The sluggish reaction kinetics of the oxygen reduction reaction (ORR) has been the limiting factor for fuel energy utilization, hence it is desirable to develop high-performance electrocatalysts for a 4-electron pathway ORR. A constant low-current (50 μA) electrodeposition technique is used to realize the formation of a uniform Co O film on well-aligned electrospun carbon nanofibers (ECNFs) with a time-dependent growth mechanism. This material also exhibits a new finding of mT magnetic field-induced enhancement of the electron exchange number of the ORR at a glassy carbon electrode modified with the Co O /ECNFs catalyst. The magnetic susceptibility of the unpaired electrons in Co O improves the kinetics and efficiency of electron transfer reactions in the ORR, which shows a 3.92-electron pathway in the presence of a 1.32 mT magnetic field. This research presents a potential revolution of traditional electrocatalysis by simply applying an external magnetic field on metal oxides as a replacement for noble metals to reduce the risk of fuel-cell degradation and maximize the energy output.

Carbon nanodots (CNDs) have attracted great attention due to their superior solubility, biocompatibility, tunable photoluminescence, and opto-electronic properties. This work describes a new fluorescence-based spectroelectrochemistry approach to simultaneously study the photoluminescence and wavelength dependent photocurrent of microwave synthesized CNDs. The fluorescence of CNDs has a selective quench upon a reversible redox couple, ferricyanide/ferrocyanide,− reaction during the cyclic voltammetry. The CNDs modified gold slide electrode demonstrates wavelength dependent photocurrent generation during the fluorescence-electrochemical study, suggesting potential application in photoelectronics. UV-Vis absorption and electrochemistry are used to quantify the energy gap of the CNDs, and then to calibrate a Hückel model for the CNDs electronic energy levels. The Hückel (or tight binding) model treatment of an individual CND as a molecule combines the conjugated π states (C=C) with the functional groups (C=O, C-O, and COOH) associated with the surface electronic states. This experimental and theoretical investigation of the CNDs provides a new perspective on the optoelectronic properties of CNDs and should aid in their development for practical use in biomedicine, chemical sensing, and photoelectric devices.

Carbon nanodots (CNDs) have shown potential for antioxidative activity at the cellular level.Here we applied a facile hydrothermal method to prepare fluorescent nitrogen and sulfur (N,S-) codoped CNDs using α-lipoic acid, citric acid, and urea as precursor molecules. This work describes a comprehensive study for exploring their antioxidation activity using UV-vis absorption and electrochemistry measurements of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH • ), as well as a lucigenin chemiluminescence (lucigenin-CL) assay. The lucigenin-CL assay detects superoxide anion radicals, i.e., reactive oxygen species (ROS) produced through the xanthine/xanthine oxidase (XO) reaction. The electrochemically derived relationship between the unreacted nitrogen-centered DPPH • and CND concentrations agrees with that obtained from UV-vis measurements. A reaction pathway for the ROS antioxidative reaction of N,S-codoped CNDs is proposed. These findings should aid in the development of N,S-codoped CNDs for practical use in biomedical applications.