This work reports on a finding of mT magnetic field induced energy storage enhancement of MnO 2 -based supercapacitance electrodes (magneto-supercapacitor).Electrodes with MnO 2 electrochemically deposited at electrospun carbon nanofibers (ECNFs) film are studied by cyclic voltammetry (CV), galvanostatic charge/discharge, electrochemical impedance spectroscopy (EIS), and life cycle stability tests in the presence/absence of milli-Tesla (mT) magnetic fields derived by Helmholtz coils. In the presence of 1.34 mT, MnO 2 /ECNFs shows a magneto-enhanced capacitance of 141.7 F g -1 vs. 119.2 F g -1 (~19% increase) with absence of magnetic field at the voltage sweeping rates of 5 mV s -1 . The mechanism of the magneto-supercapacitance is discussed and found that the magnetic susceptibility of the MnO 2 significantly improves the electron transfer reaction of pseudoreaction of Mn(IV)/Mn(III) at the electrode, along with the magnetic field induced impedance effect, which may greatly enhance the interface charge density, facilitate electrolyte transportation, and improve the efficiency of cation intercalation/de-intercalation of the pseudocapacitor under mT-magnetic field exposure, resulting in enhancement of energy storage capacitance and longer charge/discharge time of the MnO 2 /ECNFs electrode without sacrificing its life cycle stability.

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 good antioxidant capabilities by scavenging oxidant free radicals such as diphenyl-1-picrylhydrazyl radical (DPPH•) and reactive oxygen species. While some studies suggest that the antioxidation activities associate to the proton donor role of surface active groups like carboxyl groups (–COOH), it is unclear how exactly the extent of oxidant scavenging potential and its related mechanisms are influenced by functional groups on CNDs’ surfaces. In this work, carboxyl and the amino functional groups on CNDs’ surfaces are modified to investigate the individual influence of intermolecular interactions with DPPH• free radical by UV-Vis spectroscopy and electrochemistry. The results suggest that both the carboxyl and the amino groups contribute to the antioxidation activity of CNDs through either a direct or indirect hydrogen atom transfer reaction with DPPH•.