An efficient probe for rapid detection of cyanide in water at parts per billion levels and naked-eye detection of endogenous cyanide

Membrane-Bound Bisindolyl-Based Chromogenic Probes: Analysis of Cyanogenic Glycosides in Agricultural Crops for Possible Remediation

Cyanogenic glycosides are plant-derived, nitrogen-containing secondary metabolites that release toxic cyanide ions upon hydrolysis by glycosidic enzymes. Therefore, consuming food items enriched with such compounds without proper remediation can cause acute cyanide intoxication. Thus, in this work, we utilize cyanide-responsive oxidized bisindole-based chromogenic probes to detect cyanogenic glycosides, such as amygdalin and linamarin (LOD: 0.12 μM), in phospholipid membranes. The bilayer surface, owing to its distinct microenvironment, enhances both the sensitivity and specificity of the probes toward amygdalin. The chromogenic response (red to yellow) is influenced by the nature of the lipid membrane (order, polarity, and interfacial hydration) as well as the number of bis-indolyl units in the probe molecules. Semiquantitative analysis of food samples before and after cooking revealed that soaking in water at room temperature significantly reduces the cyanogenic glycoside content. The ability to directly detect cyanogenic glycosides in food samples without pretreatment is a notable aspect of this investigation.

An indolium ion-based colorimetric sensor for naked-eye detection of cyanide and ammonia: on-site detection technique for cyanide in natural sources and day-to-day monitoring of food spoilage

Herein, we developed an easy-to-synthesize, simple colorimetric probe and demonstrated its potential for the detection of anions and amines. The probe was capable of detecting CN- selectively among other anions and could detect the presence of all tested amines. It exhibited obvious colour and spectroscopic changes in the presence of the said analytes. The probe was highly sensitive to CN- ions, which enabled the detection of trace amounts of the aforementioned anion. The detection limit for CN- was found to be 3.98 × 10-8 M, which is below most of the LOD values reported thus far. The sensing was further extended to the solid state by effectively immobilizing the probe in a hydrogel matrix. Moreover, upon exposure to ammonia vapour, noticeable colour changes were observed in a probe-coated paper chip within few minutes. Moreover, the practical application of the probe was demonstrated for both CN- and amines. The probe can serve as a promising alternative for detection of CN- content in food and monitoring of biogenic amines and food freshness.

Colorimetric chemosensors for the selective detection of arsenite over arsenate anions in aqueous medium: Application in environmental water samples and DFT studies

Novel organic receptors N3R1- N3R3 were developed for the selective colorimetric recognition of arsenite ions in the organo-aqueous media. In the 50% aq. acetonitrile media and 70% aq. DMSO media, receptors N3R2 and N3R3 showed specific sensitivity and selectivity towards arsenite anions over arsenate anions. Receptor N3R1 showed discriminating recognition of arsenite in the 40% aq. DMSO medium. All three receptors formed a 1:1 complex with arsenite and stable for a pH range of 6-12. The receptors N3R2 and N3R3 achieved a detection limit of 0.008 ppm (8 ppb) and 0.0246 ppm, respectively, for arsenite. Initial hydrogen bonding on binding with the arsenite followed by the deprotonation mechanism was well supported by the UV-Vis titration, ¹H- NMR titration, electrochemical studies, and the DFT studies. Colorimetric test strips were fabricated using N3R1- N3R3 for the on-site detection of arsenite anion. The receptors are also employed for sensing arsenite ions in various environmental water samples with high accuracy.

Colorimetric and fluorimetric detection of fluoride ion using thiazole derived receptor

Thiazole based receptor 3, was designed and synthesized by condensation reactionof5-chlorosalicylaldehyde with 4-(4-phenylthiazol-2-yl)semicarbazide for colorimetric and fluorimetric detection of fluoride ion. Receptor 3 was characterized by ¹H NMR, ¹³C NMR, and HRMS, and shows absorption in 280-400 nm region with emission at 442 nm in tetrahydrofuran (THF). Addition of fluoride ion to the THF solution of receptor 3 results in color change from colorless to yellow with significant change in UV-Visible absorption. The receptor-anion interaction occurs via hydrogen bonding followed by deprotonation which results in large bathochromic shift in absorption spectra and naked-eye color change. The colorimetric changes show selective response for fluoride ions over other anions. Fluorescence studies exhibit remarkable enhancement in emission intensity upon addition of fluoride ion with a limit of detection (LOD) of 8.6 nM. The ¹H NMR titration studies exhibit deprotonation of the -OH proton of the salicylaldimine moiety resulting significant colorimetric and fluorimetric changes.

Ppb-Level, Dual Channel Sensing of Cyanide and Bisulfate Ions in Aqueous Medium: Computational Rationalization of Ion-Dependent ICT Mechanism

In this report, three oxidized diindolylarylmethane (DIAM) based chromogenic probes (designated as 1, 2, and 3) have been developed for the simultaneous and dual-channel detection of cyanide (LOD: 6.2 ppb)...

Aggregation-Induced Emission-Based Material for Selective and Sensitive Recognition of Cyanide Anions in Solution and Biological Assays

Cyanide is one of the highly poisonous pollutants to our environment and toxic to human health. It is important to develop the widely applicable methods for their recognition to secure safe uses for people coming into contact and handling cyanide and their derivatives. In this regard, the aggregation-induced emission materials possess high potential for the development of simple, fast, and convenient methods for cyanide detection through either "turn-off" or "turn-on". Among the AIE-based materials, tetraphenylethylene is a promising sensor for various sensing applications. In this paper, we have designed and synthesized a TPE-based chemosensor, which shows high sensitivity and displays good selectivity for cyanide (CN-) over others in the presence of interfering Cl-, I-, F-, Br-, HSO4 -, H2PO4 -, NO3 -, HCO3 -, and ClO4 - anions employed. The naked-eye, UV-vis, and fluorescence methods are employed to evaluate the performance of probe 1 toward CN- detection. From these experiments, CN- ions can be detected with a limit of detection as low as 67 nM, which is comparatively lower than that of the World Health Organization (WHO) permissible limit of the cyanide anion, that is, 1.9 μM. From the Job's plot, the 1:1 stoichiometric complexation reaction between probe 1 and CN- was found. The probe was efficiently applied for the detection of CN- ions using a paper strip method. The probe 1 also showed the potential of detecting CN- ions in various food items and in the cell line.

A Highly Selective Turn-on Fluorescent and Naked-eye Colourimetric Dual-channel Probe for Cyanide Anions Detection in Water Samples

A highly selective turn-on fluorescent and naked-eye colourimetric dual-channel probe for cyanide anions (CN-) has been designed and characterized. In the mixed solution (DMSO / H₂O, 9:1, v / v), only CN- could cause an increase in the UV absorption intensity and the corresponding fluorescence intensity increased, and other anions had no significant effect on the probe. After treatment with cyanide in the probe solution, the solution showed a noticeable colour change, from light yellow to purple. Moreover, a fluorescence spectrophotometer can be used to observe that the fluorescence intensity of the solution is significantly enhanced. The response of the colourimetric and fluorescent dual-channel probe to CN- was attributed to nucleophilic addition, and the mechanism was determined by ¹H NMR spectroscopy. In addition, this probe was used to detect CN- in actual water samples, including river water, drinking water, and tap water. The spiked CN- recovery rate is very high (97.2%-100.06%), and analytical precision is also very high (RSD < 2%), which shows its feasibility and reliability for detecting cyanide ions in actual water samples.

Rationally designed imidazole derivative as colorimetric and fluorometric sensor for selective, qualitative and quantitative cyanide ion detection in real time samples

A new imidazole derivative of 1,2-diaminoanthraquinone and fluorene-2-carboxaldehyde was designed as a sensor B2 to selectively detect the cyanide (CN^-) ion through colorimetric and/or fluorometric methods. The photochemical characterizations of sensor B2 were tested using absorption and emission spectral studies in CH₃CN-H₂O (8:2) semi-aqueous medium. An excited state proton transfer process (ESIPT) was proved by theoretical and spectral studies. The colorimetric and fluorescence detection limit of CN^- ion was found to be 5.3 × 10^-6 M and 4.11 × 10^-8 M, respectively. ¹H NMR titration, electrochemical and DFT studies were supported the removal of -NH proton from B2. In order to utilize this sensor in real-time applications, we developed a test cassette which is coated with sensor B2 detected the presence of CN^- ion in the food sample with endogenous cyanide ion.

Helquats as Promoters of the Povarov Reaction: Synthesis of 1,2,3,4-Tetrahydroquinoline Scaffolds Catalyzed by Helicene-Viologen Hybrids

Helquats (HQs) are structurally linked to helicenes and viologens, and they represent an attractive field of research in chemistry and medicinal chemistry. In the present work they were used as catalysts for the synthesis of 1,2,3,4-tetrahydroquinolines in good yields by the Povarov reaction. The substrate scope and the capability of different helquats to promote Povarov reactions are demonstrated. Studies to elucidate mechanistic details revealed that helquats act as single-electron transfer oxidants through a cation-radical mechanism. The screening of the catalytic activity of HQs confirmed that an active HQ must have a LUMO energy below -8.67 eV and the standard redox potential higher (less negative) than -1.2 V vs. the ferrocene/ferrocenium redox couple.

Pyridine-hydrazone-controlled cyanide detection in aqueous media and solid-state: tuning the excited-state intramolecular proton transfer (ESIPT) fluorescence modulated by intramolecular NH⋯Br hydrogen bonding

A new efficient pyridine-hydrazone-substituted naphthalimide receptor 4a-E has been synthesized as a selective colorimetric and fluorescent chemosensor for cyanide sensing in aqueous environments through a unique ESIPT mechanism.

Determination of Cyanide in Water and Food Samples Using an Efficient Naphthalene-Based Ratiometric Fluorescent Probe

Monitoring cyanide levels in water and food samples is crucial. Herein, we rationally developed a simple and efficient fluorescent probe for cyanide determination. The probe displayed selective ratiometric fluorescent response to cyanide. In addition, after treatment with cyanide, the fluorescence ratios (I ₅₀₉/I ₄₆₆) exhibited a good linearity with cyanide concentration in the range of 0-60 μM, and the detection limit was determined to be 0.23 μM (S/N = 3). Significantly, the practical application demonstrated that the probe was able to quantitatively detect cyanide concentration in natural water samples. Monitoring of endogenous cyanide in cherry nut by the probe was also successfully conducted. Notably, upon fabrication of test strips, the probe could be conveniently utilized for field measurement of cyanide in bitter almond without relying on sophistical instruments. Furthermore, the cyanide in potato tissues was determined for the first time by means of fluorescence imaging.

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 easy to make chemoreceptor for the selective ratiometric fluorescent detection of cyanide in aqueous solution and in food materials

A ratiometric fluorescent receptor selectively detects cyanide in aqueous solution and food materials via deprotonation of a phenolic hydroxyl group.

Visual detection of a nerve agent simulant using chemically modified paper strips and dye-assembled inorganic nanocomposite

Chromogenic probe with oxidized bis-indolyl scaffold has been synthesized for the detection of a nerve gas mimicking agent, DCNP (diethyl cyanophosphonate) at pH 8.0 in water. The mechanism of interaction was proposed as the release of cyanide ion through the indole group mediating the hydrolysis of phosphorous-hetero atom bond and, thereafter, the Michael addition of the liberated CN^- ion to the electron deficient C[double bond, length as m-dash]C bond of the bis-indolyl moiety. The reaction featured a remarkable change in color from red to colorless at ambient condition. Then, low-cost and portable paper strips were designed for a rapid and on-site vapor phase detection of DCNP without involving any sophisticated instrument or skilled personnel. Finally, a dye assembled inorganic nanocomposite material was devised to achieve a more sensitive 'turn-on' detection of DCNP in water.

A Disassembly Strategy for Imaging Endogenous Pyrophosphate in Mitochondria by Using an Fe(III) -salen Complex

Inorganic pyrophosphate (PPi) is produced from nucleoside triphosphates in important biosynthetic reactions and is considered a diagnostic marker for various diseases, such as cancer, crystal deposition disease, and arthritis. Traditional methods for biological PPi detection rely on off-line analytics after sample destruction. Molecular probes for imaging this biologically important analyte with temporal and spatial control in living cells are currently in demand. Herein, we report an Fe(III) -salen complex as the first small reaction-based probe for endogenous mitochondrial PPi following a disassembly approach. Significantly, we successfully applied this complex for the detection of increased cellular PPi levels, and its performance was not affected by the presence of mitochondrial ATP in living cells.

A pyrylium–coumarin dyad as a colorimetric receptor for ratiometric detection of cyanide anions by two absorption bands in the visible region

A pyrylium–coumarin dyad behaves as a colorimetric receptor for ratiometric detection of cyanide anions in aqueous media by two absorption bands in the visible wavelength region.

Triarylborane conjugated dicyanovinyl chromophores: intriguing optical properties and colorimetric anion discrimination

Three new triarylborane conjugated dicyanovinyl chromophores (Mes2B-π-donor-DCV); donor: N-methyldiphenylamine () and triphenylamine ( and [with two BMes2 substitutions]) of type A-D-A (acceptor-donor-acceptor) are reported. Compounds exhibit intense charge transfer (CT) absorption bands in the visible region. These absorption peaks are combination CT bands of the amine donor to both the BMes2 and DCV units. This inference was supported by theoretical studies. Compound shows weak fluorescence compared to and . The discrimination of fluoride and cyanide ions is essential in the case of triarylborane (TAB) based anion sensors as a similar response is given towards both the anions. Anion binding studies of , and showed that fluoride ions bind selectively to the boron centre and block the corresponding CT transition (donor to BMes2) leaving the other CT transition to be red shifted. On the other hand, cyanide ions bind with both the receptor sites and stop both the CT transition processes and hence a different colorimetric response was noted. The binding of F(-)/CN(-) induces colour changes in the visible region of the electronic spectra of and , which allows for the naked-eye detection of F(-) and CN(-) ions. The anion binding mechanisms are established using NMR titration experiments.

Fluorescent Ensemble Based on Bispyrene Fluorophore and Surfactant Assemblies: Sensing and Discriminating Proteins in Aqueous Solution

A particular bispyrene fluorophore (1) with two pyrene moieties covalently linked via a hydrophilic spacer was synthesized. Fluorescence measurements reveal that the fluorescence emission of 1 could be well modulated by a cationic surfactant, dodecyltrimethylammonium bromide (DTAB). Protein sensing studies illustrate that the selected ensemble based on 1/DTAB assemblies exhibits ratiometric responses to nonmetalloproteins and turn-off responses to metalloproteins, which can be used to differentiate the two types of proteins. Moreover, negatively charged nonmetalloproteins can be discriminated from the positively charged ones according to the difference in ratiometric responses. Fluorescence sensing studies with control bispyrenes indicate that the polarity of the spacer connecting two pyrene moieties plays an important role in locating bispyrene fluorophore in DTAB assemblies, which further influences its sensing behaviors to noncovalent interacting proteins. This study sheds light on the influence of the probe structure on the sensing performance of a fluorescent ensemble based on probe and surfactant assemblies.

A fluoride-sensing receptor based on 2,2'-bis(indolyl)methane by dual-function of colorimetry and fluorescence

A compound based on 2,2'-bis(indolyl)methane containing nitro group was studied as a new anion receptor. It could recognize selectively F(-) by an increasing fluorescence signal and a visible color change from colorless to blue. The introduction of nitro group induced the spectral dual-function related to the deprotonation of N-H protons.

Two-Photon Sensing and Imaging of Endogenous Biological Cyanide in Plant Tissues Using Graphene Quantum Dot/Gold Nanoparticle Conjugate

One main source of cyanide (CN(-)) exposure for mammals is through the plant consumption, and thus, sensitive and selective CN(-) detection in plants tissue is a significant and urgent work. Although various fluorescence probes have been reported for CN(-) in water and mammalian cells, the detection of endogenous biological CN(-) in plant tissue remains to be explored due to the high background signal and large thickness of plant tissue that hamper the effective application of traditional one-photo excitation. To address these issues, we developed a new two-photo excitation (TPE) nanosensor using graphene quantum dots (GQDs)/gold nanoparticle (AuNPs) conjugate for sensing and imaging endogenous biological CN(-). With the benefit of the high quenching efficiency of AuNPs and excellent two-photon properties of GQDs, our sensing system can achieve a low detection limit of 0.52 μM and deeper penetration depth (about 400 μm) without interference from background signals of a complex biological environment, thus realizing sensing and imaging of CN(-) in different types of plant tissues and even monitoring CN(-) removal in food processing. To the best of our knowledge, this is the first time for fluorescent sensing and imaging of CN(-) in plant tissues. Moreover, our design also provides a new model scheme for the development of two-photon fluorescent nanomaterial, which is expected to hold great potential for food processing and safety testing.

Corrin-based chemosensors for the ASSURED detection of endogenous cyanide

Cassava (Manihot esculenta Crantz) is a staple food for more than 500 million people, especially in Africa and South America. However, its consumption bears risks as it contains cyanogenic glycosides that convert enzymatically to toxic cyanide during cell damage. To avoid serious health problems by unintentional cyanide intake, this dangerous product of decomposition must be removed before consumption. For monitoring such food processing procedures and for controlling the quality and safety of cassava products on the market, a convenient and reliable analytical method for routine applications without laboratory equipment is required. This Perspective summarizes the authors' work on corrin-based chemosensors for the ('naked-eye') detection of endogenous cyanide in cassava samples. Considering selectivity, sensitivity, handling and speed of detection, these systems are superior to currently applied methods. Based on these properties, the development of a test kit for application by rural farmers in remote locations is proposed.

Fluoride binding in water with the use of micellar nanodevices based on salophen complexes

Uranyl-salophen complexes incorporated into micelles are evaluated as supramolecular nanosystems for the binding of fluoride in water.

Detecting biologically relevant phosphates with locked salicylaldehyde probes in water

This communication describes a disassembly based approach for the detection of biologically relevant di- and tri-phosphates in water using locked fluorescent salicylaldehyde probes.

A novel phenylacetylene-indolium fluorophore for detection of cyanide by the naked eye

The compound 2 mixed α-cyclodextrin exhibits the highest CN⁻ recognition sensitivity in aqueous media with the detection limit of 1.3 μM. Test strips based on compound 2 can act as a convenient and efficient CN⁻ test kit.

An imidazolyl-pyreno-imidazole conjugate as a cyanide sensor and a set–reset memorized sequential logic device

A pyrenyl-bisimidazole system can act as an efficient cyanide sensor and a ‘set–reset’ memory device.

Fluorescent probes for the detection of cyanide ions in aqueous medium: cellular uptake and assay for β-glucosidase and hydroxynitrile lyase

A chemodosimetric reagent for specific detection of cyanide species and its possible use in imaging applications as well as assay development for important enzymes.

Chromogenic chemodosimeter for highly selective detection of cyanide in water and blood plasma based on Si-O cleavage in the micellar system

A novel silylated imine was designed to act efficiently in a chemodosimeter approach for the selective detection of cyanide in an aqueous micellar CTABr solution. This simple system allows the detection of cyanide, with high sensitivity and specific selectivity, in water and in human blood plasma.

Reaction-based fluorescent probe for detection of endogenous cyanide in real biological samples

Herein, two compounds (1 a and 1 b) were rationally constructed as novel reaction-based fluorescent probes for CN(-) by making use of the electron-withdrawing ability of the cyano group that was formed from the sensing reaction. Notably, this design strategy was first employed for the development of fluorescent CN(-) probes. The experimental details showed that probe 1 a exhibited a fluorescence turn-on response to CN(-), whereas other anions, biological thiols, and hydrogen sulfide gave almost no interference. The detection limit of probe 1 a for CN(-) was found to be 0.12 μM. The sensing reaction product of 1 a with CN(-) was characterized by NMR spectroscopy and mass spectrometry. TD-DFT calculations demonstrated that the formed cyano group drives the intramolecular charge transfer (ICT) process from coumarin dye to the cyano group and thus the original strong ICT from the coumarin dye to the 3-position pyridyl vinyl ketone substituent is weakened, which results in recovery of coumarin fluorescence. The practical utility of 1 a was also examined. By fabricating paper strips, probe 1 a can be used as a simple tool to detect CN(-) in field measurements. Moreover, probe 1 a has been successfully applied for quantitative detection of endogenous CN(-) from cassava root.