The new materials processing beamline at the SRS Daresbury, MPW6.2

A new beamline (MPW6.2) has been designed and built for the study of materials during processing where three synchrotron techniques, SAXS, WAXS and XAS, are available simultaneously. It has been demonstrated that Rietveld refinable data can be collected from silicon SRM 640b over a 60 degrees range in a time scale of 1 s. The data have been refined to a chi(2) of 2.4, the peaks fitting best to a Pearson VII function or with fundamental parameters. The peak halfwidths have been found to be approximately constant at 0.06 degrees over a 120 degrees angular range indicating that the instrumental resolution function has matched its design specification. A quantitative comparison of data sets collected on the same isotactic polypropylene system on MPW6.2 and DUBBLE at the ESRF shows a 17% improvement in angular resolution and a 1.8 improvement in peak-to-background ratio with the RAPID2 system; the ESRF data vary more smoothly across detector channels. The time-dependent wide-angle XRD was tested by comparing a hydration reaction of gypsum-bassanite-anhydrite with energy-dispersive data collected on the same system on the same time scale. Three sample data sets from the reaction were selected for analysis and gave an average chi(2) of 3.8. The Rietveld-refined lattice parameters are a good match with published values and the corresponding errors show a mean value of 3.3 x 10(-4). The data have also been analysed by the Pawley decomposition phase-modelling technique demonstrating the ability of the station to quickly and accurately identify new phases. The combined SAXS/WAXS capability of the station was tested with the crystallization and spinodal decomposition of a very dilute polymer system. Our measurements show that the crystallization of a high-density co-polymer (E76B38) as low as 0.5% by weight can be observed in solution in hexane. The WAXS and SAXS data sets were collected on the same time scale. The SAXS detector was calibrated using a collagen sample that gave 30 orders of diffraction in 1 s of data collection. The combined XRD and XAS measurement capability of the station was tested by observing the collapse and re-crystallization of zinc-exchanged zeolite A (zeolite Zn/Na-A). Previous studies of this material on station 9.3 at the SRS were compared with those from the new station. A time improvement of 38 was observed with better quality counting statistics. The improved angular resolution from the WAXS detector enabled new peaks to be identified.

Chemical force microscopy with active enzymes

The adhesion forces have been measured between an atomic force microscope tip derivatized with an active enzyme, shikimate kinase, and an ATP mimic immobilized on a gold surface. Experiments with competitive binding of other ligands in solution show that the observed adhesion forces arise predominantly from specific interactions between the immobilized enzyme and surface-bound adenine derivative. These experiments represent a step in the development of a screening methodology based upon chemical force microscopy.

Coated silica tips for use in high-pressure, high-temperature, scanning tunneling microscopy

A novel application of coated silica tips for use in high-pressure, high-temperature, scanning tunneling microscopy is introduced. Thermal drift is reduced in the Z-direction due to the low thermal expansion of silica. Virtually, any conducting material that can be evaporated or sputtered can be used as a tip material. Experimental results are shown for tips sputter coated with platinum, along with images obtained.

Hybrid scanning ion conductance and scanning near-field optical microscopy for the study of living cells

We have developed a hybrid scanning ion conductance and scanning near-field optical microscope for the study of living cells. The technique allows quantitative, high-resolution characterization of the cell surface and the simultaneous recording of topographic and optical images. A particular feature of the method is a reliable mechanism to control the distance between the probe and the sample in physiological buffer. We demonstrate this new method by recording near-field images of living cells (cardiac myocytes).

Optical chemical imaging of tobacco mosaic virus in solution at 60-nm resolution

Scanning near-field optical microscopy can provide images with a resolution less than the wavelength of light, and therefore ought in principle to be of great value in studies of biological structures. In this work we show how for the first time images have been obtained of tobacco mosaic virus particles at 60-nm resolution, combined with chemical imaging using monoclonal antibodies under in vitro conditions.

Neutron inelastic scattering spectra of methane on graphite at the commensurate–incommensurate phase transition

Neutron scattering spectra associated with rotational tunnelling and low frequency vibrations of CH4 adsorbed on graphite at 4 K and coverages from 0.2 to 1.5 monolayers are reported. Particular consideration is given to the changes which occur across the commensurate–incommensurate phase transition. It is shown that the incommensurate phase has a domain wall structure and is not a floating phase as had previously been proposed from theory.