Biomedical subjects
Publications and source records attributed to D J Schiffrin.
Fullerene-Pt nanoparticle assemblies were prepared by attachment and immobilisation of different Pt nanoparticles on a gold electrode using molecular layers of C60 as a linker system. These assemblies were active for the methanol oxidation following treatment with CO.
It is demonstrated that scanning electrochemical microscopy can be used to investigate the kinetics of electron transfer reactions catalysed by metal nanoparticles supported on an insulating substrate.
So-called bottom-up fabrication methods aim to assemble and integrate molecular components exhibiting specific functions into electronic devices that are orders of magnitude smaller than can be fabricated by lithographic techniques. Fundamental to the success of the bottom-up approach is the ability to control electron transport across molecular components. Organic molecules containing redox centres-chemical species whose oxidation number, and hence electronic structure, can be changed reversibly-support resonant tunnelling and display promising functional behaviour when sandwiched as molecular layers between electrical contacts, but their integration into more complex assemblies remains challenging. For this reason, functionalized metal nanoparticles have attracted much interest: they exhibit single-electron characteristics (such as quantized capacitance charging) and can be organized through simple self-assembly methods into well ordered structures, with the nanoparticles at controlled locations. Here we report scanning tunnelling microscopy measurements showing that organic molecules containing redox centres can be used to attach metal nanoparticles to electrode surfaces and so control the electron transport between them. Our system consists of gold nanoclusters a few nanometres across and functionalized with polymethylene chains that carry a central, reversibly reducible bipyridinium moiety. We expect that the ability to electronically contact metal nanoparticles via redox-active molecules, and to alter profoundly their tunnelling properties by charge injection into these molecules, can form the basis for a range of nanoscale electronic switches.
The electrochemistry of ubiquinone-10, UQ, incorporated over a phospholipid layer adsorbed on a mercury drop electrode has been investigated over a wide pH range. It is shown that the position of the quinone headgroup in relation to the lipid determines the reversibility of the redox chemistry. For pH <7, the reaction follows a disproportionation route involving the ubiquione radical. There is evidence for the presence of a parallel reaction sequence. The bifurcation point appears to occur for the UQ molecule, which disproportionates after protonation and reduction, in parallel with direct electron transfer to yield the UQ--radical anion. The incorporation of UQ in a lipid monolayer makes its reduction very irreversible for pH > 7.
Ellipsometric measurements were used to monitor the formation of a bacterial cell film on polarized metal surfaces (Al-brass and Ti). Under cathodic polarization bacterial attachment was measured from changes in the ellipsometric angles. These were fitted to an effective medium model for a nonabsorbing bacterial film with an effective refractive index (nf) of 1.38 and a thickness (df) of 160 +/- 10 nm. From the optical measurements a surface coverage of 17% was estimated, in agreement with direct microscopic observations. The influence of bacteria on the formation of oxide films was monitored by ellipsometry following the film growth in situ. A strong inhibition of metal oxide film formation was observed, which was assigned to the decrease in oxygen concentration due to the presence of bacteria. It is shown that the irreversible adhesion of bacteria to the surface can be monitored ellipsometrically. Electrophoretic mobility is proposed as one of the factors determining bacterial attachment. The high sensitivity of ellipsometry and its usefulness for the determination of growth of interfacial bacterial films is demonstrated.
Antibodies to atrazine were labelled with glucose oxidase and used in colorimetric enzyme linked immunosorbent assays. Transparent aminosilanized indium tin oxide coated glass electrodes were derivatized with aminodextran covalently modified with atrazine caproic acid. The labelled antibodies were used to investigate the derivatized electrodes colorimetrically and the electrodes were use in an electrochemiluminescence flow injection analyser. Electrochemiluminescence immunoassay for atrazine in the range 0-10 ppb showed that it was possible to detect less than 0.1 ppb, the precautionary limit for pesticides in drinking water recommended by the European Commission.
Explore the source record for details and available documents.
It is shown that the interfacial free energy of adsorbed phospholipid layers is dependent on the interfacial inner potential difference and on the local pH at the surface. Gradients of potential and pH result in the onset of Marangoni hydrodynamic convective fluxes at the phase adjoining a phospholipid monolayer. It is proposed that the coupling between potential, pH and interfacial Gibbs energy can provide an elementary driving force for cell and organelle motility, phagocytosis and streaming effects. It is shown that the order of magnitude of the surface shear stress generated by surface tension gradients is sufficient to account for cytoplasmic streaming in cells.