Fabrication and electrochemical behavior of single-walled carbon nanotube/graphite-based electrode

Studies on Square Wave and Cyclic Voltammetric Behavior of 1,2- and 1,4-Dihydroxybenzenes and Their Derivatives in Acetic Acid, Ethyl Acetate and Mixtures of the Two

An electrochemical investigation of 1,2- and 1,4-dihydroxybenzenes was carried out with platinum macro- and microelectrodes using square wave and cyclic voltammetry techniques. Furthermore, the effect of the two solvents-acetic acid and ethyl acetate-was compared. When using square wave voltammetry, signals only appeared at lower frequencies and only when the supporting electrolyte was in excess, as expected due to the relatively low permittivity of the used solvents. The behavior of hydroquinone and catechol did not differ significantly from that of their derivatives (dihydroxybenzaldehydes, dihydroxybenzoic acids and 2',5'-dihydroxyacetophenone). When the cyclic voltammetric experiments using a microelectrode were extended to higher anodic potentials, electrode fouling was very significant in ethyl acetate after the potential region where steady-state oxidation to the corresponding quinone occurs. The substituent effect was not significant here either, which was proven by using different functional groups in different positions. In contrast, the position had a dramatic influence on the susceptibility to electropolymerization, as 1,2-dihydroxybenzenes-independent of the nature of the substituent on the benzene ring-deactivated the electrode, while 1,4-dihydroxybenzenes did not, possibly due to the different solubilities of the polymers formed from the primary oxidation product (quinones). A user-friendly analytical procedure is also proposed that uses an electropolymerization reaction and does not require frequent cleaning of the electrode via polishing, which is required usually especially with a microelectrode.

Assembly and electroanalytical performance of Prussian blue/polypyrrole composite nanoparticles synthesized by the reverse micelle method

We report on the characterization, assembly and electroanalytical performance of Prussian blue/polypyrrole (PBPPy) composite nanoparticles synthesized by the reverse micelle method. Scanning electron microscopy suggests the formation of nanosized PBPPy particles with diameters between 40 and 50 nm. Optical absorption confirms that the particles are composed of Prussian blue (PB) and polypyrrole. PB and PBPPy nanoparticles were anchored onto the surface of cysteine-modified Au electrodes. Cyclic voltammetry experiments show that PB- or PBPPy-modified electrodes exhibit intrinsic electrochemical properties and a high electrocatalytic activity towards H2O2. PBPPy-modified electrodes exhibit a higher sensitivity to H2O2 than PB-modified electrodes. A linear calibration curve in the concentration range 0.99 μM-8.26 mM H2O2 is constructed with a detection limit of 0.23 μM at a signal-to-noise ratio of 3. Excellent stability is observed for PBPPy-composite-nanoparticle-modified electrodes even in a pH 6 phosphate buffer solution with a high H2O2 concentration (0.99 mM). Glutaraldehyde and [Formula: see text] were also employed to immobilize glucose oxidase for the development of PBPPy-based biosensors. The results show that PBPPy composite nanoparticles can be used to develop oxidase-based biosensors.