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K. Kato, A. Takatsu, N. Matsuda, R. Azumi, and M. Matsumoto
[Chem. Lett., 1995, pp.437-438, 1995]
A novel slab optical waveguide (SOWG) technique with a white light excitation source was applied to the spectroscopy of Langmuir-Boldgett (LB) monolayer samples. A SOWG was fabricated by an ion-exchange process form slide glass in molten potassium nitrate at 420°C for 30 min. A single or double layer assembly of mixture of Cd-icosanoate and Cu-porphyrin complex was transferred onto the SOWG by LB technique. The experimental setup is schematically shown in Figure 1. The white light excitation beam from 500 W xenon arc lamp was chopped and was in-coupled into and out-coupled from SOWG with a use of coupling prisms. Transmitted light through the SOWG was monochromated and was detected by a photomultiplier tube. Absorption spectra of a Cu-porphyrin complex in LB films at concentrations of 0.1 to 0.5 monolayers were observed in the wavelength range of 380 to 350 nm as shown in Figure 2. Polarized spectra giving information on the molecular orientation in the ordered thin films were also measured.
Fig. 1. Schematic diagram of the slab optical waveguide spectrometer. The SOWG was placed horizontally on a gonio stage. Micro-lenses (ML1,2) attached at the ends of optical fibers (F) were mounted on mechanical XYq-stages.
Fig. 2. Absorption spectra of Cu-porphyrin in the LB films. The solid line and the dotted one correspond to a concentration of 0.46 and 0.1 monolayer, respectively.