Browsing by Author "Hsu, Shou-Jen"

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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
;
Hsu, Shou-Jen
;
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
;
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.