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• In this paper, we report a 1,8-naphthalimide/ triphenylamine-based fluorescent probe (TPA-NI-NO 2) for the specific detection of 4‑methoxy-thiophenol (MTP) with good selectivity among the thiophenols. • The probe can "turn on" detect MTP with the limit of detection (LOD) of 80 nM and no obvious response to relevant analytes and homologues. • The sensing mechanism was explored by HPLC experiment and the PET process was determined by density functional theory (DFT) calculations. • The Gibbs free energy (DG) analysis for the reaction between the probe and different thiophenols were obtained by the theoretical calculations to study the specificity of the probe. • The probe was successfully applied to monitor the MTP in Hela cells. Thiophenols as a series of industrial products are widely used and high toxicity to the organisms and the environment. The fluorescent probe technique offers important insights into thiophenols convenient sensing. Herein, we report a 1,8-naphthalimide/ triphenylamine-based fluorescent probe (TPA-NI-NO 2) for the specific detection of 4‑methoxy-thiophenol (MTP). The probe can "turn on" specific detect MTP with the limit of detection (LOD) of 80 nM among various relevant analytes and homologues (p -Cl-C 6 H 4 SH, p -NO 2 - C 6 H 4 SH, C 6 H 5 SH and o -CH 3 - C 6 H 5 SH). The sensing mechanism was explored by the HPLC experiment and the PET process was determined by density functional theory (DFT) calculations. In addition, the specificity of the probe was also studied by the Gibbs free energy (ΔG) analysis of the reaction between the probe and different thiophenols. The reaction between probe and MTP gives the minimum of the ΔG value (∼ -9.7280 kcal/mol) and that of other thiophenols-mediated is -2.5283 to -5.8911 kcal/mol, which proves the thermodynamic chemical equilibrium can optimize the design of reaction-based fluorescent probes with excellent specificity. At last, TPA-NI-NO 2 was successfully applied to Hela cells imaging. [Display omitted] [ABSTRACT FROM AUTHOR]

• An AIE active anthracene-based Schiff base probe ' AP' is firstly reported as Cu2+ sensor. • AP has negligible interfering effect on Cu2+ detection with nanomolar LOD. • AP - AP * in AIE and AP − Cu2+ − AP * excimer formation is established from UV/PL, DFT and 1H NMR titration debriefings. • Crystalline and nanostructural features of AIE and sensors are authorized by PXRD, SEM, TEM and DLS studies. • Proposed method is validated by cellular imaging and real water recovery interrogations. An aggregation induced emission (AIE) active anthracene-based Schiff base probe "(2-((anthracen-9-ylmethylene) amino) phenol); AP " was synthesized via one-pot reaction and utilized in "turn-on" detection of Cu2+ ions. Ultraviolet–visible and photoluminescence (UV–vis/PL) interrogations confirm the AIE between 0 and 99 % water fraction (f w) and high selectivity of AP to Cu2+. PL studies establish the linear regression of Cu2+ between 0 and 24 µM with a detection limit (LOD) of 53.2 nM. The Job plot and high-resolution mass (HR-mass) data affirm 2:1 stoichiometry and the association constant (K a) value appraised as 1.88 × 10−4 M−2. Time-resolved photoluminescence (TRPL) studies reveal decay kinetics of AIE, Cu2+ sensors and complex's reversibility. Moreover, 1H NMR titration and density functional theory (DFT) investigations identify the binding mode, π-π stacking in AIE, AP − Cu2+ − AP * excimer formation, band gap variations and involvement of photoinduced electron transfer (PET) and chelation enhanced fluorescence (CHEF) mechanism. Crystallinity and nanostructural variations of AIE and Cu2+ sensors are investigated by using powder-X-ray diffraction (PXRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and dynamic light scattering (DLS). AIE and Cu2+ sensory method are validated by MDA-MB-231 cellular imaging studies. Finally, real water-based titrations show nanomolar LODs and recoveries > 97 % with RSDs < 3.5 %. [ABSTRACT FROM AUTHOR]

• A VN62 fluorescent sensor with ESIPT propertywas designed, synthesized and characterized. • VN62 sensor exhibited rapid and stable detection of Al3+ with a remarkable fluorescence enhancement in aqueous solution. • The sensing mechanism of VN62 sensorto Al3+ wasreasonably speculated based on experimental results and theoretical calculations. • VN62 sensor was capable of recognizing Al3+ by test strips and imaging Al3+in plants and living cells. A new acylhydrazone fluorescent sensor (VN62) with excited intramolecular proton transfer (ESIPT) characteristics has been designed and synthesized through condensation of o -vanillin with 6‑hydroxy-2-naphthoic hydrazide for selective detection of Al3+ in aqueous medium. The structure of the VN62 sensor was characterized by various techniques such as 1H and 13C NMR and mass spectrometry, and also confirmed by single crystal X-ray diffraction. The VN62 sensor showed a remarkable fluorescence enhancement response to Al3+ over a broad pH range in a nearly 100 % aqueous solution without interference by most of tested metal ions and anions. Through fluorescence titration and a Job's plot experiment, the binding stoichiometry of VN62 with Al3+ was found to be 1:1. The limit of detection of VN62 toward Al3+ was determined as 39.6 nM and the binding constant was 2.66 × 104 M−1. Comprehensive analyses by HR-MS, 1H NMR and density functional theory calculations illustrated that the VN62 sensor coordinated with Al3+, forming a stable trigonal bipyramid structure complex, which blocked the ESIPT and photoinduced electron transfer processes and simultaneously promoted an intramolecular charge transfer process, thereby leading to strong cyan fluorescence. Moreover, VN62 -loaded test strips were successfully applied for rapid and visual detection of Al3+. Furthermore, the VN62 sensor was used to visualize Al3+in plants and live cells. The results indicated that the VN62 sensor has great potential for detecting Al3+in biological systems. [Display omitted] [ABSTRACT FROM AUTHOR]

• A simple way to synthesize probes. • A new fluorescent probecan detect the level of ClO− in aqueous solution quickly and sensitively. • A new probe can be used to monitor the level of ClO- in living cells. Hypochlorite (ClO−) plays an important source of chlorine contaminant in the environment which may cause various diseases. Therefore, it is imperative to explore a novel method for instant detection of ClO−. In this research, a new fluorescent probe (JSJ-1) has been designed and synthesized for selective response toward ClO−. The response time is less than 30 s while the detection limit can reach as low as 52.3 nM. Further experiments showed that JSJ-1 retains excellent anti-interference features when a variety of possible interferent anions or cations coexist and therefore displayed successful application in ClO− detection in environmental water samples. In addition, the working principle of the probe JSJ-1with high sensitivity and specificity is based on the oxidative cleavage of olefin units by ClO−. The explanation for the chemical processes is supported by fluorescence spectra, UV-vis spectra, 1H NMR, HRMS, and density functional theory (DFT) calculations. A new fluorescent probe JSJ-1 can detect the level of ClO− in aqueous solution quickly and sensitively. [ABSTRACT FROM AUTHOR]

• The chemosensor H 3 L can selectively detect Zn(II), Al(III) and SO 4 =. • Sensing phenomena deals with turn on –off fluorescence. • The HR-MS, NMR, IR spectroscopic study confirm the 1:1 probe-analyte binding. • DFT study optimizes the three 1: 1 probe-analyte structures. • Cell imaging study assures the biosensing activity of the chemosensor. A Salen type Schiff base H 3 L , generated by the one step condensation of 1, 3 diamino 2-propanol and 3- ethoxy salicylaldehyde, for selective and easy detection of the two different cations Zn(II), Al(III) and one specific anion SO 4 = among several competitive cations and anions in 1:9 methanol water HEPES buffer medium. This probe with moderate luminescence property exhibits elevated fluorescence enhancement with different shifting of spectral position during detection of Al(III) / Zn(II) and fluorescence diminution at the time of SO 4 = detection. One another interesting noticeable fact is that, with the help of F − ion Zn(II) can be detected in presence of Al(III) whereas by using CN− ion Al(III) can be detected in presence of Zn(II). The moderately higher binding constant values, measured from the probe-analytes electronic titration and the results obtained from the fluorescence lifetime study, convince us regarding the formation of Zinc/Aluminum/SO 4 = -probe complexes during sensing by the chemosensor H 3 L. The 1:1 binding mechanisms between H 3 L and Al(III)/Zn(II)/SO 4 = ions are propped up by HR-MS analysis and NMR/FTIR titration. The mononuclear structure of Zn(II)- H 3 L / Al(III)- H 3 L and SO 4 = H 3 L complexes are optimized by implementing Density Functional Theory (DFT) study. The sensing phenomena of two metal ions are further utilized to form a molecular logic gate formulation. Interestingly, this chemosensor can effectively detect and quantify all the aforementioned ions in tap water. Finally, the bio sensing ability of the chemosensor has been inspected by performing the fluorescence live cell imaging study, showing the intercellular Zn(II) sensing efficacy. [Display omitted] [ABSTRACT FROM AUTHOR]

• A water soluble hydrazone sensor 1 ·Cl for the detection of Zn2+ has been developed. • The resulting 1 +Zn2+ system could recognize S2− via an on-off process. • Sensing mechanism of sensor 1 ·Cl toward Zn2+ and S2− was demonstrated by spectroscopic studies and DFT calculations. • 1 ·Cl was successfully applied to imaging mitochondrial Zn2+ and S2−. [Display omitted] A simple water soluble hydrazone sensor (1· Cl) has been developed to selectively chelate with Zn2+ via an O 2 N donor set, leading to specific fluorescence enhancements. The highly emissive 1 -Zn2+ complex can serve as a reversible on-off sensor for S2−. The detection limits of 1· Cl for Zn2+ and S2− are 66.0 and 32.6 nM, respectively. The recognition mechanism was carefully investigated through FL, UV-vis, 1H NMR, ESI-MS, time-resolved fluorescence, and density functional theory (DFT) calculations. Owing to the mitochondria-targeting ability of the terminal quaternary ammonium moiety, 1· Cl was successfully applied to image mitochondrial Zn2+ and S2−. [ABSTRACT FROM AUTHOR]

A 5-formyl-2-hydroxybenzoicacid-based fluorescence probe (L) for Cu2+ ions was designed and synthesized. L in CH 3 CN:H 2 O (1:9, v/v) solution displayed highly selective and sensitive fluorescence 'off-on' response over all the other competitive metal ions including Fe2+, Fe3+, Mn2+, Ba2+, Pb2+, Co2+, Cr3+, Cd2+, Na+, Zn2+, Hg2+, Ag+, Ca2+, Al3+, Mg2+, K+, Ni2+ and Y3+. The fluorescence intensity of L presented good linear relationship to the Cu2+ concentration and with the lower detection limits of 2.19 × 10−7 M for Cu2+ ion. Job's plot, mass spectra, Benesi-Hildebrand plot and DFT calculation confirmed that fluorescence increased was caused by the formation of 1:2 complex between L and copper ion. The recovery tests demonstrated that L could accurately detect the existence of Cu2+ ions in water samples. In addition, L can recognize Cu2+ ion in living cells via the fluorescence confocal images and in water samples via test papers mode. • A 5-formyl-2-hydroxybenzoic acid-based probe (L) was synthesized successfully. • L displayed high selective and sensitive "off-on" fluorescence sensing for Cu2+. • L also can be used as test strips to recognize copper ion. • Fluorescence imaging confirmed L can recognize Cu2+ in live cells. [ABSTRACT FROM AUTHOR]