Dye In Methanol Research Articles

Spectral and photophysical properties of fluorone dyes in bio-related films and methanol

The fluorone dyes fluorescein, 4,5-dibromofluorescein, eosin Y, erythrosine B, and rose bengal in the biological materials gelatin, starch, and chitosan have been characterized by absorption and emission spectroscopy. Comparative studies were carried out for the same dyes in methanol. The absorption cross-section spectra, luminescence quantum distributions, luminescence quantum yields, fluorescence quantum yields, and degrees of luminescence polarization were determined by steady-state spectroscopy. The fluorescence lifetimes were measured by time-resolved laser experiments. High fluorescence quantum yields were obtained for fluorescein in both the solid hosts and the liquid solutions. The fluorescence reduction due to enhancement of intersystem crossing by heavy atom spin-orbit coupling was efficient both in the biofilms and in methanol. Room temperature phosphorescence emission was observed for the heavy atom substituted fluorescein derivatives in the biofilms. The spectroscopic behavior of the fluorone dyes depends on their ionic state with highest luminescence efficiency for the dianionic forms. This form was realized for all investigated dyes in basic methanol and in most cases also in the biofilms.

Electrochemical threshold conditions during electro-optical switching of ionic electrophoretic optical devices

Electro-optical modulation by electrophoresis of dye ions is a promising technique for applications such as electronic paper displays and nonmechanical beam steering devices. To achieve a sufficient response rate in these devices, the transition time between two different optical states can be decreased by increasing the magnitude of the voltage applied across the electrodes, but this also leads to irreversible and undesirable electrochemical reactions. An electron tunneling model has been developed to describe the electrochemical reaction and to better understand the conditions determining its onset. The model gives rise to three predictions that were subsequently confirmed experimentally: the magnitude of the applied surface charge density should determine the rate of electrochemical activity, the bulk concentration of ions in the solution should shift the threshold voltage at which electrochemical reactions occur, and the reaction rate should be substantially enhanced around nanometer-sized bumps on the electrode surface. Applying this new understanding, the transition time of a device incorporating porous zinc antimonate (ZnSb2O6) electrodes and a solution of Methylene Blue dye in methanol was reduced by a factor of approximately 20.

Interfacially polymerized thin film composite membranes on microporous polypropylene supports for solvent-resistant nanofiltration

Interfacial polymerization (IP) is a powerful technique for fabrication of thin film composite (TFC) membranes. The polymers used most often as support are polysulfone (PS) or polyethersulfone (PES). These supports have limited stability in organic solvents. In this work, microporous polypropylene (PP) flat film and hollow fiber membranes were used as a support to fabricate TFC membranes for nanofiltration by the IP technique. Porous polypropylene membranes can provide substantial chemical, pH, and solvent resistance and are therefore suitable as supports for fabricating TFC membranes functioning as solvent-stable nanofiltration membranes. The surface and the pore interior of polypropylene flat sheet and hollow fiber membranes were hydrophilized first by pre-wetting with acetone followed by oxidation with chromic acid solution. A standard procedure to successfully coat the hydrophilized flat film and hollow fiber membranes was developed next. The monomeric system chosen for IP was poly(ethyleneimine) and isophthaloyl dichloride. The TFC hollow fiber membranes were characterized by nanofiltration of safranin O (MW 351) and brilliant blue R (MW 826) dyes in methanol. Rejection values of 88% and 43% were achieved for brilliant blue R and safranin O, respectively at a transmembrane pressure of 413 kPa in the TFC hollow fiber membranes. Pressure dependences of the solvent flux and solute rejection of the TFC membranes were studied using the modified flat sheet membranes up to a pressure of 965–1241 kPa. Solvent flux increased linearly with an increase in the transmembrane pressure. Solute rejection also increased with an increase in the transmembrane pressure. All modified membranes were also characterized using scanning electron microscopy. Extended-term solvent stability of the fabricated membranes was studied in toluene; the membranes demonstrated substantial solvent stability in toluene.

Stilbazolium merocyanine dye determination in different solutions, concentrations and colloids using SERS

AbstractSurface‐enhanced Raman scattering (SERS) measurements were carried out on stilbazolium merocyanine dye in methanol and pyridine solvents. Both solutions were measured in a series of concentrations covering a range of 5 × 10−5 M to 5 × 10−8 M. In these measurements, Ag and Au colloids were used, and the results have shown that Ag colloids yield better enhancement in the Raman spectra of this dye. Moreover, the effect of adding NaCl solution to the SERS samples was also studied. All measurements were carried out using the state‐of‐the‐art ChiralRaman instrument, which utilizes a 532 nm laser source. We report here on the success of using SERS to obtain Raman spectra of merocyanine dye at very low concentrations in an attempt to find a new approach that can be used for further investigations of the dye. The SERS spectra are reported here, and the results from different solutions, colloids, concentrations and pH values are compared. Copyright © 2006 John Wiley & Sons, Ltd.

Possible singlet oxygen generation from the photolysis of indigo dyes in methanol, DMSO, water, and ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate

We suggest that singlet molecular oxygen [ 1O 2 ( 1Δ g)] is formed upon irradiation of indigo 1 [in air or O 2-saturated DMSO and DMSO (0.5% H 2SO 4)] and indigo carmine 2 [in air or O 2-saturated CH 3OH, D 2O, and 1-butyl-3-methylimidazolium tetrafluoroborate (BmIm–BF 4)]. The quantum yield for production of 1O 2 is estimated to be 0.6 for 1 and 0.3–0.5 for 2. The rates of reaction of 1O 2 with 1 and 2 were determined by monitoring the emission of 1O 2 at 1270 nm over time. Low molar absorptivities (at 532 nm) and rapid physical quenching caused by 1 and 2 limit their utility as 1O 2 photosensitizers in solution. Compounds 1 and 2 degrade slowly during the photolysis due to a self-sensitized (type I or II) photooxidation reaction. Oxidative cleavage of 1 by singlet oxygen and superoxide, and 2 by superoxide has been noted before (Kuramoto, N.; Kitao, T. J. Soc. Dyers Color. 1979, 95, 257–261; Kettle, A. J.; Clark, B. M.; Winterbourn, C. C. J. Biol. Chem. 2004, 279, 18521–18525).

Molecular Forms of Coumarin-307 in Sol-Gel Glasses

Coumarin-307(C-307) impregnated sol-gel glass samples were prepared by two methods - (I) predoping using HNO3 as catalyst, and (II) postdoping using HNO3 as catalyst and formamide as drying control chemical additive (DCCA). The absorption/fluorescence properties including fluorescence lifetime of the dye in these sol-gel host matrices were studied and results were compared with dye in methanol (MeOH). In addition to usual non-polar form of C-307 that exists in MeOH, amino-protonated form and dimer of dye have also been found to co-exist in the dried state of samples prepared by predoping method. This behaviour of dye was uncommon to sol and gel states of materials. The fluorescence quantum yield (Qf) of C-307 doped solid was found to be 0.77 and it was almost constant in the concentration range 5 x 10(16) to 8.8 x 10(17) cm(-3). On the other hand, only non-polar form of C-307 has been observed in the samples prepared by postdoping method. The Qf value of dye was 0.96 in the postdoped samples. To explain such behaviour of C-307 in the two types of sol-gel matrices: dye concentration, role of HNO3, water, formamide and matrix effect have been taken into account.

Application of standard addition methodology for the determination of banned azo dyes in different leather types

An analytical procedure based on microwave-assisted extraction (MAE) and standard addition was applied for the determination of banned azo dyes in bovine, sheep, and goat leather. Standard addition at four different concentration levels was performed using azo dyes, dissolved either in methanol or water. All dyes were determined indirectly by measuring their corresponding harmful aromatic amines, formed after reduction by use of sodium dithionite. Comparing found amounts of amines with theoretical target values allowed an assessment of accuracy. The recoveries were also compared with those obtained for non-spiked samples using external standard calibration. The standard addition approaches provided much better accuracy than external standard calibration, with recoveries close to 100% for most amines. Since there was no great difference in recoveries when using methanol or water as solvent, preparation of the dyes in methanol might be preferred because of the faster evaporation of the solvent after spiking.

Measuring the absolute quantum efficiency of luminescent materials

A measurement system and mathematical procedure are developed for determining the absolute quantum efficiency (QE), of luminescent materials. This technique, based on absorption of diffuse light within an integrating sphere, is applied to fluorescent laser dyes and conventional phosphor powders. The system described is tested for excitation in the near-UV and blue regions, but can be applied to higher energy excitation (UV), as well as lower energy excitation in the visible to near-IR, with the appropriate photodetectors and optical filters. The system was tested on both liquid and solid samples such as Coumarin 500 (CM500) dye in methanol and ethyl acetate; Rhodamine 6G in ethanol; and a variety of powder phosphors. The QE of quinine sulfate dihydrate solution (5×10 −3 M in 0.1 N H 2SO 4), a NIST fluorescence standard, was found to be in good agreement with the NIST value under 390 nm excitation. The accuracy of this measurement technique is acceptable for samples with absorption cross sections greater than ∼6 mm 2.

Saturable and reverse saturable absorption of Rhodamine B in methanol and water

We have investigated nonlinear absorption of Rhodamine B dye in methanol and water near resonance (532 nm) on the higher-energy (435 nm) and lower-energy (600 nm) sides of the absorption band, using an open-aperture Z-scan technique with nanosecond pulses. We observed reverse saturable absorption (RSA) at 435 nm in both of the solvents, and a transition from saturable absorption (SA) to RSA with an increase in either intensity or concentration at 600 nm in methanol. A transition from RSA to SA with an increase in concentration at 600 nm was observed with water as the solvent. We used theoretical analysis based on rate equations to determine the two-photon and excited-state absorption coefficients from the experimental results.

Release characteristics of an azo dye from poly(ureaurethane) microcapsules

The time course for the transfer of azo dyes from the microcapsule core of dioctylphthalate to the dispersing medium of methanol through a poly(ureaurethane) (PUU) membrane was measured for various average size microcapsules with a size distribution. The dye release curves are represented by a stretched exponential function C( t)= C eq{1−exp [−( t/ τ eff) α ]}, where C( t) is the concentration of the dye in methanol, C eq that at the equilibrium state, and t the time. The exponent α decreased by increasing the variance of the size distribution of microcapsules. The effective time constant τ eff was expressed by τ eff= c 0〈 R 2〉/ κ( α), where 〈 R 2〉 and κ( α) are the mean square of microcapsule radius and a correction for the size distribution, respectively. The characteristic proportional constant, c 0, was determined as 2.6±0.2 min/μm 2. From the value of the constant, the diffusion coefficient of the azo dye in the PUU membrane was evaluated as 2.6×10 −12 cm 2/s.

Permeability of azo-dye through poly(urea-urethane) microcapsule membrane

Transfer of azo-dyes from dioctylphthalate to methanol through poly(urea-urethane) microcapsule (PUUMC) membrane has been measured. The release curves are expressed by an exponential equation C s= C ∞(1−e − t/ τ ), where C s is the concentration of the dye in methanol, C ∞ that at the equilibrium state, t the elution time and τ is a time constant. C ∞ and τ are related to the chemical potentials and the diffusion coefficient of the dye, based on a simple theoretical model. The relationship between τ and the absolute temperature exhibits non-Arrhenius behavior at high temperatures. The non-Arrhenius behavior is explained on the basis of the chemical potential effect on τ. At low temperatures, τ exhibits the Arrhenius behavior. From a semi-logarithmic plot of τ versus the reciprocal of the absolute temperature in the low temperature region, the activation energy for the transfer of the dye is estimated.

Handling and detection of 0.8 amol of a near-infrared cyanine dye by capillary electrophoresis with laser-induced fluorescence detection.

We are interested in the detection of DNA adducts and other trace analytes by labeling them with a fluorescent tag followed by use of capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) for high resolution and sensitivity. Towards this goal, here we report the following: (1) synthesis and handling properties of a near-IR, carboxyl-substituted heptamethine cyanine dye; (2) modification of an existing ball lens LIF detector to provide near-LIF detection with excitation at 785 nm for CE; and (3) corresponding handling and detection of as little as 0.8 amol of the dye by enrich-injection of 4.7 microl of 1 x 10(-13) mol/l dye in methanol from an 8-microl volume into a corresponding CE-LIF system. The electrolyte for the separation was methanol-40 mmol/l aqueous sodium borate (98:2, v/v). This finding encourages further exploration of the dye by functionalization of its carboxyl group for chemical labeling purposes.

Pervaporation of water–dye, alcohol–dye, and water–alcohol mixtures using a polyphosphazene membrane

A novel phosphazene heteropolymer (HPP) was synthesized that contained three differing pendant groups: 2-(2-methoxyethoxy)ethanol (MEE), 4-methoxyphenol, and 2-allylphenol. The resulting polymer is an amorphous elastomer with good film forming properties where MEE and 4-methoxyphenol pendant groups influenced the hydrophilicity and the solvent compatibility of the polymer. Sorption studies were performed to characterize the polymer in terms of Hansen solubility parameters. Additionally, group contributions were used to predict the Hansen parameters for the polymer and these data compared favorably with the observed solubility behavior with 15 solvents that ranged from hydrocarbons to water. Homopolymers synthesized from MEE and 4-methoxyphenol were also studied for solubility revealing different behaviors with each representing a limit in hydrophilicity; MEE formed a water-soluble hydrophilic polymer and 4-methoxyphenol yielded a hydrophobic polymer. Membranes formed from HPP were characterized for use as pervaporation membranse using five different feeds: water–dye, methanol–dye, 2-propanol–dye, water–2-propanol, and water–methanol. Fluxes of methanol and isopropanol were greater than for water. For the alcohol–water separations, the alcohol was the favored permeate in all cases with higher fluxes observed for higher alcohol feed concentrations, however, separation factors declined.

Effect of aggregation on bacteriochlorin a triplet-state formation: a laser flash photolysis study.

Bacteriochlorin a (BCA) is a potential photosensitizer for photodynamic therapy of cancer. It has been shown previously that the photoefficiency of the dye is mainly dependent on singlet oxygen (1O2) generation. Nanosecond laser flash photolysis was used to produce and to investigate the excited triplet state of the dye in methanol, phosphate buffer and dimiristoyl-L-alpha-phosphatidylcholine (DMPC) liposomes. The transients were characterized in terms of their absorption spectra, decay kinetics, molar absorption coefficients and formation quantum yield of singlet-triplet intercrossing. The lifetime of the BCA triplet state was measured at room temperature. The triplet-state quantum yield is quite high in methanol (0.7) and in DMPC (0.4) but only 0.095 in phosphate buffer. In the last case, BCA is in a monomer-dimer equilibrium, and the low value of the quantum yield observed was ascribed to the fact the triplet state is only formed by the monomers.

Cardiolipin binds nonyl acridine orange by aggregating the dye at exposed hydrophobic domains on bilayer surfaces

10- N-Nonyl acridine orange (NAO) has been used at low concentrations as a fluorescent indicator for cardiolipin (CL) in membranes and bilayers. The mechanism of its selective fluorescence in the presence of CL, and not any other phospholipids, is not understood. The dye might recognize CL by its high p K (p K 2>8.5). To investigate that, we established that NAO does not exhibit a p K in a pH range between 2.3 and 10.0. A second explanation is that the dye aggregates at hydrophobic domains on bilayers exposed by the CL. We found that a similar spectral shift occurs in the absence of CL in a concentrated solution of the dye in methanol and in the solid state. A model is proposed in which the nonyl group inserts in the bilayer at the hydrophobic surface generated by the presence of four chains on the phospholipid.

Investigation of the spectral properties of a squarylium near-infrared dye and its complexation with Fe(III) and Co(II) ions

The spectral features of the squarylium near-infrared (NIR) dye NN525 in different solutions and its complexation with several metal ions were investigated. The absorbance maximum of the dye is λ=663 nm in methanol. This value matches the output of a commercially available laser diode (650 nm), thus making use of such a source practical for excitation. The emission wavelength of the dye in methanol is λ em=670 nm. The addition of either Fe(III) ion or Co(II) ion resulted in fluorescence quenching of the dye. The Stern–Volmer quenching constant, K SV, was calculated from the Stern–Volmer plot to be K SV=2.70×10 7 M −1 for Co(II) ion. The K SV value for Fe(III) ion could not be established due to the non-linearity of the Stern–Volmer plot and the modified Stern–Volmer plot for this ion. The detection limit is 6.24×10 −8 M for Fe(III) ion and 1.55×10 −5 M for Co(III) ion. The molar ratio of the metal to the dye was established to be 1:1 for both metal ions. The stability constant, K S, of the metal–dye complex was calculated to be 3.14×10 6 M −1 for the Fe–dye complex and 2.64×10 5 M −1 for the Co–dye complex.

Investigations of energy transfer from some diolefinic laser dyes to Rhodamine 110

2,5-Distytyl pyrazine (DSP) and 1,4-bis(β-pyridyl-2-vinyl) benzene (P2VB) laser dyes have been studied with respect to energy transfer to rhodamine 110 (R110) laser dye in methanol and butanol by steady state emission measurements. The Stern–Volmer plots are linear, from which the second order-quenching rate constants of energy transfer ( k ET) were determined as 9.8×10 12 and 13.4×10 12 mol −1 dm 3 s −1 for DSP–R110, 2.17×10 13 and 2.3×10 13 mol −1 dm 3 s −l for P2VB–R110 in methanol and butanol, respectively. The critical transfer distances ( R 0) have been calculated from the emission of donor and absorption spectra of the acceptor using the Förster formula as 41.4 and 41 Å for P2VB–R110, 55.5 and 52.7 Å for DSP–R110 in the same solvents, respectively. The large values of k ET and R 0 indicate that the dominant mechanism responsible for energy transfer is due to long-range dipole–dipole interaction between excited donor and ground state acceptor molecules.

FLR technique exchange of methanol/fluorescent dye with water in water-saturated cement paste examined by NMR

A water saturated cement paste (w/c = 0.7) confined in a solution of methanol saturated with a fluorescent dye showed complete exchange of water after 10 days. However, after exchange the concentration of dye within the cement paste was less than 50% compared to the expected equilibrium value. This result is rationalized by the much larger solubility of dye in methanol compared to water, by more than two orders of magnitude. The diffusion of dye into the cement paste is thus a rather complex process, likely to involve precipitation at the water/methanol interphase, followed by an increasing solubility as more methanol enters the cement paste. The 1H nuclear magnetic resonance spectral analysis suggests that methanol and/or dye reacts with the cement paste.

Spectroscopy and laser characteristics of copper-vapor-laser pumped Pyrromethene-556 and Pyrromethene-567 dye solutions

We measured the basic optical properties of Pyrromethene-567 (P567) and Pyrromethene-556 (P556) dye solutions that are relevant to their application as dye lasers. The fluorescence spectra of methanol solutions show mirror images in relation to the absorption spectra, with Stokes shifts of 29.5 and 37.5 nm, respectively, for the two dyes. The central fluorescence peaks were at 546 and 535 nm, with widths of ~40 and ~50 nm (FWHM). The quantum yields were 97% ? 5% and 78% ? 5% for P567 and P556, respectively. Fluorescence lifetimes of 6.0 ? 0.2 ns were obtained for both dyes in methanol. Laser action, obtained by pumping with the green emission line (510.6 nm) from a copper-vapor laser, was measured in a Hänsch-type cavity. Tunability ranged from 531 to 590 nm for P567 and from 522 to 590 nm for P556. Lasing thresholds were ~0.27 and ~0.16 mJ/pulse, with 25% and 27% slope efficiencies for P567 and P556, respectively. Spectroscopy and lasing were studied in other solvents as well.

Femtosecond Spectroscopic Study of Relaxation Processes of Three Amino-Substituted Coumarin Dyes in Methanol and Dimethyl Sulfoxide

Time-resolved fluorescence spectra of three amino-substituted coumarin dyes have been recorded in methanol and dimethyl sulfoxide using the fluorescence upconversion technique with an apparatus response function of ≈200 fs fwhm. The three fluorinated coumarins are the 7-amino-4-trifluoromethylcoumarin (C151), the 7-diethylamino-4-trifluoromethylcoumarin (C35), and the rigidified aminocoumarin with a julolidine structure (C153). The dynamic Stokes shifts are found to be dominated by an ultrafast component with a characteristic time shorter than the present time resolution of ≈50 fs. The dynamic Stokes shifts are compared to estimations based on a “Kamlet and Taft” analysis of steady-state data in 20 solvents. It is found that the ultrafast component can be assigned mainly to intramolecular relaxation. The influences of photoinduced changes of solute−solvent hydrogen bonds on the observed spectral shifts are discussed. The breaking of hydrogen bonds at the amino group is very fast in both solvents and embed...