Perovskite-Carbon Joint Substrate for Practical Application in Proton Exchange Membrane Fuel Cells under Low-Humidity/High-Temperature Conditions

Highly active catalysts with promising water retention are favorable for proton exchange membrane fuel cells (PEMFCs) operating under low-humidity/high-temperature conditions. When PEMFCs operate under low-humidity/high-temperature conditions, performance attenuation rapidly occurs owing to reduced proton conductivity of dehydrated membrane electrode assemblies. Herein, we load platinum onto a perovskite-carbon joint substrate (BaZr0.1Ce0.7Y0.1Yb0.1O3-σ-XC-72R) to construct a highly active and durable catalyst with good water retention capacity. We propose that the Pt/(BZCYYb-C) catalyst layer at cathode can promote the water back diffusion of produced water from the cathode to the membrane, thus preventing the decay of fuel-cell performance under low-humidity/high-temperature conditions. The catalyst exhibited outstanding mass activity of 0.542 A mgpt–1 at 0.9 V vs RHE. PEMFCs with such a catalyst delivered very high peak power densities (1.70/1.14 W cm–2 under H2–O2/air conditions at 70 °C) and kept 85.3%/92.1% of initial performance values under low-humidity/high-temperature conditions (relative humidity 60%@70 °C/100 °C)

Fabrication of a Selective and Sensitive Sensor Based on Molecularly Imprinted Polymer/Acetylene Black for the Determination of Azithromycin in Pharmaceuticals and Biological Samples.

A new selective and sensitive sensor based on molecularly imprinted polymer/acetylene black (MIP/AB) was developed for the determination of azithromycin (AZM) in pharmaceuticals and biological samples. The MIP of AZM was synthesized by precipitation polymerization. MIP and AB were then respectively introduced as selective and sensitive elements for the preparation of MIP/AB-modified carbon paste (MIP/ABP) electrode. The performance of the obtained sensor was estimated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Compared with non-molecularly imprinted polymer (NIP) electrodes, NIP/ABP electrodes, and MIP-modified carbon paste electrodes, MIP/ABP electrode exhibited excellent current response toward AZM. The prepared sensor also exhibited good selectivity for AZM in comparison with structurally similar compounds. The effect of electrode composition, extraction parameters, and electrolyte conditions on the current response of the sensor was investigated. Under the optimized conditions, the prepared sensor showed two dynamic linear ranges of 1.0 × 10-7 mol L-1 to 2.0 × 10-6 mol L-1 and 2.0 × 10-6 mol L-1 to 2.0 × 10-5 mol L-1, with a limit of detection of 1.1 × 10-8 mol L-1. These predominant properties ensured that the sensor exhibits excellent reliability for detecting AZM in pharmaceuticals and biological fluids without the assistance of any separation techniques. The results were validated by the high-performance liquid chromatography-tandem mass spectrometry method

Magnetic Molecularly Imprinted Polymers for the Rapid and Selective Extraction and Detection of Methotrexatein Serum by HPLC-UV Analysis

In this work, novel selective recognition materials, namely magnetic molecularly imprinted polymers (MMIPs), were prepared. The recognition materials were used as pretreatment materials for magnetic molecularly imprinted solid-phase extraction (MSPE) to achieve the efficient adsorption, selective recognition, and rapid magnetic separation of methotrexate (MTX) in the patients’ plasma. This method was combined with high-performance liquid chromatography–ultraviolet detection (HPLC–UV) to achieve accurate and rapid detection of the plasma MTX concentration, providing a new method for the clinical detection and monitoring of the MTX concentration. The MMIPs for the selective adsorption of MTX were prepared by the sol–gel method. The materials were characterized by transmission electron microscopy, Fourier transform-infrared spectrometry, X-ray diffractometry, and X-ray photoelectron spectrometry. The MTX adsorption properties of the MMIPs were evaluated using static, dynamic, and selective adsorption experiments. On this basis, the extraction conditions were optimized systematically. The adsorption capacity of MMIPs for MTX was 39.56 mgg−1, the imprinting factor was 9.40, and the adsorption equilibrium time was 60 min. The optimal extraction conditions were as follows: the amount of MMIP was 100 mg, the loading time was 120 min, the leachate was 8:2 (v/v) water–methanol, the eluent was 4:1 (v/v) methanol–acetic acid, and the elution time was 60 min. MTX was linear in the range of 0.00005–0.25 mg mL−1, and the detection limit was 12.51 ng mL−1. The accuracy of the MSPE–HPLC–UV method for MTX detection was excellent, and the result was consistent with that of a drug concentration analyzer

DPV curves (A) of the MIP/ABP electrode in different concentrations of AZM (from a to i): 0.1, 0.2, 0.5, 1, 2, 5, 10, 15 and 20 μM. Calibration curve (B) of AZM under the optimized conditions.

<p>DPV curves (A) of the MIP/ABP electrode in different concentrations of AZM (from a to i): 0.1, 0.2, 0.5, 1, 2, 5, 10, 15 and 20 μM. Calibration curve (B) of AZM under the optimized conditions.</p

Comparison of the presented MIP/ABP electrode with other reported electrodes for AZM determination.

<p>Comparison of the presented MIP/ABP electrode with other reported electrodes for AZM determination.</p

Chemical structures of six MACs and six other compounds tested in this study.

<p>The six MACs are AZM, ERY, TM, OLE, TYL, and CLA. The six other compounds are DA, STM, GM, TC, NM, and TAP.</p

DPV curves (A) of the MIP/ABP electrode in different concentrations of AZM (from a to i): 0.1, 0.2, 0.5, 1, 2, 5, 10, 15 and 20 μM. Calibration curve (B) of AZM under the optimized conditions.

<p>DPV curves (A) of the MIP/ABP electrode in different concentrations of AZM (from a to i): 0.1, 0.2, 0.5, 1, 2, 5, 10, 15 and 20 μM. Calibration curve (B) of AZM under the optimized conditions.</p

Detection of AZM in real samples by the developed electrochemical method (<i>n</i> = 3) and HPLC-MS/MS method (<i>n</i> = 3).

<p>Detection of AZM in real samples by the developed electrochemical method (<i>n</i> = 3) and HPLC-MS/MS method (<i>n</i> = 3).</p