From colorimetric chemosensors to metal nanoparticles using two new tyrosine Schiff-base ligands for Cu2+ detection

Abstract

Two new tyrosine Schiff-base ligands 1 and 2 bearing an indole or a thianaphthene moiety were synthesized and characterized by elemental analysis, 1H NMR, IR spectroscopy (KBr discs), MALDI-TOF-MS spectrometry, UV–Vis and fluorescence emission spectroscopy. The sensing ability towards Ca2+, Zn2+, Cd2+, Cu2+, Ni2+, Hg2+ and Al3+ metal ions was explored in absolute ethanol. Both compounds showed colorimetric properties in the presence of Cu2+ ions, changing their colour from light yellow to purple (1) and dark pink (2). The minimal amount of Cu2+ that compounds 1 and 2 could quantify was ca. of 8ppm.In order to obtain new nanomaterials based on the reported systems, new gold and silver nanoparticles were successfully synthesized by self-reduction of compound 1 in an aqueous alkaline environment. The nanoparticle formation was demonstrated by UV–Vis and fluorescence emission spectroscopy, dynamic light scattering and transmission electron microscopy (TEM). TEM images of AgNPs and AuNPs showed sizes of 12±3.5nm with monodispersed distribution, and 7.50±6nm with asymmetric average distribution, respectively. In the case of gold nanoparticles the polydisperse distribution suggested some nanoparticle aggregation.