Kummari, ShekherKumar, V. SunilGoud, K. YugenderGobi, K. Vengatajalabathy...
10页
查看更多>>摘要：A versatile reusable electrochemical biosensor has been formulated by using colloidal gold nanoparticle (AuNPs) suspension and conducting polymer poly-(3-amino-5-hydroxypyrazole (poly-AHP) modified carbon paste electrode (AuNPs/poly-AHP/CPE) for detection of an important anti-viral drug valacyclovir (VAL). A thin film of poly-AHP incorporated with homogeneous distribution of AuNPs on the surface of carbon paste electrode is fabricated stepwise by applying one by one. An electrochemical potentiodynamic polymerization of AHP was followed by a potentiostatic electrodissolution-induced deposition of AuNPs on poly-AHP. The sensor surface has been characterized by scanning electron microscopy (SEM), energy dispersive X-Ray spectroscopy (EDX), X-ray powder diffraction (XRD) and UV-visible spectroscopy for surface topological/morphological characteristics. Electrochemical efficiency of the present sensor system towards the detection of VAL is explored by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), differential pulse voltammetry (DPV) and hydrodynamic steady-state current-time analysis, and the fabricated AuNPs/poly-AHP/CPE is recognized as a capable sensor system for electrochemical determination of VAL. Applying DPV under optimized conditions, the anodic peak current exhibited a linear relationship against VAL over the range of 5-80 nM with a detection limit of as low as 1.9 nM and an analysis time of 15 s. Under hydrodynamic conditions mimicking flow-cell analysis, the low detection limit was as low as 2.5 nM (S/N > 4) with rapid analysis time of mere 5 s. Selective determination of VAL was performed in the presence of dopamine and serotonin. Practical utility of the AuNPs/poly-AHP film sensor has been demonstrated for the detection of VAL directly from artificial urine, pharmaceutical formulations and diluted human serum with good recovery limits.
Jeong, YohanPark, JoongwonLee, SanghyunOh, Si Hun...
12页
查看更多>>摘要：Iron oxide-carbon nanocomposites modified with organic ligands (L-iron oxide-carbon) were prepared by a hydrothermal process and subsequent thermal treatments for application as lithium-ion battery anode materials. The use of polyacrylic acid as the organic ligand effectively inhibited the agglomeration and additional growth of iron oxide nanoparticles, helping to form the porous composite structure. The molecular weights of the as-employed polymeric organic ligands were further regulated (high-molecular-weight ligands (HMLs) and low-molecular-weight ligands (LMLs) were used) to control the pore structure of the composite. Interestingly, since the pore structure of the composite depended on the molecular weight (or radius of gyration) of the polymeric organic ligand, HML-based composites possessed a larger pore volume and larger pore size than those of the LML-based one. The as-formed HML-iron oxide-carbon composite contained homogeneously distributed iron oxide nanoparticles in the porous graphitic carbon matrix obtained by regulated thermal treatments involving carbonization and oxidation. In the comparative electrochemical (EC) test for the samples (HML-iron oxide-carbon and controls), HML-iron oxide-carbon exhibited superior performance (retained capacity: 835 mAh/g after 100 cycles at 1 A/g; rate capability: 628 mAh/g at 3 A/g) compared to that of the controls (LML-iron oxide-carbon, iron oxide-carbon, iron oxide, and porous carbon). HML-iron oxide-carbon also exhibited an increased capacity of 835 mAh/g at 1 A/g after prolonged cycling (after 100 cycles). This outstanding EC performance of HML-iron oxide-carbon can be attributed to its unique composite structure design obtained by the introduction of HMLs and consecutive thermal treatments.
查看更多>>摘要：Reduced graphene oxide (rGO) has attracted significant attention for electrochemical sensing applications. In this work, rGO was obtained by thermal annealing of electrospun polymeric nanofiber membrane at 500 and 600 degrees C. The XRD patterns reveals the phase and crystalline formation of rGO. The interlayer spacing decreases at higher temperature that indicates the removal of oxygen containing moieties. FTIR spectrum shows the absence of epoxy, carboxyland hydroxylgroups for rGO-600 that resembles the surface feature of rGO. XPS further corroborates the XRD and FTIR results and quantifies the predominant functional groups in rGO-500 and rGO-600 degrees C. The synthesized materials were applied for the electrochemical sensing of dopamine (DA) by cyclic voltammetry. In the case of rGO-500/SPCE, a linear relationship for the DA concentration wasobserved in the range of 0.5 pM to 20 pM with a detection limit of 1.11 pM. Whereas, rGO-600/SPCEalso gave a linear relationship for the DA concentration in the range of 0.5 pM to 20 pM with 1.23 pM detection limit. These electrodes showed good electrocatalytic activity for the oxidation of DA with a minute variation in their detection limit. Therefore, the annealed material rGO can be efficiently used for the quantitative analysis of dopamine after carefully controlling the surface functional groups.
查看更多>>摘要：Due to the excellent intrinsic activity, platinum-based materials are widely used to produce highly efficient electrocatalysts towards oxygen reduction reactions (ORR), but their ultrahigh price and poor stability severely hinder the mass production and further wide application. Alloying Pt with 3d transition metals through galvanic replacement is an effective way to reduce Pt loading based on the premise of outstanding ORR activity. In this work, to fabricate the optimal precursor for subsequent galvanic replacement, a series of carbon-supported Ni samples were firstly prepared by tuning the Ni loading amount and pyrolysis temperature. Then, the highly dispersed PtNi nanoparticles modified carbon nanohybrid (PtNi/C) with low Pt content of 2.29 wt% can be obtained, which exhibits remarkable and durable ORR activity with E-1/2 of 0.841 V vs. RHE via efficient 4e-ORR process in acidic media. Moreover, it should be emphasized that the as-synthesized PtNi/C behaves the impressively high mass activity of 0.57 A/mgPt at 0.8 V, which is 9.4 times that of commercial Pt/C. It is confident that our work can offer constructive suggestions for the design and synthesis of high-performanced electrocatalysts fabricated through galvanic replacement method.
查看更多>>摘要：Healthcare supplements are prime targets to be made into falsified products as they undergo less stringent regulation and can be purchased through online sites. There is an upsurge in the purchase of vitamin C due to the COVID19 pandemic which has made this product a target for falsification. Vitamin C can be available in various oral formulations and thus sample preparation is required prior to analysis. Chromatography and spectroscopy are the most widely used approaches for analysis. Therefore, this study focused on investigating if voltammetry could provide a rapid measurement approach of various formulations (normal, chewable, and effervescent tablets) of vitamin C without the need for any sample analysis. We found that tablet excipients reduce the oxidation peak current and influence the peak shape and oxidation peak potentials. This variation in the oxidation peak potential provided the ability to distinguish between the different oral formulations. Voltammetry provided the ability to conduct repeatable measurements and the solutions of the tablets were stable for 2 days for measurements. In a blinded study, voltammetry was able to identify the concentration of vitamin C present and the type of oral formulation of various falsified samples. Our findings highlight that voltammetry can be a vital technique for the determination of falsified healthcare supplements.
查看更多>>摘要：Conducting polymers are commonly used as precursors for preparing carbon-based catalysts and have been used in electrocatalytic water splitting. However, so far, most of the catalytic materials synthesized with the assistance of high polymer conducting polymers are non-self-supporting and have only a single-function catalytic effect. Therefore, it is an inevitable trend to synthesize a bifunctional self-supported, highly efficient and long-stable water splitting catalyst. Herein, a self-supporting polypyrrole precursor PPy-PW12 was prepared by electrodeposition with phosphotungstic acid as a dopant. In addition, the PPy-PW12 precursor was then calcined. The as-prepared W/Ni3(PO4)2@NC/NF electrocatalyst exhibits admirable HER and OER performances with overpotentials of 48 mV for HER and 236 mV for OER to reach a current density of 10 mA cm-2 in 1.0 M KOH solution. Additionally, when W/Ni3(PO4)2@NC/NF is used in overall water splitting as a bifunctional catalyst, it needs only 1.53 V to deliver a current density of 10 mA cm-2, which is superior to typically integrated Pt/C and RuO2 counterparts. Our work offers a facile strategy to apply W/Ni3(PO4)2@NC/NF as practical bifunctional electrocatalysts for large-scale water splitting.
Barkae, Tesfaye HailemariamZeid, Abdallah M.Quan, ShuaiGilani, Muhammad Rehan Hasan Shah...
6页
查看更多>>摘要：Hexamethylphosphoramide (HMPA) is extensively used in various applications. However, it is categorized as carcinogenic and mutagenic substance that participates in adverse effects on public health. Herein, we developed a new Ru(bpy)32+ electrochemiluminescence (ECL) system for sensitive, cost-effective, rapid, and specific detection of HMPA. The developed ECL sensing platform enabled analysis of HMPA over a wide dynamic range of 0.1 mu M to 1 mM with a detection limit of 0.08 mu M (S/N = 3). The designed ECL sensor exhibited high percentage recoveries (98.0-102.5%) in real samples of lake water and waste water.
Juan Lopez-Garcia, JoseHorno, JoseGrosse, Constantino
4页
查看更多>>摘要：The dependence of the differential capacitance and surface charge density of electrochemical cells on the potential is analysed solving the Poisson-Boltzmann equation avoiding the commonly used infinite solution approximation. We find that the system behavior changes significantly. Instead of growing exponentially without limit with the potential, the surface charge density is limited in a real system by the total ionic content in the solution so that the differential capacitance shows a maximum. This behavior correlates qualitatively with experimental observations only explained to date by taking into account the finite ionic size. Moreover, approximate analytic expressions for the surface charge density and differential surface capacitance, valid when the electric double layer coupling is negligible, are obtained.
查看更多>>摘要：We report on plasmonic imaging of electron transfer at a semiconductor-metal interface by combining principles of surface plasmon resonance imaging (SPRi) and a closed bipolar electrode (CBPE). In the two-cell configuration, one cell was deposited with thin films of semiconductor-based photocatalysts and the other cell without any modification. By this configuration, electron transfer at the semiconductor-metal interface was coupled with interfacial charging in the latter cell, which was read out optically by SPRi. Two different semiconductor-metal interfaces, that were ZnO/Au and TiO2/Au were investigated respectively. Both of their SPR signals increased when light on and decreased when light off. And light intensity increased the corresponding SPR responses. Finally taking advantage of the high-throughput features of SPRi, electron transfer at the two interfaces were visualized simultaneously. This work expands applications of SPRi and provides a new route to investigate electron transfer at semiconductor-metal interfaces.
NSTL
Elsevier