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Electrochemical Transducers for Biosensors
Published in Sibel A. Ozkan, Bengi Uslu, Mustafa Kemal Sezgintürk, Biosensors, 2023
Ali A. Ensafi, Parisa Nasr-Esfahani
In voltammetric techniques, the voltage is scanned, and the current that is a result of analyte electrochemical reduction or oxidation at the working electrode is measured. Actually, the voltage is applied between the working electrode and the reference electrode, while the current is measured between the counter electrode and the working electrode. A voltammogram showed the obtained current vs. voltage. The current response is proportional to the analyte concentration and is usually a peak or a plateau (2). Depending on the type of applied voltage, there are various voltammetric methods, including polarography, cyclic voltammetry, linear sweep voltammetry, differential pulse voltammetry, square-wave voltammetry, stripping voltammetry, and AC voltammetry. In the following, we will discuss the most widely used of these methods in the field of electrochemical biosensors.
Porous Materials and Electrochemistry
Published in Antonio Doménech-Carbó, Electrochemistry of Porous Materials, 2021
As previously noted, electrochemical methods are based on recording of the response of an electrode—in contact with an electrolyte—to an electrical excitation signal. Depending on the characteristics of the excitation potential signal applied to the working electrode and the measured signal response, one can distinguish different electrochemical techniques. Voltammetry consists of the recording of current (I) which flows between the working electrode and an auxiliary electrode vs. potential (E) which is applied between a working electrode and a reference electrode. In conventional three-electrode arrangements, a potentiostat controls the potential so that the current flows almost exclusively between the working electrode and the auxiliary electrode while a small, practically negligible current is passing through the reference electrode.
Voltammetry, Polarography
Published in Ernő Pungor, A Practical Guide to Instrumental Analysis, 2020
Voltammetry is an electroanalytical measuring technique which can be used for the quantitative determination of reducible or oxidizable components. The technique is based on the study of current vs. potential relationships. In voltammetry the working electrode is polarizable, i.e., by changing its potential according to a special time program, in a certain range the potential of the electrode will change according the applied potential program. The reference electrodes used in voltammetry are nonpolarizable, i.e., their potential remains constant in the course of the voltage change in the measuring cell. (For ensuring the controlled working electrode potential generally a third, so-called auxiliary electrode is also used.) In the course of the potential change components present in the solution to be studied can be oxidized or reduced; as a result of these processes current is flowing through the cell. The current vs. potential relationships are called voltammetric curves.
Single-step biogenic synthesis of silver nanoparticles using honeybee-collected pollen
Published in Inorganic and Nano-Metal Chemistry, 2022
Brajesh Kumar, Kumari Smita, Yolanda Angulo, Alexis Debut, Luis Cumbal
Until now, various types of pollen have been used to synthesize MNPs. Turunc et al, synthesized AgNPs using Cupressus sempervirens pollen extract as a reducing and stabilizing agent. They also studied their electrochemical behavior using cyclic voltammetry and square wave voltammetry techniques.[25] Al-Yousef et al. reported the usefulness of bee pollen extract in the preparation of AgNPs and evaluation of their anti-cancer and anti-bacterial activities.[26] In another study, Banu et al. reported biomimetic synthesis of AgNPs and gold nanoparticles using pollen extract from date palm for cytotoxicity on MCF-7 cells.[27] Azizi et al. performed zinc oxide (ZnO) nanoparticle biosynthesis using plant pollen for biomedical applications.[28] Shen et al. reported the preparation of porous silver spheres by reducing the silver-ammonia solution and using rapeseed pollen as novel bio-templates.[29] Hajeb and coworkers prepared 23 nm spherical AgNPs with rapeseed flower pollen extract and evaluated the antioxidant, antiangiogenesis and cytotoxicity against MDA-MB-231, MCF7 and carcinoma cell lines.[30] In another investigation, Khatami et al., describes an extremely simplified method for the synthesis of gold nanoparticles using male pine cone pollen extract as a local natural source and having low toxicity effects on MCF-7 and HUVECs cell lines.[31]
Electrochemical detection and quantification of Reactive Red 195 dyes on graphene modified glassy carbon electrode
Published in Journal of Environmental Science and Health, Part C, 2019
M. Revathi, B. Kavitha, C. Vedhi, N. Senthil Kumar
The electrochemical reduction of this dye has been investigated in aqueous solution using cyclic voltammetry, controlled potential electrolysis and cathodic stripping voltammetry.22 Voltammetric measurements show that Reactive Blue 81 electrooxidation proceeds easier and with higher rate than electrooxidation of Reactive Red 2.23 Qualitative voltammetric determination of reactive dyes is possible down to concentrations of about 10−5 mol/l using DC-polarography. Using rotating solid electrodes (glassy carbon) a detection limit of about 10−4 mol/l can be obtained.24 Cyclic Voltammetry becomes the most widely used technique to acquire qualitative information on electrochemical reactions because of its ability in providing considerable information about the kinetics of the system, number of electron transferred, reversibility of the system as well as adsorption and diffusion characteristics.25
Progress and challenges in electrochemical sensing of volatile organic compounds using metal-organic frameworks
Published in Critical Reviews in Environmental Science and Technology, 2019
Pawan Kumar, Ki-Hyun Kim, Parveen Kumar Mehta, Liya Ge, Grzegorz Lisak
Various types of amperometric sensors have been developed using MOF-based materials (Chen et al., 2016; Zhang, Ji, et al., 2017; Xiao, Xu, Yuan, & Wang, 2017; Deng, Lin, Bo, & Guo, 2017; Gu, Yin, Bo, & Guo, 2018; Yuan et al., 2014). Typically, electrochemical stripping voltammetry is a common analytical technique used to offer excellent sensitivity due to effective pre‐concentration of the analyte at the electrode surface. It is noted that stripping voltammetry could achieve a sensitivity far superior to other amperometric techniques (Gu et al., 2018). Zhang et al. (2015) have successfully prepared a good amperometric sensing platform using cobalt-based MOF with the incorporation of macroporous carbon (MPC). The amperometric sensing platform displayed excellent electrocatalytic ability for the oxidation of hydrazine and reduction of nitrobenzene (Figure 6A). Furthermore, differential pulse voltammetry (DPV) was employed to detect nitrobenzene at Co-MOF–MPC-2–GCE (Figure 6B). A series of DPV curves were obtained for different concentrations of nitrobenzene. As seen from the calibration curve of reduction current (Figure 6C), a good linearity for nitrobenzene was confirmed in the concentration ranges of 0.5–15 μM (sensitivity: 1780 μA μM−1) and 15 to 235 μM (1060 μA μM−1). The LOD was computed as 0.21 μM (S/N = 3). More recently, Gu et al. (2018) successfully prepared an amperometric sensor using a Cr‐based MOF (MIL‐101(Cr))/reduced graphene oxide (rGO) electrocatalyst for detection of metronidazole, a semi-VOC with a boiling point around 400 °C. The linear range for metronidazole can be divided in two parts, e.g., from 0.5 to 200 μM and from 200 to 900 μM. The LOD is 0.24 μM (S/N = 3, n = 10).