Synthesis of novel acylthioureas bearing naphthoquinone moiety as dual sensor for high-performance naked-eye colorimetric and fluorescence detection of CN- and F- ions and its application in water and food samples

In this study, six new acylthiourea, bearing naphthoquinone moiety, sensors were synthesized in high yield (88-96%) and characterized using H-1/C-13 NMR, FT-IR and HRMS techniques. All synthesized sensors (4a-f) showed shifts in absorbance and colorimetric changes by CN-, F-, AcO-, and H2PO4-. However, 4e showed a chromogenic different sensitivity response to CN- and F- against competing anions such as AcO- and H2PO4- in DMSO. Furthermore, CN- added 4e showed an increase at the emission intensity and intensive fluorimetric color change was observed in UV-light (lambda ex. 365 nm). All sensors showed chromogenic selectivity towards CN- in aqueous solutions (in DMSO/H2O: 1:1, v/v). Interaction mechanisms between 4e and CN- and F- anions were investigated by experimental studies using various spectroscopic methods such as UV/Vis, fluorescence, H-1/F-19 NMR, and DFT calculation. The results showed that CN- interacts with 4e by the main mechanism as nucleophilic addition of cyanide to 3,5-dinitrophenyl moiety while F- caused an occurrence of imidazole ring-closing due to deprotonation of NH2. LOD values are reported as 2.7 mu M for sensor 4e. Moreover, interaction studies were carried out on food sample such as bitter almond, sprouting potato and apricot seed. Furthermore, UV/vis responses were obtained between sensors (4a-f) and the cations, and found selectivity towards Hg2+ in DMSO.