Search

Squaraines have been known for many decades as very stable and versatile vis–NIR absorbing dyes. They have found applications for example as sensitizers in organic photovoltaics and photodetectors. The most common squaraine structure is the 1,3-regioisomer. Their 1,2-regioisomers are seldom mentioned and unanimously regarded as side products. A facile direct synthesis of 1,2-squaraines, highlighting the role played by reaction conditions and electronic factors, is described. The first electrochemical characterization of these dyes is also shown. [ABSTRACT FROM AUTHOR]

Elucidation of photoinduced charge transfer behavior in organic dye/metal hybrids is important for developing photocatalytic systems for solar energy conversion. We report the synthesis and photophysical characterization of a perylene-3,4:9,10-bis(dicarboximide) (PDI)–ruthenium(II) complex, bis-PDI-2,2′-bipyridineRu(II)Cl2(CNtbutyl)2, which has favorable energetics, ΔGCS≈ −1.0 eV, for singlet electron transfer from the Ru complex to PDI. Time-resolved optical spectroscopy reveals that upon selective photoexcitation of PDI, ultrafast charge transfer (<150 fs) from the Ru complex to 1*PDI generates the Ru(III)–PDI–•ion pair. The resulting vibrationally hot Ru(III)–PDI–•ion pair exhibits fast relaxation (τ = 3.9 ps) and charge recombination (τCR= 63 ps). Our experimental and computational (DFT and TDDFT) studies show that energy-preserving photodriven singlet electron transfer can dominate in properly designed organic dye/metal complexes, making them of particular interest for use in artificial photosynthetic systems for solar fuels formation. [ABSTRACT FROM AUTHOR]

The high molar absorption coefficient organic D-π-A dye C220 exhibits more than 6% certified electric power conversion efficiency at AM 1.5G solar irradiation (100 mW cm−2) in a solid-state dye-sensitized solar cell using 2,2′,7,7′-tetrakis(N,N-dimethoxyphenylamine)-9,9′-spirobifluorene (spiro-MeOTAD) as the organic hole-transporting material. This contributes to a new record (6.08% by NREL) for this type of sensitized heterojunction photovoltaic device. Efficient charge generation is proved by incident photon-to-current conversion efficiency spectra. Transient photovoltage and photocurrent decay measurements showed that the enhanced performance achieved with C220 partially stems from the high charge collection efficiency over a wide potential range. [ABSTRACT FROM AUTHOR]

The 1H NMR chemical shifts were theoretically computed for the organic dyes 2-(2,6-dimethyl-4H-pyran-4-ylidene)-malononitrile (1), cyano-(2,6-dimethyl-4H-pyran-4-ylidene)-acetic acid methyl ester (2), 2-(2,6-bis(4-(dimethylamino)styryl)-4H-pyran-4-ylidene)-malononitrile (3), and methyl 2-(2,6-bis(4-(dimethylamino)styryl)-4H-pyran-4-ylidene)-2-cyanoacetate (4) at the GIAO/B3LYP/6-311(d,p)//B3LYP/6-311(d,p) level of theory. Moreover, the intramolecular rotational barriers of the molecules were calculated to evaluate the internal flexibility with respect to the torsional degrees of freedom, and the nuclear-independent chemical shifts (NICS) were employed to analyze the ring currents. The difference was explained in terms of intramolecular hydrogen bonds and ring currents of the molecules. The 1H NMR spectra were reproduced by experiments for the comparison with computationally constructed data. Our results suggest a good guideline in interpreting 1H NMR chemical shifts using computational methods and furthermore a reliable perspective for designing molecular structures. [ABSTRACT FROM AUTHOR]

The quest of organic dyes presenting improved electronic features has been extremely active during the last decades, as new structures are necessary to build novel materials such as dye-sensitized solar cells, nonlinear optics commutators, or molecular photochromic switches. Cyanine derivatives occupy a key spot in that scene, as they present intense absorption bands and tunable colors, even when a relatively short π-conjugated path is used. This behavior has often been interpreted as a consequence of a negligible bond length alternation. Recently, Thorley et al. have designed and characterized new cationic compounds that possess the cyanine electronic features, though presenting sizable bond length alternation (Angew. Chem. Int. Ed.2008, 47, 7095−7098). In this contribution, I investigate, with quantum mechanical tools, the size dependence of these properties in model symmetric dyes displaying Thorley’s patterns. Extended chains are simulated in order to obtain insights into the chain length convergence, and the results are compared to those obtained at the same level of theory for classical cyanine architectures. This theoretical work is a step toward the rational development of more efficient π-conjugated compounds. [ABSTRACT FROM AUTHOR]

The synthesis, spectroscopic properties, and TD-DFT calculations of new aza-Boron-dipyromethene dyes featuring pendant nitrofluorenylethynyl substituents are described. This functionalization allows for moving the luminescence in the NIR, conserving a good quantum yield efficiency. [ABSTRACT FROM AUTHOR]

Fluorescence correlation spectroscopy (FCS) has been used to study the motion of fluorescent dyes in a giant (diameter 20 000 nm = 20 μm) catanionic vesicle comprised of the surfactant sodium dodecyl sulfate (SDS) and dodecyltrimethyl ammonium bromide (DTAB). The diffusion in the anion (SDS) rich catanionic vesicle was studied both in bulk water and in an immobilized vesicle attached to a positively charged glass surface. In the case of the immobilized vesicle, the diffusion coefficients (Dt) of R6G (rhodamine 6G), DCM (4-dicyanomethylene-2-methyl-6-p-dimethyl aminostyryl-4H-pyran), and C343 (coumarin 343) are found to be 1.5, 2.5, and 10 μm2/s, respectively, which are 280, 120, and 55 times slower compared to those for the same dyes in bulk water. The magnitude of Dtis found to vary for different vesicles. This was attributed to the difference in size and shape of the immobilized vesicles. In bulk, R6G binds completely to the vesicle and exhibits extremely slow diffusion with Dt= 0.5 ± 0.1 μm2/s (∼850 and 3 times slower compared to that of R6G in bulk water and within the immobilized vesicle). This is attributed to very slow overall diffusion of the very large size vesicles (20 μm = 20 000 nm). Both of the dye molecules (DCM and C343) show two different diffusion coefficients for the vesicles in bulk. In this case, the small Dt(0.5 ± 0.1 μm2/s) corresponds to the diffusion of the vesicle as a whole and the large Dtvalue (300 and 550 μm2/s for DCM and C343, respectively) corresponds to the free dye molecules in bulk water. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSCs) with cobalt-based mediators with efficiencies surpassing the record for DSCs with iodide-free electrolytes were developed by selecting a suitable combination of a cobalt polypyridine complex and an organic sensitizer. The effect of the steric properties of two triphenylamine- based organic sensitizers and a series of cobalt polypyridine redox mediators on the overall device performance in DSCs as well as on transport and recombination processes in these devices was compared. The recombination and mass-transport limitations that, previously, have been found to limit the performance of these mediators were avoided by matching the properties of the dye and the cobalt redox mediator. Organic dyes with higher extinction coefficients than the standard ruthenium sensitizers were employed in DSCs in combination with outer-sphere redox mediators, enabling thinner TiO2 films to be used. Recombination was reduced further by introducing insulating butoxyl chains on the dye rather than on the cobalt redox mediator, enabling redox couples with higher diffusion coefficients and more suitable redox potential to be used, simultaneously improving the photocurrent and photovoltage of the device. Optimization of DSCs sensitized with a triphenylamine-based organic dye in combination with tris(2,2'-bipyridyl)cobalt(II/III) yielded solar cells with overall conversion efficiencies of 6.7% and open-circuit potentials of more than 0.9 V under 1000 W m-2 AM1.5 G illumination. Excellent performance was also found under low light intensity indoor conditions. [ABSTRACT FROM AUTHOR]

Millimeter-sized single MOF-5 crystals are used as "chromatographic columns" to effectively separate mixtures of organic dyes. Remarkably, owing to the nanoscopic pore dimensions and the molecular-level interactions between the migrating molecules and the MOF scaffold, the separations occur over a distance of only a few hundred micrometers which is unambiguously confirmed by fluorescence confocal microscopy. [ABSTRACT FROM AUTHOR]

The synthesis, electronic properties, and performance in dye-sensitized solar cells (DSSC5) of four cone-shaped organic dyes (ITD, UFD-Th, ITD-Hx, and ITD-OM) containing the isotruxene π-scaffold are reported. Selective substitution of the unsymmetrical isotruxene core with two diarylamino donors and one cyanocarboxylic acid acceptor was achieved by using a prefunctionalized dibromoisotruxene building block. The ortho-para-branched isotruxene core allows strong electronic couplings among the donors and the acceptor, leading to red-shifted absorption profiles with significant charge-transfer character. All four isotruxene dyes display reversible anodic waves in cyclic voltammagrams with both 1-LOMO and LUMO potentials suitable for application in DSSCs. The DSSCs fabricated with these cone- shaped organic dyes exhibited high open-circuit voltages (0.67-0.76 V) and fill factors (0.67-0.72) with a power conversion efficiency (η) up to 5.45%, which is 80% of the ruthenium dye N7 19-based standard cell fabricated and measured under the same conditions. [ABSTRACT FROM AUTHOR]

A series of symmetrical D−π-A−π-D molecules based on benzothiadiazole and oligo(thienylenevinylene)s were facilely developed. The investigation of their photophysical and electrochemical properties demonstrated that these compounds exhibited broad absorption covering the whole visible range with appropriate energy levels for light-harvesting donors. [ABSTRACT FROM AUTHOR]

This work reports a theoretical study of the photovoltaic properties of a series of original conjugated metal-free organic dyes containing the triphenylamine (TPA) moiety. These compounds have recently been developed for dye sensitized solar cells (DSSCs). Our (TD)DFT-based procedure made it possible to get insights into the geometrical and electronic structures of the dyes and to unravel the structural modifications optimizing the properties of TPA-based DSSCs. In particular, we aimed at improving the electron injection process as well as the light harvesting efficiency of the dyes. On the other hand, molecular dynamic (MD) investigations of the kinetics of the regeneration step have been performed for both "classical" (CHCl3/I3-/I-/Li+) and iodide imidazolium-based solvent-free electrolytes (DMII+/I-). The MD simulations helped to understand the regeneration mechanism for the solvent-free electrolyte: it combines the DMII+/DMII0 couple to the I3-/I- redox system which acts as a "mediator". [ABSTRACT FROM AUTHOR]

Color is an important component in the perception of beauty and in an artist’s original intent when creating a work. Better conservation of our cultural heritage requires detailed knowledge of artwork materials and the complex evolution they have endured over time. Organic dyes have been used from ancient times, and their characterization is a challenge that has been successfully addressed over the past few years by the development of advanced techniques, such as microspectrofluorimetry. [ABSTRACT FROM AUTHOR]

We demonstrate an effective micelle shuttle between water and a hydrophobic ionic liquid and its application in transportation in the biphasic system, using a commercially available and inexpensive Pluronic block copolymer. The poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (P123) block copolymer self-assembles into micelles in both water and the ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate, as characterized by dynamic light scattering. The poly(ethylene oxide) blocks provide the well-solvated corona, whereas the poly(propylene oxide) blocks form the solvophobic core. The micelles can spontaneously transfer between the two phases upon a simple temperature stimulus; the transfer is reversible and repeatable, and 1H NMR analysis indicates quantitative transfer. The micelle nanocarriers are used to transport various cargoes in the biphasic system: fully reversible transport of hydrophobic small organic dyes into and out of water and facile extraction of an ionic liquid-phobic polymer from the ionic liquid. This simple round-trip delivery system may be used in delivery, separations, and extraction in synthesis and biphasic catalysis involving ionic liquids. [ABSTRACT FROM AUTHOR]

We employ the 4,4-dihexyl-4H-cyclopenta[2,1-b:3,4-b′]dithiophene (CPDT) segment as a conjugated spacer to construct an extremely high-molar-absorption-coefficient organic chromophore for dye-sensitized solar cells, exhibiting a high power conversion efficiency of 8.95% measured under irradiation of 100 mW cm−2 AM1.5G sunlight. Our comparative experiments have proved the prominent merit of employing CPDT instead of the prevailing 2,2′-dithiophene (DT) as the building block for the further dye design. We also have demonstrated that a controllable coassembling of dye molecules and electrolyte components on semiconducting nanocrystals can reduce surface states and inhibit charge recombination synchronously. [ABSTRACT FROM AUTHOR]

A series of dyes were synthesized to examine the roles of the hydrophilic characteristics of R in sensitized hydrogen generation by dye-grafted Pt/TiO2under visible light irradiation. The hydrogen-generation efficiencies and optimum amounts of the dyes grafted to Pt/TiO2were affected substantially by the hydrophilic and steric effects of R; moderately hydrophilic DEO1 and DEO2 showed higher sensitization activity at a lower loading than hydrophobic D-H. [ABSTRACT FROM AUTHOR]

The monomer−aggregate equilibrium of four phenothiazine (PN) dyes, containing thionine (TH), methylene blue (MB), new methylene blue (NMB), and 1,9-dimethylmethylene blue (DMB), in the tungsten(VI) oxide (WO3) nanocolloid solution has been investigated by means of UV−vis spectroscopy. Addition of PN dye into the WO3nanocolloid solution brought about significant changes in the absorption spectrum, suggesting the formation of H-type (face-to-face fashion) trimer on the WO3nanocolloid surface. The adsorptivity of PN dyes onto the WO3nanocolloid surface was diminished by the raising the ionic strength, indicating the evidence of the electrostatic interaction between cationic PN dye and negatively charged WO3nanocolloids. The detail analysis of each spectral data provided insight into the effect of molecular structure of PN dyes on the adsorption and aggregation behaviors on the WO3nanocolloid surface. Moreover, in situmeasurement of PN dye aggregation using the centrifugal liquid membrane (CLM) technique revealed that the aggregation of PN dyes on the WO3nanocolloid surface proceeded in a two-step three-stage (monomer → dimer → trimer) formation. The aggregation mechanism of PN dyes on the WO3nanocolloid surface was discussed on the basis of Kasha’s exciton theory. [ABSTRACT FROM AUTHOR]

A new dye, SSD1, featuring two donor/acceptor chromophores aligned in a spiro configuration with two anchoring groups separated at a distance of 10.05 Å (closely matching the distance between the adsorption sites of the anatase TiO2surface) undergoes efficient dye adherence on TiO2films. A dye-sensitized solar cell incorporating SSD1exhibited a short-circuit current of 8.9 mA cm−2, an open-circuit voltage of 0.63 V, a fill factor of 0.67, and a power conversion efficiency of 3.75%. [ABSTRACT FROM AUTHOR]

New dipolar compounds incorporating a dithieno[3,2-b:2′,3′-d]thiophene unit as the electron donor, an oligothiophene moiety as the conjugated spacer, and 2-cyanoacrylic acid as the electron acceptor have been synthesized. These nonarylamine type metal-free organic compounds have been successfully used as the sensitizers of dye-sensitized solar cells (DSSCs). The conversion efficiencies of the DSSCs range from 3.54 to 5.15% under AM 1.5 G irradiation. The best efficiency reached ∼70% of the ruthenium dye N719-based standard cell fabricated and measured under similar conditions. [ABSTRACT FROM AUTHOR]

A two-dimensional (2D) optical coherent spectroscopy that correlates the double excited electronic states to constituent single excited states is described. The technique, termed two-dimensional double-quantum coherence spectroscopy (2D-DQCS), makes use of multiple, time-ordered ultrashort coherent optical pulses to create double and single quantum coherences over the time intervals between the pulses. The resulting 2D electronic spectra map out the energy correlation between the first excited state and two-photon-allowed double-quantum states. Measurements of organic dye molecules show that the near-resonant energy offset for adding a second electronic excitation to the system relative to the first excitation is on the order of tens of millielectronvolts. Simulations of DQC spectra show that vibronic transitions add rich features to the 2D spectra. The results of quantum chemical calculations on model systems provide insight into the many-body origin of the energy shift measured in the experiment. These results demonstrate the potential of 2D-DQCS for elucidating quantitative information about electron−electron interactions, many-electron wave functions, and electron correlation in electronic excited states and excitons. [ABSTRACT FROM AUTHOR]

Two indole-based organic dyes were conveniently prepared and well characterized. The triphenylamine or carbazole moieties were bonded to the indole group acting as a potential electron donor, which can tune the HOMO and LUMO levels of the resultant dye, and another triphenylamine or carbazole group was linked to the pyrrole ring on the nitrogen atom, which was expected to suppress the aggregation of the dye in the solid state to some degree. These two dyes were utilized as dye sensitizers in dye-sensitized solar cells and demonstrated efficient photon-to-electron conversion properties. [ABSTRACT FROM AUTHOR]

We characterize the nature of the low-lying excited states in H-aggregated perylene bisimide (PBI) dyes in terms of the recently proposed long-range-corrected density functional theory (LRC-DFT) and the mixed intramolecular Frenkel exciton (FE) and the intermolecular charge-transfer exciton (CTE) model. The singlet vertical excitation energies of H-aggregated PBI dimers and multimers are theoretically evaluated by considering the aggregation details. It is found that the dimer absorption follows closely the spectra of PBI aggregates in solution and demonstrates strong mixing of two kinds of excitons. The experimentally observed low-energy absorption peak near 2.3 eV should not be a pure CT state but a mixed excitonic state. To model the electronic excitations of H-aggregated PBI multichromophoric oligomers, we adopt a mixed FE-CTE model Hamiltonian, whose microscopic parameters are determined from LRC-DFT/TD-LRC-DFT calculations performed on an individual chromophore or a chromophore pair. By involving four to five PBI chromophores, we have succeeded in reproducing the experimental trends of optical properties in PBI stacking, such as the large blue shift of the absorption band, the mixed FE-CTE nature of the low-energy absorption bands, and the large Stokes shift of emission spectra. The long-range correction on DFT exchange-correlation energy functionals is crucial to correctly evaluate the photophysical characteristics of π−π stacks. [ABSTRACT FROM AUTHOR]

The interaction of anionic micelle sodium dodecyl sulfate (SDS) and amphiphilic block copolymers polyethylene-b-polyethylene glycol (PE-b-PEG) and the sharp change of excited-state charge-transfer complex photophysics of 2-(4-(dimethylamino)styryl)-1-methylpyridinium iodide (DASPMI) inside of the supramolecular assembly have been addressed in the paper. The dramatic enhancement of emission intensity of DASPMI incorporated inside of the nanostructure formed by micellar and polymeric chains indicates a completely different environment compared to that in the water and micellar system. A huge increase in the rotational relaxation time obtained from time-resolved anisotropy decay and the value of the order parameter is indicative of a very restrictive regime in the self-assembly system. The wobbling and translational motion of the probe is also restricted inside of the micelle−polymer aggregate due to the presence of polymer chains. The translational diffusion coefficient is drastically reduced due to the aggregation. [ABSTRACT FROM AUTHOR]

Organic laser dyes coumarin 1, coumarin 2, coumarin 102, coumarin 314, and coumarin 334 have been included in crystalline guanidinium organodisulfonate (GDS) host frameworks, forming stable inclusion compounds with lamellar architectures. The GDShosts consist of 2D quasihexagonal hydrogen-bonded sheets with topologically complementary guanidinium (G) ions and the sulfonate (S) moieties of a variety of organodisulfonates that serve as “pillars” that connect opposing GSsheets, thus generating inclusion cavities between the sheets. These host frameworks display a variety of architectural isomers, including the so-called bilayer, simple brick, zigzag brick as well as two heretofore unreported framework isomers: double zigzag brick and a “chevron” brick. These isomers vary with respect to the connectivity between opposing GSsheets and the corresponding shape of the inclusion cavities. The preference for the framework isomers reflects a systematic templating role for the guest molecules, largely based on their steric requirements. The coumarin guests exhibit a distinct arrangement in each host−guest combination, resulting in a range of fluorescence emission wavelengths that differ from that observed for the monomeric form in dilute solutions. For example, the bilayer framework, which has narrow 1D pores, enforces the alignment of coumarin guests as head-to-tail arrays resembling J-aggregates. The simple brick structure, however, has wider 1D channels that permit the formation of linear arrays of face-to-face coumarin dimers resembling H-aggregates. The coumarin guests in the zigzag brick architecture are confined within isolated inclusion cavities as face-to-face dimers. In general, the maxima of the emission bands of the coumarin dyes in the bilayer structure are blue-shifted, while those in the simple brick and zigzag brick structures are red-shifted. The fluorescence reflects the unique guest−guest packing in each framework isomer as well as interactions between the coumarin guest and the organodisulfonate pillar. The ability to include laser dyes in high concentrations in a robust host framework with regulation of intermolecular association between the dye molecules may lead to new solid-state lasing materials that overcome some of the barriers encountered for dyes embedded as dilute solutes in amorphous solid-state matrices such as polymers, zeolites, and sol−gel glasses. [ABSTRACT FROM AUTHOR]

When an alkyl-functionalized metal-free organic dye (MK-2) was employed as a sensitizer, dye-sensitized TiO2solar cells (DSSCs) fabricated with an ionic liquid (IL) electrolyte showed an energy conversion efficiency of 7.6%, which was comparable to that with a volatile liquid electrolyte. This contrasts with the case of DSSCs employing conventional Ru complex sensitizer (N719), whose efficiency was decreased markedly when the electrolyte was replaced from the volatile to IL. As a result, with the IL electrolyte, the conversion efficiency with MK-2 was higher than that with N719. The result was mainly attributed to longer electron lifetime in the DSSCs with MK-2. The longer electron lifetime is remarkable because with conventional volatile electrolyte, the lifetimes with many organic dyes including MK-2 were shorter than that with N719. This high compatibility of MK-2 with the IL electrolyte shows that the molecular modification of organic dyes can overcome the both disadvantages of ILs and organic dyes, mostly originated from their high viscosity and from the short electron lifetime observed with volatile electrolyte, respectively. Long-term stability of the DSSCs with MK-2 and the ionic electrolyte was also investigated, showing the efficiency of more than 7% for 2000 h under 1 sun conditions. [ABSTRACT FROM AUTHOR]

The self-assembly of uniform single-crystalline microrods of organic dye Sudan II (1-(2,4- dimethylphenyl-azo)-2-naphthol) in solution was achieved by reprecipitation with the assistance of amphiphilic block copolymer Pluronic F127. It was found that the formation of F127 micelles was favorable for the production of uniform Sudan II microrods whereas individual F127 molecules favored the formation of Sudan II fibers. The optical absorption and fluorescence emission properties of the uniform microrods were characterized, and the time-dependent spectra of the precipitating solution for microrod formation were measured to monitor the self-assembly process of Sudan II molecules. The Sudan II microrods exhibited intense fluorescence emission, indicating an unusual aggregation-induced emission (AIE) phenomenon for Sudan II. The fluorescent microscopy investigation suggested that the obtained Sudan II microrods exhibited remarkable optical waveguide behavior, which is expected to serve as single rod active optical waveguides that can be used as building blocks for miniaturized photonic devices. Furthermore, novel Sudan II microplates, which exhibited interesting 2D optical waveguide behavior, were readily obtained by reprecipitation of Sudan II from cationic surfactant cetyltrimethylammonium bromide (CTAB) solution. [ABSTRACT FROM AUTHOR]

Solid-state dye-sensitized solar cells were fabricated using an organic dye, 2-cyanoacrylic acid-4-(bis-dimethylfluoreneaniline)dithiophene (JK2), which exhibits more than 1 V open-circuit potential (Voc). To scrutinize the origin of high voltage in these cells, transient Vocdecay measurements and density functional theroy calculations of the interacting dye/semiconductor surface were performed. A negative conduction band shift was observed due to the favorable dipolar field exerted by the JK2 sensitizer to the TiO2surface, at variance with heteroleptic Ru(II)-dyes for which an opposite dipole effect was found, providing an increased Voc. [ABSTRACT FROM AUTHOR]

A new organic fluorescent dye, 2,4-dichloro-6-[p-(N,N-diethylamino)biphenylyl]-1,3,5-triazine (DBQ), with an electron withdrawing−donating pair bridged by a twistable aromatic chain has been synthesized. DBQ exhibits high fluorescence quantum yields (0.96 in hexane and 0.71 in THF), high extinction coefficients, and an excitation window extending up to ∼480 nm. Due to the strong intramolecular charge transfer character, DBQ shows obviously solvent-dependent Stokes shifts with a value as high as 6360 cm−1in THF and controllable fluorescence emission in the visible region from “blue” to “orange”. The axially chiral structures of DBQ crystals were clearly revealed by the X-ray analyses and CD spectroscopy measurements. Two enantiomers of DBQ were obtained by spontaneous resolution upon crystallization without any chiral auxiliary. The low rotation barriers around the interannular bonds in DBQ molecules resulted in an efficient and selective multiplication of each of the chiral structures when DBQ crystallized in THF at room temperature in the presence of an enantiopure crystal seed, leaving racemized DBQ molecules in the solution. The special crystalline properties of DBQ provided a new approach to the design and synthesis of organic chiral crystals. The photophysical properties of DBQ make it promising in the preparation of new fluorescent probes with high sensitivity. [ABSTRACT FROM AUTHOR]

Tailored ad-hoc methods must be developed for successful identification of minute amounts of natural dyes on works of art using Surface-Enhanced Raman Spectroscopy (SERS). This article details two of these successful approaches using silver film over nanosphere (AgFON) substrates and silica gel coupled with citrate-reduced Ag colloids. The latter substrate functions as the test system for the coupling of thin-layer chromatography and SERS (TLC-SERS), which has been used in the current research to separate and characterize a mixture of several artists' dyes. The poor limit of detection of TLC is overcome by coupling with SERS, and dyes which co-elute to nearly the same spot can be distinguished from each other. In addition, in situ extractionless non-hydrolysis SERS was used to analyze dyed reference fibers, as well as historical textile fibers. Colorants such as alizarin, purpurin, carminic acid, lac dye, crocin, and Cape jasmine were thus successfully identified. [ABSTRACT FROM AUTHOR]

We have characterized the structure of J-aggregate in a Langmuir−Blodgett film of pure merocyanine dye (MS18) fabricated under an aqueous subphase containing a cadmium ion (Cd2+) and have investigated its thermal behavior by UV−visible and IR absorption spectroscopy in the range from 25 to 250 °C with a continuous scan. The results of both UV−visible and IR absorption spectra indicate that temperature-dependent changes in the MS18aggregation state in the pure MS18system are closely and mildly linked with the MS18intramolecular charge transfer and the behavior of the packing, orientation, conformation, and thermal mobility of MS18hydrocarbon chain, respectively. The J-aggregate in the pure MS18system dissociates from 25 to 150 °C, and the dissociation temperature at 150 °C is higher by 50 °C than that in the previous MS18-arachidic acid (C20) binary system. The lower dissociation temperature in the binary system originates from the fact that temperature-dependent structural disorder of cadmium arachidate (CdC20), being phase-separated from MS18, has an influence on the dissociation of J-aggregate. From 160 to 180 °C, thermally induced blue-shifted bands, caused by the oligomeric MS18aggregation, appear at around 520 nm in the pure MS18system by contraries, regardless of the lack of driving force by the melting phenomenon of CdC20. The temperature at which the 520 nm bands occur is in good agreement with the melting point (160 °C) of hydrocarbon chain in MS18with Cd2+, whereas its chromophore part is clearly observed to melt near 205 °C by UV−visible spectra. Therefore, it is suggested that the driving force that induces the 520 nm band in the pure MS18system arises from the partial melting of hydrocarbon chain in MS18with Cd2+. [ABSTRACT FROM AUTHOR]

The use of nanoparticles, either for the delivery of drugs or for imaging contrast agents, or a combination of both (theranostics), is very appealing in biological and biomedical research. The design of high-quality NIR-emitting quantum dots (QDs), with outstanding optical properties in comparison to that of organic dyes, should lead to novel contrast agents with improved performance for optical and multimodal imaging. Moreover, these nanocrystals could also be used for exploring therapeutic applications, such as drug delivery or phototherapy. In this article, we report the coating of commercial ITK705-amino QDs with methoxy-terminated poly(ethylene glycol) (PEG) of different chain lengths. Homogeneous QD solutions that are stable over extended periods of time were prepared. The impact of the particle coating on their in vivo fate after tail IV injection was studied by fluorescence imaging. The speed of the first pass extraction of the coated QDs toward the liver decreased with the PEG length, whereas the hydrodynamic diameter of the particles was increased. [ABSTRACT FROM AUTHOR]

The catalytic degradation of organic dye (methylene blue, MB) has been studied using green oxidation methods (tertiary-butyl hydrogen peroxide, TBHP, as the oxidant with several doped mixed-valent and regular manganese oxide catalysts in water) at room and higher temperatures. These catalysts belong to a class of porous manganese oxides known as octahedral molecular sieves (OMS). The most active catalysts were those of Mo6+- and V5+-doped OMS. Rates of reaction were found to be first-order with respect to the dye. TBHP has been found to enhance the MB decomposition, whereas H2O2does not. Reactions were studied at pH 3−11. The optimum pH for these reactions was pH 3. Dye-decomposing activity was proportional to the amount of catalyst used, and a significant increase in catalytic activity was observed with increasing temperature. X-ray diffraction (XRD), energy dispersive spectroscopy (EDX), and thermogravimetric analysis (TGA) studies showed that no changes in the catalyst structure occurred after the dye-degradation reaction. The products as analyzed by electrospray ionization mass spectrometry (ESI-MS) showed that MB was successively decomposed through different intermediate species. [ABSTRACT FROM AUTHOR]

New large size luminescent nanoparticles have been prepared, based on lead bromide or iodide organic perovskites. The luminescent center is made of PbX42−octahedrons. The preparation of the nanoparticles stems from fast nebulization and subsequent lyophilization of perovskite DMF solutions. The particles described have an average size of 60 nm, but a 20−500 nm range is in principle accessible. These new nanoparticles constitute an alternative to Q-dots which allows variable size while retaining the same emission wavelength, like silica particles functionalized with organic dyes, but with a higher stability under illumination. [ABSTRACT FROM AUTHOR]

We report the synthesis and unique spectroscopic properties of organic styryl dye nanoparticles. Aqueous-phase ion association between a cationic styryl dye 2-(4-(dimethylamino)styryl)-1-ethylpyridinium (DASPE), possessing both electron donor and acceptor groups in its molecule, and tetraphenylborate (TPB) or tetrakis(4-fluorophenyl)borate (TFPB) anion, in the presence of poly(vinylpyrrolidone), produces the ion-based dye (DASPE) nanoparticles of ∼30−100 nm in diameter. Absorption spectra of the DASPE nanoparticles show a large bathochromic shift in comparison with that of the dye monomer in water. Quantum chemical calculations demonstrate that ion-pair formation brings about a large internal rotation around a single bond in DASPE, and this internal twisting as well as local polarity of the counteranion have a strong influence on the red shift of the optical spectra. Furthermore, nanoparticle formation results in enhanced fluorescence of DASPE: more than a 20-fold enhancement in the fluorescence quantum yield as compared to that of the dye monomer in water, giving a new methodology for the synthesis of fluorescent organic nanoparticles. The observed fluorescence would come from an intramolecular charge-transfer (ICT) excited state stabilized by the matrix of TPB or TFPB, and the enhancement is due to both the high rotational resistance for the single bond in DASPE and the matrix polarity effect that can suppress the nonradiative processes. [ABSTRACT FROM AUTHOR]

A series of structurally simple dipolar light-harvesting organic dyes featuring 1,3-cyclohexadiene in the aromatic π framework for dye-sensitized solar cells has been synthesized and characterized. The highest conversion efficiency of the DSSCs based on these dyes can reach up to 4.4%. [ABSTRACT FROM AUTHOR]

New metal-free dyes with a furan moiety in the conjugated spacer between the arylamine donor and the 2-cyanoacrylic acid acceptor have been synthesized, and high efficiency dye-sensitized solar cells were fabricated using these molecules as light-harvesting sensitizers. [ABSTRACT FROM AUTHOR]

Noncharged pyrene molecules were incorporated into multilayer films by first loading pyrene into poly(acrylic acid) (PAA)-stabilized cetyltrimethylammonium bromide (CTAB) micelles (noted as PAA&(Py@CTAB)) and then layer-by-layer (LbL) assembled with poly(diallyldimethylammonium chloride) (PDDA). The stable incorporation of pyrene into multilayer films was confirmed by quartz crystal microbalance (QCM) measurements and UV−vis absorption spectroscopy. The resultant PAA&(Py@CTAB)/PDDA multilayer films show an exponential growth behavior because of the increased surface roughness with increasing number of film deposition cycles. The present study will open a general and cost-effective avenue for the incorporation of noncharged species, such as organic molecules, nanoparticles, and so forth, into LbL-assembled multilayer films by using polyelectrolyte-stabilized surfactant micelles as carriers. [ABSTRACT FROM AUTHOR]

The article focuses on the use of bimetallic zero-valent iron in enhanced biological treatment of industrial wastewaters. It states that municipal wastewater is traditionally treated via biological processes such as aerobic organisms in suspended systems or surface-anchored biofilms, while industrial process wastes often possess toxic pollutants that are less biodegradable. It examines the use of iron shavings for enhanced biological treatment of wastewater from industrial processes, with the shavings containing iron, chromium, silica, and a few other trace elements. It comments on reactions of iron shavings with chlorinated aliphatic compounds, organic dyes, and with nitrobenzenes and chlorinated phenols.

A theoretical analysis, based on density functional theory, has been carried out on the electronic properties of eosin yellowish (2′,4′,5′,7′-tetrabromofluorescein), a dye used for photovoltaic applications. In particular different oxidation states of the bare molecule as well as its complexes with a Zn dication have been considered, with the aim to gain some insights on its electro- and photochemical behavior. The calculations have been carried out both in the gas phase and in solution, this last modeled by a continuum model. Besides the agreement with the experimental data, our results allow for a better interpretation of the spectroscopic properties of this dye and their tuning by interaction with the solvent or metal atom in aqueous solution. [ABSTRACT FROM AUTHOR]

Textile dye bath effluent contains high concentrations of organic dye, sodium chloride, and other chemicals which inhibit the activity of microorganisms during biological oxidation. Hence high concentrations of organic dye and total dissolved solids have to be removed considerably before biological treatment. In this paper, degradation of dye effluent and simultaneous generation of caustic soda in an electrochemical membrane cell was investigated. Experiments were carried out at different current densities and different flow rates using Ti/RuO 2/IrO 2as anode and stainless steel as cathode. In the present study of dye effluent treatment the results showed that the electrochemical process could effectively remove COD and color by anodic oxidation (92.16% and 100%) and concentrate caustic soda from 40 to 210.28 g L −1. [ABSTRACT FROM AUTHOR]

We have developed a new color-encoding method that facilitates high-throughput screening of one-bead one-compound (OBOC) combinatorial libraries. Polymer beads displaying chemical compounds or families of compounds are stained with oil-based organic dyes that are used as coding tags. The color dyes do not affect cell binding to the compounds displayed on the surface of the beads. We have applied such rainbow beads in a multiplex manner to discover and profile ligands against cell surface receptors. In the first application, a series of OBOC libraries with different scaffolds or motifs are each color-coded; small samples of each library are then combined and screened concurrently against live cells for cell attachment. Preferred libraries can be rapidly identified and selected for subsequent large-scale screenings for cell surface binding ligands. In a second application, beads with a series of peptide analogues (e.g., alanine scan) are color-coded, combined, and tested for binding against a specific cell line in a single-tissue culture well; the critical residues required for binding can be easily determined. In a third application, ligands reacting against a series of integrins are color-coded and used as a readily applied research tool to determine the integrin profile of any cell type. One major advantage of this straightforward and yet powerful method is that only an ordinary inverted microscope is needed for the analysis, instead of sophisticated (and expensive) fluorescent microscopes or flow cytometers. [ABSTRACT FROM AUTHOR]

Perylene-3,4:9,10-bis(dicarboximide) (PDI) and its derivatives are robust organic dyes that strongly absorb visible light and display a strong tendency to self-assemble into ordered aggregates, having significant interest as photoactive materials in a wide variety of organic electronics. To better understand the nature of the electronics states produced by photoexcitation of such aggregates, the photophysics of a series of covalent, cofacially oriented, -stacked dimers and trimers of PDI and 1,7-bis(3‘,5‘-di-t-butylphenoxy)perylene-3,4:9,10-bis(dicarboximide) (PPDI) were characterized using both time-resolved absorption and fluorescence spectroscopy. The covalent linkage between the chromophores was accomplished using 9,9-dimethylxanthene spacers. Placing n-octyl groups on the imide nitrogen atoms at the end of the PDI chromophores not attached to the xanthene spacer results in PDI dimers having near optimal -stacking, leading to formation of a low-energy excimer-like state, while substituting the more sterically demanding 12-tricosanyl group on the imides causes deviations from the optimum that result in slower formation of an excimer-like excited state having somewhat higher energy. By comparison, PPDI dimers having terminal n-octyl imide groups have two isomers, whose photophysical properties depend on the ability of the phenoxy groups at the 1,7-positions to modify the stacking of the PPDI molecules. In general, disruption of optimal -stacking by steric interactions of the phenoxy side groups results in excimer-like states that are higher in energy. The corresponding lowest excited singlet states of the PDI and PPDI trimers are dimer-like in nature and suggest that structural distortions that accompany formation of the trimers are sufficient to confine the electronic interaction on two chromophores within these systems. This further suggests that it may be useful to build into oligomeric PDI and PPDI systems some degree of flexibility that allows the structural relaxations necessary to promote electronic interactions between multiple chromophores. [ABSTRACT FROM AUTHOR]

We present a device based study into the operation of liquid electrolyte dye-sensitized solar cells (DSSC’s) using organic dyes. We find that, for these systems, it is entirely necessary to employ a compact TiO 2layer between the transparent fluorine doped SnO 2(FTO) anode and the electrolyte in order to reduce charge recombination losses. By incorporation of a compact layer, the device efficiency can be increased by over 160% under simulated full sun illumination and more than doubled at lower light intensities. This is strong evidence that the more widely employed ruthenium based sensitizers act as to “insulate” the anode against recombination losses and that many planar organic dyes employed in DSSC’s could greatly benefit from the use of a compact TiO 2blocking layer. This is in strong contrast to DSSC’s sensitized with ruthenium based systems, where the introduction of compact TiO 2has only marginal effects on conversion efficiencies. [ABSTRACT FROM AUTHOR]

The article discusses the syntheses and spectroscopic properties of 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes and their derivatives. According to the authors, the dyes tend to be strongly ultraviolet-absorbing small molecules that emit relatively sharp fluorescence peaks with high quantum yields. They add that the dyes are relatively insensitive to the polarity and pH of their environment and are reasonably stable to physiological conditions.

Laser-induced acoustic desorption (LIAD) from thin metal foils is a promising technique for gentle and efficient volatilization of intact organic molecules from surfaces of solid substrates. Using the single-photon ionization method combined with time-of-flight mass spectrometry, we have examined the neutral component of the desorbed flux in LIAD and compared it to that from direct laser desorption. These basic studies of LIAD, conducted for molecules of various organic dyes (rhodamine B, fluorescein, anthracene, coumarin, BBQ), have demonstrated detection of intact parent molecules of the analyte even at its surface concentrations corresponding to a submonolayer coating. In some cases (rhodamine B, fluorescein, BBQ), the parent molecular ion peak was accompanied by a few fragmentation peaks of comparable intensity, whereas for others, only peaks corresponding to intact parent molecules were detected. At all measured desorbing laser intensities (from 100 to 500 MW/cm²), the total amount of desorbed parent molecules depended exponentially on the laser intensity. Translational velocities of the desorbed intact molecules, determined for the first time in this work, were of the order of hundreds of meters per second, less than what has been observed in our experiments for direct laser desorption, but substantially greater than the possible perpendicular velocity of the substrate foil surface due to laser-generated acoustic waves. Moreover, these velocities did not depend on the desorbing laser intensity, which implies the presence of a more sophisticated mechanism of energy transfer than direct mechanical or thermal coupling between the laser pulse and the adsorbed molecules. Also, the total flux of desorbed intact molecules as a function of the total number of desorbing laser pulses, striking the same point on the target, decayed following a power law rather than an exponential function, as would have been predicted by the shake-off model. To summarize, the results of our experiments indicate that the LIAD phenomenon cannot be described in terms of simple mechanical shake-off or direct laser desorption. Rather, they suggest that multistep energy-transfer processes are involved. Two possible (and not mutually exclusive) qualitative mechanisms of LIAD that are based on formation of nonequilibrium energy states in the adsorbate-substrate system are proposed and discussed. [ABSTRACT FROM AUTHOR]

A novel metallophthalocyanine derivative, cobalt tetra (2,4-dichloro-1,3,5-triazine) aminophthalocyanine (Co-TDTAPc), was prepared and immobilized on cellulosic fiber by covalent bond to obtain a supported oxidation catalyst (Co-TDTAPc-F). Co-TDTAPc-F/H2O2 system based on phase-transfer catalytic oxidation for decomposing dyes, including acid, reactive, and direct dyes, has been investigated thoroughly. Compared to traditional adsorption technologies and advanced oxidation processes (AOPs) for dye treatment, Co-TOTAPc-F/H2O2 combines the advantages of both and is more efficient and more effective. Azo dyes such as C. I. Acid Red 1 (AR1) can be quickly adsorbed onto/into the fiber from aqueous solution and decomposed in situ simultaneously in the presence of Co-TDTAPc-F and H2O2. It has been found that the reaction process is not affected by the visible light. Furthermore, it turns the negative effect of NaCI normally observed in homogeneous catalysis into positive one. The catalytic reaction can proceed at a wide pH range from acidic to alkaline. In 60 min, more than 98% of AR1 was eliminated at initial pH 2. In 90 min, about 40% of the carbon was found mineralized as determined by the analysis of the residual total organic carbon. The high-performance liquid chromatography result indicated that a substantial amount of the starting AR1 was converted to other organic products, while gas chromatography/mass spectrometry analysis showed the rest of the carbon existed mainly as small molecular biodegradable aliphatic carboxylic compounds such as oxalic acid, malonic acid, and maleic acid, etc. Co-TDTAPc-F is stable, causes no secondary pollution, and remains efficient in repetitive test cycles with no obvious degradation of catalytic activity. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman spectroscopy (SERS) was used to detect and characterize polyatomic cations and molecules that were electrosprayed into the gas phase and soft-landed in vacuum on plasma-treated silver substrates. Organic dyes such as crystal violet and Rhodamine B, the nucleobase cytosine, and nucleosides cytidine and 2′-deoxycytidine were immobilized by soft landing on plasma-treated metal surfaces at kinetic energies ranging from near thermal to 200 eV. While enhancing Raman scattering 105–106-fold, the metal surface effectively quenches the fluorescence that does not interfere with the Raman spectra. SERS spectra from submonolayer amounts of soft-landed compounds were sufficiently intense and reproducible to allow identification of Raman active vibrational modes for structure assignment. Soft-landed species appear to be microsolvated on the surface and bound via ion pairing or π-complexation to the Ag atoms and ions in the surface oxide layer. Comparison of spectra from soft-landed and solution samples indicates that the molecules survive soft landing without significant chemical damage even when they strike the surface at hyper-thermal collision energies. [ABSTRACT FROM AUTHOR]

New organic dyes composed of the benzo[b]furan donor, thiophene-conjugated bridge, and cyano acrylic acid acceptor have been newly synthesized through the one-pot coupling cyclization key step. Nanocrystalline TiO2 dye-sensitized solar cell was fabricated using this dye. A solar-to-electric conversion efficiency of 6.65% and 4.70% is achieved with 1 and 2, respectively. [ABSTRACT FROM AUTHOR]

An organic dye, SAMSA, bound to gold nanoparticles, displays random photoactivated fluorescence blinking whose rate depends on the size of the nanoparticles. We report experiments indicating that (1) the dye emission wavelength is red-shifted (10−30 nm) by applying an external low voltage (1−10 V) and that (2) the fluorescence emission of single dyes can be resonantly driven by tuning the alternating external bias frequency from 1 to 3 Hz, depending on the nanoparticle size. These properties appear highly valuable and promising for devising light emitting nanostructures. [ABSTRACT FROM AUTHOR]

We present a joint theoretical and experimental work aimed to understand the spectroscopic behavior of multipolar dyes of interest for nonlinear optics (NLO) applications. In particular, we focus on the occurrence of broken-symmetry states in quadrupolar organic dyes and their spectroscopic consequences. To gain a unified description, we have developed a model based on a few-state description of the charge-transfer processes characterizing the low-energy physics of these systems. The model takes into account the coupling between electrons and slow degrees of freedom, namely, molecular vibrations and polar solvation coordinates. We predict the occurrence of symmetry breaking in either the ground or first excited state. In this respect, quadrupolar chromophores are classified in three different classes, with distinctively different spectroscopic behavior. Cases of true and false symmetry breaking are discriminated and discussed by making resort to nonadiabatic calculations. The theoretical model is applied to three representative quadrupolar chromophores: their qualitatively different solvatochromic properties are connected to the presence or absence of broken-symmetry states and related to two-photon absorption (TPA) cross-sections. The proposed approach provides useful guidelines for the synthesis of dyes for TPA application and represents a general and unifying reference frame to understand energy-transfer processes in multipolar molecular systems, offering important clues to understand basic properties of materials of interest for NLO and energy-harvesting applications. [ABSTRACT FROM AUTHOR]