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Self-assembled systems of water soluble metal 8-hydroxyquinolates with surfactants and conjugated polyelectrolytes for optical sensing, light harvesting and charge transport
Abstract
We have studied the interaction of 8-hydroxyquinoline-5-sulfonate (8-HQS) with the metal ions Al(III) and Zn(II) in aqueous solution in the presence of tetraalkylammonium surfactants using UV/vis absorption, fluorescence, NMR spectroscopy and electrical conductivity measurements, complemented by DFT calculations and molecular dynamics (MD) simulations. Under appropriate conditions, complexes between 8-HQS and metal ions form rapidly, and have similar electronic, spectroscopic and photophysical properties to the corresponding metal quinolates, such as Alq3. These interact with the cationic surfactants, leading to marked increases in fluorescence intensity. However, significant differences are seen in the behavior of the two metal ions. With aluminium, a stable [Al(8-QS)3]3- anion is formed, and interacts, predominantly through electrostatic interactions, with the surfactant, without disrupting the metal ion coordination sphere. In contrast, with Zn(II), there is competition between metal ion and surfactants in the interaction with 8-HQS, although the [Zn(8-QS)2(H2O)2]2- species is stable at appropriate pH and surfactant concentration. The studies are extended to systems with the conjugated polyelectrolyte (CPE) poly-(9,9-bis(6-N,N,N-trimethylamonium)hexyl)–fluorene-phenylene) bromide (HTMA-PFP), which has a similar alkylammonium chain to the surfactants. Mixing metal salt, 8-HQS and HTMA-PFP in the presence of a nonionic surfactant leads to formation of metal complex/CPE supramolecular assemblies between the conjugated polyelectrolyte and metal/8-HQS complex, as demonstrated by electronic energy transfer. The potential of these systems in sensing, light harvesting, and electron injection/transport layers in organic semiconductor devices is discussed.
... Another interesting finding involves fluorene-based conjugated polyelectrolytes (CPEs) [10]. Conjugated polyelectrolytes tend to aggregate in water, which limits its electrical conductivity and photoluminescence for practical applications [11][12][13]. Surfactants and co-solvents can be efficiently used to promote the disaggregation of CPEs [10,14,15]. Knaapila et al. [16] have found that poly(vinyl alcohol), with a molecular weight around 30000-40000 g mol −1 also leads to the breakup of CPE structure, highlighting the occurrence of hydrophobic interactions promoting the disaggregation process. ...
The Taylor dispersion technique has been used for measuring the tracer diffusion coefficients, D⁰Tracer, for poly (vinyl alcohol) (PVA) in aqueous systems containing two specific electrolytes (i.e., NaCl and Na2SO4) at three different concentrations (0.020, 0.050 and 0.10 mol dm⁻³), and at 25 °C. The selection of these salts has been based on the Hofmeister series of cations and anions, which order the ions with respect to the behavior of some macroscopic properties (such as, surface tension) and that can be interpreted as an effect salting-out or salting-in, depending if the target ions are strongly (kosmotropic) or a weakly hydrated (chaotropic). In this work, we have been used the combination of two kosmotropic ions (Na2SO4) and another one with a kosmotropic cation and a chaotropic anion (NaCl).
These data, complemented by NMR measurements, permit us to have a better understanding about the effect of these sodium salts on transport and thermodynamic behaviour of PVA.
... Aluminum(III), magnesium(II) and zinc(II) quinolinolato complexes, particularly, show pronounced fluorescence properties although a free ligand emits weak fluorescence. The metal quinolinolato complexes have also been functionalized in organic light emitting devices [14,15]. In terms of separation chemistry, the facilitated ion transfer (electrochemical solvent extraction) of metal ions by the lipophilic HQ has been studied at liquid|liquid interfaces under electrochemical control, where a slight partitioning of ligands into the aqueous phase occurs, accompanied by the complexation homogeneously, and finally, the metal complexes are transferred into the organic phase [16][17][18][19]. ...
The transfer mechanism and adsorption state of water-soluble 8-quinolinolate complexes were studied at the water|1,2-dichloroethane interface by electrochemical and spectroelectrochemical techniques. The interfacial affinities of the metal complexes of 8-hydroxyquinoline-5-sulfonate (QS) were estimated as AlQS33−, CuQS22− > ZnQS22−. Potential modulated fluorescence spectroscopy revealed the potential-driven process of fluorescent QS complexes, where Al(III) and Zn(II) complexes were transferred across the interface accompanied by the adsorption at the aqueous side of the interface. The adsorption state and preferential molecular orientation of these complexes were analyzed in detail by polarization-modulation total internal reflection fluorescence (PM-TIRF) spectroscopy. The PM-TIRF results showed that the square-planar 1:2 complexes, AlQS2− and ZnQS22−, were oriented relatively in parallel to the interface and approximately identical to the aqueous species. The adsorption behavior of the Zn(II) complex of tridentate 8-hydroxyquinoline-2-carboxylate (QC) ligand was also investigated, and ZnQC22− exhibited a strong interfacial affinity with intermediate spectral features between the aqueous and organic species.
Following previous studies on the complexation in aqueous solutions of 8-hydroxyquinoline-5-sulfonate (8-HQS) with the trivalent metal ions, Al(III) and Ga(III) and various other metal ions, using multinuclear NMR, DFT calculations, UV-vis absorption and luminescence techniques, we have extended our studies on 8-HQS complexation to the trivalent metal ion In(III). The study combines the high sensitivity of luminescence techniques and the selectivity of multinuclear NMR spectroscopy with the structural details accessible through DFT calculations, and aims to obtain a complete understanding of the complexation between the In3+ metal ion and 8-HQS, and how this influences the luminescence behaviour.
A full speciation study has been performed and, as has been reported for the complexes of 8-hydroxyquinoline (8-HQ), the dominant complexes of 8-HQS with In(III) show marked differences in the complexation behaviour when compared with the equivalent complexes with the other Group 13 cations Al(III) and Ga(III). While all three complexes have a 1 : 3 (metal:ligand) stoichiometry, those with Al(III) and Ga(III) show a mer- geometry of the ligands around the metal centre, whereas the fac-geometry is observed for the complexes with In(III).
On binding to metal ions, 8-HQS shows a marked increase in the intensity of the fluorescence emission band compared to that of the virtually non-luminescent free ligand. However, the increase for In(III) is less pronounced than with Al(III) or Ga(III). These observations have important implications for the application of the complexes in sensing, light emitting devices (e.g. OLEDs), or as electron transport layers in photovoltaics for solar energy conversion. Furthermore, surfactant complexation is known to improve the fluorescence intensity in metal complexes with 8-HQS, by inhibiting the ligand exchange, as we have reported for complexes of HQS with Al(III) and Ga(III). Accordingly, in view of the development of applications in either sensing or optoelectronics, our interest also includes the study of HQS complexes of In(III) in the presence of cationic surfactants, in comparison with previous results with Al(III) and Ga(III).
Multinuclear (1H and 13C) NMR, and Raman spectroscopy, combined with DFT calculations, provide detailed information on the complexation between the U(VI) oxoions and 8-hydroxyquinoline-5-sulfonate (8-HQS) in aqueous solution. Over the concentration region studied, U(VI) oxoions (uranyl ions) form one dominant complex with 8-HQS in water in the pH range 3-6, a mononuclear 1:2 (metal:ligand) complex, with the metal centre (UO22+) coordinated to two 8-HQS ligands, together with one or more water molecules. An additional minor, 1:1 complex, has also been detected for solutions with 1:1 metal:ligand molar ratio. A geometry of the dominant complex is proposed based on the combination of NMR and Raman results with DFT calculations. Further information on the electronic structure of the complex has been obtained from UV/visible absorption and luminescence spectra. The complex between U(VI) and 8-HQS is only weakly luminescent, in contrast to what has been observed with this ligand and many other metal ions. We suggest this is due to the presence of low-lying ligand-to-metal charge transfer (LMCT) states below the emitting ligand-based and uranyl based levels which quench their emission. These studies have fundamental importance and are also relevant in the context of environmental studies, and the water soluble ligand 8-HQS has been chosen for application in uranium remediation of aqueous environments.
Flexible conductive polyelectrolyte multilayer films built upon anionic poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and cationic poly(3-hexylthiophene)-based conjugated polyelectrolytes (P3HT-R) containing imidazolium, pyridinium and phosphonium ionic groups were prepared using electrostatic layer-by-layer assembly. Adsorbed amount of each polyelectrolyte strongly increases when divalent cations (Ba²⁺) are employed as electrolyte and when the rinsing step is avoided during the build-up. The electrical properties of these (P3HT-R/PEDOT:PSS)n multilayer films were then investigated using the van der Pauw method leading to an average conductivity of ∼2 S m⁻¹. Semiconducting behavior of these organic coatings was demonstrated by the direct relationship between the conductivity and the temperature. (P3HT-R/PEDOT:PSS)n multilayer films exhibited p-type semiconducting behavior as showed by Seebeck measurements. Finally, these films were successfully deposited onto flexible polymer sheets and their conductivity was found to be not affected by applying a bending stress.
We report on a multiscale polymer-within-polymer structure of the cationic conjugated polyelectrolyte poly{[9,9-bis(6′-N,N,N-trimethylammonium)hexyl]fluorene–phenylene} (HTMA-PFP) in aqueous poly(vinyl alcohol) (PVA) sol. Molecular dynamics simulations and small-angle neutron scattering (SANS) data show that HTMA-PFP forms aggregates in water but becomes entangled by PVA (with a 1:1 molar ratio of HTMA-PFP to PVA) and eventually immersed in PVA clusters (with the ratio 1:4). This is attributed to the hydrophobic–hydrophilic balance. Contrast variation data with regular and deuterated PVA support a rigid body model, where HTMA-PFP is confined as locally isolated, but closely located, chains within PVA clusters, which alter correlation distances within the system. These results are supported by enhanced photoluminescence (PL) and ionic conductivity which, together with a red-shift in UV/vis absorption spectra, indicate the breakup of HTMA-PFP aggregates upon PVA addition.
Multinuclear (1H, 13C, 95Mo and 183W) NMR spectroscopy, combined with DFT calculations, provides detailed information on the complexation between the Mo(VI) and W(VI) oxoions and 8-hydroxyquinoline-5-sulfonate (8-HQS) in aqueous solution. Over the concentration region studied, Mo(VI) and W(VI) oxoions form three homologous complexes with 8-HQS in water in the pH range 2-8. Two of these, detected at pH < 6, are mononuclear 1:2 (metal:ligand) isomers, with the metal centre (MO22+) coordinated to two 8-HQS ligands. An additional complex, dominant at slightly higher pH values (5 to 8) for solutions with 1:1 metal:ligand molar ratio, has a binuclear M2O52+ centre coordinated to two 8-HQS ligands. The two metal atoms are bridged by three oxygen atoms, two coming from 8-HQS, together with the M-O-M bridge of the bimetallic centre. We show that the long-range exchange corrected BOP functional with local response dispersion (LCBOPLRD), together with explicit solvent molecules, leads to geometries that readily converged to equilibrium structures having realistic bridging O8-HQS-M bonds. Previous attempts to calculate structures of such binuclear complexes using DFT with the B3LYP functional have failed due to difficulties in treating the weak interaction in these bridged structures. We believe that the LCBOPLRD method may be of more general application in theoretical studies in related binuclear metal complexes. UV/visible absorption and luminescence spectra of all complexes have also been recorded. The complex between Mo(VI) and 8-HQS is only weakly luminescent, in contrast to what has been observed with this ligand and many other metal ions. We suggest this is due to the presence of low-lying ligand-to-metal charge transfer (LMCT) states close to the emitting ligand-based level which quench the emission. However, with W(VI), DFT calculations show the LMCT states are now much higher in energy than the ligand based levels, leading to a marked increase in fluorescence.
The efficiency of biological photosynthesis results from the exquisite organization of photoactive elements that promote rapid
movement of charge carriers out of a critical recombination range. If synthetic organic photovoltaic materials could mimic
this assembly, charge separation and collection could be markedly enhanced. We show that micelle-forming cationic semiconducting
polymers can coassemble in water with cationic fullerene derivatives to create photoinduced electron-transfer cascades that
lead to exceptionally long-lived polarons. The stability of the polarons depends on the organization of the polymer-fullerene
assembly. Properly designed assemblies can produce separated polaronic charges that are stable for days or weeks in aqueous
solution.
1H, 13C and 51V NMR spectra, DFT calculations, and UV/visible absorption and luminescence spectra are used to study complexation of 8-hydroxyquinoline-5-sulfonate (8-HQS) with vanadium(V). A full speciation study over the concentration region studied shows that V(V) oxoions form three complexes in the pH range 4–7. Geometries are proposed based on NMR and DFT calculations. Dominant species are 1 : 2 (metal : ligand)
mononuclear six-coordinated isomers with an almost octahedral geometry, having the metal centre
coordinated to two 8-HQS ligands, and only differing in the arrangement of the donor groups. A minor
binuclear complex species was also identified, and possesses two five coordinated metal centres, with
distorted trigonal bipyramidal geometry, bridged by two coordinated 8-HQS molecules. Upon binding to V(V),
marked changes are seen in UV/visible absorption spectra. However, in contrast to other metals (Al(III), Ga(III), Zn(II)), the complexes are only weakly luminescent; this is suggested to be due to quenching of the emission by low-lying ligand-to-metal (LMCT) states close to the emitting ligand-based excited state.
This Perspective describes electronic materials whose molecular structure permits extreme deformation without the loss of electronic function. This approach—“molecularly stretchable” electronics—is complementary to the highly successful approaches enabled by stretchable composite materials. We begin by identifying three general types of stretchable electronic materials: (1) random composites of rigid structures sitting atop or dispersed in an elastic matrix, (2) deterministic composites of patterned serpentine, wavy, or fractal structures on stretchable substrates, and (3) molecular materials—noncomposite conductors and semiconductors—that accommodate strain intrinsically by the rational design of their chemical structures. We then identify a short-term and a long-term goal of intrinsically stretchable organic electronics: the short-term goal is improving the mechanical stability of devices for which commercialization seems inevitable; the long-term goal is enabling of electronic devices in which every component is highly elastic, tough, ductile, or some combination thereof. Finally, we describe our and others’ attempts to identify the molecular and microstructural determinants of the mechanical properties of organic semiconductors, along with applications of especially deformable materials in stretchable and mechanically robust devices. Our principal conclusion is that while the field of plastic electronics has achieved impressive gains in the last several years in terms of electronic performance, all semiconducting polymers are not equally “plastic” in the sense of “deformable”, and thus materials tested on glass substrates may fail in the real world and may not be amenable to stretchable—or even modestly flexible—systems. The goal of this Perspective is to draw attention to the ways in which organic conductors and semiconductors specifically designed to accommodate large strains can enable highly deformable devices, which embody the original vision of organic electronics.
Multinuclear (1H, 13C and 71Ga) magnetic resonance spectroscopy (1D and 2D), DFT calculations and luminescence techniques have been used to study 8-hydroxyquinoline-5-sulfonate (8-HQS) and its complexes with Ga(iii) in aqueous solutions. The study combines the high sensitivity of luminescence techniques and the selectivity of multinuclear NMR spectroscopy with the structural details accessible through DFT calculations, and aims to obtain a complete understanding of the complexation between the Ga3+ ion and 8-HQS, and how this influences the luminescence behaviour. A full speciation study has been performed on this system and three complexes detected, with (metal : ligand) 1 : 1, 1 : 2 and 1 : 3 stoichiometries, the results being consistent with those previously found for the system Al(iii)-8-HQS. Complexation in these systems is relevant to their potential biomedical, sensing and optoelectronic applications. On binding to Ga(iii), a marked increase is seen in the intensity of the 8-HQS fluorescence ban
The thermodynamics of micelle formation of ionic surfactants, sodium dodecyl sulfate (SDS), cetyl pyridinium chloride (CPC), and sodium salt of dioctyl sulfosuccinate (Aerosol OT or AOT) have been thoroughly assessed from microcalorimetric, conductometric, and tensiometric measurements, and the results have been rationalized in terms of physicochemical concepts and relations. The past and recent critical micellar concentration (CMC) data on SDS have been considered and compared; the CMCs of SDS, CPC, and AOT determined in this and earlier studies have been processed to evaluate the energetic parameters (free energy, enthalpy, entropy, and heat capacity) of micellization. The effect of the salt, NaCl, on the CMC and energetics of micellization of the surfactants has been also examined.
Multinuclear ((1)H, (13)C and (27)Al) magnetic resonance spectroscopy (1D and 2D), DFT calculations and fluorescence have been used to study the complexation of 8-hydroxyquinoline-5-sulfonate (8-HQS) with Al(iii). The study combines the high sensitivity of luminescence techniques, the selectivity of multinuclear NMR spectroscopy with the structural details accessible through DFT calculations, and aims to provide a detailed understanding of the complexation between the Al(3+) ion and 8-HQS. A full speciation study has been performed and over the concentration region studied, the Al(3+) ion forms complexes with 8-HQS in an aqueous solution in the pH range 2-6. At higher pH, the extensive hydrolysis of the metal limits complexation. Using Job's method, three complexes were detected, with 1 : 1, 1 : 2 and 1 : 3 (metal : ligand) stoichiometries. These results are in agreement with those previously reported using potentiometric and electrochemical techniques. The geometries of the complexes are proposed based on the combination of NMR results with optimized DFT calculations. All the complexes in aqueous solutions at 25 °C are mononuclear species, and have an approximately octahedral geometry with the metal coordinated to one molecule of 8-HQS and four molecules of water (1 : 1 complex), two molecules of 8-HQS and two molecules of water mutually cis (1 : 2 complex), and to three molecules of 8-HQS in non-symmetrical arrangement (mer-isomer), for the 1 : 3 (metal : ligand) complex. On binding to Al(iii), 8-HQS shows a more marked fluorescence than the weakly fluorescent free ligand. In addition, as previously noted, there are marked changes in the absorption spectra, which support the use of 8-HQS as a sensitive optical sensor to detect Al(3+) metal ions in surface waters and biological fluids. These complexes also show potential for applications in organic light emitting diodes (OLEDs).
Quaternization of poly-(9,9-bis(6'-bromohexyl)fluorenephenylene by treatment with trimethylamine gas was used to obtain a water soluble ammonium salt copolymer. The neutral copolymer containing fluorene/phenylene alternating repeating units was obtained by a palladium-catalyzed Suzuki coupling reaction. This strategy could be applied to prepare water soluble conjugated polymers with the ability to change the charge functionality. The polymers were characterized by gel permeation chromatography (GPC), H-1 and (CNMR)-C-13 spectroscopy, FT-IR spectroscopy, and thermogravimetric analysis (TGA). The neutral polymer was stable to over 300degreesC, while the cationic polymer begins to degrade at 120degreesC with a progressive loss of mass at 290degreesC. The optical properties of the polymers were investigated in solution and solid phases by UV/VIS and fluorescent spectroscopy. Mesoporous silica thin films were prepared as a host matrix for the fluorescent copolymers.
Background
The Avogadro project has developed an advanced molecule editor and visualizer designed for cross-platform use in computational chemistry, molecular modeling, bioinformatics, materials science, and related areas. It offers flexible, high quality rendering, and a powerful plugin architecture. Typical uses include building molecular structures, formatting input files, and analyzing output of a wide variety of computational chemistry packages. By using the CML file format as its native document type, Avogadro seeks to enhance the semantic accessibility of chemical data types.
Results
The work presented here details the Avogadro library, which is a framework providing a code library and application programming interface (API) with three-dimensional visualization capabilities; and has direct applications to research and education in the fields of chemistry, physics, materials science, and biology. The Avogadro application provides a rich graphical interface using dynamically loaded plugins through the library itself. The application and library can each be extended by implementing a plugin module in C++ or Python to explore different visualization techniques, build/manipulate molecular structures, and interact with other programs. We describe some example extensions, one which uses a genetic algorithm to find stable crystal structures, and one which interfaces with the PackMol program to create packed, solvated structures for molecular dynamics simulations. The 1.0 release series of Avogadro is the main focus of the results discussed here.
Conclusions
Avogadro offers a semantic chemical builder and platform for visualization and analysis. For users, it offers an easy-to-use builder, integrated support for downloading from common databases such as PubChem and the Protein Data Bank, extracting chemical data from a wide variety of formats, including computational chemistry output, and native, semantic support for the CML file format. For developers, it can be easily extended via a powerful plugin mechanism to support new features in organic chemistry, inorganic complexes, drug design, materials, biomolecules, and simulations. Avogadro is freely available under an open-source license from
http://avogadro.openmolecules.net.
A description of the ab initio quantum chemistry package GAMESS is presented. Chemical systems containing atoms through radon can be treated with wave functions ranging from the simplest closed-shell case up to a general MCSCF case, permitting calculations at the necessary level of sophistication. Emphasis is given to novel features of the program. The parallelization strategy used in the RHF, ROHF, UHF, and GVB sections of the program is described, and detailed speecup results are given. Parallel calculations can be run on ordinary workstations as well as dedicated parallel machines. © John Wiley & Sons, Inc.
In this article, we present a new LINear Constraint Solver (LINCS) for molecular simulations with bond constraints. The algorithm is inherently stable, as the constraints themselves are reset instead of derivatives of the constraints, thereby eliminating drift. Although the derivation of the algorithm is presented in terms of matrices, no matrix matrix multiplications are needed and only the nonzero matrix elements have to be stored, making the method useful for very large molecules. At the same accuracy, the LINCS algorithm is three to four times faster than the SHAKE algorithm. Parallelization of the algorithm is straightforward. © 1997 John Wiley & Sons, Inc. J Comput Chem18: 1463–1472, 1997
The molecular weight of an electron donor-conjugated polymer is as essential as other well-known parameters in the chemical structure of the polymer, such as length and the nature of any side groups (alkyl chains) positioned on the polymeric backbone, as well as their placement, relative strength, the ratio of the donor and acceptor moieties in the backbone of donor–acceptor (D–A)-conjugated polymers, and the arrangement of their energy levels for organic photovoltaic performance. Finding the “optimal” molecular weight for a specific conjugated polymer is an important aspect for the development of novel photovoltaic polymers. Therefore, it is evident that the chemistry of functional conjugated polymers faces major challenges and materials have to adopt a broad range of specifications in order to be established for high photovoltaic performance. In this review, the approaches followed for enhancing the molecular weight of electron-donor polymers are presented in detail, as well as how this influences the optoelectronic properties, charge transport properties, structural conformation, morphology, and the photovoltaic performance of the active layer.
The kinetically inert chromium(III) tris-(8-hydroxyquinolinate), Crq3, has been synthesized, crystallized from 90% methanol-water, and characterized by MALDI-TOF mass spectrometry, thermogravimetry, FTIR, NMR spectroscopy, and X-ray powder diffraction. It is formed as a methanol solvate, but solvent can be removed by heating. Large paramagnetic shifts and spectral broadening in 1H NMR spectra indicate electron delocalization between metal and ligand. DFT calculations show it is present as the meridional isomer, with the HOMO largely based on one of the metal 3d orbitals and the LUMO essentially localized on the ligands. Cyclic voltammetry (CV) in acetonitrile solutions shows four oxidation peaks and two, less intense reduction waves on first scan. The HOMO energy determined from the first oxidation peak is fairly close to that obtained by DFT, in agreement with this being mainly metal based. Although the number of peaks decreases on subsequent CV scans, the complex shows markedly enhanced electrochemical stability compared with aluminium(III) tris-(8-hydroxyquinolinate). Solution UV/visible absorption and solid diffuse reflectance spectra have a weak, long wavelength band, assigned to the metal based d-d transition, in addition to the normal, ligand based, bands seen in metal quinolates. The energy of the lowest energy band is identical to the HOMO-LUMO separation obtained by cyclic voltammetry, in agreement with the above description. The compound is only weakly luminescent, in contrast to many other metal quinolates, due to the lowest energy transition being metal rather than ligand based. The potential of this compound as an electron transporting/hole blocking layer in optoelectronic devices is indicated.
The charge transport and recombination in white-emitting polymer light- emitting diodes (PLEDs) are studied. The PLED investigated has a single emissive layer consisting of a copolymer in which a green and red dye are incorporated in a blue backbone. From single-carrier devices the effect of the green- and red-emitting dyes on the hole and electron transport is determined. The red dye acts as a deep electron trap thereby strongly reducing the electron transport. By incorporating trap-assisted recombination for the red emission and bimolecular Langevin recombination for the blue emission, the current and light output of the white PLED can be consistently described. The color shift of single-layer white-emitting PLEDs can be explained by the different voltage dependencies of trap-assisted and bimolecular recombination.
Polymer Properties are Governed by the Choice of MonomersThe Molecular Weight is an Important ParameterDissolving a Polymer Can be a ProblemPolymers in Solution Can be Characterized by Viscosity MeasurementsPolymer Solutions May Undergo Phase SeparationPolymers Containing Oxyethylene Groups Phase-separate upon Heating in Aqueous SystemsSolvents and Surfactants Have Large Effects on Polymer SolutionsThe Solubility Parameter Concept is a Useful Tool for Finding the Right Solvent for a PolymerThe Theta Temperature is of Fundamental ImportanceThere are Various Classes of Water-soluble PolymersPolyelectrolytes are Charged PolymersPolymer Configurations Depend on Solvent ConditionsBibliography
The interaction of the water soluble conjugated polyelectrolyte (CPE) poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} (PBS-PFP) (degree of polimerization, DP, ~3-6), with various concentrations of a homologous series of oppositely charged amphiphilic phenylenevinylene oligomers was investigated in water:dioxane mixtures and in aqueous micellar solutions of the non-ionic surfactant n-dodecylpentaoxyethylene glycol ether (C12E5). The excellent spectral overlap between the CPE fluorescence and the conjugated oligoelectrolyte (COE) absorption indicates that energy transfer between these is a highly favoured process, and can be tuned by changing the COE chain length. This is supported by time-resolved fluorescence data. The overall results provide support for different types of self-assembly, which are sensitive to the solvent environment and to the size of the phenylenevinylene oligoelectrolyte chain. It is suggested that large aggregates are formed in water:dioxane mixtures, while decorated core-shell structures are present in the surfactant solutions.
Bis(8-hydroxyquinolate-5-sulfonate)zinc anion (ZQS2−) and dodecyl sulfonate anion (DDS−) have been co-intercalated into the layered double hydroxidehost (MnAl LDH, M2+ = Mg, Zn, n = 2, 3) by a hydrothermal co-precipitation method, with samples denoted as DDS–ZQS(x%)/LDH (x stands for the molar percentage content of ZQS with respect to DDS + ZQS). The structure and chemical composition of the resulting compounds were characterized by X-ray diffraction (XRD), FT-IR and elemental analysis. Their films obtained by the solvent evaporation method have a well-defined c-orientation confirmed by XRD and scanning electron microscopy (SEM). Thermogravimetry and differential thermal analysis (TG–DTA) results elucidate that the thermal stability of ZQS is enhanced upon co-intercalation. The fluorescent studies show that the luminous behavior (wavelength, intensity, lifetime and quantum yield) of ZQS is correlated with the fluorophore content and can be modulated by controlling the host–guest and guest–guest interaction through changing the ratio of DDS to ZQS, metal species and positive charge density of the LDH host layer. DDS–ZQS(5%)/Mg2Al LDH exhibits the optimal luminous intensity and the longest lifetime among the DDS–ZQS(x%)/Mg2Al LDH samples.
Electronic energy transfer has been studied between the cationic conjugated polyelectrolyte, poly{9,9-bis[6-N,N,N-trimethylammonium)hexyl]fluorene-co-1,4-phenylene} dibromide (HTMA-PFP), and three, oppositely charged meso-tetrakis-phenylporphyrinsulfonates in buffered (pH = 9.2), 4% (v/v) dimethyl sulfoxide-water (DMSO-water) solutions using steady-state and time-resolved fluorescence. Energy transfer was indicated by the decrease in intensity of the fluorescence band of the HTMA-PFP donor, by a corresponding increase in fluorescence of the porphyrin acceptors, by a band in the excitation spectrum of the porphyrin corresponding to the polymer absorption, and by the fact that the decay of the polymer emission observed at 423 nm was accompanied by the grow-in of porphyrin emission at 650 nm in time-resolved measurements. It is suggested that the energy transfer may involve upper excited states of the acceptor. The Förster equation and the experimental spectral overlap between donor fluorescence and acceptor absorption were used to calculate Förster radii for the three systems. Both steady-state and dynamic Stern-Volmer plots were nonlinear at high acceptor concentrations, and quenching rate constants calculated from the slopes of the initial linear region and the HTMA-PFP fluorescence lifetime were orders of magnitude greater than expected for a diffusion-controlled process, strongly supporting the idea that energy transfer occurs in self-assembled species formed by association (through ion pairing) of the polymer and porphyrins. There are indications that these aggregates involve more than one polymer chain. Picosecond time-resolved measurements on the HTMA-PFP fluorescence decay showed a short-lived component, attributed to the energy-transfer step, and two longer lived decays, which may be associated with exciton migration along the chain and the fluorescence decay of the polymer backbone, respectively. From considerations of the probable distance between donor and acceptor it is suggested that the Forster mechanism, assuming point dipoles, is inadequate for this system and that more detailed calculations, considering the actual sizes of the donor and acceptor, are necessary.
An optical sensor responding to Al(III), Mg(II), Zn(II) and Cd(II) is prepared by immobilizing quinolin-8-ol-5-sulfonate (QS) on an ion-exchange resin and attaching the resin to the end of a trifurcated fiber-optic bundle. Immobilization leads to weak fluorescence from QS and causes shifts in the fluorescence spectra of the QS/metal complexes. Detection limits for the metal ions studied are all below 1 × 10−6 M. Response to metal ion concentration is nonlinear. The shape of the response fits a model that assumes a 1:1 metal/QS chelate is formed. Forrnation constants for immobilized QS complexes calculated from the model are similar to those observed for dissolved QS. Immobilized and dissolved QS behave similarly with respect to pH and interferences.
This paper reports optical absorption spectra of oxidized fluorene copolymers obtained by chemical oxidation with Ce(IV) and by pulse radiolysis experiments in chlorinated solvents. Comparison of the results observed by the two techniques is used to provide spectral data on the copolymer radical ions and information on stability of the oxidized species. In addition, a detailed quantum chemical characterization is presented, concerning the electronic and optical properties of three series of charged oligomers containing alternating fluorene and phenylene or thienylene or benzothiadiazole units, respectively. The introduction of the comonomer strongly influences the optical properties, leading to a red shift in the absorption spectra of the charged oligomers. This shift is more pronounced in the case of fluorene benzothiadiazole anions due to the strong electron-accepting character of the benzothiadiazole moieties. The charge distribution of the fluorene benzothiadiazole anion is different from that corresponding to fluorene phenylene and fluorene thienylene anions. The negative charge of the latter oligomers is evenly distributed over the fluorene units, while the former oligomer localizes the negative charge on the benzothiadiazole units. The charge distribution correlates with the optical absorption spectra. When the positive charge is localized on a different unit than the negative charge, the cation and anion spectra are different. Similar spectra are obtained if both the positive and negative charges are localized on the same unit.
Four different methods for the calculation of the formation constants of fluorescing complexes are discussed. The methods were used to determine constants for the complexes of aluminum(III), gallium(III) and indium(III) with 8-quinolinol-5-sulfonate anion.RésuméOn examine quatre méthodes différentes pour calculer les constantes de formation de complexes fluorescents, en particulier aluminium(III), gallium(III) et indium(III) avec le 8-quinolinol-5-sulfonate.ZusammenfassungVier verschiedene Methoden zur Berechnung der Bildungskonstanten fluoreszierender Komplexe werden diskutiert. Die Methoden wurden auf die Bestimmung der Konstanten für die Komplexe von Aluminium(III), Gallium(III) und Indium-(III) mit dem 8-Hydroxychinolin-5-sulfonat-Anion angewendet.
A new water soluble fluorene-based polyelectrolyte containing on-chain porphyrin units has been synthesized via Suzuki coupling, for use in optoelectronic devices. The material consist of a random copolymer of poly{1,4-phenylene-[9,9-bis(4-phenoxy butylsulfonate)]fluorene-2,7-diyl} (PBS-PFP) and a 5,15-diphenylporphyrin (DPP). The energy transfer process between the PBS-PFP units and the porphyrin has been investigated through steady state and time-resolved measurements. The copolymer PBS-PFP-DPP displays two different emissions one located in the blue region of the spectra, corresponding to the fluorene part and another in the red due to fluorescent DPP units either formed directly or by exciton transfer. However, relatively inefficient energy transfer from the PFP to the on-chain porphyrin units was observed. We compare this with a system involving an anionic blue light-emitting donor PBS-PFP and a anionic red light-emitting energy acceptor meso-tetrakisphenylporphyrinsulfonate (TPPS), self-assembled by electrostatic attraction induced by Ca2+. Based on previous studies related to chain aggregation of the anionic copolymer PBS-PFP, two different solvent media were chosen to further explore the possibilities of the self-assembled system: dioxanewater and aqueous nonionic surfactant n-dodecylpentaoxyethylene glycol ether (C12E5). In contrast, with the on-chain PBS-PFP-DPP system the strong overlap of the 0-0 emission peak of the PBS-PFP and the Soret absorption band of the TPPS results in an efficient Forster transfer. This is strongly dependent on the solvent medium used. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Degradation of the materials in organic light-emitting devices (OLEDs) is the major impediment for the development of economically feasible, highly efficient and durable devices for commercial applications. Even though this chemical degradation is complex and the least understood of the different degradation modes in OLEDs, scientists were successful in providing insight into some of the responsible processes. In this progress report we will review recent advances in the elucidation of chemical degradation mechanisms: First possible reasons for defect formation and the most common and important methods to investigate those processes are covered before discussing the reactions and their products for the different types of materials present in a device. We summarize commonalities in the occurring mechanisms, and identify structural features and moieties that can be detrimental to operational stability. Some of the resulting implications on the development of new materials are presented and backed by concrete examples from literature.
The cationic, all-conjugated AB diblock copolymer poly[9,9-bis(2-ethylhexyl)fluorene]-b-poly[3-(6-trimethylammoniumhexyl) thiophene] bromide (PF2/6-b-P3TMAHT) shows dual fluorescence from the poly(fluorene) (PF) and poly(thiophene) (PT) blocks. A comparison of fluorescence quenching of the cationic PT block fluorescence with unquenched PF block provides a sensitive ratiometric method for anion sensing. The application to analysis of halide ions, single- and double-stranded DNA is demonstrated. High selectivity is observed with halide ions, with the strongest quenching being seen with iodide. The quenching with DNA can be used for nucleic acid quantification at sub-μM concentrations.
Organic photoconductors sensitive to blue, green, and red light were fabricated using coumarin 6 (C6)-doped poly(m-hexoxyphenyl)phenylsilane (PHPPS), rhodamine 6G (R6G)-doped polymethylphenylsilane (PMPS), and zinc phthalocyanine (ZnPc)/tris-8-hydroxyquinoline aluminum (Alq3) double layer, respectively. Selectivities of the spectral responses of these films were good enough to divide the incident light into three color components, indicating the possibility of color separation without prism for video cameras. The quantum efficiency of a ZnPc/Alq3 double-layer film is over an order of magnitude better than those of C6/PHPPS and R6G/PMPS blend films due to the dissociation of electron–hole pair generated at the interface between ZnPc and Alq3. © 2003 American Institute of Physics.
The construction of a very simple electronic device, a rectifier, based on the use of a single organic molecule is discussed. The molecular rectifier consists of a donor pi system and an acceptor pi system, separated by a sigma-bonded (methylene) tunnelling bridge. The response of such a molecule to an applied field is calculated, and rectifier properties indeed appear.
The interaction between the vanadate ion (VO3-, i.e. vanadium (V)) and the carbohydrates sucrose, glucose and fructose has been studied in aqueous solutions (pH approximate to 6,298.15 K) using measurements of diffusion coefficients, electrical conductivity, Raman and multinuclear NMR spectroscopy. With sucrose and glucose, indications of hydrolysis of the anion in the absence of the sugars came from a decrease in the diffusion coefficient with increasing concentration. Significant effects on the diffusion coefficients were observed in the presence of sucrose and glucose, suggesting interactions between the carbohydrates and vanadate ion. Support for this came from electrical conductivity measurements, where there were indications of formation of oligomeric species. These were found to depend on the carbohydrate used: confirmation of oligomer formation came from Raman spectroscopy, where it was possible to identify these species, and see their dependence on the particular carbohydrate used. Information on the interactions between the carbohydrates glucose or sucrose and vanadate came from V-51 and H-1 NMR spectroscopy, where the dominant species appeared to be a 2:2 complex with glucose, possessing trigonal bipyramidal centres, whereas with sucrose it is suggested that octahedral species are formed. Studies with fructose were complicated by competing oxidation of this carbohydrate and reduction of vanadium (V).
The interaction between the trivalent cations chromium(III), lanthanum(III) and gadolinium(III) and the anionic surfactant sodium dodecyl sulfate (SDS) has been studied in aqueous solutions using electrical conductivity. This data, together with previous results for aluminium(III) and SDS, are considered in terms of interaction of the metal ions and dodecyl sulfate at a critical aggregation concentration (cac) considerably below the surfactant cmc. The aggregates have a stoichiometry somewhat greater than that expected from simple charge neutralization, possibly due to formation of lamellar structures. Aggregates redissolve upon increasing SDS concentration, and at higher surfactant concentrations formation of surfactant micelles is observed. From detailed thermodynamic analysis of this process considerations are given on the major factors responsible for differences in behavior between the four trivalent cations.
8-Hydroxyquinoline (8-HQ), referred as to oxine in analytical chemistry, is a fluorogenic ligand. Its lack of fluorescence in water and alkanes, and its low quantum yield in many other organic solvents, are rationalized in the present study in terms of photoinduced formation of a nonfluorescent tautomeric form 8-HQ(T*). In water, intermolecular proton transfers with surrounding water molecules are expected, but intrinsic intramolecular proton transfer between the −OH and N functions cannot be ruled out because the presence of a weak internal H bond can be inferred from the ground-state properties of 8-HQ such as pKa values or solubility. In organic solvents, vapor pressure osmometry measurements in conjunction with infrared spectra allow us to show that (i) in alkane solvents, a very stable dimer is formed in the ground state (Kdim = 7 × 107 at 25 °C); biprotonic concerted proton transfers are then expected to occur within the dimer upon excitation, as was previously reported for 7-azaindole; (ii) in chlorinated solvents (CH2Cl2, CHCl3), hydration by residual water molecules likely leads to a nonnegligible fraction of hydrated open structures where excited-state proton transfer is impaired; a weak fluorescence can then be observed (ΦF ≈ 4 × 10-3).
Solution electrochemical studies have been conducted of the principle lumophores, dopants, and hole-transport agents of aluminum-quinolate(Alq3)-based organic light-emitting diodes (OLEDs) along with the characterization of their electrogenerated chemiluminescence (ECL). In acetonitrile/benzene solvent mixtures, Alq3 shows single one-electron reduction and oxidation processes, with a separation between the first oxidation and first reduction potentials, ΔEelectrochemical = 3.03 V, close to the estimates of energy difference between HOMO and LUMO levels obtained from absorbance spectra of thin films of Alq3, ΔEoptical = 3.17 eV. A new sulfonamide derivative of Alq3, (Al(qs)3), showed a positive shift (ca. 0.32 V) in the first reduction potential versus the parent molecule, and resolution of the overall reduction process into three successive, chemically reversible, one-electron reductions. Two successive one-electron oxidations are seen for 4,4‘-bis(m-tolyphenylamino)biphenyl (TPD), a hole-transporting material in many bilayer OLEDs, and for TPDF2, a fluorinated version of TPD, with TPDF2 oxidation occurring 0.1 V positive of that for TPD. Electrogenerated chemiluminescence reactions (Alq3-•/TPD+• (or TPDF2+•) and Al(qs)3-•/TPD+• (or TPDF2+•)) were found to produce emission spectra from Alq3*s or Al(qs)3*s states which were nearly identical to those seen from OLEDs based upon these molecules. Emission intensities increased with the increasing potential difference between the relevant redox couples. The diisoamyl derivative of quinacridone (DIQA), a quinacridone dopant for certain Alq3-based OLEDs, undergoes two successive one-electron reductions and two successive one-electron oxidations. The ECL reactions DIQA-•/DIQA+•, DIQA+•/Alq3-•, DIQA+•/Al(qs)3-•, DIQA-•/TPD+• and DIQA-•/TPDF2+• all produce the same singlet emissive state, DIQA*s, and the same emission spectral response seen in quinacridone and DIQA-doped OLEDs.
A number of metal complexes of 8-quinolinol (QOH) of general formula M(QO)n (n = 3, M = Al(III), Bi(III), Rh(III), Ir(III); n = 2, M = Pt(II), Pb(II)) have been synthesized and characterized. The heavy-metal complexes (M = Pt(II), Pb(II), Bi(III), Ir(III)) exhibit long-lived (τ ≃ 2-4 μs) phosphorescence and excited-state absorption (ESA) in fluid solution. The photophysics of these complexes (emission spectra and lifetimes, ESA spectra and lifetimes, emission quantum yields, efficiencies of formation of the long-lived state) has been studied in some detail. The long-lived emitting state is assigned as a metal-perturbed triplet state of the 8-quinolinol ligand. On the basis of their ground-state redox potentials and on their excited-state properties, the heavy-metal 8-quinolinol complexes are predicted to behave as powerful excited-state reductants (potentials in the -0.8 to -1.3 V range vs. SCE). Quenching studies verify these expectations.
The Automated force field Topology Builder (ATB, http://compbio.biosci.uq.edu.au/atb) is a Web-accessible server that can provide topologies and parameters for a wide range of molecules appropriate for use in molecular simulations, computational drug design, and X-ray refinement. The ATB has three primary functions: (1) to act as a repository for molecules that have been parametrized as part of the GROMOS family of force fields, (2) to act as a repository for pre-equilibrated systems for use as starting configurations in molecular dynamics simulations (solvent mixtures, lipid systems pre-equilibrated to adopt a specific phase, etc.), and (3) to generate force field descriptions of novel molecules compatible with the GROMOS family of force fields in a variety of formats (GROMOS, GROMACS, and CNS). Force field descriptions of novel molecules are derived using a multistep process in which results from quantum mechanical (QM) calculations are combined with a knowledge-based approach to ensure compatibility (as far as possible) with a specific parameter set of the GROMOS force field. The ATB has several unique features: (1) It requires that the user stipulate the protonation and tautomeric states of the molecule. (2) The symmetry of the molecule is analyzed to ensure that equivalent atoms are assigned identical parameters. (3) Charge groups are assigned automatically. (4) Where the assignment of a given parameter is ambiguous, a range of possible alternatives is provided. The ATB also provides several validation tools to assist the user to assess the degree to which the topology generated may be appropriate for a given task. In addition to detailing the steps involved in generating a force field topology compatible with a specific GROMOS parameter set (GROMOS 53A6), the challenges involved in the automatic generation of force field parameters for atomic simulations in general are discussed.
We have discovered a new type of small molecular host material based on aluminum(III) 8-hydroxyquinolates, Al(Saq)3, which was synthesized with three 5-(N-ethylanilinesulfonamide)-8- quinolinoline as bidentate ligands. By X-ray diffraction crystallographic analysis, the crystals of meridional Al(Saq)3 are monoclinic, space group P21/c, a = 17.952(3) Å, b = 17.716(3) Å, c = 17.080(3) Å, β = 99.895(4)°. Its peak photoluminescence in solid phase appears at 488 nm. Its LUMO/HOMO (−3.13/−6.04 eV) and optical band gap (Eg 2.91 eV) were determined by cyclic voltammetry . In solid thin film morphological investigation, it shows good thermal properties and high quantum efficiency. When doped with 0.7 wt % of the high fluorescent green dopant 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-benzo-[l]pyrano[6,7,8-ij]quinolizin-11-one (C-545T), energy transfer from Al(Saq)3 to dopant will occur and high green light emission can be achieved. For fabrication of OLEDs using spin-coating techniques, its electroluminescence is at 1931 CIEx,y (0.21, 0.41).
The diffusion behavior of the conjugated polyelectrolyte poly{[9,9-bis(6'-N,N,N-trimethylammonium)hexyl]fluorene-phenylene) bromide (HTMA-PFP) with different molecular weights has been studied in dimethyl sulfoxide (DMSO) + water solutions. Samples of HTMA-PFP with various molecular weights were obtained by synthesis of poly[9,9-bis(6'-bromohexyl)fluorene-phenylene] via a Suzuki coupling reaction, characterized by size exclusion chromatography (SEC), and quaternized with trimethylamine. Multicomponent chemical interdiffusion coefficients (mutual diffusion coefficients) were determined for solutions of HTMA-PFP and DMSO in water using the Taylor dispersion method. The results suggest specific interactions between the DMSO and the polymer. In addition, these systems were studied by pulse-field gradient nuclear magnetic resonance spectroscopy (PFG-NMR), and the corresponding self-diffusion coefficients were obtained. These were modeled using the Kirkwood-Riseman model, and a good fit to the observed behavior was obtained using literature data for molecular dimensions.
In this work, conditions of Suzuki condensation and polymer modification of polymers of benzene and fluorene units have been studied. A new polymer was prepared with statistical equimolecular amounts of two 2,7-dibromo-9,9-bis(6'-susbtituted-hexyl)fluorene as starting monomers. The C9 position of the poly [9,9-bis(6'-bromohexylfluoren-2,7-diyl)-alt-co-(benzen-1,4-diyl)] has been substituted yielding poly[9,9-bis(6'-cyanohexylfluoren-2,7-diyl)-alt-co-(benzen-1,4-diyl)] with a high degree of conversion. All polymers were completely soluble in THF and chloroform and were characterized by NMR, FTIR, and elemental analysis. Molecular weights measured by gel permeation chromatography coupled with light scattering detector results in polydispersity values between 3.3 and 1.2. Their glass transitions temperature were over 90 and 99 degrees C by DSC. Comparative studies of optical properties in solution and solid state show similar values indicating that the remote substitution of functional group maintains the spectroscopic characteristics of the backbone. Cyclic voltammetry studies and preliminary results in bias potentials of electroluminiscent devices reveal that these polymers may be promising candidates to be used as hole and electron transporting materials.
Blue luminescent hybrid materials (DDS–AQS(x%)/LDH) are successfully prepared by co-intercalating tris(8-hydroxyquinoline-5-sulfonate)aluminum anions (AQS3−) and dodecyl sulfonate (DDS−) with different molar ratios into Mg–Al layered double hydroxides (LDHs) by the hydrothermal and solution co-precipitation methods. A film of the material on a quartz substrate is obtained by the solvent evaporation method. The results show the blue luminescence is remarkably different from the pristine Na3AQS, which has cyan luminescence (ca. 450–470 nm vs. 495 nm). Furthermore, the hydrothermal product of DDS–AQS(66.67%)/LDH exhibits optimal luminous intensity and a significantly enhanced fluorescence lifetime. Nuclear magnetic resonance and Fourier-transform infrared spectroscopy indicate that the cyan–blue luminescence transition is due to the isomerization of meridianal to facial AQS via ligand flip caused by a host–guest electrostatic interaction, in combination with the dispersion and pre-intercalation effect of DDS. The hydrothermal conditions can promote a more ordered alignment of the intercalated fac-AQS compared with alignment in the solution state, and the rigid LDHs environment can confine the internal mobility of AQS to keep the facial configuration stable. This stability allows a facile preparation of large amounts of blue luminous powder/film, which is a new type of inorganic–organic hybrid photofunctional material.
Fabrication of high efficiency polymer based electrophosphorescent light emitting diodes (LED) was demonstrated. The luminous efficiency of 36 cd A -1 was obtained at 45 V. Results showed that light emitting devices could be fabricated by processing the luminescent layer from solution. High performance LEDs with low operating voltages were realized using Ir-complex with conjugated semiconducting polymers as host materials.
Using differential scanning calorimetry (DSC) measurements in combination with structural and optical characterization we have investigated the formation conditions of different phases of tris(8-hydroxyquinoline)aluminum (Alq3). We have identified the δ-phase as a high-temperature phase of Alq3 being composed of the facial stereoisomer, and report an efficient method to obtain blue luminescent Alq3 by a simple annealing process. This allows the preparation of large amounts of pure δ-Alq3 by choosing appropriate annealing conditions, which is necessary for further characterization of this blue-luminescent phase, and offers the possibility of fabricating blue organic light-emitting devices (OLEDs) from this material.
A study was conducted to demonstrate the synthesis and properties of an original group of liquid-crystalline Alq 3 derivatives, obtained by the ionic self-assembly process. The study demonstrated the synthesis of Alq 3 derivative, functionalized in the 5-position of the 8-hydroxyquinoline ligand by sulfonate groups. It was observed that the ionic self-assembly process allows to produce liquid-crystalline materials and highly luminescent thin-films from a charged Alq 3 core and oppositely charged surfactants. It was demonstrated that the morphology and molecular organization of these derivatives can be easily tuned from smectic to columnar matter, depending on the nature and the shape of the surfactant used.
Inkjet printing is considered to be a key technology in the field of defined polymer deposition. This article provides an introduction to inkjet printing technology and a short overview of the available instrumentation. Examples of polymer inkjet printing are given, including the manufacturing of multicolor polymer light-emitting diode displays, polymer electronics, three-dimensional printing, and oral dosage forms for controlled drug release. Special emphasis is placed upon the utilized polymers and conditions, such as polymer structure, molar mass, solvents, and concentration. Studies on viscoelastic fluid jets and the formation of viscoelastic droplets under gravity indicate that strain hardening is the key parameter that determines the inkjet printability of polymer solutions.
Singlet excitation energy harvesting and triplet emission in the self-assembled system poly{1,4-phenylene[9,9-bis(4-phenoxy-butylsulfonate)] fluorene-2,7-diyl} copolymer/tris(bipyridyl)ruthenium(II) in aqueous solution was studied. PBS-PFP was synthesized by condensation of 2,7-dibromo-9,9-bis(4- sulfonylbutoxyphenyl)fluorene and 1,4-phenylenediboronic acid, using Pd(PPh 3)4 as a catalyst. The steady-state fluorescence spectra were recorded using a Horiba-Jobin-Yvon-SPEX Fluorolog 3-22 instrument. The spectra were corrected for the wavelength response of the system. Time-resolved fluorescence decays were collected using the picosecond time-correlated single-photon counting technique. Results have shown that the anionic conjugated polyelectrolyte PBS-PFP and the cationic Ru(bpy)32+ self-assemble in aqueous solutions in the presence of the nonionic surfactant C12E5, and that efficient Förster energy transfer occurs from the CPE to the metal complex within 30 ps.
Precise conductance measurements on aqueous potassium chloride solutions at 0, 10, 18, and 25C have been made under various conditions over a concentration range 10–4<c<510–2 mole-dm–3, yielding the conductance equations
25° C:L = 149.873 - 95.01Öc + 38.48c log c + 183.1c - 176.4c3/2 18° C:L = 129.497 - 80.38Öc + 32.87c log c + 154.3c - 143.0c3/2 10° C:L = 107.359 - 64.98Öc + 27.07c log c + 125.4c - 110.3c3/2 0° C:L = 81.700 - 47.80Öc + 20.60c log c + 93.8c - 79.3c3/2 \begin{gathered} 25^\circ C:\Lambda = 149.873 - 95.01\sqrt c + 38.48c log c + 183.1c - 176.4c^{3/2} \hfill \\ 18^\circ C:\Lambda = 129.497 - 80.38\sqrt c + 32.87c log c + 154.3c - 143.0c^{3/2} \hfill \\ 10^\circ C:\Lambda = 107.359 - 64.98\sqrt c + 27.07c log c + 125.4c - 110.3c^{3/2} \hfill \\ 0^\circ C:\Lambda = 81.700 - 47.80\sqrt c + 20.60c log c + 93.8c - 79.3c^{3/2} \hfill \\ \end{gathered}
which are proposed for calibration of conductance cells.
GROMACS 3.0 is the latest release of a versatile and very well optimized package for molecular simulation. Much effort has been devoted to achieving extremely high performance on both workstations and parallel computers. The design includes an extraction of virial and periodic boundary conditions from the loops over pairwise interactions, and special software routines to enable rapid calculation of x–1/2. Inner loops are generated automatically in C or Fortran at compile time, with optimizations adapted to each architecture. Assembly loops using SSE and 3DNow! Multimedia instructions are provided for x86 processors, resulting in exceptional performance on inexpensive PC workstations. The interface is simple and easy to use (no scripting language), based on standard command line arguments with selfexplanatory functionality and integrated documentation. All binary files are independent of hardware endian and can be read by versions of GROMACS compiled using different floating-point precision. A large collection of flexible tools for trajectory analysis is included, with output in the form of finished Xmgr/Grace graphs. A basic trajectory viewer is included, and several external visualization tools can read the GROMACS trajectory format. Starting with version 3.0, GROMACS is available under the GNU General Public License from http://www.gromacs.org.