Luminescent sensor based on the lanthanide-fibroin composite

This work aims to produce luminescent sensors based on lanthanide ions and silk fibroin composite films. Associating the physicochemical properties of fibroin with the spectroscopic properties of lanthanide ions can be a strategy to develop a new generation of biocompatible and biodegradable sensors with high transparency in the visible region. The results presented herein are a natural consequence of a previous study that used europium ions as structural probes in the composite fibroin matrix and investigated their potential application as photonic devices. Here, highly transparent thin films containing the silk fibroin matrix and an Eu3+ complex were produced by dip-coating under controlled conditions. Europium thenoyltrifluoroacetonate was employed as the luminescent component of the proposed sensor. The films were characterized by electronic spectroscopy in the UV-Vis region and photoluminescence. The effect of complex insertion on the refraction index of the silk fibroin film was studied. The results showed a high-intensity emission that is characteristic of europium beta-diketone chelates, and the intensity of the D-5(0) -> F-7(2) transition depended on the ammonia vapor concentration. To understand the whole process, different composite films were prepared, and the results corroborated the potential use of this system as a photonic sensor of vapors.