A selective, colorimetric, and fluorescent chemodosimeter for relay recognition of fluoride and cyanide anions based on 1,1'-binaphthyl scaffold

Spectroscopic and TD-DFT studies on the chromo-fluorogenic detection of cyanide ions in organic and aquo-organic media

A new naked-eye chromogenic and fluorogenic probe KS5 has been developed for the detection of CN- ions in neat DMSO and H2O:DMSO (1:1 v/v) media. The probe KS5 exhibited selectivity towards CN- and F- ions in organic and high selectivity towards CN- ions in aquo-organic media resulting in a colour change from brown to colourless and a turn-on fluorescence response. The probe could able to detect CN- ions via a deprotonation process, which was conceived by consecutive addition of hydroxide and hydrogen ions and confirmed using 1H NMR studies. The limit of detection (LOD) of KS5 towards CN- ions were in the range of 0.07-0.62 µM in both these solvent systems. Suppression of intra-molecular charge transfer (ICT) transition and photoinduced electron transfer (PET) process of KS5 by the added CN- ions are responsible for the chromogenic and fluorogenic changes observed, respectively. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations strongly supported the proposed mechanism along with the optical properties of the probe before and after the addition of CN- ions. To prove the practical applicability, KS5 was successfully utilized to detect CN- ions in cassava powder and bitter almonds as well as to determine CN- ions in various real water samples.

A Handy Chemical Sensor Based on Benzaldehyde and Imidazo[1,2-a]pyridine Mixture for Naked-eye Colorimetric and Fluorescent Detection of F. J Fluoresc 2023;33:2381-2390. [PMID: 37071230 DOI: 10.1007/s10895-023-03195-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Upon the Schiff base condensation reaction of imidazo[1,2-a]pyridine-2-carbohydrazide and 2,5-dihydroxybenzaldehyde, a bimodal colorimetric and fluorescent chemosensor 1o for assaying fluoride (F-) in DMSO was synthesized. The characterization of 1o structure was obtained by 1H NMR, 13C NMR and MS.The structure of 1o was characterized by 1H NMR, 13C NMR and MS. Under the presence of various anions, 1o could be applied for naked-eye and fluorescent detection of F- (naked eye: colorless to yellow; fluorescence: dark to green) and displayed promising performance, such as high selectivity and sensitivity, as well as a low detection limit. Upon calculation, the detection limit of chemosensor 1o for F- was 193.5 nM, which is well below the allowed maximum value of F- (1.5 mg/L) by WHO. As the intermolecular proton transfer mechanism induced "turn-on" fluorescent signal and naked-eye color change of F- to 1o through deprotonation effect, which was confirmed by Job's plot curve, mass spectrometry and 1H NMR titration. Alternatively, the chemosensor 1o can be effectively manufactured into test strips to detect fluoride in solid state, which is user-friendly with no additional equipment required.

Sequential detection of inflammation-related hypochlorite ions and viscosity with a relay fluorescent probe

Based on the correlation between inflammation and reactive oxygen species and viscosity, a fluorescent probe (SWJT-19) was designed for a relay detection of hypochlorite ions and viscosity. The synthesized probe could quickly and selectively detect hypochlorite ions, as well as viscosity of the system effectively. Moreover, the probe had been successfully applied to sequentially detect hypochlorite ions and viscosity in organisms, as well as imaging in mouse inflammation.

Sequence-Specific Relay Recognition of Multiple Anions: An Interplay between Proton Donors and Acceptors

Ratiometric detection of analyte is highly deserving since the technique is free from background correction. This work reports the design and synthesis of a pyridine-end oligo p-phenylenevinylene (OPV) derivative, 1 and its application in ratiometric dual-mode (both colorimetric and fluorogenic) recognition of dual anions, bisulfate (LOD=12.5 ppb) followed by fluoride (LOD=18.2 ppb) by sequence-specific relay (SPR) technique. The colorless probe turns brown with addition of bisulfate and again becomes colorless with the sequential addition of fluoride ion. In addition to such naked-eye color change, interestingly the ratiometric spectroscopic signals are reversible and evidently, the probe is reusable for several cycles. Besides, in presence of bisulfate, the protonated probe molecules, owing to their larger amphiphilic characteristics, formed self-assembled nanostructures. In addition to colorimetric and fluorescent changes, 1 H NMR titration and systematic DFT study evidently establish the underneath proton transfer mechanisms. Such reusable OPV-based chemosensor particularly with the capability of naked-eye recognition of dual anions using the SPR technique is seminal and possibly the first report in the literature.

A highly selective probe for fluorometric sensing of cyanide in an aqueous solution and its application in quantitative determination and living cell imaging

A simple fluorescent probe (KS4) containing multiple reaction sites (phenolic -OH, imine and C = C bonds) is successfully synthesized and characterized using 1H NMR, 13C NMR, mass and single crystal XRD techniques. KS4 exhibits high selectivity towards CN- over a wide range of common anions in H2O:DMSO (1:1 v/v) leading to an amazing turn-on fluorescence at 505 nm via deprotonation of the phenolic -OH group. The limit of detection (1.3 µM) for CN- was much below the standard (1.9 µM) set by the World Health Organization (WHO). Stoichiometry of the interaction between KS4 and CN- was ascertained as 1:1 by the Job's plot method and the binding constant was determined to be 1.5x104 M-1. Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) based theoretical insight has been appealed to understand the optical properties of KS4 before and after the addition of CN- ion. The probe shows respectable real-time applicability for qualitative detection of CN- in almond and cassava powder as well as quantification in real water samples with excellent recoveries (98.8 - 99.8%). In addition, KS4 is found to safe towards living HeLa cells and successfully applied to the detection of endogenous cyanide ions in HeLa cells.

Synthesis of novel 3-hydroxy-2-naphthoic hydrazones as selective chemosensors for cyanide ions

The development of an effective and selective chemosensor for CN^- ions has become the need of the hour due to their hazardous impact on the environment and humans. Herein, we report the synthesis of two novel chemosensors, IF-1 and IF-2 based on 3-hydroxy-2-naphthohydrazide and aldehyde derivatives that have shown selective sensing of CN^- ions. IF-2 exhibited exclusive binding with CN^- ions that is further confirmed by the binding constant value of 4.77 × 10⁴ M^-1 with a low detection limit (8.2 μM). The chemosensory potential is attributed to deprotonation of the labile Schiff base center by CN^- ions that results in a color change from colorless to yellow as visible by the naked eye. Accompanying this, a DFT study was also performed in order to find the interaction between the sensor (IF-1) and its ions (F^-). A notable charge transfer from 3-hydroxy-2-naphthamide to 2,4-di-tert-butyl-6-methylphenol, was indicated by the FMO analysis. The QTAIM analysis revealed that in the complex compound, the strongest pure hydrogen-hydrogen bonding was observed between H53 and H58, indicated by a ρ value of +0.017807. Due to its selective response, IF-2 can be successfully used for making test strips for the detection of CN^- ions.

Triarylborane-triphenylamine based luminophore for the mitochondria targeted live cell imaging and colorimetric detection of aqueous fluoride

Bioimaging of subcellular organelles such as mitochondria is crucial for detecting physiological abnormalities induced by fluctuations in the levels of various analytes. Herein, we report the design and synthesis of two novel water-soluble cationic Lewis acid triarylborane-triarylamine conjugates 1 and 2. The optical characteristics of 1 and 2 and their precursor compounds BTPA-NMe2 and BTPA-2NMe2 were evaluated, which show similar absorption and fluorescence spectra, with 1 and 2 exhibiting higher quantum yields of 0.73 and 0.64, respectively, than those of the precursors BTPA-NMe2 and BTPA-2NMe2, indicating the partial disruption of the ICT process and the activation of alternative emission bands in 1 and 2. The live cell imaging ability of compound 2 was examined in HeLa cells using a confocal microscope. Moreover, mitochondrial internalisation using compound 2 was effective and it was found to have high photostability under UV light conditions. Furthermore, compound 2 demonstrated an evident colorimetric response with a colour change to dark yellow in aqueous environments, indicating that it could be used for anion sensing. The spectral changes were observed in UV-visible and fluorescence titration experiments, which were strongly supported by DFT calculations. In short, compound 2 synthesized by us can be exclusively utilized for the selective localization of mitochondria with less cytotoxicity and shows excellent colorimetric response to aqueous inorganic fluoride at levels as low as 0.1 ppm with high selectivity.

Polymer-based lab-on-a-molecule for the selective and sensitive recognition of fluoride and cyanide

A polymer chemical sensor based on lab-on-a-molecule was synthesised by amine-aldehyde polymerisation for selective detection of fluorine ions (F^-) and cyanide (CN^-). The polymer chemical sensor shows significant absorption and fluorescence changes upon the addition of F^- and CN^-, which can be observed by the naked eye and optical reactions. The polymer has a higher fluorescence enhancement effect than its monomer and the distance of wavelength of each anion increased which could be applied to better distinguish the two anions.

Naked-eye colorimetric and turn-on fluorescent Schiff base sensor for cyanide and aluminum (III) detection in food samples and cell imaging applications

A new efficient Schiff base sensor SB3 for fluorescent and colorimetric "naked-eye" "turn-on" sensing of cyanide anion (CN^-) with excellent sensitivity and selectivity was developed. The 4,4'-(perfluoropropane-2,2-diyl)bisphenol group and two phenyl groups were covalently linked by two C = N bonds to extend the conjugation length. The four hydroxyl groups can improve the water solubility of the SB3 sensor. The SB3 sensor exhibited high specificity towards CN^- by interrupting its intramolecular charge transfer, resulting in a color change and remarkable "turn-on" green fluorescence emission. The sensing mechanism is caused by the nucleophilic addition of CN- toward imine groups of the SB3 sensor, leading to breaks of the conjugation, fluorescent spectral changes, and color change. It was confirmed by ¹H NMR titration and Mass spectra. The detection limits for CN^- and Al³⁺obtained by fluorescence spectrum are 0.80 µM and 0.25 µM, respectively. The SB3 sensor can act as an efficient chemical sensor for detecting the CN^- and Al³⁺ ions under common environmental and physiological conditions (pH 5-12). Besides, the sensor can also detect CN^- in food materials (such as sprouting potatoes and cassava flour) and imaging CN^-in living cells with strong "turn-on" fluorescence at 490 nm. SB3 is an excellent CN^- sensor that exhibits some advantages, including easy synthesis, distinct fluorescence and color change, high selectivity, low detection limit, and good anti-interference ability to analyze solution and food samples, together with fluorescence cell imaging.

A New Reversible Colorimetric Chemosensor Based on Julolidine Moiety for Detecting F. J Fluoresc 2021;31:1675-1682. [PMID: 34387807 DOI: 10.1007/s10895-021-02801-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

We synthesized an original reversible colorimetric chemosensor PDJ ((E)-9-((2-(6-chloropyridazin-3-yl)hydrazono)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol) for the detection of F^-. PDJ displayed a selective colorimetric detection to F^- with a variation of color from colorless to yellow. Limit of detection of PDJ for F^- was calculated as 12.1 µM. The binding mode of PDJ and F^- turned out to be a 1:1 ratio using Job plot. Sensing process of F^- by PDJ was demonstrated by ¹H NMR titration and DFT calculation studies that suggested hydrogen bond interactions followed by deprotonation. Moreover, the practicality of PDJ was demonstrated via a reversible test with TFA (trifluoroacetic acid).

Aggregation-induced emission enhancement (AIEE)-active tetraphenylethene (TPE)-based chemosensor for CN. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021;245:118928. [PMID: 32950857 DOI: 10.1016/j.saa.2020.118928]

An aggregation-induced emission enhancement (AIEE)-active fluorescent sensor has been successfully designed and synthesized, combining the AIE effect of tetraphenylethylene (TPE) with the cyanide acceptor of phenanthro[9,10-d]imidazole. The sensor exhibits not only the property of AIEE in DCM/n-hexane or THF/H₂O, but also the phenomenon of mechanofluorochromic (MFC). It displays large Stokes shift (107 nm) due to the intramolecular charge transfer (ICT) process. The cation of CN^- boosts the ICT process to make the greater Stokes shift (184 nm) with the fluorescent color vary from blue-green to sodium-yellow and visually turning from light yellow to dark yellow in the naked eyes. The results of Job's plot, ESI-MS and the DFT calculations provide the stoichiometric ratio and electronic properties of the sensor. Furthermore, the sensor could be applied to qualitative and quantitative detection of CN^- on test paper strips.

Indirect differential pulse voltammetric analysis of cyanide at porous copper based metal organic framework modified carbon paste electrode: Application to different water samples

Carbon paste electrode (CPE) modified with porous copper based metal organic framework (Cu-MOF) nanocomposite is described for analysis of cyanide (CN^-) for the first time. The electrochemical performance of the proposed electrode was investigated by differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The Cu-MOF nanocomposite was characterized using scanning electron microscope (SEM), N₂-adsorption-desorption isotherms, powder X-ray powder diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Under optimal conditions of measurements, the anodic peak (Ipa) decreases linearly in the range of 1.87-25 μM with LOD of 0.60 μM (at S/N = 3). The Cu-MOF/CPE showed good selectivity towards CN^- measurement with no significant interference in pH 7.0 using 0.25 M KCl to increase the medium conductivity and to stabilize the analyte and prevents its volatility. Moreover, the method was successfully applied for determination of CN^- in different environmental water samples.

Synthesis and application of a new chemosensor based on the thiazolylazo-quinazolinone hybrid for detection of F- and S2- in aqueous solutions

A new chemosensor based on the thiazolylazo-quinazolinone hybrid (TAQH) was designed and synthesized for naked-eye sensitive detection of F^- and S^2-in aqueous acetonitrile solution. Spectral characterization of TAQH using FT-IR, ¹H NMR, and ¹³C NMR analysis revealed that the probe TAQH was successfully synthesized using a two steps reaction, including the diazotization-coupling and condensation reactions, respectively. The ion sensing ability of TAQH toward a wide range of anions and metal ions was evaluated by naked-eye detection method and UV-Vis absorption spectroscopy. The chemosensor TAQH displayed a fast and clear color change from yellow to red in the presence of F^- and S^2- ions, enabling easily detect with the naked eye. This clear color change is due to the effective interaction of the basic F^- and S^2- anions with hydroxyl group of chemosensor as a binding site. The experimental data also revealed that the F^- and S^2- ions were sensed by the probe TAQH over a wide pH range from 3 to 8. The results also confirmed that the TAQH has a wide linear detection range for F^- and S^2- ions. From UV-vis titration experiment, the limit of detection (LOD) for F^- and S^2- ions was found to be 3.1 μM and 5.7 μM, respectively. For quantitative measurements, the paper test strips containing TAQH were successfully fabricated and applied to detect F^- and S^2- ions in aqueous solutions. Furthermore, Job's plot based on spectroscopic data showed one-to-one stoichiometry for the interaction of anions with probe TAQH. Therefore, the proposed chemosensor with excellent features like the cost-effective, high sensitively and selectively and short response times can be utilized in any physical and biological conditions.

An Efficient Probe of Cyclometallated Phosphorescent Iridium Complex for Selective Detection of Cyanide

A cyclometallated phosphorescent iridium-based probe to detect CN^- was prepared through a cyanide alcoholize reaction based on the C^N type main ligand and N^N type ancillary ligand (2-phenyl pyridine and 1,10-phenanthroline-5-carboxaldehyde, respectively). The efficient probe exhibited good sensitivity in response to CN^- in an CH₃CN and H₂O (95/5) mixture within a 1.23 μM detection limit. The response of PL is directly in line with the concentration of CN^- from 0 to 2.0 equiv. The PL investigation of other reactive anions proved the great selectivity to CN^-. Additionally, upon adding 1.0 equiv. of cyanide, the formation of cyanohydrin was correctly elucidated in ¹H NMR, FT-IR, and mass spectra studies. The conspicuous results indicate that the iridium complex has the potential possibility of application in other biosystems related to CN^-.

Cyclocondensation of coumarin-3-thioformates with 3-hydroxyoxindoles and 3-aminooxindoles for the synthesis of spiro-fused pentaheterocyclic compounds

A range of spiro-fused pentaheterocyclic compounds including spiro-butyrolactoneoxindole[3,4-c]coumarins and spiro-butyrolactamoxindole[3,4-c]coumarins were smoothly obtained via tandem Michael addition-lactonization/lactamization process.

Novel cyanide supramolecular fluorescent chemosensor constructed from a quinoline hydrazone functionalized-pillar[5]arene

Herein, we report a simple and novel approach for the design of fluorescent chemosensor through the self-assembly of functionalized monomer molecules. According to these approach, a novel supramolecular fluorescent chemosensor (SPMS) was successfully constructed by self-assembly of a quinoline hydrazone functionalized pillar[5]arene monomer PM. Interestingly, upon the addition of CN^-, the solution of SPMS instantly shows dramatic fluorescent enhancement and emitting bright blue emission. Meanwhile, the fluorescence quantum yields show distinct increase from 0.0582 of SPMS to 0.3952 of SPMS + CN^-. The detection limit (LOD) of SPMS for CN^- is 9.70 × 10^-8 M, which indicated high sensitivity. Moreover, the SPMS is selective for CN^- even in the presence of other anions, the fluorescent detection process of SPMS for CN^- was not interfered by other competitive anions (F^-, Cl^-, Br^-, I^-, N₃^-, OH^-, SCN^-, HSO₄^-, AcO^-, H₂PO₄^- and ClO₄^-). Notably, in the CN^- sensing process, the self-assembly structure of the supramolecular chemosensor SPMS didn't show any disassembly. This work provides a novel approach for instant detection of CN^- through a self-assembled supramolecular fluorescent chemosensor in aqueous system. Moreover, the test strips based on SPMS were fabricated, which could serve as convenient and efficient CN^- test kits.

A dual-responsive fluorescent probe for detection of fluoride ion and hydrazine based on test strips

Hydrazine (N₂H₄) and fluoride ion (F^-) are regarded as environmental pollutants and potential carcinogens. A dual-functional fluorescent probe (probe 1) was developed for both F^- and N₂H₄ with high selectivity and sensitivity. 1 was based on nucleophilic aromatic substitution reaction for N₂H₄ detection and selective cleavage of 4-nitrobenzenesulphonyl group for the determination of F^-. The limits of detection of probe for F^- and N₂H₄ were 77.82 nM and 29.34 nM, respectively, which are far below the threshold limit value (TLV) of United States Environmental Protection Agency (EPA). The home-made test strips of 1 provided the positive tool for F^- and gaseous N₂H₄ in different system. And the confocal fluorescence images indicated that 1 can quantitatively detect N₂H₄ in living PC12 cells. Promisingly, 1 has great prospects for N₂H₄ imaging and determining in living system.

A colorimetric and ratiometric fluorescent probe for cyanide sensing in aqueous media and live cells

A mitochondria-targeting ratiometric fluorescent probe for cyanide was reported.

Cyanide and biothiols recognition properties of a coumarin chalcone compound as red fluorescent probe

A novel coumarin chalcone derivative 1 was designed, synthesized and characterized by nuclear magnetic resonance spectra and high resolution mass spectrum. The photophysical and recognition properties of the compound as red fluorescent probe for cyanide and biothiols including cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) have been discussed systematically. Red fluorescence probe 1 was able to achieve rapid and selective identification for cyanide anion and biothiols in aqueous solutions with red fluorescence quench. In addition, the recognition mechanism of 1 was demonstrated by in situ ¹H NMR. The compound has two potential nucleophilic sensing sites including carbon-carbon double bond and 4-position of coumarin. The results indicate that cyanide anions can be bonded to these two sites to afford 2:1 bonding product. But biothiols only are bonded to carbon-carbon double bond by Michael addition reaction. The bonding of both cyanide and biothiols to the probe disrupts intramolecular charge transfer and leads to fluorescence quench.

Oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor: Sensing ability, TD-DFT calculations and its application as an efficient solid state sensor

An oligothiophene-based colorimetric and ratiometric fluorescence dual-channel cyanide chemosensor 3 T-2CN was reported. Sensor 3 T-2CN showed both naked-eye recognition and ratiometric fluorescence response for CN^- with an excellent selectivity and high sensitivity. The sensing mechanism based on the nucleophilic attack of CN^- on the vinyl CC bond has been successfully confirmed by the optical measurements, ¹H NMR titration, FT-IR spectra as well as the DFT/TD-DFT calculations. Moreover, the detection limit was calculated to be 0.19μM, which is much lower than the maximum permission concentration in drinking water (1.9μM). Importantly, test strips (filter paper and TLC plates) containing 3 T-2CN were fabricated, which could act as a practical and efficient solid state optical sensor for CN^- in field measurements.

Sensitive fluorescence on-off probes for the fast detection of a chemical warfare agent mimic

Two highly sensitive probes bearing a nucleophilic imine moiety have been utilized for the selective detection of chemical warfare agent (CWA) mimics. Diethyl chlorophosphate (DCP) was used as mimic CWAs. Both iminocoumarin-benzothiazole-based probes not only demonstrated a remarkable fluorescence ON-OFF response and good recognition, but also exhibited fast response times (10s) along with color changes upon addition of DCP. Limits of detection for the two sensors 1 and 2 were calculated as 0.065μM and 0.21μM, respectively, which are much lower than most other reported probes. These two probes not only show high sensitivity and selectivity in solution, but can also be applied for the recognition of DCP in the gas state, with significant color changes easily observed by the naked eye.

A cyanide-triggered hydrogen-bond-breaking deprotonation mechanism: fluorescent detection of cyanide using a thioacetohydrazone-functionalized bispillar[5]arene

Bispillar[5]arene-based fluorescent sensor was used for fluorescent detection of cyanide anions through deprotonation accompanied by intermolecular hydrogen bond breakage.

A novel water soluble pillar[5]arene and phenazine derivative self-assembled pseudorotaxane sensor for the selective detection of Hg2+ and Ag+ with high selectivity and sensitivity

A bifunctional supramolecular pseudorotaxane chemosensor (G-WAP) based on pillar[5]arene and phenazine imidazole was constructed, which could detect Hg²⁺ and Ag⁺ in water.

Sequential Detection of CN- and HSO4- Anions in an Aqueous Environment Utilizing a New Colorimetric Azoimine Receptor: Mimicking Logic Gate Behaviour and a Security Keypad Lock

A new isonicotiamide-based azoimine receptor has been successfully devised and synthesised for dual-recognition of CN− and HSO4− anions in aqueous media (3 : 2 DMSO–water solution). The devised azomethine probe detected lethal cyanide ions under UV-vis spectroscopy through the rapid appearance of an orange colour. More importantly, the colour and spectroscopic changes of the devised chemosensor could be revived upon the addition of HSO4− to the sensor containing cyanide ions. Furthermore, other surveyed anions failed to induce a similar response. Interestingly, based on changes in absorption intensity at a particular wavelength in the presence of two aforementioned anions, as two chemical inputs, an INHIBIT logic gate has been elaborated. Moreover, the reversibility of the sensory system provided an opportunity to present a sequential logic circuit at a molecular level. In accession, the target chemosensor could operate as a molecular keypad lock with sequential chemical inputs of CN− and HSO4− anions.

Fluorescent probes for the simultaneous detection of multiple analytes in biology

This review identifies and discusses fluorescent sensors that are capable of simultaneously reporting on the presence of two analytes for biological application.

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

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.

Detection of cyanide ions in aqueous solutions using cost effective colorimetric sensor

Cyanide (CN̄) is one of the most toxic material to the human and environment. It is very important to develop the diagnostic tools for the detection of CN̄ ions. Moreover, detection of the ions in an aqueous medium is a challenging task as water molecules interfere with the sensing mechanism. In this context, we prepared chemical sensor, S1, having anthraquinone as a signaling unit and thiourea as a binding site. This sensor exhibited distinct visual color and spectral changes in response to CN̄ ion over other testing anions in 50% aq. DMSO solution. However, in 20% aq. DMSO solution, S1 exhibited obvious spectral and color changes in response to CN̄, fluoride (F̄), acetate (Ac̄) and benzoate (Bz̄). Another sensor, S2, having a same signaling unit with that of S1, but a different binding site of urea group. In contrast to S1, S2 exhibited obvious spectral and color changes to F̄ in 2.5% aq. DMSO solution. NMR titration results suggested that the spectral and colorimetric responses were due to the formation of host-guest complex and deprotonation events. Finally, economically viable paper-based colorimetric "test stripes" of S1 were fabricated to detect the CN̄ ions in 100% aqueous solution.

Multi-ion detection and molecular switching behaviour of reversible dual fluorescent sensor

The selective chemosensing behaviour of imidazole bisthiocarbohydrazone (IBTC) towards F^- and Cu²⁺ are studied via colorimetric, UV-Visible, fluorescence spectra studies, and binding constants were calculated. The ¹H NMR titration study strongly support that the deprotonation of IBTC followed by the hydrogen bond formation via N1H1 and N2H2 protons with fluoride ion. The fluorescence inactive IBTC-Cu complex became fluorescence active in the presence of perchlorate (ClO₄^-) ion. The selective detection of perchlorate ion was also explained. The F^- sensing mechanism of IBTC has been investigated by Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT) methods. The theoretical outcomes well reproduce the experimental results. And it concluded the NH protons, nearby the imine group was first captured by the added F^- ion and then deprotonation happened followed by the formation of hydrogen bond. The IBTC found good reversibility character with the alternative addition of Ca²⁺ and F^-. The multi-ion detection of IBTC was used to construct the NOR, OR and INHIBITION molecular logic gates.

How explosive TNP interacts with a small tritopic receptor: a combined crystallographic and thermodynamic approach

The interaction of explosive and pollutant TNP with the host receptor has been thoroughly explained and characterized by SCXRD and thermodynamic parameters.

Positional isomeric chemosensors: fluorescent and colorimetric cyanide detection based on Si–O cleavage

Highly selective and sensitive fluorescent and colorimetric cis/trans isomers 3 were rationally designed and investigated for the fast detection and visualization of cyanide ions (TBACN and NaCN) via CN-promoted Si–O cleavage in aqueous solution and in the solid state.