Europium based luminescent hybrid films for metal detection: A potential Cu(II) sensor

F. IGLESIAS; M. BERNARDI; S. BARI; B. C. BARJA

La Serena

Conferencia; X ELAFOT (Latin-American Meeting on Photochemistry and Photobiology; 2010

Europium-based luminescent hybrid films for metal detection: a potential copper (II) sensor (Oral Presentation )     Fabricio Iglesias, Milagros Bernardi, Sara Bari and Beatriz Barja   INQUIMAE and Depto. Química Inorgánica, Analítica y Química Física. Facultad de Ciencias Exactas y Naturales. UBA. Pabellón 2. Ciudad Universitaria. C1428EHA Buenos Aires. Argentina   Keywords: europium, films, copper   Lanthanide ions display a well-defined luminescence characterized by narrow and highly structured emission bands with lifetimes in the millisecond timescale1. Strongly luminescent materials are obtained by incorporating lanthanide complexes in hybrid matrices prepared from organic silanised precursors2. huf hua In this work we synthesized a bridged polysilsesquioxane hybrid in which a highly luminescent Eu(III) complex of 2,6,-piridindicarboxylic acid is grafted covalently to the backbone of the silica network. Gels were synthesized with and without a templating agent (CTAB) to study the influence of the porosity of the materials. The Eu(III) luminescent hybrid sols obtained were deposited on glass slides by dip-coating, left ageing for 20 days and thermally treated at 60oC. Luminescence quenching experiments with templated (TF) and non-tempated (NTF) films were performed in-situ by the addition of aqueous solutions of Fe(III), Co(II), Ni(II) and Cu(II) (lexc= 290 nm, lem= 615 nm). Linear Stern Volmer plots were obtained for the TF being the constants KSV = 2.5.105 M-1, 8027 M-1, 6313 M-1 and 4075 M-1 for Cu(II), Ni(II), Fe(III) and Co(II), respectively. Cu(II) showed an unusual deactivation efficiency when compared with the rest of the metals, attaining detection limits of  almost 50 ppm for 10 % deactivation. Stern Volmer plots for NTF showed a downward curvature for similar Io/I ratios which could be fitted to Freundlich isotherms. NTF recovered almost 100% of their original Io value when washed with water, independently of the metal, indicating that physisorption could be the mechanism responsible for the deactivation of the luminescence. This result is in line with a lower porosity and therefore accessibility of the metal ions to the emissive Eu(III) centers in the NTF. huf hua