Microplasma electrochemistry (MIPEC) strategy for accelerating the synthesis of metal organic frameworks at room temperature

Metal organic frameworks(MOFs) are a kind of promising materials in many applications,while the fast and controllable synthesis of MOFs is still challenging.Here,taking HKUST-1 as illustration,a microplasma electrochemistry(MIPEC) strategy was developed to accelerate the synthesis process of MOFs with micro-plasma acting as cathode.Treating the HKUST-1 precursor solution with micro-plasma cathode could not only transfer the electrons into the solution leading to the deprotonation effect,but also generate radical species to trigger and accelerate the nucleation and growth of MOFs at the plasmaliquid interface.Thus,uniform and nanosize MOFs could be prepared within minutes.The obtained MOFs show similar excellent uranium adsorption properties compared with those obtained by other method,with a highly adsorption capability of uranium with 550 mg/g in minutes.The novel MIPEC strategy developed in this work provides an alternative for controllable synthesis of MOFs,and especially has potential application in accelerating traditional organic synthesis.     

Needle-like cobalt phosphide arrays grown on carbon fiber cloth as a binder-free electrode with enhanced lithium storage performance

Cobalt phosphide(CoP) is a promising anode candidate for lithium-ion batteries(LIBs) due to its high specific capacity and low working potential.However,the poor cycling stability and rate performance,caused by low electrical conductivity and huge volume variation,impede the further practical application of CoP anode materials.Herein,we report an integrated binder-free electrode featuring needle-like CoP arrays grown on carbon fiber cloth(CC) for efficient lithium storage.The as-prepared CoP/CC electrode integrates the advantages of 1 D needle-like CoP arrays for efficient electrolyte wettability and fast cha rge transpo rtation,and 3 D CC substrate for superior mechanical stability,flexibility and high conductivity.As a result,the CoP/CC electrode delivers an initial specific capacity of 1283 mAh/g and initial Coulombic effeciencies of 85.4%,which are much higher than that of conventional CoP electrode.Notably,the Co P/CC electrode shows outstanding cycling performance up to 400 cycles at 0.5 A/cm² and excellent rate performance with a discharge capacity of 549 mAh/g even at 5 A/cm².This work demonstrates the great potential of integrated CoP/CC hybrid as efficient bind-free and freestanding electrode for LIBs and future flexible electronic devices.     

改性钛基PbO2电极的制备及其对COD的快速检测

通过制备Ti/α/β-PbO₂、Ti/Ag/β-PbO₂这两种含有不同中间层的钛基二氧化铅电极来探究电催化氧化技术快速测定葡萄糖模拟废水中有机物(COD)含量的可行性。为了评估两种电极的各项性能,首先采用扫描电镜(SEM)、X射线衍射(XRD)对电极进行形貌表征,其次进行电化学性能测试包括线性伏安曲线(LSV)、塔菲尔曲线(Tafel)、循环伏安曲线(CV)以及交流阻抗测量分析。结果表明,Ti/α/β-PbO₂电极表面晶体结构更加均匀,晶粒尺寸偏小,具有更大的电活性表面积。Ti/α/β-PbO₂电极的析氧电位为1.77 V,为·OH的产生提供良好条件。在Tafel、CV测试中,Ti/α/β-PbO₂电极的交换电流密度i₀及比电容C_p分别为0.0995 A·cm^-1、0.004098 F·cm^-1均高于Ti/Ag/β-PbO₂电极,说明Ti/α/β-PbO₂电极的耐腐蚀性以及释放电子的能力优异。最终选用Ti/α/β-PbO₂电极为工作电极。Ti/α/β-PbO₂电极检测COD的最佳条件为：氧化电位1.30 V、电解时间150 s、电解液浓度0.03 mol·L^-1 硝酸钠(NaNO₃)。电化学法与比色消解法测定COD的相关系数可达0.9909,同时具有良好的重现性与相关性,COD的检测范围为0 mg·L^-1 ~ 500 mg·L^-1。在误差允许的范围内可以替代标准的重铬酸钾法,为实现COD的在线快速检测提供参考价值。     

PEMFC阴极催化层结构分析

采用CCS法（catalyst coated substrate）构建铂纳米颗粒（Pt-NPs）和铂纳米线（Pt-NWs）双层催化层结构,分析其对单电池电化学性能的影响。对于富铂/贫铂双层铂纳米颗粒结构,靠近质子交换膜侧的富铂层中致密的铂颗粒结构能促进ORR速率,而靠近气体扩散层一侧的具有更高的孔隙率和平均孔尺寸的贫铂层,有利于反应气体的传输和扩散,当贫富铂层铂载量比为1:2时,单电池测试表现出最优性能,在0.6 V时的电流密度达到了1.05 A·cm^-2,峰值功率密度为0.69 W·cm^-2,较常规单层催化层结构提升了21%。在以Pt-NPs作为基底层时生长Pt-NWs时,得到了梯度分布的双层结构。铂颗粒的存在促进了铂前驱体的还原,并为新形成的铂原子提供了沉积位置。在Pt-NPs基底上生长的Pt-NWs具有更均匀的分布以及更致密的绒毛结构,并且自然形成了一种梯度分布。优化后的Pt-NWs催化层在0.6 V时的电流密度提高了21%。含有双层催化层结构的膜电极具有更高的催化剂利用率,对阴极催化层结构的优化和制备提供了新思路。     

基于硅基硼掺金刚石电极的电化学-原位核磁共振波谱电解池的设计、制备与可行性研究

电化学与核磁共振波谱联用技术（EC-NMR）可以实时监测电化学反应过程,从分子水平阐释反应机理,是一种非常有前景的无损在线检测技术。本文首次报道以硅基硼掺金刚石（Si/BDD）作为工作电极的原位EC-NMR三电极单室电解池的设计和制作。研究表明,由于尺寸12.5 mm × 1.2 mm × 0.5 mm的Si/BDD电极在核磁检测区的体积较小且电极材料厚度较薄,因此该电极对射频场的阻碍较小,对磁场均匀性破坏也相应较小。运用自制的EC-NMR电解池并以经典的对苯二酚（QH ₂）电氧化生成对苯二醌（Q）作为模型体系,原位研究了该电化学反应的整个动态过程。在1.2 V恒电位下电解0.1 mol·L^-1 QH₂ 64分钟,监测到位于6.83 ppm处的Q特征峰逐渐生成,反应过程中核磁谱峰未发生裂分或明显的展宽。结果表明,应用本文所设计并制备的原位EC-NMR电解池,可有效对电化学反应物和产物进行定性、定量分析,将可在后续的电化学原位核磁波谱研究中发挥重要作用。     

An Efficient Novel Electrochemical Sensor for Simultaneous Determination of Vitamin C and Aspirin Based on a PMR/Zn-Al LDH/GCE

A sensitive, low-cost, and simple electrochemical sensor based on Zn−Al layered double hydroxide (Zn−Al LDH) combined with a polymer film of methyl red (PMR) to modify a GCE has been created for the first time. Using cyclic voltammetry (CV), the electrochemical characteristics of the newly fabricated sensor were investigated. The characterised PMR/Zn−Al LDH/GCE shows high electro-catalytic activity towards the vitamin C (AA) and aspirin (ASA) oxidation. Schematic fabrication of PMR/Zn−Al LDH/GCE for the determination of AA or ASA was presented. The new sensor demonstrated superior analytical efficiency for the simultaneous identification of AA and ASA traces in well-spaced anodic peaks, even in the presence of certain intervening species. According to experimental results, the fabricated sensor represented two well-separated oxidation peaks for AA and ASA oxidation with potential difference of 799 mV (vs. Ag/AgCl). The linear dependences of the anodic peak currents of AA and ASA on their concentrations in the ranges of 0.10–53.17 μM are good. The detection limits of AA and ASA at the PMR/Zn−Al LDH/GCE were found to be 1.26 and 1.27 μM, respectively. Meanwhile, the quantification limits of AA and ASA were calculated as 4.21 and 4.25 μM, respectively. On other hand, the limit of detection (LODs) of AA and ASA oxidation were determined to be 0.47 and 0.21 μM, respectively, according to DPV method. The effect of scan rate (100 to 800 mV/s) on the anodic peak currents of AA and ASA was examined. A sensing model mechanism has been suggested and discussed in detail. Finally, the proposed sensor displayed a good reproducibility, stability and selectivity. The developed sensor was eventually used to successfully detect AA and ASA in urine samples.     

Determination of Tedizolid Phosphate Using Graphene Nanocomposite Based Solid Contact Ion Selective Electrode; Green Profile Assessment by Eco-scale and GAPI Approach

Antibiotics determination plays a major role in minimizing antimicrobial resistance starting from quality control of pharmaceutical formulations to therapeutic drug monitoring. Green modified glassy carbon electrode has been developed for determination of tedizolid phosphate; new antibiotic prodrug; in presence of its active metabolite. The graphene transducer interlayer, dispersed with PVC, improved the electrode stability and standard potential reproducibility. Graphene hydrophobicity prevented the water layer formation between the sensing layers that decreased the potential drift down to 267 μV h⁻¹. Electrochemical impedance showed a low resistance value for graphene containing sensor due to its high electron transfer ability.     

Discrimination of Beers by Cyclic Voltammetry Using a Single Carbon Screen-printed Electrode

A fast, simple and costless methodology without sample pre-treatment is proposed for the discrimination of beers. It is based on cyclic voltammetry (CV) using commercial carbon screen-printed electrodes (SPCE) and includes a correction of the signals measured with different SPCE units. Data are submitted to partial least squares discriminant analysis (PLS−DA) and support vector machine discriminant analysis (SVM−DA), which allow a reasonable classification of the beers. Also, CV data from beers can be used to predict their alcoholic degree by partial least squares (PLS) and artificial neural networks (ANN). In general, non-linear methods provide better results than linear ones.     

Development of Pen-type Portable Electrochemical Sensor Based on Au-W Bimetallic Nanoparticles Decorated Graphene-chitosan Nanocomposite Film for the Detection of Nitrite in Water,Milk and Fruit Juices

The development and fabrication of a simple, portable, and sensitive detection tool to precisely monitor nitrite level is of growing importance in electrochemistry research, given the strong interest in the protection of drinking water quality, treatment of wastewater, food production, and control of remediation processes. This work describes the fabrication of a simple, cost-effective, pen-type electrochemical sensor based on bimetallic gold and tungsten nanoparticles electrochemically decorated on graphene-chitosan modified pencil graphite electrode (PGE) for the trace detection of nitrite in real samples. The prepared nanocomposite was characterized using XRD, SEM, and EDS. The electrochemical behavior of the sensor was evaluated by cyclic voltammetry (CV) and impedance electrochemical spectroscopy (EIS). Results revealed that the proposed sensor displayed excellent electrocatalytic activity towards electro-oxidation of nitrite with an irreversible redox reaction. The AuNPs-WNPs@Gr-Chi/PGE sensor exhibited excellent analytical performance with a wide linear range from 10 to 250 μM towards nitrite. The LOD and LOQ were calculated to be 0.12 μM and 0.44 μM, respectively. The designed electrochemical sensor was successfully applied for the detection of nitrite in water, milk, and natural fruit juice samples.     

Voltammetric Analysis of Oxymetazoline Hydrochloride at Zeolite – Modified Carbon Paste Electrode in Micellar Medium

Simple, sensitive, accurate and inexpensive differential pulse (DPV) and square wave (SWV) voltammetric methods utilizing zeolite modified carbon paste electrode (ZMCPE) were developed for the determination of Oxymetazoline hydrochloride (OXM) in nasal drops. Various experimental parameters were optimized using cyclic voltammetry (CV). Calibration curves were linear over the concentration ranges 9.8×10⁻⁸–3.6×10⁻⁶ M and 9.8×10⁻⁶–9×10⁻⁵ M for DPV and SWV, respectively. The DPV method showed a limit of detection (LOD) of 1.04×10⁻⁷ M. The method was applied for the determination of OXM in pharmaceutical formulation with an average recovery of 101.18 % (%RSD=0.41, n=9).