Conductive diamond: synthesis, properties, and electrochemical applications

This review summarizes systematically the growth, properties, and electrochemical applications of conductive diamond.

Electrochemical behavior of chlorogenic acid at a boron-doped diamond electrode and estimation of the antioxidant capacity in the coffee samples based on its oxidation peak

In this study, an electroanalytical methodology for the determination of chlorogenic acid (CGA) was achieved at a boron-doped diamond electrode under adsorptive transfer stripping voltammetric conditions. The values obtained for CGA were used to estimate the antioxidant properties of the coffee sample based on CGA oxidation. By using square-wave stripping mode, the compound yielded a well-defined voltammetric response at +0.49 V with respect to Ag/AgCl in Britton-Robinson buffer at pH 3.0 (after 120 s accumulations at a fixed potential of 0.40 V). At the optimum experimental conditions, linear calibration curve is obtained within the concentration range of 0.25 to 4.0 μg mL⁻¹ with the limit of detection 0.049 μg mL⁻¹ . The developed protocol was successfully applied for the analysis of antioxidant capacity in the coffee products such as Turkish coffee and instant coffee.

Electrochemical incineration of high concentration azo dye wastewater on the in situ activated platinum electrode with sustained microwave radiation

In this study, an in situ microwave activated platinum electrode was developed for the first time to completely incinerate the azo dye simulated wastewater containing methyl orange. The experiments were carried out in a circulating system under atmospheric pressure. Azo bond of methyl orange was partly broken on Pt, certain decoloration was reached, and the total organic carbon was not removed effectively without microwave activation. However, methyl orange was mineralized completely and efficiently on the in situ microwave activated Pt. 2,5-Dinitrophenol, p-nitrophenol, hydroquinone, benzoquinone, maleic and oxalic acids are the main intermediates during degradation of methyl orange. Aromatic products are the main substances leading to the poisoning of Pt and decrease of electrochemical oxidation efficiency, so methyl orange removal can not be carried out thoroughly. However, the intermediates were broke down quickly with in situ microwave activation promoting the mineralization of methyl orange on Pt.

Electrochemical degradation of refractory pollutant using a novel microstructured TiO2 nanotubes/ Sb-doped SnO2 electrode

A novel Sb-doped SnO2 electrode featuring high oxygen evolution potential, excellent electrocatalytic performance, and long stabilitytoward electrochemical degradation of refractory organic pollutants was constructed by designing and regenerating the microstructure of the Ti substrate. Highly ordered TiO2 nanotubes (TiO2-NTs) with three-dimensional microstructure, large specific surface area and space utilization rate could be grown in situ on Ti substrate under controlled conditions, followed by being implanted with Sb-doped SnO2 through a surfactant-assisted, sol-gel method under vacuum environment. The amount of Sb-doped SnO2 and service lifetime for the constructed electrode (TiO2-NTs/SnO2) were 2.4 and 12 times as much asthose for a traditional Sb-doped SnO2 (SnO2) electrode. Moreover, the constructed electrode performed at higher oxygen evolution potential and exhibited superior electrochemical capability to that on SnO2 electrode. Compared with low TOC removal by the SnO2 electrode, the TiO2-NTs/SnO2 electrode could completely mineralize benzoic acid (BA) under the same condition. The mineralization current efficiency and the first-order kinetic constant for BA degradation at the TiO2-NTs/SnO2 electrode were 1 and 3.5 times greater than those observed for the SnO2 electrode.

Highly sensitive amperometric biosensors for phenols based on polyaniline-ionic liquid-carbon nanofiber composite

A novel polyaniline-ionic liquid-carbon nanofiber (PANI-IL-CNF) composite was greenly prepared by in situ one-step electropolymerization of aniline in the presence of IL and CNF for fabrication of amperometric biosensors. The scanning electron micrographs confirmed that the PANI uniformly grew along with the structure of CNF and the PANI-IL-CNF composite film showed a fibrillar morphology with the diameter of around 95 nm. A phenol biosensor was constructed by immobilizing tyrosinase on the surface of the composite modified glassy carbon electrode via the cross-linking step with glutaraldehyde. The biosensor exhibited a wide linear response to catechol ranging from 4.0 x 10(-10) to 2.1 x 10(-6)M with a high sensitivity of 296+/-4 AM(-1)cm(-2), a limit of detection down to 0.1 nM at the signal to noise ratio of 3 and applied potential of -0.05 V. According to the Arrhenius equation, the activation energy for enzymatic reaction was calculated to be 38.8 kJmol(-1) using catechol as the substrate. The apparent Michaelis-Menten constants of the enzyme electrode were estimated to be 1.44, 1.33, 1.16, 0.65 microM for catechol, p-cresol, phenol, m-cresol, respectively. The functionalization of CNF with PANI in IL provided good biocompatible platform for biosensing and biocatalysis.