Browsing by Subject "conjugated polymers"

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A Dual-Fluorescent Composite of Graphene Oxide and Poly(3-Hexylthiophene) Enables the Ratiometric Detection of Amines
(2014-04) Meng, Dongli; Yang, Sshaojun; Sun, Dianming; Zeng, Yi; Sun, Jinhua; Li, Yi; Yan, Shouke; Huang, Yong; Bielawski, Christopher W.; Geng, Jianxin; Bielawski, Christopher W.
A composite prepared by grafting a conjugated polymer, poly(3-hexylthiophene) (P3HT), to the surface of graphene oxide was shown to result in a dual-fluorescent material with tunable photoluminescent properties. Capitalizing on these unique features, a new class of graphene-based sensors that enables the ratiometric fluorescence detection of amine-based pollutants was developed. Moreover, through a detailed spectroscopic study, the origin of the optical properties of the aforementioned composite was studied and was found to be due to electronic decoupling of the conjugated polymer from the GO. The methodology described herein effectively overcomes a long-standing challenge that has prevented graphene based composites from finding utility in sensing and related applications.
Electrochemistry and Electrogenerated Chemiluminescence of Thiophene and Fluorene Oligomers. Benzoyl Peroxide as a Coreactant for Oligomerization of Thiophene Dimers
(2012-05) Nepomnyashchii, Alexander B.; Ono, Robert J.; Lyons, Dani M.; Bielawski, Christopher W.; Sessler, Jonathan L.; Bard, Allen J.; Nepomnyashchii, Alexander B.; Ono, Robert J.; Lyons, Dani M.; Bielawski, Christopher W.; Sessler, Jonathan L.; Bard, Allen J.
The electrochemical properties of oligomers of thiophene (with number of monomer units, n, from 2 to 12) and fluorene (n = 3 to 7) were investigated. Both sets of oligomers were characterized by the presence of two oxidation and two reduction waves as determined by cyclic voltammetry (CV), with the reversibility of the waves depending on the structural properties of the compounds. The addition or removal of a third electron was found to be difficult relative to the second, a finding shown for conjugated oligomers with chain lengths up to 7 in the case of the fluorenes and up to 12 for the thiophenes. The oligothiophenes showed a larger separation between the electrochemical waves for the same chain length, and also substantial electrogenerated chemiluminescence (ECL) signals, whose intensity increased with oligomer size. In contrast, the ECL intensity of the fluorene oligomers was essentially independent of chain length. The ECL spectra for the thiophene dodecamer were obtained with concentrations as low as 20 pM, a result that reflects a high ECL efficiency, close to that of the well-known ECL standard Ru(bpy)(3)(2+). Oligomers were also formed on electrochemical reduction of an appropriately functionalized dimer in the presence of benzoyl peroxide producing a longer wavelength emission (maximum at similar to 540 nm) as opposed to the spectrum of the dimer (lambda(em) = 390 nm).
Thermodynamic Synthesis of Solution Processable Ladder Polymers
(2015-11) Lee, Jongbok; Rajeeva, Bharath Bangalore; Yuan, Tianyu Y.; Guo, Zi-Hao; Lin, Yen-Hao; Al-Hashimi, Mohammed; Zheng, Yuebing; Fang, Lei; Zheng, Yuebing; Zheng, Yuebing
The synthesis of a carbazole-derived, well-defined ladder polymer was achieved under thermodynamic control by employing reversible ring-closing olefin metathesis. This unique approach featured mild conditions and excellent efficiency, affording the ladder polymer backbone with minimum levels of unreacted defects. Rigorous NMR analysis on a C-13 isotope-enriched product revealed that the main-chain contained less than 1% of unreacted precursory vinyl groups. The rigid conformation of the ladder-type backbone was confirmed by photophysical analysis, while the extended rod-like structure was visualized under scanning tunneling microscope. Excellent solubility of this polymer in common organic solvents allowed for feasible processing of thin films using solution-casting techniques. Atomic force microscopy and grazing incident X-ray scattering revealed a uniform and amorphous morphology of these films, in sharp contrast to the polycrystalline thin films of its small molecular counterpart.