Browsing by Author "Chu, Hsuan-Chih"

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Novel Reversible Chemosensory Material Based on Conjugated Side-Chain Polymer Containing Fluorescent Pyridyl Receptor Pendants
(2011-07-21)
Chu, Hsuan-Chih
;
Lee, Yu-Hsien
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Hsu, Shou-Jen
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Yang, Po-Jen
;
Yabushita, Atsushi
A novel light-emitting monomer M1 and its side-chain polymer PI containing three conjugated aromatic pendants, including one pyridyl terminus, were successfully synthesized via Wittig and Pd-catalyzed Heck coupling reactions. The fluorescence of polymer P1 was efficiently quenched upon addition of different metal ions due to the facile energy transfers from the pendent groups of polymer PI to specific metal ions. Among these metal ions, PI exhibited extraordinary sensory selectivities for Ni(2+) and Cu(2+) ions over the other metal ions due to the stronger binding capabilities of Ni(2+) and Cu(2+) ions with polymer P1. From the time-resolved fluorescence (TRF) signals in photoluminescence spectra, the emergences of tau(1) decay components in polymer complexes (P1+Ni(2+)) and (P1-FCu(2+)) clearly indicated that their TRF traces consisted of two contributions, one from the complexes (tau(1)) and the other from free polymer P1 (tau(2)). Upon addition of Ni(2+) and Cu(2+) ions, polymer PI showed faster decay time constants (tau(1)) of metal ion quenching on TRF signals (i.e., better quenching efficiencies on photoluminescence) than its monomer M1. Furthermore, the on-off-on fluorescent switching behavior by adding a tridentate ligand 1,1,4,7,7-pentamethyl-diethylenetriamine (PMDTA) to the polymer complex (P1+Cu(2+)),for several successive cycles demonstrated a superior reusable chemosensor of P1 for further applications.
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
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Padhy, Harihara
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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.
Quenching effects of gold nanoparticles in nanocomposites formed in water-soluble conjugated polymer nanoreactors
(2012-02-17)
Yang, Po-Jen
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Chu, Hsuan-Chih
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Lee, Yu-Hsien
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Kobayashi, Takayoshi
;
Chen, Te-Cheng
In this paper we describe the first example of the in situ synthesis of gold nanoparticles (AuNPs) in the presence of a water-soluble conjugated polyfluorene (NPF) presenting pendent ammonium groups, with the polymer acting as an aqueous surfactant and providing fluorescent nanoreactors. Using this approach, we produced well-dispersed NPF-AuNP nanocomposites without the need for any additional reducing agents. The photoluminescence emission intensity of NPF-AuNP nanocomposite solution was quenched to a greater extent upon increasing the concentration of AuNPs, presumably through energy transfer or electron transfer from the fluorescent polymer to the metal nanoparticles. Through variations in the degrees of protonation and deprotonation of the amino groups of NPF at different values of pH, we found that the extent of quenching of AuNPs in NPF-AuNP nanocomposite solutions was directly related to the adsorption and desorption behavior of NPF on the metal surfaces. Transmission electron microscopy revealed that the greatest aggregation of AuNPs in the nanocomposite solution occurred at pH 3. suggesting that the ammonium groups (RNMe2 at pH 8.5; RNMe2H+ at pH 3) of the polymer side chains adsorbed onto the AuNP surfaces under these conditions. Distinct time-resolved fluorescence signals of the AuNP-quenched NPF polymers at different values of pH confirmed the interactions between these species. (C) 2012 Elsevier Ltd. All rights reserved.
Recoverable fluorescence chemosensors for Ni2+ ions based on hydrogen-bonded side-chain copolymers presenting pendent benzoic acid and pyridyl receptor units
(2012)
Yang, Po-Jen
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Chu, Hsuan-Chih
;
Chen, Te-Cheng
;
Lin, Hong-Cheu
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材料科學與工程學系
In this study we synthesized the novel fluorescent conjugated homopolymers P1 and P4 and the copolymers P2 and P3 containing proton-acceptor (pyridyl receptor) M1 monomer units and proton-donor (benzoic acid) M2 monomer units and investigated them as recoverable chemosensors for Ni2+ ions (based on adjusting the fluorescence energy transfer between the M1 and M2 moieties through varying the degree of hydrogen bonding). The levels of available (i.e., non-hydrogen-bonded) pyridyl receptors in the copolymers P2 and P3 were modified using different molar ratios of the pyridyl monomer M1 and the benzoic acid monomer M2. Significant chelation of the Ni2+ ions by the fluorescent homopolymers P1 and P4 and the copolymers P2 and P3 was evident by their distinct fluorescence quenching behaviors; the specific quenching constants (K-SV) decreased in the order P1 > P2 > P3 > P4, following the trend of the molar ratios of pyridyl receptors. When we added a third component, cyclodextrin (CD), to cap the benzoic acid moieties and, thereby, disrupt the hydrogen bonding between the M1 and M2 moieties in the copolymers P2 and P3, the levels of available pyridyl receptors in the recoverable chemosensor copolymers increased, resulting in relatively higher quenching constants for the P2 + CD, P3 + CD and blend (P1/P4) + CD systems. Fluorescence decay experiments revealed that the addition of CD also increased the fluorescence quenching efficiencies of the copolymers P2 and P3 towards Ni2+ ions. Such supramolecular (hydrogen-bonded) side-chain fluorescent copolymers might have practical applicability as recoverable and/or adjustable chemosensors.
Structural planarity and conjugation effects of novel symmetrical acceptor-donor-acceptor organic sensitizers on dye-sensitized solar cells
(2012-04-01)
Chu, Hsuan-Chih
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Sahu, Duryodhan
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Hsu, Ying-Chan
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Padhy, Harihara
;
Patra, Dhananjaya
In this study two series of novel symmetrical acceptor-donor-acceptor organic sensitizers containing 3,6- and 2,7-functionalized carbazole cores, respectively, connected to two anchoring cyanoacrylic acid termini via thienyl linkers were synthesized. The effect of the molecular planarity originating from the 3,6- and 2,7-functionalized carbazole cores on the performance of corresponding solar cells were investigated. Molecular orbital analyses revealed the characteristics of the carbazole-based highest occupied molecular orbitals and acid-based lowest unoccupied molecular orbitals. Time-dependent density functional theory calculations allowed us to assign the electronic transitions (>90%) of the low energy bands. Among these new dyes, the highest power conversion efficiency of 4.82% was obtained in a dye-sensitized solar cell device under standard AM 1.5 sunlight with an open-circuit voltage of 0.61 V, a short-circuit photocurrent density of 12.66 mA cm(-2) and a fill factor of 0.62. (C) 2011 Elsevier Ltd. All rights reserved.
Surface Modification of Gold Nanorods by Grafting Fluorene-Based Conjugated Copolymers Containing Thiol-Pendants
(1970-01-01)
Sahu, Duryodhan
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Chu, Hsuan-Chih
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Yang, Po-Jen
;
Lin, Hong-Cheu
;
材料科學與工程學系
"Two conjugated surfactants of monomer TF and polymer PTF with pendant thiol groups are synthesized for surface modifications of gold nanorods (GNRs). Cetyltrimethylammonium bromide (CTAB)-GNRs (without surface-modification) in aqueous solutions are prepared, and the original CTAB surfactant is replaced with TF and PTF due to their thiol-gold grafting reactions. Surface-modified TF-GNRs and PTF-GNRs in THF are obtained. UV-visible spectra provide the grafting evidence of TF and PTF. Compared with TF-GNRs, the PTF-GNRs show better solubility and stability against aggregations of nanorods in THF. TEM and XPS confirm the existence of binding bonds between the sulfur groups of PTF and the gold surface in PTF-GNRs. Compared with polymer surfactant (PTF), the faster PL emission decay in PTF-GNRs match well with the PL quenching of PTF-GNRs. Surface modifications are verified by UV-visible, TEM, XPS, PL and lifetime measurements."
Synthesis of Main-Chain Metallo-Copolymers Containing Donor and Acceptor Bis-Terpyridyl Ligands for Photovoltaic Applications
(2012-04-13)
Padhy, Harihara
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Ramesh, Mohan
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Patra, Dhananjaya
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Satapathy, Rudrakanta
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Pola, Murali Krishna
Two random (ZnII-based P1P2) and two alternating (RuII-based P3P4) metallo-copolymers containing bis-terpyridyl ligands with various central donor (i.e., fluorene or carbazole) and acceptor (i.e., benzothiadiazole) moieties were synthesized. The effects of electron donoracceptor interactions with metal (ZnII and RuII) ions on their thermal, optical, and electrochemical properties were investigated. Because of the strong ICT transitions between donor and acceptor ligands in both ZnII- and RuII-based metallo-coplymers and MLCT transitions in RuII-based metallo-coplymers, the absorption spectra covered a broad range of 260750 nm with the band gaps of 1.571.77 eV. In addition, the introduction of RuII-based metallo-coplymer P4 mixed with PC60BM as an active layer of the BHJ solar cell device exhibited the highest PCE value up to 0.90%.