XF, HyFlex EDM (EDM), and TF adaptive (TFA). Sixty instruments from each file type were divided into two categories for cyclic fatigue group (CGr) and torsional fracture group (TGr). CGr and TGr were divided into three subgroups, respectively, consisting of ten instruments from each file type. Cyclic fatigue fracture test was performed using artificial canal made of stainless steel, and the mean number of cycles to failure (NCF) were determined. CGr1, the files were tested to establish baseline for NCF; CGr2, the files were tested cyclic fatigue after 10 cycles of autoclave; CGr3, instruments were autoclaved after being cycled to 25, 50, and 75% of corresponding NCF determined in CGr1, followed by cyclic fatigue test. The torsional fracture test was performed without autoclave (TGr1), after 3-cycle autoclave (TGr2), and 7-cycle autoclave (TGr3), respectively, which evaluated maximum torque and angular deflection. NCF, maximum torque and angular deflection were compared using one-way ANOVA with Bonferroni test. Two-way ANOVA was performed to determine the interaction between 'autoclave treatment' and 'type of NiTi file'. EDM showed highest NCF within the same autoclave treatment. TFA presented the lowest maximum torque and the highest angular deflection, and PTU presented the lowest angular deflection. Within the same NiTi file systems, most of NCF, maximum torque and angular deflection of tested files were not significantly influenced by autoclave condition.

A semiconductor junction photoelectrochemical device without a depletion region.

Semiconductor junctions are believed to form a depletion region at the band edge of the semiconductor as the chemical potentials for electrons (work functions) are aligned to the same level. Here, we demonstrated that ultrathin Ni film (less than 4 nm thick)/Si junction-based photoelectrochemical (PEC) devices have no depletion region due to three distinct phenomena: (i) the electrostatic or electrochemical potential extrinsically charged to the electrolytic-capacitive Ni surface dominates rather than the chemical potential of electrons (work function) of the bulk Ni, (ii) the charged potential is dynamically variable depending on the reaction and is rapidly volatile so as not to be constant; therefore, (iii) the charged potential is misaligned with the chemical potential of Si under equivalent circuit conditions. Such junction PEC devices were shown to follow a novel operating principle in which the output voltage (open circuit potential) is generated by the electrochemical potential charged at the Ni surface, and not by the light-induced potential (photovoltage) in Si. In addition, due to the bipolar charging nature, the ultrathin Ni film was effective in achieving a high open circuit potential in both p-Si photocathodes (0.57 V) and n-Si photoanodes (0.45 V). These anomalous results were not explained by the classical Schottky diode model based on the equilibrium of diffusion-drift current but by establishing a new model based on the equilibrium of the diffusion-charging current without accounting for the depletion region. Our findings provide an explanation for the unexpected results of the nanostructured PEC devices and insight into a new design that can overcome conventional limitations.

Seebeck-voltage-triggered self-biased photoelectrochemical water splitting using HfOx/SiOx bi-layer protected Si photocathodes.

The use of a photoelectrochemical device is an efficient method of converting solar energy into hydrogen fuel via water splitting reactions. One of the best photoelectrode materials is Si, which absorbs a broad wavelength range of incident light and produces a high photocurrent level (~44 mA·cm-2). However, the maximum photovoltage that can be generated in single-junction Si devices (~0.75 V) is much lower than the voltage required for a water splitting reaction (>1.6 V). In addition, the Si surface is electrochemically oxidized or reduced when it comes into direct contact with the aqueous electrolyte. Here, we propose the hybridization of the photoelectrochemical device with a thermoelectric device, where the Seebeck voltage generated by the thermal energy triggers the self-biased water splitting reaction without compromising the photocurrent level at 42 mA cm-2. In this hybrid device p-Si, where the surface is protected by HfOx/SiOx bilayers, is used as a photocathode. The HfOx exhibits high corrosion resistance and protection ability, thereby ensuring stability. On applying the Seebeck voltage, the tunneling barrier of HfOx is placed at a negligible energy level in the electron transfer from Si to the electrolyte, showing charge transfer kinetics independent of the HfOx thickness. These findings serve as a proof-of-concept of the stable and high-efficiency production of hydrogen fuel by the photoelectrochemical-thermoelectric hybrid devices.

Synergistic doping effects of a ZnO:N/BiVO4:Mo bunched nanorod array photoanode for enhancing charge transfer and carrier density in photoelectrochemical systems.

One-dimensional heterojunction nanorods are highly attractive as photoanodes for developing efficient photoelectrochemical (PEC) systems for the effective photogeneration of charge carriers and transport. ZnO/BiVO4 nanorod arrays (NRAs) are excellent candidates if their charge transferring and recombination issues can be improved. In the current work, we have studied the synergistic doping effects of N-doped ZnO/Mo-doped BiVO4 NRAs for enhancing the photoanode activity in PEC devices. The N-doping of ZnO NRs enhances the charge carrier density ∼3-fold over undoped ZnO NRs through increased oxygen vacancies induced by N dopants. The Mo dopants in BiVO4 improve the mobility of photogenerated charge carriers and contribute to reducing charge recombination. The synergistic doping effects of both ZnO and BiVO4 could increase the charge transfer rate constant (kct) of the ZnO:N/BiVO4:Mo heterojunction by ∼40% and decrease the charge transfer resistance ∼1.9-fold compared to those of undoped ZnO/BiVO4, which were confirmed by time resolved photoluminescence (PL) and electrochemical impedance (EIS) analyses. Our optimally fabricated ZnO:N/BiVO4:Mo NRA photoanode could achieve an excellent photocurrent of 3.62 mA cm-2 without the application of any co-catalysts. This work presents a useful strategy for designing efficient heterojunction photoanodes in PEC systems.

Solid-State Rechargeable Zinc-Air Battery with Long Shelf Life Based on Nanoengineered Polymer Electrolyte.

Zinc-air batteries (ZABs) are vulnerable to the ambient environment (e.g., humidity and CO2 ), and have serious selfdischarge issues, resulting in a short shelf life. To overcome these challenges, a near-neutral quaternary ammonium (QA) functionalized polyvinyl alcohol electrolyte membrane (different from conventional alkali-type membranes) has been developed. QA functionalization leads to the formation of interconnected nanochannels by creating hydrophilic/-phobic separations at the nanoscale. These nanochannels selectively transport OH- ions with a reduced migration barrier, while inhibiting [Zn(NH3 )6 ]2+ crossover. Owing to the superior water retention ability and enhanced chemical stability of the membrane, the solid-state zinc-air battery (SZAB) displays outstanding flexibility, a promising cycle lifetime, and a large volumetric energy density. More importantly, the self-discharge rate of SZAB is depressed to less than 7 % per month, and the fully dehydrated SZAB could recover its rechargeability upon replenishment of the solution of NH4 Cl.

Current Technologies of Electrochemical Immunosensors: Perspective on Signal Amplification.

An electrochemical immunosensor employs antibodies as capture and detection means to produce electrical charges for the quantitative analysis of target molecules. This sensor type can be utilized as a miniaturized device for the detection of point-of-care testing (POCT). Achieving high-performance analysis regarding sensitivity has been one of the key issues with developing this type of biosensor system. Many modern nanotechnology efforts allowed for the development of innovative electrochemical biosensors with high sensitivity by employing various nanomaterials that facilitate the electron transfer and carrying capacity of signal tracers in combination with surface modification and bioconjugation techniques. In this review, we introduce novel nanomaterials (e.g., carbon nanotube, graphene, indium tin oxide, nanowire and metallic nanoparticles) in order to construct a high-performance electrode. Also, we describe how to increase the number of signal tracers by employing nanomaterials as carriers and making the polymeric enzyme complex associated with redox cycling for signal amplification. The pros and cons of each method are considered throughout this review. We expect that these reviewed strategies for signal enhancement will be applied to the next versions of lateral-flow paper chromatography and microfluidic immunosensor, which are considered the most practical POCT biosensor platforms.

Hierarchically Designed 3D Holey C2N Aerogels as Bifunctional Oxygen Electrodes for Flexible and Rechargeable Zn-Air Batteries.

The future of electrochemical energy storage spotlights on the designed formation of highly efficient and robust bifunctional oxygen electrocatalysts that facilitate advanced rechargeable metal-air batteries. We introduce a scalable facile strategy for the construction of a hierarchical three-dimensional sulfur-modulated holey C2N aerogels (S-C2NA) as bifunctional catalysts for Zn-air and Li-O2 batteries. The S-C2NA exhibited ultrahigh surface area (∼1943 m2 g-1) and superb electrocatalytic activities with lowest reversible oxygen electrode index ∼0.65 V, outperforms the highly active bifunctional and commercial (Pt/C and RuO2) catalysts. Density functional theory and experimental results reveal that the favorable electronic structure and atomic coordination of holey C-N skeleton enable the reversible oxygen reactions. The resulting Zn-air batteries with liquid electrolytes and the solid-state batteries with S-C2NA air cathodes exhibit superb energy densities (958 and 862 Wh kg-1), low charge-discharge polarizations, excellent reversibility, and ultralong cycling lives (750 and 460 h) than the commercial Pt/C+RuO2 catalysts, respectively. Notably, Li-O2 batteries with S-C2NA demonstrated an outstanding specific capacity of ∼648.7 mA h g-1 and reversible charge-discharge potentials over 200 cycles, illustrating great potential for commercial next-generation rechargeable power sources of flexible electronics.

Planar n-Si/PEDOT:PSS hybrid heterojunction solar cells utilizing functionalized carbon nanoparticles synthesized via simple pyrolysis route.

Herein, we present a facile and simple strategy for in situ synthesis of functionalized carbon nanoparticles (CNPs) via direct pyrolysis of ethylenediaminetetraacetic acid (EDTA) on silicon surface. The CNPs were incorporated in hybrid planar n-Si and poly(3,4-etyhlenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solar cells to improve device performance. We demonstrate that the CNPs-incorporated devices showed increased electrical conductivity (reduced series resistance) and minority carrier lifetime (better charge carrier collection) than those of the cells without CNPs due to the existence of electrically conductive sp 2-hybridized carbon at the heterojunction interfaces. With an optimal concentration of CNPs, the hybrid solar cells exhibited power conversion efficiency up to 11.95%, with an open-circuit voltage of 614 mV, short-circuit current density of 26.34 mA cm-2, and fill factor of 73.93%. These results indicate that our approach is promising for the development of highly efficient organic-inorganic hybrid solar cells.

Self-assembled air-stable magnesium hydride embedded in 3-D activated carbon for reversible hydrogen storage.

The rational design of stable, inexpensive catalysts with excellent hydrogen dynamics and sorption characteristics under realistic environments for reversible hydrogen storage remains a great challenge. Here, we present a simple and scalable strategy to fabricate a monodispersed, air-stable, magnesium hydride embedded in three-dimensional activated carbon with periodic synchronization of transition metals (MHCH). The high surface area, homogeneous distribution of MgH2 nanoparticles, excellent thermal stability, high energy density, steric confinement by carbon, and robust architecture of the catalyst resulted in a noticeable enhancement of the hydrogen storage performance. The resulting MHCH-5 exhibited outstanding hydrogen storage performance, better than that of most reported Mg-based hydrides, with a high storage density of 6.63 wt% H2, a rapid kinetics loading in <5 min at 180 °C, superior reversibility, and excellent long-term cycling stability over ∼435 h. The significant reduction of the enthalpy and activation energy observed in the MHCH-5 demonstrated enhancement of the kinetics of de-/hydrogenation compared to that of commercial MgH2. The origin of the intrinsic hydrogen thermodynamics was elucidated via solid state 1H NMR. This work presents a readily scaled-up strategy towards the design of realistic catalysts with superior functionality and stability for applications in reversible hydrogen storage, lithium ion batteries, and fuel cells.

Simple but Effective Way To Enhance Photoelectrochemical Solar-Water-Splitting Performance of ZnO Nanorod Arrays: Charge-Trapping Zn(OH)2 Annihilation and Oxygen Vacancy Generation by Vacuum Annealing.

This study presents an effective and the simplest method to substantially improve the photoelectrochemical water-splitting ability of hydrothermally grown ZnO nanorod arrays (NRAs). In the hydrothermal growth of ZnO NRAs, unwanted Zn(OH)2 species are formed, which act as trapping sites of photoexcited charges. We found that those inherent charge-trapping sites could be annihilated by the desorption of the hydroxyl groups upon vacuum annealing above 200 °C, which resulted in an enhancement of the charge-separation efficiency and photocurrent density. Another drastic increase in the photocurrent density occurred when ZnO NRAs were treated with annealing at higher temperature (700 °C), which can be attributed to the introduced oxygen vacancies acting as shallow donors in the ZnO crystal lattice. The removal of the charge-trapping Zn(OH)2 and the generation of oxygen vacancies were confirmed by photoluminescence (PL) and XPS analyses. The ZnO NRAs treated by this simple method yield a photocurrent density of 600 µA/cm2 at 1.23 VRHE under 1 sun illumination, which is 20 times higher than that obtained from as-grown ZnO NRAs. This study presents a highly efficient way of increasing the bulk electric conductivity and photoelectrochemical activity of metal oxide nanorods without requiring the introduction of any extrinsic dopants.

Semi-continuous, real-time monitoring of protein biomarker using a recyclable surface plasmon resonance sensor.

Although label-free immunosensors based on, for example, surface plasmon resonance (SPR) provide advantages of real-time monitoring of the analyte concentration, its application to routine clinical analysis in a semi-continuous manner is problematic because of the high cost of the sensor chip. The sensor chip is in most cases regenerated by employing an acidic pH. However, this causes gradual deterioration of the activity of the capture antibody immobilized on the sensor surface. To use sensor chips repeatedly, we investigated a novel surface modification method that enables regeneration of the sensor surface under mild conditions. We introduced a monoclonal antibody (anti-CBP Ab) that detects the conformational change in calcium binding protein (CBP) upon Ca2+ binding (>1mM). To construct a regenerable SPR-based immunosensor, anti-CBP Ab was first immobilized on the sensor surface, and CBP conjugated to the capture antibody (specific for creatine kinase-MB isoform (CK-MB); CBP-CAb) then bound in the presence of Ca2+. A serum sample was mixed with the detection antibody to CK-MB, which generated an SPR signal proportional to the analyte concentration. After each analysis, the sensor surface was regenerated using medium (pH 7) without Ca2+, and then adding fresh CBP-CAb in the presence of Ca2+ for the subsequent analysis. Analysis of multiple samples using the same sensor was reproducible at a rate >98.7%. The dose-response curve was linear for 1.75-500.75ng/mL CK-MB, with an acceptable coefficient of variation of <8.8%. The performance of the immunosensor showed a strong correlation with that of the Pathfast reference system (R2>96%), and exhibited analytical stability for 1 month. To our knowledge, this is the first report of a renewal of a sensor surface with fresh antibody after each analysis, providing high consistency in the assay during a long-term use (e.g., a month at least).

Highly active and durable carbon nitride fibers as metal-free bifunctional oxygen electrodes for flexible Zn-air batteries.

The design of flexible, highly energetic, and durable bifunctional oxygen electrocatalysts is indispensable for rechargeable metal-air batteries. Herein we present a simple approach for the development of carbon nitride fibers co-doped with phosphorus and sulfur, grown in situ on carbon cloth (PS-CNFs) as a flexible electrode material, and demonstrate its outstanding bifunctional catalytic activities toward ORR and OER compared to those of precious metal-based Pt/C and IrO2 on account of the dual action of P and S, numerous active sites, high surface area, and enhanced charge transfer. Furthermore, we demonstrate the flexibility, suitability, and durability of PS-CNFs as air electrodes for primary and rechargeable Zn-air batteries. Primary Zn-air batteries using this electrode showed high peak power density (231 mW cm-2), specific capacity (698 mA h g-1; analogous energy density of 785 W h kg-1), open circuit potential (1.49 V), and outstanding durability of more than 240 h of operation followed by mechanical recharging. Significantly, three-electrode rechargeable Zn-air batteries revealed a superior charge-discharge voltage polarization of ∼0.82 V at 20 mA cm-2, exceptional reversibility, and continuous charge-discharge cycling stability during 600 cycles. This work provides a pioneering strategy for designing flexible and stretchable metal-free bifunctional catalysts as gas diffusion layers for future portable and wearable renewable energy conversion and storage devices.