A rare combination of dual static and dynamic fluorescence quenching mechanisms is reported, while sensing the nitroexplosive trinitrotoluene (TNT) in water by a cationic conjugated copolymer PFPy. Since the fluorophore PFPy interacts with TNT in both ground state as well as the excited states, a greater extent of interaction is facilitated between PFPy and the TNT, as a result of which the magnitude of the signal is amplified remarkably. The existence of these collective sensing mechanisms provides additional advantages to the sensing process and enhances the sensing parameters, such as LoD and highly competitive sensing processes in natural water bodies irrespective of the pH and at ambient conditions. These outcomes involving dual sensing mechanistic pathways expand the scope of developing efficient sensing probes for toxic chemical analyte and biomarker detection, preventing environmental pollution and strengthening security at sensitive locations while assisting in early diagnosis of disease biomarkers.

Bilirubin (BR) is a potent biomarker for jaundice and liver malfunction. However, its quantitative determination remains a bottleneck due to the interference of numerous biomolecules present in the blood serum. To overcome this, a conjugated polyfluorene derivative, poly1,1′-((2,7-dimethyl-9H-fluorene-9,9-diyl)­bis­(hexane-6,1-diyl))­bis­(1H-benzo­[d]­imidazole) (PFBZ), was synthesized by incorporating it with a specific receptor, benzimidazole, for BR detection using a low-cost and straightforward oxidative coupling polymerization. The PFBZ polymer spontaneously forms nanoparticles in an aqueous medium and unveils excellent sensitivity toward BR in an aqueous PBS medium with a limit of detection of 6.9 pM, which is far less than the clinically relevant range. The sensing mechanism is based on probe–analyte interaction chemistry and Förster resonance energy transfer, which were confirmed from both experimental and theoretical studies. This platform offers excellent sensitivity and selectivity, which motivated us to successfully explore the quantitative determination of BR in real serum samples. This method of sensing is straightforward, noninvasive, and can be used as a biomedical sensor to diagnose the onset of jaundice and liver malfunction.

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