The self-limiting reaction of aqueous permanganate with carbon nanofoams produces conformal, nanoscopic deposits of birnessite ribbons and amorphous MnO2 throughout the ultraporous carbon structure. The MnO2 coating contributes additional capacitance to the carbon nanofoam while maintaining the favorable high-rate electrochemical performance inherent to the ultraporous carbon structure of the nanofoam. Such a three-dimensional design exploits the benefits of a nanoscopic MnO2-carbon interface to produce an exceptionally high area-normalized capacitance (1.5 F cm-2), as well as high volumetric capacitance (90 F cm-3).

This paper describes the preparation of air and moisture stable octanol derivatized crystalline silicon nanoparticles by room temperature sodium naphthalenide reduction of silicon halides.

Alkyl-capped and alkyl/alkoxy-capped silicon nanocrystals have been prepared by the oxidation of magnesium silicide with bromine. High-resolution transmission electron microscopy confirmed the crystalline nature of the nanoparticles and provided an average diameter of 4.5 (2.0) nm for the alkyl-capped and for the alkyl/alkoxy-capped nanoparticles. Energy-dispersive X-ray spectroscopy showed that the nanoparticles are composed of silicon, with no evidence of unreacted bromine. FTIR spectra were consistent with alkyl-and alkyl/ alkoxy-capped surfaces. Fluorescence spectroscopy indicated strong ultraviolet-blue photoluminescence, which was attributed to both quantum confinement and surface termination. These nanoparticles displayed long-term stability and no degradation of the photoluminescence was observed for a period of 1 year.

We describe a simple self-limiting electroless deposition process whereby conformal, nanoscale iron oxide (FeO(x)) coatings are generated at the interior and exterior surfaces of macroscopically thick ( approximately 90 microm) carbon nanofoam paper substrates via redox reaction with aqueous K(2)FeO(4). The resulting FeO(x)-carbon nanofoams are characterized as device-ready electrode structures for aqueous electrochemical capacitors and they demonstrate a 3-to-7 fold increase in charge-storage capacity relative to the native carbon nanofoam when cycled in a mild aqueous electrolyte (2.5 M Li(2)SO(4)), yielding mass-, volume-, and footprint-normalized capacitances of 84 F g(-1), 121 F cm(-3), and 0.85 F cm(-2), respectively, even at modest FeO(x) loadings (27 wt %). The additional charge-storage capacity arises from faradaic pseudocapacitance of the FeO(x) coating, delivering specific capacitance >300 F g(-1) normalized to the content of FeO(x) as FeOOH, as verified by electrochemical measurements and in situ X-ray absorption spectroscopy. The additional capacitance is electrochemically addressable within tens of seconds, a time scale of relevance for high-rate electrochemical charge storage. We also demonstrate that the addition of borate to buffer the Li(2)SO(4) electrolyte effectively suppresses the electrochemical dissolution of the FeO(x) coating, resulting in <20% capacitance fade over 1000 consecutive cycles.

We report the room temperature solution synthesis of alkyl protected silicon nanocrystals. The nanocrystals are of unusually uniform tetrahedral morphology and of a limited size distribution. The nanocrystals were characterized by transmission and scanning electron microscopy as well as atomic force microscopy.