Simulation of edge effects in electroanalytical experiments by orthogonal collocation—VI. Cyclic voltammetry at ultramicroelectrode ensembles

Facile and ultra-sensitive voltammetric electrodetection of Hg2+ in aqueous media using electrodeposited AuPtNPs/ITO

In this study, we have investigated the use of electrodeposited Au-Pt nanoparticles (AuPtNPs) on indium tin oxide (ITO) for the detection of Hg²⁺ heavy ions in water samples. The mechanism of AuPtNP electrocrystallization on ITO glass in an aqueous solution containing 0.5 mM HAuCl₄ + 0.5 mM H₂PtCl₆ is described for the first time. The nucleation mechanism of monometallic AuNPs on ITO was found to be progressive; however, a transition from progressive to instantaneous was observed for bimetallic AuPtNPs at elevated overpotentials. The modified ITOs were then assessed for the electrodetection of Hg²⁺ in aqueous media. It was shown by differential pulse voltammetry (DPV) that the sensitivity of the constructed AuPtNPs/ITO electrode toward Hg²⁺ was about 2.08 μA nM^-1. An approximate detection limit of 4.03 nM Hg²⁺ was achieved, which is below the permissible level of 30.00 nM Hg²⁺ in drinking water, according to the World Health Organization (WHO). Characterization of AuPt nanostructures was carried out by X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM), and different electrochemical techniques (cyclic voltammetry (CV), chronoamperometry, and electrochemical impedance spectroscopy (EIS)). Our results indicate a good potential of a facile and robust electrochemical assembly for on-site detection of heavy metals in water samples.

A review of the advanced developments of electrochemical sensors for the detection of toxic and bioactive molecules

The recent developments made regarding the novel, cost-effective, and environmentally friendly nanocatalysts for the electrochemical sensing of biomolecules, pesticides, nitro compounds and heavy metal ions are discussed in this review article.

Total phenol analysis of weakly supported water using a laccase-based microband biosensor

The monitoring of phenolic compounds in wastewaters in a simple manner is of great importance for environmental control. Here, a novel screen printed laccase-based microband array for in situ, total phenol estimation in wastewaters and for water quality monitoring without additional sample pre-treatment is presented. Numerical simulations using the finite element method were utilized for the characterization of micro-scale graphite electrodes. Anodization followed by covalent modification was used for the electrode functionalization with laccase. The functionalization efficiency and the electrochemical performance in direct and catechol-mediated oxygen reduction were studied at the microband laccase electrodes and compared with macro-scale electrode structures. The reduction of the dimensions of the enzyme biosensor, when used under optimized conditions, led to a significant improvement in its analytical characteristics. The elaborated microsensor showed fast responses towards catechol additions to tap water - a weakly supported medium - characterized by a linear range from 0.2 to 10 μM, a sensitivity of 1.35 ± 0.4 A M(-1) cm(-2) and a dynamic range up to 43 μM. This enhanced laccase-based microsensor was used for water quality monitoring and its performance for total phenol analysis of wastewater samples from different stages of the cleaning process was compared to a standard method.

Graphene oxide-based electrochemical sensor: a platform for ultrasensitive detection of heavy metal ions

Facile functionalization of graphene oxide sheets on gold surface results in complexation-enhanced electrochemical detection of heavy metal ions, shown here for Pb²⁺, Cu²⁺ and Hg²⁺, with improved detection limits by two orders of magnitude relative to the control electrode.

Sonochemically fabricated microelectrode arrays for use as sensing platforms

The development, manufacture, modification and subsequent utilisation of sonochemically-formed microelectrode arrays is described for a range of applications. Initial fabrication of the sensing platform utilises ultrasonic ablation of electrochemically insulating polymers deposited upon conductive carbon substrates, forming an array of up to 70,000 microelectrode pores cm(-2). Electrochemical and optical analyses using these arrays, their enhanced signal response and stir-independence area are all discussed. The growth of conducting polymeric "mushroom" protrusion arrays with entrapped biological entities, thereby forming biosensors is detailed. The simplicity and inexpensiveness of this approach, lending itself ideally to mass fabrication coupled with unrivalled sensitivity and stir independence makes commercial viability of this process a reality. Application of microelectrode arrays as functional components within sensors include devices for detection of chlorine, glucose, ethanol and pesticides. Immunosensors based on microelectrode arrays are described within this monograph for antigens associated with prostate cancer and transient ischemic attacks (strokes).

Electrochemical characteristics of an interdigitated microband electrode array of boron-doped diamond film

An microband electrode array (MBEA) of a boron-doped diamond (BDD) film was prepared by using the hot-filament chemical vapor deposition (HF-CVD) technique and microfabrication process with a standard photolithography technique. Electrochemical properties of a single MBEA (S-MBEA) and interdigitated MBEA (I-MBEA) of BDD film were studied by cyclic voltammetry (CV) analysis. Charge transfer characteristics were examined by electrochemical impedance spectra (EIS) analysis. A ferri–ferrocyanide redox system was chosen to act as the probe of one-electron transfer processes. The redox reaction was controlled by linear diffusion-limited transport at S-MBEA and quasi-steady-state non-linear diffusion at I-MBEA. A relation between current limit at I-MBEA and sweep rate was obtained with a correlation coefficient greater than 0.93. Hemispherical diffusion was primary at I-MBEA of BDD surface. There were two time constants for the S-MBEA and one time constant for the I-MBEA in the redox system.