Mechanochemical synthesis of an AIE-TICT-ESIPT active orange-emissive chemodosimeter for selective detection of hydrogen peroxide in aqueous media and living cells, and solid-phase quantitation using a smartphone

Abstract

Hydrogen peroxide (H₂O₂), a signature compound for peroxide explosives, is an important reactive oxygen species (ROS) that plays a crucial role in the physiological processes of organisms. We report herein the design and solventless synthesis of a chemodosimeter, benzothiazole-derived unsymmetrical azine protected by 4-bromomethylphenylboronic acid (BTPAB), for the selective detection of H₂O₂ in a turn-on manner with an orange aggregation-induced emission (AIE). The probe, p-Cl-benzothiazole-diphenyl-azineboronic acid (BTPAB), was synthesized in four steps from 2-amino thiophenol and a suitably substituted salicylaldehyde derivative by adopting a green route, mechanochemistry. H₂O₂ spontaneously cleaves the benzylboronic acid group of BTPAB in 1% DMSO in PBS (10 mM, pH 7.4) medium to produce its precursor BTPA, which emits intense orange AIE and also exhibits photophysical phenomena, namely excited-state intramolecular proton transfer (ESIPT) and twisted intramolecular charge transfer (TICT). The probe was non-responsive to other ROS, cations, anions, and oxidizing and reducing agents. The high sensitivity of BTPAB towards H₂O₂ is attributed to a low limit of detection (LOD) of 3.9 × 10⁻⁸ M (1.3 ppb). The practical utility of BTPAB in H₂O₂ detection was demonstrated by spiking H₂O₂ in water samples collected from local water bodies and in blood serum. BTPAB could efficiently detect intracellular H₂O₂ as demonstrated by imaging in live HeLa cells. BTPAB was successfully demonstrated in solid-phase detection of H₂O₂ using TLC plates as the platform, a smartphone for image-capture and ImageJ analysis for a practical demonstration of the on-site quantitation of H₂O₂.