Browsing by Subject "Fluorine"

Now showing 1 - 5 of 5

Open Access
A complementary electrochromic device with highly improved performance based on brick-like hydrated tungsten trioxide film
(American Scientific Publishers, 2012) Jiao, Z.; Wang, J.; Ke, L.; Sun, X. W.; Demir, Hilmi Volkan
Uniform and well adhesive nanostructured hydrated tungsten trioxide (3WO 3•H 2O) films were grown on fluorine doped tin oxide (FTO) substrate via a facile and template-free crystal-seed-assisted hydrothermal method by addition of ammonium sulfate ((NH 4) 2SO 4) and hydrogen peroxide (H 2O 2). X-ray diffraction (XRD) studies indicated that the films are of orthorhombic structure. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) analysis showed that the film was composed of brick-like nanostructures with a preferred growing direction along (002). The influence of seed layer, (NH 4) 2SO 4 and H 2O 2 on the products were also studied. The film showed good cyclic stability, comparable switching speed and coloration efficiency (30.1 cm 2 C -1). A complementary electrochromic device based on the film and Prussian blue depicted highly improved color contrast, coloration/bleaching response (1.8 and 3.7 s respectively) and coloration efficiency (164.6 cm 2 C -1).
Open Access
The effect of cucurbit[n]uril on the solubility, morphology, and the photophysical properties of nonionic conjugated polymers in an aqueous medium
(2010) Tuncel, D.; Artar, M.; Hanay, S. B.
The effects of cucurbit[n]uril on the dissolution and the photophysical properties of nonionic conjugated polymers in water are described. For this purpose, a fluorine-based polymer, namely, poly[9,9-bis{6(N,N-dimethylamino) hexyl}fluorene-co-2,5-thienylene (PFT) was synthesized and characterized by spectroscopic techniques including 1D and 2D NMR, UV-vis, fluorescent spectroscopy, and matrix-assisted laser desorption mass spectrometry (MALDI-MS). For the first time, it was demonstrated that a nonionic conjugated polymer can be made soluble in water through an inclusion complex formation with CB8. The structure of the complex was elucidated by NMR experiments including 1H and selective 1D-NOESY. This complex emits green and is highly fluorescent with fluorescent quantum yield of 35%. In contrast, CB6 or water-soluble CB7 although they are chemically identical to CB8 do not have any effect on the dissolution and photophysical properties of PFT. By preparing a protonated version of PFT, the optical properties of PFT in methanol, protonated PFT and PFT@CB8 in water have been studied and compared. It was also observed that the morphology of the polymer PFT was affected by the presence of CB8. Thus CB8-assisted self-assembly of polymer chains leads to vesicles formation; these structures were characterized by DLS, AFM, SEM, and TEM fluorescent optical microscopy.
Open Access
Effects of perfluorination on thiophene and pyrrole oligomers
(2010) Salzner, U.
The effect of perfluorination on thiophene and pyrrole oligomers in neutral, cationic, and anionic states was investigated with density functional theory at the (TD)B3P86-30%/6-31G* level. For the title compounds fluorination leads to planarization. For pyrroles a band gap reduction of 0.58 eV results, as unsubstituted pyrroles are nonplanar and disordered in the solid state. For thiophene the band gap is slightly increased as long thiophene oligomers are almost planar. Ionization energies and electron affinities increase upon fluorination by 0.65 and 0.60 eV for polythiophene and by 0.45 and 0.90 eV for polypyrrole. Conduction band widths increase by 0.5 for polythiophene and by 0.7 eV for polypyrrole. Spectra of charged (doped) forms are almost identical to those of the parent systems. Like parent systems, fluorinated oligomers with chain lengths of more than six rings develop a third UV absorption that increases in strength and decreases in energy upon chain length increase.
Open Access
A photoelectron spectroscopic investigation of conducting polypyrolle-polyamide composite film
(Elsevier, 1995-04) Süzer, Şefik; Toppare, L.; Allen, G. C.; Hallam, K. R.
X-ray photoelectron spectrum of the electrochemically prepared polypyrrole and polypyrrole-polyamide composite films exhibit an additional strong high binding energy peak at 402.0 eV corresponding to N+ moieties. Intensity of this peak is significantly reduced upon electrochemical reduction. Atomic concentrations derived from the observed N+ and F (stemming from the dopant BF4-) peaks reveal a slightly higher cation/anion ratio for this composite and suggest that the composite has a different chemical composition than the corresponding polymers. © 1995 Elsevier Science B.V.
Open Access
Theoretical analysis of poly(difluoroacetylene) PDFA
(Elsevier, 2003) Salzner, U.
Due to the π-donating ability of fluorine, fluorosubstitution has a remarkable effect on the band structure of polyacetylene (PA). Valence and conduction band edges decrease in energy, leading to narrower valence and wider conduction bands. Ionization potential and electron affinity of PDFA are predicted to be about 1.5 eV higher than those of PA. This indicates that PDFA is an excellent candidate for an n-type conductor. PDFA tends to adopt non-planar structures but the energy of planarization is only 5.44 kcal/mol. Alternating difluoroethylene and ethylene units yield planar polymers with decreased band gaps. Ionization potential and electron affinity of the mixed polymer are between those of the homopolymers. © 2003 Elsevier Science B.V. All rights reserved.