Irena Šimkienė

Magnetic circular dichroism of iron porphyrin

Magnetic circular dichroism of iron porphyrin aqueous solutions was studied using a photometric ellipsometer with photoelastic modulator of light polarization in the spectral range 350-750 nm in magnetic fields up to 350 mT. Buffered aqueous solutions of iron porphyrin with pH-values equal to 1.7, 3.6 and 6.8 and concentration 0.1-1.0 mM were prepared by dissolving Fe(III) meso-tetra(4- sulfonatophenyl)porphine chloride. The spectra of magnetic circular dichroism were observed in the region of Soret band (390-420 nm) and Q-bands (500-700 nm). The lineshape analysis of magnetic circular dichroism spectra has shown that A-terms were dominant though a significant overlap masked the fine structure of the Q-bands. The magnetic circular dichroism signal was of order 1x10-2 cm-1/T in a linear approximation with respect to magnetic field. The data indicated that complete lifting of the degeneracy of the states involved in the corresponding optical transitions did not occurred in magnetic fields used. The model of the ground and excited states in iron porphyrin was discussed.

Studies of composite system of iron porphyrin immobilized on aminosilanized Si

Composite system of iron porphyrin (FeTPPS) on aminosilanized Si substrates was investigated by studies of surface morphology and optical response. Aminofunctionalized siloxane films on silicon substrates were produced from different sol-gel precursors prepared from 3-aminopropyltriethoxysilane (APTES) dissolved in water, ethanol and acetone. Immersion technique was used for the formation of APTES films. Aqueous solutions of FeTPPS were deposited on aminosilanized Si substrates. Topographic features of nanostructures in composite FeTPPS/APTES/Si system were investigated by atomic force microscopy (AFM) technique. High-resolution phase contrast imaging revealed the substructure of siloxane films on silicon substrates and nanoaggregates of FeTPPS immobilized on aminosilanized Si surface. Spectroscopic ellipsometry measurements were carried out in the region 1-5 eV in order to characterize the siloxane films and composite structures. The analysis of obtained results allowed one to conclude that FeTPPS molecules were attached to the surface by covalent bonds between the functional group of sulfonic acid SO3- of iron porphyrin and (-NH2H+)-group of APTES.