A colorimetric chemosensor for pyrophosphate based on mono-pyrenylurea in aqueous media

Research on pyrophosphate ions detection remains important because it plays crucial roles in various fields. A simple and new colorimetric sensor for pyrophosphate (PPi) based on mono-pyrenylurea ligand (L) has been designed and synthesized by a simple reaction of 1-pyrenemethylamine hydrochloride with p-nitrophenylisocyanate. In DMSO-15% H₂O solution and DMSO-15% HEPES (10 mM, pH = 7.2) buffer solution, L displayed a selective colorimetric response for pyrophosphate (PPi) against other anions by changing color from colorless to yellow. This recognition process was confirmed by UV-vis spectroscopy. Also, the colorimetric properties of L are attributed to the anion-induced deprotonation of the urea subunit as demonstrated by ¹H NMR titration method. Moreover, convenient test strips coated with L could be utilized to detect PPi in aqueous solution by naked-eye.