A Unique Water-Tuning Dual-Channel Fluorescence-Enhanced Sensor for Aluminum Ions Based on a Hybrid Ligand from a 1,1′-Binaphthyl Scaffold and an Amino Acid

A naphthyl thiourea-based effective chemosensor for fluorescence detection of Ag+ and Zn2

A naphthyl thiourea-based effective chemosensor HNC, (E)-2-(2-hydroxy-3-methoxybenzylidene)-N-(naphthalen-1-yl)hydrazine-1-carbothioamide, was synthesized. HNC showed quick responses toward Ag⁺ and Zn²⁺ through marked fluorescence turn-on in different solvent conditions, respectively. Binding proportions of HNC to Ag⁺ and Zn²⁺ were found to be 2:1 and 1:1, respectively. Detection limits of HNC for Ag⁺ and Zn²⁺ were calculated as 3.82 and 0.21 μM. Binding processes of HNC for Ag⁺ and Zn²⁺ were represented using Job's plot, DFT, ¹ H NMR titration, and ESI-MS.

Distinct solvent-dependent luminescence sensing property of a newly constructed Cu(ii)–organic framework

The distinct solvent-dependent fluorescence sensing behavior of an extremely rare Cu(ii) MOF, showing the fluorescent “turn-off” sensing of Fe³⁺ and HCO₃⁻ in DMF and “turn-on” sensing of Al³⁺ in water.

A dual functional turn-on non-toxic chemosensor for highly selective and sensitive visual detection of Mg2+ and Zn2+: the solvent-controlled recognition effect and bio-imaging application

A new dual functional turn-on chemosensor, 2,6-diformyl-4-methylphenol-di(isoquinolinyl-1-hydrazone) (HL), has been developed, which could highly selectively discriminate Mg²⁺ and Zn²⁺ in different solvent systems. The chemosensor HL exhibits rapid visual turn-on fluorescence enhancing recognition toward Mg²⁺/Zn²⁺, which is not interfered by other cations, especially for respective congeners Ca²⁺/Cd²⁺. The remarkable fluorescence enhancement (71-fold or 11-fold) was observed after adding Mg²⁺ in acetonitrile or Zn²⁺ in DMF-H₂O solvent systems. Additionally such a solvent medium-controlled platform could achieve the quantitative determination of Mg²⁺ and Zn²⁺ quantitation with low detection limits of 2.97 × 10^-8 M and 3.07 × 10^-7 M, respectively. Furthermore, the turn-on fluorescence sensing mechanism is also investigated by ¹H NMR, FT-IR and ESI-MS spectroscopy. Density functional theory (DFT) calculations derive optimized geometries of HL and its complexes. Notably, non-toxic HL also can be successfully applied as a visual probe for the practical determination of Mg²⁺/Zn²⁺ in MCF-7 cells, Zebrafish larvae, syrup and water samples, which might provide extensive application in biology and medicine fields.

A bright red-emitting flavonoid for Al3+ detection in live cells without quenching ICT fluorescence

A bright red-emitting flavonoid derivative was synthesized, which exhibited a large Stokes shift (Δλ > 150 nm) and high fluorescence quantum yields (ϕ_fl = 0.10–0.35).

A simple quinolone Schiff-base containing CHEF based fluorescence 'turn-on' chemosensor for distinguishing Zn2+ and Hg2+ with high sensitivity, selectivity and reversibility

A new simple 'dual' chemosensor MQA ((E)-2-methoxy-N-((quinolin-2-yl)methylene)aniline) for distinguishing Zn²⁺ and Hg²⁺ has been designed, synthesized and characterized. The sensor showed excellent selectivity and sensitivity with a fluorescence enhancement to Zn²⁺/Hg²⁺ over other commonly coexisting cations (such as Na⁺, Mg²⁺, Al³⁺, K⁺, Mn²⁺, Fe²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Ga³⁺, Cd²⁺, In³⁺ and Pb²⁺) in DMSO-H₂O solution (1/99 v/v), which was reversible with the addition of ethylenediaminetetraacetic acid (EDTA). The detection limit for Zn²⁺/Hg²⁺ by MQA both reached the 10^-8 M level. The 1 : 1 ligand-to-metal coordination patterns of the MQA-Zn2+ and MQA-Hg2+ were calculated through a Job's plot and ESI-MS spectra, and were further confirmed by X-ray crystal structures of complexes MQA-Zn2+ and MQA-Hg2+. This chemosensor can recognize similar metal ions by coherently utilizing intramolecular charge transfer (ICT) and different electronic affinities of various metal ions. DFT calculations have revealed that the energy gap between the HOMO and LUMO of MQA has decreased upon coordination with Zn(ii)/Hg(ii).

A fluorescein-based chemosensor for relay fluorescence recognition of Cu(ii) ions and biothiols in water and its applications to a molecular logic gate and living cell imaging

Relay recognition of copper(ii) ions and biothiolsviaa fluorescence “on–off–on” cascade has been realized in 100% aqueous solution when excited by the visible light.

Substituent-tuned structure and luminescence sensitizing towards Al3+ based on phenoxy bridged dinuclear EuIII complexes

We present herein a novel luminescent enhanced Eu^III complex-supported chemosensor by fine tuning the substitution group on ligands.

A rhodamine based fluorescent trivalent sensor (Fe3+, Al3+, Cr3+) with potential applications for live cell imaging and combinational logic circuits and memory devices

A novel sensor (HL5) recognizes sensitively and selectively trivalent metal ions M³⁺ (M = Al, Fe and Cr) with prominent enhancement in emission intensities with logic gate circuits and memory devices with living cell imaging application.

Single fluorescent chemosensor for multiple targets: sequential detection of Al3+ and pyrophosphate and selective detection of F− in near-perfect aqueous solution

An easily fabricated chemosensor was developed for selective fluorescence detection of three analytes, Al³⁺, pyrophosphate (PPi), and F⁻, in aqueous solution.

A fluorescent probe for relay recognition of homocysteine and Group IIIA ions including Ga(iii)

Relay fluorescence recognition of homocysteine and gallium ions was realized by sequential chemodosimeter and chemosensor approaches for the first time.

Synthesis and cation-binding studies of gold(i) complexes bearing oligoether isocyanide ligands with ester and amide as linkers

Bis(alkynyl)calix[4]arene gold(i) isocyanide complexes with amide linkers show strong binding affinity towards Al³⁺, which turns on the low-energy emission associated with the presence of Au(i)⋯Au(i) interactions.

1,8-Naphthalimide derivative-based turn-off fluorescent probe for the detection of picrate in organic aqueous media

The synthesis of a simple fluorescent naphthalimide-based receptor N-allyl-4-iminodi(N-butylacetamide)-1,8-naphthalimide 3 was carried out as a selective picrate (Pic–) anion probe, and the detecting behavior of this probe was studied by fluorescence spectroscopy. In DMF solution, the interaction of compound 3 with different anions, including Pic–, F–, Cl–, Br–, I–, OH–, Ac–, NO3 –, ClO4 –, SCN–, SO3 2–, SO4 2–, H2PO4 –, and HPO4 2–, revealed significant fluorescence quenching only with the Pic– anion. By adding the picrate anions, green-yellow fluorescence emission quenches, which is easily observed by naked eyes under a 365 nm UV light irradiation. This phenomenon is essential for producing a highly selective and sensitive fluorescent probe for picrate anions. The probe can be applied to the quantification of Pic– with a linear range covering from 4.97 × 10–6 to 6.82 × 10–5 m and a detection limit of 5.8 × 10–7 m. Most importantly, probe 3 has a high selectivity for picrate over competitive anions and picrate-containing analytes, which meet the selective requirements for practical application. Thus, the present results would be inspiring findings in the future design of reaction-based fluorescent turn-off probes for the environmentally relevant picrate probe.

Electrostatic Polyion Micelles with Fluorescence and MRI Dual Functions

We report in this work the formation of fluorescence and MRI bimodal imaging nanoparticles achieved by electrostatic self-assembly. The nanoparticles are micelles formed with Gd(3+) ion, a bisligand that contains aggregation induced emission (AIE) group, and a block copolymer. The coordination between the Gd(3+) ion and the bisligand produces a negatively charged coordination complex, which interacted with the positive-neutral block copolymer to form polyion micelles. The micelles exhibit considerable fluorescence owing to the rotation restriction of the AIE group; meanwhile, the longitudinal relaxation of water was significantly slowed down which provide T1 contrast for magnetic resonance imaging. In vitro fluorescence imaging and in vivo MRI measurements verified this micelle indeed exhibit dual imaging ability. We expect that this orthogonal imaging may provide more accurate diagnosis in practical applications and will pave the way for the development of an advanced technique for diagnosis.

A New Fluorescence Turn-On Probe for Aluminum(III) with High Selectivity and Sensitivity, and its Application to Bioimaging

The development of novel selective probes with high sensitivity for the detection of Al(3+) is widely considered an important research goal due to the importance of such probes in medicine, living systems and the environment. Here, we describe a new fluorescent probe, N'-(4-diethylamino-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (1), for Al(3+). Probe 1 was evaluated in a solution of acetonitrile/water (1:1 v/v). Compared with previously reported probes for Al(3+), probe 1 can be synthesized easily and in high yield. A Job plot confirmed that probe 1 is able to complex Al(3+) in a 1:1 ratio, and the binding constant was determined to be 4.25×10(8) m(-1). Moreover, the detection limit was as low as 6.7×10(-9) m, suggesting that probe 1 has a high sensitivity. Common coexistent metal ions, such as K(+), Co(2+), Ca(2+), Ba(2+), Ni(2+), Pb(2+), Hg(2+), Ce(2+), Zn(2+), Cd(2+), Fe(3+), showed little or no interference in the detection of Al(3+) in solution, demonstrating the high selectivity of the probe. Finally, the ability of probe 1 to act as a fluorescent probe for Al(3+) in living systems was evaluated in Gram-negative bacteria, Escherichia coli, and confocal laser scanning microscopy confirmed its utility. The results of this study suggest that 1 has appropriate properties to be developed for application as a fluorescent probe of Al(3+) for use in biological studies.

A terbium(III)-complex-based on-off fluorescent chemosensor for phosphate anions in aqueous solution and its application in molecular logic gates

A new Tb(III) complex based on a tripodal carboxylate ligand has been synthesized for the selective fluorescent recognition of phosphate anions, including inorganic phosphates and nucleoside phosphates (e.g., ATP), in Tris buffer solution. The resulting L · Tb complex shows the characteristic emission bands centered at about 495 and 550 nm from the Tb(III)-centered (5)D4 excited state to (7)FJ transitions with J = 6 and 5, where the chelating ligand acts only as an "antenna". Upon the addition of phosphate anions to the aqueous solution of Tb(III) complex, significant "on-off" fluorescence changes were observed, which were attributed to the inhibition of the "antenna" effect between the ligand and Tb(III) after the incorporation of phosphate anions. Furthermore, this unique Tb(III) complex has been successfully utilized to detect phosphate anions with filter papers and hydrogels. Notably, the Tb(III) complex also can be used for the construction of molecular logic gates with TRANSFER and INHIBIT logic functions by using the above fluorescence changes.

A Chalcone-Based Highly Selective and Sensitive Chromofluorogenic Probe for Trivalent Metal Cations

A new chalcone-based probe for the chromofluorogenic sensing of trivalent (Al³⁺ , Fe³⁺ , Cr³⁺ , Ga³⁺ , In³⁺ and As³⁺ ) over mono- and divalent cations and anions is reported. In the presence of trivalent metal cations, the probe was able to display a remarkable color change from yellow to colorless that was clearly visible to the naked eye. Also, the initial strong yellow emission was gradually quenched and substituted by a weakly shifted band.

Forced solid-state interactions for the selective "turn-on" fluorescence sensing of aluminum ions in water using a sensory polymer substrate

Selective and sensitive solid sensory substrates for detecting Al(III) in pure water are reported. The material is a flexible polymer film that can be handled and exhibits gel behavior and membrane performance. The film features a chemically anchored salicylaldehyde benzoylhydrazone derivative as an aluminum ion fluorescence sensor. A novel procedure for measuring Al(III) at the ppb level using a single solution drop in 20 min was developed. In this procedure, a drop was allowed to enter the hydrophilic material for 15 min before a 5 min drying period. The process forced the Al(III) to interact with the sensory motifs within the membrane before measuring the fluorescence of the system. The limit of detection of Al(III) was 22 ppm. Furthermore, a water-soluble sensory polymer containing the same sensory motifs was developed with a limit of detection of Al(III) of 1.5 ppb, which was significantly lower than the Environmental Protection Agency recommendations for drinking water.

A polynuclear hetero atom containing molecular organic scaffold to detect Al3+ ion through a fluorescence turn-on response

A simple polynuclear hetero atom (N and O) containing molecular organic scaffold/probe, 3 has been designed and synthesized and explored as a potential chemosensor to detect Al³⁺ (22 nM; ∼0.6 ppb) ion in a HEPES buffer.

Selective detection of Al3+and citric acid with a fluorescent amphiphile

The assembly and disassembly of a fluorescent amphiphile by Al³⁺and citrate, respectively, can be used to sense these analytes by fluorescence spectroscopy.

Fluorescence sensing and intracellular imaging of Al3+ions by using naphthalene based sulfonamide chemosensor: structure, computation and biological studies

Naphthyl appended sulfonamide Schiff base (HL), an antimicrobial nontoxic agent, serves as a fluorogenic sensor to Al³⁺, LOD 33.2 nM and is used for living cell imaging.

A remarkable effect of N,N-diethylamino functionality on the optoelectronic properties of a salicylimine-based probe for Al(3+)

A new live-cell permeable, fluorescent probe comprised of a simple salicylimine-based Schiff base (SA1) has been developed for Al3+ with nano-molar sensitivity in aqueous media. SA1 was synthesized through a simple structural modification of a recently reported receptor SA2 by the incorporation of the N,Ndiethylamino (DEA) group as a fine controllable unit. This modification affects the performance of SA1 remarkably in terms of its sensitivity, water compatibility and efficiency as well as its mechanistic aspect. The presence of the DEA group in SA1 led to its dual channel emission due to the TICT state and at the same time its hydrophobic nature was also responsible for controlling the strong hydration of Al3+ ions in aqueous media which ultimately led to the high sensitivity of SA1 for Al3+. The structure of SA1 was confirmed by single crystal X-ray diffraction and its binding with Al3+ was studied in detail using UVvisible, fluorescence and 1H NMR spectral studies along with mass determination. The effort of getting a single crystal of Al3+–SA1 led to single crystals of Cl−/NO3 − complexes of protonated SA1 which were fully characterized by their XRD studies.