A novel ratiometric near-infrared fluorescent probe for monitoring cyanide in food samples

An affordable, field-deployable detecting system for cyanide ion - Investigating applications in real time uses

A highly efficient system that incorporates the instantaneous visualization of the cyanide ion in water was synthesized by keeping the fluorophore system (electron donor) as a julolidine-coumarin conjugate and changing the electron acceptor unit. The probes exhibit a notable color change in normal and UV light. The probe interaction modalities are based on the ICT process. With a detection limit in the nM range, it may preferentially react with cyanide, which is less than the tolerable level of 1.9 μM. According to 1H NMR data, the probes detect cyanide ions by nucleophilic addition reaction mechanism. Furthermore, current probe successfully determines real resources, including cyanide containing cassava powder, sprouted potatoes and various water samples. Besides the test strips, an electronic Arduino device was also employed to detect the cyanide ion. As such, the developed probes exhibit outstanding practical application with respect to the cyanide ion.

D-π-A type fluorescent dyes: Effect of π-bridge units on optical and G4 DNA binding properties

Fluorescent solvatochromic dyes that are sensitive to the nature of local microenvironmental, have been explored as probes in applications ranging from the imaging biomolecules to understanding of basic biomolecule functions. To expand the scope of fluorescent solvatochromic dyes for G-quadruplex (G4) DNA structures, and to illustrate the relationship between structure and properties, three newly designed D-π-A type fluorescent dyes were synthesized by introducing diarylimidazole to carbazole skeleton linked to benzene, furan or thiophene π-conjugated bridge and connected with pyridinium acceptor, respectively. Their structural characteristics, optical properties, and G4 DNA binding properties were discussed in detail. In general, the incorporation of furan and thiophene as π-conjugated bridges leads the better conjugation and molecular coplanarity with more efficient intramolecular charge transfer (ICT) effect compared with benzene bridge. The fluorescence intensities induced upon interaction were found that TP-6 with thiophene π-conjugated bridge had the strongest response toward G4 DNAs. In addition, the application of this dye as a fluorescent agent for living cell imaging was also demonstrated.

Recent advances in photoluminescent fluorescent probe technology for food flavor compounds analysis

The real-time, precise qualitative and quantitative sensing of food flavor compounds is crucial for ensuring food safety, quality, and consumer acceptance. As indicators for food flavor labeling, it is vital to delve deep into the specific ingredient and content of food flavor compounds to assess the food flavor quality, but still facing huge challenges. Photoluminescent fluorescent probe technology, with fast detection and high sensitivity, has shown immense potentials in detecting food flavor compounds. In this review, the classification and optical sensing mechanism of photoluminescent fluorescent probe technology are described in detail. Besides, challenges in applying photoluminescent fluorescent probe technology to analyze food flavor compounds are outlined to indicate future research directions. We hope this review can provide an insight for the applications of photoluminescent fluorescent probe technology in the evaluation of food flavor quality in future.

Nanozyme catalysis pressure-powered intuitive distance variation for portable quantitative detection of H2S with the naked eye

As a representative gas of food spoilage, the development of rapid hydrogen sulfide (H2S) analysis strategies for food safety control is in great demand. Despite traditional methods for H2S detection possessing great achievements, they are still incapable of meeting the requirement of portability and quantitative detection at the same time. Herein, a nanozyme catalysis pressure-powered sensing platform that enables visual quantification with the naked eye is proposed. In this methodology, Pt nanozyme inherits the catalase-like activity to facilitate the decomposition of H2O2 to O2, which can significantly improve the pressure in the closed container, further pushing the movement of indicator dye. Furthermore, H2S was found to effectively inhibit the catalytic activity of Pt nanozyme, indicating that the catalase-like activity of PtNPs may be regulated by varying concentrations of H2S. Therefore, by utilizing a self-designed pressure-powered microchannel device, the concentration of H2S was successfully converted into a distinct signal variation in distance. The effectiveness of the as-designed sensor in assessing the spoilage of red wine by H2S determination has been demonstrated. It exhibits a strong correlation between the change in dye distance and H2S concentration within the range of 1-250 μM, with a detection limit of 0.17 μM. This method is advantageous as it enhances the quantitative detection of H2S with the naked eye based on the portable pressure-powered sensing platform, as compared to traditional H2S biosensors. Such a pressure-powered distance variation platform would greatly broaden the application of H2S-based detection in food spoilage management.

Ratiometric detection and monitoring of cyanide in biological, environmental and food samples by a novel triphenylamine-xhantane based fluorescent probe

BACKGROUND

As cyanide (CN-) is a significant hazard to the environment and human health, it is essential to monitor cyanide levels in water and food samples. Moreover, real-time visualization of CN-could provide an additional understanding of its critical physiological and toxicological roles in living cells. The fluorescence approach based on small organic probes is an effective way for the detection of CN-. In this approach, a triphenylamine-xhantane conjugate was applied to detect in many samples such as sewage water, soil, sprouted potato, apricot seed, and living cells.

RESULTS

We report a new ratiometric near-infrared fluorescent probe based on a triphenylamine-xhantane derivative for CN-sensing in many samples. The probe displays high selectivity for only CN- ions among a series of analytes. The addition of cyanide to the dicyanovinyl moiety of the probe disrupts π-conjugation followed by the interruption of internal charge transfer. Consequently, the emission peak of the probe shifts hypsochromically from 655 to 495 nm. There is a linear correlation between the emission intensity (I495) and cyanide level, with a detection limit of 0.036 μM. The probe has many advantages over many probes, such as NIR fluorescence, ratiometric response, low cytotoxicity (85.0 % cell viability up to 50.0 μM of the probe), good membrane permeability, fast response time (4.0 min), high selectivity, good photostability, and anti-interference capability.

SIGNIFICANCE

Although various probes have been reported in the literature, the use of triphenylamine-xhantane unit as CN- probe has yet to be explored. The probe can detect trace levels of cyanide in many samples such as sewage water, soil, sprouted potatoes, and apricot seeds. Furthermore, it is successfully utilized for the ratiometric fluorescent bioimaging of cyanide in living cells.

A ferrocene-based chemo-dosimeter for colorimetric and electrochemical detection of cyanide and its estimation in cassava flour

A simple chemo-dosimeter VDP2 bearing a ferrocene moiety was designed, synthesized, and characterized, and exhibited both chromogenic and electrochemical responses selectively for CN- in H2O-DMSO (9 : 1, v/v) medium. The probe VDP2 showed an instantaneous color change from colorless to yellow with CN- that can readily be observed visually. The deprotonation of the benzimidazole -NH, followed by nucleophilic addition of CN- to the olefinic C-atom, as evidenced by 1H and 13C NMR titration experiments, caused the colorimetric and electrochemical responses. The mass spectral study, CV, FTIR and Mulliken charges computed well supported the proposed mechanism. The electrochemical limit of detection was calculated to be 72 nM. The results of DFT and TD-DFT calculations suggested that the colorless nature of the probe VDP2 is due to weak intramolecular charge transfer (ICT) transition and the yellow color of the VDP2+CN adduct is due to through-space ICT transition. Above all, the probe could be an ideal candidate for monitoring cyanide in water samples and cassava flour with practical significance. A simple and convenient colorimetric method was developed to determine cyanide content in cassava flour.

Visual detection and discrimination of nerve and blood agents using a dual-site fluorescent probe in living cells and mice

Of all chemical warfare agents (CWAs), only nerve and blood agents cause massive mortality at low concentrations. To better detect and discriminate nerve and blood agents, a reliable detection method is desirable. We report a series of fluorescent probes for nerve and blood agent detection. Among the tested probes, SR-Pip detected nerve and blood agents quickly (within 10 s for nerve agents and 1 min for blood agents). SR-Pip coupled with nerve agent produced a weak orange fluorescence with good sensitivity [limit of detection (LOD)= 5.5 μM]. Upon reaction with blood agent, the fluorescence of SR-Pip changed from orange fluorescence to blue fluorescence with detection limits as low as 9.6 nM. This probe effectively visualised different concentrations of nerve agents in living cells and mice. A portable test kit using SR-Pip instantly detected nerve and blood agents. To the best of our knowledge, SR-Pip is the first fluorescent probe for nerve and blood agent detection.

Construction of a Colorimetric and Near-Infrared Ratiometric Fluorescent Sensor and Portable Sensing System for On-Site Quantitative Measurement of Sulfite in Food

Sulfites play imperative roles in food crops and food products, serving as sulfur nutrients for food crops and as food additives in various foods. It is necessary to develop an effective method for the on-site quantification of sulfites in food samples. Here, 7-(diethylamino) quinoline is used as a fluorescent group and electron donor, alongside the pyridinium salt group as an electron acceptor and the C=C bond as the sulfite-specific recognition group. We present a novel fluorescent sensor based on a mechanism that modulates the efficiency of intramolecular charge transfer (ICT), CY, for on-site quantitative measurement of sulfite in food. The fluorescent sensor itself exhibited fluorescence in the near-infrared light (NIR) region, effectively minimizing the interference of background fluorescence in food samples. Upon exposure to sulfite, the sensor CY displayed a ratiometric fluorescence response (I447/I692) with a high sensitivity (LOD = 0.061 μM), enabling accurate quantitative measurements in complex food environments. Moreover, sensor CY also displayed a colorimetric response to sulfite, making sensor CY measure sulfite in both fluorescence and colorimetric dual-signal modes. Sensor CY has been utilized for quantitatively measuring sulfite in red wine and sugar with recoveries between 99.65% and 101.90%, and the RSD was below 4.0%. The sulfite concentrations in live cells and zebrafish were also monitored via fluorescence imaging. Moreover, the sulfite assimilated by lettuce leaves was monitored, and the results demonstrated that excessive sulfite in leaf tissue could lead to leaf tissue damage. In addition, the sulfate-transformed sulfite in lettuce stem tissue was tracked, providing valuable insights for evaluating sulfur nutrients in food crops. More importantly, to accomplish the on-site quantitative measurement of sulfite in food samples, a portable sensing system was prepared. Sensor CY and the portable sensing system were successfully used for the on-site quantitative measurement of sulfite in food.

Dual channel chemosensor for successive detection of environmentally toxic Pd2+ and CN- ions and its application to cancer cell imaging

BACKGROUND

Detecting and neutralizing Pd2+ ions are a significant challenge due to their cytotoxicity, even at low concentrations. To address this issue, various chemosensors have been designed for advanced detection systems, offering simplicity and the potential to differentiate signals from different analytes. Nonetheless, these chemosensors often suffer from limited emission response and complex synthesis procedures. As a result, the tracking and quantification of residual palladium in biological systems and environments remain challenging tasks, with only a few chemosensing probes available for commercial use.

RESULTS

In this paper, a straightforward approach for the selective detection of Pd2+ ions is proposed, which involves the design, synthesis, and utilization of a propargylated naphthalene-derived probe (E)-N'-((2-(prop-2-yn-1-yloxy)naphthalen-1-yl)methylene)benzohydrazide (NHP). The NHP probe exhibits sensitive dual-channel colorimetry and fluorescence Pd2+ detection over other tested metal ions. The detection process is performed through a catalytic depropargylation reaction, followed by an excited state intramolecular proton transfer (ESIPT) process, the detection limit is as low as 11.58 × 10-7 M under mild conditions. Interestingly, the resultant chemodosimeter adduct (E)-N'-((2-hydroxynaphthalen-1-yl)methylene)benzohydrazide (NHH) was employed for the consecutive detection of CN- ions, exhibiting an impressive detection limit of 31.79 × 10-8 M. Validation of both detection processes was achieved through 1H nuclear magnetic resonance and density functional theory calculations. For real-time applications of the NHP and NHH probes, smartphone-assisted detection, and intracellular detection of Pd2+ and CN- ions within HeLa cells were studied.

SIGNIFICANCE

This research presents a novel naphthalene derivative for visually detecting environmentally toxic Pd2+ and CN- ions. The synthesized probe selectively binds to Pd2+, forming a chemodosimeter. It successfully detects CN- ions through colorimetry and fluorimetry, offering a low detection limit and quick response. Notably, it's the first naphthalene-based small molecule to serve as a dual probe for toxic analytes - palladium and cyanide. Moreover, it effectively detects Pd2+ and CN- intracellularly in cancer cells.

A practical chromogenic and fluorogenic dual-mode sensing platform for rapid quantification of sulfite in food

Sulfur dioxide (SO2) and its derivatives (HSO3- and SO32-) are widely used in food-processing. Whereas excessive consumption of sulfur dioxide and its derivatives (>0.70 mg·kg-1day-1) severely endangers human health. In this work, we rationally constructed a practical dual-mode probe (dicyanomethylene)-1-methyl-1,4-dihydroquinolin-2-yl)vinyl)-1-methylquinolinium (QMN), which underwent a specific 1, 4-Michael addition with sulfite to afford a noticeable color change from pale yellow to red along with a high-contrast fluorescence turn-on response at 598 nm. QMN has the advantages of rapid response, high signal-to-noise ratio, excellent selectivity, good water-solubility, large Stokes shift and low detection limit (LOD = 31.9 nM). QMN has been successfully used to on-site visually determine sulfite in a diversity of foods with satisfactory recoveries (91.33-111.33 %) and high accuracy (93.74-98.71 %). Furthermore, a portable smartphone-based fluorescence sensing platform was fabricated for on-site determination of sulfite in food with good performance.

A reaction based carbazole-indolium conjugate probe for the selective detection of environmentally toxic ions

A nucleophilic addition based chemodosimeter was designed and synthesized with a carbazole donor and an indole acceptor. The addition of a cyanide ion to an electron-deficient indole moiety disrupts the acceptor-donor relationship, resulting in noticeable color shifts and spectrum differences in both the absorption and emission profiles. The design has a D-π-A molecular arrangement. Selectivity was investigated in 90% aqueous DMSO solution of probe CI with various anions such as SCN-, PF6-, NO3-, N3-, I-, HSO4-, CN-, H2PO4-, F-, HS-, ClO4-, Cl-, Br-, and AcO-. An intermolecular charge transfer (ICT) band at 506 nm in the UV-visible spectra vanished and the intensity of emission was quenched at 624 nm upon the addition of CN- ions. These outcomes demonstrate the effective nucleophilic addition of cyanide ions to the electron-deficient indole moiety of the probe, resulting in the formation of a new adduct in which the ICT transition is interrupted when π conjugation is blocked. The Job plot, 1H NMR spectroscopy, and HRMS analysis confirmed the formation of a new product. An outstanding response was shown by paper test strips made using probe molecules for the easy detection of cyanide ions in aqueous solutions. Besides, the probe selectively senses cyanide ions in different water samples.

Spectroscopic and Theoretical Studies on the Selective Detection of Cyanide Ions by a Turn-On Fluorescent Chemo-Dosimeter and its Application in Living Cell Imaging

A new chemo-dosimeter AK4 containing quinoline fluorophore has rationally been designed, synthesised and characterized using 1H and 13C NMR and mass spectral techniques. The probe senses explicitly CN- ion through a dramatic enhancement in fluorescence over other commonly coexistent anions in H2O:DMSO (9:1 v/v) medium over a broad pH range (4-10). 1H NMR titration revealed the deprotonation followed by nucleophilic addition reaction of CN-, which was supported by 13C NMR and mass spectral examinations. The Job's continuous variation method indicated the formation of a 1:1 adduct between AK4 and CN- with a binding constant of 1.62 × 104 M-1. A limit of detection (LOD) towards CN- of 0.69 µM has been determined, which is much lower than the World Health Organization (WHO) recommended limit of CN- in drinking water (1.9 µM). The changes in the optical properties of AK4 upon reaction with CN- were delineated using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) calculations. Moreover, fluorescence microscopic studies established that AK4 could be an effective probe for imaging intracellular CN- in HeLa cells.

The quality of beef in the conditions of the former Semipalatinsk Test Site

The territory of the Semipalatinsk Nuclear Test Site represents vast areas of grassy steppes, their use as pastures seems promising. The purpose of work was to compare beef samples obtained from settlements belonging to different categories of radiation risk: Kokpekty village, Chagan urban-type settlement, Krivinka village, Sarzhal village, three samples were examined from each settlement. Organoleptic analysis, radiometric determination of 137 Cs, was used as criteria. Also, an analysis of the amino acid composition by the high-performance liquid chromatograph method was carried out and a calculation of protein indicators was made: meat tenderness, amino acid usefulness, nutrition value. The organoleptic examination showed the compliance of all samples with the standards, with the exception of one sample from the Sarzhal village. The study of the specific activity of 137 Cs showed a direct correlation between the category of radiation risk and the content of this radioisotope in meat from different zones. The availability of some deviations in the samples indicators obtained from the Sarzhal village indicates the need to approach the products control from this zone more carefully, and radioisotope analysis should become a decisive criterion in determining the safety profile of the product.

Nanoscatterer-Assisted Fluorescence Amplification Technique

Weak fluorescence signals, which are important in research and applications, are often masked by the background. Different amplification techniques are actively investigated. Here, a broadband, geometry-independent and flexible feedback scheme based on the random scattering of dielectric nanoparticles allows the amplification of a fluorescence signal by partial trapping of the radiation within the sample volume. Amplification of up to a factor of 40 is experimentally demonstrated in ultrapure water with dispersed TiO2 nanoparticles (30 to 50 nm in diameter) and fluorescein dye at 200 μmol concentration (pumped with 5 ns long, 3 mJ laser pulses at 490 nm). The measurements show a measurable reduction in linewidth at the emission peak, indicating that feedback-induced stimulated emission contributes to the large gain observed.

Construction of a water-soluble fluorescent probe for copper (II) ion detection in live cells and food products

The quality of wine can be affected by excess Cu²⁺ due to the occurrence of oxidation reactions or precipitation. Therefore, it is essential to use simple and effective testing methods to ensure the Cu²⁺ content in wine. In this work, we designed and synthesized a rhodamine polymer fluorescent probe (PEG-R). The water solubility of PEG-R was improved by the introduction of polyethylene glycol, which improved the performance and broadened its application in the food field. The PEG-R was characterized by high sensitivity, selectivity and fast response to Cu²⁺ and was able to complete the response process within 30 s, with approximately 29-fold fluorescence enhancement of the probe after exposure to Cu²⁺, the limit of detection (LOD) was 1.295 × 10^-6 M. The probe can be used for the determination of Cu²⁺ in living cells, zebrafish, white wine and food products, and it was made into practical gels and test strips.

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.

Red-emitting fluorescent probe for hydrogen sulfide detection and its applications in food freshness determination and in vivo bioimaging

We report the development of a red-emitting fluorescence probe (XDS) for hydrogen sulfide (H₂S) detection in biosystems, real-world food samples, and application of this probe for monitoring of H₂S production during food spoilage. The XDS probe is developed by coupling of coumarin derivative to rhodanic-CN through a H₂S responsive CC bond. Remarkable fluorescence quenching of XDS is observed as a result of the response to H₂S. Semi-quantitative detection of H₂S in three real-world water and two beer samples and monitoring of H₂S production during food spoilage in real-time by "naked-eye" and smartphone colorimetric analysis are then achieved using XDS as the probe. Moreover, XDS is low toxicity, allowing it being used for visualizing endogenous and exogenous H₂S in vivo in a mouse model. It is expected that the successful development of XDS could provide an effective tool for investigating the roles of H₂S in biomedical system and for future food safety evaluation.

Cascade reaction-based highly sensitive fluorescent sensing systems applicable for dual-pattern fluorescence visualizing of thiophenol flavors in meat products and condiments

Thiophenols (ArSHs) are widely used as popular flavoring ingredients for making daily dishes. Dissecting the ArSHs contents in common foodstuffs is meaningful in the field of food safety science. Herein, a novel small-molecule sensor 2-(1H-benzo[d]imidazol-2-yl)-3-(2-(2,4-dinitrophenoxy)-4-morpholinophenyl)acrylonitrile (NOSA) has been tailored. The NOSA is able to respond to ArSHs, spontaneously yielding highly green-emissive fluorescent iminocoumarin (I₅₀₀). This cascade reaction-based strategy is sensitive (limit-of-detection = 2.8 nM), rapid (within 5 min), and selective toward ArSH flavors. Probe NOSA has been applied to the determination of ArSHs in real-life meat products and condiments. Moreover, a far-red fluorescent compound, 2-(7-(diethylamino)-4-(4-(methylthio)styryl)-2H-chromen-2-ylidene)malononitrile (CMMT), has been first combined with NOSA to construct a composite probe NOSA@CMMT for the ratiometric detection of ArSHs (I₅₀₀/I₆₃₀). System NOSA@CMMT exhibits a conspicuous fluorescence change from deep-red to light-green. Benefitted from the gorgeous chromatic fluctuation, a smartphone-integrated analysis platform is established for the real-time evaluation of ArSHs level.

Fluorescent probes for the detection of chemical warfare agents

Chemical warfare agents (CWAs) are toxic chemicals that have been intentionally developed for targeted and deadly use on humans. Although intended for military targets, the use of CWAs more often than not results in mass civilian casualties. To prevent further atrocities from occurring during conflicts, a global ban was implemented through the chemical weapons convention, with the aim of eliminating the development, stockpiling, and use of CWAs. Unfortunately, because of their relatively low cost, ease of manufacture and effectiveness on mass populations, CWAs still exist in today's world. CWAs have been used in several recent terrorist-related incidents and conflicts (e.g., Syria). Therefore, they continue to remain serious threats to public health and safety and to global peace and stability. Analytical methods that can accurately detect CWAs are essential to global security measures and for forensic analysis. Small molecule fluorescent probes have emerged as attractive chemical tools for CWA detection, due to their simplicity, ease of use, excellent selectivity and high sensitivity, as well as their ability to be translated into handheld devices. This includes the ability to non-invasively image CWA distribution within living systems (in vitro and in vivo) to permit in-depth evaluation of their biological interactions and allow potential identification of therapeutic countermeasures. In this review, we provide an overview of the various reported fluorescent probes that have been designed for the detection of CWAs. The mechanism for CWA detection, change in optical output and application for each fluorescent probe are described in detail. The limitations and challenges of currently developed fluorescent probes are discussed providing insight into the future development of this research area. We hope the information provided in this review will give readers a clear understanding of how to design a fluorescent probe for the detection of a specific CWA. We anticipate that this will advance our security systems and provide new tools for environmental and toxicology monitoring.

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.

Design of "turn-off" luminescent Ln-MOFs for sensitive detection of cyanide anions

Two novel 2D lanthanide metal-organic frameworks (Ln-MOFs), namely {[Eu₂(DBTA)₃(DMF)₂]·DMF}_n (1) and {[Tb₂(DBTA)₃(DMF)₂]·DMF}_n (2) (H₂DBTA = 2,5-dibromoterephthalic acid), have been successfully synthesized by the solvothermal method. Single-crystal X-ray diffraction results proved that the complexes possess the same topological structure of a (4²·6)₂(4²·8⁴)(4⁷·6³)₂-connected net. The recognition of CN^- from interfering anions with a low detection limit by "turn-off" luminescence makes them promising candidates for the highly selective and sensitive detection of the cyanide ion. The Ln-MOFs 1 and 2 exhibit excellent chemical sensing properties for CN^- with efficiency, selectivity, and excellent performance in various mixed anions. The evaluation parameters, including the quenching constant and detection limit, have been investigated to obtain the detection performance for CN^-.

Pyrene functionalized oxacalix[4]arene architecture as dual readout sensor for expeditious recognition of cyanide anion

A pyrene functionalized oxacalix[4]arene architecture (DPOC) was utilized as a fluorescence probe for selective recognition of cyanide ions. The receptor DPOC shows excellent selectivity towards cyanide ion with a red shift of 108 nm in absorption band along with a significant change in colour from light yellow to pink. The fluorescence titration experiments further confirm the lower limit of detection as 1.7µM with no significant influences of competing anions. ¹ H-NMR titration experiments support the deprotonation phenomena, as the -NH proton disappears upon successive addition of cyanide ions. The DFT calculation also indicates a certain increment of -NH bond length upon interaction with cyanide ions. The spectral properties as well as colour of DPOC-CN^- system may be reversed upon the addition of Ag⁺/ Cu²⁺ ions up to 5 consecutive cycles. Moreover, DPOC coated "test strips" were prepared for visual detection of cyanide ions.

A near-infrared emitted fluorescence probe for the detection of biosulfite in live zebrafish, mouse and real food samples

Bisulfite (HSO₃^-) has been widely used as an important food additive in daily life. Furthermore, a normal amount of HSO₃^- plays a significant role in biological systems. However, excessive intake of HSO₃^- will lead to a variety of diseases. Therefore, it is of great significance to develop an efficient fluorescent probe that can be used for detection of HSO₃^- in biological systems and food samples. In this work, a near-infrared (NIR) emitted fluorescent probe (SZY) based on hemicyanine dye was successfully synthesized and applied to detect HSO₃^- in several food samples and live animals. The proposed nucleophilic addition sensing mechanism of SZY towards HSO₃^- has been confirmed by ¹H NMR titration, high resolution mass spectrometry (HR-MS) and density functional theory (DFT) theoretical computation. The HSO₃^--induced nucleophilic reaction with α,β-unsaturated C=C binding of SZY results in the dramatic decline of the UV-vis absorption and remarkable quenching of the fluorescence emission. SZY features the advantages of near infrared emission (centered at 720 nm), high water solubility (in 98% aqueous solution), fast response time (50 s), large Stokes shift (244 nm) and low cytotoxicity. The probe SZY was successfully applied to image of HSO₃^- in live nude mouse and adult zebrafish. Semi-quantitatively analyzing the HSO₃^- level by "naked eye" in several food samples including canned fruit, white wine, white sugar and jasmine tea drinks has been realized by the colorimetric method.

Determination of cyanide based on a dual-emission ratiometric nanoprobe using silver sulfide quantum dots and silicon nanoparticles

A novel ratiometric fluorescent nanoprobe was designed for the sensitive determination of cyanide anion (CN^-) by the electrostatic attraction between positively charged silicon nanoparticles (Si NPs) and negatively charged silver sulfide quantum dots (Ag₂S QDs). The nanoprobe exhibited two well-resolved emission peaks at 446 nm and 540 nm under a single excitation wavelength (360 nm). In the presence of CN^-, the fluorescence of Ag₂S QDs at 540 nm was remarkably quenched, while the fluorescence of the Si NPs at 446 nm remained constant, establishing the desired conditions for ratiometric fluorescence detection. Under optimal conditions, the ratiometric fluorescence assay showed good linearity (R² = 0.9921) within the range 0.05-15 μM, and the limit of detection was calculated to be 56 nM (at an S/N ratio of 3). The proposed Ag₂S QD/Si NP nanoprobe has been successfully used to determine CN^- in water and sprouting potato samples with satisfactory recoveries in the range 97-110.5%.

Visualizing the Interplay of Lipid Droplets and Protein Aggregates During Aging via a Dual-Functional Fluorescent Probe

Fluorescence imaging the interplay between lipid droplets (LDs) and protein aggregates (PAs) is extremely valuable for elucidating molecular mechanisms of aging. Here, we describe the first dual-functional fluorescent probe, LW-1, for simultaneously imaging LDs and PAs in distinct fluorescence channels to dissect interplaying roles between LDs and PAs during aging. Notably, based on an intriguing mechanism of hydrogen bonds regulating single bond rotation, LW-1 selectively detected LDs in a red channel. Meanwhile, based on another mechanism of the hydrogen bond regulating intramolecular charge transfer efficiency, probe LW-1 further detected PAs in an NIR channel. Practical applications showed that LW-1 was capable of concurrently detecting LDs and PAs in living cells. Moreover, simultaneously imaging LDs and PAs in intestine tissues of mice at different aging degrees was conducted. The results denoted that the PAs level in the intestine tissue increased dramatically with aging, accompanying the buildup of LDs. Significantly, the interplay between LDs and PAs during aging was observed. These evidences demonstrated that the PAs level was closely related with aging processes in intestine tissues, while LDs were formed correspondingly to interact with PAs, suggesting that excessive PAs can be loaded into LDs and then be removed by lipophagy.

Magnetic mesoporous nanomaterials with AIE properties for selective detection and removal of CN- from water under magnetic conditions

We have prepared a type of magnetic mesoporous nanomaterial with aggregation-induced emission properties (Fe₃O₄@mSiO₂@TPA@BA, hence abbr. FSTB) to detect and remove cyanide ions (CN^-) under magnetic conditions. FSTB has a large specific surface area and improved fluorescence performance to identify CN^-, and its superparamagnetic behavior plays an important role in removing CN^-. The magnetic sensor FSTB shows excellent selectivity and anti-interference for the detection of CN^- in aqueous solutions. It is obvious from the equation LOD = 3δ/S that the limit of detection (LOD) of FSTB for CN^- is significantly lower than the permissible level of CN^- in drinkable water recommended by the World Health Organization. Therefore, the magnetic sensor FSTB has a wide range of applications for detecting and removing harmful CN^-.

Construction of DCM-based NIR fluorescent probe for visualization detection of H2S in solution and nanofibrous film

Hydrogen sulfide (H₂S) played crucial roles in biological processes and daily life, and the abnormal level of H₂S was associated with many physiological processes. In this paper, we designed and developed a dicyanomethylene-4H-chromene (DCM)-based near-infrared (NIR) fluorescent probe DCM-NO guided by theoretical calculation. The probe displayed excellent selectivity towards H₂S with a fast response time (3 min) and low detection limit (fluorescence 25.3 nM/absorption 6.61 nM) in Hela cells and real water samples. Furthermore, the probe-doped solid sensing materials (test strips and nanofibrous films) exhibited specific visualization of H₂S under ambient light or hand-held UV lamp, providing great potential for on-site and real-time application in environmental and biological systems.

A colorimetric and far-red fluorescent probe for rapid detection of bisulfite/sulfite in full water-soluble based on biquinolinium and its applications

Bisulfite (HSO₃^-) and sulfite (SO₃^2-) are involved in numerous physiological processes of living systems. However, high levels of these substances are often correlated to many diseases. Herein, we designed and synthesized a simple full water-soluble colorimetric and far-red fluorescent probe (E)-1-methyl-4-(2-(1-methylquinolin-1-ium-3-yl)vinyl)quinolin-1-ium iodide trifluoromethanesulfonate (DQ) for HSO₃^-/SO₃^2- detection by coupling 1,4-dimethylquinolinium with 3-quinolinium carboxaldehyde for the first time. The probe DQ showed high selectivity for HSO₃^- detection via a 1,4-nucleophilic addition reaction with distinct color changes from colorless to purple-red and remarkable far-red fluorescence enhancement in pure aqueous solutions. Specifically, the probe displayed a fast response (<15 s) for bisulfite, which renders it suitable for real time detection of HSO₃^-. Under the optimized conditions, the far-red fluorescence intensity was linear to the concentrations of HSO₃^- in the range from 0 to 25 μM and the detection limit was as low as 0.11 μM. Additionally, the probe could be applied to sense HSO₃^- on paper strips, real sample including vermicelli and sugar and image HSO₃^- in living cells, which indicated that probe DQ has potential application in food samples and living systems.

Amphiphilic BODIPY-based nanoparticles as "light-up" fluorescent probe for PAEs detection by an aggregation/disaggregation approach

Phthalic acid eaters (PAEs) play the role of plasticizer and have been widely used in the industrial and plastic production process. But due to not chemically bound in the polymeric matrix, PAEs can be easily released directly and/or indirectly into the environment, and pose a threat the ecosystem and human health. Small-molecule self-assembled nanoparticles have drawn more and more attention due to advantages of precise molecular structure, biocompatibility, great diversity, and tunability in optical properties and functionalities. Here we report the use of disaggregation-induced emission (DIE) based supramolecular assembly to design organic nanoprobe for detection PAEs. In the water solution, the designed small organic fluorophore AJ-1 was aggregated via noncovalent forces to form fluorescence off nanoparticles, but in the presence of PAEs, they disaggregated and produced a clear light-up fluorescent signal. The detection of PAEs with selectivity, sensitivity and rapid response were further achieved. The experiment of recovery of PAEs in real-water sample illustrated the practicability of probe AJ-1 in real-world applications. Besides, cellular uptake assay suggested that AJ-1 could pass through membrane and gather in the cytoplasm.

Controllable and reversible sensing cyanide ion using dual-functional Cu(II)-based ensemble

In this work, a dual-functional Cu²⁺-based ensemble (2S·Cu²⁺) was well designed and characterized. Then, the successional and discriminating sensing for CN^- over other competitive species (H₂PO₄^- and biothiols) was achieved based on the disaggregation of 2S·Cu²⁺ ensemble and the deprotonation of imidazole NH of regenerated sensor S in aqueous solution, respectively. The visual sensing mechanism could be clearly demonstrated by ¹H NMR, HRMS and energy changes between the HOMO-LUMO band gaps. Furthermore, the reversibility and reusability of S and 2S·Cu²⁺ upon alternating addition of CN^-/H⁺ and CN^-/Cu²⁺ were studied. Interestingly, the sequential sensing for biothiols (cysteine, glutathione and homocysteine) and CN^- was also realized through spectroscopic methodology and test paper strips. This work may provide a feasible strategy to discriminate CN^- over H₂PO₄^- and biothiols with high selectivity and sensitivity through Cu²⁺-based ensembles.

Synthesis of some new distyrylbenzene derivatives using immobilized Pd on an NHC-functionalized MIL-101(Cr) catalyst: photophysical property evaluation, DFT and TD-DFT calculations

In this study the catalytic application of a heterogeneous Pd-catalyst system based on metal organic framework [Pd-NHC-MIL-101(Cr)] was investigated in the synthesis of distyrylbenzene derivatives using the Heck reaction. The Pd-NHC-MIL-101(Cr) catalyst showed high efficiency in the synthesis of these π-conjugated materials and products were obtained in high yields with low Pd-contamination based on ICP analysis. The photophysical behaviors for some of the synthesized distyrylbenzene derivatives were evaluated. The DFT and TD-DFT methods were employed to determine the optimized molecular geometry, band gap energy, and the electronic absorption and emission wavelengths of the new synthesized donor-π-acceptor (D-π-A) molecules in the gas phase and in various solvents using the chemical model B3LYP/6-31+G(d,p) level of theory.

Novel fluorescence immunoassay for the detection of zearalenone using HRP-mediated fluorescence quenching of gold-silver bimetallic nanoclusters

In the presented study, a horseradish peroxidase (HRP)-mediated ratiometric fluorescence enzyme-linked immunosorbent assay (ELISA) for zearalenone (ZEN) was reported based on fluorescence quenching of gold-silver bimetallic nanoclusters (Au-Ag NCs). HRP-antibody was used as a bridge in this immunoassay, linking the ratiometric fluorescence signal to the ZEN concentration. HRP catalyzed the oxidization of o-phenylenediamine in the presence of H₂O₂, leading to the formation of 2,3-diaminophenazine, which not only delivered a new peak at 580 nm but also quenched Au-Ag NCs fluorescence at 690 nm. Under optimal conditions, the detection limit for the proposed ELISA was 0.017 ng/mL, which was approximately 6.6-fold lower than conventional ELISA. Moreover, analytical performances were evaluated fully including specificity, accuracy, precision, and practicability, and showed that this method provides a potential platform for sensitive and reliable detection of ZEN.

3-Hydroxy-2-naphthoic hydrazide as a probe for fluorescent detection of cyanide and aluminium ions in organic and aquo-organic media and its application in food and pharmaceutical samples

The commercially available fluorophore, 3-hydroxy-2-naphthoic hydrazide (RS2), has rationally been selected for the study, which displays a rapid fluorescent response and high sensitivity for CN^- and Al(III) ions in neat DMSO and H₂O-DMSO (1:1 v/v) media. The addition of CN^- to RS2 triggers an enhancement in fluorescence at 505 nm (green fluorescence), while the addition of Al(III) increases the fluorescence of the probe with a blue-shift of emission maximum by 25 nm (bluish-green fluorescence). The probe's action was investigated by ¹H NMR titrations that indicate deprotonation of OH and NH moieties by these ions. ²⁷Al NMR of RS2-Al(III) complex suggests an octahedral geometry for the complex. The sensitivity of the fluorescent-based assays in aq. DMSO medium, 0.8 µM for CN^- and 1.9 µM for Al(III) ions are far below the limits in the World Health Organization guidelines for drinking water. RS2 detects Al(III) by the chelation-enhanced fluorescence (CHEF) mechanism. Besides, RS2 was successfully applied to detect CN^- and Al(III) ions in food materials and pharmaceutical samples, respectively.

A turn-on red-emitting fluorescent probe for determination of copper(II) ions in food samples and living zebrafish

Herein, we developed a turn-on red-emitting fluorescent probe for the sensitive and selective detection of copper ions (Cu²⁺) in food samples and living zebrafish. The probe employs a hemicyanine scaffold as the fluorophore and a 2-pyridinecarbonyl group as the recognition receptor and quenching moiety. The 2-pyridinecarbonyl moiety can be specifically cleaved by Cu²⁺ and results in an approximately 18-fold fluorescence enhancement of the probe, thereby providing a fluorescence turn-on assay for Cu²⁺. Additionally, the probe exhibited excellent selectivity, high sensitivity, a broad linear relationship (0.020 to 8.0 μM), and a low limit of detection (4.0 nM, S/N = 3) for Cu²⁺. Concomitantly, the probe exhibited satisfactory analytical performance when used with actual food samples. Moreover, the probe could be used for in situ determination of Cu²⁺ in both living plant tissues and in living zebrafish.

Application of a Colorimetric and Near-Infrared Fluorescent Probe in Peroxynitrite Detection and Imaging in Living Cells

Peroxynitrite (ONOO^-) plays a vital role in pathological and physiological processes, and an excessive amount of ONOO^- causes various diseases. Developing a specific and sensitive method for the detection of ONOO^- in biological systems is significant. Herein, we reported a novel colorimetric and near-infrared fluorescent probe (pyridin-4-ylmethyl (Z)-2-cyano-2-(3-((E)-4-hydroxystyryl)-5,5-dimethylcyclohex-2-en-1-ylidene)acetate diphenyl phosphinate group (AN-DP)) based on isophorone and phosphinate groups for ONOO^- detection. The probe displayed excellent selectivity toward ONOO^- compared with other relevant analytes. It showed a good linear relationship between the fluorescence intensity at 670 nm and ONOO^- concentration (0-10 μM) with a low detection limit (53 nM). Importantly, the probe was a colorimetric and near-infrared fluorescent probe suitable for ONOO^- detection. Furthermore, the probe could be used for imaging ONOO^- in HepG2 cells.

A Simple Water-Soluble ESIPT Fluorescent Probe for Fluoride Ion with Large Stokes Shift in Living Cells

Developing an effective method for monitoring fluoride ion in biological samples is meaningful because fluoride ion plays a vital role in biological processes. In this contribution, a simple water-soluble ESIPT fluorescent probe 2-((4-((tert-butyldiphenylsilyl)oxy)-1,3-dioxoisoindolin-2-yl)methyl)-1-ethylpyridin-1-ium iodide (SPI) was constructed for monitoring fluoride ion. The probe SPI containing pyridinium salt group exhibited preeminent water solubility. The probe SPI introducing a trimethyldiphenylsilyl ether recognition group displayed excellent selectivity for fluoride ion over other biologically relevant species. Additionally, the probe SPI exhibited a fast response for a fluoride ion, suggesting that it could provide real-time fluoride ion detection. Importantly, the probe could detect fluoride ion with a linear range of 0-70.0 × 10-6 M and a low detection limit of 1.16 × 10-6 M. Furthermore, probe SPI could detect fluoride ion with a large Stokes shift (98 nm), which was attributed to ESIPT fluorescence sensing process. At last, probe SPI was successfully employed to monitor fluoride ion in living cells.

A Highly Selective Fluorescent Probe for Hg2+ Based on a 1,8-Naphthalimide Derivative

Hg2+ has a significant hazardous impact on the environment and ecosystem. There is a great demand for new methods with high selectivity and sensitivity to determine mercury in life systems and environments. In this paper, a novel turn-on Hg2+ fluorescent probe has been reported with a naphthalimide group. The Hg2+ fluorescent probe was designed by the inspiration of the well-known specific Hg2+-triggered thioacetal deprotection reaction. A 1,2-dithioalkyl group was chosen as the specific recognition site of Hg2+. The probe showed weak fluorescence without Hg2+, and the color of the solution was light yellow. In the presence of Hg2+, the probe reacted specifically with the mercury ion to produce an aldehyde and emitted strong fluorescence, and the color of the solution also turned light green, thus realizing the monitoring of the mercury ion. The Hg2+ fluorescent probe showed outstanding sensitivity and selectivity toward Hg2+. Furthermore, the Hg2+ fluorescent probe could work in a wide pH range. The linear relationship between the fluorescence intensity at 510 nm and the concentration of Hg2+ was obtained in a range of Hg2+ concentration from 2.5 × 10-7 to 1.0 × 10-5 M. The detection limit was found to be 4.0 × 10-8 M for Hg2+. Furthermore, with little cell toxicity, the probe was successfully applied to the confocal image of Hg2+ in PC-12 cells.

A novel coumarin-chitosan fluorescent hydrogel for the selective identification of Fe2+ in aqueous systems

Functional fluorescent hydrogels were synthesized, and they can detect and adsorb Fe²⁺ in aqueous solution.

An endoplasmic reticulum-targeting and ratiometric fluorescent probe for hypochlorous acid in living cells based on a 1,8-naphthalimide derivative

A novel reticulum-targeting and ratiometric fluorescent probe for determining hypochlorous acid has been developed.