Abstract
Recently, based on the principle of proton transfer, the binary system composed of dye with a ionizable hydrogen atom and deprotonic reagent has become as an important type of water-jet rewritable paper (WJRP) for saving papers. In this paper, azo dye with sulfonamide group (2,2′-bis 4-methylbenzenesulfonamido azobenzene, SA) has been designed to detect moisture in organic solvents and prepare WJRP with yellow texts on a dark red background based on the water-inducing protonation between N–H of azo dye deprotonated by anions (e.g., H2PO4− and OAc−). The color and absorption spectra of the deprotonated species were restored to their original state after the reaction of the anionic dye with water. The interaction mode of azo dye and anion was verified by the titration of UV–Vis and 1H NMR spectroscopy. These findings show opportunities for the development of colorful and environmental friendly WJRP.
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