A highly selective colorimetric and fluorescent turn-on chemosensor for Al(3+) based on naphthalimide derivative

A trans-Ferulic acid based fluorescence "turn-on" chemosensor for aluminum (III) ions in live cells and environmental samples

This study introduces a novel fluorescence 'turn-on' chemosensor, FHDA, based on a trans-Ferulic acid Schiff-base derivative. FHDA stands out as a highly selective and sensitive tool for the fluorescent detection of Al3+ with the fluorescence 'turn-on' effect. FHDA exhibits a strong CHEF effect and ICT upon complexation with Al3+ in a 1:2 binding stoichiometry. The significant Stokes shift (Δλ = 108 nm, λex = 422 nm, λem = 530 nm), large binding constant (Ka = 4.2 × 104 M-1), ∼9.5-fold increase in the quantum yield (FHDA, Φ = 0.020; FHDA-Al3+ complex, Φ = 0.189), and a LOD of 134 nM, makes FHDA an excellent chemosensor for detecting Al3+ in solution; tests in live cells and environmental samples also showed excellent responses. FHDA offers substantial improvements over existing methods with its ease of use, limited expense, high specificity, and the ability to provide real-time, in-situ monitoring of Al3+ ions. The utility of FHDA is highlighted through applications in monitoring Al3+ ions in e.g. lung cancer cells (A549) and environmental water samples. We believe that applications of FHDA can potentially lead to a novel diagnostic and therapeutic strategy against diseases linked to aluminum dysregulation.

A 1,8-naphthimide-based Fluorescent Probe for Analyzing DMF/H2O Composition

A novel 1,8-naphthalimide fluorescent probe (BNAS) containing 2-thiopheneethylamine moiety was designed and synthesized for analyzing the composition of N,N-dimethylformamide (DMF)/deionized water (H2O) mixtures. With the increase of DMF content, the fluorescence of the system was enhanced from dark to bright yellow-green. Taking 15% (volume) DMF content as the dividing point, the fluorescence intensity of the system at 535 nm showed two good linear relationships with the DMF content 1-15% and 15-99%, based on which the composition of the DMF/H2O mixtures with a volume ratio of 1/99-99/1 could be quickly and efficiently analyzed with high selectivity and sensitivity. BNAS can be applied in real sample assay and further be loaded onto filter paper to make a portable sensor. The mechanism of BNAS response to DMF/H2O composition was also explored.

Schiff Base Compounds as Fluorescent Probes for the Highly Sensitive and Selective Detection of Al3+ Ions

Two new Schiff base fluorescent probes (L and S) were designed for selectively detecting Al3+ ions in aqueous medium. Structural characterization of the purely synthesized compounds was acquired by IR, 1H NMR and 13C NMR. Moreover, their photochromic and fluorescent behaviors have been investigated systematically by UV–Vis absorption and fluorescence spectra. The two probes have both high selectivity and sensitivity toward Al3+ ions in aqueous medium. The 2:1 stoichiometry between the Al3+ and probes was verified by Job’s plot. Moreover, the limits of detection (LOD) for Al3+ by L and S were 1.98 × 10−8 and 4.79 × 10−8 mol/L, respectively, which was much lower than most previously reported probes. The possible recognition mechanism was that the metal ions would complex with Schiff base probes because of the prevalence of the species optimal for complex formation, inhibiting the structural isomerization of conjugated double bonds (-C=N-), inhibiting the proton transfer process in the excited state of the molecules and resulting in changes of its color and fluorescence behavior. Furthermore, the probes will have potential applications for selectively, detecting Al3+ ions in the environmental system with high accuracy and providing a new strategy for the design and synthesis of multi-functional sensors.

A simple "turn-on" fluorescent sensor for reversible recognition of aluminum ion in living cell

A simple and reliable "turn-on" fluorescent sensor (E)-1-[((2-hydroxyethyl)imino) methyl] naphthalen-2-ol (HNP) has been designed, synthesized, and characterized by ¹H-NMR, ¹³C-NMR, FT-IR, and EI-MS analysis. The binding property of HNP was examined employing UV-Vis and fluorescence spectroscopy. HNP exhibited high selectivity towards Al³⁺ among other cations and anions. The fluorescence titration experiment has established binding stoichiometry of HNP with Al³⁺ is 2:1, which can be further verified by HR-MS. The detection limit of HNP is 2.9 μM, and it can be reversible five-to-seven times to detect Al³⁺ without losing much efficiency which indicates that it can be a reliable probe for Al³⁺. Additionally, HNP was successfully applied for the detection of Al³⁺ in living cells. To achieve the detection of aluminum ion across a simple, reliable, and precise method, we have investigated the reversible detection (which can reversible response to Al³⁺ for five-to-seven times) of Al³⁺ through an extremely simple (requires only one-step reaction) "turn-on" fluorescent probe which enables us to visualize and analyze Al³⁺ with low detection limit (2.9 μM) and high selectivity in living cell without interference from the high abundant small biological molecules.

A Significant Fluorescence Turn-On Probe for the Recognition of Al3+ and Its Application

An easy prepared probe, BHMMP, was designed and synthesized, which displayed a significant fluorescence enhancement (over 38-fold) and obvious color change in the recognition of Al³⁺. The binding ratio of probe BHMMP to Al³⁺ was determined as 1:1, according to Job plot. The binding mechanism was fully clarified by the experiments, such as FT-IR spectrum, ESI-MS analysis, and ¹H NMR titration. A DFT study further confirmed the binding mode of BHMMP to Al³⁺. The limit of detection (LOD) for Al³⁺ was determined as low as 0.70 µM, based on the fluorescence titration of BHMMP. Moreover, the results from real sample experiments, including real water samples, test papers, and cell images, well-demonstrated that BHMMP was capable of sensing Al³⁺ in environmental and biological systems.

A novel bifunctional chemosensor for bioimaging in living cells with highly sensitive colorimetric and fluorescence detection of CN− and Al3+

A novel colorimetric/fluorescent chemosensor (1o) was designed and synthesized for the detection of CN− and Al3+.

New Fluorescent Probes for the Sensitive Determination of Glyphosate in Food and Environmental Samples

In this paper, a dual-functional probe, 2-(benzothiazol)-4-(3-hydroxy-4-methylphenyl) imino phenol (BHMH), was synthesized and characterized for the simultaneous detection of Cu2+ and Fe3+ in dimethyl sulfoxide/4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (DMSO/HEPES) (1:4, v/v, pH = 6.0). The limits of detections (LODs) for Cu2+ and Fe3+ were 9.05 and 48 nM, respectively. Based on the competitive coordination, the complex BHMH-Cu2+/Fe3+ exhibited good sensitivity and selectivity for glyphosate. The LODs of BHMH-Cu2+ and BHMH-Fe3+ for glyphosate were 0.41 and 0.63 μM, respectively. The probe quantitatively detected glyphosate in tap water, Songhua River water, local water and soil, and food samples. The colorimetric on-site glyphosate sensing through the probe BHMH-Cu2+ was also studied based on smartphones. BHMH and BHMH-Cu2+/Fe3+ exhibited outstanding imaging capabilities for Cu2+, Fe3+, and glyphosate in living cells with low cytotoxicity, especially the first time for glyphosate.

A Novel Schiff Base-Modified Dialdehyde Cellulose-Based Fluorescent Probe for Al3+ and Its Application in Environmental Analysis

Cellulose is the most abundant natural polymer with good biodegradability and biocompatibility. In this paper, a novel fluorescent probe DAC-SD-NA for aluminum (Al³⁺ ) detection is successfully synthesized based on dialdehyde cellulose (DAC). DAC-SD-NA exhibited a remarkable "turn-on" fluorescence response to Al³⁺ in a wide pH range, and the fluorescence color of DAC-SD-NA solution turned from colorless to bright blue at the presence of Al³⁺ . The detection limit for Al³⁺ is computed to be 6.06×10^-7 m. The reaction mechanism of DAC-SD-NA towards Al³⁺ is confirmed by Job's plot, X-ray photoelectron spectroscopy, and density functional theory (DFT) calculations. In view of DAC-SD-NA exhibited good sensitivity and selectivity, it is applied to detect Al³⁺ in real water. What's more, DAC-SD-NA-loaded fluorescent hydrogel can serve as a convenient tool for the detection of Al³⁺ .

A dual-response ratiometric fluorescent probe for hypochlorite and hydrazine detection and its imaging in living cells

In this work, a dual-response ratiometric fluorescent probe (E)-3-(5-(2-nitrovinyl)thiophen-2-yl)-9-phenyl-9H-carbazole (NTPC) for high selectivity and sensitivity detection of ClO^- and N₂H₄ was successfully developed. This probe NTPC showed ratiometric fluorescent response to ClO^- and N₂H₄, which induces obvious naked-eye color changes, respectively. In addition, the NTPC for ClO^- and N₂H₄ detection displayed low detection limits of 71.4 nM and 0.6 μM, respectively. And the sensing mechanism of NTPC with ClO^- and N₂H₄ was well confirmed by ¹H NMR and HR-MS spectra. Moreover, this novel probe was applied to monitoring and differentiating ClO^- and N₂H₄ in living cells, and exhibits good biocompatibility and low cytotoxicity.

NADH-Activated Dual-Channel Fluorescent Probes for Multicolor Labeling of Live Cells and Tumor Mimic Spheroids

The 1,4-dihydronicotinamide adenine dinucleotide (NADH) is one of the key coenzymes that participates in various metabolic processes including maintaining the redox balance. Early information on the imbalance of NADH is crucial in the context of diagnosing the pathogenic conditions. Thus, a dual-channel fluorescent probe (MQN) is developed for tracking of NADH/NAD(P)H in live cells. In the presence of NADH, only it showed emission signals at 460 and 550 nm upon excitation at 390 and 450 nm, respectively. The probe could provide accurate information on NADH levels in cancer cells (HeLa) and normal cells (WI-38). We observed that the NADH level in cancer cells (HeLa) is relatively higher than that in normal WI-38 cells. We received similar information on NADH upon calibrating with a commercial NADH kit. Moreover, we evaluated substrate-specific NADH expression in the glycolysis pathway and oxidative phosphorylation process. Also, the dual-channel probe MQN has visualized NADH manipulation in the course of depletion of GSH to maintain cellular redox balance. This dual-channel molecular probe MQN comes out as a new detection tool for NADH levels in live cells and tumor mimic spheroids.

A dual-functional probe for sensing pH change and ratiometric detection of Cu2

A series of benzothiazole-based compounds were synthesized and characterized. Among them, probe Z showed significant dual-functional performance which was capable of sensing pH change and Cu²⁺. Probe Z displayed fluorescent turn-on under alkaline conditions due to deprotonation of the hydroxyl group along with the obviously color change from colorless to mint green. Interestingly, it further achieved in ratiometric detection of Cu²⁺ through absorbance or fluorescence signals in strong alkaline condition. The limit of detection was calculated correspondingly as 0.37 μM and 1.35 μM, respectively. Especially, the combination of the XNOR and INHIBIT logic gates could be used to confirm that one medium was in neutrality or alkalinity condition. Moreover, Z was successfully used in real water samples and test paper for fast identification of Cu²⁺, respectively.

A novel dual-function probe for recognition of Zn2+ and Al3+ and its application in real samples

A dual-function probe NAHH based on naphthalene was synthesized and characterized. Based on the combination effects derived from the inhabitation of photo-induced electron transfer (PET) and CN isomerization, probe NAHH achieved in the recognition of Zn2+ and Al3+ both through obvious fluorescence enhancement and color changes detected by naked eye, respectively. Probe NAHH showed high sensitivity with the limit of detection as low as 3.02 × 10-7 M for Zn2+ and 7.55 × 10-8 M for Al3+, indicated the capability of probe NAHH in trace detection for Zn2+ and Al3+. The binding ratio of NAHH with Zn2+ and Al3+ were all 1:1 determined by Job plot, and the corresponding association constant was calculated as 8.48 × 104 M-1 and 4.45 × 105 M-1, respectively. The mechanism was further confirmed by FT-IR, 1H NMR titration and ESI-MS analysis. Furthermore, probe NAHH was successfully applied in logic gate construction and the detection of Zn2+ and Al3+ in Songhua River and test stripe. Fluorescence imaging experiments confirmed that NAHH could be used to monitor Zn2+ in plant root.

A Benzothiazole-Based Fluorescent Probe for Ratiometric Detection of Al3+ and Its Application in Water Samples and Cell Imaging

An easily prepared benzothiazole-based probe (BHM) was prepared and characterized by general spectra, including ¹H NMR, ¹³C NMR, HRMS, and single-crystal X-ray diffraction. Based on the synergistic mechanism of the inhabitation of intramolecular charge transfer (ICT), the BHM displayed high selectivity and sensitivity for Al³⁺ in DMF/H₂O (v/v, 1/1) through an obvious blue-shift in the fluorescent spectrum and significant color change detected by the naked eye, respectively. The binding ratio of BHM with Al³⁺ was 1:1, as determined by the Job plot, and the binding details were investigated using FT-IR, ¹H NMR titration, and ESI-MS analysis. Furthermore, the BHM was successfully applied in the detection of Al³⁺ in the Songhua River and on a test stripe. Fluorescence imaging experiments confirmed that the BHM could be used to monitor Al³⁺ in human stromal cells (HSC).

A lysosome-targetable fluorescent probe for imaging trivalent cations Fe3+, Al3+ and Cr3+ in living cells

An effective morpholine-type naphthalimide chemsensor, N-p-chlorophenyl-4-(2-aminoethyl)morpholine-1,8-naphthalimide (CMN) has been developed as a lysosome-targeted fluorometric sensor for trivalent metal ions (Fe³⁺, Al³⁺ and Cr³⁺). Upon the addition of Fe³⁺, Al³⁺ or Cr³⁺ ions, the probe CMN showed an evident naked-eye color changes which pale yellow solution of CMN turned deepened and it displayed turn-on fluorescence response in methanol. CMN showed a significant selective and sensitive toward Fe³⁺, Al³⁺ or Cr³⁺ ions, while there was no obvious behavior to other monovalent or divalent metal ions from the UV-vis and fluorescence spectrum. Based on the Job's plot analyses the 1:1 coordination mode of CMN with Fe³⁺, Al³⁺ or Cr³⁺ was proposed. The limit of detection (LOD) observed were 0.65, 0.69 and 0.68 μM for Fe³⁺, Al³⁺ and Cr³⁺ ions, respectively. The N-atom of morpholine directly involved in complex formation, CMN emitted fluorescence through inhibition of photoinduced electron transfer (PET). This probe exhibited excellent imaging ability for Fe³⁺, Al³⁺and Cr³⁺ ions in living cells with low cytotoxicity. Significantly, the cellular confocal microscopic research indicated that the lysosome-targeted group of morpholine moiety was introduced which realized the capability of imaging lysosomal trivalent metal ions in living cells for the first time.

A Naphthalimide-Based Fluorescence "Off-on-Off" Chemosensor for Relay Detection of Al3+ and ClO. Front Chem 2019;7:549. [PMID: 31428604 PMCID: PMC6687763 DOI: 10.3389/fchem.2019.00549]

A novel Al³⁺ chemosensor NPA was designed and synthesized on basis of the mechanism of ICT and CHEF. Upon addition of Al³⁺, the probe NPA displayed a bright green fluorescence under UV radiation and visual color change from yellow to colorless. Spectrum titrations showed that NPA could be recognized as a fluorescent turn-on probe with 10^-8 M detection level. The probe was successfully applied in real water sample and test paper. More important, NPA-Al³⁺ complex were used as a fluorescent turn-off probe for the detection of ClO^- with the detection as low as 2.34 × 10^-8 M. The performance of NPA to Al³⁺ and NPA-Al³⁺ complex to ClO^- demonstrated that NPA could be served as a sensitive probe and exhibit INHIBIT logic gate behavior with Al³⁺ and ClO^- as inputs.

A Schiff-base receptor based chromone derivate: Highly selective fluorescent and colorimetric probe for Al(III)

Upon excitation of the visible light, probes show colorimetric and fluorescent responses to the specific metal ion, which can be easily detected by the naked eye. Owing to the excitation of the visible light at 423 nm, a novel and simple Schiff-base receptor based chromone derivative called 7-methoxychromone-3-carbaldehyde-(indole-3-formyl) hydrazone (MCIH2) had been investigated as a selective and sensitive probe for Al³⁺ with colorimetric and fluorescent responses. Upon addition of Al³⁺ to compound MCIH2 solution, compound MCIH2 could respond to Al³⁺ with a good selective colorimetric signal, which was easily observed from colorless to yellow-green by the naked eye. Furthermore, a remarkable fluorescence emission enhancement with an "OFF-ON" signal by over 700-fold was triggered, but other various metal ions had no such significant effects on the fluorescence emission. In addition, the detection limit of compound MCIH2 for recognizing Al³⁺ was evaluated to be as low as 1 × 10^-7 M level, which was sufficiently low for sensing Al³⁺ widely distributed in various environmental and biological systems.

A Highly Selective Fluorescence "Turn on" and Absorbance-Ratiometric Detection of Al3+ in Totally H2O and its Application in Test Paper

A novel naphthalene based fluorescence probe NBDH was designed and synthesized. Probe NBDH exhibited highly selective and sensitive responses towards Al³⁺ in HEPES-NaOH buffer solution (pH = 7.4). In addition, the detection of NBDH to Al³⁺ could be achieved through dual channels embodied in significant fluorescent turn-on signal and ratiometric absorbance response. The stoichiometry ratio of NBDH-Al³⁺ was 1:1 by fluorescence job' plot and binging mechanism was further varified by the FT-IR, NMR titration and HRMS. Furthermore, NBDH was achieved in real sample detection, and a series of color test paper were developed for visual detecting Al³⁺ ions.

A dual-function probe based on naphthalene for fluorescent turn-on recognition of Cu2+ and colorimetric detection of Fe3+ in neat H2O

A simple naphthalene derivative, 6-hydroxy-2-naphthohydrazide (NAH), was designed and synthesized through two facile steps reactions with the 6-hydroxy-2-naphthoic acid (NCA) as the starting material. In neat H₂O (10% 0.01 M HEPES buffer, v/v, pH = 7.4), probe NAH showed a highly selective and sensitive response towards Fe³⁺ via perceptible color change and displayed "turn-on" dual-emission fluorescence response for Cu²⁺. The binding stoichiometry ratio of NAH/Cu²⁺ and NAH/Fe³⁺ were all confirmed as 1:1 by the method of fluorescence job's plot and UV-Vis job's plot, respectively. Probe NAH can be used over a wide pH range for the determination of Fe³⁺ (2.0-10.0) and Cu²⁺ (6.0-10.0) without interference from other co-existing metal ions. A possible detection mechanism was the hydrolysis of NAH upon the addition of Fe³⁺ or Cu²⁺, thereby leading to the formation of 6-hydroxy-naphthalene-2-carboxylic acid (NCA) which was further confirmed by the various spectroscopic techniques including FT-IR, ¹H NMR titration and HRMS. Moreover, NAH was successfully applied to the detection of Cu²⁺ and Fe³⁺ in tap water, ultrapure water and BSA.

Anion Recognition in Water by Charge-Neutral Halogen and Chalcogen Bonding Foldamer Receptors

A novel strategy for the recognition of anions in water using charge-neutral σ-hole halogen and chalcogen bonding acyclic hosts is demonstrated for the first time. Exploiting the intrinsic hydrophobicity of halogen and chalcogen bond donor atoms integrated into a foldamer structural molecular framework containing hydrophilic functionalities, a series of water-soluble receptors was constructed for an anion recognition investigation. Isothermal titration calorimetry (ITC) binding studies with a range of anions revealed the receptors to display very strong and selective binding of large, weakly hydrated anions such as I^- and ReO₄^-. This is achieved through the formation of 2:1 host-guest stoichiometric complex assemblies, resulting in an encapsulated anion stabilized by cooperative, multidentate, convergent σ-hole donors, as shown by molecular dynamics simulations carried out in water. Importantly, the combination of multiple σ-hole-anion interactions and hydrophobic collapse results in I^- affinities in water that exceed all known σ-hole receptors, including cationic systems (β₂ up to 1.68 × 10¹¹ M^-2). Furthermore, the anion binding affinities and selectivity trends of the first example of an all-chalcogen bonding anion receptor in pure water are compared with halogen bonding and hydrogen bonding receptor analogues. These results further advance and establish halogen and chalcogen bond donor functions as new tools for overcoming the challenging goal of anion recognition in pure water.

A naphthalene-quinoline based chemosensor for fluorescent "turn-on" and absorbance-ratiometric detection of Al3+ and its application in cells imaging

A new naphthalene-quinoline based chemosensor L was prepared and structurally characterized. L exhibited excellent selectivity and sensitivity to Al³⁺ through distinct fluorescence enhancement (335-fold) and ratiometric detection in DMF/H₂O (v/v, 1/9) based on the combined mechanisms of ESIPT and CHEF. The recognizing behavior of L toward Al³⁺ had been investigated in detail through Job's Plot, FT-IR, HNMR, and HRMS analysis. The limit of detection (LOD) for Al³⁺ was as low as and 3.67 × 10^-8 M. L was successfully applied in real sample detection and construction of molecular logic gate. Moreover, L was verified to be of low cytotoxicity and good imaging characteristics for the detection of Al³⁺ in cells HSC.

Al(iii)-responsive "off-on" chemosensor based on rhodamine derivative and its application in cell imaging

In this work, a new rhodamine chemosensor (P) with excellent photochromic properties upon vis irradiation was designed and synthesized. The fabricated chemosensor P could detect Al3+ via the opening of the spirolactam ring of the rhodamine unit with high selectivity and sensitivity. The spirolactam ring opening was confirmed by NMR and infrared spectroscopy. Upon binding with Al3+, the generated 1 : 1 P-Al3+ complex, confirmed by Job's plot titrations and mass spectrometry analysis, could exhibit a remarkable fluorescence enhancement with a limit of detection (LOD) of 0.16 μM. Furthermore, the sensing of P to Al3+ in vivo was also studied quantitatively and qualitatively in detail, and the results showed that the coordination between P with Al3+ was reversible in living cells.

A multifunctional selective “turn-on” fluorescent chemosensor for detection of Group IIIA ions Al3+, Ga3+ and In3+

A versatile chemosensor was developed for highly distinguishable and selective recognition of group IIIA metal ions (Al³⁺, Ga³⁺ and In³⁺).

Straightforward Design of Fluorescent Receptors for Sulfate: Study of Non-Covalent Interactions Contributing to Host-Guest Formation

A straightforward design of receptors for binding and sensing of sulfate in aqueous medium was developed. The design involves the connection of two naphthalimide-based pH probes through a hydrogen-bonding motif. The structure of the receptor-sulfate complex, predicted by DFT calculations, was unambiguously confirmed by NMR measurements. There are three major interactions stabilizing the host-guest complex: electrostatic interactions, hydrogen bonding, and stacking interactions of the dyes. Study of two control receptors containing either one dye or methyl amide groups instead of amides, revealed that electrostatic and hydrogen bonding interactions contribute the most to affinity and selectivity of receptors. The receptors can detect sulfate in a 1:1 THF-buffer mixture in pH window 3.6-4.5 demonstrating up to 7-fold fluorescence enhancement. To the best of our knowledge, the reported PET (photoinduced electron transfer) anion probes possess the largest response for sulfate in aqueous solution yet described.

A Highly Selective Naphthalimide-Based Chemosensor: "Naked-Eye" Colorimetric and Fluorescent Turn-On Recognition of Al3+ and Its Application in Practical Samples, Test Paper and Logic Gate

A novel naphthalimide-based colorimetric and fluorescent turn-on chemosensor for Al³⁺ was synthesized and characterized with spectroscopic techniques. In MeOH solution, BPAM showed high selectivity and sensitivity to Al³⁺ by a 60-fold fluorescence enhancement and blue-shift absorption with visible color changes attributed to the contribution of chelation enhanced fluorescence (CHEF) and inhibition of intramolecular charge transfer (ICT). A 1:1 BPAM-Al³⁺ complex confirmed by job's plot and HRMS with a binding constant of 6.37 × 10⁴ M^- 1, and the detection limit for Al³⁺ was as low as 1.59 × 10^- 7 M. BPAM was successfully applied in real sample detection and assessing the existence of Al³⁺ by a colorimetric method on filter paper. Furthermore, the fluorescent signals of BPAM were designed to construct an INHIBIT molecular logic gate.

Synthesis, fluorescence-sensing and molecular logic of two water-soluble 1,8-naphthalimides

Two novel highly water-soluble fluorescence sensing 1,8-naphthalimides are synthesized and investigated. The novel compounds are designed on the "fluorophore-receptor₁-spacer-receptor₂" model as a molecular fluorescence probe for determination of cations and anions in 100% aqueous media. The novel probes comprising N-imide and N-phenylpiperazine or morpholine substituents are capable to operate simultaneously via ICT and PET signaling mechanism as a function of pH and to recognize selectively Cu²⁺ and Hg²⁺ over the other representative metal ions. Due to the remarkable fluorescence changes in the presence of protons, hydroxyl anions, Hg²⁺ and Cu²⁺, INH and doubly disabled INH logic gates are executed and the systems are able to act as a single output combinatorial logic circuit with four chemical inputs.

A highly selective chromogenic sensor for Mn2+, turn-off fluorometric for Hg2+ ion, and turn-on fluorogenic sensor for F- ion with the practical application

A colorimetric and fluorometric probe (E)-2-((8-hydroxy-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-9-yl)methylene)hydrazinecarbothioamide based on thiosemicarbazide and julolidine moieties has been synthesised in pure crystalline form and characterized by ¹H NMR, UV-vis, elemental analysis and single crystal XRD. The probe functioned as multitarget ion sensor, detect biologically important metal ions Hg²⁺ and Mn²⁺ in dual channel mode. Meanwhile, in mixed solvent media DMF/H₂O [8:2], probe displayed selectivity for Hg²⁺ over other cations by the emission spectrum. Interestingly probe has been explored to recognize F^- anion in DMF through ESIPT mechanism. The 1:1 binding stoichiometry of probe with Hg²⁺ and Mn²⁺ is confirmed by Job's plot through emission titration and UV-vis titration respectively. Probe is selective and sensitive to Hg²⁺ and Mn²⁺ with detection limit as low as 15μM and 0.2μM respectively. The sensing mechanism for selective ions was also scrutinized using ¹H NMR experiments and computational studies.

Crystal structure of 2-(4-(2-butyl-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)piperazin-1-yl)-2-oxoethyldiethylcarbamodithioate, C27H34N4O3S2

C27H34N4O3S2, monoclinic, P21/c (no. 14), a = 17.7267(7) Å, b = 10.5415(5) Å, c = 14.1637(4) Å, β = 91.644(3)°, V = 2645.62(18) Å3, Z = 4, R gt(F) = 0.0620, wR ref(F 2) = 0.2008, T = 293(2) K.

A review of mechanisms for fluorescent ‘‘turn-on’’ probes to detect Al3+ ions

The adverse effect of Al³⁺ ions on human health as well as the environment makes it desirable to develop sensitive and specific techniques for the detection of Al³⁺ ions.