Abstract
ABSTRACTHerein, we have designed and developed four luminescent mesoporous squaraine copolymers (PSQ‐X) based on substituted diaryl‐1,4‐diamine moiety with various heteroatom “X” such as CH2, O, S, and SO2 to demonstrate the effect of heteroatom on structural, thermal, electrochemical, and optical properties of copolymers. Synthesis has been achieved through a facile single step metal‐free poly‐condensation reaction using commercially available low‐cost monomers. All polysquaraines (PSQs) possess good thermal stability, crystallinity and low bandgap energy (2–3 eV). Utilizing the fluorescent nature of the PSQs, we have explored them as a “turn‐off” sensor for the selective and sensitive detection of picric acid among various nitro‐aromatic explosives via photoinduced electron transfer (PET) and inner filter effect (IFE) mechanism. The Stern–Volmer constant (KSV) for PA has estimated as 1.93 × 104, 1.92 × 104, 0.68 × 104, and 3.57 × 104 M−1 for PSQ‐CH2, PSQ‐O, PSQ‐S, and PSQ‐SO2, respectively, indicating that PA can quench the emission intensity of PSQ‐SO2 most efficiently with the detection limit in the nano‐molar range (LOD = 5.96 nM). Contact mode detection of PA has been also accomplished using economical and transportable fluorescent paper test strip devices for on‐site sensing, which can detect a minimum of 6.9 fg of PA.
Published Version
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