scholarly journals Electrochemical Oxidation of Monosaccharides at Nanoporous Gold with Controlled Atomic Surface Orientation and Non-Enzymatic Galactose Sensing

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5632
Author(s):  
Yasuhiro Mie ◽  
Shizuka Katagai ◽  
Masiki Ikegami
Keyword(s):  
Electrochemical Oxidation ◽  
Electrochemical Sensors ◽  
Oxidation Potential ◽  
Chloride Ions ◽  
Nanoporous Gold ◽  
Calibration Plot ◽  
Current Response ◽  
Positive Potential ◽  
Physiological Conditions ◽  
Atomic Surface

Non-enzymatic saccharide sensors are of great interest in diagnostics, but their non-selectivity limits their practical diagnostic abilities. In this study, we investigated the electrochemical oxidation of monosaccharides at nanoporous gold (NPG) catalysts with different contributions of surface crystallographic orientations. Fructose elicited no clear electrochemical response, but glucose, galactose, and mannose produced clear oxidative current. The onset potentials for oxidation of these saccharides depended on the surface atomic structure of the NPG. The oxidation potential was approximately 100 mV less positive at the Au(100)-enhanced NPG than at the Au(111)-enhanced NPG. Furthermore, the voltammetric responses significantly differed among the saccharides. Galactose was oxidized at less positive potential and exhibited a higher current response than the other saccharides. This tendency was enhanced in the presence of chloride ions. These features enabled the selective and sensitive detection of galactose at an NPG electrode without enzymes under physiological conditions. A linear range of 10 μM to 1.8 mM was obtained in the calibration plot, which was comparable to those in previously reported enzymatic galactose sensors. Thus, we demonstrated that controlling the crystallographic orientation on the nanostructured electrode surface is useful in developing electrochemical sensors.

scholarly journals MnO2@Reduced Graphene Oxide Nanocomposite-Based Electrochemical Sensor for the Simultaneous Determination of Trace Cd(II), Zn(II) and Cu(II) in Water Samples

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 517
Author(s):  
Siyamthanda Hope Mnyipika ◽  
Tshimangadzo Saddam Munonde ◽  
Philiswa Nosizo Nomngongo
Keyword(s):  
Heavy Metals ◽  
Electrochemical Sensor ◽  
Simultaneous Determination ◽  
Rapid Detection ◽  
Electrochemical Sensors ◽  
Simultaneous Detection ◽  
Cyclic Voltammograms ◽  
Current Response ◽  
Mno2 Nanoparticles

The rapid detection of trace metals is one of the most important aspect in achieving environmental monitoring and protection. Electrochemical sensors remain a key solution for rapid detection of heavy metals in environmental water matrices. This paper reports the fabrication of an electrochemical sensor obtained by the simultaneous electrodeposition of MnO2 nanoparticles and RGO nanosheets on the surface of a glassy carbon electrode. The successful electrodeposition was confirmed by the enhanced current response on the cyclic voltammograms. The XRD, HR-SEM/EDX, TEM, FTIR, and BET characterization confirmed the successful synthesis of MnO2 nanoparticles, RGO nanosheets, and MnO2@RGO nanocomposite. The electrochemical studies results revealed that MnO2@RGO@GCE nanocomposite considerably improved the current response on the detection of Zn(II), Cd(II) and Cu(II) ions in surface water. These remarkable improvements were due to the interaction between MnO2 nanomaterials and RGO nanosheets. Moreover, the modified sensor electrode portrayed high sensitivity, reproducibility, and stability on the simultaneous determination of Zn(II), Cd(II), and Cu(II) ions. The detection limits of (S/N = 3) ranged from 0.002–0.015 μg L−1 for the simultaneous detection of Zn(II), Cd(II), and Cu(II) ions. The results show that MnO2@RGO nanocomposite can be successfully used for the early detection of heavy metals with higher sensitivity in water sample analysis.

scholarly journals Electrochemical Detection of Phenanthrene Using Nickel Oxide Doped PANI Nanofiber Based Modified Electrodes

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Omolola E. Fayemi ◽  
Abolanle S. Adekunle ◽  
Eno E. Ebenso
Keyword(s):  
Nickel Oxide ◽  
Square Wave Voltammetry ◽  
Modified Electrodes ◽  
Oxidation Potential ◽  
Current Response ◽  
Modified Glassy Carbon Electrode ◽  
Square Wave ◽  
Wave Voltammetry ◽  
Doped Polyaniline ◽  
Uv Visible

A nickel oxide doped polyaniline nanofibers (PANI-NiO) based electrochemical sensor was constructed for detection of phenanthrene. Successful synthesis of PANI-NiO nanocomposite was confirmed with techniques such as SEM, XRD, EDX, FTIR, and UV-visible spectroscopy. The electrocatalytic oxidation of phenanthrene on PANI-NiO on modified glassy carbon electrode (GCE-PANI-NiO) was studied using cyclic voltammetry, square wave voltammetry, and impedance spectroscopy and discussed. Results showed that detection of phenanthrene was enhanced by the nanostructure of PANI-NiO film. The square wave voltammetry analysis shows a very low detection limit of 0.732 pM for phenanthrene with the linear range of 7.6 pM–1.4 × 10−11 M. The Tafel value of 227 mVdec−1suggests adsorption of phenanthrene oxidation intermediates on the GCE-PANI-NiO electrode. The GCE-PANI-NiO modified electrodes gave better performance towards phenanthrene in terms of current response, oxidation potential, current recovery, stability, and resistance to electrode fouling effects.

scholarly journals Low Cost Electrochemical Sensors for Silver, Chloride, Bromide and Iodide Ions

1970 ◽  
Vol 6 (6) ◽  
pp. 33-36 ◽  
Author(s):  
Raja Ram Pradhananga ◽  
Armila Rajbhandari Nyachhyon
Keyword(s):  
Electrochemical Sensors ◽  
Silver Chloride ◽  
Low Cost ◽  
Selectivity Coefficient ◽  
Chloride Ions ◽  
Equimolar Mixture ◽  
Potentiometric Selectivity ◽  
Iodide Ion ◽  
Silver Sulphide ◽  
Potentiometric Selectivity Coefficient

Low cost all solid state pressed pellet Ag+, halides and sulphide sensitive electrodes based on silver sulphide were fabricated. The electrodes have been tested and results compare favorably with commercial electrodes. Pure Ag2S electrode with internal silver metal contact was found to follow Nernstian equation from 1 x 10-1 to 1 x 10-5 M of silver ion with slope equal to 59.8 mV per decade change in concentration of Ag+ - ion. Electrodes fabricated from equimolar mixture of Ag2S and Ag - halide was found to be sensitive to the respective halide and silver ions. Iodide ion selective electrode prepared from a equimolar mixture of Ag2S and AgI was found to be selective to iodide ion with negligible interference from bromide and chloride ions. The potentiometric selectivity coefficient Kpot I,Br, Kpot I,Cl were found to be 1.77x10-2 and 7.94x10-3 respectively. All these electrodes were found to be selective to Ag+ ion with negligible interference with Kpot Ag, Hg equal to 1 x 10-5 Hg++ ion with selectivity coefficient. Keywords: Ion selective electrodes; Potentiometric selectivity coefficient; Silver sulphide.   DOI: 10.3126/sw.v6i6.2631 Scientific World, Vol. 6, No. 6, July 2008 33-36

scholarly journals Effect of Chloride Ions on the Electrochemical Oxidation of Chalcopyrite at 340 °C and 21 MPa

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1071
Author(s):  
Luying Wang ◽  
Heping Li ◽  
Qingyou Liu ◽  
Liping Xu ◽  
Lei Zha ◽  
...  
Keyword(s):  
Electrochemical Oxidation ◽  
Protective Property ◽  
Electrochemical Impedance ◽  
Chloride Ions ◽  
Ionic Diffusion ◽  
Copper Extraction ◽  
Dissolution Mechanism ◽  
Oxidation Layer ◽  
X Ray ◽  
Nacl Concentration

Understanding the oxidative mechanisms of chalcopyrite in various hydrothermal fluids is of great significance to improve copper extraction and to model the geochemical cycling of copper, iron, and sulfur. This paper investigated the effect of NaCl on the electrochemical oxidation of chalcopyrite at 340 °C and 21 MPa using polarization curves, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. The experimental results showed that NaCl can promote chalcopyrite leaching. As NaCl concentration increases, the protective property of the oxidation layer degraded. In the absence of NaCl, the oxidation layer that consisted of CuSn, (n ≥ 1), probably with some Fe2O3 and Fe(OH)3 and also in the presence of NaCl, Fe2O3, is the principal oxidation product. More rapid ionic diffusion and further chemical reaction contributed to the improvement of chalcopyrite dissolution with increasing NaCl concentration. A dissolution mechanism is proposed in this paper to explain the chalcopyrite leaching processes which is dependent on NaCl concentration.

scholarly journals Copper(I)-Catalyzed Click Chemistry as a Tool for the Functionalization of Nanomaterials and the Preparation of Electrochemical (Bio)Sensors

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2379 ◽  
Author(s):  
P. Yáñez-Sedeño ◽  
A. González-Cortés ◽  
S. Campuzano ◽  
J. M. Pingarrón
Keyword(s):  
Electrochemical Sensors ◽  
Functional Integration ◽  
Future Directions ◽  
Physiological Conditions ◽  
Electrode Surfaces ◽  
Wide Range ◽  
High Yields ◽  
By Products ◽  
Powerful Strategy

Proper functionalization of electrode surfaces and/or nanomaterials plays a crucial role in the preparation of electrochemical (bio)sensors and their resulting performance. In this context, copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) has been demonstrated to be a powerful strategy due to the high yields achieved, absence of by-products and moderate conditions required both in aqueous medium and under physiological conditions. This particular chemistry offers great potential to functionalize a wide variety of electrode surfaces, nanomaterials, metallophthalocyanines (MPcs) and polymers, thus providing electrochemical platforms with improved electrocatalytic ability and allowing the stable, reproducible and functional integration of a wide range of nanomaterials and/or different biomolecules (enzymes, antibodies, nucleic acids and peptides). Considering the rapid progress in the field, and the potential of this technology, this review paper outlines the unique features imparted by this particular reaction in the development of electrochemical sensors through the discussion of representative examples of the methods mainly reported over the last five years. Special attention has been paid to electrochemical (bio)sensors prepared using nanomaterials and applied to the determination of relevant analytes at different molecular levels. Current challenges and future directions in this field are also briefly pointed out.

Enhanced electrocatalytic activity of cobalt phthalocyanines when “clicked” to graphene oxide nanosheets

2019 ◽  
Vol 23 (07n08) ◽  
pp. 828-840 ◽  
Author(s):  
Lekhetho S. Mpeta ◽  
Tebello Nyokong
Keyword(s):  
Graphene Oxide ◽  
Catalytic Activity ◽  
Benzene Ring ◽  
Electrocatalytic Activity ◽  
Electrochemical Sensors ◽  
Limit Of Detection ◽  
Oxidation Potential ◽  
Graphene Oxide Nanosheets ◽  
Ring Complex ◽  
Good Catalytic Activity

Alkyne-terminated Co phthalocyanine (CoPc) derivatives are linked to reduced graphene oxide nanosheets (GONS) via click chemistry and the conjugates are used for the electrocatalytic oxidation of 2-mercaptoethanol. CoPc derivatives where the alkyne group is separated from the Pc ring by an aliphatic and benzene ring (complex 3) showed the best catalytic activity (in terms of oxidation potential) in comparison to when only aliphatic chains were employed without the benzene ring (complex 2) and when there were no substituents (complex 1). The anodic oxidation of 2-mercaptoethanol on 3-GONS (linked) occurred at the least positive oxidation potential (-0.22 V vs. Ag|AgCl). 3-GONS (linked) was found to have the highest sensitivity with the lowest limit of detection of 0.08 [Formula: see text]M. When the CoPc derivative and GONS were not linked but placed sequentially on the electrode, the electrocatalytic activity (in terms of LOD) was poorer than when linked. The electrodes modified with CoPc clicked to GONS are highly promising electrochemical sensors in terms of stability, sensitivity, good catalytic activity and ease of fabrication.

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