Etude de différentes méthodes de biofonctionnalisation pour la ...

III. Etudes du film Lan gmuir-Blodgett enzymatique
FTIR measurements were performed in the attenuated total
reflection (ATR) mode, This method
takes advantage of the evanescent waves to analyse a material in optical contact with an internal
reflection element (IRE). The IRE is a solid transparent to the infrared with a high refractive index (n >
2.5, generally) in order to fulfil the total reflection conditions. The probed depth is within the
micrometer range and depends upon the wavelength of the radiation, the incidence angle, and the
refractive indices of the IRE and of the materials to be analysed9. The ATR cell used in this work was
primarily designed to study water diffusion through thin polymer film deposited on the IRE10. As the
infrared beam penetrates the IRE under normal incidence, the adjustment is easy when changing from
one sample to another and no beam condenser is needed. The IRE was cut from a Ge piece (at
dimensions 65 x 20 x 2.25 mm) and bevelled at 22.5° in order to produce reflections under 45°
incidence. This geometry allows a total of 28 internal reflections (figure 1).
5.5 cm
Ge
crysta
T2.25 mm
6.5 cm
LB film
incident
ray
Figure 1. JR beam path in the Ge internal rejiexion
element on which LB 111m is deposited.
The FTIR spectra were recorded on a Nicolet 710 spectrometer maintained under dry air purge,
fitted with a liquid nitrogen-cooled MOT detector. Generally, 512 scans at a resolution of 4cm were
recorded to obtain a spectrum. As this spectrometer is a single beam device, a Ge background was
collected on each IRE prior to OTS deposition or LB film deposition.
2.4.2. Contact angle measurements
Contact angle measurements by the sessile drop method were carried out using a GBX Scientific
Instruments apparatus . A video camera equipped with an image analyzer visualized the shape of the
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