A highly selective pyrene based fluorescent sensor toward Hg2+ detection

Ultrasound-Assisted Synthesis of Chalcone: A Highly Sensitive and Selective Fluorescent Chemosensor for the Detection of Fe3+ in Aqueous Media

The chalcone compound DHPO was synthesized through a chemical reaction between 1-(2-hydroxyphenyl)-ethanone and 3,4-dimethoxy benzaldehyde under ultrasound irradiation. The interaction between the DHPO compound and several metal ions was studied using fluorescence behavior, revealing that the chalcone function as a "turn on and turn off" switch fluorescent sensor, for selectively and sensitively detecting Fe3+ ions. The process of fluorescence quenching and complexation of DHPO with Fe3+ ion was further studied using methods such as Benesi-Hildebrand, Stern-Volmer plot, and job plot.

Terbium Vanadate Nanowires-Based Electrochemical Sensors for Mercury Ions

Terbium vanadate nanowires were synthesized via a facile chemical approach using sodium vanadate and terbium chloride. Morphology, structure, composition, and electrochemical characteristics of the terbium vanadate nanowires were investigated by different techniques. Terbium vanadate nanowires with single crystalline tetragonal TbVO4 phase possess smooth surface and flat tips. The length of the nanowires is longer than 5 μm, and diameter is 40-100 nm. Terbium vanadate nanowires modified electrode was used for trace-level mercury ions (Hg2+) detection. One well-defined stripping peak exists at - 0.34 V at the terbium vanadate nanowires modified electrode in 0.1 mM Hg2+ solution. Buffer solution pH value, deposition time, deposition potential, and standing time are pH = 1, 150 s, - 1.5 V, and 60 s, respectively. Detection limit for Hg2+ detection is 0.18 nM, and linear range is 0.01-100 μM. The proposed terbium vanadate nanowires modified electrode exhibits significant selectivity, stability, and reproducibility toward Hg2+. The usefulness of the developed sensor based on the terbium vanadate nanowires modified electrode was verified by Hg2+ detection in real samples.

Pyrene-Terminated Tin Sulfide Clusters: Optical Properties and Deposition on a Metal Surface

Herein, we present the synthesis of two pyrene-functionalized clusters, [(Rpyr Sn)4 S6 ]⋅2 CH2 Cl2 (4) and [(Rpyr Sn)4 Sn2 S10 ]⋅n CH2 Cl2 (n=4, 5 a; n=2, 5 b; Rpyr =CMe2 CH2 C(Me)N-NC(H)C16 H9 ), both of which form in reactions of the organotin sulfide cluster [(RN Sn)4 S6 ] (C; RN =CMe2 CH2 C(Me)N-NH2 ) with the well-known fluorescent dye 1-pyrenecarboxaldehyde (B). In contrast, reactions using an organotin sulfide cluster with another core structure, [(RN Sn)3 S4 Cl] (A), leads to formation of small molecular fragments, [(Rpyr Cl2 Sn)2 S] (1), (pyren-1-ylmethylene)hydrazine (2), and 1,2-bis(pyren-1-ylmethylene)hydrazine (3). Besides synthesis and structures of the new compounds, we report the influence of the inorganic core on the optical properties of the dye, which was analyzed exemplarily for compound 5 a via absorption and fluorescence spectroscopy. This cluster was also used for exploring the potential of such non-volatile clusters for deposition on a metal surface under vacuum conditions.

Blue luminescent graphene quantum dot conjugated cysteamine functionalized-gold nanoparticles (GQD-AuNPs) for sensing hazardous dye Erythrosine B

Erythrosine B (ErB) is a xanthenes approved dye that widely used in various fields such as foods, drugs and cosmetics. This work intended to analyze the interaction of this dye on synthesized graphene quantum dot conjugated cysteamine functionalized gold nanoparticles. Pyrolysis of citric acid was applied to graphene quantum dots (GQDs) synthesis. These are zero dimensional materials promising considerable applications because of their extraordinary physicochemical properties. In this work, to improve its applications conjugates of GQDs and gold nanoparticles (GQD-AuNPs) are synthesized and characterized with FESEM, TEM, EDX and FTIR techniques. Interaction of ErB with synthesized conjugates was investigated using fluorescence technique and the results demonstrate that ErB can quench fluorescence of GQD-AuNPs conjugates, considerably. At last, we used of this good interaction for construction sensor for detection of ErB in the concentration range of 1.2 nM to 50 nM and the obtained LOD was 0.03 nM (S/N = 3) with correlation coefficient of (99%).

The Fluorescent Quenching Mechanism of N and S Co-Doped Graphene Quantum Dots with Fe3+ and Hg2+ Ions and Their Application as a Novel Fluorescent Sensor

The fluorescence intensity of N, S co-doped graphene quantum dots (N, S-GQDs) can be quenched by Fe3+ and Hg2+. Density functional theory (DFT) simulation and experimental studies indicate that the fluorescence quenching mechanisms for Fe3+ and Hg2+ detection are mainly attributed to the inner filter effect (IFE) and dynamic quenching process, respectively. The electronegativity difference between C and doped atoms (N, S) in favor to introduce negative charge sites on the surface of N, S-GQDs leads to charge redistribution. Those negative charge sites facilitate the adsorption of cations on the N, S-GQDs' surface. Atomic population analysis results show that some charge transfer from Fe3+ and Hg2+ to N, S-GQDs, which relate to the fluorescent quenching of N, S-GQDs. In addition, negative adsorption energy indicates the adsorption of Hg2+ and Fe2+ is energetically favorable, which also contributes to the adsorption of quencher ions. Blue fluorescent N, S-GQDs were synthesized by a facile one-pot hydrothermal treatment. Fluorescent lifetime and UV-vis measurements further validate the fluorescent quenching mechanism is related to the electron transfer dynamic quenching and IFE quenching. The as-synthesized N, S-GQDs were applied as a fluorescent probe for Fe3+ and Hg2+ detection. Results indicate that N, S-GQDs have good sensitivity and selectivity on Fe3+ and Hg2+ with a detection limit as low as 2.88 and 0.27 nM, respectively.

NIR-emitting benzothiazolium cyanines with an enhanced stokes shift for mitochondria imaging in live cells

A series of benzothiazolium-based hemicyanines (3a-3f) have been synthesized. Evaluation of their photophysical properties shows that they exhibit improved photophysical characteristics. In comparison with the available commercial MitoTrackers, the new probes revealed an enhanced Stokes shift (Δλ ∼ 80 nm) and minimized aggregation for increased sensitivity. The synthesized probes are found to exhibit excellent selectivity for mitochondrial staining in an oligodendrocyte cell line. Probes show almost no fluorescence in aqueous environments, while the fluorescence is increased by ∼10-fold in organic solvents, making it possible for mitochondrial imaging without the need for post-staining washing. Since the absorption peaks of probes are close to the laser wavelengths of 561 and 640 nm on a commercial confocal microscope, e.g.3a exhibits λabs ∼ 620 nm and λem ∼ 702 nm, they could be useful probes for mitochondrial tracking in live cells.

AIE active multianalyte fluorescent probe for the detection of Cu2+, Ni2+ and Hg2+ ions

A novel pyrazolyl chromene derivative (Probe 1) displaying aggregation induced emission (AIE) properties that capable of sensing of multiple metal ions has been designed and synthesized. The multi analyte probe exhibits selective sensing for Cu²⁺ and Ni²⁺ ions via fluorescence turn-off mechanism and ratiometric selectivity for Hg²⁺ ions in aqueous media. The extent of binding of the probe with sensitive metal ions has been demonstrated. The experimental results were further investigated by computational means by optimizing the ground state geometries of Probe 1 and its various metal complexes for Probe 1-Ni, Probe 1-Hg and Probe 1-Cu using density functional theory (DFT) at B3LYP/6-31+g(d,p) (LANL2DZ) level. On the basis of binding energies, the stability of metal complexes has been studied. In Probe 1-Ni and Probe 1-Cu complexes, charge transfer has been observed from Probe 1 to metal ions revealing ligand to metal charge transfer (LMCT) while in Probe1-Hg complex LMCT as well as intra-molecular charge tranfer (ICT) within Probe 1.

The fluorescent property of 3-[(2-hydroxy-1-naphthyl) methylideneamino]benzoic acid and its application as fluorescent chemosensor for Hg2+ and Al3+ ions

This manuscript studies the fluorescent property of 3-[(2-hydroxy-1-naphthyl)methylideneamino]benzoic acid (H₂L). Fluorescent spectra show that in different solvents, H₂L displays different fluorescent properties, which can be attributed to the interaction between the solvents and H₂L. Further study indicates that H₂L exhibits a highly selective and sensitive recognition for Hg²⁺ ions in dimethylsulfoxide (DMSO), Al³⁺ ions in methanol and N,N'-dimethylformamide/water (DMF/H₂O, 1/1, v/v). The bonding modes and bonding ratio of H₂L and metal ions in different solvents are explored by Job's plot, ¹H NMR titration, and electrospray ionization mass spectrometry (ESI-MS). The probable mechanisms were discussed.

A Unique Sensitive and Highly Selective Fluorescent Naphthodiaza-Crown Macrocyclic Ligand Chemosensor for Hg2+ in Water

The noticeable enhancement in fluorescence emission of O₂N₂-donor naphthodiaza-crown macrocyclic ligand (L) in the presence of Hg²⁺ was observed in which the fluorescence quantum yield of free ligand L as well as L/Hg²⁺ complex were found to be as 0.29 and 0.49, respectively. The observed ultra-low limit of detection (LOD) for Hg²⁺ by L was determined as low as 1.0 × 10^-11 M in water. A 1:1 stoichiometry was also established for L/Hg²⁺ together with a binding constant K _BH = 66,543 by employing fluorescence spectrophotometry. The competition experiments on L/Hg²⁺ demonstrated highly selective detection of Hg²⁺ in the presence of the library cations. A two path mechanism for detection of metal ion in terms of coordination of metal ion to L and/or the formation of counter ion was proposed by using of ¹H NMR and fluorescence spectroscopy. Graphical Abstract pH dependence mechanism of interaction between Hg²⁺ and macrocyclic ligand L.

Novel fluorene-based supramolecular sensor for selective detection of amoxicillin in water and blood

Synthesis, characterization and molecular recognition properties of fluorene based supramolecular cleft 1 is reported. The cleft molecule 1 was prepared in a single-step with good yield (85% yield), by linking Fluorene with 1-ethyl piperazine. The cleft molecule 1 was carefully characterized using various spectroscopic techniques such as NMR and mass spectrometry. The supramolecular interaction of cleft 1 with amoxicillin, 6APA, aspirin, captopril, cefotaxime, ceftriaxone, cefuroxime, diclofenac, penicillin, and cephradine was evaluated by fluorescent spectroscopy. The molecular recognition studies showed that amoxicillin selectively binds with cleft 1 in the presence of other drugs. The analytical method developed for the supramolecular interaction of molecular cleft 1 and amoxicillin was validated at varying pH, concentration and temperature during recognition process. Job's plots indicated that the stochiometry of the interactions between the cleft 1 and the amoxicillin was 1:1.

Quinazolinone derivative: Model compound for determination of dipole moment, solvatochromism and metal ion sensing

A dihydroquinazolinone derivative 2-(2,4-Dimethoxy-phenyl)-2,3-dihydro-1H-quinazolin-4-one (1) was synthesized and characterized by ¹H NMR, ¹³C NMR and FT-IR and its spectral, photophysical, intramolecular charge transfer characteristics were studied by absorption and emission spectroscopy. The compound exhibits significant changes in their photophysical properties depending on the solvent polarity. The observed bathochromic emission band and difference in Stokes shift on changing the polarity of the solvents clearly demonstrate the highly polar character of the excited state, which is also supported by the enhancement of dipole moment of the molecule upon photoexcitation. Solvatochromic shift methods based on Lippert-Mataga, Bakhshiev-Kawski and Reichardt's correlations were applied to calculate the ground, excited and change in dipole moments. The effect of solute-solvent interactions on compound 1 was studied using multi-parameter solvent polarity scales proposed by Kamlet-Taft and Catalan. The interactions of various metal ions on compound 1 were also studied using steady state fluorescence measurements. The emission profile reveals that it acts as on-off type fluorescent chemosensor for selective and sensitive detection of Hg²⁺ions. Complexation stoichiometry and mechanism of quenching were determined from Benesi-Hildebrand and Stern-Volmer plot.

Pyrene–antipyrine based highly selective and sensitive turn-on fluorescent sensor for Th(iv)

Herein, a turn-on flruorescent sensor for thorium(iv) based on pyrene–antipyrine unit is described.

Solvent effect and fluorescence response of the 7-tert-butylpyrene-dipicolylamine linkage for the selective and sensitive response toward Zn(ii) and Cd(ii) ions

The complexation behaviour of new fluorescent sensors based on 7-tert-butylpyrene towards Zn²⁺and Cd²⁺in different solvent systems has been investigated.

Probing solution behaviour of metallosupramolecular complexes using pyrene fluorescence

A new method for assessing the topology of metallosupramolecular assemblies using pyrene-appended ligands is reported. Two potentially tetradentate ligands containing one (L(1)) and two (L(2)) terminal pyrene moieties were synthesised and their complexes with Cu(+) and Cd(2+) were characterised. Photophysical measurements demonstrate that in [Cu(2)(L(1))(2)](2+), [CdL(1)](2+) and [Cu(2)(L(2))(2)](2+) the emission spectra are dominated by monomeric emission but in the cadmium complex of L(2) (where the pyrene units are in close proximity) a quenching of the luminescence coupled with weak emission at 540 nm is indicative of excimer formation.

A pyrene-based fluorescent sensor for Zn2+ ions: a molecular 'butterfly'

A simple pyrene-based triazole receptor has been synthesised and shown to self-assemble in the presence of ZnCl(2) in an exclusively 2:1 ratio, whereas a mixture of 2:1 and 1:1 ratios are observed for other Zn(2+) salts. The pyrene units are syn in orientation; this is supported by a strong excimer signal observed at 410 nm in the presence of ZnCl(2) in acetonitrile. DFT calculations and 2D NMR support the proposed structure.