Detection Of Cyanide In Water Research Articles

Miniaturized dual-wavelength β-correction spectrophotometric probe for sensitive detection of cyanide in water via formation of cyano dithizone adduct

Cyanide toxicity in water significantly threatens public health and the environment. To address this, a miniaturized simple, low-cost, selective and sensitive direct dual wave β-correction spectrophotometric probe has been established for cyanide detection in water. The dual-wavelength β-correction spectrophotometry enhances the selectivity and sensitivity of the probe in the presence of interfering species. The assay relies a highly selective nucleophilic addition of cyanide ions to dithizone (H2Dz) as chromogenic reagent in aqueous media of pH 6.8–7.2, forming a red-colored cyano H2Dz adduct. The electronic spectrum of the formed adduct displays a sharp absorption peak at λmax = 480 nm, enabling precise colorimetric detection. The molar absorptivity and Sandell’s sensitivity index for the cyano H2Dz adduct with and without β-correction spectrophotometry were 5.62 × 103, and 1.79 × 103 L mol−1 cm−1, and 0.002 and 0.0033 µg cm−2, respectively. Beer’s law and Ringbom’s plots are valid in the range 0.01–5.0 and 0.06–2.0 µg mL−1 CN– concentration, respectively. The limits of detection (LOD) and quantification (LOQ) improved from 1.03 × 10−1 and 3.13 × 10−1 μg/mL using ordinary spectrophotometry to 2.8 × 10−2 and 8.7 × 10−2 μg mL−1 employing β-correction spectrophotometry. The probe offers rapid response, good anti-interference ability, reproducibility, and cost-effectiveness. The probe was successfully applied for detection of trace levels of cyanide ions in water with good repeatability. It has been also validated in water samples with good recoveries (99.2 ± 5.02 %). The experimental Student t test (texp = 1.2–1.5) was lower than the critical (texp = 2.78) at 95 % probability (n = 5). The stoichiometry and mechanism of formation of the cyano adduct were assigned and addressed.

Progress in Organic Triboluminescent EuD4TEA Crystal

AbstractOrganic triboluminescent (TL) crystals have attracted significant attention in recent years for their potential applications in various fields such as damage sensing in aerospace structures, cyanide detection in water, and radiation sensing. Europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA) is a class of organic TL crystals that have shown promising results in terms of sensitivity due to their high TL intensity, however, they exhibit thermal instability and fragility concerns. In this review, recent research progress on the development, characterizations, TL properties, and potential applications of EuD4TEA crystals in various fields, are summarized. The review will conclude with the current challenges of EuD4TEA crystals, such as fragility nature, thermal instability, and increasing cost of europium. Despite having challenges, EuD4TEA crystals have the potential for damage sensing in the structural composite.

Water-soluble AIE-active Fluorescent Organic Nanoparticles: Design, Preparation and Application for Specific Detection of Cyanide in Water and Food Samples.

A dilactosyl-dicyanovinyl-functionalized tetraphenylethene (TPELC) was designed, synthesized and used for ratiometric sensing of cyanide. TPELC was comprised of three moieties (tetraphenylethylene, dicyanovinyl group and lactose unit) in one molecule, making TPELC water-soluble and aggregation-induced emission (AIE)-active and selectively reactive to cyanide. Compared with other reported fluorescent probes containing dicyanovinyl group, TPELC is the first AIE luminogen to be assembled as fluorescent organic nanoparticles (FONs) for sensing of cyanide in water without the use of surfactant or the help of organic solvents based on the nucleophilic addition reaction. The detection mechanism was verified by liquid chromatograph mass spectrometry experiments and by protonation of cyanide to reduce the nucleophilicity of cyanide. In addition, TPELC was used for detection of the cyanide content of food samples and test strips were developed to simplify the detection procedure.

A TiO2 Nanotube-Based Sensor for the Detection of Cyanide in Water

Cyanide is an acutely toxic compound capable of reducing or eliminating oxygen utilization in living organisms on exposure. Natural and industrial processes contribute to the presence of cyanide in the environment. However, the concentrated nature of industrial-process-derived cyanide calls for greater attention. The ability to bind to other compounds makes cyanide capable of spreading to ground and surface waters more easily than other industrial contaminants. Cyanide concentrations in waste waters need monitoring to ensure that they are within permissible levels. Furthermore, cyanide is an essential reagent in some processes, and thus tracking of cyanide concentrations in the process line is essential. Real-time monitoring of cyanide concentrations calls for a robust and quick method for detection of cyanide concentrations in water. As such, this work focuses on the application of titanium dioxide (TiO2) nanotubes for the sensitive and selective electrochemical detection of cyanide in water. The TiO2 nanotubes were modified by the addition of iron (Fe) and sulfur (S) to the nanotube structures. Characterization of the prepared sensing electrode was carried out using X-ray diffraction and electron microscopy. Electrochemical sensing of the cyanide in water was performed using a three-electrode system with an Fe-S-TiO2 working electrode. Cyclic voltammetry was used to establish the sensing of the cyanide species as well as the response to cyanide concentration in water. Chronoamperometry was used to test the effect of interfering species as well as the sensor sensitivity, with an observed current response to a 0.1μM change in cyanide concentration. The sensor response indicated that an Fe-S-TiO2 sensing electrode could effectively be used for the sensing of cyanide concentrations lower than the recommended limits in water, and with good sensing electrode reusability.

Gold nanoparticles-decorated paper-based sensor for rapid cyanide detection in water

In this study, a versatile sensing platform based on a commercially available filter paper for the development of a colorimetric sensor using label-free gold nanoparticles (AuNPs) for the detection of cyanide in water is presented. The developed sensor can be applied for the direct detection of cyanide from an aqueous sample efficiently in a wide concentration range. The synthesised AuNPs were found to have an average size of about 13.2 ± 2.65 nm with a surface plasmon resonance peak at around 525 nm. Successful integration of AuNPs on the WFP substrate was observed through the FESEM-EDX analysis and supported by the presence of an absorbance peak at about 528 nm on the spectrum of the WFP-AuNPs composite. The colour of the WFP-AuNPs composite changed from purple-red to white in the presence of cyanide. Using the paper-based sensor, the limit of detection is calculated to be 7.68 × 10−6 M (0.5 ppm). The said sensitivity is good enough for the determination of cyanide in industrial wastewater samples. The developed sensor also showed excellent selectivity towards cyanide over other ions, demonstrating its practical applicability to monitor cyanide contamination in different environmental samples. Furthermore, the applicability of the sensor was demonstrated using several real water samples spiked with cyanide, including creek and tap water. Notably, the sensor showed great promise for the rapid, cost-effective, and versatile monitoring of cyanide contamination in various aqueous samples.

TiO2 Nanotube-Based Sensor for the Detection of Cyanide in Water

Cyanide is an acutely toxic compound capable of spreading to ground and surface waters more easily than other industrial contaminants. Real-time monitoring of cyanide concentrations calls for a robust and quick method for cyanide detection in water. This work focuses on the application of anodized titanium dioxide (TiO2) nanotubes as a substrate, with suitable and relatively inexpensive additives, for the sensitive and selective electrochemical detection of cyanide in water. The TiO2 nanotubes were modified by the addition of iron (Fe) and sulfur (S) as sensing elements. Characterization of the prepared sensing platform was performed using X-ray diffraction and electron microscopy. Current-time measurements indicated that i) increasing cyanide concentration can perturb the current proportionally, ii) the differential in the current can be used as a calibration for quantitative detection of cyanide, and iii) the sensor is highly selective even in the presence of interfering species. A cyanide detection limit of 0.49 μM and a sensitivity of −13.8 mAcm−2 μM−1 were established. The sensor response indicated that an Fe-S-TiO2 nanotube sensing electrode could effectively and repeatedly be used over a period of several months for the sensing of cyanide concentrations lower than the recommended WHO and USEPA limits in water.

Cyanide Sensing in Water Using a Copper Metallogel through "Turn-on" Fluorescence.

The development of fluorescent probes for selective detection of cyanide has gained considerable attention over the past two decades due to benefits like high selectivity as well as sensitivity, fast response, visual output, accurate quantification, and a simplified sample preparation procedure. However, the propensity of supramolecular gels toward fluorescence sensing of cyanide in aqueous medium is not well explored until now. Herein, we report the design and synthesis of a novel copper based metallogel capable of sensing cyanide in water by fluorescence "turn on". Toward this, a terpyridine attached poly(aryl ether) dendrone derivative (G1) is synthesized which forms gel and exhibits Aggregation Induced Emission (AIE). The addition and diffusion of copper ions to the gel resulted in the formation of a nonluminescent copper metallogel (CuG). The copper metallogel could selectively sense cyanide in water by a fluorescence "turn-on" signal due to the regeneration of the AIE active gel. The mechanistic pathways of the sensing have been studied, and the detection limit for sensing was found to be as low as 1.09 μM. A thin film of CuG was prepared by casting the gel and used as a test strip for the visual detection of cyanide in water.

Metal complexation induced supramolecular gels for the detection of cyanide in water

ABSTRACT The role of metal salts in inducing supramolecular gel network formation was analysed by reacting two pyridyl-N-oxide amides with various diamagnetic zinc(II) and cadmium(II) salts. Metal induced supramolecular gelation was observed for zinc(II) and cadmium(II) chloride complexes in water and the morphologies of the xerogels were analysed by scanning electron microscopy (SEM). The relative gel strength was corroborated with various non-bonding interactions observed in the solid-state structures of zinc(II) complexes using X-ray diffraction. The non-bonding interactions of the pyridyl-N-oxide amides and the metal complexes were compared to find the key interactions responsible for metallogel formation. The anion induced stimuli-responsive property of the metallogels was studied in the presence of halides and cyanide anions. The cadmium(II) gels were stable in presence of two equivalents of halides but the network collapsed in presence of cyanide anion in water and this property can be used to detect cyanide anions in water.

A novel colorimetric and fluorometric probe for the detection of CN− with high selectivity in aqueous media

A novel colorimetric and fluorometric probe L1 for detecting CN− with high selectivity was constructed and synthesized based on intramolecular charge transfer (ICT). Remarkably, L1 was found to be exclusively responsive to CN− via nucleophilic attack of dicyanovinyl group via 1H NMR titration experiment. The detection system exhibited “turn-on” fluorescence with the addition of cyanide, which was opposite to previously reported fluorescence quenching probes with the same sensing process. Moreover, the detection limit of L1 for CN− was determined to be 1.1 μM, lower than the standard (1.9 μM) regulated by the World Health Organization (WHO). This work demonstrated that L1 could serve as both a colorimetric and a fluorimetric sensor for cyanide detection in pure water, making it possible for the applications of cyanide detection in water.

AIE-active polysulfatesviaa sulfur(vi) fluoride exchange (SuFEx) click reaction and investigation of their two-photon fluorescence and cyanide detection in water and in living cells

Three polysulfates P1, P2 and P3 containing two representative AIE-active groups, tetraphenyl ethylene and naphthylamide, were successfully synthesized based on a sulfur(vi) fluoride exchange (SuFEx) click reaction.

Highly selective turn-on fluorescent probe for detection of cyanide in water and food materials

A naphthoquinone-imine based fluorescent probe (R) has been synthesized and characterized by NMR and mass spectral techniques. The receptor shows high selectivity towards cyanide in water in the presence of other competitive anions with an instantaneous colour change from non-emissive to green under UV light. The turn-on fluorescence is due to deprotonation of three hydroxyl groups by cyanide ions as evidenced from 1H NMR titration experiment. The LOD of cyanide by R in water is 0.6 μM, which is much lower than the permissible limit of cyanide in drinking water according to the WHO.

A highly selective and sensitive dual-mode sensor for colorimetric and turn-on fluorescent detection of cyanide in water, agro-products and living cells

A new highly selective and sensitive dual-mode sensor 3TD based on the conjugate of oligothiophene and barbituric acid moiety was developed for colorimetric and turn-on fluorescent detection of CN─. The sensor 3TD exhibited high specificity towards CN─ by interrupting its own ICT producing thereupon a large blue-shift in UV–Vis spectrum and remarkable “turn-on” fluorescence emission. The detection limit was 2.26 × 10─7 M, which is quite lower than the permissible level of CN─ in drinking water according to the WHO. The fluorescent detection of CN─ was well demonstrated by filter paper strips and silica coated TLC plates. Moreover, the sensor was also used to detect CN─ in environmental water and agro-products with satisfactory results. Most importantly, in terms of these advantages of colorimetric and turn-on fluorescent dual-mode, immediate response, excellent selectivity, high sensitivity, low cytotoxicity, and good biocompatibility, the sensor 3TD was successfully applied into CN− imaging in living cells, demonstrating its excellent value in practical application.

Paper-based headspace extraction combined with digital image analysis for trace determination of cyanide in water samples

A simple, cost-effective, instrumental free and user-friendly analytical method based on the combination of paper-based headspace extraction and digital scanning image analysis was developed for the sensitive detection of cyanide in water and wastewater samples. The method relied on chloramine-T/pyridine-barbituric acid reaction, which is a well-known process for measuring cyanide in standard analytical methods. During the reaction, cyanide was converted to cyanogen chloride, which was extracted and collected on a paper impregnated with pyridine-barbituric acid. The color appeared on the paper was used to quantify the analyte using a scanning-assisted image processing software. Experimental parameters affecting the sensitivity of the method such as stirring rate, paper size, chloramine-T and barbituric acid concentration, equilibrium and extraction time were studied. Under optimal conditions, the calibration curve was linear in the range of 3.0–100 μg L−1 with the detection limit of 0.7 μg L−1. The intra- and inter- day relative standard deviations of the method at 10 and 70 μg L−1 concentration levels were less than 6%. Analyte recovery in real samples was in the range of 69–111%.

Synthetic green fluorescent protein (GFP) chromophore analog for rapid, selective and sensitive detection of cyanide in water and in living cells

Here, we report Green Fluorescent Protein (GFP) chromophore analog as a turn-on fluorescent chemodosimeter (THBI) for selective detection of cyanide in water, on solid state and in living cells. The detection limit was found to be 0.17 μM (4.5 ppb). The time dependent study revealed that there is a rapid enhancement in fluorescence intensity (in less than 5s) and was constant over the period of 1 h. Cell imaging data exhibited that THBI was successfully crossed cell membrane and visualized fluorescence response in live HCT cells.

Capped Mesoporous Silica Nanoparticles for the Selective and Sensitive Detection of Cyanide.

The development of easy and affordable methods for the detection of cyanide is of great significance due to the high toxicity of this anion and the potential risks associated with its pollution. Herein, optical detection of cyanide in water has been achieved by using a hybrid organic-inorganic nanomaterial. Mesoporous silica nanoparticles were loaded with [Ru(bipy)3 ]2+ , functionalized with macrocyclic nickel(II) complex subunits, and capped with a sterically hindering anion (hexametaphosphate). Cyanide selectively induces demetallation of nickel(II) complexes and the removal of capping anions from the silica surface, allowing the release of the dye and the consequent increase in fluorescence intensity. The response of the capped nanoparticles in aqueous solution is highly selective and sensitive towards cyanide with a limit of detection of 2 μm.

A novel indolium salt as a highly sensitive and selective fluorescent sensor for cyanide detection in water

A highly sensitive fluorescent turn-on cyanide probe is developed based on benzylidenes containing methylindolium group. Three benzylidene derivatives were synthesized from the condensations of three benzaldehyde derivatives and methyleneindoline. Only one of these three derivatives shows strong blue fluorescent response selectively to CN− which can be clearly observed in submicromolar range as the result of the cyanide addition to the indolium group. The detection of cyanide with this compound is optimized in aqueous media using non-ionic surfactant and sonication method to give very low limit of detection in subnanomolar range. The probe is also developed into a paper-based and gel-based sensing kits that can readily detect cyanide ion in micromolar range by naked eye under a common black light (360nm) illumination.

Fluorescence light-up detection of cyanide in water based on cyclization reaction followed by ESIPT and AIEE.

Schiff base 1 (2,4-di-tert-butyl-6-((2-hydroxyphenyl-imino)-methyl)phenol) containing two hydroxyl groups could undergo an oxidative cyclization reaction and then generate hydroxyphenylbenzoxazole (HBO) 2 when CN- was present as a catalyst. The multistep cyclization reaction was proved by spectroscopy, 1H NMR, 13C NMR and mass spectra. C[double bond, length as m-dash]N isomerization is the predominant decay process of the excited states, so sensor 1 is weakly emissive in solution at ambient temperature. When 1 reacts with CN-, the emission is remarkably enhanced, where 1 is converted to 2. The cyclization product HBO 2 displays bright green luminescence in micellar due to the ESIPT (excited-state intramolecular proton transfer) as well as AIEE (aggregation-induced emission enhancement) effect. The detection limit is 5.92 × 10-7 M, lower than the WHO guideline of CN- in drinking water (1.9 μM). The selective and competitive experiments reveal that sensor 1 shows high sensing selectivity and sensitivity for CN- over other anions. Test papers containing absorbed 1 were prepared and applied for practical application of cyanide detection.

A benzimidazole functionalized NDI derivative for recyclable fluorescent detection of cyanide in water

An NDI-based chemosensor (L2) was synthesized via a one step reaction; L2 showed recyclable CN− detection properties in water.

Optical devices for the detection of cyanide in water based on ethyl(hydroxyethyl)cellulose functionalized with perichromic dyes

Films of three polymers, based on ethyl(hydroxyethyl)cellulose functionalized with protonated perichromic dyes, were used for anion sensing. The polymer functionalized with protonated Brooker’s merocyanine acts as a chromogenic/fluorogenic system for the selective detection of cyanide in water. An increase of >28 times was verified for the fluorescence lifetime of the sensing units in the polymer in comparison with protonated Brooker’s merocyanine in water. Moreover, an increase in the pKa values was verified for the sensing units in the polymers. Data suggest that the hydrocarbonic polymeric chains provide an adequate microenvironment to protect the sensing unit from bulk water. The other polymer, functionalized with an iminophenol, also showed high selectivity for cyanide (detection limit=9.36×10−6molL−1 and quantification limit=3.12×10−5molL−1). The polymer functionalized with azophenol units is unable for the detection of cyanide, due to the low pKa value verified for its chromogenic units.

Malononitrile–derivative chromogenic devices for the detection of cyanide in water

Two compounds, 2–(4–hydroxybenzylidene)malononitrile (1a) and 2–[4–(dimethylamino)benzylidene]malononitrile (2), were synthesized with a view to their use as optical devices for anionic detection. Compound 1a was studied as a chromogenic chemosensor using an acid–base strategy. In purely aqueous medium, 1a was used in the detection of CN− with high selectivity. This is possible because the colorless solution of the compound becomes yellow upon addition of the anion, which acts as a base and abstracts the hydrogen from the phenolic moiety of the molecule, generating the corresponding dye (1b). Optical detection and optical quantification limits were determined as 6.17×10−7molL−1 and 2.06×10−6molL−1, respectively. These values are much lower than the maximum level of the concentration of CN− allowed by the World Health Organization in potable water (1.7μmolL−1). Compound 2 was used in a chemodosimeter approach for the highly selective detection of CN− in water with cetyltrimethylammonium bromide above its critical micellar concentration. Solutions of 2 are yellow but become colorless with the addition of the anion. This is because CN− attacks the CHC double bond in the compound and disrupts the electronic conjugation between the electron donating and the electron accepting moieties of the dye. Thus, with the addition of CN− to the medium compound 1a acts as an off–on optical device while dye 2 operates as an on–off chemodosimeter.