Anthraquinone Based Sensors for the Selective Detection of Cyanide Ion with Turn on Fluorescence with Logic Gate & Real Sample Applications.

In recent years, there is an increasing interest in finding better and more efficient ways to detect CN- ions. Most of the anthraquinone-based probes show less fluorescence This paper presents the design and synthesis of a new anthraquinone based imine probe with good colorimetric sensing property and fluorescent turn on behavior toward CN- ion. Herein, we report a receptor with both colorimetric and fluorescent enhancement of cyanide ion in DMSO medium is synthesized. The synthesized receptor shows an immediate color change from orange to pink when cyanide is added; and it can be readily observed visually due to the presence of diverse p-conjugated systems in the receptor. These studies were confirmed by UV-Visible, PL studies, DFT, HRMS and 1H NMR titration. Moreover, this receptor shows 1:1 stoichiometry and micromolar detection limit. Further the receptor was applied to a real sample in finger millet (Eleusine Coracana) to detect the presence of cyanide ion. Moreover, the receptor is applicable toward INHIBITION, IMPLICATION logic gates with two input systems.

Cyanine-based Fluorescent Probe for Cyanide Ion Detection.

Cyanine-based probe-possessing indolium iodide and indole unit were synthesized in two-step with easy available raw material: a potential probe for the cyanide ion detection. The detecting ability of the probe was investigated and confirmed by a visual and instrumental approach. A noticeable color change from orange to colorless obtained only for cyanide ions and other added ions does not impart any changes visually and through UV and Fluorescence technique. To confirm the mechanism of sensing 1H-NMR recorded. From the result, the peak belonging to N-methyl displayed an upfield shift from 4.01 δ ppm to 2.74 δ ppm due to the disappearance of indolium iodide ion and the olefin protons peaks were shifted from 7.19 to 6.17 and 8.70 to 7.20 δ ppm confirms the nucleophilic addition of cyanide ion to the probe. Test kit from filter paper prepared for the real-time monitoring cyanide ion. The prepared strip is effective in detecting cyanide ion with a visual color change.

Determination of Azide Ions in Blood by Pentafluorobenzyl Derivation Followed by GC-MS.

ABSTRACT: Objective To establish a method for determination of the azide ions in blood by gas chromatography-mass spectrometry （GC-MS） following pentafluorobenzyl derivatization. Methods A blood sample of 0.2 mL was placed into a 10 mL glass test tube, and the internal standard sodium cyanide, derivatization reagent pentafluorobenzyl bromide and catalyst tetradecyl benzyl dimethyl ammonium chloride were added in turn. After vortex mixing, the mixture was heated with low-power microwave for 3 min. After centrifugation, the organic phase was taken for GC-MS analysis. Results The azide ions in blood had a good linear relationship in the mass concentration range of 0.5 to 20 µg/mL. The lowest detection limit was 0.25 µg/mL and the relative recovery was 91.36%-94.58%. The method was successfully applied to a case of death from sodium azide poisoning. The mass concentration of azide ions in the blood of the dead was 11.11 µg/mL. Conclusion The method developed in this paper has strong specificity and is easy to operate, which is suitable for the rapid detection of azide ions in blood.

Mechanochemical synthesis of fluorescein-based receptor for CN- ion detection in aqueous solution and cigarette smoke residue.

A facile green method for the mechanochemical synthesis of Schiff base phenylhydrazono-N-methylene fluorescein (PHMF) with 95% yields has been established. The synthesized receptor assists in the naked-eye detection of CN- ions in organic and aqueous media, and F- ions in acetonitrile over a series of anions with a color transfer from colorless to pink. A redshift of 160 nm of PHMF-CN- complex in the absorbance spectrum and a turn-on response in the fluorescence spectrum were observed, respectively, at λmax 345 to 515 and 519 nm. A strong interaction of PHMF with CN- and F- ions forming a 1:3 binding stoichiometry has been noted in this study. In an aqueous medium for CN- ion, the lower limit of detection (LOD) is defined as 9.204 nM, which is quite better in terms of sensitivity. In addition, PHMF's paper-strip sensor for rapid real-time CN- ion sensing was found to be sufficiently sensitive to successfully detect CN- ion in water and a solid state, resulting in a portable device for detecting cyanide ions. In acetonitrile, the receptor's ability to detect CN- ion in cigarette smoke residue was also satisfactorily achieved. Graphical Abstract.

New Fluorescent and Colorimetric Chemosensor for Detection of Cyanide with High Selectivity and Sensitivity in Aqueous Media.

A fluorescent and colorimetric chemosensor for detection of cyanide ion based on a styryl quinoline derivative has been designed and synthesized. The chemosensor (E)-2-(4-mercaptostyryl)quinolin-8-ol L showed high selectivity for detection of cyanide over other anions such as F¯, Cl¯, Br¯, I¯, NO3¯, SCN¯, N3¯, ClO4¯, H2PO4¯, AcO¯, HCO3¯, SO42¯ and HSO4¯in aqueous solution. The chemosensor L displayed an immediate visible and fluorescence changes from nearly colorless to orange and greenish-blue to brick-red upon addition of cyanide ion respectively. It is more likely, these distinct changes can be attributed to hydrogen bonding interaction between phenol group and cyanide anion leading to a 1:1 binding stoichiometry following with deprotonation of phenol group. The detection limit for chemosensor L toward CN¯ was 2.73× 10-8 M. Thus, the chemosensor can be used efficiently and selectively for detection and monitoring of small amounts of cyanide ion in aqueous media.

Turn-off-on chemiluminescence determination of cyanide.

A flow injection chemiluminescence (FI-CL) method was developed for the determination of cyanide (CN(-) ) based on the recovered CL signal by Cu(2+) inhibiting a glutathione (GSH)-capped CdTe quantum dot (QD) and hydrogen peroxide system. In an alkaline medium, strong CL signals were observed from the reaction of CdTe QDs and H2O2 , and addition of Cu(2+) could cause significant CL inhibition of the CdTe QDs-H2O2 system. In the presence of CN(-) , Cu(2+) can be removed from the surface of CdTe QDs via the formation of particularly stable [Cu(CN)n ]((n-1)-) species, and the CL signal of the CdTe QDs-H2O2 system was efficiently recovered. Thus, the CL signals of CdTe QDs-H2O2 system were turned off and turned on by the addition of Cu(2+) and CN(-) , respectively. Further, the results showed that among the tested ions, only CN(-) could recover the CL signal, which suggested that the CdTe QDs-H2O2 -Cu(2+) CL system had highly selectivity for CN(-) . Under optimum conditions, the CL intensity and the concentration of CN(-) show a good linear relationship in the range 0.0-650.0 ng/mL (R(2) = 0.9996). The limit of detection for CN(-) was 6.0 ng/mL (3σ). This method has been applied to detect CN(-) in river water and industrial wastewater with satisfactory results.

Tailored fluorophore design: Enhancing selectivity for cyanide ion sensing in water and food samples, and innovative device development.

A rigid fluorophore unit of Julolidine/coumarin fused with an indolium-conjugated system was built for the immediate and effective recognition of cyanide ions in a 90 % aq. DMSO solution. The probes are capable of displaying better sensitivity/selectivity for the cyanide ion over a wide range of other interfering ions. The probe JI showed an instant colorimetric variation, whereas the modified probe JCI showed both colorimetric and fluorimetric variation with cyanide ion. The observed detection limit values indicated excellent sensitivity of the probe to the cyanide ion. HRMS and 1H NMR studies confirmed that the mechanism of detection of CN- is via the nucleophilic attack on the electron-deficient indolium moiety of the molecule. Moreover, the probes are well proficient in selective recognition of cyanide in various real time applications (test strips, electronic sensor kit, food and water sample analysis).

Selective and Sensitive Fluorescence Turn-On Detection of Cyanide Ions in Water by Post Metallization of a MOF.

Owing to detrimental impact of cyanide ion (CN- ) towards the entire living system as well as its availability in drinking water, it has become very important developing potential sensory materials for the selective and sensitive recognition of CN- ions in water. In the domain of sensory materials, luminescent metal-organic frameworks (LMOFs) have been considered as a promising candidate owing to their unique host-guest interaction, where MOFs can serve as an ideal scaffold for encapsulating relevant guest molecules rendering specific functionality. In this study, a post-synthetically modified MOF (viz., CuCl2 @MOF-867) was applied to recognize cyanide (CN- ) ions in water via "turn-on" response. The bipyridyl functionalities in MOF-867 were used to perform post-synthetic metalation to infiltrate CuCl2 inside porous architecture of the MOF. Moreover, a CuCl2 @MOF-867 based probe demonstrated highly selective and sensitive aqueous phase recognition of CN- ions even in the presence of other interfering anions such as Br- , NO3- , I- , SO42- , OAc- , SCN- , NO2- , etc. The selective binding of CN- ions to the copper-metal center has led to the generation of stable Cu(CN)2 species. This phenomenon has further resulted in a fluorescence turn-on response. The aqueous phase cyanide detection by the rationally modified MOF system exhibited very low limit of detection (0.19 µM), which meets the standardized limit stated by World Health Organization (WHO) that is 1.9 µM.

A novel Near-Infrared fluorescent probe for Zn2+ and CN- double detection based on dicyanoisfluorone derivatives with highly sensitive and selective, and its application in Bioimaging.

We have successfully synthesized NIRF as a near-infrared fluorescence probe for relay recognition of zinc and cyanide ions. The probe possesses well selectivity and anti-interference ability over common ions towards Zn2+ and CN-. The results showed that Zn2+ and the probe formed [NIRF-Zn2+] complex after added Zn2+ into the probe NIRF solution, which emited red fluorescence. The probe can be used for quantitative detection of Zn2+ with a detection limit of 4.61 × 10-8 M. It was determined that the binding stoichiometry between the NIRF and Zn2+ was 1:1 according to the job,s curve. Subsequently, CN- was added to the NIRF-Zn2+ solution, CN- combined with Zn2+ to generate [Zn(CN-)x]1-x due to the stronger binding ability between zinc ion and cyanogen, which lead to the red fluorescence disappeared. The quantitative detection of CN- was realized with a detection limit of 7.9 × 10*7 M. In addition, the probe has excellent specificity and selectivity for Zn2+ and CN-. And the probe can be stable in a wide range of pH. Through biological experiments, we found that it can complete cell imaging in macrophages and imaging of living mice, which has application prospects in Bioimaging. In addition, the probe NIRF has good applicability for Zn2+ and CN- detection in actual samples.

A Turn-On Fluorescent Chemosensor for Cyanide Ion Detection in Real Water Samples.

We have designed and synthesized a novel simple colorimetric fluorescent probe with aggregation-induced emission (AIE) properties. Probe 5-(4-(diphenylamine)phenyl) thiophen-2-formaldehyde W exhibited a turn-on fluorescent response to cyanide ion (CN-), which induces distinct visual color changes. Probe W exhibited a highly selective and sensitive ratiometric fluorescence response for the detection of CN- over a wide pH range (4-11) and in the presence of common interferents. The linear detection of CN- over the concentration range of 4.00-38.00 µM (R 2 = 0.9916, RSD = 0.02) was monitored by UV-Vis absorption spectrometry (UV-Vis) with the limit of detection determined to be 0.48 µM. The linear detection of CN- over the concentration range of 8.00-38.00 µM was examined by fluorescence spectrophotometry (R 2 = 0.99086, RSD = 0.031), and the detection limit was found to be 68.00 nM. The sensing mechanisms were confirmed by 1H NMR spectroscopic titrations, X-ray crystallographic analysis, and HRMS. Importantly, probe W was found to show rapid response, high selectivity, and sensitivity for cyanide anions in real water samples, over the range of 100.17∼100.86% in artificial lake water and 100.54∼101.64% in running water by UV-Vis absorption spectrometry, and over the range of 99.42∼100.71% in artificial lake water and 100.59∼101.17% in running water by fluorescence spectrophotometry. Importantly, this work provides a simple and effective approach which uses an economically cheap and uncomplicated synthetic route for the selective, sensitive, and quantitative detection of CN- ions in systems relevant to the environment and health.

Highly selective, colorimetric probes for cyanide ion based on ß-formylBODIPY dyes by an unprecedented nucleophilic addition reaction.

Two ß-formylBODIPYs with strong daylight excitable fluorescence and highly selective visual and colorimetric responses to cyanide anion (CN-) have been prepared. NMR titration experiments have been performed to study the sensing mechanism for these two dyes. Surprisingly, cyanide anion is nucleophilic addition to the α-position of BODIPY core (the azafulvene framework) in aqueous system instead of the expected classical nucleophilic addition to the formyl moiety of the probes. This nucleophilic addition of cyanide anion to the azafulvene framework causes the interruption of the π-conjugation of the BODIPY system, which brings a significant blue-shift (up to 104 nm) of the absorption maxima. A broadened and decreased absorption as well as ratiometrical fluorescence response (with maxima shifts from 523 to 670 nm) were observed with the titration of cyanide anion to probe 1b.

Bisphenol-based cyanide sensing: Selectivity, reversibility, facile synthesis, bilateral "OFF-ON" fluorescence, C2ν structural and conformational analysis.

A structurally characterized novel dual-pocketed tetra-conjugated bisphenol-based chromophore (fluorescence = 652 nm) was synthesized in gram scale in ~90% yield from its tetraaldehyde. Highly selective, naked-eye detection of CN- (DMSO/H2O) was confirmed by interferent testing. A detection limit of 0.38 µM, within the permissible limit of CN- concentration in drinking water was achieved as mandated by WHO. The "reversibility" study shows potential applicability and reusability of Sen. Moreover, cost-effective and on-site interfaces, application tools such as fabricated cotton swabs, plastic Petri dishes, and filter papers further demonstrated the specific selectivity of Sen for the toxic CN-. In addition, an easily available and handy smartphone-assisted "Color Picker" app was utilized to help estimate the concentration of CN- ion present. A dual phenol deprotonation mechanism is active and supported by 1H NMR spectroscopic data and DFT calculation results.

Rational design of a colorimetric and fluorescence turn-on chemosensor with benzothiazolium moiety for cyanide detection in aqueous solution.

A novel colorimetric and fluorescence turn-on chemosensor TBB with benzothiazolium moiety has been explored, which exhibited the high selectivity for cyanide ion (CN-) in THF-H2O (2:8, v/v) mixture. The aqueous solution of sensor TBB was scarcely emissive. In the presence of CN- ion, the nucleophilic addition of CN- with the benzothiazolium CN bond of TBB produced the new species TBB-CN, consequently resulting in the intense orange-red emission by aggregation-induced emission (AIE) effect. Meanwhile, the color of solution was changed from orange-yellow to light yellow. The sensing mechanism was verified by Mass spectrometry, NMR analysis and DFT calculations.

5'-Hydroxymethyl fluorescein: A colorimetric chemosensor for naked-eye sensing of cyanide ion in a biological fluid.

A two-step synthetic method to prepare a highly sensitive and selective chemosensor 5'-hydroxymethyl fluorescein (5'-HMF) is described herein. This sensor was explored as a colorimetric sensor for naked-eye detection of cyanide ion in the biological fluid as well as in organic and aqueous media. The addition of cyanide ion to 5'-HMF resulted in a rapid change in color in aqueous medium from light green to dark fluorescent green, and in acetonitrile from light pink to purple. A significant bathochromic shift in the absorption spectra enables cyanide ion to be detected by naked eyes in water and acetonitrile without any interference of the competing anions such as, AcO-, F- and SCN- in aqueous solution. Using the 1HNMR titration experiments and Job's plot from absorbance spectroscopy, the interaction of CN- ion with 5'-HMF has been investigated and binding stoichiometry was found to be 1:2 (5'-HMF to CN-). The limit of detection (LOD) of the sensor for CN- was 3.68 µM in water with a linearity (R2 = 0.9923) in the range of 0.50 to 30.0 µM concentration assuming 1:2 (5'-HMF to CN-) binding stoichiometry. In addition, the sensor 5'-HMF sensed the CN- ion in human saliva with the LOD as 7.0 µM in aq. medium.

A simple pyrimidine based colorimetric and fluorescent chemosensor for sequential detection of copper (II) and cyanide ions and its application in real samples.

In this study, a new pyrimidine-based chemosensor (PyrCS) has been developed for sequential detection of copper (II) and cyanide ions. The PyrCS has revealed high sensitivity and selectivity toward copper ion over other metal ions in aqueous media. The PyrCS as an optical probe exhibited a distinct color change and a bathochromic shift in UV spectra in the presence of copper ion in a few seconds due to the formation of stable complex (PyrCS-Cu2+). The results confirmed that the PyrCS has a widely linear detection range of 0.3-30 µM toward Cu2+. The calculated limit of detection for Cu2+ ions was low as 0.116 µM. Moreover, the fluorescent intensity of PyrCS at 507 nm was significantly quenched in the presence of Cu2⁺ and Fe2⁺ ions. Additionally, complex PyrCS-Cu2+ was successfully used to detect cyanide ions via Cu2+ displacement approach. The free PyrCS was recovered after adding the CN‾ ions in a few seconds due to the formation of the stable copper cyanide complex Cu(CN)x. The calculated LOD for CN‾ ions was low as 0.320 µM. The data also clarified that the other competing anions did not create a clear color change in solutions. Since the proposed method could provide a vivid colorimetric response in the presence of detected analytes within the pH range of 3-9, we can claim that the developed chemosensor can be utilized in any physical and biological conditions.

Mechanistic Insight Into the AuCN Catalyzed Annulation Reaction of Salicylaldehyde and Aryl Acetylene: Cyanide Ion Promoted Umpolung Hydroacylation/Intramolecular Oxa-Michael Addition Mechanism.

The detailed mechanism of the AuCN-catalyzed annulation of salicylaldehyde (SA) and phenyl acetylene leading to isoflavanone-type complexes has been investigated via density functional theory (DFT) calculations. Reaction pathways and possible stationary points are obtained with the combined molecular dynamics and coordinate driving (MD/CD) method. Our calculations reveal that the cyanide ion promoted umpolung hydroacylation/intramolecular oxa-Michael addition mechanism is more favorable than the Au(I)/Au(III) redox mechanism proposed previously. In the umpolung mechanism, the hydroxyl of SA is found to strongly stabilize the cyanide ion involved intermediates and transition states via hydrogen bond interactions, while the Au(I) ion always acts as a counter cation. The overall reaction is exergonic by 41.8 kcal/mol. The hydroacylation of phenyl acetylene is the rate-determining step and responsible for the regioselectivity with a free energy barrier of 27.3 kcal/mol. These calculated results are in qualitative accord with the experimental findings.

High performance cyanide sensing with tunable limit of detection by stimuli-responsive gold nanoparticles modified with poly (N,N-dimethylaminoethyl methacrylate).

Detection of cyanide ion (CN-) and design of new sensors with high sensitivity and selectivity are interesting topics in recent developments. Cyanide ions lead to immediate dissolution of gold nanoparticles (AuNPs) and distinct color changes from red to transparent colorless solution. The presence of any material e.g. stabilizer may affect dissolution mechanism and hence sensing properties. Here, we represent a novel sensor (Au-PDA) based on the AuNPs coated with poly (N,N-dimethylaminoethyl methacrylate) (PDMAEMA) for the detection of CN- with tunable sensitivity. PDMAEMA bearing tertiary amine groups not only induced stimuli-responsivity to the prepared Au-PDA as the sensor, but also influenced the sensing performance like linear response range and limit of detection (LOD). The detection process with the increase in CN- concentration in wide range of pHs as well as high ionic strength of the medium was monitored by reduction of the localized surface plasmon resonance band of AuNPs at 530 nm. In the optimized condition, this sensing approach exhibited excellent selectivity in contrary to other anions and cations. The highest sensitivity was obtained in basic media (i.e. pH 9) with a LOD of 4.7 × 10-6 µM and two linear ranges from 10-5-10-3 µM and 0.04-320 µM. The tunable sensitivity could be considered as the strength point of such sensor with lowest LOD for detection of CN- and such a controlled stimuli-responsivity will open up a promising route toward adjustable detection of other chemicals.

Visual detection of cyanide ion in aqueous medium by a new chromogenic azo-azomethine chemosensor.

A simple and new chromogenic azo-azomethine chemosensor N'-(5-((2,4-dichloro- phenyl) diazenyl)-2-hydroxylbenzylidene) picolinohydrazide (L) has been synthesized as an effective colorimetric sensor for cyanide ion. The sensing behavior of the probe L towards CN- over other anions was examined by naked-eye, UV-vis spectroscopy and NMR studies. L exhibited a selective sensing ability to CN- in DMSO/H2O(6:4, v:v) binary solution and DMSO/Tris(10 mM, pH = 7.1, 6:4, v:v) buffer solution by changing color from colorless to yellow. The detection limit was calculated to be 6.4 µM. The recognition mechanism was attributed to deprotonation process according to 1H NMR titration method. Moreover, test strips coated with L were easily fabricated with low cost and could be used to detect CN- in aqueous solution conveniently.

Catalytic Deacetylation of p-Nitrophenyl Thioacetate by Cyanide Ion and Its Sensor Applications.

We demonstrated a simple and rapid deacetylation reaction of p-nitrophenyl thioacetate by cyanide ion. This reaction is caused by the strong nucleophilic tendency of the cyanide ion to the electrophilic substrate and has been previously reported as the most common method for detecting cyanide ions. Tetrabutylammonium cyanide and sodium cyanide can be used as sources of cyanide ions for catalytic deacetylation reactions. Both catalysts showed almost the same catalytic reaction and the catalytic reaction was instantaneous at room temperature with a minimum concentration of cyanide ions of up to 1.0 µM. Cyanide did not catalyze the deacetylation reaction of p-nitropnenyl acetate due to a decrease in the nucleofugality of the leaving group and a decrease in the electrophilicity of carbonyl carbon in the substrate. However, the only disadvantage of this reaction system is the interference with other anions, such as acetate and azide, which also have nucleophilicity toward an electrophilic substrate. If these problems are improved, the system could be applied as a very efficient cyanide ion sensor.

An ionic liquid-modified diarylethene: Synthesis, properties and sensing cyanide ions.

An ionic liquid-modified diarylethene was synthesized and characterized. Its photochromic properties in a variety of solutions were studied. Compared to the neutral diarylethene, the closed-ring isomer of the ionic liquid-modified diarylethene exhibits obvious solvent-dependence. The closed-ring isomer showed solvatochromism depending on the solvent dielectric constants. More importantly, a dual colorimetric cyanide sensor with high selectivity has been achieved based on this ionic liquid-modified diarylethene derivative. Both the open-ring and closed-ring isomers recognized the strongly nucleophilic cyanide by forming of C4-cyano adducts. This study provides a novel design strategy for the development of photochromic diarylethenes for the colorimetric recognition of CN-.