Browsing by Author "Guo, Song"

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Effects on Oxidation Waves of Conjugated Polymers by Studying Photoluminescence Quenching and Electrogenerated Chemiluminescence
(2011-05-26)
Chen, Jiun-Tai
;
Chang, Ya-Lan
;
Fabian, Omar
;
Guo, Song
;
Lackowski, William M.
We study the electrochemical oxidation waves of conjugated polymers by examining photoluminescence (PL) quenching and electrogenerated chemiluminescence (ECL) of poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT). Different factors such as the anion concentration, the anion size, the electrochemical potential, and the coreactant concentration are investigated for their effects on the behavior of the oxidation waves. Our results show that the wave speeds of PL quenching or ECL can be increased by increasing the anion concentration, decreasing the anion size, or increasing the electrochemical potentials. In addition, the intensity of ECL can be controlled by the coreactant concentration. The transition from pinned to free ECL waves is also studied when an intermediate coreactant concentration is used. These results provide useful insights for understanding the electrochemical oxidation wave phenomenon.
Electrogenerated Chemiluminescence of Conjugated Polymer Films from Patterned Electrodes
(2011-08-10)
Guo, Song
;
Fabian, Omar
;
Chang, Ya-Lan
;
Chen, Jiun-Tai
;
Lackowski, William M.
A new phenomenon is presented in which electrogenerated chemiluminescence (ECL) is generated and propagates laterally as self-reinforcing waves as a result of the oxidation of a poly(9,9-dioctylfluorene-co-benzothiadiazole) thin film. In an ordered array of Au electrode posts that act as effective ECL nucleation sites, soliton-like waves were observed to expand from each site and annihilate upon collision with each other. Simulations of the ECL response supported the experimental observations that the ECL waves propagate at a constant speed. A correlated diffusion mechanism involving the correlated motion of ions, injected holes, and solvent molecules is proposed to interpret the experimental data qualitatively. A rapid increase in the diffusion coefficient of these species in the polymer results in a sharp interface between non-oxidized and oxidized polymer phases wherein the electrochemical (EC) oxidation and mass transport of all pertinent species take place. EC oxidation of conjugated polymers of this type has important implications for the understanding of these materials and their modes of operation in EC conjugated polymer devices.
Electrogenerated Chemiluminescence of Pure Polymer Films and Polymer Blends
(2011-04-04)
Chen, Jiun-Tai
;
Chang, Ya-Lan
;
Guo, Song
;
Fabian, Omar
;
Lackowski, William M.
We recently reported the discovery of soliton-like electrogenerated chemiluminescence (ECL) waves from pure conjugated polymer films and gold-nanoparticles-doped polymer films. In addition to a more detailed study of these polymer systems by changing the film thickness and the distribution of local leaks, we also apply the ECL wave phenomenon to polymer blends of conjugated and nonconjugated polymers. Poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT) is used as the active material that is oxidized and produces ECL with the presence of a co-reactant, tri-n-propylamine (TPA). Several factors such as film thickness, artificial leaks, and solubility of doped polymers are examined for their effects on the ECL behavior. When polystyrene (PS), less soluble in the electrolyte, is blended with F8BT, dotted ECL signals are observed and transported as waves. When poly(methyl methacrylate) (PMMA), more soluble in the electrolyte, is blended with F8BT, PMMA serves as local scratches and ECL waves are triggered simultaneously from the whole film.