Luminescência de complexo de európio(III) intensificada por nanopartículas de prata: um potencial sensor luminescente

Abstract

The development of sensors for analytes detection which humans and the environment are exposed to can be optimized by optical sensors studies. These are devices that make the detection of a substance of interest generating a visible analytical sign like a color change, light emission or luminescence quenching. The present study investigated the emission intensification of europium tris betadiketonate complex with the ligand butyl methoxydibenzoylmethane (bmdm), [Eu(bmdm)3(H2O)2], by Metal-Enhanced Fluorescence (MEF) effect, using silver nanoparticles and exploring the possibility to apply this system on the detection of various inorganic ions. The complex was synthesized with 1:3 molar ratio of Eu:bmdm, stoichiometry was confirmed by Complexometric Titration and Elemental Analysis, the coordination by Infrared Spectroscopy and the visible emition by Photoluminescence Spectroscopy. The silver nanoparticles were synthesized in aqueous solution using pectin as reducing and capping agent and its formation were confirmed by monitoring surface plasmon resonance by Ultraviolet and Visible Spectroscopy. The nanoparticles size was estimated by Transmission Electron Microscopy images and presented diameters between 20 and 50 nm, depending on the synthesis conditions. Different methodologies to extend the particles stability were also explored and the application of citric acid as capping agent was the better one. The presence of Cu2+, Fe2+, Fe3+, CrO42-, Cr2O72-, H2PO4- and HPO42- in a 100 µmol L-1 complex dispersion exhibited a clear quenching in the emission, with the analytes being detected between 10 and 1000 µmol L-1. The MEF effect was observed in the appropriate proportion of complex and nanoparticles and made possible to detect the analytes applying a concentration of europium(III) up to 25 times lower than the detection without nanoparticles. It was also confirmed the possibility of detection and quantification using Digital Image Colorimetry, resource that allows analysis in a faster and more accessible way. These results suggest that the combination of these materials has a great potential for the development of devices and analytical methods for detection and quantification of some inorganic ions in aqueous dispersions. The application of MEF effect can be a great advantage, because it makes it possible to use less luminescent material which can make the methods and devices developed with these material cheaper and more efficient, and can also reach lower detection and quantification limits of the analytes.