Reaction‐Based Colorimetric and Ratiometric Fluorescence Sensor for Detection of Cyanide in Aqueous Media

A stilbene‐based compound ( 1 ) has been prepared and was highly selective for the detection of cyanide anion in aqueous media even in the presence of other anions, such as F^?, Cl^?, Br^?, I^?, ClO₄^?, H₂PO₄^?, HSO₄^?, NO₃^?, and CH₃CO₂^?. A noticeable change in the color of the solution, along with a prominent fluorescence enhancement, was observed upon the addition of cyanide. The color change was observed upon the nucleophilic addition of the cyanide anion to the electron‐deficient cyanoacrylate group of 1 . The spectral changes induced by the reaction were analyzed by comparison with two model compounds, such as compound 2 with dimethyl substituents and compound 3 without a cyanoacrylate group. An intramolecular charge‐transfer (ICT) mechanism played a key role in the sensing properties, and the mechanism was supported by DFT/TDDFT calculations.     

Reaction‐Based Ratiometric Chemosensor for Instant Detection of Cyanide in Water with High Selectivity and Sensitivity

A highly selective chemosensor 1 based on an acylhydrazone group as binding site and naphthalene group as the fluorescence signal group were described, which could instantly detect CN^? in water with specific selectivity and high sensitivity. The detection of cyanide was performed via the nucleophilic attack of cyanide anion on the carbonyl group, which could be confirmed by ¹H NMR, ¹³C NMR, ESI‐MS and DFT calculations. The addition of CN^? to sensor 1 induced a remarkable color change from colorless to yellow and generated a blue fluorescence, these sense procedure could not interfered by other coexistent competitive anions (F^?, Cl^?, Br^?, I^?, AcO^?, H₂PO₄^?, HSO₄^?, ClO₄^?, SCN^?, S^2?, NO₃^? and SO₄^2?). The detection limits were 5.0×10^?7 M and 2.0×10^?9 M of CN^? using the visual fluorescent color changes and fluorescence spectra changes respectively, which is far lower than the WHO guideline of 1.9×10^?6 M . Test strips based on sensor 1 were fabricated, which could act as a convenient and efficient CN^? test kit to detect CN^? in pure water for “in‐the‐field” measurement.     

A Multifunctional Bimetallic Molecular Device for Ultrasensitive Detection,Naked‐Eye Recognition,and Elimination of Cyanide Ions

A new bimetallic Fe^II–Cu^II complex was synthesized, characterized, and applied as a selective and sensitive sensor for cyanide detection in water. This complex is the first multifunctional device that can simultaneously detect cyanide ions in real water samples, amplify the colorimetric signal upon detection for naked‐eye recognition at the parts‐per‐million (ppb) level, and convert the toxic cyanide ion into the much safer cyanate ion in situ. The mechanism of the bimetallic complex for high‐selectivity recognition and signaling toward cyanide ions was investigated through a series of binding kinetics of the complex with different analytes, including CN^?, SO₄^2?, HCO₃^?, HPO₄^2?, N₃^?, CH₃COO^?, NCS^?, NO₃^?, and Cl^? ions. In addition, the use of the indicator/catalyst displacement assay (ICDA) is demonstrated in the present system in which one metal center acts as a receptor and inhibitor and is bridged to another metal center that is responsible for signal transduction and catalysis, thus showing a versatile approach to the design of new multifunctional devices.     

A novel and synthetically facile coumarin-thiophene-derived Schiff base for selective fluorescent detection of cyanide anions in aqueous solution: Synthesis,anion interactions,theoretical study and DNA-binding properties

A colorimetric and fluorescent chemosensor (chemosensor 2) for the detection of cyanide anions in aqueous solution has been designed and synthesized in high yield. The sensing mechanism of the chemosensor was verified via UV–vis, fluorimetric, and NMR titrations, and was theoretically explained using DFT and TD-DFT calculations. The chemosensor could optically discriminate the presence of fluoride ions over other anions by a color change from yellow to red with an enhancement of pink fluorescence in DMSO. However, it showed strong green fluorescence when CN^? was added to a mixture of DMSO/water (6:4 v/v). Thus, the chemosensor can be employed in selective detecting of CN^? besides other interference anions (F^?, AcO^? and H₂PO₄^?) in aqueous solution. Moreover, 2 can be used to detect CN^? at a concentration as low as 0.32?μM, which is lower than the WHO guideline (2.7?μM) for cyanide. A low quantity of CN^? (1.08?μM) can be detected and quantified using the prepared chemosensor. Moreover, the UV–vis and fluorescence spectroscopy studies of the interactions between 2 and dublex DNA revealed intercalative binding of calf thymus DNA to the chemosensor.     

Coumarin-based urea-amide scaffold in ratiometric fluorescence sensing of CN−

Coumarin-based urea and urea–amide scaffolds 1–3 have been designed and synthesized for the selective and naked eye detection of cyanide ion. Of the three, compound 3 exhibits ratiometric fluorescence change selectively in the presence of CN^? and validates the rationality in designing anion receptor. Upon interaction with CN^?, the color of the solution of 3 in CH₃CN under UV exposure becomes bright yellow, which is beneficial for its naked eye detection. Addition of CN^? of ～10^?4 M brings nice color change from colourless to yellow in ordinary light. The sensing event is supposed to be due to nucleophilic addition of CN^? to the coumarin unit enabling intramolecular charge transfer (ICT) mechanism.     

A crossed molecular beam study of the chemiluminescent reaction Xe(3P2,0) + BrCN → Xe(1S0) + Br + CN(B2Σ+)

The chemiluminescent interaction of Xe(³P_2,0) and BrCN has been studied under crosscd-beam conditions at collision energies ranging up to 70 kj mol^?1. The CN(B → X) fluorescence spectrum, the excitation function for its production and the fluorescence polarisation - or rather its absence - have been determined. The results can be explained by a two-stage harpooning mechanism involving an inert-gas cyanide (Xe⁺CN^?)¹ intermediate but not by a “sensitisation” mechanism proceeding through electronic energy transfer.     

A Fluorometric Method for Cyanogen (C2N2) with No Cyanide Interference

Abstract

A fluorometric method for the analysis of cyanogen (C₂N₂, ethanedinitrile) without cyanide interference is described the procedure is based on the reaction of C₂N₂ with hexamethylenetetramine (HMTA) to produce a fluorophor. the fluorescence yield is linear over a range of 3–4 orders of magnitude. the method is comparable in detection limits to CN^? measurements done electrochemically; in this case >10^?2?<10^?5 M. Many anions and cations were examined for interference; only transition and heavy metal compounds reduced fluorescence. Certain amines may interfere, although all examined reacted much slower than the HMTA.     

A Turn‐On Fluorescence Chemosensor for Cyanide in Aqueous Media Based on a Nucleophilic Addition Reaction

We synthesized a new cyanide (CN ⁻) chemosensor CX based on a nucleophilic addition reaction prompted by cyanide ion, which could be used for highly selective and sensitive fluorescence turn‐on detection of cyanide in aqueous media. The CX showed selective fluorescence recognition for CN ⁻, the miscellaneous competitive anions (F⁻, Cl⁻, Br⁻, I⁻, AcO ⁻, H₂PO₄⁻, HSO₄⁻, ClO₄⁻, S^{2 −}, PO₄³⁻, CO₃²⁻ and SCN ⁻) did not lead to any significant interference. The detection limit of the sensor towards CN ⁻ is 1.15 × 10⁻⁷ mol•L⁻¹. The sensor has been successfully applied to estimate the cyanide ion in seeds of cherries. Test strips based on CX were fabricated, which could be used as a convenient and efficient CN ⁻ test kit to detect CN ⁻ in aqueous solution for “in‐the‐field” measurement.     

Aroyleneimidazophenazine: A Sensitive Probe for Detecting CN− Anion and its Solvatochromism Effect

A novel electron‐deficient heteroacene 15H‐pyrazino[2″,3″:3′,4′]pyrrolo[1′,2′:1,2]imidazo[4,5‐b]phenazin‐15‐one ( 1 ) has been successfully synthesized and characterized. Compound 1 can selectively recognize CN^? and F^? over other 10 anions including BF₄^?, PF₆^?, Cl^?, SO₄^2?, NO₃^?, I^?, H₂PO₄^?, ClO₄^?, Ac^?, and Br^? in CHCl₃/DMF mixed solvents with dual responses, including absorption signals and fluorescent “turn‐off” effects. CN^? and F^? can be distinguished by the completely quenched fluorescence (for CN^?) and partially reduced fluorescence (for F^?). Especially, compound 1 exhibits higher sensitivity to CN^? than F^? with the response concentration as low as 5.0 × 10^?6 mol/L. Moreover, compound 1 shows very interesting solvatochromism effect, and the CHCl₃ solution of compound 1 is sensitive to triethylamine, and its emission could change from green to red upon the addition of triethylamine, which is attributed to the n–π intermolecular charge‐transfer interaction.     

A highly selective chemosensor derived from benzamide hydrazones for the detection of cyanide ion in organic and organic-aqueous media: design,synthesis, sensing and computational studies

ABSTRACT

A new, highly sensitive and selective chemosensing method has been developed for the detection of cyanide ion using benzamide hydrazone receptors (R1-R4). The sensing ability of these compounds towards CN^? in the presence of Br ^?, HSO₄ ^?, Cl^?, OH^?, I^?, F^?, AcO^?, NO₂ ^? and NO₃ ^? in DMF and DMF-Aqueous mixture (DMF:H₂O, 9:1 v/v) was investigated. The binding characteristics of the probe with cyanide ions carried out by ¹ H NMR titrations indicated the deprotonation of N-H group through H-bond interactions between benzamide hydrazones and cyanide ions; it has been theoretically supported by DFT. The binding constant (Ka) and stoichiometry of the host–guest complex formed was calculated by the Benesi–Hildebrand (B–H) plot, and strong interaction of the probe with CN^- ions forming a 1:2 binding stoichiometry has been noted in this study. In a DMF and aqueous medium for CN^? ion, the lower limit of detection (LOD in ppm) is compared to the limit of quantification (LOQ in ppm), which is quite better in terms of sensitivity.     

Probing phosphate ion via the europium(III)-modulated fluorescence of gold nanoclusters

Fluorescent gold nanoclusters (Au-NCs) were synthesized by a one-pot method using 11-mercaptoundecanoic acid as a reducing and capping reagent. It is found that the red fluorescence of the Au-NCs is quenched by the introduction of Eu(III) at pH 7.0, but that fluorescence is restored on addition of phosphate. The Au-NCs were investigated by transmission electron microscopy and fluorescence photographs. The effect of pH on fluorescence was studied in the range from pH 6 to 10 and is found to be strong. Based on these findings, we have developed an assay for phosphate. Ions such as citrate, Fe(CN)₆ ^3?, SO₄ ^2?, S₂O₈ ^2?, Cl^?, HS^?, Br^?, AcO^?, NO₂ ^?, SCN^?, ClO₄ ^?, HCO₃ ^?, NO₃ ^?, Cd²⁺, Ba²⁺, Zn²⁺, Mg²⁺, and glutamate do not interfere, but ascorbate and Fe³⁺ can quench Au-NCs fluorescence. The fluorescent nanocluster probe responds to phosphate in the range from 0.18 to 250 μM, and the detection limit is 180 nM. The probe also responds to pyrophosphate and ATP. Figure

Off/on fluorescence sensor for phosphate based on Eu³⁺-modulated Au NCs thanks to the competition of oxygen-donor atoms from phosphate with those from the carboxylate groups was developed     

Vibrational energy transfer in CH3I

Previous works have reported vibration—vibration and vibration—translation transfer rates in the methyl halides. Using the technique of laser induced infrared fluorescence we have studied energy transfer in the concluding member of this series, CH₃I. Following excitation by resonant lines of a Q-switch CO₂ laser, infrared fluorescence has been observed from the v₂, v₅ as well as the 2v₅, v₁, v₄ vibrational energy levels of CH₃I. All the observed states exhibit a single exponential decay rate of 23 ± 2 ms^?1 torr^?1. Measurements have also been made on deactivation of the various modes by rare gases. The risetime of the v₂, v₅ levels was found to be approximately 101 ± 20 ms^?1 torr^?1, while that of the 2v₅, v₁, v₄ levels was approximately 225 ± 45 ms^?1 torr^?1. Fluorescence was not detected from the v₃ level. These results are discussed in terms of SSH type theoretical calculations, and comparison is made with the results obtained for other members of the methyl halide series, namely CH₃F, CH₃Cl and CH₃Br.     

The Hofmeister Anion Effect on Ionophore‐based Ion‐selective Nanospheres Containing Solvatochromic Dyes

Recently reported ionophore‐based ion‐selective nanospheres contained pH‐independent and positively charged solvatochromic dyes. Here, we evaluate systematically the effect of anions to the fluorescence response of the nanospheres. The anion interference was found significant for anion concentrations above 10 mM. The sensor responses in the presence of various anion background was studied. While target ion (K⁺) causes the fluorescence of the nanospheres to decrease, increasing anion background also leads to lower fluorescence intensity. Lipophilic anions such as ClO₄^?, SCN^?, and I^? exhibited much more interference than hydrophilic anions (e. g., NO₃^?, Cl^?, F^?, SO₄^2?). The trend of the anion interference followed the Hofmeister series. A theoretical model was also demonstrated based on anion adsorption on the surface of the nanospheres.     

A Fluorescent Chemosensor for Dihydrogen Phosphate Ion Based on 2‐[2‐Hydroxy‐4‐(diethylamino) phenyl]‐1H‐imidazo[4,5‐b]phenazine‐Fe3+ Ensemble

A long wavelength emission fluorescent (612 nm) chemosensor with high selectivity for H₂PO₄^? ions was designed and synthesized according to the excited state intramolecular proton transfer (ESIPT). The sensor can exist in two tautomeric forms ('keto' and 'enol') in the presence of Fe³⁺ ion, Fe³⁺ may bind with the 'keto' form of the sensor. Furthermore, the in situ generated GY‐Fe³⁺ ensemble could recover the quenched fluorescence upon the addition of H₂PO₄^? anion resulting in an off‐on‐type sensing with a detection limit of micromolar range in the same medium, and other anions, including F^?, Cl^?, Br^?, I^?, AcO^?, HSO₄^?, ClO₄^? and CN^? had nearly no influence on the probing behavior. The test strips based on 2‐[2‐hydroxy‐4‐(diethylamino) phenyl]‐1H‐imidazo[4,5‐b]phenazine and Fe³⁺ metal complex ( GY‐Fe³⁺ ) were fabricated, which could act as convenient and efficient H₂PO₄^? test kits.     

Intermolecular interaction between squarylium cyanine and porphyrin

In this paper, the interaction between squarylium cyanine and porphyrin in chloroform is investigated by absorption and fluorescence spectroscopy. Emphasis has been put on the mechanism of intermolecular energy transfer. The overlap integral J between the absorption spectrum of squarylium cyanine and the fluorescence spectrum of porphyrin was calculated, which reveals that the singlet-singlet energy transfer may occur from porphyrin to squarylium cyanine in solution. In comparison of the observed rate constant [kqII=6.1 ×1013 (mol/L)-1·s-1] for fluorescence quenching of porphyrin by squarylium cyanine with the diffusion rate constant in chloroform [kdif=1.1×1010 (mol/L)-1·s-1] and the rate of energy transfer [ket≤6.7×104 (mol/L)-1·s-1 in the experimentally dilute solutions] estimated from Forster formula, the possibility of energy transfer by electron exchange or/and coulombic mechanism could be excluded. So it has been definitely convinced that the intermolecuiar energy transfer between them is     

Particle size,morphology, and properties of transition metal ferrospinels of the MFe<Subscript>2</Subscript>O<Subscript>4</Subscript> (M = Co,Ni, Zn) type,produced by glycine-nitrate combustion

Ferrites-spinels of the MFe₂O₄ type (M = Co, Ni, Zn), produced by glycine-nitrate combustion were studied. A physicochemical study of ferrite samples was performed by X-ray fluorescence analysis, scanning electron microscopy, X-ray phase analysis, and X-ray spectroscopy. The average size of the coherent scanning region was found to be (nm): 28 ± 2 for CoFe₂O₄, 32 ± 2 for NiFe₂O₄, and 26 ± 2 for ZnFe₂O₄. Magnetic characteristics were determined by the NMR method. The specific residual magnetization, specific saturation magnetization, and coercive force were, respectively, 14.1 A m² kg^?1, 20.1 A m² kg^?1, 31800 A m^?1 for CoFe₂O₄; 4.4 A m² kg^?1, 23.1 A m² kg^?1, 6550 A m^?1 for NiFe₂O₄; and 5.1 A m² kg^?1, 18.3 A m² kg^?1, 3200 A m^?1 for ZnFe₂O₄. Their magnetic properties show that the resulting ferrospinel powders can be used in the following fields of technology: CoFe₂O₄ in those areas where heat transfer is necessary (hyperthermia) and in development of data storage media; NiFe₂O₄ and ZnFe₂O₄ in those areas where low heat exchange is necessary, ZnFe₂O₄ for fast remagnetization and NiFe₂O₄ as a core or shell for transportation of other substances. The ferrospinel samples compare well in magnetic properties with their foreign commercial analogs, which makes these compounds commercially viable.     

Visible Light Excitable SCN− Selective Fluorescence Probe Derived from Thiophene

An efficient fluorescence probe, 4‐methyl‐2,6‐bis((thiophen‐2‐ylmethylimino)methyl)phenol (DFPTMA) and its SCN^? adduct has been synthesized and characterized by different spectroscopic techniques like ¹H NMR,¹³C NMR, QTOF‐MS ES⁺, UV‐Vis and FTIR spectroscopy. Single crystal X‐ray structure of DFPTMA is reported. In presence of SCN^?, DFPTMA exhibits significant fluorescence enhancement (λ_Ex, 455 nm, λ_Em, 504 nm) in aqueous methanol (water‐methanol, 1:4, V/V, 0.1 mol/L HEPES buffer, pH 7.4). Common bio‐relevant anions viz. CH₃COO^?, NO₂^?, NO₃^?, Cl^?, Br^?, I^?, SO₄^2?, HSO₄^?, N₃^?, HAsO₄^2?, Cr₂O₇^2?, H₂PO₄^?, ClO₄^?, NCO^?, CN^?, CO₃^2?, F^?, PO₄^3?, S^2?, HS^? do not interfere in the recognition of SCN^?. Lowest detection limit for SCN^? is 0.88 µmol/L with response time <5 min. The SCN^? assisted enhancement in emission intensity may be attributed to the formation of H‐bond which enhances the rigidity of the molecular assembly.     

Through bond mechanism versus exciplex formation in the photochemistry of fullerene / ferrocene donor-bridge-acceptor dyads

A systematic fluorescence and flash photolytic investigation of a series of covalently linked fullerene / ferrocene based donor-bridge-acceptor dyads is reported as a function of the nature of the bridge between the donor site and acceptor site. The fluorescence of the investigated dyads 2 (Φ_rel = 0.17 × 10^?4, 3 (Φ_rel = 0.78 × 10^?4), 4 (Φ_rel = 1.5 × 10^?4), 5 (Φ_rel = 0.7 × 10^?4), and 6 (Φ_rel = 2.9 × 10^?4) were substantially quenched, relative to N-methyl fulleropyrrolidine (1) (Φ_rel = 6.0 × 10^?4). Photolysis of N-methyl fulleropyrrolidine (1) in toluene revealed formation of the excited singlet state which was followed by a rapid intersystem crossing to the excited triplet state. On the other hand, the fate of the excited singlet state of 2, 3, 4, 5, and 6 was found to be governed by rapid intramolecular quenching, with rate constants of 28×10⁹ s^?1, 6.9×10⁹ s^?1, and 3.4×10⁹ s^?1, 14×10⁹ s^?1, 2.3×10⁹ s^?1 respectively. The electron transfer process and the charge separation were confirmed by monitoring the characteristic π-radical anion bands at λ_max = 400 and 1055 nm in degassed benzonitrile with τ_1/2 = 1.8 μs (3) and 2.5 μs (4).     

A Benzodithiophene‐Based Fluorescence Probe for Rapid Detection of Fluoride Ion

A novel and simple fluorescence probe was synthesized from benzo[1,2‐b:4,5‐b′]dithiophene (BDT) and trimethylsilylethyne via Sonogashira reaction, and showed highly selective and sensitive fluorescence decreasing response towards F^?. The probe molecule turned to a weakly fluorescent terminal alkyne moiety because its trimethylsilyl (TMS) group was cleaved by fluoride, which was proved by ¹H NMR titration. Whereas no distinct fluorescent changes were observed with the addition of other anions, such as Cl^?, Br^?, I^?, AcO^? and H₂PO₄^?. Upon the addition of F^?, the maximum fluorescence emission wavelength shifted from 460 nm to 450 nm with a decrease of fluorescence intensity by 40% within 20 s. Moreover, the detection limit towards F^? was calculated to be as low as 73.5 nmol/L.     

Epoxy-based oligomeric probe bearing naphthalene units for selective turn-OFF fluorescent sensing of fluoride anion

A simple epoxy-based oligomer 1 bearing naphthalene unit at the chain-ends is reported to be highly selective ON–OFF type fluorescent probe for fluoride anion. The titled oligomer displayed fluorescence quenching upon addition of F^?, resulting in selective detection of fluoride anion over other anions, such as AcO^?, Cl^?, Br^?, I^?, HSO₄^?, NO₃^? and H₂PO₄^? in CH₃CN. Fluorescence experiments suggest the significant influence of the oligomer chain on the sensitivity and selectivity of 1 towards fluoride anion.