Planar patch-clamp is a two-dimensional variation of traditional patch-clamp. By contrast to classical glass micropipette, the seal quality of silicon patch-clamp chips (i.e. seal resistance and seal success rate) have remained poor due to the planar geometry and the nature of the substrate and thus partially obliterate the advantages related to planar patch-clamp. The characterization of physical parameters involved in seal formation is thus of major interest. In this paper, we demonstrate that the physical characterization of surfaces by a set of techniques (Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), surface energy (polar and dispersive contributions), drop angles, impedance spectroscopy, combined with a statistical design of experiments (DOE)) allowed us discriminating chips that provide relevant performances for planar patch-clamp analysis. Analyses of seal quality demonstrate that dispersive interactions and micropore size are the most crucial physical parameters of chip surfaces, by contrast to surface roughness and dielectric membrane thickness. This multi-scale study combined with electrophysiological validation of chips on a diverse set of cell-types expressing various ion channels (IRK1, hERG and hNa(v)1.5 channels) unveiled a suitable patch-clamp chip candidate. This original approach may inspire novel strategies for selecting appropriate surface parameters dedicated to biochips.

The use of filters to block interfering gases from reaching the surface of the sensing element is an effective manner to improve selectivity of gas sensors. Different types of filters are discussed. As examples, applications of active and passive filtering membranes are considered.

In this work, we report on the effect of noble metal doping (namely Pd or Pt) on the optical properties of SnO2 thin films. The optical constants (n and k) of the films, as a function of noble metal nature and content, were obtained using variable angle spectroscopic ellipsometry in the ultraviolet-visible-near infrared (UV-vis-NIR) regions. Ellipsometry analysis showed that we can tune the optical constants of SnO2 films by changing Pt or Pd doping concentration. In particular, their refractive index increases from 1.6 to similar to 2 while varying Pt content from 3 to 12 at. %. The origin of this optical behaviour was correlated to the microstructure change induced by metal doping. X-ray diffraction (XRD) was used to investigate the effect of doping on SnO2 lattice parameter, on crystallite size and on film preferential orientation. Atomic force microscopy (AFM) was used to estimate the surface roughness of the films. A metal concentration of similar to 3 at.% (for both Pt and Pd), which is known to yield the highest SnO2 gas sensing response, was found to correspond to the highest contraction of the lattice parameter of the films. Finally, the energy band gap of undoped SnO2 thin films (estimated to 4 eV) was found to shift to lower value while increasing doping concentrations. (C) 2009 The Japan Society of Applied Physics DOI: 10.1143/JJAP.48.072501

New gas sensitive MIS structures Pt/Al2O3(M)/p-Si, where M=Pt, Rh, with granular dielectric Al2O3 layers doped with noble metals were obtained by an aerosol pyrolysis method. Surface morphology and composition of the structures were studied by TEM, AFM and EPMA. Sensor properties of the MIS structures were studied towards reducing gases (1000ppm H2, 300ppm CO, 1000ppm CH4 in air) at 100 and 200°C. The Pt/Al2O3(M=Pt, Rh)/Si structures showed a very high sensor response to reducing gases. A shift of C–V characteristics was up to 2.5V under CO, 2.2V under hydrogen and 0.7V under methane. High values of shift of C–V curves can be related with cooperative influence of a change of surface state density in dielectric layer, reduction of platinum electrode and dipole layer formation.

This article explores the possibilities of using Sb doped SnO2 thin films as potential electrode substrates for biosensors. Two series of electrodes were modified with electrogenerated functionalised polymeric films. The polymers investigated were biotinylated poly(ruthenium pyrrole) and poly(pyrrole benzophenone). AFM studies show polymer morphologies depending on the nature and roughness of the substrates.

Semiconductor gas sensor stability and selectivity can be improved by using catalytic filtering membranes to avoid the gas interference. The filtering membranes of pure and Pt or Ru doped Al2O3 with various thickness (9-53 nm) were deposited on the surface of SnO2(Pd) films by aerosol pyrolysis method. Phase composition and microstructure of the films were studied by XRD, AFM and EPMA. Sensors properties of SnO2(Pd)/Al2O3 and SnO2(Pd)/Al2O3(M) structures (M = Pt, Ru) were studied under H-2, CH4 and CO-air gas mixtures at 100-300 degrees C. All membranes reduce significantly sensitivity to CO and increase the sensitivity to CH4 at 200 degrees C. Ru-doped membranes significantly reduces the sensitivity to H-2. The sensitivity and response time considerably depend on membrane thickness. (c) 2005 Elsevier B.V. All rights reserved.

Thin polycrystalline SnO2 films were obtained by magnetron sputtering with subsequent oxidation and then doped with platinum by laser ablation method. It was observed that surface doping with platinum improves significantly the material's sensitivity to hydrogen. Sensor properties of SnO2(Pt) films were investigated in a temperature range 100–350°C in hydrogen–air mixtures containing 20–2000ppm of H2. Optimal doping parameters (thickness of platinum films and energy density of laser radiation) were determined.