Bis naphthalene derived dual functional chemosensor: Specific signalling for Al3+ and Fe3+ ions with on-the-spot detection, bio-imaging, and logic gate applications

Abstract

Bis naphthalene derived Schiff base (R) was achieved as a dual functional chemosensor for highly specific recognition of Al3+ and Fe3+ ions in DMSO-H2O medium. The sensor R acts as a single scavenger to detect dual analytes by colorimetric and fluorimetric techniques through a switch “off–on” process. The probe R detects Al3+ by enhancing the fluorescence emission and Fe3+ by an increase in the absorbance emission respectively, via in restriction of CN rotation, blockage of CN isomerization and inhibition of photoinduced electron transfer (PET) assisted with Excited State Intramolecular Proton Transfer (ESIPT) processes. The binding stoichiometry ratio was determined to be 1:1 complexation by job’s plot method supported by 1H NMR titration, IR studies and DFT analysis. The limit of detection (LOD) was calculated to be 1.7 µM and 23.2 µM for the detection of Fe3+ and Al3+ by probe R through colorimetric and fluorimetric techniques respectively. Further, sensor R was practically applied for the detection of Al3+ and Fe3+ in water samples and bio-imaging of microbial pathogens. Especially, colour change of sensor R on the binding of Al3+ was demonstrated in various applications like paper strip, silica-gel supported analysis and smartphone-colour assist technique.