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Through a simple method, a new kind of Mn 3 O 4 nanoparticles (Mn 3 O 4 NPs) decorated nitrogen-doped graphene (N-GR) was synthesized firstly, and then a Mn 3 O 4 NPs/N-GR modified carbon paste electrode (CPE) was fabricated. Several techniques, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemistry, were performed to characterize Mn 3 O 4 NPs/N-GR. A large amount of N on the graphene surface (about 9.86% of atomic ratio) was detected by XPS. Mn 3 O 4 nanoparticles (50–80 nm) homogeneously coated on N-GR. Mn 3 O 4 NPs/N-GR/CPE was used for sensitive non-enzymatic glucose sensing, which exhibited the response current of glucose ca. 10-fold higher than that of pure CPE. Under the optimum determination conditions, Mn 3 O 4 NPs/N-GR/CPE provided glucose with a broader detection range of 2.5–529.5 μM with a low detection limit (1.0 μM, S/N = 3). This novel method was successfully used to determine glucose in human urine sample. [ABSTRACT FROM AUTHOR]

Nitrogen-enriched porous carbon nanofibers were successfully prepared by using water-soluble phenolic resin/polyvinyl alcohol blend solution as precursor via electrospinning followed by carbonization and NH 3 treatments. The NH 3 treatment time has a significant effect on the pore structure, thermal stability as well as the surface chemistry. The as-prepared carbon materials were studied as freestanding electrodes for supercapacitor without the addition of binders and conductive additives in 6 M KOH solution. The sample treated with NH 3 for 3 h exhibits a high specific surface area (763 m 2 g −1 ), rich surface functionalities (5.26 at.% nitrogen and 4.37 at.% oxygen), optimized pore structure, good thermal stability and electrical conductivity. It shows the maximum specific capacitance of up to 251.2 F g −1 at 0.1 A g −1 , about 25% higher than that of the sample treated with argon. Furthermore, the specific capacitance remains 193 F g −1 at 20 A g −1 with high rate capability of 77%, as well as excellent cycle stability (99% capacity retention after 2000 cycles). The outstanding performance of nitrogen-doped porous carbon nanofibers could be attributed to the synergistic effect of the proper pore size distribution, high effective surface area and certain amount of nitrogen- and oxygen-containing functional groups, resulting in both electrochemical double layer and faradaic capacitance contributions. [ABSTRACT FROM AUTHOR]

Herein, a facile hydrothermal treatment of lime juice to prepare biocompatible nitrogen-doped carbon quantum dots (N-CQDs) in the presence of ammonium bicarbonate as a nitrogen source has been presented. The resulting N-CQDs exhibited excitation and pH independent emission behavior; with the quantum yield (QY) up to 40%, which was several times greater than the corresponding value for CQDs with no added nitrogen source. The N-CQDs were applied as a fluorescent probe for the sensitive and selective detection of Hg 2 + ions with a detection limit of 14 nM. Moreover, the cellular uptake and cytotoxicity of N-CQDs at different concentration ranges from 0.0 to 0.8 mg/ml were investigated by using PC12 cells as a model system. Response surface methodology was used for optimization and systematic investigation of the main variables that influence the QY, including reaction time, reaction temperature, and ammonium bicarbonate weight. [ABSTRACT FROM AUTHOR]

In this paper, we report a template-free method to fabricate hollow nitrogen-doped carbon (HNC) by pyrolysis of hollow polyaniline microspheres, which were synthesized by suspension polymerization method. The entire synthesis is simple, environmentally benign, and economic. The oxygen reduction reaction (ORR) activity of the as-prepared HNC catalyst is close to that of the commercial Pt/C catalyst in alkaline media with four electron pathway. Moreover, the HNC shows much better fuel crossover resistance and long-term durability than the commercial Pt/C in alkaline medium. All these features make HNC a potentially promising and suitable substitute for the expensive noble metal catalysts in the next generation alkaline fuel cells. [ABSTRACT FROM AUTHOR]