Voltammetric analysis of epinephrine using glassy carbon electrode modified with nanocomposite prepared from Co-Nd bimetallic nanoparticles, alumina nanoparticles and functionalized multiwalled carbon nanotubes

Herein, we investigated the electrochemical behaviour of fMWCNTs decorated with Co-Nd bimetallic nanoparticles and alumina nanoparticles (Co-Nd/Al2O3@fMWCNTs). The nanocomposites were synthesised using simple mechanical mixing and characterised by FT-IR, XRD, UV-visible studies, SEM, TEM and EDAX. Moreover, the crystalline size of the synthesised nanoparticles was also calculated using XRD data (Debye-Scherer formula) and was found in the nm range. The electrochemical behaviour of epinephrine (EP) was examined in the presence of Co-Nd/Al2O3@fMWCNTs nanocomposite modified glassy carbon electrode (GCE) using various electrochemical techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and chronocoulometry. Among all the above-mentioned techniques, the DPV response of the modified Co-Nd/Al2O3@fMWCNTs/GCE under optimal circumstances revealed a dual linear range (0.2 to 4000 µM and 4000 to 14,000 µM) and LOD of 0.015 µM (S/N = 3). The sensitivities were determined to be 0.00323 µAµM-1 and 0.0004 µAµM-1 in 0.2 to 4000 µM and 4000 to 14,000 µM concentration ranges. Using chronocoulometry, the surface coverage of Co-Nd/Al2O3@fMWCNTs/GCE was calculated to be 1.37 × 10-8 mol cm-2. The fabricated Co-Nd/Al2O3@fMWCNTs/GCE demonstrated remarkable repeatability, with an RSD of 0.09%, and storage stability of 3 weeks, with 89.6% current retention. Lastly, it was found that Co-Nd/Al2O3@fMWCNTs/GCE worked well for EP analysis in a variety of biological fluids.

Enhanced Electrochemical Conductivity of Surface-Coated Gold Nanoparticles/Copper Nanowires onto Screen-Printed Gold Electrode

Electrochemical application has been widely used in the study of biosensors. Small biomolecules need a sensitive sensor, as the transducer that can relay the signal produced by biomolecule interactions. Therefore, we are improvising a sensor electrode to enhance electrochemical conductivity for the detection of small DNA molecule interaction. This work describes the enhanced electrochemical conductivity studies of copper nanowires/gold nanoparticles (CuNWs/AuNPs), using the screen-printed gold electrode (SPGE). The AuNPs were synthesized using the Turkevich method as well as characterized by the high-resolution transmission electron microscopy (HRTEM) and ultraviolet-visible (UV-Vis) analysis for the particle size and absorption nature, respectively. Further, the surface morphology and elemental analysis of a series of combinations of different ratios of CuNWs-AuNPs-modified SPGE were analyzed by field emission scanning electron microscopy (FESEM) combined with an energy dispersive X-ray (EDX). The results indicate that the nanocomposites of CuNWs-AuNPs have been randomly distributed and compacted on the surface of SPGE, with AuNPs filling the pores of CuNWs, thereby enhancing its electrochemical conductivity. The cyclic voltammetry (CV) method was used for the evaluation of SPGE performance, while the characterization of the electrochemical conductivity of the electrode modified with various concentrations of AuNPs, CuNWs, and different volumes of dithiopropionic acid (DTPA) has been conducted. Of the various parameters tested, the SPGE modified with a mixture of 5 mg/mL CuNWs and 0.25 mM AuNPs exhibited an efficient electrochemical conductivity of 20.3 µA. The effective surface area for the CuNWs-AuNPs-modified SPGE was enhanced by 2.3-fold compared with the unmodified SPGE, thereby conforming the presence of a large active biomolecule interaction area and enhanced electrochemical activity on the electrode surface, thus make it promising for biosensor application.

Voltammetric determination of uric acid using multiwall carbon nanotubes coated-poly(4-amino-3-hydroxy naphthalene sulfonic acid) modified glassy carbon electrode

In this study, an electrochemical sensor based multiwalled carbon nanotubes (MWCNTs)-poly (4-amino-3-hydroxy naphthalene sulfonic acid) modified glassy carbon electrode (MWCNTs/poly (AHNSA)/GCE) was developed for the determination of uric acid (UA). The composite electrode was prepared first by electropolymerization of the monomer (AHNSA) on GCE using cyclic voltammetry within the potential range of -0.8 V to +2.0 V vs Ag/AgCl for 15 cycles followed by drop coating of MWCNTs solution on the surface of poly (AHNSA)/GCE. Under optimal conditions, MWCNTs/poly (AHNSA)/GCE showed a linear current response with UA concentrations in the range of 1 × 10-6 to 1 × 10-4 M with R2 = 0.9972. The sensor exhibited low detection limit with a value of 0.024 μM. The sensors have been applied to successfully quantify UA in urine samples.

Immobilized aptamer on gold electrode senses trace amount of aflatoxin M1

An electrochemical aptasensor for detection of trace amounts of aflatoxin M1 was developed. This required immobilization of aptamer on screen printed gold electrode comprising of working electrode, counter electrode and reference electrode and was achieved by sequentially layering dithiodipropionic acid, streptavidin and biotinylated-tetraethylene glycol-aptamer. Immobilization of aptamer was monitored by cyclic voltammetry. Peak current in square wave voltammogram was inversely related to logarithmic concentration of aflatoxin M1. Dynamic range of sensor was 1-105 ppt aflatoxin M1. Sensor can be regenerated by treating electrode with 10% sodium dodecyl sulfate or 40 mM tris-HCl (pH 8.0) containing 10 mM ethylenediaminetetraacetic acid and 0.02% tween-20.

Utilization of a new gold/Schiff-base iron(iii) complex composite as a highly sensitive voltammetric sensor for determination of epinephrine in the presence of ascorbic acid

A new voltammetric sensor based on an iron(iii) Schiff-base complex/Au composite is synthesized and applied for the in vitro detection of epinephrine.