Coumarin Dyes Research Articles

A novel coumarin-based chemosensor for colorimetric detection of Ag(I) ion and fluorogenic sensing of Ce(III) ion

A novel coumarin dye was synthesized, which acts as a chemosensor for selective detection of Ag+ and Ce3+ ions in aqueous solution. Upon addition of Ag+ to the sensor solution a new absorption band centered 580 nm was observed and the color of the solution changed from pale yellow to brown while other metal ions (Cu2+, Hg2+, Zn2+, Li+, Na+, Al3+, Fe3+, Co2+, Ni2+, K+ and Cr3+) did not cause distinct change. The coumarin dye can also be used as a fluorescence turn-on chemosensor for selective detection of Ce3+ over other metal ions including common trivalent metal ions Al3+, Fe3+ and Cr3+ as well as lanthanide metal ions Pr3+, Yb3+, Nd3+ and La3+. Investigation on changes in the intensity of the fluorescence emission band at around 350 nm with the equivalent ratio of Ce3+/sensor (0–1.1) reveals an approximate linear relationship, from which the concentration of Ce3+ ion may be estimated. The detection limit of Ce3+ ion by the sensor is estimated to be 2.07 × 10–7 M.

Ratiometric fluorescence sensing of mercuric ion based on dye-doped lanthanide coordination polymer particles

This work focused on the development of a novel ratiometric fluorescence sensor for detection of Hg2+ by using dye-doped lanthanide infinite coordination polymer (Ln-ICP) particles. The dye-doped Ln-ICP used herein was prepared by self-assemble of adenosine monophosphate (AMP) with Ce3+ and Tb3+ (Ce/Tb-AMP) through self-adaptive chemistry, in which the fluorescent dye coumarin was encapsulated during the assembly process as a guest molecule. Under 310 nm irradiation, the obtained coumarin@Ce/Tb-AMP itself emitted characteristic green luminescence of Tb3+, accompanied with a weak fluorescence at 445 nm originated from coumarin encapsulated in the Ce/Tb-AMP networks. The fluorescence emission of coumarin became strong when it was released to the solution. In the presence of Hg2+, the coumarin@Ce/Tb-AMP was destroyed due to the specific coordination interaction between AMP and Hg2+, which leaded to the release of coumarin to the solution meanwhile. Consequently, the fluorescence of Ce/Tb-AMP was quenched, while that of coumarin enhanced. On the basis of this strategy, we developed a novel ratiometric fluorescent sensor for the detection of Hg2+ by measuring the ratio of fluorescent intensity of the coumarin@Ce/Tb-AMP suspension, which showed a wide linear range from 0.08 to 1000 nM and detection limit of 0.03 nM with high selectivity and sensitivity. Furthermore, the constructed ratiometric fluorescent sensor was successfully applied in detecting Hg2+ in drinking water and human blood serum (HBS) with satisfactory results.

Arm-First Approach toward Cross-Linked Polymers with Hydrophobic Domains via Hypervalent Iodine-Mediated Click Chemistry.

In this work, synthesis of two cross-linked polymeric systems through isoxazoline ring formation using nitrile oxide–acrylate click chemistry has been described. In the first system, styrenic block copolymer with oxime-functionalized middle block was synthesized using S,S′-bis(α,α′-dimethyl-α″-acetic acid)trithiocarbonate as chain-transfer agent using reversible addition fragmentation chain-transfer technique. This block copolymer was further utilized to prepare core cross-linked star polymers by reacting with a four-arm acrylic cross-linker by employing environment-friendly, nontoxic PhI(OAc)2-mediated “click reaction” via the formation of isoxazoline ring. In the second system, two linear styrenic block copolymers, one containing oxime and another containing acrylate group, were reacted to form a cross-linked (CS) polymeric system. Formation of cross-linked polymers and isoxazoline ring was confirmed by Fourier transform infrared spectroscopy, gel permeation chromatography, NMR spectroscopy, and dynamic light scattering studies. Later, we also demonstrated that in aqueous medium these CS polymers produced polymeric nanoparticles (NPs), which can be used as potential carriers of hydrophobic drug molecules. The loading capacity of the hydrophobic domains has been investigated using coumarin dyes with varying hydrophobicity through steady-state and time-resolved spectroscopy studies. The polymeric NPs were also shown to successfully encapsulate a hydrophobic drug doxorubicin.

Dye Tool Box for a Fluorescence Enhancement Immunoassay.

Immunochemical analytical methods are very successful in clinical diagnostics and are nowadays also emerging in the control of food as well as monitoring of environmental issues. Among the different immunoassays, luminescence based formats are characterized by their outstanding sensitivity making this format especially attractive for future applications. The need for multiparameter detection capabilities calls for a tool box of dye labels in order to transduce the biochemical reaction into an optically detectable signal. Here, in a multiparameter approach each analyte may be detected by a different dye with a unique emission color (covering the blue to red spectral range) or a unique luminescence decay kinetics. In the case of a competitive immunoassay format for each of the different dye labels an individual antibody would be needed. In the present paper a slightly modified approach is presented using a 7-aminocoumarin unit as the basic antigen against which highly specific antibodies were generated. Leaving the epitope region in the dyes unchanged but introducing a side group in positon 3 of the coumarin system allowed us to tune the optical properties of the coumarin dyes without the necessity of new antibody generation. Upon modification of the parent coumarin unit the full spectral range from blue to deep red was accessed. In the manuscript the photophysical characterization of the coumarin derivatives and their corresponding immunocomplexes with two highly specific antibodies is presented. The coumarin dyes and their immunocomplexes were characterized by steady-state and time-resolved absorption as well as emission spectroscopy. Moreover, fluorescence depolarization measurements were carried out to complement the data stressing the different binding modes of the two antibodies. The binding modes were evaluated using the photophysics of 7-aminocoumarins and how it was affected in the respective immunocomplexes, namely, the formation of the intramolecular charge transfer (ICT) as well as the twisted intramolecular charge transfer (TICT). In contrast to other antibody-dye pairs reported a distinct fluorescence enhancement upon formation of the antibody-dye complex up to a factor of 50 was found. Because of the easy emission color tuning by tailoring the coumarin substitution for the antigen binding in nonrelevant position 3 of the parent molecule, a dye tool box is on hand which can be used in the construction of competitive multiparameter fluorescence enhancement immunoassays (FenIA).

基于香豆素的荧光传感器及其对次氯酸根的快速检测

基于香豆素的荧光传感器及其对次氯酸根的快速检测

Application of coumarin dyes for organic photoredox catalysis.

Here we report the application of readily prepared and available coumarin dyes for photoredox catalysis, which are able to mimic powerful reductant [Ir(iii)] complexes. Coumarin derivatives 9 and 10 were employed as photoreductants in pinacol coupling and in other reactions, in the presence of Et3N as a sacrificial reducing agent. As the electronic, photophysical, and steric properties of coumarins could be varied, a wide applicability to several classes of photoredox reactions is predicted.

Gamma Ray Effect on the Properties of Coumarin C47 Laser Dye

The research is concerned about studying the absorption spectrum of the solution coumarin dye C47. The chloroform solvent was used with C47 dye in three different concentrations 10-4, 10-5 and 10-6 M. The laser dye solution was prepared by dissolving the required amount of dye in chloroform alcohol, while studying absorption spectrum before and after irradiation with gamma ray by cobalt-60 source 60Co at exposure time, which are 0, 4, 6 and 18 hours with different absorbed doses 0, 136, 204 and 612 Gy. The results show that red shift in the absorption spectrum was increased by increasing the concentration of laser dye solutions , while the increase of gamma dose led to increase the red shift after irradiation, as the exposure period and irradiation dose increased from gamma ray at 60Co source. Furthermore, the decrease in the concentrations of laser dye solutions shifts the absorption spectrum peak towards the short wavelength blue shift.

An anionic iridium(iii) complex as a visible-light absorbing photosensitizer.

In this work, a new anionic Ir(iii) complex (Ir2) was synthesized using coumarin 6 and orotate ligands, and its use as a photosensitizer in photochemical hydrogen (H2) generation was demonstrated. For comparison purposes, we also prepared a known anionic Ir(iii) complex (Ir1) bearing 2-phenylpyridine and orotate ligands, which was previously reported as an emitting material by another research group. The photophysical properties of complexes Ir1 and Ir2 were examined in several solvents including aqueous acetonitrile (CH3CN-H2O), which is frequently used in photocatalytic H2-generating experiments. Ir1 was found to be weakly emissive in CH3CN-H2O, which is probably due to the effect of hydrogen bonding between the orotate ligands and H2O molecules. In sharp contrast, Ir2 exhibited remarkable properties that include strong visible-light absorption (ε = 78 800 M-1 cm-1 at 462 nm), a high phosphorescence quantum yield (50%), and a long-lived excited state (15 μs), even in the same solvent. Actually, Ir2 functioned as a photosensitizer during visible-light-driven H2 generation using sodium ascorbate and a cobalt(iii) diglyoxime complex as the electron donor and water-reduction catalyst, respectively. To the best of our knowledge, this is the first example of the use of an anionic Ir(iii) sensitizer in a photoinduced electron-transfer reaction. The results of this study suggest that Ir2 can be applied to future photochemical H2-generating systems that are based on ion-paired photocatalysts.

Functionalized Carbon Nano-scale Drug Delivery Systems From Biowaste Sago Bark For Cancer Cell Imaging.

Nano-scale carbon systems are emerging alternatives in drug delivery and bioimaging applications of which they gradually replace the quantum dots characterized by toxic heavy metal content in the latter application. The work intended to use carbon nanospheres synthesized from biowaste Sago bark for cancer cell imaging applications. This study synthesised carbon nanospheres from biowaste Sago bark using a catalyst-free pyrolysis technique. The nanospheres were functionalized with fluorescent dye coumarin-6 for cell imaging. Fluorescent nanosytems were characterized by field emission scanning electron microscopy-energy dispersive X ray, photon correlation spectroscopy and fourier transform infrared spectroscopy techniques. The average size of carbon nanospheres ranged between 30 and 40 nm with zeta potential of -26.8 ± 1.87 mV. The percentage viability of cancer cells on exposure to nanospheres varied from 91- 89 % for N2a cells and 90-85 % for A-375 cells respectively. Speedy uptake of the fluorescent nanospheres in both N2a and A-375 cells was observed within two hours of exposure. Novel fluorescent carbon nanosystem design following waste-to-wealth approach exhibited promising potential in cancer cell imaging applications.

Styryl and phenylethynyl based coumarin chromophores for dye sensitized solar cells

A set of coumarin dyes with styryl and phenylethynyl π-bridge at the 3-position were tested for dye-sensitized solar cells (DSSCs). The natural product 6,7-dihydroxycoumarin (Esculetin) was used as starting material. Crucial steps for extension of the conjugated system involved Sonogashira and regioselective Heck arylation reactions, yielding highly fluorescent molecules. The photophysical characterization showed that the extension of conjugation via the alkynyl bridge resulted in redshifted absorption and emission spectra relatively to the parent compound. Electrochemical studies revealed that this derivatization resulted in a marked decrease in HOMO energy levels, which had a marked effect on sensitized solar cell performance. The overall conversion efficiency of the phenylethynyl derivatives proved to be significantly superior (ca. 45%) to the vinyl derivatives, with 6a showing a 2% conversion.

Influence of tagging thiophene bridge unit on optical and electrochemical properties of coumarin based dyes for DSSCs with theoretical insight

Abstract A novel series of coumarin based dyes were designed and synthesised with coumarin donor (D) moiety, various thiophene bridge (Th-π) unit and –CNCHCOOH acceptor (A). The dye sensitized solar cells' (DSSCs) performance, optical and electrochemical properties of coumarin dyes were examined systematically. Moreover, optimization calculations for the geometries of all the coumarin dyes with various Th-bridge units were studied by DFT (density functional theory). CDT-3 dye containing three Th- unit shows the highest short circuit current (Jsc = 15.14 mA/cm2) and efficiency is 6.02% under 1 sunlight (100 mW/cm2, AM1.5) illumination. The DSSCs devices with all three coumarin dyes exhibit good, long term stability up to 500hr.

Fluorescent vinyl and styryl coumarins: A comprehensive DFT study of structural, electronic and NLO properties

Nonlinear optical properties of 3-styryl and 3-vinyl coumarin dyes have been investigated with Density Functional Theory (DFT) using global hybrid (GH) and range-separated hybrid (RSH) functionals. The performance of GHs - B3LYP, BHHLYP, PBE0, M06, M06L, M062X, and M06HF and RSHs - CAM-B3LYP, HISSbPBE, HSEH1PBE, wB97, wB97X, and wB97XD in combination with 6-311++G(d,p) basis set has been analyzed. Estimated (hyper) polarizability ( $$\alpha _{0}, \beta _{0})$$ obtained from the GHs - M06, M062X and PBE0 are in agreement with each other. The RSHs - wB97 and wB97X estimate very close values of $$\beta _{0}$$ . The $$\beta _{0}$$ value of 3-styryl and 3-vinyl coumarins reaches the maximum as the bond length alternation and bond order alternation parameters tend to zero. Natural bond orbital analysis shows there is extensive charge transfer in the excited state leading to large value of $$\beta _{0}$$ . The vibrational contribution to $$\alpha _{0}$$ and $$\beta _{0}$$ is significantly less when the donor is methoxy group and acceptor is nitro group in the 3-styryl coumarin. The dye, (E)-7-(diethylamino)-3-(4-nitrostyryl)-2H-chromen-2-one (3c) is found to give the highest NLO response. An increasing electrophilicity originating from the decreased HOMO-LUMO band gap leads to an increase in $$\alpha _{0} $$ and $$\beta _{0}$$ in all the cases. JCSC-D-17-00839R1 Synopsis - The NLO properties of 3-styryl and 3-vinyl coumarin dyes have been investigated thoroughly with the help of DFT using global hybrid (GH) and range-separated hybrid (RSH) functionals. The performance of GHs and RSHs in combination with 6-311++G(d,p) basis set has been analyzed. Calculated BLA/BOA index, NBO analysis, electrophilicity index and HOMO-LUMO gap are good agreement with the $$\alpha _{0}$$ and $$\beta _{0}$$ .

Chromatographic Properties of Minimal Aspect Ratio Monolithic Silica Columns.

We report on a study wherein we synthesized TMOS-based silica monolithic skeletons in capillaries with an i.d. of 5 and 10 μm to produce skeleton structures with very low capillary-to-domain size aspect-ratios. These structures include the absolute minimal aspect-ratio case of a monolithic structure whose cross-section only contains a single node point. With domain-sized based reduced plate heights running as low as hmin = 1.3-1.5 for retained coumarin dyes providing a retention factor of k = 0.6-1.0, the study confirms the classic observation that ultralow aspect ratio columns generate a markedly lower dispersion than columns with a larger aspect ratio made in the past by Knox, Jorgenson, and Kennedy for the packed bed of spheres, but now for silica monoliths. The course of the reduced van Deemter curves, and more specifically the ratio of A-term versus C-term band broadening, could be interpreted in terms of the width and persistence length of the velocity bias zones in the columns. Considering the overall kinetic performance, it is found that the two best performing structures are also the structures with the lowest number of domains or node points, that is, with the lowest capillary-to-domain size aspect-ratio and, hence, resembling closest to the open-tubular format, which remains confirmed as the column format with the best kinetic performance. This is quantified by the fact that the minimal impedance values (order of Emin = 100) of the best performing ultralow aspect ratio monolithic columns are still significantly larger than the Emin values for the reference open-tubular columns (order of Emin = 15-20).

Silicon microfluidics: An enabling technology for life sciences application

Abstract In this paper we review the silicon microfabrication process that has been developed for various life science applications over the last several years. Silicon microfabrication is a key enabling technology in the developing personalized point of care or point of need systems. Silicon microfabrication allows for accurate control of fine features and it can combine active and passive components within a single chip. It is also very reliable, repeatable and it benefits from cost reduction due to mass production capabilities Depending on the application, we have fabricated devices with either a single silicon etch or a two-step approach. Single step etches are typically 250–280μm deep. Two-step etching, the shallow features are 50μm while deeper are 250μm. We have developed an optimized deep silicon etch process that gives very straight profiles with minimum loss of critical dimension (CD) for different features. The minimum CD is 3μm while the largest features are 500μm wide The etching was done an SPTS Rapier DRIE system. We describe the working principles of the various components in the system including PCR and micropillar filters. The filter has been used for high performance liquid chromatography (HPLC). It exhibits very low broadening of the components travelling through it and separation of a mixture of coumarin dyes is efficiently performed in a very short time. A micro PCR chamber with thermal isolation to the surrounding silicon is characterized and DNA amplification is achieved.

Structures and photoluminescence properties of organic-inorganic hybrid materials based on layered rare-earth hydroxides

Two kinds of coumarin derivatives, 7-hydroxy coumarin and 7-hydroxy-4-methyl coumarin, were intercalated into the layered europium hydroxide by ion exchange reaction. The two organic compounds, despite with the same basic structure of benzopyrone but only varied substituent groups, demonstrated much different intercalation structures. The 7-hydroxy coumarin molecules may deposite on the external surface of the layers and 7-hydroxy-4-methyl coumarin molecules corresponded to a vertical mono-layered arrangement. In addition, co-intercalation of surfactant 1-octane sulfonic acid sodium with coumarin anions into layered europium hydroxide can enlarge the interlayer distance, both of the coumarin anions located vertically in the interlayer. The thermal stability of organics was enhanced after intercalation. The combination of the coumarin anions with the positively-charged layers generated hybrid materials exhibiting versatile luminescence properties. In solid state, the luminescence of the organics and Eu3+ were co-quenched for 7-hydroxy coumarin composites, but surfactant co-intercalated 7-hydroxy-4-methyl coumarin composite showed strong violet emission. In formamide, all of the composites displayed blue emission. The energy transfer between Eu3+ and organics and the change of microenvironment were proposed to account for the versatile luminescence properties. This work benefits the improvement of stability and fluorescence property of coumarin dyes and offers a beneficial approach to fabricate organic-inorganic hybrid materials with controllable structures and luminescence properties.

Modulation of Protolytic Equilibrium of Bichromophoric Coumarin‐30 Dye with Cucurbit[8]uril Encapsulation

AbstractHost‐guest interaction of macrocyclic receptor, cucurbit[8]uril (CB8), with neutral bichromophoric coumarin 30 (C30) dye has been investigated using various spectroscopic tools. Absorption and fluorescence emission results along with 1H NMR data have demonstrated the existence of host‐guest complex of C30 dye with CB8 host in a 1:2 and 3:2 (CB8:C30) stoichiometries. Comparative studies with the photophysical aspects of the protonated C30 dye (at pH 3) confirmed that interaction of neutral C30 dye (at pH 7) with CB8 has led to the host assisted protonation of C30 in the CB8:C30 complex, registering an upward supramolecular pKa shift of about 3 units. The 3:2 stoichiometric complex exhibits strong excimer emission and is dictated by the structural features of C30. Due to this complexation not only we accomplish modulation in the photophysics of the dye, but also it enhances the aqueous solubility of C30, especially at pH 7. Taking advantage of CB8 assisted tunable pKa shift, currently we are pursuing the prospects of using photostable coumarin dyes for cellular imaging studies as well as their applicability as aqueous dye laser systems.

Photoinduced formation of the laser dye coumarin 6 from its dihydro derivatives

The dihydro form of the laser dye Coumarin 6 and its acylated derivatives undergo photoinduced transformations with Coumarin 6 formation. The reactions go easily both in organic solvents and in polymer films with a high increase of fluorescence. Irreversibility of the reaction provides potential use of the new photosensitive media for optical information recording and sensing technologies.

Preparation and evaluation of mesoporous silica layers on radially elongated pillars

The present paper describes the application of a sol-gel procedure on radially elongated pillars (REPs) using tetramethoxysilane and methyltrimethoxysilane. After octadecylsilylation, the quality of the porous layered REP (PLREP) columns was evaluated by in-situ determination of migration velocities and band broadening of coumarin dyes with fluorescence microscopy in reversed-phase liquid chromatography. Based on the increase in retention due to the sol-gel process, an increase in accessible specific surface by a factor of 112 was observed. Argon physisorption measurements on bulk monoliths prepared with the same method revealed a predominant pore size of 91Å. Plate heights as low as 0.4–0.8μm (k=0–1.97) could be obtained thanks to the very low dispersion of the REP format and to the fact that the applied silica layer was conformally and uniformly deposited on the flow-through channels. A kinetic plot analysis demonstrated that the studied PLREP column will deliver more theoretical plates per unit of time than a 5μm core shell packed bed when more than 1.0×104 theoretical plates are required.

Monitoring of nanoclay–protein adsorption isotherms via fluorescence techniques

The investigation of nanoparticles and their interaction with bio-macromolecules have become an important issue; the widely discussed protein corona around nanoparticles and their biological fate in general have drawn particular attention. Here, we focus on nanoclay dispersions and the use of solvatochromic fluorescent dyes (Dansyl and Coumarin 153) for monitoring the interaction with two model proteins, bovine serum albumin and β-lactoglobulin. On one hand, these dyes are poorly emissive in water, but experience a boost in their fluorescence when adsorbed into the hydrophobic domains of proteins. On the other hand, (nano)clays and clay minerals have previously been investigated in terms of their individual protein adsorption isotherms and their usefulness for the solubilization of water-insoluble dyes into an aqueous environment. In the following, we have combined all three individual parts (nanoclay, fluorophore and protein) in dispersions in a wide range of concentration ratios to systematically study the various adsorption processes via fluorescence techniques. In order to clarify the extent of dye diffusion and adsorption-desorption equilibria in the investigations, nanoclay hybrids with an adsorbed dye (Coumarin 153) and a covalently conjugated dye (Dansyl) were compared. The results suggest that the fluorescence progression of protein titration curves correlate with the amount of protein adsorbed, matching their reported adsorption isotherms on hectorite clays. Furthermore, experimental data on the protein monolayer formation around the nanoclays could be extracted due to only minor alterations of the dispersions’ optical quality and transparency. In this manner, a fluorescence-based monitor for the formation of the globular protein layer around the nanoclay was realized.

Broadband plasmonic silver nanoflowers for high-performance random lasing covering visible region

Abstract Multicolor random lasing has broad potential applications in the fields of imaging, sensing, and optoelectronics. Here, silver nanoflowers (Ag NF) with abundant nanogaps are fabricated by a rapid one-step solution-phase synthesis method and are first proposed as effective broadband plasmonic scatterers to achieve different color random lasing. With abundant nanogaps and spiky tips near the surface and the interparticle coupling effect, Ag NFs greatly enhance the local electromagnetic field and induce broadband plasmonic scattering spectra over the whole visible range. The extremely low working threshold and the high-quality factor for Ag NF-based random lasers are thus demonstrated as 0.24 MW cm−2 and 11,851, respectively. Further, coherent colorful random lasing covering the visible range is realized using the dye molecules oxazine (red), Coumarin 440 (blue), and Coumarin 153 (green), showing high-quality factor of more than 10,000. All these features show that Ag NF are highly efficient scatterers for high-performance coherent random lasing and colorful random lasers.