Spectroscopic study of anthraquinone dye/amphiphile systems in binary aqueous/organic solvent mixtures

The absorption spectra of novel dye/amphiphile systems, in which the dye is a 1,5-bis-(R-phenylamino)anthraquinone [R = o-methoxy, o-ethoxy, H] and the solvents are either organic or H₂O/organic solvent mixtures, have been investigated. It was found that an abrupt λ_max shift of more than 80 nm occurred for the system containing dye having R = o-methoxy and the amphiphile (poly-bis-(2,2′-dimethyl-5,5′-disulphonate)naphthylmethane disodium salt) in pure solvents with a specific E_T(30) value or in H₂O/DMF (N,N-dimethylformamide) mixtures containing at least 38% water. This type λ_max shift was not observed when solvent mixtures containing the other two dyes were studied. The origin of the pronounced λ_max shift is discussed in detail. It is believed that this shift arises mainly from changes in the solvation state of hydrophobic dye having R = o-methoxy when water is introduced in the presence of a dispersing agent. In this regard, dye is converted from the monomolecular state to dispersed particles.     

Triphenylamine-based organic dyes containing benzimidazole derivatives for dye-sensitized solar cells

The synthesis and application to dye-sensitized solar cells of two new triphenylamine-based organic dyes containing benzimidazole derivatives as secondary donors together with a simple triphenylamine derived dye for the purpose of comparison is reported. The photophysical and electrochemical properties of the dyes were investigated by UV–vis spectroscopy and cyclic voltammetry. The introduction of benzimidazole derivatives in the phenyl ring of the triphenylamine core increases the molar extinction coefficients and λ_max because of the extension of the π-conjugation structures of the dyes. Overall conversion efficiencies of ∼2.5% under full sunlight (AM 1.5G, 100 mW cm⁻²) irradiation were obtained for DSSCs based on these new dyes, under the same conditions, the reference dye and di-tetrabutylammonium cis-bis(isothiocyanato) bis(2,2′-bipyridyl-4,4′-dicarboxylato) ruthenium(II) (N719) gave overall conversion efficiencies of 1.23% and 5.61%, respectively. Our findings demonstrate that the introduction of benzimidazole derivatives as secondary donors in triphenylamine-based dye can improve their photovoltaic performance compared to the unsubstituted reference dye in DSSCs.     

Preferential solvation of pomalidomide,an anticancer compound,in some binary mixed solvents at 298.15 K

Preferential solvation of pomalidomide (PMD) was explored in dimethyl sulfoxide (DMSO)-dimethylformamide (DMF), DMSO-tetrahydrofuran (THF), DMSO-methanol (MeOH), DMSO-isopropanol, DMSO-water, water-DMF, water-THF, water-MeOH, and water–isopropanol binary mixed solvents at 298.15 K. Bosch-Rose model was utilized to determine the electronic transition energies (E_T) and other preferential solvation parameters, describing solute-solute and solute-solvent interactions. We found that λ_max situation shifted with dielectric constant of the pure solvents meaningfully. According to the obtained results, E_T enhanced and λ_max shifted to the lower wavelengths as the percentage of DMSO decreased in the binary mixtures, remarking the important role of DMSO for stabilizing the excited state (π^⁎) of PMD chromophore via efficient intermolecular solute-solvent interactions. In addition, the aqueous binary systems showed an optimum point for the E_T values as the percentage of water changed in the solutions. The local mole fraction of the solvents in the cybotactic region was also estimated to describe the specific and non-specific interactions in the systems.     

Photoluminescence study of β relaxation of polyethylene blends

Secondary β relaxation of polyethylene blends (50/50 HDPE/LDPE) were studied by photoluminescence of anthracene molecules dissolved in the polymer bulk. The temperature of the β relaxation has been determined as T_β = ?40°C by the dependence of the ratio of vibronic components of the fluorescence band on the temperature. The molecular mechanism of this relaxation has been discussed considering the possibility of the energy migration involving anthracene molecules in the singlet electronic excited and ground states. © 1993 John Wiley & Sons, Inc.     

Synthesis,spectral properties and application of novel disazo disperse dyes derived from polyester waste

Terephthalic dihydrazide was obtained through aminolytic depolymerisation of polyester bottle waste by using hydrazine hydrate. It was further reacted with 4‐aminobenzoic acid in the presence of polyphosphoric acid to obtain a cyclic compound, 4,4′‐[5,5′‐(1,4)‐phenylene)bis(1,3,4‐oxadiazole‐5,2‐diyl)dianiline, having a heterocyclic moiety. Diazotisation of this compound followed by coupling with various N,N‐disubstituted anilines afford a series of novel disazo disperse dyes. The structures of these synthesised dyes were confirmed by elemental analysis and Fourier Transform–infrared, proton nuclear magnetic resonance and mass spectroscopy. Ultraviolet–visible spectra of these azo dyes in different polar solvents showed considerable variation in the wavelength of maximum absorbance (λ_max). Application of these dyes on polyester and nylon fabrics using high‐temperature dyeing methods gave brilliant yellowish red hues with fair to moderate light fastness and very good to excellent wash fastness and sublimation fastness.     

Strategies and investigations on bridging squaraine dye units

Synthetic strategies and basic molecular principles were investigated in order to achieve chromophores absorbing light in the far red or even near infrared region. Therefore, a comprehensive series of new squaraine dyes were synthesized and characterized. Beside monomeric unsymmetrical and symmetrical squaraine dyes, also squaraine dye dimers and oligomers bridged with phenylene, fluorene, iso-octyloxy phenylene and tetrafluoro phenylene moieties or directly coupled via condensation reaction were obtained. The influence of the various molecular dye structures to their absorption properties was studied with UV–vis measurements supported by theoretical investigations applying Kiprianov's theory of coupled dyes. With regard to Meyer's theory of the limiting values, the effective number of repeating units for dye series for the highest possible absorption maximum was determined. Observed trends and limiting values for electrochemical potentials and electrical band gaps of the dyes are in agreement with the UV–vis investigations. Finally, calculated molecular structures and frontier orbitals of dimers verify the results of the optophysical and electrochemical studies.     

Solar photocatalytic decolorization of dyes in solution with TiO2 film

Application of TiO₂ film to solar photocatalysis of organic dyes, including Methylene Blue (MB) (λ_max, 660 nm), RR195 (λ_max, 540 nm) and RY145 (λ_max, 420 nm), was investigated. It was found that after 6-h solar irradiation, the extent of color degradation of dyes using solar photocatalytic system without TiO₂ film was quite limited. The color removal percentage for MB, RR195, and RY145 was found to be 23.3, −9.3, and −20.7%, respectively, resulting from competitions between the photosensitizing reaction and formation of colored intermediates during solar irradiation. However, as TiO₂ film was applied, the color degradation capability of solar photocatalytic system was significantly improved, in spite of the fact that only approximately 7% of solar irradiation belongs to the UV region. The color removal percentage for MB, RR195, and RY145 was up to 93.6%, 85.3%, and 71.1%, respectively, after 6-h irradiation. We believed that in such a solar photocatalytic system immobilized with TiO₂ film, both the maximum absorbance wavelength of the dye and the adsorbability of the dye on TiO₂ film played significant roles on the rate and efficiency of color removal of the dye solutions. Moreover, the possible reaction mechanism was proposed. The solar photocatalytic process with immobilized TiO₂ film was found to follow the pseudo-first order reaction kinetics. Color removal rate of MB was almost twice of that of RY145. Accordingly, the photocatalytic degradation process using solar light as an irradiation source, and immobilized TiO₂ as a photocatalyst, showed potential application for the decolorization of wastewater.     

Studies on dyeing and structural behavior of chemically treated polyester yarns

The dyeing behavior of poly(ethylene terephthalate) based flat, high twist, and spun yarns pretreated with trichloroacetic acid–methylene chloride (TCAMC) reagent was studied. Disperse dyes having two different energy levels were employed for the dyeing work. The effect of time, temperature, and dye diffusion transition temperature (T_D) on dye uptake was analyzed. A considerable increase in equilibrium dye uptake and decrease in T_D of all the treated yarns were observed. The variation in dye diffusion behavior of higher and lower molecular weight dyes and the difficulties encountered in calculating the diffusion coefficient of the dyes are discussed. The structural and morphological changes effected by the pretreatment were also investigated using XRD and SEM, respectively. The increase in lateral order of the treated yarns was noted. The possible reason for an unusual relationship between the increase in lateral order and increase in dye uptake was explained. The cross-sectional shape and swelling and the smoothening out of the fiber surface were evidence by SEM. © 1996 John Wiley & Sons, Inc.     

The synthesis, spectroscopic and electrochemical properties, and application of new dyeing photoinitiator systems for acrylate monomers polymerization

New symmetrical bicationic polymethine dyes were synthesized and their spectroscopic and electrochemical properties were described. The bichromophoric dyes (benzothiazole, benzoxazole, indolinium derivatives) were investigated as sensitizers in the free radical photopolymerization initiated by their borate salts. The obtained kinetic results shown that bicationic polymethine dyes as the organoborate salts are much efficient photoinitiating systems of acrylate monomers polymerization than monocationic parent dyes. The rate of polymerization depends on ΔG_ET of electron transfer from borate anion to the excited singlet state of bicationic polymethine dye. The relationship between the rate of polymerization and the free energy of electron transfer process shows the dependence predicted by the classical theory of electron transfer.     

Spectroscopic study of interactions between model direct dyes and cotton

Although examined for years, interactions between direct dyes and the chemical structure of cotton cellulose remain an interesting, and still not entirely known, chemical phenomenon occurring in the fiber. Ten model azo dyes have been studied in aqueous solution, as dye powders and on cotton fabric using ¹³C MAS NMR and UV–visible spectroscopy. NMR spectroscopy indicates that model azo dyes, especially dye 8, interact by π‐stacking at the central biphenyl group, and that there is hydrogen bonding with cellulose. Model azo dyes are present as the azo or hydrazone tautomer. The UV–visible λ_max indicate that shifts are attributed to adsorption of model azo dyes into cellulose surfaces. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 758–766, 2007     

Optical properties of bis-(2,4,6-trimethylpyridine)iodine(I) cation: absorption and emission

With regard to its electronic structure, the cation Icoll₂⁺ (coll = collidine or 2,4,6-trimethylpyridine) is viewed as a coordination compound of iodine(I) with a p⁴ electron configuration. The lowest-energy excited state of Icoll₂⁺ is suggested to be a ππ^* collidine intraligand (IL) triplet which appears in absorption (λ_max=332 nm, ε=250) and emission (λ_max=405 nm, φ=0.001, τ∼90 ns). Owing to the heavy-atom effect of iodine this phosphorescence occurs at r.t. The longest-wavelength pp absorption is apparently obscured by the intense spin-allowed IL band at λ_max=268 nm.     

The influence of molecular weight of acid dyes on the yield stress of dyed nylon monofilament

The yield stress of nylon filament dyed with several acid dyes has been determined as a function of dye content and the molecular weight of acid dyes. The nylon filament dyes with acid dye has greater yield stress than undyed one. The relation between the increment of the yield stress (f) due to the adsorption of acid dye and the dye content (C) in the filament can be expressed by parameters A and B as log f = A log(C ? _C) + B, where C₀ is the dye content under which no contribution to the yield stress is observed and C₀ depends on the number of sulfonic groups in acid dye. It is found that these parameters A and B are expressed by M (the difference between the molecular weight of acid dye and the weight of SO₃Na groups in it) as A = 1 ? 100/M, B = k₁ M^k2, where k¹ and k² are the constants which depend on the parent chemical structure of dyes. The parameters A and B are expected to give available informations as to the physical state of adsorbed dye on nylon filament.     

Effect of side chain substituents on the electron injection abilities of unsymmetrical perylene diimide dyes

Three near-infrared (NIR) absorbing unsymmetrical perylene diimide D-A-D type dyes containing 6-undecanoxy as donor group were utilized in dye-sensitized nanocrystalline TiO₂ solar cells. Structure of the acceptor side of the molecules were improved by adding 4-[2-methyl-5-(cyanoacrylic acid)-3-thienyl]-phenyl (V), 3-carboxy-2-pyridil (VI) and 3-carboxy-2-pyrazyl (VII) moieties attached to one of the N-side of the dye. The relationship between the molecular structure of the acceptor sites of the dyes and the photovoltaic performances were discussed. Electrochemical measurements indicated that band gaps of the dyes were energetically favorable for electron injection from the excited state of the dyes to the conduction band of TiO₂ nanoparticles. However, three dyes gave lower conversion efficiency on DSSC applications. Strong electron-withdrawing nature of perylene core might not permit to transfer the photo-generated electrons to the carboxyl groups anchoring to TiO₂ surface, and then solar-to-electricity conversion efficiencies of the dyes were reduced.     

Ultraviolet Absorbing Efficacy and Photostability of Feruloylated Soybean Oil

Feruloylated soy glycerides (FSG) are a natural‐based, ultraviolet (UV) absorbing, antioxidant vegetable oil synthesized from the lipase‐catalyzed transesterification of ethyl ferulate and soybean oil. Commercial broad spectrum UV absorbing formulations contain multiple UV absorbing compounds that absorb UV radiation in specific regions. The most commonly used compounds are avobenzone (AVO, λ_max 356 nm) and octinoxate (ONX, λ_max 310 nm), which absorb primarily ultraviolet A and ultraviolet B radiation, respectively. The FSG chromophore is chemically similar to ONX but has a λ_max of 328 nm, approximately the median λ_max of AVO and ONX. Equimolar mixtures of AVO–ONX and AVO–FSG, 50 μM:50 μM, solutions in ethanol were compared to determine whether FSG was fungible for ONX in total absorbance capacity, photostability when exposed to UV radiation, and broad spectrum absorbance coverage before and after exposure to UV radiation. While it was determined that AVO–FSG mixtures possessed statistically indistinguishable total absorbance capacity compared to AVO–ONX solutions, AVO–FSG possessed slightly better photostability after 4 hours of UV exposure based on 95% confidence interval comparisons from weighted regression equations. Substituting FSG for half of the ONX (e.g., 50 μM:25 μM:25 μM AVO–ONX–FSG) resulted in the best mixture with total absorbance capacity and photostability statistically equal to the AVO–ONX mixtures but with statistically superior broad spectrum UV absorbance compared to AVO–ONX and AVO–FSG mixtures. The natural, vegetable oil‐based FSG can be substituted on an equimolar bases for ONX in mixtures with AVO to produce formulations with similar to superior efficacy.     

Dual drug release from CO2‐infused nanofibers via hydrophobic and hydrophilic interactions

This study investigated the effects of hydrophobic–hydrophilic interactions on dual drug release from CO₂‐infused nanofibers scaffolds (PCL, PCL–gelatin, and PCL “core” PCL–gelatin “shell”) using BODIPY 493/503 and Rhodamine B fluorescent dyes as drug models. Favorable dye–scaffold interactions increased total dye loading and promoted steady, more linear release. Unfavorable dye–scaffold interactions reduced overall loading and led to a greater burst release of dye. However, when CO₂ was used to infuse dye into an unfavorable scaffold, the changes in loading and release were less pronounced. When two dyes were infused, these behaviors were accentuated due to interactions between the dissolved forms of the dyes. Core–shell composite nanofibers displayed radically different release properties versus pure PCL–gelatin fibers when treated with dyes via CO₂ infusion. Dye release from core–shell scaffolds was highly sensitive to both interactions with scaffolds and the phase of CO₂ used to infuse the compounds of interest. By using different phases of CO₂ to partition dyes into hydrophobic and hydrophilic sections of core–shell nanofibers, such interactions can be manipulated to develop a bimodal drug release system with potential application in drug delivery or tissue engineering. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42571.     

Generation and Electron-Transfer Reactivity of the Long-Lived Photoexcited State of a Manganese(IV)-Oxo-Scandium Nitrate Complex

Photoexcitation of a manganese(IV)-oxo-scandium nitrate complex ([(Bn-TPEN)Mn^IV(O)]²⁺−Sc(NO₃)₃) in a solvent mixture of trifluoroethanol and acetonitrile (v/v=1 : 1) resulted in generation of the long-lived photoexcited state, which is detected by nanosecond laser transient absorption measurements. The transient absorption maximum (λ_max) of the ²E excited state of [(Bn-TPEN)Mn^IV(O)]²⁺−Sc(NO₃)₃ is observed at 620 nm with lifetimes of 7.1 μs. The λ_max value is blue-shifted and the lifetime becomes longer as compared with the previously reported values of λ_max (640 nm) and lifetime (6.4 μs) of the ²E excited state of the 1 : 2 complex between [(Bn-TPEN)Mn^IV(O)]²⁺ and Sc(OTf)₃ ([(Bn-TPEN)Mn^IV(O)]²⁺−(Sc(OTf)₃)₂). The electron-transfer reactivity of the ²E excited states of [(Bn-TPEN)Mn^IV(O)]²⁺−Sc(NO₃)₃ was similar to that of [(Bn-TPEN)Mn^IV(O)]²⁺−(Sc(OTf)₃)₂. The long lifetime and the high reactivity of the ²E excited state of [(Bn-TPEN)Mn^IV(O)]²⁺−Sc(NO₃)₃ provide an excellent photooxidant for oxidation of compounds, which would otherwise be impossible to be oxidized.     

The effect of disperse dyes on the glass transition temperature of polymers

The lowering of the glass transition temperature (T_g) of a polymer produced by the incorporating various concentrations of azo disperse dyes has been investigated, and the effects of the structure and concentrations of the dyes were examined. The T_g values were lowered with increasing dye concentrations in the polymer, and the lowering of T_g produced by the dyes was influenced not only by the molecular structure of the dyes but also the dye-polymer interactions.     

Untersuchungen zum UV/VIS-Spektralverhalten von Azofarbstoffen. XV. Eine Analyse der Absorptionsspektren von 4,4′-Diaminoazobenzenen

Studies on UV/VIS Absorption Spectra of Azo Dyes. XV. An Analysis of the Absorption Spectra of 4,4′-Diaminoazobenzenes In the visible absorption spectrum 4,4′-bis-diethylaminoazobenzene shows two absorption maxima (λ_max = 426 nm and λ_max = 477 nm) with high intensity. Quantum chemical calculations and examination by peak separation of six 4-substituted azobenzenes and six 4′-substituted 4-diethylaminoazobenzenes ( 1a–k ) indicate that the longest wavelength band is due to a n-π* transition and the other band is due to a π-π*-transition. This is verified using an increment system for n-π* absorption maxima. A linear relation is found between intensity ratios of the two bands and the HAMMETT -σ-constants of the substituents. With increasing electron releasing tendency of the substituents the absorption intensity of the n-π*-band increases.     

Computational study of the one- and two-photon absorption properties of macrocyclic thiophene derivatives

The geometrical structure, electronic structure, one-photon and two-photon absorption properties of a series of macrocyclic thiophene derivatives C[3T_DA]_n (n = 2-5) have been studied using density functional theory (DFT) and Zerner’s intermediate neglect of differential overlap (ZINDO) methods theoretically. The results showed that the range of λ⁽¹⁾_maxs is 390-470 nm and λ⁽²⁾_maxs is 640-670 nm, while, both λ⁽¹⁾_max and λ⁽²⁾_max gradually enlarge as increasing the number of the C[3T_DA] unit. And C[3T_DA]_n compounds exhibited large TPA cross-section (δ_max), and the factors influencing on the δ_max values were analyzed in detail. Transition dipole moments M_0k and M_kn play important roles on δ_max. Both π-electron number (N_e) and the product of oscillator strengths from ground state to mediate state (?_0k) and from mediate state to final state (?_kn) are in proportion to δ_max. Moreover, δ_max linearly depends on the static second-order nonlinear optical susceptibilities (β₀).