Electrochemical and Structural Modifications of Humic Acids in Aerobically and Anaerobically Incubated Peat

Exposure to oxygen and aerobic biological activity during drought periods alters the availability of terminal electron acceptors (TEA) in the peat catotelm layer. We investigated the changes in the electrochemical and chemical characteristics of humic acids (HA) induced by subjecting air-dried sphagnum peat to biological oxidation or reduction during a 90-day incubation experiment. Structural modifications of HAs from anaerobically (HAred) and aerobically (HAox) incubated peat were investigated by ATR-FTIR, UV–vis, and EEM fluorescence spectroscopy. Number and strength of acid groups were characterized by titration, while changes in redox properties were characterized by cyclic voltammetry and quantified by coulometry with mediated electrochemical oxidation (MEO). Exposure to oxygen had small effects, but compared to anaerobic incubation, decreased by 20% the capacity of HA to reduce the radical ion of 2,2′-Azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS●−), passing from 2.77 ± 0.13 mmole- gHA−1 in HAred to 2.21 ± 0.10 mmole- gHA−1 in HAox. Pseudo-first-order electron transfer kinetic constants were 13.3 ± 1.2 s−1 for HAox and 16.7 ± 1.4 s−1 for HAred. Alterations in the hydrological status of the catotelm have minor effects on the actual in situ availability of organic TEA, but if coupled to intensified biological activity they may result in significant variations of greenhouse gases emissions.

In Situ Spectroelectrochemical Investigation of Perovskite Quantum Dots for Tracking Their Transformation

All-inorganic lead-halide perovskite quantum dots (PQDs) (CsPbX3, where X is Cl, Br, or I) have been used successfully in optoelectronic applications, such as solar cells, light-emitting diodes, photocatalysts, and lasers. These PQDs work under electrochemical bias and/or illumination with charge separation/collection by interacting with the charge-transport medium. In this study, we discuss the spectroelectrochemical characteristics of PQDs to understand the oxidation and reduction processes that occur during photoinduced charge transport or charge injection under electrochemical conditions. We also found that the PQDs underwent irreversible transformation to the precursor state of plumbate complexes under electrochemical conditions. Furthermore, in situ spectroelectrochemical analysis demonstrated that hole-mediated electrochemical oxidation of PQDs resulted in their irreversible transformation. Finally, the results presented herein contribute to our understanding of the charge-transfer-mediated process in PQDs and enhance their application potential in optoelectronic devices.

Degradation of Nonylphenol Ethoxylate-10 (NPE-10) by Mediated Electrochemical Oxidation (MEO) Technology

Nonylphenol ethoxylate (NPE-10) is a non-ionic surfactant that is synthesized from alkylphenol ethoxylate. The accumulation of NPE-10 in wastewater will endanger the ecosystem as well as the human being. Nowadays, NPE-10 can be degraded indirectly by using an electrochemical treatment by the advancement of technology. Thus, this study is aimed to evaluate the electro-degradation potential of NPE-10 by MEO using Ce(IV) ionic mediator. In addition, the influence of Ag(I) ionic catalyst in the performance of MEO for the degradation of NPE-10 was also observed. The potency of MEO technology in the NPE-10 degradation was evaluated by voltammetry technique and confirmed by titrimetry and LC-MS analysis. The results showed that in the absence of Ag(I) ionic catalyst, the degradation of NPE-10 by MEO was 85.93%. Furthermore, when the Ag(I) ionic catalyst was applied, the performance of MEO in degradation of NPE-10 was improved to 95.12%. The back titration using Ba(OH)2 confirmed the formation of CO2 by 46.79%, whereas the redox titration shows the total of degradation organic compounds by 42.50%. It was emphasized by the formation of two new peaks in the LC-MS chromatogram. In summary, our results confirmed the potential of MEO technology for the NPE-10 degradation.

Diethyl Phosphite Promoted Electrochemical Oxidation of Tetrahydroisoquinolines to 3,4-Dihydroisoquinolin-1(2H)-ones

A diethyl phosphite mediated electrochemical oxidation strategy for the synthesis of 3,4-dihydroisoquinolin-1(2H)-ones from tetrahydroisoquinolines under mild conditions has been developed. This protocol provides an environmentally friendly and simple way for the construction of C=O bonds in an undivided cell unit.