Showing papers on "Cyanide published in 2017"

Cyanides in the environment—analysis—problems and challenges

Abstract: Cyanide toxicity and their environmental impact are well known Nevertheless, they are still used in the mining, galvanic and chemical industries As a result of industrial activities, cyanides are released in various forms to all elements of the environment In a natural environment, cyanide exists as cyanogenic glycosides in plants seeds Too much consumption can cause unpleasant side effects However, environmental tobacco smoke (ETS) is the most common source of cyanide Live organisms have the ability to convert cyanide into less toxic compounds excreted with physiological fluids The aim of this paper is to review the current state of knowledge on the behaviour of cyanide in the environment and its impact on the health and human life

Highly fluorescent nitrogen and sulfur co-doped graphene quantum dots for an inner filter effect-based cyanide sensor

Abstract: In this work, nitrogen and sulfur co-doped graphene quantum dots (N,S-GQDs), exhibiting bright blue fluorescence with an excellent quantum yield of 67%, were facilely prepared by one-pot pyrolysis of citric acid (carbon source) and cysteine (N and S sources). Compared to conventional GQDs, the doping of nitrogen/sulfur had significantly altered and uniformed the surface state, and the as-obtained N,S-GQDs displayed an excitation-independent emission behavior, where the fluorescence decay curve was nearly a single exponential. On the basis of the well-known inner filter effect of silver nanoparticles (AgNPs) and cyanide (CN − )-induced etching of AgNPs, the fluorescence of N,S-GQDs could be quenched by AgNPs, and the nonfluorescence state of the as-prepared N,S-GQD-AgNP ensemble would be switched on in the presence of CN − . Meanwhile, the addition of N,S-GQDs has almost ignorable effect on the absorption spectrum of the AgNP solution, however, the subsequent introduction of CN − would significantly decrease the absorbance value owing to the aforementioned etching behavior of CN − . Therefore, a N,S-GQD-based fluorescent and AgNP-related colorimetric dual-mode analytical system for efficacious determination of CN − has been rationally designed and successfully developed for the first time. Furthermore, the detection limits were found to be 0.52 μM and 0.78 μM for fluorescent and colorimetric sensors individually under the optimal experiment conditions. The proposed N,S-GQD-AgNP-based assay can be successfully utilized to the quantitative determination of CN − in spiked tap water samples.

Synthesis of Dicyanovinyl-Substituted 1-(2-Pyridyl)pyrazoles: Design of a Fluorescent Chemosensor for Selective Recognition of Cyanide

Abstract: A fluorescence “turn-off” probe has been designed and successfully applied to detect cyanide (CN–) based on a Michael-type nucleophilic addition reaction and intramolecular charge transfer (ICT) mechanism. For this research, a family of 3-aryl-4-(2,2-dicyanovinyl)-1-(2-pyridinyl)pyrazoles as donor-π-acceptor (D-π-A) systems have been synthesized in 58–66% overall yield, by a three-step synthesis sequence starting from p-substituted acetophenones. The substituted p-methoxyphenyl showed good fluorescence emission and large Stokes shifts in different solvents due to its greater ICT. Likewise, this probe evidenced high selectivity and sensitivity and fast recognition for CN– with a detection limit of 6.8 μM. HRMS analysis, 1H NMR titration experiments, and TD-DFT calculations were performed to confirm the mechanism of detection and fluorescence properties of the chemodosimeter of CN–. Additionally, fluorescent test paper was conveniently used to detect cyanide in aqueous solution.

Exploring molecular complexity with ALMA (EMoCA): Simulations of branched carbon-chain chemistry in Sgr B2(N)

Abstract: Using mm-wavelength data from ALMA, the EMoCA spectral line survey revealed the presence of both the straight-chain and branched forms of propyl cyanide (C$_3$H$_7$CN) toward the Galactic Center star-forming source Sgr B2(N2). This was the first interstellar detection of a branched aliphatic molecule. Through computational methods, we seek to explain the observed $i$:$n$ ratio for propyl cyanide, and to predict the abundances of the four different forms of the homologous nitrile, butyl cyanide (C$_4$H$_9$CN). We also investigate whether other molecules will show a similar degree of branching, by modeling alkanes up to pentane (C$_5$H$_{12}$). We use a coupled three-phase chemical kinetics model to simulate the chemistry of Sgr B2(N2), using an updated chemical network that includes grain-surface/ice-mantle formation routes for branched nitriles and alkanes. We use the EMoCA survey data to search for the straight-chain form of butyl cyanide toward Sgr B2(N2). The observed $i$:$n$ ratio for propyl cyanide is reproduced by the models. Butyl cyanide is predicted to show similar abundances to propyl cyanide, and to exhibit strong branching, with the $sec$ form clearly dominant over all others. The addition of CN to acetylene and ethene is found to be important to the production of vinyl, ethyl, propyl, and butyl cyanide. We report a non-detection of $n$-C$_4$H$_9$CN toward Sgr B2(N2), with an abundance at least 1.7 times lower than that of $n$-C$_3$H$_7$CN. This value is within the range predicted by the chemical models. The models indicate that the degree of branching rises with increasing molecular size. The efficiency of CN addition to unsaturated hydrocarbons boosts the abundances of nitriles in the model, and enhances the ratio of straight-to-branched molecule production. The predicted abundance of $s$-C$_4$H$_9$CN makes it a good candidate for future detection toward Sgr B2(N2).

Sn4+ self-doped hollow cubic SnS as an efficient visible-light photocatalyst for Cr(VI) reduction and detoxification of cyanide

Abstract: Sn4+ self-doped hollow SnS microcubes are controllably designed by a simple template-assisted synthesis followed by reduction under low temperature. The in situ self-doping enhances the interaction between SnS2 and SnS. The 3D hollow structures of the photocatalyst improve the light efficiency significantly due to effective multiple reflections in the cave. Therefore, this novel material shows a remarkable reduction performance for Cr(VI) and detoxification of cyanide under visible light irradiation. The concentration of Cr(VI) decreases sharply with the irradiation time, and 99.6% of Cr(VI) is degraded within 50 min. Meanwhile, the chromium ions can be adsorbed completely. Moreover, the removal rate for cyanide is as high as 97.2%. Combined with the analysis of in situ ATR-FTIR spectroscopy technology, the photocatalytic reduction mechanism of Cr(VI) is confirmed as a proton coupled electron transfer process. The improved photocatalytic activity of the Sn4+ self-doped SnS can be attributed to the enhanced photoabsorption properties and effective separation of photoinduced charge carriers. This general strategy provides a novel route for the synthesis of hollow cubic structural materials, which can be used for photocatalysis, energy storage and wastewater purification applications.

Synthesis of a new fluorescent cyanide chemosensor based on phenothiazine derivative

Abstract: A new phenothiazine derivative containing two dicyano-vinyl groups as the cyanide receptor on both sides was synthesized and fully characterized. The chemosensor showed an intramolecular charge transfer (ICT) absorption band at 494 nm and emission band at 633 nm in acetonitrile solution. Upon titration with different concentrations of cyanide anion both absorption and emission bands decreases in a ratiometric manner. This optical response for cyanide anion is due to the nucleophilic Michael addition of CN− on the α-position of the dicyano-vinyl groups present in the chemosensor in both sides and thus converting these electron acceptors to anionic electron donors and consequently breaking the conjugation, which ultimately affect the ICT and the fluorescence of the chemosensor. The result indicated that the chemosensor showed high sensitivity with a fast response of less than 50 s and selectivity toward cyanide anion with a detection limit as low as 3.2 × 10−9 M, which is the lowest ever reported. The chemosensor reaction mechanism with CN− was studied by 1H NMR and 13C NMR, FTIR and mass spectroscopies.

Organic Cyanide Decorated SERS Active Nanopipettes for Quantitative Detection of Hemeproteins and Fe3+ in Single Cells.

Abstract: It is challenging to develop a robust nanoprobe for real-time operational and accurate detection of heavy metals in single cells. Fe-CN coordination chemistry has been well studied to determine the structural characteristics of hemeproteins by different techniques. However, the frequently used cyanide ligands are inorganic molecules that release cyanide anion under particular conditions and cause cyanide poisoning. In the present study, organic cyanide (4-mercaptobenzonitrile, MBN) was utilized for the first time in developing a facile nanoprobe based on surface-enhanced Raman scattering (SERS) for quantitative detection of hemeproteins (oxy-Hb) and trivalent iron (Fe3+) ions. The nanoprobe prepared by coating the glass capillary tip (100 nm) with a thin gold film, which enables highly localized study in living cell system. The cyanide stretching vibration in MBN was highly sensitive and selective to Fe3+ and oxy-Hb with excellent binding affinity (Kd 0.4 pM and 0.1 nM, respectively). The high sensitivity...

ALMA detection and astrobiological potential of vinyl cyanide on Titan

Abstract: Recent simulations have indicated that vinyl cyanide is the best candidate molecule for the formation of cell membranes/vesicle structures in Titan's hydrocarbon-rich lakes and seas. Although the existence of vinyl cyanide (C2H3CN) on Titan was previously inferred using Cassini mass spectrometry, a definitive detection has been lacking until now. We report the first spectroscopic detection of vinyl cyanide in Titan's atmosphere, obtained using archival data from the Atacama Large Millimeter/submillimeter Array (ALMA), collected from February to May 2014. We detect the three strongest rotational lines of C2H3CN in the frequency range of 230 to 232 GHz, each with >4σ confidence. Radiative transfer modeling suggests that most of the C2H3CN emission originates at altitudes of ≳200 km, in agreement with recent photochemical models. The vertical column densities implied by our best-fitting models lie in the range of 3.7 × 1013 to 1.4 × 1014 cm-2. The corresponding production rate of vinyl cyanide and its saturation mole fraction imply the availability of sufficient dissolved material to form ~107 cell membranes/cm3 in Titan's sea Ligeia Mare.

Exploring molecular complexity with ALMA (EMoCA): Simulations of branched carbon-chain chemistry in Sgr B2(N)

Abstract: Context. Using millimeter wavelength data from the Atacama Large Millimeter/submillimeter Array (ALMA), the EMoCA spectral line survey recently revealed the presence of both the straight-chain (normal) and branched (iso) forms of propyl cyanide (C3 H7 CN) toward the Galactic Center star-forming source Sgr B2(N2). This was the first interstellar detection of a branched aliphatic molecule.Aims. Through computational methods, we seek to explain the observed i :n ratio for propyl cyanide, and to predict the abundances of the four different forms of the homologous nitrile, butyl cyanide (C4 H9 CN). We also investigate whether other molecules will show a similar degree of branching, by modeling the chemistry of alkanes up to pentane (C5 H12 ).Methods. We use the coupled three-phase chemical kinetics model, MAGICKAL, to simulate the chemistry of the hot-core source Sgr B2(N2), using an updated chemical network that includes grain-surface/ice-mantle formation routes for branched nitriles and alkanes. The network explicitly considers radical species with an unpaired electron on either the primary or secondary carbon in a chain. We also include mechanisms for the addition of the cyanide radical, CN, to hydrocarbons with multiple bonds between carbon atoms, using activation energy barriers from the literature. We use the EMoCA survey data to search for the straight-chain form of butyl cyanide toward Sgr B2(N2).Results. The observed i :n ratio for propyl cyanide is reproduced by the models, with intermediate to fast warm-up timescales providing the most accurate result. Butyl cyanide is predicted to show similar abundances to propyl cyanide, and to exhibit strong branching, with the sec form clearly dominant over all others. Normal and iso-butyl cyanide are expected to have similar abundances to each other, while the tert form is significantly less abundant. The addition of CN to acetylene and ethene is found to be important to the production of vinyl, ethyl, propyl, and butyl cyanide. The alkanes also show significant branching. We report a non-detection of n- C4 H9 CN toward Sgr B2(N2), with an abundance at least 1.7 times lower than that of n- C3 H7 CN. This value is within the range predicted by the chemical models.Conclusions. The models indicate that the degree of branching rises with increasing molecular size. The efficiency of CN addition to unsaturated hydrocarbons boosts the abundances of nitriles in the model, and enhances the ratio of straight-to-branched molecule production. Other types of molecule may be less abundant, but show an even greater degree of branching. The predicted abundance of, in particular, s -C4 H9 CN, which at its peak is comparable to that of propyl cyanide, makes it a good candidate for future detection toward Sgr B2(N2).

Diverse benzothiazole based chemodosimeters for the detection of cyanide in aqueous media and in HeLa cells

Abstract: Benzothiazole derivatives bearing anthracenyl, pyrenyl and N,N,-dimethylaminophenyl as an efficient chemodosimeter for cyanide ions are designed and synthesized. The manifestation of selectivity of probes was via both spectral shifts and intensity changes in the presence of cyanide, allowing for both turn-on/ratiometric and colorimetric sensing. The distinct color changes after addition of cyanide ions makes feasible as colorimetric sensors. These probes showed a very fast response with cyanide ions. Density functional theory calculations were conducted in order to support the observed photophysical properties of the probes in the presence of cyanide ions. Furthermore, the chemodosimeters utility was studied by monitoring changes in intracellular cyanide in HeLa cells.

Remediation of cyanide-contaminated environments through microbes and plants: a review of current knowledge and future perspectives

Abstract: Mining industry has been using cyanide for more than ten decades to recover precious metals such as gold and silver. The presence of cyanide in the environment has long been a matter of concern due...

A new aggregation-induced emission active fluorescent probe for sensitive detection of cyanide

Abstract: A novel AIE active fluorescence chemosensor 1 was synthesized with 2-benzothiazoleacetonitrile and 4-(diphenylamino)-benzaldehyde in 73% yield. 1 exhibited prominent selective and sensitive detection to cyanide with significant turn-off fluorescent response in almost pure aqueous media. Moreover, 1 achieved a low detection limited of 0.22 μm (9.44 ppm) which is lower than the maximum level of cyanide in the drinking water (1.9 μm) that the World Health Organization (WHO) permits. The fluorescent response to CN− was attributed to the nucleophilic addition of CN− to the vinyl group of 1 resulting in breaking of the conjugated, which was supported by Job’s plot and 1H NMR titration. The biological applications of 1 were also evaluated and found that 1 exhibited low cytotoxicity and membrane permeability. Furthermore, 1-based test strips could also detect CN− conveniently.

Bifunctional colorimetric chemosensing of fluoride and cyanide ions by nickel-POCOP pincer receptors.

Abstract: Three Ni(II)-POCOP pincer complexes [NiCl{C6H2-4-OH-2,6-(OPPh2)2}], 1; [NiCl{C6H2-4-OH-2,6-(OPtBu2)2}], 2 and [NiCl{C6H2-4-OH-2,6-(OPiPr2)2}], 3 were studied as bifunctional molecular sensors for inorganic anions and acetate. In CH3CN, fluoride generates a bathochromic shift with a colorimetric change for 1–3 with a simultaneous fluorescence turn on, this optical effect is based on deprotonation of the para-hydroxy group of the POCOP ligand. On the other hand, in a neutral aqueous solution of 80 vol% CH3CN, additions of cyanide produce a distinct change of color by forming very stable complexes with the nickel-based receptors 1–3 with log Ka in the range of 4.38–5.03 M−1 and pronounced selectivity over other common anions such as iodide, phosphate, and acetate. Additionally, bromide shows a modest spectral change and affinity, but lower than those observed for cyanide. On the basis of 1H NMR experiments, UV-vis titrations, ESI-MS experiments, and the crystal structure of the neutral bromo complex of 1, it is proposed that the colorimetric change involves an exchange of chloride by CN− on the Ni(II) atom. The Ni(II)-based sensor 1 allows the fluorescent selective detection of fluoride with a limit of 5.66 μmol L−1 and colorimetric sensing of cyanide in aqueous medium in the micromolar concentration range.

Triphenylethylenyl-based donor–acceptor–donor molecules: studies on structural and optical properties and AIE properties for cyanide detection

Abstract: Six novel molecules with donor–acceptor–donor (D–A–D) configurations were synthesized with a middle acceptor flanked by two electron-rich triphenylthylenyl moieties. The first set of three molecules (TPE-FLN, TPE-AQN and TPE-BZQ) consists of fluorenone, anthraquinone and benzophenone as acceptors, respectively, which then underwent Knoevenagel condensation with malononitrile to give the second set of 1,1-dicyanomethylidene-containing molecules CS1, CS2 and CS3. Compounds CS1, CS2 and CS3 were found to be selective to nucleophilic attack by cyanide ion and hence their potential as optical cyanide sensors was investigated. It was found that the main cyanated products of CS1 and CS3 were aggregation-induced emission (AIE) active, and they were successfully isolated and fully characterized. Finally, paper probes were fabricated from the three compounds, of which the CS1-coated paper probe gave a remarkable turn-on of fluorescence in the presence of cyanide, revealing potential for use as a cyanide sensor.

A reaction based colorimetric chemosensor for the detection of cyanide ion in aqueous solution

Abstract: A conjugated naphthoquinone-benzothiazole (R) system was developed and characterized and its cyanide sensing properties were monitored in 80% aqueous DMF solution. Cyanide ions react with the receptor through a nucleophilic addition reaction, resulting in immediate color change that can be viewed and monitored colorimetrically and fluorimerically. Optical properties of R were not affected by the addition of other common anions in the presence and absence of cyanide ions. A test strip based on R was fabricated and could act as a convenient test kit to detect cyanide ions. Thus, the receptor can be used as an effective probe to detect cyanide ions in aqueous solution.

Colorimetric sensing of cyanide and fluoride ions by diaminomalenonitrile based Schiff bases

Abstract: Two new diaminomalenonitrile (DMN) based Schiff bases have been synthesized and explored as a highly efficient receptor for fluoride and cyanide anions. Detection of anions induced by deprotonation of –NH 2 followed by transfer of proton to the electron deficient nitrogen atom of –CN which induce the strong charge transfer (CT). Anion selectivity was controlled by the fluorophore attached to the DMN, the fluorophore can tune the electron push–pull property. This phenomenon was confirmed by 1 H NMR and DFT calculations.

A BODIPY-based dye with red fluorescence in solid state and used as a fluorescent and colorimetric probe for highly selective detection of cyanide

Abstract: Borondipyrromethene (BODIPY) dyes with strong red solid-state photoluminescence are highly desirable for their applications. In this work, a novel BODIPY dye ( 1 ) containing para -bromophenyl at meso position as a molecular separator and dicyanovinyl group on the 2 position as asymmetrical moiety was prepared. The emission peaks of 1 in THF and powder are 548 nm and 640 nm with emission quantum yield of 55.4% and 4.7%, respectively. Moreover, 1 can be used as a fluorescent and colorimetric probe for the detection of cyanide, which is attributable to the addition of CN − to the electron-deficient dicyanovinyl group of 1 . It shows that the color changes from yellow to purple when CN − is added to 1 in THF/H 2 O (10/1, v/v). The maximum emission intensity at 548 nm is quenched 96%, which constitutes the fluorescence signature for cyanide detection. Furthermore, probe 1 achieves rapid detection of cyanide anion within 1 min. However, other anions do not induce any significant change of absorption/emission spectrum of 1 . Notably, the test strips and silica based – 1 can successfully detect CN − .

Smart Phone Assisted Detection and Quantification of Cyanide in Drinking Water by Paper Based Sensing Platform

Abstract: An organometallic dye, europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA) and gold nanoparticles (Au NPs) impregnated paper based sensor platform have been utilized for development of fluorescence turn-on cyanide assay in aqueous media. The ordinary filter paper with 6 μ m pore size were employed as solid support that facilitates impregnation of EuD4TEA and gold nanoparticles and provides durability. Detection mechanism relying on two processes (i) dissolution of gold nanoparticles causing fluorescence recovery and (ii) ligand exchange of triethyl amine with CN group stimulating cyanide specific fluorescence enhancement. The paper platform exhibit naked eye distinguishable color transition upon CN− addition from 10−2 to 10−12 M. To standardize the methodology a homemade image processing algorithm has been developed that enabling calibration of color change and quantify CN− concentration. The described algorithm is applicable to Android smart phones and facilitate transforming these devices into a quantitative cyanide detector. The overall methodology provides instrument free cyanide detection and therefore rapid control of water quality and safety at off-field conditions.

Turn-on fluorescent sensor for the detection of cyanide based on a novel dicyanovinyl phenylacetylene

Abstract: A novel phenylacetylene derivative containing the dicyanovinyl group (3) was successfully synthesized via Sonogashira coupling and a Knoevenagel reaction. Compound 3 could be used as a highly selective and sensitive turn-on fluorescent sensor for the detection of cyanide ions in aqueous solution. Upon the addition of cyanide ions, compound 3 changed from yellow to colorless which was readily observable by the naked eye. In addition, there was an increase of blue fluorescence emission under black light (365 nm) illumination. Using measurements of fluorescence intensity, the linear dynamic range for the quantitative analysis of cyanide concentration was determined to be 0–80 μM with a detection limit of 0.68 μM which is below the 1.9 μM limit recommended by the World Health Organization (WHO) for drinking water. 1H-NMR titration confirmed that the fluorescence turn-on signal is the result of a nucleophilic addition of the cyanide ion to the β-position of the dicyanovinyl carbon. The addition of the cyanide ion disrupts the π-conjugation between the fluorescent phenylacetylene unit and the strong electron withdrawing dicyanovinyl group, thus inhibiting the non-radiative intramolecular charge transfer (ICT) process. The application of compound 3 for the determination of cyanide in spiked samples of water and tapioca starch showed satisfactory results.

H2O2 Assisted Photoelectrocatalytic Oxidation of Ag-Cyanide Complexes at Metal-free g-C3N4 Photoanode with Simultaneous Ag Recovery

Abstract: A g-C3N4 thin film was synthesized by a liquid-based reaction onto ITO substrate via the calcination treatment. The resultant electrode was used as photoanode for photoelectrocatalytic (PEC) oxidation of Ag cyanide complexes with simultaneous Ag recovery, which was enhanced with the addition of H2O2. Surface variation of the g-C3N4 photoanode and titanium cathode was analyzed using SEM, XRD, and XPS techniques. It was observed that, with the cyanide oxidation, Ag oxides and metal Ag were deposited onto the g-C3N4 photoanode and titanium cathode, respectively. The photoelectrochemical response of the g-C3N4 photoanode was obviously increased after the AgO deposition. ESR and trapping experiments confirmed the existence and roles of •O2– and •OH in the PEC oxidation process. The photogenerated electrons from g-C3N4 could be captured by •O2– and H2O2, generating •OH radicals for oxidizing the Ag cyanide complexes. Meanwhile, the deposition of AgO species onto the g-C3N4 surface increased its electrical condu...