Engineering a Two-in-one Ni(II)-azophenine switch: Intelligent Lab-on a-box device for decentralized recognition event

Abstract

A new Ni2+ complex of an azophenine-based sensory receptor, CN-1•Ni2+ is judiciously designed for selective aqueous phase fluoride recognition based on specific hydrogen bonding interaction with sharp chromogenic variation from brownish orange to purple. The mechanistic pathway of interaction has been thoroughly investigated via ESI-MS, FT-IR, differential pulse voltammetry (DPV) studies with theoretical DFT support and Loewdin spin population analysis. The detection limit was acquired to be 148 ppb, which is lower than the WHO permissible limit. The real-time sensitivity of the probe has been displayed by TLC strip-based solid-state sensing assay. The probe is also responsive towards recognition of fluoride from various real field water specimens with promising recoveries (95–119%). One step ahead, the chemically obtained outcomes have been extensively synchronized with electronic circuitry to fabricate lab-on a-box based Layman’s prototype for on-spot, decentralized detection of fluoride, which would be beneficial for the end users, particularly in the fluoride endemic areas. Moreover, based on the reversible spectroscopic outcome, herein AND-NOT-OR-NOR gate-based complex logic circuitry and sequence-dependent molecular keypad lock has been fabricated. In addition, silica gel supported composite material, CN-1•Ni2+@SG has been prepared for effectual remediation of aqueous fluoride below safe limit. Thus, the present work relies on recognition as well as proficient remediation of aqueous fluoride based on selective tuning of acidity, validating the ‘Two-in-one’ approach.