Browsing by Author "Liang, Tzung-Chi"

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Photoluminescence quenching effects of surface-modified gold nanoparticles on side-chain polymers containing pyridyl H-acceptors with various lateral polarities
(2011-12-01)
Chu, Hsuan-Chih
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Liang, Tzung-Chi
;
Padhy, Harihara
;
Hsu, Shou-Jen
;
Lin, Hong-Cheu
In this study, we used photoluminescence (PL) quenching and transmission electron microscopy (TEM) to study the morphological behavior of hydrogen-bonded (H-bonded) supramolecular assemblies of luminescent H-acceptor polymers and H-donor gold nanoparticles (Au NPs). In fluorescence titration experiments, the lateral Me and MeO substituents on the fluorescent H-acceptor side-chain polymers PBOT1-PBOT3 and PBT1-PBT3 exhibited different electron-donating capabilities, thereby inducing different degrees of H-bonding and dipole-dipole interactions, as evidenced by effective fluorescence quenching upon the addition of surface-modified Au NPs bearing acid and acid-free surfactants (AuSCOOH and AuSC10, respectively). Among all of our tested nanocomposites, the highest Stern-Volmer quenching constant (K(sv)) was that obtained from the assembly of AuSCOOH with the homopolymer PBOT1. In addition, we developed fittable exponential equations to predict the values of Ksv of other fluorescent polymers (containing various molar ratios of pyridyl conjugated units) when titrated with these NP quenchers. The morphologies observed in the TEM images confirmed that fluorescence quenching resulted from the self-assembly of the supramolecular nanocomposites, mediated by H-bonds between the fluorescent H-acceptors of the polymers and the H-donors of the Au NPs presenting acid-modified surfactants. (C) 2011 Elsevier Ltd. All rights reserved.
Study of Supramolecular Side-Chain and Cross-Linking Polymers by Complexation of Various H-Donor Acids with H-Acceptor Copolymers Containing Pendent Carbazole and Fluorescent Pyridyl Units
(2009-06-01)
Liang, Tzung-Chi
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Lin, Hong-Cheu
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材料科學與工程學系
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Department of Materials Science and Engineering
Two H-bonded acceptor (H-acceptor) homopolymers 14 and 17 were successfully prepared by polymerization of fluorescent pyridyl monomers PBT and PBOT (12 and 13), which were synthesized via Sonogashira coupling and Wittig-Horner reactions. To increase the glass transition temperatures as well as reduce the pi-pi stacking of the photoluminescent (PL) H-acceptor copolymers and their H-bonded polymer complexes, fluorescent monomers 12 and 13 were copolymerized with N-vinylearbazole monomer CAZ (23) to produce H-acceptor copolymers 15-16 and 18-19. Supramolecular side-chain and crosslinking polymers (i.e., H-bonded polymer complexes) obtained by complexation of light-emitting H-acceptor polymers 14-19 with various proton donor (H-donor) acids 20-22 were further characterized by DSC, POM, FTIR, XRD, and PL measurements. The mesomorphic properties can be tuned from the nematic phase in H-acceptor homopolymers (14 and 17) to the tilted smectic C phase in their H-bonded polymer complexes (14/20-21 and 17/20-22) by the introduction of H-donor acids (20-22). Moreover, the PL properties of light-emitting H-acceptor polymers can be adjusted not only by the central structures of the conjugated pyridyl cores but also by their surrounding nonfluorescent H-donor acids. In general, redder shifts of PL emissions in H-bonded polymer complexes occurred when the light-emitting H-acceptor polymers were complexed with H-donors having smaller pKa values. (c) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2734-2753, 2009
Supramolecular assembly of H-bonded copolymers/complexes/nanocomposites and fluorescence quenching effects of surface-modified gold nanoparticles on fluorescent copolymers containing pyridyl H-acceptors and acid H-donors
(2009)
Liang, Tzung-Chi
;
Lin, Hong-Cheu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A series of photoluminescent (PL) and liquid crystalline (LC) self-H-bonded side-chain copolymers (P1-P3) consisting of pyridyl H-acceptors and isomeric acid H-donors (i.e., para-, meta-, and orthobenzoic acids) were synthesized. Supramolecular H-bonded complexes were also obtained by mixing the photoluminescent H-acceptor homopolymer PBT1 (containing pyridyl pendants) with isomeric H-donor homopolymers P7-P9. The formation of H-bonds was confirmed by FTIR, DSC, and XRD measurements. Moreover, PL and LC properties of the H-bonded copolymers and complexes were affected not only by the H-bonding effect of the supramolecular structures but also by the acid-substituted positions of isomeric H-donors. In combination with different functionalized gold nanoparticles (which bear acid or acid-free surfactants), the emission intensities of nanocomposites containing self-H-bonded copolymer P1 (bearing both H-acceptor and H-donor moieties) and non-self-H-bonded copolymer P4 (bearing acid-protected moieties), were quenched to different extents by varying the concentration of gold nanoparticles. The copolymeric H-acceptors and surface-modified gold nanoparticles demonstrated diverse morphological and PL quenching effects on the supramolecular architectures of the nanocomposites, which result from competition between the H-donors from the acid pendants on copolymers and the acid surfactants on the gold nanoparticles.
Supramolecular Assembly of H-Bonded Side-Chain Polymers Containing Conjugated Pyridyl H-Acceptor Pendants and Various Low-Band-Gap H-Donor Dyes Bearing Cyanoacrylic Acid Groups for Organic Solar Cell Applications
(2009-11-15)
Liang, Tzung-Chi
;
Chiang, I-Hung
;
Yang, Po-Jen
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Kekuda, Dhananjay
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Chu, Chih-Wei
Novel supramolecular side-chain polymers were constructed by complexation of proton acceptor (H-acceptor) polymers, i.e., side-chain conjugated polymers P1-P2 containing pyridyl pendants, with low-band-gap proton donor (H-donor) dyes S1-S4 (bearing terminal cyanoacrylic acids) in a proper molar ratio. Besides unique mesomorphic properties confirmed by DSC and XPD results, the H-bonds of supramolecular side-chain structures formed by pyridyl H-acceptors and cyanoacrylic acid H-donors were also confirmed by FTIR measurements. H-donor dyes S1-S4 in solid films exhibited broad absorption peaks located in the range of 471-490 nm with optical band-gaps of 1.99-2.14 eV. Furthermore, H-bonded polymer complexes P1/S1-P1/S4 and P2/S1-P2/S4 exhibited broad absorption peaks in the range of 440-462 nm with optical band-gaps of 2.11-2.25 eV. Under 100 mW/cm(2) of AM 1.5 white-light illumination, the bulk heterojunction polymer solar cell (PSC) devices containing an active layer of H-bonded polymer complexes P1/S1-P1/S4 and P2/S1-P2/S4 (as electron donors) mixed with [6,6]-phenyl C(61) butyric acid methyl ester (i.e., PCBM, as an electron acceptor) in the weight ratio of 1:1 were investigated. The PSC device containing H-bonded polymer complex P1/S3 mixed with PCBM (1:1 w/w) gave the best preliminary result with an overall power conversion efficiency (PCE) of 0.50%, a short-circuit current of 3.17 mA/cm(2), an open-circuit voltage of 0.47 V, and a fill factor of 34%. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5998-6013, 2009