A Schiff base-based ratiometric chemosensor conjugated NBD derivative with the large stock shift for formaldehyde detection

A simple colorimetric chemosensor conjugated NBD derivative was synthesized for the detection of formaldehyde (FA) in DMSO/KHP buffer (50% v/v, pH 4.0). Phenylenediamine was designed as a reactive site for FA through the formation of Schiff base. Upon the addition of FA, the color solution of the sensor 1 changed from yellow to deep-purple, observed by naked-eyes. The ratiometric sensor in the presence of FA exhibited an intense absorption band of the red shift from 485 nm to 582 nm. The sensor was highly selective toward FA among other reactive carbonyl species, reactive oxygen species, amino acids, and food additives in 50% DMSO/KHP buffer. The sensor could be utilized in quantitative analysis for FA with the linear relationship in the concentration range of 0-6.5 mM. The product of the sensor and FA was also investigated by H-1 NMR, C-13 NMR, and HRMS analysis. Furthermore, the paper-based sensor was successfully developed for FA sensing. (C) 2020 Published by Elsevier Ltd.