Blue Monomer Research Articles

A novel ratiometric fluorescent probe through aggregation-induced emission and analyte-induced excimer dissociation

Ratiometric fluorescent sensing can minimize interfering effects and thus allow for more accurate and quantitative readouts. Ratiometric sensing can be achieved by adopting several mechanisms such as energy transfer and introduction of reference dye. Herein, we report a novel and facile approach for realizing fluorescent ratiometric sensing, which functions through aggregation-induced emission and analyte-induced excimer dissociation. For this sensing system, the fluorophore 9-anthraldehyde in its good solvent exhibits no monomer emission due to intramolecular charge transfer from anthracene moiety to aldehyde group; while in poor solvent such as water, 9-anthraldehyde molecules tend to aggregate and form excimers, which display yellow-green excimer emission. The presence of sulfite anions transforms the aldehyde groups into negatively charged ones in aqueous solution; this causes the excimers’ dissociation, makes the fluorophores exhibit blue monomer emission, and thereby realizes the ratiometric sensing for sulfite ion. The system shows a large emission wavelength separation (∼100nm) as well as highly selective and sensitive detection for sulfite with the detection limit of 3.19μM. Moreover, it can be applied to real samples such as red wine, beer and rain water.

Tuning of the emission chromaticity of Eu, Gd, Be-containing copolymers

Eu, Gd, Be-containing copolymers were synthesized through copolymerization of reactive complexes with methyl methacrylate (MMA). Their structure was characterized by FT-IR and UV analysis. The glass transition temperature Tg of the copolymers was 24°C higher than that of PMMA. XRD analysis indicates that the complexes were bonded and dispersed uniformly in polymer matrix. The copolymers showed the emission peaks of red, green and blue monomers under the UV excitation of 365nm. When the feed ratio of Eu, Gd, Be was 1.5:15:2, the CIE coordinate was calculated as (0.34, 0.33), being located in white light range, and the relative quantum yield (ηS) was calculated to be 0.112. Therefore, this kind of luminescent material is promising for application in white light-emitting diodes.

High color rendering index and chromatic‐stable white organic light‐emitting diodes with single‐host double emissive layer structure

In this paper, we successfully demonstrated high color rendering index (CRI) and color stable white organic light‐emitting diodes (WOLEDs) based on a hole‐type single‐host double emissive layer (EML) structure. By combining the yellow phosphorescent emission with the blue monomer and red excimer emission of platinum [1,3‐difluoro‐4,6‐di(2‐pyridinyl)benzene]chloride (Pt‐4), the devices exhibited a maximum CRI of 93, which was attributed to the perfect spectrum complement and the relative intensity adjustment of each emission peak. Meanwhile, the WOLEDs were very stable and showed a slight color coordinate shift of (±0.007, ±0.004) over a wide range of driving voltages from 4 to 10 V. The use of the double EML structure effectively confines the exciton generation zone in the Pt‐4 EML, thus, the white‐light emission comes from the energy transfer from host to Pt‐4 and then to yellow phosphor, which is less affected by the driving conditions.

Bright Blue and White Electrophosphorescent Triarylboryl‐Functionalized C^N‐Chelate Pt(II) Compounds: Impact of Intramolecular Hydrogen Bonds and Ancillary Ligands

New blue and blue‐green phosphorescent C^N chelate Pt(II) compounds that contain a dimesitylboryl‐functionalized phenyl‐1,2,3‐triazole ligand (Bptrz) are synthesized. The influence of three different ancillary ligands, namely acetylacetonato (acac), picolinate (pic) and pyridyl‐1,2,4‐triazolyl (pytrz), on phosphorescence quantum efficiency and excimer emission is examined. Pt(II) compounds with a p‐Bptrz ligand consistently emit a blue‐green color with an emission wavelength = 490–500 nm while those with a m‐Bptrz ligand emit a blue color with λem = 450–460 nm and a quantum efficiency as high as 0.97. In addition to the blue monomer emission peak, Pt(m‐Bptrz)(pytrz) compounds display an excimer emission peak at ∼550 nm in a solid matrix whose intensity is dependent on the substituent group on pytrz and the doping concentration. As a result of the monomer and excimer emission, bright white phosphorescence is observed for several members of Pt(m‐Bptrz)(pytrz) compounds. Intramolecular CH···N hydrogen bonds are found to play an important role in the high stability and high phosphorescent quantum efficiency of Pt(m‐Bptrz)(pytrz) compounds. Single‐dopant blue and white electrophosphorescent devices using Pt(m‐Bptrz)(CF3‐pytrz‐Me) or Pt(m‐Bptrz)(t‐Bu‐pytrz‐Me) as the emitter are successfully fabricated. White electroluminesence devices with external quantum efficiency of 15.6% and CIE (xy) of 0.31, 0.44 are achieved.

Photoacoustic lifetime contrast between methylene blue monomers and self-quenched dimers as a model for dual-labeled activatable probes.

Activatable photoacoustic probes efficiently combine the high spatial resolution and penetration depth of ultrasound with the high optical contrast and versatility of molecular imaging agents. Our approach is based on photoacoustic probing of the excited-state lifetime of methylene blue (MB), a fluorophore widely used in clinical therapeutic and diagnostic applications. Upon aggregation, static quenching between the bound molecules dramatically shortens their lifetime by three orders of magnitude. We present preliminary results demonstrating the ability of photoacoustic imaging to probe the lifetime contrast between monomers and dimers with high sensitivity in cylindrical phantoms. Gradual dimerization enhancement, driven by the addition of increasing concentrations of sodium sulfate to a MB solution, showed that lifetime-based photoacoustic probing decreases linearly with monomer concentration. Similarly, the addition of 4 mM sodium dodecyl sulfate, a concentration that amplifies MB aggregation and reduces the monomer concentration by more than 20-fold, led to a signal decrease of more than 20 dB compared to a solution free of surfactant. These results suggest that photoacoustic imaging can be used to selectively detect the presence of monomers. We conclude by discussing the implementation of the monomer-dimer contrast mechanism for the development of an enzyme-specific activatable probe.

White organic light-emitting diodes based on a combined electromer and monomer emission in doubly-doped polymers

We report on white organic light-emitting diodes (WOLEDs) based on polyvinylcarbazole (PVK) doped with 1,1-bis((di-4-tolylamino)phenyl)cyclohexane (TAPC) and perylene, and investigate the luminescence mechanism of the devices. The chromaticity of light emission can be tuned by adjusting the concentration of the dopants. White light with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.33, 0.34) is achieved by mixing the yellow electromer emission of TAPC and the blue monomer emission of perylene from the device ITO/PVK: TAPC: perylene (100:9:1 in wt.) (100 nm)/tris-(8-hydroxyquinoline aluminum (Alq3) (10 nm)/Al. The device exhibits a maximal luminance of 3727 cd/m2 and a current efficiency of 2 cd/A.

Study on the Structure and Liquid Crystal Behavior of Cyclohexane Liquid Crystal Monomer

Chemical structure and liquid crystal behavior of mesogenic monomer(Trans, trans)-4-propyl-4’-vinyl- bicyclohexane(3HHV) with platelet texture of a blue phase and mesogenic monomer(Trans, trans)-4-propyl-4’-propenyl –bicyclohexane(4HHV) with cholesteric phase were studied. The chemical structure of mesogenic monomers were determined by Fourier transform infrared spectroscopy, and Hydrogen-nuclear magnetic resonance spectra. Liquid crystal behavior of mesogenic monomers were analyzed by polarizing optical microscopy and X-ray diffraction. Thermal properties of mesogenic monomers were researched by differential scanning calorimetry. The results were that: 3HHV showed the platelet texture of a blue phase was considerably different from single color texture of blue phase we always refer to, and assuredly belong to a new kind of blue phase liquid crystal. These two kinds of cyclohexane liquid crystal monomer also showed good thermal stability.

The synthesis, characterization and melting properties of thiophene-containing dithiocarboxylate complexes of nickel(II)

The reactions of a series of 5-alkyl-2-thiophenedithiocarboxylates with nickel(II) chloride afforded two types of complexes, blue nickel(II) complexes with two terminal dithiocarboxylate ligands, [Ni(S 2CTR) 2] and violet nickel(II) complexes with perthio- and dithiocarboxylate ligands, [Ni(S 2CTR)(S 3CTR)] (where T = 2,5-disubstituted thiophene, R = C n H 2 n+1 , n = 4, 6, 8, 12, 16). The blue monomers are preferred for the shorter chains (C 4 and C 6) and the violet compounds form exclusively for the longer chains (C 8, C 12, and C 16) in the alkylthiophene complexes. In addition to the above series, [Ni(S 2CTCH 3) 2], was prepared in a one-pot reaction in THF and both the blue and violet products were isolated. It was possible to convert the blue complexes [Ni(S 2CTR) 2] (R = butyl, hexyl) into the corresponding violet complexes [Ni(S 2CTR)(S 3CTR)] after stirring in THF solutions for prolonged periods of time. Liquid-crystalline properties of these complexes were examined by DSC and POM. The violet complexes with C 8 and C 12 alkyl chains showed liquid-crystalline properties.

Structure of GlnK1 with bound effectors indicates regulatory mechanism for ammonia uptake

A binary complex of the ammonia channel Amt1 from Methanococcus jannaschii and its cognate P(II) signalling protein GlnK1 has been produced and characterized. Complex formation is prevented specifically by the effector molecules Mg-ATP and 2-ketoglutarate. Single-particle electron microscopy of the complex shows that GlnK1 binds on the cytoplasmic side of Amt1. Three high-resolution X-ray structures of GlnK1 indicate that the functionally important T-loop has an extended, flexible conformation in the absence of Mg-ATP, but assumes a compact, tightly folded conformation upon Mg-ATP binding, which in turn creates a 2-ketoglutarate-binding site. We propose a regulatory mechanism by which nitrogen uptake is controlled by the binding of both effector molecules to GlnK1. At normal effector levels, a 2-ketoglutarate molecule binding at the apex of the compact T-loop would prevent complex formation, ensuring uninhibited ammonia uptake. At low levels of Mg-ATP, the extended loops would seal the ammonia channels in the complex. Binding of both effector molecules to P(II) signalling proteins may thus represent an effective feedback mechanism for regulating ammonium uptake through the membrane.

The role of the methylene blue and toluidine blue monomers and dimers in the photoinactivation of bacteria

The interactions between the phenothiazine dyes, methylene blue (MB) and toluidine blue (TB), and bacteria ( Staphylococcus aureus, Streptococcus pneumoniae, Enterococcus faecalis, Hemophilus influenzae, Escherichia coli and Pseudomonas aeruginosa) were studied spectrophotometrically. This demonstrated that a metachromatic reaction took place between the dyes and bacteria. Furthermore, bacteria induced additional dimerization of MB and TB. The effective dimerization constants of MB and TB were evaluated in the presence of each bacterial strain at a concentration of 10 8 CFU/ml. The analysis of the effective dimerization constants for MB and TB in the presence of bacteria indicated that the ability to form dimers was greater for TB than for MB. Gram-negative bacteria induced the dye dimerization more intensely than gram-positive bacteria. There was a correlation between the ability of each dye to form dimers in the presence of bacteria and the relative photobactericidal efficacy of each dye against these bacteria. These results provide evidence confirming the essential role of the dye dimers in bacterial photodamage.

Relaxation of the methylene blue monomer–dimer equilibrium in supercooled glycerol near the glass transition

The relaxation of the methylene blue monomer–dimer equilibrium in supercooled glycerol near the glass transition temperature, T g, was studied by monitoring the change in the optical absorbance associated with dimer formation during continuous cool/heat cycles. A hysteresis is observed in the absorbance at ≈ T g+25 K. Based on an analysis of the data using the Tool–Narayanaswamy–Moynihan model, relaxation in the hysteresis region is exponential. Exponential relaxation and the occurrence of the hysteresis at temperatures above the calorimetric T g are rationalized in terms of the length scale for monomer diffusion versus the length scale of the dynamic heterogeneity in glycerol.

High efficiency single dopant white electrophosphorescent light emitting diodesElectronic supplementary information (ESI) available: emission spectra as a function of doping concentration for 3 in CBP, as well as the absorption and emission spectra of Irppz, CBP and mCP. See http://www.rsc.org/suppdata/nj/b2/b204301g/

Efficient white electrophosphorescence has been achieved with a single emissive dopant. The dopant in these white organic light emitting diodes (WOLEDs) emits simultaneously from monomer and aggregate states, leading to a broad spectrum and high quality white emission. The dopant molecules are based on a series of platinum(II) [2-(4,6-difluorophenyl)pyridinato-N,C2′] β-diketonates. All of the dopant complexes described herein have identical photophysics in dilute solution with structured blue monomer emission (λmax = 468, 500, 540 nm). A broad orange aggregate emission (λmax ≈ 580 nm) is also observed, when doped into OLED host materials. The intensity of the orange band increases relative to the blue monomer emission, as the doping level is increased. The ratio of monomer to aggregate emission can be controlled by the doping concentration, the degree of steric bulk on the dopant and by the choice of the host material. A doping concentration for which the monomer and excimer bands are approximately equal gives an emission spectrum closest to standard white illumination sources. WOLEDs have been fabricated with doped CBP and mCP luminescent layers (CBP = N,N′-dicarbazolyl-4,4′-biphenyl, mCP = N,N′-dicarbazolyl-3,5-benzene). The best efficiencies and color stabilities were achieved when an electron/exciton blocking layer (EBL) is inserted into the structure, between the hole transporting layer and doped CBP or mCP layer. The material used for an EBL in these devices was fac-tris(1-phenylpyrazolato-N,C2′)iridium(III). The EBL material effectively prevents electrons and excitons from passing through the emissive layer into the hole transporting NPD layer. CBP based devices gave a peak external quantum efficiency of 3.3 ± 0.3% (7.3 ± 0.7 lm W−1) at 1 cd m−2, and 2.3 ± 0.2% (5.2 ± 0.3 lm W−1) at 500 cd m−2. mCP based devices gave a peak external quantum efficiency of 6.4% (12.2 lm W−1, 17.0 cd A−1), CIE coordinates of 0.36, 0.44 and a CRI of 67 at 1 cd m−2 (CIE = Commission Internationale de l'Eclairage, CRI = color rendering index). The efficiency of the mCP based device drops to 4.3 ± 0.5% (8.1 ± 0.6 lm W−1, 11.3 cd A−1) at 500 cd m−2, however, the CIE coordinates and CRI remain unchanged.

Quantification of methylene blue aggregation on a fused silica surface and resolution of individual absorbance spectra

The absorbance spectra of individual methylene blue aggregates adsorbed by spin coating on a fused silica surface are resolved. Using singular value decomposition and a model incorporating Beer's Law and elemental conservation, a varied concentration family of UV–Vis spectra are fit. Results indicate that H-dimer formation occurs beginning at a surface concentration of 3×1013molecules/cm2, and further aggregate formation, including J-type dimers, is significant above 2×1014molecules/cm2. Based on our results, past assumptions that a spin-coated surface (using a millimolar coating solution) results in a monolayer of methylene blue monomers should be reexamined.

Synthesis and Structure−Property Relationships of Soluble Rigid−Flexible Copolyethers Containing Blue and Yellow Light Emitting Units

A series of new rigid−flexible copolyethers containing blue- and yellow-emitting conjugated segments have been synthesized. The thermal, mechanical, and optical properties of the polymers are controlled by the type of the comonomers, their ratio at the preparation stage, and the length of the flexible spacer, as well as the structure of the blue monomer in the main chain. The polyethers were characterized by viscosimetry, thermal and mechanical analysis, NMR, and UV−vis and luminescence spectroscopy. The polymers obtained are soluble in common solvents, form free-standing films either from solution casting or after melt pressing, and show good mechanical properties. Regardless of the excitation wavelength, the polyethers show bright-yellow photoluminescence in solution, suggesting energy transfer from the blue to the yellow unit. In the solid state, the luminescence behavior is controlled by the monomer structure, the molar percentage of the comonomers, the length of the flexible spacer, and the excitatio...

New NO-donors with antithrombotic and vasodilating activities, Part 19. Pseudonitroles and their dimeric azodioxides.

Thirteen geminally substituted nitro-nitroso compounds (pseudonitroles) have been synthesized, four of them for the first time. In the solid state the pseudonitroles are dimerized to azodioxides. This is proved by IR spectroscopy, with the dimeric N-O valence vibration being observed between 1293 and 1306 cm-1. Only 1,3-diphenyl-2-nitro-2-nitrosopropane is monomeric even when solid. This is backed by its blue color and an IR band at 1574 cm-1. When dissolved in chloroform these azodioxides dissociate completely to the blue monomers (lambda max approximately 650 nm). Eight pseudonitroles inhibited the aggregation of blood platelets half-maximally at concentrations below 10 microM (Born test, collagen). When administered orally to rats (60 mg/kg) the thrombus formation in mesenteric arterioles and venules was inhibited up to 25 percent (k; 1-nitro-1-nitrosocyclohexane). When kept in aqueous media at 37 degrees C nitric oxide and its reduced from, i.e. nitrosohydrogen, are released. This suggests that the above biological effects arise from an NO dependent mechanism. The lack of influence on the blood pressure of spontaneously hypertensive rats, however, strongly suggests that an enzyme supported rather than a thermal formation of NO occurs in vivo.

Release of Methylene Blue from dioctadecyldimethylammonium chloride vesicles

The cationic dye Methylene Blue included in the internal aqueous microphase of dioctadecyldimethylammonium chloride (DODAC) vesicle shows the typical monomer–dimer equilibrium observed in homogenous aqueous solutions. Using a simple spectrophotometric method, values of 54 000 ± 1300 M–1 cm–1 and 3860 ± 130 M–1 have been obtained for the extinction coefficient of Methylene Blue monomer at 680 nm (eM680) and the equilibrium constant (K), respectively, in homogeneous aqueous solution at 20 °C. At this wavelength dimer absorbance is negligible. Leakage of Methylene Blue from the inner aqueous pseudophase can be described in terms of Fick’s law. The dependence of the release rate on monomer concentration, the value of the permeability constant (1.09 × 10–9 cm s–1 at 20.3 °C) and the dependence of the release rate on NaCl addition suggest that Methylene Blue diffuses across the lipidic bilayer of the vesicle as a monomer.

Importance of Methylene Blue Monomer in Methylene Blue Sensitized Dichromated Gelatin for Hologram Recording with Red Light

Importance of Methylene Blue Monomer in Methylene Blue Sensitized Dichromated Gelatin for Hologram Recording with Red Light

In-situ spectroelectrochemistry of adsorbed methylene blue on a sulphur-modified gold electrode

The properties of a methylene blue layer adsorbed onto a sulphur-modified gold electrode have been studied by electrochemical and in-situ reflectance spectroscopy in the visible region. At saturation coverage, methylene blue monomer and dimer bands were observed in the double-layer region through the electrochromism of the adsorbed film arising from the effect of the double-layer field on the molecule transition moment. Possible dye orientations in the adsorbed state are discussed with the aid of the optical measurements. At low surface concentrations, the optical signal stems from modulation of the monomer/dimer interconversion. Repeated electrochemical reduction and oxidation of adsorbed methylene blue result in gradual desorption of the dimer species, probably due to a change in the molecular geometry upon reduction which may evolve from a planar configuration to a folded structure.

CHARACTERIZATION OF THE RED LIGHT INDUCED REDUCTION OF A PARTICLE ASSOCIATED b‐TYPE CYTOCHROME FROM CORN IN THE PRESENCE OF METHYLENE BLUE*

Abstract—Methylene blue transfers electrons to a membrane‐associated b‐type cytochrome in particulate fractions from corn coleoptiles. The Km for methylene blue is less than 1 µM under optimal conditions. This reaction is destroyed by boiling, but not by 7 M urea. Kinetic analyses of the influence of light intensity on cytochrome reduction suggest that a first order photochemical reaction is limiting. Free EDTA may serve as an electron donor in this system at least at high methylene blue and protein concentrations. The photoactivity does not coincide either with mitochondrial or endoplasmic reticulum markers, and may be localized in plasma membrane. There is an estimated 5 times 10‐10 mol photoreducible cytochrome per g coleoptile tissue. Studies on the effect of pH on the reaction in the presence of methylene blue or thionine indicate that dye photoreduction itself is not rate‐limiting. Wavelength dependence studies suggest that it is methylene blue monomer and not dimer which mediates the reaction. Although oxygen is apparently required for the reaction, neither superoxide nor excited singlet oxygen appear to be involved. The reaction mechanism is still unknown.

Perylene excimer fluorescence in cyclohexane

The blue monomer fluorescence of perylene in cyclohexane is replaced by an orange excimer fluorescence emission upon freezing the solution with increasing pressure. The temperature dependence of the excimer decay is characterized by a radiative lifetime of 80 nsec and an activation energy of 670 cm−1.