Galvinol as ratiometric naked-eye colorimetric moisture sensor: Synthesis process development, applications and mechanistic studies

Abstract

Moisture detection through a simple colorimetric approach using molecular materials has been a cost-effective and user-friendly technology of choice as high moisture and humidity conditions lead to serious issues across various fields. However, the poor availability of such efficient molecular systems is a serious concern, and hence the need is quite evident. In this regard, the galvinol (GALH) molecule has been explored as a highly responsive colorimetric moisture-sensing in liquid and gaseous systems. Notably, it has been synthesized in a multigram scale via an unexplored demethylative C-C coupling of butylated hydroxyl toluene (BHT). The deprotonated form of GALH (GAL-) has been investigated as a reversible colorimetric moisture sensing platform with limits of detection (LOD) for water (H2O) in acetonitrile and tetrahydrofuran solvents as 0.0022 and 0.0031% v/v, respectively. The moisture sensing mechanism is based upon the competitive ion pairing of GALH with tetra-n-butylammonium fluoride and H2O during the protonation/deprotonation process. The developed moisture sensing probe has shown its universal applicability during the fabrication of polystyrene resin anchored solid medium device for relative humidity detection, color indicating moisture absorbing silica gel preparation, paper strip-based moisture detection in organic solvents and soil as real sample analysis, moisture erasable inkjet-printing and inkless writing.