Definitive evidence is presented for the favourable electrochemical properties of carbon nanotube modified electrodes arising from the ends of SWNTs due to oxygenated carbon species in general, and carboxylic acid moieties in particular, produced during acid purification.

Direct electron transfer between an electrode and the redox active centre of glucose oxidase, flavin adenine dinucleotide (FAD), is probed using carbon nanotube modified gold electrodes. Gold electrodes are first modified with a self-assembled monolayer of cysteamine and then shortened single walled carbon nanotubes (SWNT) are aligned normal to the electrode surface by self-assembly. The electrochemistry of these aligned nanotube electrode arrays is initially investigated using potassium ferricyanide which showed SWNT act as nanoelectrodes with the ends of the tubes more electrochemically active than the walls. Subsequently the nanotubes are plugged into the enzymes in one of two ways. In the first method, native glucose oxidase is covalently attached to the ends of the aligned tubes which allowed close approach to FAD and direct electron transfer to be observed with a rate constant of 0.3 s À1. In the second strategy, FAD was attached to the ends of the tubes and the enzyme reconstituted around the surface immobilized FAD. This latter approach allowed more efficient electron transfer to the FAD with a rate constant of 9 s À1.

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Micrometre-sized MgB2 crystals of varying quality, synthesized at low temperature and autogenous pressure, are compared using a combination of Raman and infra-red (IR) spectroscopy. These data, which include new peak positions in both spectroscopies for high quality MgB2, are interpreted using DFT calculations on phonon behaviour for symmetry-related structures. Raman and IR activity additional to that predicted by point group analyses of the P6/mmm symmetry are detected. These additional peaks, as well as the overall shapes of calculated phonon dispersion (PD) models are explained by assuming a double super-lattice, consistent with a lower symmetry structure for MgB2. A 2× super-lattice in the c-direction allows a simple correlation of the pair breaking energy and the superconducting gap by activation of corresponding acoustic frequencies. A consistent physical interpretation of these spectra is obtained when the position of a phonon anomaly defines a super-lattice modulation in the a-b plane.

The influence of the length of the carbon chain of a self-assembled monolayer (SAM) on gold electrodes on the electrochemical performance of carbon nanotube arrays attached to the SAM was explored. Four electrode constructs were assessed, all of which were modified with four different lengths (C2−C11) of amine-terminated alkanethiols. The four constructs were gold electrodes modified (1) with SAMs alone, (2) with carbon nanotubes randomly dispersed onto the SAM-modified electrodes by drop coating, (3) with vertically aligned carbon nanotubes formed by self-assembly onto the SAMs, and (4) with vertically aligned nanotubes with ferrocene attached to the nanotubes. By use of ruthenium hexaammine as a redox probe, the attachment of the carbon nanotubes to the SAM, either randomly dispersed or aligned, enabled electrochemistry to be observed at SAMs that were passivating prior to attachment of the nanotubes. The electrochemistry decayed exponentially with methylene chain length as expected but with a surprisingly low attenuation factor (β value) for the nanotube-modified surfaces. For randomly dispersed nanotubes, the β value was 0.27 per -CH2- (s = 0.04, n = 4), and for the vertically aligned nanotubes, 0.66 per -CH2- (s = 0.04, n = 4). A similar β value of 0.62 per -CH2- for vertically aligned nanotubes with ferrocene attached provided good evidence that the results with ruthenium hexaammine were due to tunneling through the SAM rather than electrochemistry proceeding via defects in the SAM or the nanotubes penetrating the SAM to the underlying electrode.

A novel gold coated femtosecond laser nanostructured sapphire surface - an "optical nose" - based on surface-enhanced Raman spectroscopy (SERS) for detecting vapours of explosive substances was investigated. Four different nitroaromatic vapours at room temperature were tested. Sensor responses were unambiguous and showed response in the range of 0.05-15 μM at 25 °C. The laser fabricated substrate nanostructures produced up to an eight-fold increase in Raman signal over that observed on the unstructured portions of the substrate. This work demonstrates a simple sensing system that is compatible with commercial manufacturing practices to detect taggants in explosives which can undertake as part of an integrated security or investigative mission.

A nanocrystalline TiO 2 (anatase) nanosheet exposing mainly the (001) crystal faces was tested as photoanode material in dye-sensitized solar cells. The nanosheets were prepared by hydrothermal growth in HF medium. Good-quality thin films were deposited on F-doped SnO 2 support from the TiO 2 suspension in ethanolic or aqueous media. The anatase (001) face adsorbs a smaller amount of the used dye sensitizer (C101) per unit area than the (101) face which was tested as a reference. The corresponding solar cell with sensitized (001)-nanosheet photoanode exhibits a larger open-circuit voltage than the reference cell with (101)-terminated anatase nanocrystals. The voltage enhancement is attributed to the negative shift of flatband potential for the (001) face. This conclusion rationalizes earlier works on similar systems, and it indicates that careful control of experimental conditions is needed to extract the effect of band energetic on the current/voltage characteristics of dye-sensitized solar cell.