A simple and efficient colorimetric anion sensor based on a thiourea group in DMSO and DMSO–water and its real-life application

An efficient colorimetric sensor with a thiourea moiety as binding sites and p-nitrophenylhydrazine as a signaling unit has been synthesized by only one single-step procedure. Selectivity for anions with the distinct geometry (tetrahedral, trigonal planar and spherical) has been investigated in dry DMSO and even in DMSO/H2O (95:5, v/v) solutions through the naked-eye experiment, UV–vis titration and 1H NMR titration techniques. In particular, the fluoride of toothpaste can be detected qualitatively by the sensor 1.