A low-cost miniaturized optosensing platform for selective peroxyacid detection in aqueous solution based on sequential oxidation of a deep blue-fluorescence emitter

• A highly functionalized fluorescent chemoprobe based on isoquinoline was reported. • It displayed excellent recognition ability towards m-CPBA in 99 % aq. ACN solution. • The limit of detection was determined to be as low as 0.93 µM. • Comparative FT-IR, NMR , mass spectral, and DFT studies were performed. • Test-strips and an RGB-Arduino device were developed enabling real-time detection. The development of fluorescent organic small-molecular probes targeting m-Chloroperoxybenzoic acid (m-CPBA) detection is crucial to effectively mitigate associated health and ecological hazards. Isoquinoline scaffold, despite its inherent attributes, has not undergone thorough exploration as a fluorescence platform, primarily owing to synthetic complexities. In the current work, we described the design, synthesis, and utilization of a novel thiomethyl-appended isoquinoline-based chemoprobe (QN) for the chemosignaling of extensively used peroxy acid m-CPBA. QN exhibits high fluorescence quantum yield (Φ f = 0.54) and demonstrates excellent sensing ability towards m-CPBA in nearly aqueous solution via the intramolecular charge transfer (ICT)-off mechanism. It was proposed that m-CPBA promoted oxidative transformations of QN into corresponding sulfoxide and sulfone analogues contributes to its discriminative character towards m-CPBA. Comprehensive Fourier transform infrared (FT-IR), high resolution mass spectrum (HRMS) analyses, and density functional theory (DFT) studies were conducted to substantiate the proposed mechanistic pathways. The limit of detection of m-CPBA with QN was determined to be 0.93 µM. Furthermore, the practicality of QN was enhanced through integration into sensing test strips allowing solid-phase detection of m-CPBA. In addition, a low-cost optosensing device based on an open-source Arduino platform, interfaced with a red, green, and blue (RGB) color sensor has been developed which enables instant quantifiable analysis of varying m-CPBA concentrations in real-time conditions.