Rational Design of an ICT-Based Chemodosimeter with Aggregation-Induced Emission for Colorimetric and Ratiometric Fluorescent Detection of Cyanide in a Wide pH Range

Fluorometric and colorimetric sensor for selective detection of cyanide anion by dibenzosuberenone-based dihydropyridazine in aqueous solution

A new chemosensory based on deprotonation and intramolecular charge transfer (ICT) was developed to detect cyanide in food samples. Deprotonation was facilitated by increasing the acidity of the NH proton in the dibenzosuberenone-based dihydropyridazine chemosensor Pz3 with -CN substituents. Addition of cyanide to acetonitrile and aqueous acetonitrile solution (1/9) of Pz3 resulted in their significant color change from colorless to purple in visible light, accompanied by a strong red shift in the absorption spectrum. Meanwhile, the near-infrared (NIR) emission (ex. 525 nm, em. 670 nm) of Pz3- resulting from deprotonation showed fluorescence switching behavior to detect the cyanide anion. While the acidic NH protons interact with basic anions as F-, CN-, OAc- and H2PO4- in organic solution (MeCN), just CN ions interact with in aqueous organic solutions (H2O-MeCN 1/9 HEPES pH 7.4). The limit of detection of cyanide from the fluorescence spectrum is 80 nM, which is well below the value determined for drinking water by World Health Organization (WHO). The interference effect of cations and anions showed that Pz3 could play an important role in the determination of waste NaCN. In addition, Pz3 successfully carried out the selective detection of cyanide in food samples such as bitter almonds and sprouting potatoes.

Selective and Effective Sensing of Cyanide Ion with no Interference in Water by Phenothiazine-indolium Fused Optical Sensor

The sensor with electron donor phenothiazine-2-carbaldehyde and electron acceptor indolium carboxylic acid, is developed with an intramolecular charge transfer transition between them. The synthesized molecule senses cyanide ion in water. The cyanide ion reacts with the molecule via nucleophilic addition in the indolium ring with a noticeable purple to colorless change in the solution observed. Also with the cyanide ion interaction, the sensor exhibits change in UV-visible absorption and fluorescence spectra. While the other ion does not show spectral and visual changes when interacts with the sensor molecule. Also the interference study reveals that the molecule is highly selective towards cyanide ion. Different source of water samples confirms the CN- ion sensing efficiency of the molecule. 1:1 interaction between the molecule PTI and cyanide ion is confirmed from the results of Jobs plot, 1H NMR and HRMS. Paper strips were prepared and this can act as a simple tool to sense cyanide ion in various water samples.

Aggregation-induced emission activity of sensor TBM-C1 hybrid of methoxy-triphenylamine (OMe-TPA) and dicyanovinyl for cyanide detection in aqueous THF: Mechanistic insights and potential applications

A series fluorescent probes (TBM-Cx (x = 1, 4, 8)) were designed based on embedding various alkoxy chains on the electron donor of triphenylamine (TPA)-based dicyanovinyl (MT) compound with an electron-deficient benzothiadiazole (BTD) for sensitive, selective, and visualizing detection of cyanide in aqueous solution. Due to the nucleophilic addition of CN-, the intramolecular charge transfer (ICT) of these probes was inhibited by the destroyed conjugated structure, exhibiting excellent "turn-on" fluorescence response toward cyanide anion (CN-) in tetrahydrofuran (THF). However, the alkoxy chains with different lengths embedded in TPA not only enhance the sensitivity and solubility, but also regulate the emission behavior from ICT to aggregation-induced emission (AIE) characteristics. The binding mechanism and AIE sensing performances between the probes and CN- have been investigated and compared in THF/water mixture by spectral tools and theoretical calculations. The results showed that the ICT-based TBM-C1 probe with methoxy chain showed significantly turn-on fluorescence response to CN- as low as 0.077 μM in THF/water solution at high water fraction (90 %). Due to the AIE sensing process, TBM-C1 was successfully employed to determine CN- in food and water samples, image CN- in living cells and BALB/c mice, and prepare test kits for visualizing cyanide.

Multi-Spectroscopic and TD-DFT Studies on Chromogenic and Fluorogenic Detection of Cyanide in an Aqueous Solution

Different spectroscopic techniques and Density Functional Theory (DFT)/Time-Dependent Density Functional Theory (TDDFT) calculations have been employed to investigate the dual channel CN- detection behaviour of the developed chemo-dosimeter (AK3). The CN- with AK3 reaction triggered a colour change from pale yellow to colourless and enhanced fluorescence. UV-Vis, fluorescence, 1H & 13C NMR and mass techniques coupled with theoretical calculations (Mulliken charges, dihedral angles) revealed that the CN- sensing process mechanism involves deprotonation of the N-H group followed by nucleophilic addition reaction. Detailed TD-DFT calculations showed that the relaxation of excited electrons from LUMO and to two different ground states is responsible for the weak/moderate fluorescence of AK3. Nucleophilic addition of CN- to the C-atom of the CH = CH bridge terminated the π-conjugation between donor and acceptor regions, reduced the coplanarity, decreased the ICT transition and consequently enhanced the fluorescence of the probe. The practical utility of the probe was demonstrated by detecting cyanide in food materials and determining CN- in environmental water samples.

AIE active luminous dye with a triphenylamine attached benzothiazole core as a portable polymer film for sensitively detecting CN- ions in food samples

Aggregation-induced emission (AIE) active 3-(3-(benzo[d]thiazol-2-yl)-2-hydroxyphenyl)-2-(4'-(diphenylamino)-[1,1'-biphenyl]-4-yl)acrylonitrile (BTPA) has been designed and synthesized herein, with the goal of detecting CN^- ions at a low-level in semi-aqueous medium. The deliberate addition of the electron-deficient alkene BTPA increased its sensitivity and selectivity to CN^- ions, with a better detection limit of 6.4 nM, unveiling the next-generation approach to creating sophisticated CN^- ions selective chemosensors. The ESI-MS and NMR spectra analyses provided strong support for the structures of the chemosensors, while the UV-Vis, photoluminescence, and ¹H-NMR titration experiments provided support for the sensing efficiencies. Subsequently, PVDF/BTPA electrospun nanofibers have been effectively produced as functional films. These nanofiber films exhibit outstanding mechanical strength, photo/thermal stability, and optical responsiveness to CN^- ions, making them a potential choice for on-field emerging contaminant detection.

A colorimetric and turn-on fluorescent sensor for cyanide and acetate-based Schiff base compound of 2,2'-((1E,11E)-5,8-dioxa-2,11-diazadodeca-1,11-diene-1,12-diyl)bis(4-((E)-phenyldiazenyl)phenol)

A novel Schiff base-based sensor (L) has been designed, synthesized, and developed as a fluorescent and colorimetric sensor for cyanide and acetate. This L exhibited a quick response with rapid sensitivity to CN^- and AcO^- through a remarkable color change from yellow to red which was detectable by the naked eyes. It also sensed CN^- and AcO^- in a fluorescent way via an enhancement in fluorescence intensity. The interaction between L and anions (CN^- and AcO^-) was investigated by using UV-Vis studies, and ¹H NMR titration. The theoretical DFT calculations were also employed to support the results, which displayed good agreement with the experimental value acquisition. As the detection limit for cyanide and acetate were 2.1 × 10^-9 M and 1.7 × 10^-9 M; respectively, low concentrations of these anions could be detectable in the proposed L sensor. In addition, L showed significant reversibility of CN^- detection by using Cu²⁺ as a proper reagent with two different sensing methods including color change and UV-Vis. Last but not least, L could be applied to rapidly detect CN^- in a wide range of pH. As a result, the proposed sensor is promising to identify cyanide and acetate in practical applications in medical, biological, and chemical fields.

Selective visualization of cyanide in food, living cells and zebrafish by a mitochondria targeted NIR-emitting fluorescent probe

Cyanide is a highly toxic substance, and the detection of cyanide in the environment and food samples is critical to public health care. Herein, we rationally designed a mitochondria-targeted near-infrared fluorescent probe BTC for ratiometric monitoring of CN^- in water, food, living cells, and zebrafish. BTC exhibits a remarkable colorimetric ratiometric fluorescence response to CN^- with high selectivity, low detection limit (54.3 nM), and large Stokes shift. The cyanide sensing mechanism was demonstrated by NMR and ESI-MS analysis and density functional theory (DFT). More importantly, BTC was used for efficient naked-eye colorimetric detection of CN^- in sprouting potatoes, almonds, and ginkgo fruit samples. Further, the BTC is capable of situ tracking and imaging cyanide in mitochondria of SMMC-7721 cells and in zebrafish via dual emission channels, and was prepared into a kit for convenient and visual on-site sensing of cyanide in food samples.

A ratiometric fluorescent probe for selective detection of thiophenol derivatives

Though a number of on-off or off-on fluorescent probes have been developed for the detection of thiophenol by using its unique recognition groups, such as 2, 4-dinitrophenyl ether, 2, 4-dinitrophenyl sulfonamide, and 2, 4-dinitrophenyl sulfonate, up to now, there are few probes that can detect thiophenol by the proportional fluorescence signal. We developed a ratiometric fluorescent probe with coumarin pyridine derivative as fluorophore and 2, 4-dinitrophenyl ether moiety as the sensing unit which could be used to detect thiophenol derivatives by the aromatic nucleophilic substitution reaction. This probe (CPBPN) displayed significant change in fluorescence ratio (256 fold) to result in a more reliable analysis by self-calibration and a relatively low detection limit of 24 nM toward 4-methylthiophenol (MTP) within 30 min to achieve more sensitivity. Besides, the probe was also applied to detect the presence of thiophenol derivatives in actual water samples and fluorescence imaging in living cells. The present work is of great importance for monitoring environmental pollutants and studying their biological function.

Lighting up hydrogen peroxide in living cells by a novel quinoxalinamine based fluorescent probe

Hydrogen peroxide (H₂O₂), a member of small-molecule reactive oxygen species (ROS), plays vital roles in normal physiological activities and the occurrence of many diseases. In this work, two off-on fluorescent probes, QX8A-H₂O₂ and QX9A-H₂O₂, were firstly designed for H₂O₂ detection with novel fused quinoxalines as the fluorophores and boronate moiety as the reaction sites. By comparing the optical properties, QX9A-H₂O₂ with better performance was selected for further studies. QX9A-H₂O₂ exhibited a high sensitivity to H₂O₂ with the detection limit as low as 46 nM, and displayed a good selectivity towards H₂O₂ over other reactants such as ROS, biothiols and various ions. The detection was based on the intramolecular charge transfer (ICT), proceeding through a sequential oxidative hydrolysis, 1,6-rearrangement elimination and decarboxylation process to release the fluorophore QX9A. Moreover, probe QX9A-H₂O₂ was cell permeable and was successfully employed in both exogenous and endogenous H₂O₂ imaging in living cells.

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)...

Idiosyncratic recognition of Zn2+ and CN- using Pyrazolyl-Hydroxy-Coumarin scaffold and live cell imaging: Depiction of Luminescent Zn(II)-Metallocryptand

Multi-responsive sensitive and selective sensor design is one of the stimulating researches in sensor field. We have designed a pyrazolyl-hydroxy-coumarin scaffold, 7-hydroxy-4-methyl-8-(((5-phenyl-1H-pyrazol-3-yl)imino)methyl)-2H-chromen-2-one (H2L) and characterized by spectroscopic data (1H-NMR,13C-NMR, ESI-MS,...

Discovery of a highly selective and ultra-sensitive colorimetric fluorescent probe for malononitrile and its applications in living cells and zebrafish

A selective and ultra-sensitive colorimetric fluorescent probe was discovered to detect malononitrile in living cells and zebrafish.

A bisspiropyran fluorescent probe for the selective and rapid detection of cyanide anion in liqueurs

A novel bisspiropyran-fluorescent probe was synthesized and applied in the selective and rapid CN− detection in liqueurs.

Cucurbit[8]uril-Assisted Nucleophilic Reaction: A Unique Supramolecular Approach for Cyanide Detection and Removal from Aqueous Solution

A unique supramolecular approach of preparing and using a cucurbit[8]uril (Q[8])-based dynamic host-guest assembly for cyanide sensing in and removal from water has been successfully developed. The dicyanovinyl-attached cationic guest (1) was designed as the fluorescent response moiety for the detection of the cyanide anion via a nucleophilic addition reaction in the assist of the Q[8]-based 2:2 quaternary complexes. Furthermore, the reaction of cyanide with 1 further switched the Q[8]-based host-guest assemblies from the 2:2 complexes to the 1:1 supramolecular polymers that precipitate in water. Thus, the macrocyclic-based dynamic host-guest assembly has potential use in applications for solving the problem of toxic anion pollutants present in aqueous environments.

Involvement of a unique chemodosimeter in the selective estimation of noxious cyanide in common water hyacinth (Eichhornia crassipes): an environmental refinement

A naphthaldehyde-pyridoxal conjugated chemodosimeter (NPLC) was developed and employed for the sensitive and selective detection and estimation of cyanide in common water hyacinth (Eichhornia crassipes), a free floating macrophyte used in the phytoremediation process since ancient times. The non-fluorescent nature of the probe NPLC, directed by the possibility of excited state intramolecular proton transfer process (ESIPT), was promptly changed due to CN^- induced di-deprotonation of the probe. The naked eye color change and turn on vivid fluorescent color of NPLC was attributed to the inhibition of the ESIPT mechanism in the deprotonated NPLC (NPLC-D). The selective detection of cyanide ion in the nanomolar range (81 nM), among other interfering anions, makes it exclusive. The involvement of the probe in a chemodosimetric fashion toward cyanide was elucidated by experimental and computational studies.

Silica covering driven intensity enhancement and handedness inversion of the CPL signals of the supramolecular assemblies

Dipeptide-based hybrid materials with enhanced and inversed circularly polarized luminescence signals were fabricated through a dynamic supramolecular templating approach.