Biomedical subjects

Philip N Bartlett

Publications and source records attributed to Philip N Bartlett.

8 recordsLinked to original sources

PubMed2006

Sculpted substrates for SERS.

Sculpted SERS-active substrates are prepared by assembling a closed packed monolayer of uniform polystyrene colloidal particles (diameter 350 to 800 nm) onto an evaporated gold surface and then electrodepositing gold through this template to produce films with controlled thicknesses, measured as fractions of the sphere diameter, d. The resulting surfaces consist of a regular hexagonal array of interconnected spherical cross-section dishes. The role of localised plasmons in determining the SERS enhancement factor obtained for benzene thiol adsorbed onto the surfaces is then investigated by correlation of the UV-visible reflectance spectra, 400 to 900 nm, measured at the same positions on the substrate surfaces, with the SERS spectra. The results are interpreted in terms of the relative contributions of plasmons that are free to propagate across the top surface and those trapped within the dishes of the sculpted surface.

Journal Article↗

PubMed2005

Wetting of regularly structured gold surfaces.

In this study we report results for a systematic study of the wetting of structured gold surfaces formed by electrodeposition through monolayer templates of close-packed uniform submicrometer spheres. Removal of the template after deposition leaves a regular hexagonal array of sphere segment pores where the depth of the pores and, thus, the topography of the surface are controlled by the thickness of gold deposited through the template. We find that, as the thickness of the porous film increases up to the radius of the pores, the apparent contact angle for water on the surface increases from 70 degrees on the flat surface to more that 130 degrees , and then with increasing thickness above the radius of the pores the apparent contact angle decreases back toward 70 degrees . We show that these changes in the apparent contact angle agree with the model of Cassie and Baxter for nonwetted surfaces even though the gold itself is hydrophilic. We also show that the apparent contact angle is independent of the diameter of the pores over the range 400-800 nm. This is the first reported example showing the change of a hydrophilic surface (theta; < 90 degrees ) into a hydrophobic surface (theta; > 90 degrees ) purely by control of the surface topography. The role of the pore shape and size in stabilizing the nonwetting (Cassie-Baxter) droplet on the surface is discussed.

Journal Article↗

PubMed2003

Measurement of the kinetic isotope effect for the oxidation of NADH at a poly(aniline)-modified electrode.

Kinetic isotope measurements using [4,4-2H2]NADH and [4-1H, 4-2H]NADH have been used to investigate the mechanism of the electrochemical oxidation of NADH at poly(aniline)-poly(vinyl sulfonate)-modified electrodes. The experiments show a primary kinetic isotope effect for the reaction of 4.2. This is consistent with literature values for the corresponding isotope effect for the oxidation of NADH by two-electron oxidants in homogeneous solution. The result demonstrates that transfer of H from NADH to the modified electrode occurs in the rate-limiting step within the reaction complex.

Aniline Compounds↗

PubMed2003

A micromachined calorimetric gas sensor: an application of electrodeposited nanostructured palladium for the detection of combustible gases.

Palladium films with regular nanoarchitectures were electrochemically deposited from the hexagonal (H1) lyotropic liquid crystalline phase of the nonionic surfactant octaethyleneglycol monohexadecyl ether (C16EO8) onto micromachined silicon hotplate structures. The H1-e Pd films were shown to have high surface areas (approximately 28 m2 g(-1)) and to act as effective and stable catalysts for the detection of methane in air on heating to 500 degrees C. The response of the H1-e Pd-coated planar pellistors was found to be linearly proportional to the concentration of methane between 0 and 2.5% in air with a detection limit below 0.125%. Our results show that the electrochemical deposition of nanostructured metal films offers a promising approach to the fabrication of micromachined calorimetric gas sensors for combustible gases.

Journal Article↗

PubMed2002

Detection of hydrogen peroxide at mesoporous platinum microelectrodes.

Mesoporous (H(I)-ePt) platinum microelectrodes electrodeposited from the hexagonal (H(I)) lyotropic liquid crystalline phase are shown to be excellent amperometric sensors for the detection of hydrogen peroxide over a wide range of concentrations. Good reproducibility, high precision, and accuracy of measurements are demonstrated. Mesoporous microelectrodes retain the high rates of mass transport typical of conventional microelectrodes, and their high real surface area greatly enhances their catalytic activity. This unique combination of properties overcomes the limitations of previous amperometric hydrogen peroxide sensors and yields outstanding qualitative and quantitative results.

Journal Article↗

PubMed2002

A method for the determination of enzyme mass loading on an electrode surface through radioisotope labelling.

A direct method has been developed for the quantitation of the amount of immobilised enzymes on biosensor surfaces. This quantity is of key importance in establishing the activity, kinetics and optimal immobilisation conditions in the construction of both amperometric and optical biosensors. Recombinant L-lactate dehydrogenase incorporating both a biosynthetically introduced radiolabel, 3H-leucine, and a hexahistidine peptide tag was immobilised on a poly(aniline) composite film and then quantitated by liquid scintillation counting. It was found that enzyme mass loading was proportional to the concentration of LDH in solution, and also depended on the morphology of the composite film. The LDH mass loading on the composite film doubled when a surface cysteine containing variant was used, possibly due to the covalent attachment of the cysteine to the diiminoquinoid rings of the poly(aniline).

Aniline Compounds↗

PubMed2002

Immobilisation of enzymes on poly(aniline)-poly(anion) composite films. Preparation of bioanodes for biofuel cell applications.

Immobilisation of enzymes is important for applications such as biosensors or biofuel cells. A poly(histidine) tag had been introduced on the C terminus of a lactate dehydrogenase enzyme. This mutant enzyme was then immobilised onto poly(aniline) (PANi)-poly(anion) composite films, PANi-poly(vinylsulfonate) (PVS) or PANi-poly(acrylate) (PAA). The NADH produced by the immobilised enzyme in the presence of beta-nicotinamide adenine dinucleotide (NAD(+)) and lactate is oxidised at the poly(aniline)-coated electrode at 0.05 to 0.1 V vs. saturated calomel electrode (SCE) at 35 degrees C.

Aniline Compounds↗

PubMed2002

The design of dehydrogenase enzymes for use in a biofuel cell: the role of genetically introduced peptide tags in enzyme immobilization on electrodes.

The immobilization of the mutants of L-lactate dehydrogenase (LDH) on poly(aniline) (PANi) composite films has been investigated. Mutants possessing peptide tags of varying charge and nucleophilicity were created to probe the nature of the interaction between the protein and PANi. These results are significant for the development of a 'generic' approach to the immobilization of enzymes and other proteins.

Bioelectric Energy Sources↗