Coumarin 6H Research Articles

Coumarin 6H-fused fluorescent probe for highly sensitive detection of coralyne using oligonucleotide-modified silver nanoparticles.

In this study, a novel, rapid, and sensitive fluorescence sensing platform was developed for the detection of coralyne (COR) by the conjugation of coumarin 6H (C6H) fluorescent dye with oligonucleotide-modified silver nanoparticles [(dT)32-AgNPs]. In the presence of COR, a remarkable and rapid decrease in the fluorescence signal of the probe with a quenching efficiency of around 62% was observed. The quenching response of the system towards COR was possibly due to the displacement of thymidine-rich deoxyoligonucleotides by COR on the surface of AgNPs. The complementary experiments with an adenine-rich single strand as well as with two different secondary structures (i.e., duplex and triplex) revealed a favorable sequence specificity of the sensing platform. The influence of key parameters including the incubation time and temperature was evaluated and optimized to achieve the highest performance. The linear range of 10-183nM with a correlation coefficient of R = 0.9982 and a limit of detection of 5.24nM were obtained under the optimized conditions. The selectivity of the proposed probe towards COR was revealed by the evaluation of its response to other small molecules that have molecular structures similar to COR. Finally, the successful applicability of the system was shown with the obtained average recoveries in the range of 87.28-104.52% in human urine samples.

Mechanism of interaction of aminocoumarins with reaction medium during cationic photopolymerization of triethylene glycol divinyl ether

Applicability of a series of coumarin derivatives as fluorescent probes for monitoring progress of cationic photopolymerization processes by Fluorescence Probe Technique (FPT) has been studied using triethylene glycol divinyl ether as a model monomer and diphenyliodonium hexafluorophospate as a cationic photoinitiator. The following coumarins were evaluated: Coumarin 1, Coumarin 6H, Coumarin 102, Coumarin 120, Coumarin 151, Coumarin 343 and Coumarin 466. It has been found that despite the presence of an amino group in their structure, at low concentrations of the order of 0.1%, the Coumarins 1, 102, 343 and 466 can be used as the fluorescent probes for the cationic photopolymerization, while Coumarin 343 exhibits the best performance. At high concentrations, the aminocoumarins slow down the photopolymerization rate and extend induction period. All of the aminocoumarins are applicable as long-wavelength sensitizers for diphenyliodonium photoinitiators, enabling photopolymerization at the irradiation wavelengths, where the photoinitiator does not absorb. At short wavelengths, where both photoinitiator and probe absorb light, and at the probe concentrations below 0.1%, Coumarin 343 and Coumarin 1 accelerate the cationic photopolymerization by supplying an additional route for the photoinitiator cleavage beside its direct cleavage upon light absorption. The direct initiation and sensitization mechanisms are proposed.

In situ temperature-modulated microscopy observation of two-phase co-existing states of coumarin and coumarin derivative in melting

Coumarin (C9H6O2) and coumarin derivative, coumarin 6H (C15H15NO2) samples were observed with a polarizing microscope at and around the melting points. The states of the two samples are crystalline at room temperature. When the temperature of the Coumarin sample was raised and a part was melted, the crystalline phases coexisted with the liquid phase. The crystal surface coexisting with the liquid phase went through a repetition of melting and crystallization on slightly modulating the sample temperature. The two-phase coexisting state was observed with a digital camera attached to a microscope. The changes in the number of pixels in the crystal part of the photographed image showed Debye relaxation with temperature change. It was found that the relaxation time was 4.9 s when the number of pixels decreased due to surface melting or increased due to surface crystallization. This relaxation time was in good agreement with that of the dynamic-specific heat measured by AC calorimetry. The coumarin 6H microcrystal also coexisted with the melt in a temperature range at and around the melting point. The change in the number of pixels of the coumarin 6H crystal part showed Debye relaxation with respect to the temperature, and the relaxation time was 15 s, which was the same as the relaxation time of the dynamic-specific heat measured in the melting temperature range of coumarin 6H.

Plasmon-enhanced fluorescence in nanomolar dye solution using combination of core-shell nanostructures of various shell thicknesses

Enhancement in fluorescence of samples in solution phase is very crucial for many practical applications. Herein, we report the fluorescence enhancement of a nanomolar solution using Ag core-silica shell nanostructures synthesized independently. Coumarin 6H dye solution has been taken as a case study. Three different Ag core – silica shell nanostructure solutions were prepared by varying the amount of reagent in Stöber method. The core-shell nanostructures were characterized by atomic force microscopy, dynamic light scattering, and UV–Visible spectrophotometry. The maximum values of fluorescence enhancement (ηmax) were found to be 2.5, 4.3, and 1.5 when respective solutions with average nanoshell thicknesses of 2.4, 16.7 and 28.3 nm were used individually. However, the value of ηmax increased by an order (ηmax ~13) when the mixture of the nanoshell solutions was used. The reason behind the improvement in η was ascribed to the optimization in the values of the distance (r) between nanoshell and dye molecules as well as the separation (d) between the nanoshells. This report, as we believe, will enable the scientific community in obtaining better enhancement in the fluorescence signal of labeled proteins and fluorescent molecules in aqueous media with ease.

Role of Dispersive Fluorous Interaction in the Solvation Dynamics of the Perfluoro Group Containing Molecules.

Perfluoro group containing molecules possess an important self-aggregation property through the fluorous (F···F) interaction which makes them useful for diverse applications such as medicinal chemistry, separation techniques, polymer technology, and biology. In this article, we have investigated the solvation dynamics of coumarin-153 (C153) and coumarin-6H (C6H) in ethanol (ETH), 2-fluoroethanol (MFE), and 2,2,2-trifluoroethanol (TFE) using the femtosecond upconversion technique and molecular dynamics (MD) simulation to understand the role of fluorous interaction between the solute and solvent molecules in the solvation dynamics of perfluoro group containing molecules. The femtosecond upconversion data show that the time scales of solvation dynamics of C6H in ETH, MFE, and TFE are approximately the same whereas the solvation dynamics of C153 in TFE is slow as compared to that of ETH and MFE. It has also been observed that the time scale of solvation dynamics of C6H in ETH and MFE is higher than that of C153 in the same solvents. MD simulation results show a qualitative agreement with the experimental data in terms of the time scale of the slow components of the solvation for all the systems. The experimental and simulation studies combined lead to the conclusion that the solvation dynamics of C6H in all solvents as well as C153 in ETH and MFE is mostly governed by the charge distribution of ester moieties (C═O and O) of dye molecules whereas the solvation of C153 in TFE is predominantly due to the dispersive fluorous interaction (F···F) between the perfluoro groups of the C153 and solvent molecules.

Reaction-based fluorescent turn-on probe for selective detection of thiophenols in aqueous solution and living cells

A novel turn-on florescent probe based on a nucleophilic substitution reaction was developed for the detection of thiophenols in aqueous solution and in living cells. In this probe, 10-hydroxyl derivative of coumarin 6H was selected as fluorophore, 2, 4-dinitrophenlate moiety acted simultaneously as recognition unit and fluorophore quencher. This probe features a remarkable large Stokes shift (128 nm) and shows a highly selective detection process for thiophenols with significant fluorescence turn-on response. Notably, biothiols, aliphatic thiols, amino acids and reducing anions do not interfere with the sensing of thiophenols. The probe shows good linearity ranges with low detection limit of 36 nM for thiophenols. More importantly, it was successfully applied for practical detection of thiophenols in real water samples with a good recovery and imaging of thiophenols in living cells, demonstrating its practical application in environmental samples and biological systems.

Solvent organization around the perfluoro group of coumarin 153 governs its photophysical properties: An experimental and simulation study of coumarin dyes in ethanol as well as fluorinated ethanol solvents.

The self-aggregation property of the perfluoro group containing molecules makes it important in the research fields of biology and polymer and organic synthesis. In the quest of understanding the role of the perfluoro group on the photophysical properties of perfluoro-containing molecules in biologically important fluoroethanol solvents, we have applied photophysical as well as molecular dynamics simulation techniques to explore the properties of perfluoro groups containing molecule coumarin-153 (C153) in ethanol (ETH), monofluoroethanol (MFE), difluoroethanol (DFE), and trifluoroethanol (TFE) and compared them with the molecules without perfluoro moiety, namely coumarin-6H (C6H) and coumarin-480 (C480). In contrast to C6H and C480, the excited state lifetime of C153 in fluorinated ETHs is not monotonic. The excited state lifetime of C153 decreases in MFE and DFE as compared to ETH, whereas in TFE, it increases as compared to MFE and DFE. Molecular dynamics simulation reveals that the carbon terminal away from the OH group of fluorinated ETHs has a preferential orientation near the perfluoro (CF3) group of C153. In MFE and DFE, the CF3 group of C153 prefers to have a CF2-F⋯H -(CHF) type of electrostatic interaction over CF2-F⋯F -(CH2) kind of dispersion interaction which increases the rate of nonradiative decay, probably due to the electrostatic nature of the CF2-F⋯H -(CHF) hydrogen bond. On the other hand, in TFE, C-F⋯ F-C type of dispersion interaction, also known as fluorous interaction, takes place between the CF3 groups of C153 and TFE which decreases the rate of nonradiative rate as compared to MFE and DFE, leading to the increased lifetime of C153 in TFE. Photophysical and MD simulation studies clearly depict that the structural organization of solvents and their interaction with the fluorocarbon group are crucial factors for the photophysical behavior of the fluorocarbon containing molecules.

Applicability of quinolizino-coumarins for monitoring free radical photopolymerization by fluorescence spectroscopy

Applicability of commercially available 2,3,5,6-1H,4H-tetrahydro-quinolizino[9,9a,1-gh]coumarin (Coumarin 6H) and its 9-methyl (Coumarin 102), 9-trifluoromethyl (Coumarin 153) and 10-carboxy (Coumarin 343) derivatives as fluorescent molecular probes for monitoring progress of free radical photopolymerization of several acrylic and methacrylic monomers by Fluorescence Probe Technique (FPT) has been tested. The progress of the photopolymerization was monitored using a specially designed cure monitoring system. It was found that all the quinolizino-coumarins shifted their fluorescence spectra towards shorter wavelengths with progress of polymerization, which enabled monitoring the progress in terms of fluorescence intensity ratios as the progress indicator. Coumarin 6H turned out to be the most sensitive to changes occurring during polymerization. Coumarin 102 and Coumarin 153 exhibit only about 20% lower sensitivity than that of Coumarin 6H, so those are also good enough for the cure monitoring of acrylic monomers, except for tetraethylene glycol diacrylate, where the quinolizino-coumarins response was disturbed by some fluorescent side product. Moreover, it has been found that the FPT technique has some limitations in the case of monofunctional monomers.

Non-covalent interactions of coumarin dyes with cucurbit[7]uril macrocycle: modulation of ICT to TICT state conversion

Non-covalent interaction of coumarin laser dyes, namely coumarin-1 (C1), coumarin-481 (C481) and coumarin-6H (C6H), with a versatile macrocyclic host molecule cucurbit[7]uril (CB7), has been investigated in aqueous solution using photophysical methods. Steady-state and time-resolved fluorescence studies illustrate significant enhancements/modifications in the fluorescence yields, lifetimes and spectral features of C1, C481 and C6H on interaction with CB7, and are assigned to 1 : 1 complex formation between the dyes and the CB7 host. The complex formation is mainly driven by charge-dipole interaction, as evident from the binding constant values (K ~ 10(4)-10(5) M(-1)). The large changes in the excited state behaviour of C1 and C481 as compared to C6H in the presence of CB7 indicate that CB7 binds C1 and C481 through the encapsulation of the 7-N,N'-diethylamino group of the dyes and the structural rigidity imposed by this interaction dramatically alters the excited state properties of the dyes by preventing the conversion of their emissive intramolecular charge transfer (ICT) state to the non-radiative twisted intramolecular charge transfer (TICT) state. The present results direct towards the probable supramolecular approach using water soluble macrocyclic CB7, in the development of aqueous dye laser systems in the blue-green region.

C213 複合感圧塗料計測の低速風洞試験への適用

We have developed a bi-luminophor pressure-sensitive paint (Bi-PSP) to correct the temperature dependence of pressure-sensitive paint. The Bi-PSP is composed of two sensor molecules, PtTFPP and Coumarin 6H (C6H), and Poly-IBM-co-TFEM was used as a binder. C6H was added as a temperature-sensitive dye. The luminescent peak-wavelength of C6H was approximately 460 nm and clearly separated from that of PtTFPP (650 nm), indicating that the luminescence of two dyes were not optically interfered with each other. Temperature was determined from the luminescent image of C6H, and the temperature dependence of PtTFPP was corrected by using the calculated temperature. The new paint was applied to low-speed test for evaluating the performance of Bi-PSP system. As a result, the pressure values acquired by the Bi-PSP agreed with pressure tap data, providing that Bi-PSP was effective in correcting the temperature dependence of PSP.

Two-color (two-photon) excitation fluorescence with two confocal beams and a Raman shifter

Two-color (two-photon) excitation fluorescence (2CF) with two confocal excitation beams is demonstrated with a Raman shifter as excitation light source. Coumarin 6H dye sample (peak absorption≈394 nm, peak fluorescence≈490 nm) is excited using the first two Stokes outputs (683, 954 nm, two-color excitation=398 nm) of a Raman shifter pumped by a 6.5 ns-pulsed 532 nm-Nd:YAG laser (repetition rate=10 Hz). The two Stokes pulses overlap for about 6 ns and two-color fluorescence is generated even with focusing objectives of low numerical apertures (NA<0.4). We observed the linear dependence of the two-color fluorescence signal with the product of the average intensities of the two Stokes excitation beams. The two-color fluorescence distribution is strongly localized around the common focus of the confocal excitation beams.

The passively mode locked coumarin 6H ring dye laser

A colliding pulse mode locked ring dye laser is described in which Coumarin 6H was passively mode locked using 3, 3'-diethyl oxacarbocyanine iodide (DOCI). Pulses of less than 500 fs duration were obtained from 492 to 507 nm, the shortest pulses being of 110 fs at 497 nm.