Electrochemical behaviour of benzylamine, 2-phenylethylamine and 4-hydroxyphenylethylamine at gold. A comparative study

Efficient photocatalytic hydrogen peroxide generation coupled with selective benzylamine oxidation over defective ZrS3 nanobelts

Photocatalytic hydrogen peroxide (H₂O₂) generation represents a promising approach for artificial photosynthesis. However, the sluggish half-reaction of water oxidation significantly limits the efficiency of H₂O₂ generation. Here, a benzylamine oxidation with more favorable thermodynamics is employed as the half-reaction to couple with H₂O₂ generation in water by using defective zirconium trisulfide (ZrS₃) nanobelts as a photocatalyst. The ZrS₃ nanobelts with disulfide (S₂^2-) and sulfide anion (S^2-) vacancies exhibit an excellent photocatalytic performance for H₂O₂ generation and simultaneous oxidation of benzylamine to benzonitrile with a high selectivity of >99%. More importantly, the S₂^2- and S^2- vacancies can be separately introduced into ZrS₃ nanobelts in a controlled manner. The S₂^2- vacancies are further revealed to facilitate the separation of photogenerated charge carriers. The S^2- vacancies can significantly improve the electron conduction, hole extraction, and kinetics of benzylamine oxidation. As a result, the use of defective ZrS₃ nanobelts yields a high production rate of 78.1 ± 1.5 and 32.0 ± 1.2 μmol h^-1 for H₂O₂ and benzonitrile, respectively, under a simulated sunlight irradiation.

An Easily Fabricated Electrochemical Sensor Based on a Graphene-Modified Glassy Carbon Electrode for Determination of Octopamine and Tyramine

A simple electrochemical sensor has been developed for highly sensitive detection of octopamine and tyramine by electrodepositing reduced graphene oxide (ERGO) nanosheets onto the surface of a glassy carbon electrode (GCE). The electrocatalytic oxidation of octopamine and tyramine is individually investigated at the surface of the ERGO modified glassy carbon electrode (ERGO/GCE) by using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Several essential factors including the deposition cycle of reduced graphene oxide nanosheets and the pH of the running buffer were investigated in order to determine the optimum conditions. Furthermore, the sensor was applied to the quantification of octopamine and tyramine by DPV in the concentration ranges from 0.5 to 40 μM and 0.1 to 25 μM, respectively. In addition, the limits of detection of octopamine and tyramine were calculated to be 0.1 μM and 0.03 μM (S/N = 3), respectively. The sensor showed good reproducibility, selectivity and stability. Finally, the sensor successfully detected octopamine and tyramine in commercially available beer with satisfactory recovery ranges which were 98.5%–104.7% and 102.2%–103.1%, respectively. These results indicate the ERGO/GCE based sensor is suitable for the detection of octopamine and tyramine.

Room temperature aerobic oxidation of amines by a nanocrystalline ruthenium oxide pyrochlore nafion composite catalyst

The aerobic oxidation of primary amines to their respective nitriles has been carried out at room temperature using a highly reusable nanocrystalline ruthenium oxide pyrochlore Nafion composite catalyst (see figure).

Fast-scan cyclic voltammetry for the detection of tyramine and octopamine

Tyramine and octopamine are biogenic amine neurotransmitters in invertebrates that have functions analogous to those of the adrenergic system in vertebrates. Trace amounts of these neurotransmitters have also been identified in mammals. The purpose of this study was to develop an electrochemical method using fast-scan cyclic voltammetry at carbon-fiber microelectrodes to detect fast changes in tyramine and octopamine. Because tyramine is known to polymerize and passivate electrode surfaces, waveform parameters were optimized to prevent passivation. No fouling was observed for octopamine when the electrode was scanned from 0.1 to 1.3 V and back at 600 V/s, while a small decrease of less than 10% of the signal was seen for 15 repeated exposures to tyramine. The technique has limits of detection of 18 nM for tyramine and 30 nM for octopamine, much lower than expected levels in insects and lower than basal levels in some brain regions of mammals. Current was linear with concentration up to 5 microM. This voltammetry technique should be useful for measuring tyramine and octopamine changes in insects, such as the fruit fly, Drosophila melanogaster.