A Novel “Turn On” Glucose-Based Rhodamine B Fluorescent Chemosensor for Mercury Ions Recognition in Aqueous Solution

A novel “turn-on” fluorescent sensor based on glucose and rhodamine B for detection of mercury ions was designed and synthesized. The fluorescent sensor showed an extreme specificity for mercury ions than for other metal ions in aqueous solution. On adding mercury ions to the solution of glucose-based rhodamine B sensor, the absorption and fluorescence signals enhanced remarkably at 567 and 587 nm, respectively. Titration of sensor with mercury ions showed 1:1 stoichiometric reaction. The cyclic voltammetric measurement of an increasing amount of mercury ions in the solution of glucose-based rhodamine B sensor commendably showed the change in the fluorescence characteristics. Furthermore, the successful detection of trace amount of mercury ions in water indicated that glucose-based rhodamine B sensor can be used for the detection of the limited mercury ions in drinking water.     

Development of tBu-phenyl Acetamide Appended Thiacalix[4]arene as “Turn-ON” Fluorescent Probe for Selective Recognition of Hg(II) Ions

Journal of Fluorescence - Herein, a novel N-(4-(tert-butyl)-phenyl)-2-chloroacetamide functionalized thiacalix[4]arene architecture, viz TCAN2PA has been synthesized and the sensing behaviour...     

New Application of a Known Molecule: Rhodamine B 8-hydroxy-2-quinolinecarboxaldehyde Schiff Base as a Colorimetric and Fluorescent “Off-On” Probe for Copper (II)

Rhodamine B 8-hydroxy-2-quinolinecarboxaldehyde Schiff base (1) has been investigated as a colorimetric and fluorescent “off-on” probe for the recognition of Cu²⁺ in aqueous solution. Probe 1 was synthesized by condensation of rhodamine B hydrazide and 8-hydroxy-2-quinolinecarboxaldehyde, which exhibited good selectivity for Cu²⁺ among a range of biologically and environmentally important metal ions. The Cu²⁺ recognition event undergoes a Cu²⁺ promoted hydrolysis of probe 1 to release rhodamine B and the recognition process is barely interfered by other coexisting metal ions.

Phenolic Hydroxyl Group–Carbon Dots as a Fluorescent Probe for the Detection of Hydrogen Peroxide and Glucose in Milk

Journal of Applied Spectroscopy - In order to directly detect the concentration of glucose in milk, carbon dots (CDs) rich in phenolic hydroxyl groups were synthesized in one step as a fluorescent...     

Preparation of Graphene oxide- CuInS2/ZnS Quantum dots Nanocomposite as “Turn-On” Fluorescent Probe for the Detection of Polycyclic Aromatic Hydrocarbons in Aqueous Medium

Journal of Fluorescence - Graphene oxide is well known for its adsorption properties with aromatic compounds. In this study, graphene oxide and eco-friendly ternary CuInS2/ZnS QDs were used to...     

Design and Synthesis of Highly Photostable Yellow–Green Emitting 1,8-Naphthalimides as Fluorescent Sensors for Metal Cations and Protons

Two highly photostable yellow–green emitting 1,8-naphthalimides 5 and 6, containing both N-linked hindered amine moiety and a secondary or tertiary cation receptor, were synthesized for the first time. Novel compounds were configured as “fluorophore–spacer–receptor” systems based on photoinduced electron transfer. Photophysical characteristics of the dyes were investigated in DMF and water/DMF (4:1, v/v) solution. The ability of the new compounds to detect cations was evaluated by the changes in their fluorescence intensity in the presence of metal ions (Cu²⁺, Pb²⁺, Zn²⁺, Ni²⁺, Co²⁺) and protons. The presence of metal ions and protons was found to disallow a photoinduced electron transfer leading to an enhancement in the dye fluorescence intensity. Compound 5, containing secondary amine receptor, displayed a good sensor activity towards metal ions and protons. However the sensor activity of dye 6, containing a tertiary amine receptor and a shorter hydrocarbon spacer, was substantially higher. The results obtained indicate the potential of the novel compounds as highly photostable and efficient “off–on” pH switchers and fluorescent detectors for metal ions with pronounced selectivity towards Cu²⁺ ions.     

Fluorescein Based Three-channel Probe for the Selective and Sensitive Detection of CO32− Ions in an Aqueous Environment and Real Water Samples

Journal of Fluorescence - We have constructed a novel fluorescein-based fluorescent chemosensor, FL-In, functionalised with an indole moiety and capable of sensing by both the optical...     

A New Emissive Chalcone-Based Chemosensor Armed by Coumarin and Naphthol with Fluorescence “Turn-on” Properties for Selective Detection of F<Superscript>−</Superscript> Ions

A new chalcone-based probe containing coumarin and naphthol at both ends has been synthesized via aldol condensation. The uniqueness of the newly derived probe can be ascribed to the presence of naphthol and coumarin units acting as binding site and signaling element, respectively. The fluorogenic behaviors toward various anions were investigated. The probe was characterized by various spectroscopic techniques and the in-depth study led to show excellent selectivity and sensitivity for fluoride ions. The hydrogen bonding thus formed with fluoride anion provides remarkable fluorometric responses. The interactions of the probe with fluoride ions were determined by fluorescence, FT-IR and NMR spectroscopic techniques. The exploratory studies by fluorescent spectral changes augur well for the naked-eye sensing applications.     

A New Fluorescent “Turn-Off” Coumarin-Based Chemosensor: Synthesis,Structure and Cu-Selective Fluorescent Sensing in Water Samples

We report the synthesis and characterization two coumarin-based fluorescence probes, N′-{[7-(diethylamino)-2-oxo-2H-chromen-3-yl]carbonyl}pyridine-3-carbohydrazide (3) and N′-benzoyl-7-(diethylamino)-2-oxo-2H-chromene-3-carbohydrazide (4), proposed as a novel fluorescent chemosensor. The two probes designed showed an instant turn-off fluorescence response to Cu²⁺ over other metal ions in ethanol-water mixture based on intramolecular charge transfer (ICT). It was found that pyridine-analogue coumarin is highly selective and sensitive sensor for Cu²⁺. The 3 sensor coordinates Cu²⁺ in 1:1 stoichiometry with a binding constant, K_a = 5.22 M^?1 and the detection limit was calculated 1.97 × 10^?9 M.     

A Rhodamine-Based “Off-On” Colorimetric and Fluorescent Chemosensor for Cu(II) in Aqueous and Non-aqueous Media

A new rhodamine derivative (RhB-NSal) bearing an electron-withdrawing group –NO₂ at the 5-position of 2-hydroxyphenyl moiety was synthesized and its sensing behaviors for Cu²⁺ in acetonitrile and aqueous acetate-buffer/acetonitrile (2/3, v/v, pH 4.8) media were investigated. In each medium, significant absorption and fluorescence enhancements accompanied by an instant color change from colorless to pink were observed for RhB-NSal upon addition of Cu²⁺. RhB-NSal binds with Cu²⁺ forming a 1:1 stoichiometric complex with an association constant of 6.72 (±0.03) × 10⁴ M^?1 and 4.23 (±0.03) × 10⁴ M^?1, respectively. RhB-NSal displayed high selectivity for Cu²⁺ over possibly competitive metal ions except that Fe³⁺ and Bi³⁺ ion can respectively bring about a little interference in absorption and fluorescence with its sensing for Cu²⁺. In dry acetonitrile, pronounced enhancements in the absorbance and emission of RhB-NSal were induced by Cu²⁺, with a detection limit of 0.49 μM, exhibiting higher sensitivity than that of a known analogue bearing no substituent on its phenol ring, RhB-Sal. In aqueous solution, RhB-NSal displayed likewise a high selectivity but a lower sensitivity for Cu²⁺ than that in acetonitrile, with a detection limit of 14.98 μM, still more sensitive than RhB-Sal in absorption. By virtue of these properties, RhB-NSal could be used as an “Off-On” fluorescent and colorimetric chemosensor for Cu²⁺ in acetonitrile medium, and be developed to be a promising candidate of “Off-On” eye-naked chemosensor for Cu²⁺ in a weakly acidic aqueous medium.     

Unsymmetrically Substituted Nickel Triazatetra-Benzcorrole and Phthalocynanine Complexes: Conjugation to Quantum Dots and Applications as Fluorescent “Turn ON” Sensors

We report on the design and application of fluorescent nanoprobes based on the covalent linking of _L-glutathione-capped CdSe@ZnS quantum dots (QDs) to newly synthesized unsymmetrically substituted nickel mercaptosuccinic acid triazatetra-benzcorrole (3) and phthalocyanine (4) complexes. Fluorescence quenching of the QDs occurred on conjugation to complexes 3 or 4. The nanoprobes were selectively screened in the presence of different cations and Hg²⁺ showed excellent affinity in “turning ON” the fluorescence of the nanoprobes. Experimental results showed that the sensitivity of QDs-4 towards Hg²⁺ was much higher than that of QDs-3 nanoprobe. The mechanism of reaction has been elucidated based on the ability of Hg²⁺ to coordinate with the sulphur atom of the Ni complex ring and apparently “turn ON” the fluorescence of the linked QDs.     

A New Rhodamine-Based “Off-On” Fluorescent Chemosensor for Hg (II) Ion and its Application in Imaging Hg (II) in Living Cells

A novel rhodamine derivative (Rh-C), synthesized by the reaction of rhodamine ethylenediamine and cinnamoyl chloride, was evaluated as a chemoselective Hg(2+) ion sensor. Addition of Hg(2+) to an ethanol aqueous solution of the Rh-C resulted in a color change from colorless to obvious pink color together with distinctive changes in UV-vis absorption spectrum and fluorescence spectrum. However, other common alkali-, alkaline earth-, transition- and rare earth metal ions induced no or minimal spectral changes. The interaction of Hg(2+) and sensor Rh-C was proven to adopt a 1:1 binding stoichiometry and the recognition process is reversible. The chemosensor displayed a linear response to Hg(2+) in the range of 0.4-5?μM with a detection limit of 7.4?×?10(-8)?M. The sensor Rh-C was also successfully applied to the imaging of Hg(2+) in HL-7702 cells.     

New Selective Fluorescent “Turn-On” Sensor for Detection of Hg2+ Based on a 1,8-Naphthalimide Schiff Base Derivative

Journal of Applied Spectroscopy - A new fluorescent “turn-on” sensor for Hg2+, N-allyl-4-(ethylenediamine-5-methylsalicylidene)-1,8-naphthalimide (HL) has been designed by combining a...     

Rhodamine B-based “turn-on” fluorescent and colorimetric chemosensors for highly sensitive and selective detection of mercury (II) ions

Two novel macromolecules based on 2-[3-(2-aminoethylsulfanyl)propylsulfanyl]ethanamine covalently bound to one and two units of rhodamine-B moieties, 1 and 2, were prepared and utilized as fluoroionophores and chromophores for the optical detection of Hg²⁺ ions. The sensors were readily prepared by a conventional two-step synthesis. Especially, sensor 1 exhibits high sensitivity and selective OFF–ON fluorescence enhancement and chromogenic change upon binding to Hg²⁺, which served as a “naked-eye” indicator by a noticeable color change of the solution (from colorless to pink–red color). 1 is shown to discriminate various competing metal ions, particularly Ag⁺ and Cu²⁺, as well as Cd²⁺, Na⁺, Li⁺, K⁺, Ba²⁺, Co²⁺, Ni²⁺, Mg²⁺, Mn²⁺ and Al³⁺, with a detection limit of 10 ppb.     

Two Highly Sensitive and Selective Colorimetric “Off-On” Rhodamine-Based Fluorescent Chemosensor for Hg(II) in Aqueous Media

Two novel rhodamine derivatives were designed and synthesized. They were successfully characterized by HR-MS, ¹H NMR and ¹³C NMR. They were found to exhibit a reversible colorimetric response and exhibit high selectivity and sensitivity for Hg(II) ion over other commonly coexistent metal ions. Their selectivity is excellent, and the detection of Hg(II) at ppb level is possible. The colorimetric and fluorescent response to Hg(II) can be conveniently detected even by the naked eye, which provides a facile method for visual detection of Hg(II).     

A Novel Colorimetric and Fluorescent “Off-On” Chemosensor for Cu2+ Based on a Rhodamine Derivative Bearing Naphthyridine Group

A new rhodamine-based derivative bearing a naphthyridine group (compound 1) was synthesized as a colorimetric and fluorescent “off-on” chemosensor for Cu²⁺ in aqueous solutions. The sensing behaviors of 1 toward various metal ions in neutral aqueous solutions were investigated by absorption and fluorescence spectroscopies. Compound 1 is found to exhibit a significant increase in absorbance at 561 nm and an amplified fluorescence at 590 nm toward Cu²⁺ in a selective, sensitive and rapid manner. The quantification of Cu²⁺ by 1 using an absorption spectroscopy method was satisfactory in the linear working range 0.9–10 μM, with a detection limit of 5.4?×?10^?8?M for Cu²⁺ and good tolerance of other metal ions. Upon addition of Cu²⁺, the spirolactam ring (colorless and nonfluorescent) of 1 was opened to ring-opened amide (red color and fluorescent) and a 1:1 stoichiochemetry for the 1-Cu²⁺ complex was formed with an association constant of 1.57?×?10⁴?M^?1.     

Comments on the paper “Detection of the Absorption Spectra of Water Clusters under Atmospheric Conditions”

A numerical simulation has been performed, indicating that the statement on the detection of water dimer absorption by V.I. Serdyukov et al. in Pis’ma Zh. Eksp. Teor. Fiz. 89, 12 (2009) [JETP Lett. 89, 10 (2009)] had been premature. Most of the revealed induced absorption can be attributed to water monomers.