Showing papers on "Amperometry published in 2019"

Stalling behaviour of chloride ions: A non-enzymatic electrochemical detection of α-Endosulfan using CuO interface

Abstract: Excessive and unsafe usage of pesticides lead to adverse effect on human beings, plants, animals and aquatic life. Endosulfan, categorized as class-I pesticide by World Health Organization, is a highly toxic pesticide, which is currently being used across countries although it has been banned. In this context, a non-enzymatic electrochemical sensor with copper oxide interface has been developed to detect α-endosulfan in water samples. Hydrothermal synthesized CuO microspheres were characterized using X-ray Diffractometer, Scanning Electron Microscope and X-ray Photoelectron Spectrometer. CuO micro-interface modified gold working electrode along with Pt counter electrode and Ag/AgCl reference electrode were employed to carry out Differential Pulse Voltammetry (DPV) and amperometry studies to detect the presence of α-endosulfan in water. The stalling behaviour of chloride ions present in α-endosulfan in reducing the current intensity confirmed the presence and concentration of α-endosulfan. The impedance variation for the varying concentration of α-endosulfan confirmed the proposed sensing mechanism. The sensor showed a linear range of 4–20 nM, and sensitivity of 0.03 μA nM−1. The relative standard deviation for the repeatability and reproducibility was 1.69%. The stability of the developed biosensor was 80.93% for 15 days.

A nanocomposite prepared from platinum particles, polyaniline and a Ti3C2 MXene for amperometric sensing of hydrogen peroxide and lactate.

Abstract: A nanocomposite consisting of platinum particles, polyaniline and Ti3C2 MXene (Pt/PANI/MXene) was used to modify a screen-printed carbon electrode (SPCE) to obtain sensors for hydrogen peroxide and lactate. This nanocomposite was characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) to determine the physical morphologies and the nanocomposite elements. The modified electrode exhibited the improved current response towards hydrogen peroxide (H2O2) compared with an unmodified electrode and provided a low detection limit of 1.0 μM. When lactate oxidase was immobilized on the modified electrode, the electrode responded to lactate via the H2O2 generated in the enzymatic reaction. The lactate assay was performed by amperometry at a constant potential of +0.3 V (vs. Ag/AgCl). The linear range was found to be from 0.005 to 5.0 mM with a detection limit of 5.0 μM for lactate. Ultimately, this biosensor was used for the determination of lactate in milk samples with high stability and reliability.

Nanostructured MXene-based biomimetic enzymes for amperometric detection of superoxide anions from HepG2 cells

Abstract: A novel MXene-based biomimetic enzyme was synthesized using adenosine triphosphate (ATP) as a template to modify a Mn3(PO4)2 nanostructure on Mxene-Ti3C2 nanosheets. The resulting composite was used as an electrode material in an electrochemical sensor for superoxide anion (O2•−). It displays excellent catalytic properties which is attributed to the synergistic effects of the two-dimensional conductive substrate and the Mn3(PO4)2 nanoparticles. The addition of ATP results in the formation of a porous and ordered nanostructure of Mn3(PO4)2. This facilitates the electron transfer between O2•− and electrode. The sensor, best operated at 0.75 V (vs. Ag/AgCl), displays a rapid amperometric response with a detection limit of 0.5 nM and an analytical range that extends from 2.5 nM to 14 μM. Conceivably, it has potential in the detection of O2•− released by living cells.

A sensitive and selective graphene/cobalt tetrasulfonated phthalocyanine sensor for detection of dopamine

Abstract: Electrochemical dopamine-sensing surfaces were fabricated by deposition of graphene sheets modified with cobalt tetrasulfonated phthalocyanine on glassy carbon electrodes (CoTSPc/Gr-GC) using differential pulse amperometry. Differential pulse stripping voltammetry was used to detect dopamine (DA) and the influence of pH value, scan rate, accumulation potential and time as well as dopamine concentration on the performance of CoTSPc/Gr-GC electrodes was investigated. The modified electrodes were successfully used as sensors for the selective and high sensitive determination of DA in presence of high concentrations of ascorbic acid (AA) and uric acid (UA) with a detection limit of 0.87 nM over the dynamic linear range of 20 nM to 220 nM.

A core-shell molybdenum nanoparticles entrapped f-MWCNTs hybrid nanostructured material based non-enzymatic biosensor for electrochemical detection of dopamine neurotransmitter in biological samples.

Abstract: Dopamine (DA) is a critical neurotransmitter and has been known to be liable for several neurological diseases. Hence, its sensitive and selective detection is essential for the early diagnosis of diseases related to abnormal levels of DA. In this study, we reported novel molybdenum nanoparticles self-supported functionalized multiwalled carbon nanotubes (Mo NPs@f-MWCNTs) based core-shell hybrid nanomaterial with an average diameter of 40–45 nm was found to be the best for electrochemical DA detection. The Mo NPs@f-MWCNTs hybrid material possesses tremendous superiority in the DA sensing is mainly due to the large surface area and numerous electroactive sites. The morphological and structural characteristics of the as-synthesized hybrid nanomaterial were examined by XRD, Raman, FE-SEM, HR-TEM, EDX. The electrochemical characteristics and catalytic behavior of the as-prepared Mo NPs@f-MWCNTs modified screen-printed carbon electrode for the determination of DA were systematically investigated via electrochemical impedance spectroscopy, cyclic voltammetry, and amperometry. The results demonstrate that the developed DA biosensor exhibit a low detection limit of 1.26 nM, excellent linear response of 0.01 µM to 1609 µM with good sensitivity of 4.925 µA µM−1 cm−2. We proposed outstanding appreciable stability sensor was expressed to the real-time detection of DA in the real sample analysis of rat brain, human blood serum, and DA hydrochloride injection.

Novel sensitive amperometric hydrogen peroxide sensor using layered hierarchical porous α-MoO3 and GO modified glass carbon electrode

Abstract: The nonenzymatic electrochemical H2O2 sensor based on molybdenum oxides has been rarely reported. In this work, a nonenzymatic electrode, hierarchical porous α-MoO3 and graphene oxide decorated glass carbon electrode (α-MoO3/GO/GCE) used for H2O2 electrochemical detection, is firstly fabricated by simple layer-by-layer assemble method, in which the α-MoO3 is derived by one-step pyrolysis of the regular organic-inorganic hybrid [(H2L)2(Mo8O26)]n [HL = N-(pyridin-3-ylmethyl)pyridine- 3-amine] single crystal precursor. The wedge-shaped morphology of the material is accumulated by micro-slices which comprise of nanosheets and small particles with average size of 25 nm. Meanwhile, different types of meso- and macro-pores with the size distributions of 4–6, 20–35 and 100–150 nm are observed, respectively. The α-MoO3/GO/GCE sensor based on the optimal ratio of 1:1 shows excellent electrocatalytic H2O2 property at room temperature. It displays the broad linear detection from 0.92 μM to 2.46 mM and the high sensitivity is calculated to be 391.39 μA mM−1 cm−2 with a low detection limit of 0.31 μM (S/N = 3). The sensor can achieve 95% steady state current within 5 s and present well stability, reproducibility and anti-interference during H2O2 detection. Furthermore, the sensor is applied for the determination of H2O2 in human serum samples. The excellent performances of this sensor are related to the hierarchical porous structure of α-MoO3 and its synergistic effect with GO.

Synthesis of Calixarene-Capped Silver Nanoparticles for Colorimetric and Amperometric Detection of Mercury (HgII, Hg0)

Abstract: Calixarene-functionalized water dispersible silver nanoparticles have been synthesized and characterized on the basis of UV-vis, IR, X-ray diffraction, and high-resolution transmission electron microscopy analysis, and their sensing properties toward metal ions have been investigated. They selectively detect Hg2+ and Hg0 in solution and vapor phases, respectively, with distinct color change. Interference study with mixture of metal ions revealed no interference from any other metal ions used in this study. Their mechanism of detection involved Hg2+-aided displacement of calixarene moiety from the surface of the functionalized nanoparticles, followed by the formation of Ag-Hg amalgam due to interaction of Hg2+ with Ag0 and also the formation of assembly of Ag0 nanoparticles by dipole-dipole interaction of the bare-surfaced nanoparticles. Electrochemical study revealed that with the aid of functionalized nanoparticles, Hg2+ can be detected amperometrically with high sensitivity. The detection limits obtained for Hg2+ by UV-vis study and amperometry are 0.5 nM (0.1 ppb) and 10 nM (2 ppb), respectively. The new material has been used to detect Hg2+ in aqueous real sample and Hg0 in soil sample.

H2O2 biosensor consisted of hemoglobin-DNA conjugate on nanoporous gold thin film electrode with electrochemical signal enhancement.

Abstract: In this research, we developed electrochemical biosensor which was composed of hemoglobin (Hb)-DNA conjugate on nanoporous gold thin film (NPGF) for hydrogen peroxide (H2O2) detection. For the first time, Hb and DNA was conjugated as a sensing platform for uniform orientation of Hb on electrode. The newly developed Hb-DNA conjugate was designed to prevent Hb from aggregation on electrode. DNA hybridization of Hb-DNA conjugate and complementary DNA (cDNA) on NPGF electrode induced uniformly assembled biosensor. Furthermore, NPGF electrode fabrication method was introduced to the increment of the surface area. To confirm the conjugation of Hb-DNA conjugate, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and ultraviolet–visible spectroscopy (UV–VIS) were used. Formation of the NPGF electrode was verified by scanning electron microscope (SEM). Atomic force microscopy (AFM) was operated for the confirmation of Hb-DNA immobilization on electrode. The electrochemical property of fabricated electrode was investigated by cyclic voltammetry (CV). Also, H2O2 sensing performance of fabricated electrode was investigated by amperometric i-t curve technique. This sensor showed a wide linear range from 0.00025 to 5.00 mM and a correlation coefficient of R2 = 0.9986. The detection limit was 250 nM. Proposed biosensor can be utilized as a sensing platform for development of biosensor.

Electrochemical detection of glucose at physiological pH using gold nanoparticles deposited on carbon nanotubes

Abstract: There is currently considerable interest in the development of non–enzymatic glucose sensors and gold is one of the noble metals that enables the oxidation of glucose. Gold nanoparticles with a mean diameter of 7.5 nm were deposited onto the walls of functionalised carbon nanotubes to give a gold loading of 2.0% by weight. This composite was dispersed and cast onto glassy carbon and carbon screen printed electrodes. These electrodes were then used to detect glucose in a neutral phosphate buffer solution, corresponding to physiological pH. Using constant potential amperometry, a linear calibration curve was obtained with a sensitivity of 2.77 ± 0.14 μA/mM, a limit of detection, LOD, of 4.1 μM and a linear region extending to 25 mM. This sensor showed very good selectivity in the presence of ascorbic acid, galactose and fructose, but interference was observed in the presence of uric acid. This interference was eliminated by applying a Nafion® film to the composite electrodes. Due to a lower diffusion of glucose across the Nafion® barrier, the sensitivity of the Nafion® coated composite was reduced to 0.55 ± 0.03 μA/mM and the LOD was increased to 10.0 μM. However, a linear response between 0.1 mM and 25 mM was obtained, which covers the normal and elevated levels of glucose in blood. These sensors showed very good stability when stored in air and it was also possible to re–use the sensors.

Highly monodisperse Pd-Ni nanoparticles supported on rGO as a rapid, sensitive, reusable and selective enzyme-free glucose sensor

Abstract: In this work, highly monodispersed palladium-nickel (Pd-Ni) nanoparticles supported on reduced graphene oxide (rGO) were synthesized by the microwave-assisted methodology. The synthesized nanoparticles were used for modification of a glassy carbon electrode (GCE) to produce our final product as PdNi@rGO/GCE, which were utilized for non-enzymatic detecting of glucose. In the present study, electrochemical impedance spectroscopy (EIS), chronoamperometry (CA) and, cyclic voltammetry (CV) methods were implemented to investigate the sensing performance of the developed glucose electrode. The modified electrode, PdNi@rGO/GCE, exhibited very noticeable results with a linear working range of 0.05–1.1 mM. Moreover, an ultralow detection limit of 0.15 μM was achieved. According to the results of amperometric signals of the electrodes, no significant change was observed, even after 250 h of operation period. In addition, the highly monodisperse PdNi@rGO/GCE was utilized to electrochemical detection of glucose in real serum samples. In light of the results, PdNi@rGO/GCE has shown an excellent sensing performance and can be used successfully in serum samples for glucose detection and it is suitable for practical and clinical applications.

Mechanism of Histamine Oxidation and Electropolymerization at Carbon Electrodes

Abstract: Histamine plays an important role in neuromodulation and the biological immune response. Although many electrochemical methods have been developed for histamine detection, the mechanism of its redox reaction has not been directly investigated. Here, we studied the mechanism of histamine oxidation at carbon electrodes and used that mechanistic information to design better fast-scan cyclic voltammetry (FSCV) methods for histamine. Using amperometry, cyclic voltammetry (CV), and X-ray photoelectron spectroscopy (XPS), we demonstrate that histamine oxidation requires a potential of at least +1.1 V vs Ag/AgCl. We propose that histamine undergoes one-electron oxidation on an imidazole nitrogen that produces a radical. The radical species dimerize and continue to undergo oxidation, leading to electropolymerization, which fouls the electrode. CV shows a peak at 1.3 V that is pH dependent, consistent with a one-proton, one-electron oxidation reaction. This mechanism is confirmed using 1- and 3-methylhistamine, which do not electropolymerize, compared to Nα-methylhistamine, which does. XPS also revealed a nitrogen-containing product adsorbed on the electrode surface after histamine oxidation. For FSCV detection of histamine at carbon-fiber microelectrodes, histamine oxidation was adsorption-controlled, and the anodic peak was observed at +1.2 V on the backward scan because of the rapid scan rate. However, the oxidation fouled the electrode and convoluted the FSCV temporal response; therefore, we implemented Nafion coating to alleviate the electrode fouling and preserve the time response of FSCV. Knowing the mechanism of histamine oxidation will facilitate design of better electrochemical methods for real-time monitoring of histamine.

Electrospun CuO-ZnO nanohybrid: Tuning the nanostructure for improved amperometric detection of hydrogen peroxide as a non-enzymatic sensor.

Abstract: Hydrogen peroxide (H2O2) is a by-product of some biochemical processes which is catalyzed by enzymes such as glucose oxidase (GOx), cholesterol oxidase (ChoOx), etc and its overproduction in living cells can trigger cancer growth and various diseases. Therefore, H2O2 sensing is of great importance in the determination of diseases as well as industries and environmental health plans. We produced ZnO-CuO nanofibers by electrospinning method for non-enzymatic electrochemical H2O2 sensing. The sensing properties of the carbon paste electrode (CPE) modified with ZnO (0.3 wt%)/CuO (0.7 wt%) nanofibers (named as ZnO3-CuO7) for detection of H2O2 were explored in phosphate-buffered saline (PBS) at pH ∼ 7.4 solution. The ZnO3-CuO7 nanofiber exhibited the lowest charge transfer resistance and the highest electrocatalytic performance among other modified electrodes for detection of H2O2 and considered as an optimized sample. The effect of scan rate and H2O2 concentration in the reduction process were also investigated by cyclic voltammetry (CV) and the mechanism for the electrochemical reaction of H2O2 at the surface of the optimized electrode was studied. The diffusion coefficient of H2O2 and the catalytic rate constant were evaluated by chronoamperometry as 1.65 × 10−5 cm2 s−1 and 6 × 103 cm3 mol−1 s−1, respectively. Furthermore, amperometric detection of H2O2 with a low detection limit of 2.4 µM and a wide linear range of 3 to 530 µM were obtained. Meanwhile, the optimized electrode displayed no recognizable response towards some biomolecules such as ascorbic acid, uric acid, dopamine and glucose. The obtained results confirmed that the modified electrode shows high sensitivity and selectivity as a H2O2 biosensor with improved reproducibility and stability.