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Hybrid materials of vanadium nitride and porous carbon nanoparticles (VN/PCNPs) were fabricated by a facile pyrolysis process of vanadium pentoxide (V2O5) xerogel and melamine at relatively low temperature of 800 °C for supercapacitor application. The effects of the feed ratio of V2O5 to melamine (r), and nitrogen flow rate on the microstructure and electrochemical performance were also investigated. It was found that the size of the as-synthesized nanoparticles is about 20 nm. Both r value and N2 flow rate have enormous impacts on morphology and microstructure of the nanoparticle, which correspondingly determined the electrochemical performance of the material. The VN/C hybrid nanoparticles exhibited high capacitive properties, and a maximum specific capacitance of 255.0 F g−1 was achieved at a current density of 1.0 A g−1 in 2 M KOH aqueous electrolyte and the potential range from 0 to −1.15 V. In addition, symmetrical supercapacitor fabricated with the as-synthesized VN/PCNPs presents a high specific capacitance of 43.5 F g−1 at 0.5 A g−1 based on the entire cell, and an energy density of 8.0 Wh kg−1 when the power density was 575 W kg−1. Even when the power density increased to 2831.5 W kg−1, the energy density still remained 6.1 Wh kg−1.Graphical Abstract Electronic supplementary materialThe online version of this article (doi:10.1007/s40820-016-0105-5) contains supplementary material, which is available to authorized users.

Transition-metal nitrides exhibit wide potential windows and good electrochemical performance, but usually experience imbalanced practical applications in the energy storage field due to aggregation, poor circulation stability, and complicated syntheses. In this study, a novel and simple multi-phase polymeric strategy was developed to fabricate hybrid vanadium nitride/carbon (VN/C) membranes for supercapacitor negative electrodes, in which VN nanoparticles were uniformly distributed in the hierarchical porous carbon 3D networks. The supercapacitor negative electrode based on VN/C membranes exhibited a high specific capacitance of 392.0 F g−1 at 0.5 A g−1 and an excellent rate capability with capacitance retention of 50.5% at 30 A g−1. For the asymmetric device fabricated using Ni(OH)2//VN/C membranes, a high energy density of 43.0 Wh kg−1 at a power density of 800 W kg−1 was observed. Moreover, the device also showed good cycling stability of 82.9% at a current density of 1.0 A g−1 after 8000 cycles. This work may throw a light on simply the fabrication of other high-performance transition-metal nitride-based supercapacitor or other energy storage devices.Electronic supplementary materialThe online version of this article (10.1007/s40820-018-0217-1) contains supplementary material, which is available to authorized users.

Until now, despite the great success acquired in scientific research and commercial applications, magnetic beads (MBs) have been used for nothing more than a carrier in most cases in bioassays. In this work, highly chemiluminescent magnetic beads containing N-(4-aminobutyl)-N-ethyl isoluminol (ABEI) and Co (Co/ABEI/MBs) were first synthesized via a facile strategy. ABEI and Co were grafted onto the surface of carboxylated MBs by virtue of a carboxyl group and electrostatic interaction. The as-prepared Co/ABEI/MBs exhibited good paramagnetic properties, satisfactory stability, and intense chemiluminescence (CL) emission when reacted with HO, which was more than 150 times that of ABEI functionalized MBs. Furthermore, it was found that 2,4,6-trinitrotoluene (TNT) aptamer could attach to the surface of Co/ABEI/MBs via electrostatic interaction and coordination interaction between TNT aptamer and Co, leading to a decrease in CL intensity due to the catalytic site Co being blocked by the aptamer. In the presence of TNT, TNT would bind strongly with TNT aptamer and detach from the surface of Co/ABEI/MBs, resulting in partial restoration of the CL signal. Accordingly, label-free aptasensor was developed for the determination of TNT in the range of 0.05-25 ng/mL with a detection limit of 17 pg/mL. This work demonstrates that Co/ABEI/MBs are easily connected with recognition biomolecules, which are not only magnetic carriers but also direct sensing interfaces with excellent CL activity. It provides a novel CL interface with a magnetic property which easily separates analytes from the sample matrix to construct label-free bioassays.