Fluorescent Probe Research Articles

Simultaneous detection of Cu2+ and amoxicillin based on the copper and nitrogen-regulated fluorescent probe

A novel fluorescence-based probe represented as Cu, N-CDs, was developed for the dual sensingdetection of Cu2+ and amoxicillin (AMO), which had a high quantum yield up to 60.08 %, along with excellent photoluminescent properties and remarkable stability. When detecting Cu2+, the fluorescence signal from Cu, N-CDs probe experienced quenching due to photoinduced electron transfer (PET). Subsequently, the introduction of AMO led to the recovery of the probe's fluorescence. This recovery was likely attributed to the superior affinity between Cu2+ and AMO, resulting in the displacement of Cu2+ from the Cu, N-CDs and blocked the PET process. Notably, the detection limits of Cu2+ and AMO were determined 18 nM and 9 nM, respectively. We further demonstrated the practical utility of the Cu, N-CDs probe through its successful application in the analysis of Cu2+ and AMO in Chinese herbal medicine and milk samples. Overall, our findings highlighted the potency of Cu, N-CDs as versatile and effective tools for the detection of Cu2+ and AMO, paving the way for their broad applications in the safety analysis of food and pharmaceutical.

Specific detection of sarin gas Mimicking, diethylchlorophosphate employing solvent mediated in-situ generated hydroxyl functional group in a phthalimide-chromone coupled fluorogenic probe

Nerve agents are particularly hazardous substances and can result in fatality due to suppressing acetylcholinesterase function. This article introduced a fluorescent probe, (E)-5-(((4-hydroxy-2-methoxy-2H-chromen-3-yl)methylene)amino)isoindoline-1,3-dione (CMAD), which was exceptionally effective at detecting the sarin replacement diethylchlorophosphate (DCP), both in solution and vapor phase, respectively which exhibited quick response, excellent sensitivity and specificity. As a result of the gradual addition of DCP into the solution of the probe, the photoluminescence intensity at 476 nm is markedly increased, exhibiting bright cyan color fluorescence because of inhibition of the excited state intramolecular proton transfer (ESIPT) process, which is also clearly reflected in the estimation of photoluminescence quantum yield of phosphorylated CMAD (0.55 relatives to 4-aminophalimide) and the color chromaticity (CIE) diagram. The lowest detection limit and limit of quantification are 3.25 µM and 10.8 µM, respectively, within the stockpiles of other analogous analytes. Additionally, for on-the-spot detection, the probe may also be utilized in the test strips with superior selectivity for DCP. The ability to identify and measure DCP in the gas phase has also been established using a dip-stick and dipped-vial-conical-flask analysis. Moreover, we also performed the smartphone-based technique for the practical utility of CMAD for the on-spot quantification and detection of sarin gas in real threat situations. The effective demonstrations of practical usage, including soil analysis, inspire additional applications in different fields. Therefore, probe CMAD is a reliable, on-site monitoring fluorescence probe for precisely identifying DCP in the presence of additional competing nerve agents.

A hemicyanine-based fluorescent probe for detection of pH and its applications in live cells imaging and food monitoring

pH as an important parameter is closely related to many pathological processes and food freshness. In this paper, a new pH-sensitive fluorescent probe 1 based on hemicyanine dye was synthesized and used for the detection of pH in live cells and food spoilage. Under neutral and alkaline conditions, the phenolic hydroxyl group of the probe deprotonates, forming a closed spirocyclic structure and resulting in fluorescence quenching. Under acidic conditions, the probe maintains an open-loop structure and has intense fluorescence. The probe possessing good selectivity and stability can target lysosomes and visualize the exogenous pH in live cells. Furthermore, by using this probe, we successfully achieved the monitoring of pH in metamorphic process of shrimp and pork. This probe is expected to provide a good imaging tool for real-time detection of pH in live cells and food monitoring.

A phenothiazine coumarin based fluorescent probe with AIE feature for real-time detecting lysosomal ClO– in living cell

A new phenothiazine coumarin based probe WX-Lyso for detection of ClO– was developed. The probe showed obvious aggregation-induced emission (AIE) characteristic and exhibited a highly selective and sensitive turn-on fluorescence signal at 544 nm for ClO– with a large Stokes shift of 144 nm. The limit of detection (LOD) of ClO– was measured as low as 0.99 μM and a good line equation was obtained in the 0–50 μM concentration range. The detection mechanism was elucidated FT-IR, ESI-MS analysis and DFT. Furthermore, the probe had been demonstrated successfully has good lysosomal-targeting and high-contrast imaging abilities, which has the potential to become a new chemical tool and provide help for detecting ClO– in living systems.

Novel fluorescent sensor based on triazole-pyridine derivative for selective detection of mercury (II) ions in different real water samples: Experimental and DFT calculations

Toxic heavy metals, particularly mercury II ions, must be selectively detected in industrial effluent to restrict their percentage and thereby aid in environmental protection. The present study describes the synthesis of 6-(4-(4-(5-cyano-6-oxo-4-styryl)-1,6-dihydropyridin-2-yl)-5-methyl-1H-1,2,3-triazol-1-yl)phenyl)-2-oxo-4-styryl)-1,2-dihydropyridine-3-carbonitrile (TOHC) and its ability as a novel selective fluorescent probe for the detection of mercury II ions in different real water samples. The structure of the prepared TOHC was confirmed by both FTIR and 1HNMR analysis, while crystal structure and thermal stability was investigated using XRD and TGA techniques. The optical properties of TOHC were investigated using both UV–vis and fluorescence spectroscopy at different pH values. Its luminescent properties obtained when TOHC is excited by a wavelength equal to 424 nm, where a maximum emission peak has observed at a wavelength equal to 466.6 nm. Moreover, using Stern-Volmer equation indicate that there is a good correlation between the concentration of Hg2+ ions and the fluorescence intensity of TOHC accompanied with high quenching rate equal to 2.24 x 104 mol−1.L. Selectivity of TOHC toward Hg2+ ions was confirmed by the assistance of fifteen different metal cations. In addition, Job’s Plot method and UV–vis spectroscopy were used to estimate the stoichiometry as well as understand the quenching mechanism between TOHC sensor and Hg2+ ions. The applicability of TOHC sensor for the detection of Hg2+ ions in real samples was further validated using five different real water samples and exhibited excellent results. Lastly, DFT calculations were conducted to provide atomistic insights into the chemical interaction between Hg(II) and TOHC.

Two new rhodamine-based fluorescent probes with thiophen/selenophene acrylate group for selective detection of Cys in living cells

Cysteine (Cys), one of the biological thiols, has long been an important sensing target. In this work, two new rhodamine-based fluorescent probes with thiophen/selenophene acrylate group (Rh-S and Rh-Se) have been obtained and fully characterized. Their sensing behaviors have been researched by UV-Vis absorption and fluorescence spectra, which display high sensitivity and good selectivity for the detection of Cys with low detection limit (0.268/0.270 μM) and fast response time (30/40 min), and exhibit a "turn on" response toward Cys. The possible sensing mechanism has been proposed and confirmed by HRMS and 1H NMR. Biological studies reveal that probe Rh-S has low cytotoxicity and good biocompatibility, thereby could be further used to determine Cys in living cells.

Tumor Targeting with Apatinib-loaded Nanoparticles and Sonodynamic Combined Therapy

This study implies the enhancement of apatinib killing effect in 4T1 tumor cells through constructing drug-loaded nanoparticles apatinib/Ce6@ZIF-8@Membranes (aCZM) to enhance tumor therapeutic targeting and reduce toxic side following sonodynamic therapy (SDT). apatinib/Ce6@ZIF-8 (aCZ) were synthesized by in situ encapsulation, and aCZM were constructed by encapsulating the nanoparticles with extracted breast cancer 4T1 cell membranes. aCZM were characterized and tested for the stability by electron microscopy, and the membrane proteins on the nanoparticles' surface were assessed using SDS-PAGE gel electrophoresis. The cell viability of 4T1 cells following treatment with aCZM was tested using cell counting kit-8 (CCK-8). The uptake of nanoparticles was detected by laser confocal microscopy and flow cytometry, and the SDT-mediated production of reactive oxygen species (ROS) was verified by singlet oxygen sensor green (SOSG), electron spin resonance (ESR), and DCFH-DA fluorescent probes. The CCK-8 assay and flow cytometry using Calcein/PI were used to assess the antitumoral effect of aCZM nanoparticles under SDT. The biosafety of aCZM was further verified in vitro and in vivo using the hemolysis assay, routine blood test and H&E staining of vital organs in Balb/c mice. aCZM with an average particle size of about 210.26 nm were successfully synthesized. The results of the SDS-PAGE gel electrophoresis experiment showed that aCZM have a band similar to that of pure cell membrane proteins. The CCK-8 assay demonstrated the absence of effects on cell viability at a low concentration range, and the relative cell survival rate reached more than 95%. Laser confocal microscopy and flow cytometry analysis showed that aCZM treated group has the strongest fluorescence and the highest cellular uptake of nanoparticles. SOSG, ESR, and DCFH-DA fluorescent probes all indicated that the aCZM + SDT treated group has the highest ROS production. The CCK-8 assay also showed that when the ultrasound intensity was fixed at 0.5 W/cm2, the relative cell survival rates in the medium concentration group (10 μg/ml) (5.54 ± 1.26%) and the high concentration group (20 μg/ml) (2.14 ± 1.63%) were significantly lower than those in the low concentration group (5 μg/ml) (53.40 ± 4.25%). Moreover, there was a concentration and intensity dependence associated with the cell-killing effect. The mortality rate of the aCZM in the ultrasound group (44.95±3.03%) was significantly higher than that of the non-ultrasound (17.00±2.26%) group and aCZ + SDT group (24.85 ± 3.08%) (P<0.0001). The live and dead cells' staining (Calcein/PI) also supported this result. Finally, in vitro hemolysis test at 4 and 24 hours showed that the hemolysis rate of the highest concentration group was less than 1%. The blood routine, biochemistry, and H&E staining results of major organs in Balb/c mice undergoing nano-treatments showed no obvious functional abnormalities and tissue damage in 30 days. In this study, a multifunctional bionic drug delivery nanoparticles (aCZM) system with good biosafety and compatibility in response to acoustic dynamics was successfully constructed and characterized. This system enhanced apatinib killing effect on tumor cells and reduced toxic side effects under SDT.

Penthorum chinense Pursh inhibits ferroptosis in cellular and Caenorhabditis elegans models of Alzheimer's disease

Background: Ferroptosis, a unique type of cell death triggered by iron-dependent lipid peroxidation, plays a critical role in the pathogenesis of Alzheimer's disease (AD), a debilitating condition marked by memory loss and cognitive impairment due to the accumulation of beta-amyloid (Aβ) and hyperphosphorylated Tau protein. Increasing evidence suggests that inhibitors of ferroptosis could be groundbreaking in the treatment of AD. Method: In this study, we established in vitro ferroptosis using erastin-, RSL-3-, hemin-, and iFSP1-induced PC-12 cells. Using MTT along with Hoechst/PI staining, we assessed cell viability and death. To determine various aspects of ferroptosis, we employed fluorescence probes, including DCFDA, JC-1, C11 BODIPY, Mito-Tracker, and PGSK, to measure ROS production, mitochondrial membrane potential, lipid peroxidation, mitochondrial morphology, and intracellular iron levels. Additionally, Western blotting, biolayer interferometry technology, and shRNA were utilized to investigate the underlying molecular mechanisms. Furthermore, p-CAX APP Swe/Ind- and pRK5-EGFP-Tau P301L overexpressing PC-12 cells, along with Caenorhabditis elegans (C. elegans) strains CL4176, CL2331, and BR5270, were employed to examine ferroptosis in AD models. Results: Here, we conducted a screening of our natural medicine libraries and identified the ethanol extract of Penthorum chinense Pursh (PEE), particularly its ethyl acetate fraction (PEF), displayed inhibitory effects on ferroptosis in cells. Specifically, PEF inhibited the generation of ROS, lipid peroxidation, and intracellular iron levels. Furthermore, PEF demonstrated protective effects against H2O2-induced cell death, ROS production, and mitochondrial damage. Mechanistic investigations unveiled PEF's modulation of intracellular iron accumulation, GPX4 expression and activity, and FSP1 expression. In p-CAX APP Swe/Ind and pRK5-EGFP-Tau P301L overexpressing PC-12 cells, PEF significantly reduced cell death, as well as ROS and lipid peroxidase production. Moreover, PEF ameliorated paralysis and slowing rate in Aβ and Tau transgenic C. elegans models, while inhibiting ferroptosis, as evidenced by decreased DHE intensity, lipid peroxidation levels, iron accumulation, and expression of SOD-3 and gst-4. Conclusion: Our findings highlight the suppressive effects of PEF on ferroptosis in AD cellular and C. elegans models. This study helps us better understand how ferroptosis affects AD and emphasizes the potential of PCP as a candidate for AD intervention.

Optical recordings of organellar membrane potentials and the components of membrane conductance in lysosomes.

The eukaryotic cell is highly compartmentalized with organelles. Owing to their function in transporting metabolites, metabolic intermediates and byproducts of metabolic activity, organelles are important players in the orchestration of cellular function. Recent advances in optical methods for interrogating the different aspects of organellar activity promise to revolutionize our ability to dissect cellular processes with unprecedented detail. The transport activity of organelles is usually coupled to the transport of charged species; therefore, it is not only associated with the metabolic landscape but also entangled with membrane potentials. In this context, the targeted expression of fluorescent probes for interrogating organellar membrane potential (Ψorg) emerges as a powerful approach, offering less-invasive conditions and technical simplicity to interrogate cellular signalling and metabolism. Different research groups have made remarkable progress in adapting a variety of optical methods for measuring and monitoring Ψorg. These approaches include using potentiometric dyes, genetically encoded voltage indicators, hybrid fluorescence resonance energy transfer sensors and photoinduced electron transfer systems. These studies have provided consistent values for the resting potential of single-membrane organelles, such as lysosomes, the Golgi and the endoplasmic reticulum. We can foresee the use of dynamic measurements of Ψorg to study fundamental problems in organellar physiology that are linked to serious cellular disorders. Here, we present an overview of the available techniques, a survey of the resting membrane potential of internal membranes and, finally, an open-source mathematical model useful to interpret and interrogate membrane-bound structures of small volume by using the lysosome as an example.

Solvation dynamics on the diffusion timescale elucidated using energy-represented dynamics theory.

Photoexcitation of a solute alters the solute-solvent interaction, resulting in the nonequilibrium relaxation of the solvation structure, often called a dynamic Stokes shift or solvation dynamics. Thanks to the local nature of the solute-solvent interaction, the characteristics of the local solvent environment dissolving the solute can be captured by the observation of this process. Recently, we derived the energy-represented Smoluchowski-Vlasov (ERSV) equation, a diffusion equation for molecular liquids, which can be used to analyze the solvation dynamics on the diffusion timescale. This equation expresses the time development for the solvent distribution on the solute-solvent pair interaction energy (energy coordinate). Since the energy coordinate can effectively treat the solvent flexibility in addition to the position and orientation, the ERSV equation can be utilized in various solvent systems. Here, we apply the ERSV equation to the solvation dynamics of 6-propionyl-2-dimethylamino naphthalene (Prodan) in water and different alcohol solvents (methanol, ethanol, and 1-propanol) for clarifying the differences of the relaxation processes among these solvents. Prodan is a solvent-sensitive fluorescent probe and is thus widely utilized for investigating heterogeneous environments. On the long timescale, the ERSV equation satisfactorily reproduces the relaxation time correlation functions obtained from the molecular dynamics (MD) simulations for these solvents. We reveal that the relaxation time coefficient on the diffusion timescale linearly correlates with the inverse of the translational diffusion coefficients for the alcohol solvents because of the Prodan-solvent energy distributions among the alcohols. In the case of water, the time coefficient deviates from the linear relationship for the alcohols due to the difference in the extent of importance of the collective motion between the water and alcohol solvents.

Recent Progress in Folic Acid Detection Based on Fluorescent Carbon Dots as Sensors: A Review.

Folic acid (FA) is a water-soluble vitamin found in diverse natural sources and is crucial for preserving human health. The risk of health issues due to FA deficiency underscores the need for a straightforward and sensitive FA detection methodology. Carbon dots (CDs) have gained significant attention owing to their exceptional fluorescence performance, biocompatibility, and easy accessibility. Consequently, numerous research studies have concentrated on developing advanced CD fluorescent probes to enable swift and precise FA detection. Despite these efforts, there is still a requirement for a thorough overview of the efficient synthesis of CDs and their practical applications in FA detection to further promote the widespread use of CDs. This review paper focuses on the practical applications of CD sensors for FA detection. It begins with an in-depth introduction to FA and CDs. Following that, based on various synthetic approaches, the prepared CDs are classified into diverse detection methods, such as single sensing, visual detection, and electrochemical methods. Furthermore, persistent challenges and potential avenues are highlighted for future research to provide valuable insights into crafting effective CDs and detecting FA.

Excited State Rotational Freedom Impacts Viscosity Sensitivity in Arylcyanoamide Fluorescent Molecular Rotor Dyes.

The microviscosity of intracellular environments plays an important role in monitoring cellular function. Thus, the capability of detecting changes in viscosity can be utilized for the detection of different disease states. Viscosity-sensitive fluorescent molecular rotors are potentially excellent probes for these applications; however, the predictable relationships between chemical structural features and viscosity sensitivity are poorly understood. Here, we investigate a set of arylcyanoamide-based fluorescent probes and the effect of small aliphatic substituents on their viscosity sensitivity. We found that the location of the substituents and the type of π-network of the fluorophore can significantly affect the viscosity sensitivity of these fluorophores. Computational analysis supported the notion that the excited state rotational energy barrier plays a dominant role in the relative viscosity sensitivity of these fluorophores. These findings provide valuable insight into the design of molecular rotor-based fluorophores for viscosity measurement.

GABAA Receptor‐Specific Carbon Dots for High‐Contrast Hepatocellular Carcinoma Imaging and Differentiation

AbstractTargeted fluorescence probes for imaging and differentiation of hepatocellular carcinoma (HCC) are highly desirable from its scientific research and clinical applications. However, most of the current targeted fluorescence probes focus on the variation of intracellular microenvironment caused by the cancerization of hepatocyte, which causes a fluorescence intensity alteration but fails to produce a spatial differentiation due to the lack of robust parameters for further improving accuracy. Herein, the study develops a new fluorescent carbon dot (CTF‐CDs) that can target the overexpressed GABAA receptor (GABAAR) on cell membrane for accurate and high‐contrast imaging of HCC and differentiation. The competition response between CTF‐CDs and typical receptor‐binding ligands reveals their affinity toward the picrotoxin‐binding site of GABAAR. Based on this GABAAR‐targeting ability, accurate imaging of HCC cells is realized by lighting their membranes, along with a big difference from the intracellular fluorescence of normal liver cells and other cancer cells. In addition, the CTF‐CDs have also been used to visualize the anticancer drug‐induced variations on HCC cell membrane and fluorescent imaging in HCC tissue. This work extends the targeting object of fluorescence probes from intracellular microenvironment to membrane protein, adding a new dimension to the imaging and differentiation of HCC.

Temperature imaging inside fluid devices using a ratiometric near infrared (NIR-II/III) fluorescent Y2O3: Nd3+, Yb3+, Er3+ nanothermometer.

Luminescence thermometry is a non-contact method that can measure surface temperatures and the temperature of the area where the fluorescent probe is located, allowing temperature distribution visualizations with a camera. Ratiometric fluorescence thermometry, which uses the intensity ratio of fluorescence peaks at two wavelengths with different fluorescence intensity dependencies, is an excellent method for visualizing temperature distributions independent of the fluorophore spatial concentration, excitation light intensity and absolute fluorescence intensity. Herein, Nd3+/Yb3+/Er3+-doped Y2O3 nanomaterials with a diameter of 200nm were prepared as phosphors for temperature distribution measurement of fluids at different temperatures. The advantages of this designed fluorescent material include non-aggregation in water and the fact that its near-infrared (NIR) fluorescence excitation (808nm) is not absorbed by water, thereby minimizing sample heating upon irradiation. Under optical excitation at 808nm, the ratio of the fluorescence intensities of Yb3+ (IYb; 975nm) and Er3+ (IEr; 1550nm), which exhibited different temperature responses, indicated the temperature distribution inside the fluid device. Thus, this technique using Nd3+/Yb3+/Er3+-doped Y2O3 is expected to be applied for temperature distribution mapping analysis inside fluidic devices as a ratiometric NIR fluorescence thermometer, which is unaffected by laser-induced heating.

Confined Unimolecular Micelles for Directed Self-Assembly of Ultrastable Multiple-Responsive Ratiometric Fluorescent Ultrasmall Nanoparticle Assemblies.

Ultrasmall fluorescent nanomaterials have been widely studied as novel fluorescent probes; however, these nanomaterials are prone to structural damage or aggregation, and the sensitivity and accuracy of most single emission fluorescence probes were very low. Therefore, the controlled synthesis of stable dual-emission ratiometric fluorescence ultrasmall assembly probes still remains a challenge. Herein, star-like polymer unimolecular micelles were utilized as a scaffold template to encapsulate fluorescent ultrasmall carbon quantum dots (CQDs) and gold nanoclusters (AuNCs) via the polymer template directed self-assembly strategy to obtain multiple-responsive ratiometric fluorescent assemblies. The assemblies were ultrastable, well-defined, and nearly monodispersed with controlled size, regular morphology, and pH- and thermal-responsiveness. The assemblies can be applied to realize rapid, sensitive, quantitative, and specific detection of Cu2+ and GSH. Moreover, the convenient rapid real-time detection was realized via the combination of the visualized paper-based sensor, and the multilevel information encryption was also achieved.

Synthesis of Monofluorinated 7-Hydroxycoumarin-3-Carboxamides as Cell-Permeable Fluorescent Molecular Probes

Synthesis of Monofluorinated 7-Hydroxycoumarin-3-Carboxamides as Cell-Permeable Fluorescent Molecular Probes

An Innovative Methodology to Characterize, at the Molecular Scale, Interactions in Polysaccharide Aqueous Solutions

Characterizing molecular interactions at the microscopic level remains difficult and, therefore, represents a key target to better understand macromolecule and biomacromolecule behaviors in solution, alone, or in mixtures with others. Therefore, accurate characterization in liquid media, especially in aqueous solutions, without causing any perturbation of the system in which they are studied, is quite difficult. To this purpose, the present paper describes an innovative methodology based on fluorescence spectrophotometry. Two molecular fluorescent probes, namely 8-anilino-1-naphtalenesulfonic acid (ANS) and 2-benzofuryl-3-hydroxy-4(1H)-quinolone (3HQ-Bf), were selected to characterize, respectively, the dipole-dipole interactions and hydrophobic micro-domains, for the first one, and hydrogen bonding, for the second. As a support to study molecular interactions, xanthan, galactomannan, and corresponding mixtures of these substances which are well known to exhibit a synergy of interactions in well-defined mixture conditions were chosen. Once the methodology was set up, the existence of the three types of interactions in these systems was demonstrated, thus allowing the elucidation of the mechanisms of interactions at the molecular scale.

A metal-organic framework and quantum dot-based ratiometric fluorescent probe for the detection of formaldehyde in food.

Agreen and sensitive ratio fluorescence strategy was proposed for the detection of formaldehyde (FA) in food based on a kind of metal-organic frameworks (MOFs), MIL-53(Fe)-NO2, and nitrogen-doped Ti3C2 MXene quantum dots (N-Ti3C2 MQDs) with a blue fluorescence at 450nm. As a type of MOFs with oxidase-like activity, MIL-53(Fe)-NO2 can catalyze o-phenylenediamine (OPD) into yellow fluorescent product 2,3-diaminophenazine (DAP) with a fluorescent emission at 560nm. DAP has the ability to suppress the blue light of N-Ti3C2 MQDs due to inner filter effect (IFE). Nevertheless, Schiff base reaction can occur between FA and OPD, inhibiting DAP production. This results in a weakening of the IFE which reverses the original fluorescence color and intensity of DAP and N-Ti3C2 MQDs. So, the ratio of fluorescence intensity detected at respective 450nm and 560nm was designed as the readout signal to detect FA in food. The linear range of FA detection was 1-200µM, with a limit of detection of 0.49µM. The method developedwas successfully used to detect FA in food with satisfactory results. It indicates that MIL-53(Fe)-NO2, OPD, and N-Ti3C2 MQDs (MON) system constructed by integrating the mimics enzyme, enzyme substrate, and fluorescent quantum dots has potential application for FA detection in practical samples.

Synthesis and Application of 1,8-Naphthalimide Derivatives Fluorescent Probe for Sequential Recognition of Cu2+ and H2PO4.

A naphthalimide Schiff base fluorescent probe (BSS) was designed and synthesized from 4-bromo-1,8-naphthalic anhydride, and its structure was characterized by 1HNMR, 13CNMR, FTIR, and MS. Fluorescence emission spectra showed that probe BSS could realize the "turn-off" detection of Cu2+ in acetonitrile solution, detection process with strong specificity and excellent anti-interference of other metal ions. In the fluorescence titration experiments, fluorescence intensity of BSS showed a good linear relationship with the Cu2+ concentration (0-10 µmol/L), and the detection limit was up to 7.0 × 10- 8 mol/L. Meanwhile, BSS and Cu2+ could form a 1:1 complex (BSS-Cu2+) during the reaction process. Under the same detection conditions, complex BSS-Cu2+ had specific fluorescence recovery properties for H2PO4- and the whole process was not only fast (6s) but also free of interference from other anions, with a detection limit was as low as 5.7 × 10- 8 mol/L. In addition, complex BSS-Cu2+ could be successfully applied to the detection of H2PO4- in actual water samples, which with excellent application prospects.

A Reaction-based Ratiometric Fluorescent Probe with Large STOKES Shift for Cu2+ in Neat Aqueous Solution.

A novel reaction-based ratiometric fluorescent probe 1 for Cu2+ using picolinate as the reaction site and hemicyanine as the fluorophore was developed. 1 displayed maximum absorption peak at 355nm and fluorescence emission peak at 500nm, with large Stokes shift of 145nm. Upon reaction with Cu2+, the maximum absorption and fluorescence emission peaks red-shifted to 390nm and 570nm respectively, owing to Cu2+-induced hydrolysis of the picolinate moiety in 1. Meanwhile, the solution of 1 turned from green to orange under a 365nm UV lamp. 1 not only could detect Cu2+ ratiometrically by the ratios of both absorbance (A390 nm/A355 nm) and fluorescence intensity (F570 nm/F500 nm), but also displayed large Stokes shift, fast response, high sensitivity and excellent selectivity over other metal ions in neat aqueous solution.