A diazonium-functionalized silver electrode for the sensitive amperometric detection of p-nitrophenol in water over a wide range of concentrations.

This work presents a novel approach for the electrochemical detection of p-nitrophenol (pNP) focusing on the development of a simple and efficient strategy to overcome pNP adsorption. The proposed method involves the functionalization of a silver (Ag) electrode with an electrografted, thin diazonium film. After characterization by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry, the as-functionalized electrode allowed a wide linear detection range to be established in aqueous solutions, spanning from 1 to 500 µM pNP. This outcome indicates that the diazonium film effectively addresses any issues related to adsorption with good repeatability and reproducibility. Furthermore, the sensor's analytical performances were evaluated yielding a sensitivity and a limit of detection of 0.3819 µA cm-2 µM-1 and 600 nM, respectively. The sensor was also found to exhibit a good selectivity towards pNP and phenolic compounds and was successfully tested on a real water sample.

EPR spectroelectrochemical investigation of guanine radical formation and environment effects.

Guanine radical detection was carried out by a new convenient and efficient method coupling electron paramagnetic resonance spectroscopy and indirect electrooxidation of guanine in different biological environments, from the free nucleotide to several types of DNA substrates. Compared to the widely used photoirradiation method, this method appeared more selective in the choice of the electrochemical mediator. Carried out in presence of a ruthenium mediator and PBN as spin trap, this method revealed two types of EPR spectra depending of the environment of the guanine radical. Both EPR spectra show the trapping of the neutral guanine radical G(-H)(•) obtained after fast deprotonation of the radical cation G(•+). However, they differ by the atom where the trapped radical is centered. This difference highlights the structural dependency of the environment on the nature of the radical formed. This work gave the evidence of an innovative method to detect in situ the guanine radical.

Unexpected effect of copper ions on electrochemical impedance behaviour of self-assembled alkylaminethiol monolayer.

Effect of copper ions on the electrochemical behaviour of an alkylaminethiol monolayer has been studied by electrochemical impedance spectrosocpy. RAMAN experiment shows the effective adsorption of receptor onto the gold surfaces. The study of Nyquist plot shows that the gold/monolayer/electrolyte interface can be described by a serial combination of two R, CPE electrical circuits. In the presence of increasing amounts of copper, the Nyquist plots at low frequencies were modified showing an increase of the resistance of the second R, CPE electrical circuit. Moreover, this increase of resistance varies linearly with the amounts of copper ions added in solution from 10(-8) mol·L(-1) to 10(-5) mol·L(-1).

Electrochemical impedance spectroscopy to study physiological changes affecting the red blood cell after invasion by malaria parasites.

The malaria parasite, Plasmodium falciparum, invades human erythrocytes and induces dramatic changes in the host cell. The idea of this work was to use RBC modified electrode to perform electrochemical impedance spectroscopy (EIS) with the aim of monitoring physiological changes affecting the erythrocyte after invasion by the malaria parasite. Impedance cell-based devices are potentially useful to give insight into cellular behavior and to detect morphological changes. The modelling of impedance plots (Nyquist diagram) in equivalent circuit taking into account the presence of the cellular layer, allowed us pointing out specific events associated with the development of the parasite such as (i) strong changes in the host cell cytoplasm illustrated by changes in the film capacity, (ii) perturbation of the ionic composition of the host cell illustrated by changes in the film resistance, (iii) releasing of reducer (lactic acid or heme) and an enhanced oxygen consumption characterized by changes in the charge transfer resistance and in the Warburg coefficient characteristic of the redox species diffusion. These results show that the RBC-based device may help to analyze strategic events in the malaria parasite development constituting a new tool in antimalarial research.

Redox sensing of anions in pure aqueous environment by ferrocene-containing 4,4'-bipyridinium-based receptors and polymer films.

Selective voltammetric sensing of ATP(2-) anions in water was achieved using ferrocene-viologen based redox active receptors and related polymer films.