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

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