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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 17:47 |
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Conference: Bucharest University Faculty of Physics 2002 Meeting
Section: Optics, Spectroscopy, Plasma and Lasers
Title:
Electronic mechanisms in mixed valence metal doped
polymers for optical applications
Authors:
M.Bulinski*, A.Nedelcu*, Cristina Kuncser**, G.Filoti***
Affiliation:
* Bucharest University, Faculty of Physics, Dept. of Optics, POB MG-11
** Secondary School “N.Teclu”, Bucharest
***INCDFM, PO Box MG 07, 76900, Bucharest
E-mail
Keywords:
Abstract:
Mixed valence metal doped polymers represent a new class of metal-organic materials with potential applications for the non-liniar optics and opto-electronics. The ferric chloride doped polyvinyl alcohol (Fe:PVA) and the dichromate polyvinyl alcohol (DCPVA) were reported as convenient low cost materials for the real time holography. In spite of high diffraction efficiency, they present a relatively low sensitivity. The electronic mechanisms responsible for the real time recording process in Fe:PVA were previously explained [1-4]. Low exposure energies induce a variation of the refractive index whereas optical absorption becomes significant at higher energy. The refractive index variation with the exposure energy is related to the local change in the valence of the metal ion, e.g. to the change of the iron oxidation state from Fe(III) to Fe(II) via an electron transfer from the polymer matrix to the metal ion. Therefore ions with a larger difference in the valence states are expected to increase both the material sensitivity and diffraction efficiency.
Fe, Sn, Sb and their combinations were used as metal doping ions. Optical absorption, m-line spectroscopy and Mossbauer spectrocopy measurements were performed in order to corroborate the optical and the electronic parameters. Preliminary studies have shown that contrary to the Fe case, the electronic transfer under the UV exposure in the Sb and Sn case are reversed (i.e inducing a higher valence), namely Sn(II)Sn(IV) and Sb(III)Sb(V). The best performances are to be obtained when the ion is firstly stabilized in the optimal valence state. This requirement is highly dependent on the preparation conditions as well as on the metal-salt/solvent and the polymer. Various PVA, PAA, PMMA and PS polymers were used. Doped polymers including water molecules show most suitable electronic transfer processes and among these the doping complex Fe/Sb present improved and attractive performances, compared with the classical Fe:PVA and DCPVA.[1-3]
1. V. Kuncser, G. Filoti, R. Podgorsek, M. Biebricher, H. Franke, "The Diffraction Efficiency in Fe:PVA explained by Mossbauer Spectroscopy" J Phys. D. Appl. Phys. 31, pp. 2315-2318, 1998
2. V. Kuncser G.Filoti, A.Avramescu, R.Podgorsek, s.a., J. OF ALLOYS AND COMP.257(1997)
3. M. Bulinski, I. Iova, A. Belea, V. Kuncser, G. Filoti, J. Mat. Sci. Lett 19(2000),pp.27-28
4. M. Bulinski, V. Kuncser, I. Iova, A. Belea, H. Franke, G. Filoti, SPIE – 4068-03 (2000) pp.17-25
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