Dual-emission Fluorescent Probe Research Articles

Carbon dots@Cu metal-organic frameworks hybrids for ratiometric fluorescent determination of pesticide thiophanate-methyl.

A dual-emission fluorescent (FL) probe was constructed by coordinating Cu2+ of copper metal-organic frameworks (Cu-MOFs) with - COO- group of carbon dots (CDs) for pesticide thiophanate-methyl (TM) determination. TM was recognized by organic ligands (H2BDC and H2BDC-NH2) of Cu-MOFs via π stacking. Due to the higher affinity of Cu2+ to TM than ligands and CDs, TM chelated with Cu2+ to form TM-Cu complex. Thus coordination of Cu-MOFs was damaged and the ligands were released resulting in the FL intensity increase of Cu-MOFs (F430). And also CDs were released from CDs@Cu-MOFs hybrids and electron transfer from CDs to CuMOFs was inhibited, leading to the FL intensity increase of CDs (F600). The FL intensity ratio (F430/F600) showed a good linear relationship with TM concentrations of 0.0307-0.769μmol L-1 with a limit of detection (LOD) of ~ 3.67nmol L-1. The probe was successfully applied to detect TM in spiked food samples with satisfactory recoveries of 93.1-113%. Additionally, visual detection of TM was achieved according to the fluorescence color variation from blue to carmine, indicating promising application of CDs@Cu-MOFs probe.

A “bottle-around-ship” method to encapsulated carbon nitride and CdTe quantum dots in ZIF-8 as the dual emission fluorescent probe for detection of mercury (II) ion

A facile and efficient "bottle-around-ship" approach for preparing the ratiometric fluorescent probe has been developed by encapsulating the red-colored fluorescence CdTe quantum dots (QDs) and blue-colored fluorescence graphitic carbon nitride quantum dots (g-CNQDs) into the zeolitic imidazolate metal-organic frameworks (ZIF-8) in one step. At a single excitation of 360nm, the obtained probe ZIF-8@g-CNQD/CdTe shows the dual-emission peaked at 450 and 633nm, respectively. The red emission of CdTe QDs is selectively quenched by the Hg2+, whereas the blue fluorescence of g-CNQDs as an internal reference is insensitive, resulting in an apparent color transformation from pink to blue for special recognition of Hg2+. By this approach, the relative fluorescence intensity ratio (F633/F450) decreased linearly with increasing Hg2+ concentration in the 0.2-3.5μM range with a low limit of detection (LOD) of ~ 46nM. Therefore, we demonstrate that this "bottle-around-ship" process provides a new strategy for the construction of ratiometric fluorescent Hg2+ probes with good simplicity, high efficiency, and excellent stabilities. Moreover, the obtained Hg2+ fluorescent probe shows good results in the detection of actual samples.

A highly water-stable dual-emission fluorescent probe based on Eu3+-loaded MOF for the simultaneous detection and quantification of Fe3+ and Al3+ in swine wastewater

A novel dual-emissive Eu3+-loaded metal–organic framework (MOF) is designed and successfully fabricated by introducing 2-hydroxyterephthalic acid (H2BDC-OH) and Eu3+ ions into an UiO-66-type MOF material. The obtained MOF, here referred to as EuUCH, exhibits dual emission at 450 and 614 nm, and both emissions are quite stable in aqueous media in the pH range of 4–11. EuUCH is characterized by a high selectivity and sensitivity toward Fe3+ and Al3+, which yield different responsive modes. The two emissions of EuUCH are quenched by Fe3+; by contrast, only the emission at 450 nm is quenched by Al3+ showing a ratiometric fluorescence signal. More importantly, as there is no clear interference between the signals of Fe3+ and Al3+, EuUCH is successfully utilized for the simultaneous detection of Fe3+ and Al3+ in their mixtures. In addition, the simultaneous quantification of Fe3+ and Al3+ is achieved in more complicated swine wastewater with good recoveries. This work provides a water-stable dual-emissive probe and the possibility to achieve the simultaneous quantification of Fe3+ and Al3+ in complicated environment wastewater.

A dual-emission fluorescent ratiometric probe based on bimetallic lanthanide complex interacted in nanoclay for monitoring of food spoilage

Owing to increasing food-safety issues, food insecurity is an enormous threat to human health and the economy. Therefore, it is necessary to explore efficient and early food spoilage detection. Herein, we develop a ratiometric fluorescent probe based on the embedding of bimetallic Ln3+ (Eu3+ and Tb3+) complex intercalated in nanoclay, which can monitor the real-time visual surveillance freshness of food. The fluorescent probe exhibits a dual-emission responsive to biogenic amine along with a significant decrease in Tb3+ emission intensity and an increase in Eu3+ emission intensity, enabling an obviously distinguishable color transition from yellow to orange to rose red clearly discerned by naked eyes. The probe shows an outstanding response and excellent sensitivity which has a low limit of detection (LOD=0.137 mg L−1) for target biogenic amines (histamine) in the range (4–22 mg L−1). Besides, we use the gel to inspect the change in the freshness of raw fish in a hermetic space. It is proved that the nanocomposite can be applied to the on-site inspection of the food freshness. This work provides a novel direction for the evolution of fluorescent nano-clay based lanthanide complexes as a new platform for application in food surveillance.

A novel dual-emission fluorescent probe for ratiometric and visual detection of Cu2+ ions and Ag+ ions.

In this work, the biomolecule glutathione was used to prepare cyan fluorescent carbon dots (GSH@CDs) by a hydrothermal method. The GSH@CDs were adopted as the scaffolds to synthesize fluorescent gold nanoclusters (GSH@CDs-Au NCs) with two independent emission peaks at 430nm and 700nm. A fluorescent method for the Cu2+ and Ag+ ion assay was established based on the fluorescence quenching or enhancement at 700nm of GSH@CDs-Au NCs. The fluorescent test strips were successfully prepared for visual detection of Cu2+ ions and Ag+ ions based on GSH@CDs-Au NCs. In addition, GSH@CDs-Au NCs were found to possess well peroxidase-like activity.

Double emission fluorescence probes based on unconventional fluorescent molecules and fluorescein isothiocyanate for ClO− and Cu2+ detection

• A novel strategy is provided to construct double emission fluorescence probes based on unconventional fluorescent molecules. • Fluorescein isothiocyanate, citric acid, and polyethyleneimine were treated hydrothermally to synthesize double emission unconjugated polymer dots ( f-PDs ). • Cu 2+ ions are combined with polyethyleneimine parts of f-PDs to form copper-amine complexes, the resulting internal filtration effect causes quench fluorescence. • ClO − can oxidize hydroxyl groups on the surface of f-PDs , resulting in fluorescence quenching. f-PDs have good water solubility, and high sensitivity. In recent years, unconventional fluorescent molecules without conjugated rings have attracted widespread interest due to their excellent fluorescence properties, simple preparation process, good water solubility and excellent biocompatibility. Dual emission fluorescent probes are usually more accurate and sensitive, for eliminating the influence of environmental factors. This work provides a novel strategy to construct double emission fluorescent probes based on unconventional fluorescent molecules and fluorescein isothiocyanate. The aqueous solution of resulting double emission polymer dots ( f-PDs ) shows two fluorescence emission peaks centered at 440 nm and 510 nm under excitation at 363 nm. According to change of these two peaks after adding ions, Cu 2+ and ClO − are judged quantitatively. Cu 2+ or ClO − are also quench fluorescence of f-PDs linearly, as Cu 2+ combines with polyethyleneimine parts of f-PDs to form complexes, while ClO − oxidize hydroxyl groups on the surface of f-PDs . The detection limits of Cu 2+ and ClO − , in an aqueous solution are 6.7 nM and 14.0 nM, respectively.

A Dual-Emission Fluorescent Ratiometric Probe Based on Bimetallic Lanthanide Complex Interacted in Nanoclay for Monitoring of Food Spoilage

A Dual-Emission Fluorescent Ratiometric Probe Based on Bimetallic Lanthanide Complex Interacted in Nanoclay for Monitoring of Food Spoilage

Multifunctional dual emissive fluorescent probe based on europium-doped carbon dots (Eu-TCA/NCDs) for highly selective detection of chloramphenicol, Hg2+ and Fe3+

In this study, we developed a dual emissive fluorescent nanoprobe based on europium doped carbon dots (Eu-TCA/CDs) for the selective detection of chloramphenicol, Hg2+ and Fe3+ in aqueous medium.

A smart probe for simultaneous imaging of the lipid/water microenvironment in atherosclerosis and fatty liver.

A smart lipid droplet specific fluorescent probe (LDs-DM) with dual-emission in water (706 nm) and oil (535 nm) under single-excitation was prepared for revealing the ultra-structure of the aqueous and lipidic microenvironment in living cells, fatty liver tissues and atherosclerotic plaques without fluorescence emission crosstalk. This work is expected to provide inspiration for designing a novel probe with color switching ability.

A new auspicious scaffold for small dyes and fluorophores

An unprecedented chromophore, based on a nitrogen fused tricyclic heterocycle, is presented. This prototype molecule can be considered a “rigidified” monomethine cyanine dye and the central core is isoelectronic to pyridine-based BODIPY analogues, such as boron difluoride dipyridylmethene. The chromophore was synthesized and its photophysical properties examined. The new molecule can be considered the starting point to develop dyes, fluorophores or dual-emission fluorescent probes with excitation window in the green region of the spectrum.

Dual-Emission Fluorescence Probe Based on CdTe Quantum Dots and Rhodamine B for Visual Detection of Mercury and Its Logic Gate Behavior.

It is urgent that a convenient and sensitive technique of detecting Hg2+ be developed because of its toxicity. Conventional fluorescence analysis works with a single fluorescence probe, and it often suffers from signal fluctuations which are influenced by external factors. In this research, a novel dual-emission probe assembled through utilizing CdTe quantum dots (QDs) and rhodamine B was designed to detect Hg2+ visually. Only the emission of CdTe QDs was quenched after adding Hg2+ in the dual-emission probe, which caused an intensity ratio change of the two different emission wavelengths and hence facilitated the visual detection of Hg2+. Compared to single emission QDs-based probe, a better linear relationship was shown between the variation of fluorescence intensity and the concentration of Hg2+, and the limit of detection (LOD) was found to be11.4 nM in the range of 0–2.6 μM. Interestingly, the intensity of the probe containing Hg2+ could be recovered in presence of glutathione (GSH) due to the stronger binding affinity of Hg2+ towards GSH than that towards CdTe QDs. Based on this phenomenon, an IMPLICATION logic gate using Hg2+/GSH as inputs and the fluorescence signal of QDs as an output was constructed.

A novel dual-excitation and dual-emission fluorescent probe (CQDs-O-NBD) based on carbon quantum dots for detection and discrimination of Cys/Hcy and GSH/H2S in living cells

Cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen sulfide (H2S) are essential active substance in human body. The identification and detection of biothiols and H2S are of great significance for the early diagnosis of certain diseases. In this paper, a new dual excitation and dual emission fluorescent probe, carbon quantum dot-O-7-nitrobenzo-2-oxa-1,3-diazole (CQDs-O-NBD), for the detection of biothiols and H2S was synthesized. The carbon quantum dots (CQDs-OH) (λex/em maxima = 377 nm/467 nm) were synthesized by a microwave-assisted method using hydroquinone as the carbon source. Through the reaction of the phenolic hydroxyl group of the carbon quantum dots and 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl), the CQDs-O-NBD was synthesized. Due to the static quenching (SQ) and the photo-induced electron transfer (PET) from CQDs to NBD, the fluorescence of the CQDs-O-NBD is very weak. After adding biothiols and H2S, the ether bond of the CQDs-O-NBD was broken through nucleophilic substitution reaction, which led to the release of the CQDs-OH (channel 1 is turned on) and generation of a new compound NBD-thiols (channel 2). The CQDs-O-NBD as a probe shows the high selectivity and sensitivity for Cys/Hcy/GSH/NaHS (LOD of 0.24 μM/0.21 μM/0.19 μM/0.18 μM) over other aminos and ions by channel 1. The new formed compounds from NBD and Cys/Hcy have strong fluorescence under 470 nm wavelength light excitation (channel 2 is turned on), while the formed compounds from NBD and GSH/NaHS have no fluorescence (no channel 2), so the CQDs-O-NBD can discriminate Cys/Hcy (LOD: 0.07 μM/0.06 μM) from GSH/NaHS. In addition, the CQDs-O-NBD shows low toxicity and can be applied to the detection of Cys in fetal bovine serum and imaging in living cells.

Ratiometric and reversible detection of endogenous SO2 and HCHO in living cells and mice by a near-infrared and dual-emission fluorescent probe

Abstract The small signal transmitters SO2 can elaborately modulate signal transduction pathways. Endogenous formaldehyde (FA) can toxify protein and DNA as a crosslinking agent besides functions in the aspect of spatial memory and cognitive ability. Both SO2 and FA are tightly associated with neurological disorders, cardiovascular diseases. Therefore, it is significant and challenging to monitor the real-time dynamic fluctuation of SO2 and FA in cells or animals. Toward this end, for the first time, a near-infrared (NIR) dual-emission fluorescent probe (BCou-BP) for SO2 and FA was developed based on the rational combination of benzypylium and benzo[g]coumarin cores through tuning the conjugation and rigidity of the fluorophore units. Thus, this rational design affords the new cationic probe the ratiometric detection ability (F604/F694) toward mitochondrial SO2 with a fast response time of 10 s, as well as toward FA in 170 s. Endogenous FA could restore the fluorescence at 694 nm of BCou-BP due to the capture of SO2 from decomposition of the adduct BCou-BP-SO3H. The powerful probe succeeded in real-time visualizing the dynamic change of endogenous mitochondrial SO2 and FA in living cells and mice.

A simple dual-channel imidazo[1,5-a]pyridine-based fluorescent probe for the discrimination between Cys/Hcy and GSH

A new dual-emission fluorescent probe 4-nitro-7-(4-(1-phenylimidazo [1,5-a]- pyridin-3-yl)phenoxy)benzo [c] (Yin et al., 2017; Jia et al., 2015; Chan et al., 2012) [1,2,5]oxadiazole (IP-NBD) with high sensitivity and selectivity for the detection of cysteine (Cys)/homocysteine (Hcy) and glutathione (GSH) was designed and synthesized. The probe, which exhibits low cytotoxicity and good cell penetration ability, can quickly detect Cys/Hcy with a detection limit as low as 140/180 nM, and has been successfully tested for Cys/Hcy and GSH in cells.

Different fluorescence emitting copper nanoclusters protected by egg white and double-emission fluorescent probe for fast detection of ethanol

Green emitting copper nanoclusters (G-Cu NCs), yellow emitting Cu NCs(Y-Cu NCs), orange emitting Cu NCs (O-Cu NCs) and red emitting Cu NCs(R-Cu NCs) were prepared using chicken egg white as the stabilizer by changing the reaction conditions. This is a green, facile and cheap method to explore different color emitting CuNCs by the same precursor and stabilizers. The G-Cu NCs were employed for the detection of ethanol due to their aggregation induced emission enhancement (AIEE) effect. The fluorescence emission of Cu NCs at 526nm under the excitation of 444nm can be effectively enhanced in the presence of ethanol due to AIEE effect, thus realizing the quantitative determination of ethanol content in the range 5-60%. In addition, a visual dual-emission fluorescence probe with the combination of G-Cu NCs and silicon nanoparticles (Si NPs/G-Cu NCs) was designed to evaluate ethanol content conveniently and rapidly. Desirable linear relationship is observed between ratio of fluorescence intensity (I525/I441) and ethanol content under the excitation of 383nm. Visible color transformation of this probe is observed in the ethanol content range 2-20%. Moreover, the ethanol sensing platforms were applied to the detection and evaluation of the alcohol content of liquor, and the recoveries in liquor were in the range 99.7% to 113%, broadening the applications of Cu NCs and providing a sensitive detection method for ethanol.

Dual-Emissive Probe for Reversible Visualization of ΔΨm Revealing Voltage Heterogeneity in a Single Mitochondrion.

Mitochondrial membrane potential (ΔΨm) is a fundamentally important parameter in eukaryotic cells playing central roles in various vital biological processes. Precise visualization of ΔΨm depends on the robust ratiometric fluorescent probes. In this work, a new dual-emissive fluorescent probe has been fabricated for ratiometric visualization of ΔΨm. The unique probe can form near-infrared emissive aggregates (∼670 nm) in mitochondria with high ΔΨm, which turned to green-emitting monomers (530 nm) with loss of ΔΨm. The reversible changes of ΔΨm can be clearly observed, and the ultralarge emission shift (∼140 nm) is greatly favorable for the clear observation of voltage distribution under a super-resolution microscope. With the robust probe, the heterogenous voltage distribution in a single mitochondrion has been revealed for the first time, which can facilitate the in-depth understanding of fine structures in mitochondria. The cell damages induced by various reagents were successfully visualized using the innovative probe, demonstrating its pronounced potential for biological research.

Ratiometric fluorescence probe of Cu2+ and biothiols by using carbon dots and copper nanoclusters.

A novel dual-emission ratiometric fluorescent probe based on N-doped yellow fluorescent carbon dots (y-CDs) and blue fluorescent copper nanoclusters (CuNCs) was established for quantitative determination of Cu2+ and biothiols. In this work, the Cu2+-(y-CDs) complexes formed by the chelation of y-CDs with Cu2+, showed an absorption peak at 430 nm that not only enhanced the fluorescence of y-CDs through inhibiting photoinduced electron transfer (PET) but also effectively quenched the fluorescence of CuNCs due to Förster resonance energy transfer (FRET). In addition, the chelation of y-CDs with Cu2+ could be inhibited by biothiols that prevented the fluorescence of y-CDs from being enhanced and the fluorescence of CuNCs from being quenched. On account of the changes of ratiometric signal, a dual-emission fluorescence probe for Cu2+ and biothiols determination was achieved. The proposed method exhibited high sensitivity for Cu2+ and biothiols in the ranges of 0.5–100 μM and 0.8–50 μM and the limits of detection (LODs) of Cu2+, glutathione (GSH), cysteine (Cys) and homocysteine (Hcy) were 0.21 μM, 0.33 μM, 0.39 μM and 0.46 μM, respectively. Subsequently, the established strategy presented an application prospect for the detection of Cu2+ and biothiols in real samples.

An Ultrasensitive Turn-On Ratiometric Fluorescent Probes for Detection of Ag+ Based On Carbon Dots/SiO2 and Gold Nanoclusters

In recent years, ratiometric fluorescent probes have been widely used in biochemical sensors and bioimaging due to their accuracy, sensitivity, and visibility. In this paper, we constructed “turn-on” ratiometric fluorescent probes for the detection of Ag+ by coupling carbon dots-silicon spheres composites (named CSs) and gold nanoclusters (AuNCs). The dual-emission fluorescent probes (CSA) exhibited two fluorescence emissions at 448 and 610 nm respectively, under a single excitation of 380 nm. When Ag+ was added, the fluorescence intensity of AuNCs was enhanced thus, quantitative detection could be carried out within the ranges of 0-0.1 μM and 0.1-10 μM. The detection limit of Ag+ was 1.6 nM. Fascinatingly, when the concentration of Ag+ was increased, the fluorescence colour of the CSA ratiometric probes changed from blue to purple and then to pink. More importantly, the CSA composites were utilized to prepare portable agarose hydrogels for the detection of Ag+ by visualization. To the best of our knowledege, this is the first time ratiometric probes sensors have been used to visually detect Ag+. Therefore, this dual-emission ratiometric fluorescent probes have the potential to be applied to the detection of Ag+ in environmental monitoring and food safety assessment. In particularly, this technology can also be extended to other analytes.

A novel dual-excitation and dual-emission fluorescent probe CDs–COO–F for hydrazine detection in aqueous solutions and living cells

In this work, a novel dual-excitation and dual-emission fluorescent probe, CDs–COO–Fluorescein (CDs–COO–F), for the specific detection of hydrazine (N2H4) was designed and synthesized through esterification reaction of carbon dots (CDs) and fluorescein (F). The prepared CDs were characterized by TEM, XPS, XRD and FT-IR and the optical properties of CDs and CDs–COO–F were described by UV–vis and fluorescence spectra. On the other hand, the affecting factors including hydrazine (N2H4) concentration and interfering substances on the hydrazine (N2H4) detection were researched. The high sensitivity and high selectivity of CDs–COO–F in detection hydrazine (N2H4) could be confirmed. Two good linear responses of fluorescence emission intensities of CDs–COO–F at 462 nm and 515 nm as functions of hydrazine (N2H4) concentration were obtained, respectively. The limits of detection hydrazine (N2H4) were 0.504 μM and 0.269 μM under 370 nm and 480 nm excitation wavelength lights, respectively. The detecting mechanism of hydrazine (N2H4) by CDs–COO–F was deduced from the experimental results. Cell imaging and cytotoxicity experiments of CDs–COO–F were measured. The experiment results show that the fluorescent probe CDs–COO–F can be applied to detect hydrazine (N2H4) in aqueous solution and living cells.

Ratiometric visual detection of tetracycline residues in milk by framework-enhanced fluorescence of gold and copper nanoclusters.

We reported a novel dual-emission fluorescence probe fabricated by encapsulating both gold (AuNCs) and copper nanoclusters (CuNCs) into zeolitic imidazolate framework-8 (ZIF-8). Obtained composite (AuCuNCs@MOF) was utilized for ratiometric determination of Tetracycline (Tcy) antibiotic. Under excitation at 400nm, the AuCuNCs@MOF composite displayed two emission peaks at 520 and 650nm which were originated from AuNCs and CuNCs, respectively. Upon the addition of Tcy, the red emission intensity of the nanoparticles at 615nm was significantly decreased, while the green emission at 520nm stayed almost constant which resulted in a clear fluorescence color change from red to green under a UV lamp. The logarithm of the fluorescence ratio against the concentration of Tcy exhibited a satisfactory linear relationship from 20 to 650nM with a detection limit (LOD) of 4.8nM. Current probe was applied for Tcy quantification in milk samples with superior results.