Graphenes prepared by three different methods have been investigated as electrode materials in electrochemical supercapacitors. The samples prepared by exfoliation of graphitic oxide and by the transformation of nanodiamond exhibit high specific capacitance in aq. H 2 SO 4 , the value reaching up to 117 F/g. By using an ionic liquid, the operating voltage has been extended to 3⋅5 V (instead of 1 V in the case of aq. H 2 SO 4 ), the specific capacitance and energy density being 75 F/g and 31⋅9 Wh kg -1 respectively. This value of the energy density is one of the highest values reported to date. The performance characteristics of the graphenes which are directly related to the quality, in terms of the number of layers and the surface area, are superior to that of single-walled and multi-walled carbon nanotubes.

Graphene has been prepared by different methods: pyrolysis of camphor under reducing conditions (CG), exfoliation of graphitic oxide (EG), conversion of nanodiamond (DG) and arc evaporation of SiC (SG). The samples were examined by X-ray diffraction (XRD), transmission electron microscopy, atomic force microscopy, Raman spectroscopy and magnetic measurements. Raman spectroscopy shows EG and DG to exhibit smaller in-plane crystallite sizes, but in combination with XRD results EG comes out to be better. The CG, EG and DG samples prepared by us have BET surface areas of 46, 925 and 520 m 2 g À1 respectively and exhibit significant hydrogen uptake up to 3 wt%. EG also exhibits a high CO 2 uptake (34.7 wt%). Electrochemical redox properties of the graphene samples have been examined in addition to their use in electrochemical supercapacitors. Functionalization of EG and DG through amidation has been carried out with the purpose of solubilizing them in non-polar solvents. Water-soluble graphene has been produced by extensive acid treatment of EG or treatment with polyethylene glycol.

Nanopore sensors detect individual species passing through a nanoscale pore. This experimental paradigm suffers from long analysis times at low analyte concentration and non-specific signals in complex media. These limit effectiveness of nanopore sensors for quantitative analysis. Here, we address these challenges using antibody-modified magnetic nanoparticles ((anti-PSA)-MNPs) that diffuse at zero magnetic field to capture the analyte, prostate-specific antigen (PSA). The (anti-PSA)-MNPs are magnetically driven to block an array of nanopores rather than translocate through the nanopore. Specificity is obtained by modifying nanopores with anti-PSA antibodies such that PSA molecules captured by (anti-PSA)-MNPs form an immunosandwich in the nanopore. Reversing the magnetic field removes (anti-PSA)-MNPs that have not captured PSA, limiting non-specific effects. The combined features allow detecting PSA in whole blood with a 0.8 fM detection limit. Our ‘magnetic nanoparticle, nanopore blockade’ concept points towards a strategy to improving nanopore biosensors for quantitative analysis of various protein and nucleic acid species.

Synthesis forms a vital aspect of the science of nanomaterials. In this context, chemical methods have proved to be more effective and versatile than physical methods and have therefore, been employed widely to synthesize a variety of nanomaterials, including zero-dimensional nanocrystals, one-dimensional nanowires and nanotubes as well as two-dimensional nanofilms and nanowalls. Chemical synthesis of inorganic nanomaterials has been pursued vigorously in the last few years and in this article we provide a perspective on the present status of the subject. The article includes a discussion of nanocrystals and nanowires of metals, oxides, chalcogenides and pnictides. In addition, inorganic nanotubes and nanowalls have been reviewed. Some aspects of core-shell particles, oriented attachment and the use of liquid-liquid interfaces are also presented.

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Carbon nanotubes (CNTs) and inorganic nanowires constitute two important classes of one-dimensional materials. [1][2][3][4][5] Several studies on the synthesis, characterization, and manipulation of these materials have been reported.[6] Thus, several workers have prepared composites of these materials and studied their properties. [1,4,7,8] CNTs have been employed as templates for the preparation of nanotubes and nanowires of inorganic materials, especially of metal oxides. [4,[9][10][11][12][13][14][15][16] For this purpose, the CNTs were covered with an oxide precursor or a gel and the nanotubes burnt off in air. [9][10][11][12][13] Han and Zettl [14] coated single-walled carbon nanotubes using a simple solution-based chemical route. While Fu et al. [15] used a high-pressure method to coat the nanotubes with layers of rare-earth oxides. Ruthenium oxide nanotubes have been obtained by Min et al. [16] by the oxidation of Ru-coated carbon nanotubes prepared by atomic layer deposition. It was our view that it would be of considerable importance if we were able to prepare composite structures of CNTs and inorganic nanowires, wherein a layer of a ceramic oxide is chemically bonded to the surface of the nanostructures. Knowing that Si-O or metal-oxygen bonds can be formed with substrates by the reaction of an appropriate chloro compound with the hydroxyl groups present on the substrate, we have explored whether ceramic oxide-coated structures can be obtained by the reaction of reactive metal chlorides with acid-treated CNTs and metal oxide nanowires. This seemed entirely feasible since the CNTs on acid treatment become functionalized with surface hydroxyl and carboxyl groups, and the metal oxide nanowires would necessarily possess hydroxyl groups on the surface. [1,2,6] The surface functional groups have been made use of for the solubilization of CNTs and other purposes. [1,6] On reaction with the vapor of a metal halide such as TiCl 4 , the surface hydroxyl groups on the nanostructures can form metal-oxygen bonds by eliminating HCl leaving extra metal-chlorine bonds. The metal-chlorine bonds can be hydrolyzed by treatment with water and the hydroxide layer again reacted with the metal chloride. On repeating the process several times followed by calcination, one should be able to obtain a CNT or a metal oxide nanowire with a chemically bonded ceramic coating of the desired thickness. We illustrate the process schematically in Scheme 1.In Figure 1a, we show a typical transmission electron microscopy (TEM) image of TiO 2 -coated multiwalled carbon nanotubes (MWNTs) obtained after ten cycles at 80°C (see Experimental for details). The color of the MWNTs changed from black to gray after the reaction. The energy-dispersive X-ray (EDX) spectrum in Figure 2a shows the presence of Ti and Cl after the reaction, the latter arising from the incomplete hydrolysis of TiCl 4 . On calcination, at 350°C for 12 h, the chlorine is eliminated as revealed by the EDX spectrum in Figure 2b. TEM images of the calcined product are shown in ...

This paper reports the manipulation of surface plasmon polaritons (SPPs) in a liquid plasmonic metal by changing its physical phase. Dynamic properties were controlled by solid-to-liquid phase transitions in 1D Ga gratings that were fabricated using a simple molding process. Solid and liquid phases were found to exhibit different plasmonic properties, where light coupled to SPPs more efficiently in the liquid phase. We exploited the supercooling characteristics of Ga to access plasmonic properties associated with the liquid phase over a wider temperature range (up to 30 °C below the melting point of bulk Ga). Ab initio density functional theory-molecular dynamic calculations showed that the broadening of the solid-state electronic band structure was responsible for the superior plasmonic properties of the liquid metal.

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