Spectrometric characterisation of the solid complexes formed in the interaction of cysteine with As(III), Th(IV) and Zr(IV)

The aminoacids play important roles in biological systems as they participate in key chemical reactions for life, usually involving complexation with metal and metalloid {metal(loid)} ions. In this work, the solid complexes prepared after mixing arsenic(III), thorium(IV) and zirconium(IV) solutions with l-cysteine at pH 8.0 were spectrometrically characterised. The X-ray diffraction, together with secondary electron microscopy/energy dispersive-X ray spectrometry, allowed us to obtain information about the crystallinity, morphology and elemental composition of the solid metal(loid)-cysteine complexes. Photoluminescence of the prepared solid complexes was also evaluated by confocal microscopy. The functional groups responsible of the complexation processes were elucidated by Raman and infrared spectrometry. The participation of the thiol group from the l-cysteine molecule in the complexation of As(III) was effectively noted by Raman spectrometry. Nonetheless, Th(IV) and Zr(IV) were bound to l-cysteine through the oxygen atoms of the carboxylate group, according to the FT-IR results. (C) 2014 Elsevier Ltd. All rights reserved.