Voltammetric Biosensor Based on Nitrogen-doped Ordered Mesoporous Carbon for Detection of Organophosphorus Pesticides in Vegetables

2018 ◽  
Vol 15 (1) ◽  
pp. 92-100 ◽  
Author(s):  
Beiqing Long ◽  
Lin Tang ◽  
Bo Peng ◽  
Guangming Zeng ◽  
Yaoyu Zhou ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Electrochemical Impedance ◽  
Tap Water ◽  
Organophosphorus Pesticides ◽  
Modified Electrodes ◽  
Agricultural Products ◽  
Self Assembled Monolayer ◽  
Detection Range ◽  
Pesticides Residues ◽  
Self Assembled

Background: Pesticides residues in agricultural products have posed a serious threat to food safety and human health, so it is necessary to develop a rapid and accurate method to detect pesticide in the environment. N-OMC with excellent electroconductivity, high biocompatibility and the functional amino group that can be covalently attached to the enzyme can be applied to construct a sensitive and stable acetylcholinesterase biosensor for rapid and accurate detection of organophosphorus pesticides with the help of L-cysteine self-assembled monolayer and AuNPs. Methods: Transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and nitrogen adsorption measurements are used to characterize materials. Electrochemical impedance spectroscopy and cyclic voltammetry are used to study the surface features of modified electrodes. Differential pulse voltammetric is used to measure the peak current of modified electrodes. GC-MS is applied to verify the reliability of the prepared biosensor for organophosphorus pesticides detection. Results: N-OMC was synthesized and applied to constructed stable and sensitive acetylcholinesterase biosensors. The combination of N-OMC, L-cysteine self-assembled monolayer and AuNPs to modify the electrode surface has greatly improved the conductivity of biosensor and provided a stable platform for acetylcholinesterase immobilization. The linear detection range of paraoxon was from 3 to 24 nM with a lower detection limit of 0.02 nM. Conclusion: The biosensor exhibited satisfactory reproducibility, repeatability and stability, and was successfully employed to determine the paraoxon in vegetables as well as tap water samples, providing a promising tool for rapid and sensitive detection of organophosphorus pesticides in agricultural products.

Comparative Study of Field Emission-Scanning Electron Microscopy and Atomic Force Microscopy to Assess Self-assembled Monolayer Coverage on Any Type of Substrate

1999 ◽  
Vol 5 (6) ◽  
pp. 413-419 ◽  
Author(s):  
Bernardo R.A. Neves ◽  
Michael E. Salmon ◽  
Phillip E. Russell ◽  
E. Barry Troughton
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Atomic Force Microscopy ◽  
Comparative Study ◽  
Field Emission ◽  
Self Assembled Monolayer ◽  
Force Microscopy ◽  
Atomic Force ◽  
Self Assembled ◽  
Scanning Electron

Abstract: In this work, we show how field emission–scanning electron microscopy (FE-SEM) can be a useful tool for the study of self-assembled monolayer systems. We have carried out a comparative study using FE-SEM and atomic force microscopy (AFM) to assess the morphology and coverage of self-assembled monolayers (SAM) on different substrates. The results show that FE-SEM images present the same qualitative information obtained by AFM images when the SAM is deposited on a smooth substrate (e.g., mica). Further experiments with rough substrates (e.g., Al grains on glass) show that FE-SEM is capable of unambiguously identifying SAMs on any type of substrate, whereas AFM has significant difficulties in identifying SAMs on rough surfaces.

scholarly journals Electrochemistry Study of Permselectivity and Interfacial Electron Transfers of a Branch-Tailed Fluorosurfactant Self-Assembled Monolayer on Gold

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2998 ◽  
Author(s):  
Shanshan Li ◽  
Qingying Luo ◽  
Zhiqing Zhang ◽  
Guanghui Shen ◽  
Hejun Wu ◽  
...  
Keyword(s):  
Self Assembly ◽  
Electrochemical Impedance ◽  
Click Reaction ◽  
Hydration Shell ◽  
Self Assembled Monolayer ◽  
Tunneling Mechanism ◽  
Assembly Technique ◽  
Hydration Resistance ◽  
Self Assembled ◽  
Electron Transfers

We investigated the permselectivity and interfacial electron transfers of an amphiphilic branch-tailed fluorosurfactant self-assembled monolayer (FS-SAM) on a gold electrode by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The FS-SAM was prepared by a self-assembly technique and a “click” reaction. The barrier property and interfacial electron transfers of the FS-SAM were also evaluated using various probes with different features. The FS-SAM allowed a higher degree of permeation by small hydrophilic (Cl− and F−) electrolyte ions than large hydrophobic (ClO4− and PF6−) ones. Meanwhile, the redox reaction of the Fe(CN)63− couple was nearly completely blocked by the FS-SAM, whereas the electron transfer of Ru(NH3)63+ was easier than that of Fe(CN)63−, which may be due to the underlying tunneling mechanism. For hydrophobic dopamine, the hydrophobic bonding between the FS-SAM exterior fluoroalkyl moieties and the hydrophobic probes, as well as the hydration resistance from the interior hydration shell around the oligo (ethylene glycol) moieties, hindered the transport of hydrophobic probes into the FS-SAM. These results may have profound implications for understanding the permselectivity and electron transfers of amphiphilic surfaces consisting of molecules containing aromatic groups and branch-tailed fluorosurfactants in their structures.

Charge Transfer Property of Self-Assembled Viologen Derivative by Electrochemical Quartz Crystal Microbalance Response

2006 ◽  
Vol 6 (11) ◽  
pp. 3657-3660 ◽  
Author(s):  
Dong-Yun Lee ◽  
A. K. M. Kafi ◽  
Sang-Hyun Park ◽  
Young-Soo Kwon
Keyword(s):  
Charge Transfer ◽  
Quartz Crystal Microbalance ◽  
Quartz Crystal ◽  
Modified Electrodes ◽  
Electrochemical Quartz Crystal Microbalance ◽  
Frequency Change ◽  
Self Assembled Monolayer ◽  
Transfer Property ◽  
Redox Peak ◽  
Self Assembled

Viologen modified electrodes have been extensively investigated with quartz crystal microbalance (QCM), which has been known as a nano-gram order mass detector, because of their highly reversible electrochemical properties, especially the first reduction-oxidation cycle of V2+ ↔ V•+. The purpose of this work was to study the charge transfer characteristics of self-assembled monolayer (SAM) by changing electrolyte solutions where the cations and anions are different. The redox peak currents were nearly equal charges during redox processes and showed an excellent linear interrelation between the scan rates and second redox peak currents. The charge transfer of self-assembled viologen monolayer was determined by the mass change during the cyclic voltammetry (CV). The total frequency change was about 17.8 Hz, 19.6 Hz, 9.5 Hz, and 8.4 Hz. From this data, we could know the transferred mass was about 19.0 ng, 20.9 ng, 10.2 ng, and 9.0 ng. Finally, the electrochemical quartz crystal microbalance (EQCM) has been employed to monitor the electrochemically induced adsorption of self-assembled monolayer.

scholarly journals Development of a DNA Sensor Based on Alkanethiol Self- Assembled Monolayer-Modified Electrodes

Sensors ◽  
2005 ◽  
Vol 5 (6) ◽  
pp. 344-363 ◽  
Author(s):  
Óscar Loaiza ◽  
Susana Campuzano ◽  
María López-Berlanga ◽  
María Pedrero ◽  
José Pingarrón
Keyword(s):  
Modified Electrodes ◽  
Dna Sensor ◽  
Self Assembled Monolayer ◽  
Self Assembled

scholarly journals Electrochemical Detection of C-Reactive Protein in Human Serum Based on Self-Assembled Monolayer-Modified Interdigitated Wave-Shaped Electrode

Sensors ◽  
2019 ◽  
Vol 19 (24) ◽  
pp. 5560 ◽  
Author(s):  
Somasekhar R. Chinnadayyala ◽  
Jinsoo Park ◽  
Young Hyo Kim ◽  
Seong Hye Choi ◽  
Sang-Myung Lee ◽  
...  
Keyword(s):  
Human Serum ◽  
Electrochemical Impedance ◽  
Electrode Array ◽  
C Reactive Protein ◽  
Self Assembled Monolayer ◽  
X Ray ◽  
Reactive Protein ◽  
Relative Standard ◽  
Label Free Detection ◽  
Self Assembled

An electrochemical capacitance immunosensor based on an interdigitated wave-shaped micro electrode array (IDWµE) for direct and label-free detection of C-reactive protein (CRP) was reported. A self-assembled monolayer (SAM) of dithiobis (succinimidyl propionate) (DTSP) was used to modify the electrode array for antibody immobilization. The SAM functionalized electrode array was characterized morphologically by atomic force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDX). The nature of gold-sulfur interactions on SAM-treated electrode array was probed by X-ray photoelectron spectroscopy (XPS). The covalent linking of anti-CRP-antibodies onto the SAM modified electrode array was characterized morphologically through AFM, and electrochemically through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The application of phosphate-buffered saline (PBS) and human serum (HS) samples containing different concentrations of CRP in the electrode array caused changes in the electrode interfacial capacitance upon CRP binding. CRP concentrations in PBS and HS were determined quantitatively by measuring the change in capacitance (ΔC) through EIS. The electrode immobilized with anti-CRP-antibodies showed an increase in ΔC with the addition of CRP concentrations over a range of 0.01–10,000 ng mL−1. The electrode showed detection limits of 0.025 ng mL−1 and 0.23 ng mL−1 (S/N = 3) in PBS and HS, respectively. The biosensor showed a good reproducibility (relative standard deviation (RSD), 1.70%), repeatability (RSD, 1.95%), and adequate selectivity in presence of interferents towards CRP detection. The sensor also exhibited a significant storage stability of 2 weeks at 4 °C in 1× PBS.

Concentration-Controlled and Phytic Acid-Assisted Synthesis of Self-Assembled LiFePO4 as Cathode Materials for Lithium-Ion Battery

NANO ◽  
2020 ◽  
Vol 15 (01) ◽  
pp. 2050003
Author(s):  
Yin Li ◽  
Keyu Zhang ◽  
Zhengjie Chen ◽  
Yunke Wang ◽  
Li Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Diffusion Coefficient ◽  
Electrochemical Performance ◽  
Phytic Acid ◽  
Cathode Materials ◽  
Electrochemical Impedance ◽  
Lithium Ion ◽  
Precursor Concentration ◽  
Phosphorus Source ◽  
Self Assembled

The olivine LiFePO4 with various morphologies and different growth lattice planes was prepared by a controllable hydrothermal method with changing precursor concentration and using phytic acid as phosphorus source. The microstructure, crystal orientation and electrochemical performance of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and charge–discharge tests. The results show that the morphologies of all samples change from spindle-like to hierarchical plate-like and then to long plate-like shape, and the main exposed facets transform from (100) to (001). This indicates that the precursor concentration and phytic acid play important roles in exposing facets and controlling the morphology of LiFePO4. In order to illustrate these phenomena, a reasonable assembly process is provided and the formation is explained. Li ion diffusion coefficient along [100] and [001] directions was calculated by using electrochemical impedance spectroscopy (EIS). The results show that the diffusion coefficient of (100) facet is higher than that of (001) facet, indicating a good electrochemical performance for (100) facet. In addition, the capacity test is carried out, which also confirms the above results. With the precursor concentration of 0.5[Formula: see text]M, the obtained LiFePO4 with self-assembled hierarchical structure, smaller size and (100) facet shows the best electrochemical performance: 162.1[Formula: see text]mAh/g at 0.1[Formula: see text]C and 112.4[Formula: see text]mAh/g at 10[Formula: see text]C. Using phytic acid as phosphorus source and controlling precursor concentration to prepare high performance LiFePO4 open up a new prospect for the production of cathode materials for lithium ion batteries.

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