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 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.

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•.

Carbon nanodots (CNDs), reported as polyatomic carbon domains surrounded by amorphous carbon frames, have drawn extensive attention due to their easy-to-synthesis, outstanding electronic properties, and superior biocompatibility. However, substantial assessments regarding their biological performance are still needed, considering the complex nature of this type of relatively new nanoparticles. In this report, CNDs derived from urea and citric acid (U-CNDs) are investigated in the treatment of two cell lines, EA.hy926 and A549 cells, to examine the biocompatibility, cellular uptake, and antioxidation effect. The intracellular uptake study suggests an energy-dependent transport process into the cells mainly involving macropinocytosis and lipid raft-mediated endocytosis pathways. Moreover, the U-CNDs mostly target the mitochondria and present strong antioxidative effects by scavenging reactive oxygen species (ROS) in cells. Overall the findings in this report manifest that the U-CNDs could serve as a bioimaging reagent and antioxidant causing little deleteriousness in the respects of viability, plasma membrane integrity, and mitochondrial activity in both cell lines, and demonstrate some efficacy for inhibiting the metabolic activities of A549 cancer cells at higher concentration.

Despite the potential health benefits of curcumin, such as antioxidant, anticancer, anti-inflammatory, and antimicrobial properties, its usage is limited by poor bioavailability and low aqueous solubility. Nano-formulations of curcumin have gained a lot of attention due to their increased bioavailability, solubility, circulation times, targeted specificity, decreased biodegradation, better stability, and improved cellular uptake. The current study aimed to enhance the bioavailability of curcumin using carbon nanodots (CNDs) as loading vehicles to deliver curcumin due to their excellent biocompatibility, aqueous solubility, and photoluminescence properties. Two types of CNDs (E-CNDs and U-CNDs) were used for curcumin loading and characterized for particle size, morphology, loading capability (measured as adsorption efficiency and loading capacity), stability, photoluminescence properties, in vitro drug release studies, cellular uptake, and anticancer activity. The prepared curcumin-loading CNDs (Curc-CNDs) displayed sizes around or below 10 nm with good stability. The Curc-E-CNDs demonstrated a curcumin adsorption efficiency of 91% in solution, while the Curc-U-CNDs have an adsorption efficiency of 82%. Both have a loading capacity of 3.4–3.8% with respect to the weight of the CNDs. Curcumin release followed a controlled sustained pattern that a total of 60% and 74% of curcumin was released at 72 h from Curc-E-CNDs and Curc-U-CNDs, respectively, in pH 5 buffer, and almost 90% was released in culture media within 96 h. Both of the Curc-CNDs were uptaken by cells and exhibited prominent cytotoxicity toward cancer cells. The results clearly depict the role of CNDs as efficient carriers for curcumin delivery with prolonged release and enhanced bioavailability, thereby improving the overall antitumor activity.