The effect of pH on the Langmuir monolayer behavior was
investigated for the poly(o-anisidine) (POAS)
conducting polymer. The Langmuir−Schaefer (LS) films were
prepared at pH 1 of the subphase, where
the doping during the monolayer formation was essential for the high
quality of the conducting polymer
film. The LS films of POAS were characterized by using Fourier
transform infrared spectroscopy, UV-vis
absorption, X-ray diffraction, and ellipsometry techniques. The
thickness of one monolayer of POAS film
was estimated to 24 Å by using X-ray reflectivity and ellipsometric
measurements. The uniformity of such
POAS LS films was investigated for the redoping in 1 M HCl (protonic
acid) for achieving the higher
conductivity. The conductivity of the POAS LS film was shown to
vary between 0.1 and 10-9 S/cm.
Direct
current through conducting LS films of POAS was observed as a function
of monolayers. Further, the
effects of different protonic acids on the electrical behavior of the
POAS LS films were also investigated
at length.
An in situ self-assembly technique with nanometre control over thicknesses and multilayered structures was used to manufacture the ultrathin films of polypyrrole (PPY). The PPY film was deposited on a polyanion, poly(styrene sulfonate) (PSS) modified surface as a function of time, previously PSS had been deposited on various substrates (glass, mica, indium-tin-oxide coated glass plates). Later, alternate PPY and PSS films were fabricated on such substrates using a layer-by-layer (LBL) technique. The glucose oxidase (GOD) molecules were also deposited on such self-assembled PPY films by the LBL technique. The PSS/PPY/GOD, PPY/PPY/GOD/poly(ethylene imine) (PEI)/GOD etc, film configurations were fabricated, and functionally as well as structurally characterized by UV-visible, electrochemical and scanning probe microscopy techniques, respectively. The results of a scanning probe microscopic study on the films were analysed to understand the molecular orientation of GOD on the PPY surface, and the dependence of the enzyme concentration for the depositing solutions. Moreover, the electrochemical studies performed provided information with respect to the electron transfer processes on the spatial arrangement of GOD molecules on the PPY surfaces. The immobilization of GOD on a conductive PPY represented a crucial and important step, and allowed us to construct the glucose-responsive biosensors.
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