The development of aggregation-induced emission enhancement (AIEE) active nanoprobes without any synthetic complication for solution-state and organic thin-film transistor (OTFT)-based sensory applications is still a challenging task. In this study, the novel pyrene-incorporated Schiff base (5-phenyl-4-((pyren-1-ylmethylene)amino)-4H-1,2,4-triazole-3-thiol; PT2) with an AIEE property was synthesized via a one-pot reaction and was reported for detecting Zn 2+ and tyrosine in the solution state and OTFT. In the AIEE studies of PT2 (in CH 3 CN) at various water fractions (f w : 0− 97.5%), the existence of J-aggregation, crystalline changes, and nanofibers formation was confirmed by ultraviolet absorption/photoluminescence (UV/PL) spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and dynamiclight scattering (DLS) techniques. Similarly, PT2-based Zn 2+ detection and sensory reversibility with tyrosine were demonstrated by UV/PL studies with evidence related to crystalline/nanolevel changes in PXRD, SEM, TEM, AFM, and DLS data. Distinct decay profiles associated with the AIEE and sensory responses of PT2 were observed in time-resolved photoluminescence spectra. From the standard deviation and linear fittings of PL titrations, detection limits (LODs) of the Zn 2+ with PT2 and the tyrosine with PT2-Zn 2+ were estimated as 0.79 and 45 nM, respectively. High-resolution mass and 1 H NMR results confirmed 2:1 and 1:1 stoichiometry and binding sites of PT2-Zn 2+ -PT2* and tyrosine-Zn 2+ complexes. Moreover, the values of association constants determined by linear fittings were 4.205 × 10 −7 and 1.73 × 10 −8 M −2 , correspondingly. Optimization via the density functional theory disclosed the binding sites and suppression of twisted intramolecular charge transfer/photoinduced electron transfer (TICT/ PET) as well as the involvement of restricted intramolecular rotation in the AIEE and PET "ON-OFF-ON" mechanisms in the Zn 2+ and tyrosine sensors. Results from the B16−F10 cellular and zebrafish imaging of AIEE, Zn 2+ , and tyrosine sensors further attested the applicability of PT2 in biological samples. Finally, the PT2 and pentacene-incorporated OTFT devices were fabricated. The devices displayed more than 90% change in drain-source current when reacted with Zn 2+ with an LOD of 5.46 μM but showed no response to tyrosine, thereby confirming the reversibility. Moreover, the OTFT devices also demonstrated Zn 2+ ion detection in tap water and lake water samples.

Development of luminescent and nontoxic Pb-free perovskite quantum dots (PQDs) for quantification of toxic/nontoxic heavy metal ions has attracted much attention recently. In this paper, blue emissive Pb-free bare and poly(ethylenimine), oleic acid stabilized methylammonium tin tribromide quantum dots (MASnBr 3 QDs and PEI-OA-MASnBr 3 QDs) are developed via modified synthetic routes with fluorescent quantum yields of (Φ f ) of 8.7 and 14.6%, respectively. The particle size, structures, diffraction patterns, and surface potential of PQDs are investigated using a high-resolution transmission electron microscope (HR-TEM), powder X-ray diffraction (PXRD), dynamic light scattering (DLS), and zeta potential techniques. Photoluminescence (PL) investigations demonstrate agglomeration-mediated energy transfer at various precursor concentrations and water sensitivity of PQDs. At 20 μL precursor concentration in DMSO, both QDs exhibit diverse fluorescent quenching to Fe 3+ and Cr 6+ with linear regression between 1−500 μM and nanomolar detection limits (LODs). Estimated Stern−Volmer quenching constant values are on the order of 10 3 −10 4 M −1 higher than those of other ions. PL and time-resolved PL studies confirm involvement of dynamic and static quenching in quantification of Fe 3+ /Cr 6+ for MASnBr 3 QDs and PEI-OA-MASnBr 3 QDs, respectively. Agglomeration of PQDs, Sn 2+ /MA + cationic displacement by Fe 3+ /Cr 6+ , and the existence of metal-oxide/hydroxide layer above the surface of QDs are confirmed by HR-TEM, DLS, zeta potential, X-ray photoelectron spectroscopy, and energy-dispersive spectroscopy investigations and supported by the density functional theory optimization. Biocompatibility of PQDs is authenticated by the methyl thiazolyl tetrazolium assay and IC 50 interrogations with supporting results from time-dependent cellular imaging of Fe 3+ and Cr 6+ ions. Individual titrations of PQDs with Fe 3+ and Cr 6+ in tap, lake, and seawater samples display linear behavior with micro/nanomolar LODs. Fe 3+ and Cr 6+ in spiked real water sample experiments show exceptional PL recoveries (>100%), which agree with the inductively coupled plasma-mass analysis.

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