Chemosensors2015, 3(2), 178-189; doi:10.3390/chemosensors3020178 (registering DOI) - published 21 May 2015 Show/Hide Abstract
Abstract: A solid state electrochemiluminescence (ECL) sensor based on Ru(bpy)32+-encapsulated silica nanoparticles (RuNP) covalently immobilised on a screen printed carbon electrode has been developed and characterised. RuNPs were synthesised using water-in-oil microemulsion method, amino groups were introduced on their surface, and they were characterised by transmission electron microscopy. Aminated RuNPs were covalently immobilised on activate screen-printed carbon electrodes to form a solid state ECL biosensor. The biosensor surfaces were characterised using electrochemistry and scanning electron microscopy, which showed that aminated nanoparticles formed dense 3D layers on the electrode surface thus allowing immobilisation of high amount of Ru(bpy)32+. The developed sensor was used for ECL detection of biogenic polyamines, namely spermine, spermidine, cadaverine and putrescine. The sensor exhibited high sensitivity and stability.
Abstract: An alcohol dehydrogenase-based biosensor was prepared and tested for its use to determine ethanol in beer. The biosensor is based on a screen-printed carbon electrode (SPCE) modified by rhodium dioxide and immobilized with a biocatalytic layer containing the enzyme. Function of the enzyme biosensor was tested in model ethanol samples, in which it showed a linear range of 15–120 g∙L−1 with a detection limit of 3.3 g∙L−1 (established as 3σ) and response time of 19 s. In a potential window from –0.2 to +0.45 V, interferences of both ascorbic and uric acids were negligible. Several types of marketed beers of Czech provenance were selected and subjected to measurements under optimized conditions but without any pretreatment of real samples. When compared with the reference method (gas chromatography), the results were in quite good agreement for beers of the pale lager type but higher contents of ethanol were indicated in the samples of dark lager beers.
Abstract: Novel pyrolyzed photoresist carbon electrodes for electroanalytical applications have been produced by photolithographic technology followed by pyrolysis of the photoresist. A study of the determination of Ni(II) dimethylglyoximate (Ni-DMG) through adsorptive cathodic stripping voltammetry at an in situ bismuth-modified pyrolyzed photoresist electrode (Bi-PPCE) is reported. The experimental conditions for the deposition of a bismuth film on the PPCE were optimized. The Bi-PPCE allowed the analysis of trace concentrations of Ni(II), even in the presence of Co(II), which is the main interference in this analysis, with cathodic stripping square wave voltammograms characterized by well-separated stripping peaks. The calculated limits of detection (LOD) were 20 ng∙L−1 for Ni(II) alone and 500 ng∙L−1 in the presence of Co(II). The optimized method was finally applied to the analysis of certified spring water (NIST1640a).
Abstract: Electrodes based on arrays of TiO2 nanowires were prepared by template sol-gel synthesis with the goal of developing a hydrazine photoelectrochemical sensor. Experimental conditions were chosen so that the gelation reaction occurred inside the nanopores of track-etched polycarbonate membranes, with consequent filling with TiO2 nanowires. Different procedures for the removal of the template were examined, in order to obtain arrays of self-standing TiO2 nanowires. The nanowire arrays were bound to fluorine doped tin oxide substrates to produce handy photoelectrodes. The photocurrent recorded with the photoelectrodes in the presence of hydrazine showed significant dependence on the pollutant concentration. The development of a photoelectrochemical sensor for hydrazine detection in water samples, based on this principle, is presented.
Abstract: Nowadays extensive volumes of pesticides are employed for agricultural and environmental practices, but they have negative effects on human health. The levels of pesticides are necessarily restricted by international regulatory agencies, thus rapid, cost-effective and in-field analysis of pesticides is an important issue. In the present work, we propose a butyrylcholinesterase (BChE)-based biosensor embedded in a flow system for organophosphorus pesticide detection. The BChE was immobilized by cross-linking on a screen-printed electrode modified with Prussian Blue Nanoparticles. The detection of paraoxon (an organophosphorus pesticide) was carried out evaluating its inhibitory effect on BChE, and quantifying the enzymatic hydrolysis of butyrylthiocholine before and after the exposure of the biosensor to paraoxon, by measuring the thiocholine product at a working voltage of +200 mV. The operating conditions of the flow system were optimized. A flow rate of 0.25 mL/min was exploited for inhibition steps, while a 0.12 mL/min flow rate was used for substrate measurement. A substrate concentration of 5 mM and an incubation time of 10 min allowed a detection limit of 1 ppb of paraoxon (corresponding to 10% inhibition). The stability of the probe in working conditions was investigated for at least eight measurements, and the storage stability was evaluated up to 60 days at room temperature in dry condition. The analytical system was then challenged in drinking, river and lake water samples. Matrix effect was minimized by using a dilution step (1:4 v/v) in flow analysis. This biosensor, embedded in a flow system, showed the possibility to detect paraoxon at ppb level using an automatable and cost-effective bioanalytical system.
Abstract: Screen-printed electrode (SPE) modified with carbon black nanoparticles (CB) has been tested as a new platform for the stable deposition of caffeic acid (CFA) on the electrode surface. The electrochemical performance from varying the amount of CFA/CB composite has been tested with respect to NADH determination. The electrocatalytic activity of CFA/CB has also been compared with that of SPEs modified by a single component of the coating, i.e., either CFA or CB. Finally, glycerol dehydrogenase, a typical NADH-dependent enzyme, was deposited on the CFA/CB coating in order to test the applicability of the sensor in glycerol determination.