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Electrochemical Sensing (electrochemical + sensing)
Selected AbstractsElectrochemical Sensing of Thiocyanate Using Gold Electrodes Modified with an Underpotentially Deposited Silver MonolayerELECTROANALYSIS, Issue 2 2010Christopher Abstract Gold electrodes modified by underpotential deposition to expose a layer of silver atoms on their surfaces were used to measure thiocyanate concentrations in aqueous solutions. When exposed to thiocyanate, the ion adsorbs onto the modified electrode and causes changes in the electrochemical properties of the silver adlayer. Coulometric measurement of the fraction of the silver adlayer that remains in its original state provides a means for determining thiocyanate concentrations. The adsorption of thiocyanate onto the electrode follows a first-order process with a rate constant of ca. 440,L/mol s that defines its concentration/time response. [source] Dendritic Silver/Silicon Dioxide Nanocomposite Modified Electrodes for Electrochemical Sensing of Hydrogen PeroxideELECTROANALYSIS, Issue 17 2008Peixi Yuan Abstract A novel biosensor for hydrogen peroxide was prepared by immobilizing horseradish peroxidase (HPR) on newly synthesized dendritic silver/silicon dioxide nanocomposites, which were coated on a glassy carbon electrode. The modified electrode was characterized with XPS, SEM, and electrochemical methods. This biosensor showed a very fast amperometric response to hydrogen peroxide with a linear range from 0.7 to 120,,M, a limit of detection of 0.05,,M and a sensitivity of 1.02,mA mM,1 cm,2. The Michaelis-Menten constant of the immobilized HRP was estimated to be 0.21,mM, indicating a high affinity of the HRP to H2O2 without loss of enzymatic activity. The preparation of the proposed biosensor was convenient, and it showed high sensitivity and good stability. [source] Direct Electrochemical Sensing and Detection of Natural Antioxidants and Antioxidant Capacity in Vitro SystemsELECTROANALYSIS, Issue 22 2007Antonio, Javier Blasco Abstract This review highlights the role of electrochemical approaches in the sensing of antioxidants and their antioxidant capacity with especial attention to the analytical possibilities of electrochemistry in the direct evaluation of antioxidant capacity exhibited by food and biological samples due to the termed dietary, natural or biological antioxidants (mainly polyphenols, and vitamins C and E). The analytical potency of the electrochemistry is comprehensively stated and the selected results found in the literature are summarized and discussed critically. The main electrochemical approaches used have been cyclic voltammetry (CV) and flow injection analysis with amperometric detection (FIA-ED). In addition, miniaturization is going to break new frontiers in the evaluation of antioxidant activity. [source] Electrochemical Sensing of ExplosivesELECTROANALYSIS, Issue 4 2007Joseph Wang Abstract This article reviews recent advances in electrochemical sensing and detection of explosive substances. Escalating threats of terrorist activities and growing environmental concerns have generated major demands for innovative field-deployable tools for detecting explosives in a fast, sensitive, reliable and simple manner. Field detection of explosive substances requires that a powerful analytical performance be coupled to miniaturized low-cost instrumentation. Electrochemical devices offer attractive opportunities for addressing the growing explosive sensing needs. The advantages of electrochemical systems include high sensitivity and selectivity, speed, a wide linear range, compatibility with modern microfabrication techniques, minimal space and power requirements, and low-cost instrumentation. The inherent electroactivity of nitroaromatic, nitramine and nitroester compounds makes them ideal candidates for electrochemical detection. Recent activity in various laboratories has led to the development of disposable sensor strips, novel electrode materials, submersible remote sensors, and electrochemical detectors for microchip (,Lab-on-Chip') devices for on-site electrochemical detection of explosive substances. The attractive behavior of these electrochemical monitoring systems makes them very promising for addressing major security and environmental problems. [source] Fluorescent and Electrochemical Sensing of Polyphosphate Nucleotides by Ferrocene Functionalised with Two ZnII(TACN)(pyrene) ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2010Zhanghua Zeng Dr. Abstract The [Fcbis{ZnII(TACN)(Py)}] complex, comprising two ZnII(TACN) ligands (Fc=ferrocene; Py=pyrene; TACN=1,4,7-triazacyclononane) bearing fluorescent pyrene chromophores linked by an electrochemically active ferrocene molecule has been synthesised in high yield through a multistep procedure. In the absence of the polyphosphate guest molecules, very weak excimer emission was observed, indicating that the two pyrene-bearing ZnII(TACN) units are arranged in a trans -like configuration with respect to the ferrocene bridging unit. Binding of a variety of polyphosphate anionic guests (PPi and nucleotides di- and triphosphate) promotes the interaction between pyrene units and results in an enhancement in excimer emission. Investigations of phosphate binding by 31P,NMR spectroscopy, fluorescence and electrochemical techniques confirmed a 1:1 stoichiometry for the binding of PPi and nucleotide polyphosphate anions to the bis(ZnII(TACN)) moiety of [Fcbis{ZnII(TACN)(Py)}] and indicated that binding induces a trans to cis configuration rearrangement of the bis(ZnII(TACN)) complexes that is responsible for the enhancement of the pyrene excimer emission. Pyrophosphate was concluded to have the strongest affinity to [Fcbis{ZnII(TACN)(Py)}] among the anions tested based on a six-fold fluorescence enhancement and 0.1,V negative shift in the potential of the ferrocene/ferrocenium couple. The binding constant for a variety of polyphosphate anions was determined from the change in the intensity of pyrene excimer emission with polyphosphate concentration, measured at 475,nm in CH3CN/Tris-HCl (1:9) buffer solution (10.0,mM, pH,7.4). These measurements confirmed that pyrophosphate binds more strongly (Kb=(4.45±0.41)×106,M,1) than the other nucleotide di- and triphosphates (Kb=1,50×105,M,1) tested. [source] Structured Nucleic Acid Probes for Electrochemical DevicesELECTROANALYSIS, Issue 19 2009Rebeca Miranda-Castro Abstract The use of nucleic acid with a specific sequence and a highly ordered secondary structure such as hairpins, quadruplexes and pseudoknots as biological recognition elements and switches in biosensors is rapidly increasing because of their improved features (e.g. selectivity) when compared with the traditional linear probes. Owing to the novelty, a critical outlook of their characteristics and a compilation of the latest advances are lacking. This article describes the potential of those nucleic acids probes whose molecular recognition ability relies on a conformational change (e.g. folding/unfolding mechanism) in electrochemical sensing. It provides an overview of the toolbox of assays using these probes for genosensors and aptasensors, highlighting its performance characteristics and the prospects and challenges for biosensor design. [source] Electrochemical Sensing of ExplosivesELECTROANALYSIS, Issue 4 2007Joseph Wang Abstract This article reviews recent advances in electrochemical sensing and detection of explosive substances. Escalating threats of terrorist activities and growing environmental concerns have generated major demands for innovative field-deployable tools for detecting explosives in a fast, sensitive, reliable and simple manner. Field detection of explosive substances requires that a powerful analytical performance be coupled to miniaturized low-cost instrumentation. Electrochemical devices offer attractive opportunities for addressing the growing explosive sensing needs. The advantages of electrochemical systems include high sensitivity and selectivity, speed, a wide linear range, compatibility with modern microfabrication techniques, minimal space and power requirements, and low-cost instrumentation. The inherent electroactivity of nitroaromatic, nitramine and nitroester compounds makes them ideal candidates for electrochemical detection. Recent activity in various laboratories has led to the development of disposable sensor strips, novel electrode materials, submersible remote sensors, and electrochemical detectors for microchip (,Lab-on-Chip') devices for on-site electrochemical detection of explosive substances. The attractive behavior of these electrochemical monitoring systems makes them very promising for addressing major security and environmental problems. [source] Modulation of the Communication between Redox Centers in a Tris(ferrocene)-tren Ligand by Complexation of Lanthanide IonsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2003Marie Heitzmann The tripodal ligand L built on the tren platform and bearing three chemically equivalent ferrocene units was prepared and characterized. Electrochemical investigations indicate that electrostatic communication occurs between the three ferrocene groups in L, which leads to the observation of two distinct voltammetric waves. The electrochemical communication between the three ferrocene moieties is disrupted in 1:1 (L:M3+) type complexes formed between L and Y3+ or Eu3+ metal cations and their electrochemical response tends towards that of a single three-independent-electrons oxidation wave. Modulation of the electrochemical properties of L in the presence of lanthanide ions might be exploited with a view to their electrochemical sensing in organic and aqueous media. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] | ||||||||||