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The novel pyrene-appended Schiff base probe L with aggregation-induced emissions (AIE) relevant to an increase in water fractions (0–90%) is synthesized and applied in sequentially detecting Cu2+ and CN−. The pyrene-based probe L firstly induces the excimer formation in the presence of Cu2+. However, the process can be reversed by sequentially adding CN−, which is demonstrated using the fluorescence "Off-On-Off" response in semi-aqueous media ethanol water (v/v = 7/3) under physiological pH (5 mM HEPES, pH 7.0). The Job's plot, mass analysis, 1H NMR titrations, and density functional theory (DFT) interrogations confirm the 2:1 stoichiometry of excimer complex L–Cu2+-L*, preferential binding atoms, and CN− tuned complex reversibility. Based on the photoluminescence (PL) titration, the association constant of L to Cu2+ is determined as 4.95 × 106 M−1. From standard deviation and linear fittings, the detection limits (LODs) of Cu2+ and CN− are estimated as 219 nM and 580 nM, respectively. The practicality of Cu2+ and CN− detection is demonstrated using a TLC plate and a blended polymer membrane through which significant color changes under a UV lamp can be monitored. Moreover, utility of the designed probe L towards biological application with low toxicity is demonstrated by detecting Cu2+ and CN− inside HeLa cells. The responses of the probe to Cu(II) ions were also verified using living HeLa cells imaging. [ABSTRACT FROM AUTHOR]

Novel anthracene-based Schiff base derivative (4-(anthracen-9-ylmethylene) amino)-5-phenyl-4H-1,2,4-triazole-3-thiol; AT2) is synthesized and utilized as an aggregation-induced emission-enhancement (AIEE) active probe to detect Zn2+ and Tyrosine. Ultraviolet-visible absorption/photoluminescence (UV-vis/PL) spectroscopy studies on the AIEE property of AT2 (in ethanol) with increasing water fractions (fw: 0–97.5%) confirm the J-type aggregation. Excellent sensor selectivity of AT2 to Zn2+ and its reversibility with Tyrosine are demonstrated with PL interrogations. 2:1 and 1:1 stoichiometry and binding sites of AT2-Zn2+ and Tyrosine-Zn2+ complexes are elucidated from Job plots, HR-mass, and 1H-NMR results. Nanomolar-level detection limits (LODs) of Zn2+ (179 nM) and Tyrosine (667 nM) and association constants (Kas) of 2.28 × 10−6 M−2 (for AT2-Zn2+) and 1.39 × 10−7 M−1 (for Tyrosine-Zn2+) are determined from standard deviation and linear fittings. Nanofiber formation in AIEE and aggregated/dispersed nanoparticles in the presence of the Zn2+/Tyrosine are supported by scanning-electron microscope (SEM), transmission-electron microscope (TEM), atomic-force microscope (AFM), and dynamic-light scattering (DLS) investigations. Density-functional theory (DFT) studies confirm an "On-Off" twisted intramolecular charge transfer/photo-induced electron transfer (TICT/PET) and "On-Off-On" PET mechanisms for AIEE and sensors, respectively. B16-F10 cellular and zebrafish imaging are conducted to support the applications of AIEE and sensors. [ABSTRACT FROM AUTHOR]

Abuse of new psychoactive substances (NPS) has become a health and social issue of global concern. p -Methoxyamphetamine (PMA)/ p -methoxymethamphetamine (PMMA) with fluoro- or chloro-derivatives of amphetamine and methamphetamine were among the most common drugs found in specimens from fatal cases in Taiwan during the January 2011 to December 2018 period. A liquid–liquid extraction sample preparation protocol with highly sensitive ultra-high performance liquid chromatography–tandem mass spectrometry approach was developed for the simultaneous analysis of seven phenethylamine-type drugs—PMA, PMMA, p -methoxyethylamphetamine, 4-fluoroamphetamine (4-FA), 4-fluoromethamphetamine (4-FMA), 4-chloroamphetamine (4-CA) and 4-chloromethamphetamine (4-CMA)—in postmortem blood and urine specimens. Separation by liquid chromatography was performed by Agilent Zorbax SB-Aq column. Tandem mass spectrometry was operated in Agilent Jet Stream Technology electrospray ionization in positive-ion multiple reaction monitoring mode. An analytical methodology was evaluated using drug-free blood and urine after fortification with 100–2,000 ng/mL of the seven target analytes. Average extraction recoveries were >80%; slightly higher ion suppression was observed for PMA and 4-CA; intra-/inter-day precision (% coefficient of variation) and accuracy were in the ranges of 0.52–12.3% and 85–110%, respectively. Limit of detection and lower limit of quantitation for these seven analytes were both in the 0.5–5 ng/mL range. Interference and carryover were not significant. This relatively simple methodology was found effective and reliable for routine identification and quantitation of these seven analytes in postmortem and antemortem blood and urine specimens received in 2018. Analytical data obtained from these actual cases indicated the following: (i) compared to findings reported during the 2007–2011 period, the use of substituted phenethylamine-type drugs decreased in 2018; (ii) ketamine and 7-aminonimetazepam (the main metabolite of nimetazepam) were the most common co-ingested substances in specimens containing PMA/PMMA, 4-FA/4-FMA, or 4-CA/4-CMA; and (iii) in drug fatalities, the concentration of PMA was significantly higher than the concentration of PMMA in both urine and blood, while the reverse was true in urine specimens from antemortem cases. [ABSTRACT FROM AUTHOR]

The homeostasis of short-lived reactive species such as hydrogen sulfide/hypochlorous acid (H 2 S/HOCl) in biological systems is essential for maintaining intercellular balance. An unchecked increase in biological H 2 S concentrations impedes homeostasis. In this report, we present a molecular probe pyrene-based sulfonyl hydrazone derived from pyrene for the selective detection of H 2 S endogenously as well as exogenously through a "turn-off" response in water. The structure of the receptor is confirmed by Fourier-transform infrared spectroscopy, 1 H and 13 C nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction studies. The receptor shows excellent green emission in both the aqueous phase and solid state. Quenching of green emission of the receptor is observed only when H 2 S is present in water with a detection limit of 18 nM. Other competing anions and cations do not have any influence on the receptor's optical properties. The efficiency of H 2 S detection is not negatively impacted by other reactive sulfur species too. The sensing mechanism of H 2 S follows a chemodosimetric reductive elimination of sulfur dioxide, which is supported by product isolation. The receptor is found to be biocompatible, as evident by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and its utility is extended to endogenous and exogenous fluorescence imaging of HeLa cells and zebrafish., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

Achieving selective detection of target analytes in aqueous media continues to be an arduous proposition. Herein, we report the conceptualization and synthesis of a novel tailor-fit molecular probe R based on 1,8-naphthalimide which acts as a trifunctional molecular sensor for CN - , Fe 3+ and H 2 S. R shows colorimetric and fluorometric "on-off" relay recognition for CN - (red colour and orange emission) and Fe 3+ (no colour and no emission) in 5% H 2 O + DMSO medium which is experimentally ascertained to be a tandem deprotonation-protonation process and is supported by 1 H-NMR titration. Among all RSS (Reactive Sulphur Species), R shows selectivity for H 2 S through red colouration. Other coexistent anions, cations and RSS cause no discernible perturbation to the detection process. The detection of H 2 S is attributed to a chemodosimetric reduction of the nitro to amino group as evidenced by a potentiometric titration assay. The experimental observations are well supported by DFT theoretical calculation. The K a for CN - /Fe 3+ are 1.4 × 10 4 M -1 , 6.07 × 10 4 M -1 respectively and photochemical yield of R + CN - is 0.86. Limit of detections for CN - , Fe 3+ and H 2 S are 17.5 nM, 8.69 μM and 8.1 μM respectively. Receptor R is effective for real time applications, bio-compatible and has been successfully employed for confocal fluorescence imaging of RAW264.7 cell and zebrafish., Competing Interests: Authors have no conflict of interest., (This journal is © The Royal Society of Chemistry.)