Micropillar array electrodes (μAEs) have been widely applied in electrochemical detection owing to their advantages of increased mass transport, lower detection limit, and potential to be ...miniaturized. This paper reports the fabrication, simulation, surface modification, and characterization of PDMS-based μAEs coated with gold films. The μAEs consist of 9 × 10 micropillars with a height of either 100 μm, 300 μm, or 500 μm in a 0.09 cm
2
region. Numerical simulation was employed to study the influence of geometrical parameters on the current density. The μAEs were fabricated by soft lithography and characterized using both SEM and cyclic voltammetry. Experiments revealed that high pillars enabled enhanced voltammetric current density regardless of the scan rates. The platinum-palladium/multi-walled carbon nanotubes (Pt-Pd/MWCNTs) were coated on the μAEs to improve their electrochemical detection capability. The μAEs demonstrated 1.5 times larger sensitivity compared with the planar electrode when hydrogen peroxide was detected. Furthermore, μAE500 with Pt-Pd/MWCNTs was employed to detect sarcosine, a potential biomarker for prostate cancer. The linear range and limit of detection for sarcosine were from 5 to 60 μM and 1.28 μM, respectively. This detection range covers the concentration of sarcosine in human tissues (0-60 μM). These results suggest that the μAEs have better detection performance in comparison to planar electrodes due to their large surface area and pillar height. This paper provides essential guidelines for the application of μAEs in high sensitivity electrochemical detection of low abundance analytes.
PDMS-based micropillar array electrodes with increased surface area and surface modification were developed to detect biomarkers with high sensitivity.
Thermal springs in the Jiangcang Basin occur in a typical geothermal zone along the northeastern edge of the Qinghai-Tibet Plateau in the northern Qilian orogenic belt. The thermal spring water (TSW) ...in this region can be divided into three groups on the basis of temperature and salinity, but the origin and recharge-discharge mechanism of the geothermal fluid remain unclear. The chemical and isotopic characteristics of these thermal springs were studied, and the genesis of the thermal system hosted by deep-seated faults was assessed. The results indicate that the springs in this region are of meteoric origin and heated via deep circulation through well-developed faults. The TSW in the Datong River washland and in the southern part of the basin are derived from carbonate rocks recharged from Datong Mountain, whereas the TSW in the northern part of the basin originates from silicates recharged from Tuolai Mountain. Differences in the circulation depth, flow pathway, residence time, and mixing relationship with cold water lead to different TWS characteristics. The results are used to establish a conceptual model of the origins and circulation of the Jiangcang thermal springs. These findings provide a geological and scientific basis for the development and use of geothermal resources in the northeastern Qinghai-Tibet Plateau.
In this paper, anode current density distribution in high-current vacuum arcs have been investigated experimentally based on the split anode and cup-shaped axial magnetic field (AMF) cathode ...configuration system. The anode surface was divided into four areas by split: one central area with a diameter of 18mm, and three symmetrical peripheral fan-shaped areas with the internal and external diameters of 22 mm and 60 mm, respectively. The contacts material was CuCr25 and the arc current varied from 6kA to 14kA (rms). The currents of the four areas on the anode contact were measured by four Rogowski Coils outside of the vacuum chamber, and the anode current density of each areas was determined by the area and current of regions. From the experimental results, the peak anode current density of central area on the anode surface increased from 14.4 A/mm 2 to 37.7 A/mm 2 , accompanied with the arc mode from the intense arc mode (14kA) from the diffuse arc mode (7.6kA). Moreover, the current density distribution became more non-uniform as the current increased, and the current density of the central area was much larger than that of other peripheral regions on the anode surface.
Anode activity is critical in a high-current interruption process of a vacuum interrupter. Under a high-current arc anode surface temperature may exceed melting point. Under such condition, an ...evaporation of metal vapor from an anode melting pool may play a role for a failure of the current interruption. The objective of this paper is to develop a 2D axisymmetric numerical simulation model of heat transfer from a vacuum arc column to an anode region under high-current vacuum arc. The model combined both the magnetohydrodynamic (MHD) model of a vacuum arc column and the heat transfer model of an anode region. The model deals with arc plasma behavior of arc column and heat transfer in the anode region in a coupled way. The temperature distribution, plasma pressure and flow velocity are given. The highest temperature on anode surface is about 1750K and appears at about 7ms. The effect of Lorentz force on the flow of arc plasma was significant. It pushed the arc plasma into the central region and affects the pressure distribution. The results can offer detailed information of high-current vacuum arc and its anode phenomena.
Iron oxyhydroxide has been considered an auspicious electrocatalyst for the oxygen evolution reaction (OER) in alkaline water electrolysis due to its suitable electronic structure and abundant ...reserves. However, Fe‐based materials seriously suffer from the tradeoff between activity and stability at a high current density above 100 mA cm−2. In this work, the Ce atom is introduced into the amorphous iron oxyhydroxide (i.e., CeFeOxHy) nanosheet to simultaneously improve the intrinsic electrocatalytic activity and stability for OER through regulating the redox property of iron oxyhydroxide. In particular, the Ce substitution leads to the distorted octahedral crystal structure of CeFeOxHy, along with a regulated coordination site. The CeFeOxHy electrode exhibits a low overpotential of 250 mV at 100 mA cm−2 with a small Tafel slope of 35.1 mVdec−1. Moreover, the CeFeOxHy electrode can continuously work for 300 h at 100 mA cm−2. When applying the CeFeOxHy nanosheet electrode as the anode and coupling it with the platinum mesh cathode, the cell voltage for overall water splitting can be lowered to 1.47 V at 10 mA cm−2. This work offers a design strategy for highly active, low‐cost, and durable material through interfacing high valent metals with earth‐abundant oxides/hydroxides.
Ce atom is introduced into the amorphous iron oxyhydroxide nanosheet to tailor electronic structure and octahedral structure for efficient electrochemical oxygen evolution reaction and water splitting, and remarkably improved activity and stability is achieved.
•MXene-holey graphene hydrogel was prepared by in-situ hydrothermal reaction.•The holey graphene can prevent the stacking of MXene sheets.•MX-HGH delivers a specific capacity of 415 F g−1 and 597 F ...cm−3.•The assembled device shows a specific energy of 15.4 Wh kg−1 at 22.2 Wh L−1.
MXene, a new two-dimensional material, has attracted much attention in the field of energy storage. Assembling it into a three-dimensional structure is an effective way to solve the self-stacking problem. However, the assembly of MXene into a three-dimensional structure inevitably reduces the density of the electrode, resulting in a low volumetric capacitance. Here, three-dimensional MXene-holey reduced graphene oxide hydrogel with hierarchical porous structure was obtained by low-temperature hydrothermal treatment, which was used as superior performance binder-free supercapacitor electrode. In the MXene-holey reduced graphene oxide hydrogel electrode, holey reduced graphene oxide can accelerate ion transport, shorten ion and electron transport pathways, and improve the gravimetric capacitance as well as the volumetric capacitance of the electrode. When MX-HGH is applied to the electrode of supercapacitor, it can release gravimetric capacitance up to 415 F g−1 and volumetric capacitance of 597 F cm−3. This work demonstrates a practical method to construct three-dimensional MXene structures with high gravimetric capacitance and relatively high volumetric capacitance, opening up a fresh idea for the application of MXene three-dimensional structures in supercapacitors.
In the communication of ternary optical computer (TOC), channel failure can make the communication system restart and data retransmission too many times, resulting in wasted resources. We have done ...the following work to solve this problem: proposed a parity check code for TOC. And take it as the core to improve the ternary Hamming code theory. To realize the practical application of Hamming code, ternary logic gates (MIN gate, MAX gate, and NOT gate) are designed. The Hamming code error correction module is designed by taking ternary logic gates as the essential component. Compared with TOC without the error correction module, the Hamming code error correction module can improve tolerance of the TOC channel for occasional failures. It dramatically reduces the communication cost and the waste of resources. Finally, this paper designs a set of verification experiments of Hamming code theory to verify its correctness. The experimental results show that the bit error rate of TOC output results can be reduced by one order of magnitude after error correction by Hamming code error correction module.
Fast infrared response (rising time = 24 ms) and ultrahigh photoconductive gain (108) are obtained in epitaxial PbS‐nanoplate–graphene heterostructures. Combining density functional theory with ...experiments, this study finds single‐crystalline PbS nanoplates are covalently bound to the grapheme edge with strong chemical hybridization, which offers a fast carrier transmission path.
Mesenchymal stem cell-derived extracellular vesicles (MSC-EVs), containing proteins or microRNAs (miRNAs), possessing various biological activity and low immunogenicity, are considered promising for ...surface modification of bone grafts. However, the modification efficiency is not satisfied yet, resulting in compromised therapy effects. Here, we report a novel immobilized method by self-assembling biotinylated MSC-EVs onto the surface of biotin-doped polypyrrole titanium (Bio-Ppy-Ti) to improve its biofunctions in vitro and in vivo. Using this method, the amount of human adipose-derived stem cell-EVs (hASC-EVs) anchored onto the Bio-Ppy-Ti surface was 185-fold higher than that of pure Ti after ultrasonic concussion for 30 s and it remained stable on the Bio-Ppy-Ti surface for 14 days at 4 °C. Compared to pristine Ti, EV-Bio-Ppy-Ti exhibited enhanced cell compatibility and osteoinductivity for osteoblasts in vitro and anti-apoptosis ability in the ectopic bone formation mode. Gene chip analysis further demonstrated that several osteoinductive miRNAs were encapsulated in hASC-EVs, which may explain the high bone regeneration ability of EV-Bio-Ppy-Ti. Thus, this MSC-EV biotin-immobilized method appears to be highly efficient and long-term stable for bone graft bioactive modification, demonstrating its potential for clinical metal implants.
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