A triple-chromophore based NIR fluorescent chemodosimeter with configurable opto-chemical logic gate functions for multi-analyte recognition of N2H4, CN−, and ClO− in real samples

Abstract

Developing structurally simple, near-infrared (NIR)-emitting organic fluorescent probes capable of simultaneously detecting multiple analytes remains challenging. Herein, we reported a dual donor-π-acceptor (D′-D-π-A) type NIR-chemodosimeter, TPB with a large stokes shift (ca. 250 nm) based on a novel triphenylamine-phenothiazine-benzothiazole multichromophoric system. With its dual reactive sites i.e. an electrophilic β-vinylic carbon and an oxidizable sulfur atom, TPB demonstrated multi-analyte responsiveness towards N₂H₄, CN⁻, and ClO⁻ through distinct fluorescence read-outs. Photophysical analysis revealed ratiometric sensing for N₂H₄ and CN⁻ with emission colors shifting from faint red to turquoise and light blue, respectively. In contrast, ClO⁻ triggered fluorescence quenching, resulting in complete disappearance of emission color. TPB displayed high sensitivity with minimal interference and exhibited low limit of detection (LOD) values of 0.065 μM, 0.117 μM, and 0.63 μM and rapid response times of 5 min, 2 min, and 12 min, for N₂H_4, CN⁻ and ClO⁻, respectively. Comprehensive ¹H/¹³C NMR, HRMS analyses, and TD-DFT studies were conducted to support the proposed mechanistic pathways. The optical responses acquired by sequential analyte interactions ensued us to devise multifunctional molecular logic circuits (YES, NOT, PASS 0, NOR) on a unimolecular platform. To enhance practicality, TPB was incorporated into test strips, allowing solid-phase real-time detection of these analytes. Furthermore, TPB successfully detected N₂H₄ in various soil-samples, demonstrating its effectiveness in environmental monitoring.