Browsing by Author "Whang, Wha-Tzong"

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A facile dedoping approach for effectively tuning thermoelectricity and acidity of PEDOT:PSS films
(2014-03-01)
Tsai, Tsung-Che
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Chang, Hsiu-Cheng
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Chen, Chun-Hua
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Huang, Yi-Chia
;
Whang, Wha-Tzong
A facile approach namely controlling the pH level of 5 wt% dimethyl sulfoxide (DMSO) doped poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) solution with sodium hydroxide (NaOH) was utilized for the first time in successfully optimizing the thermoelectric conversion efficiency of PEDOT:PSS films. The largely varied Seebeck coefficients and electrical conductivities of the pH controlled PEDOT:PSS films which could thus construct a beneficial curve for locating the optimized power factor are clearly shown from the significant changes of the carrier concentration via the dedoping of PEDOT. The correlation between pH value and carrier concentration as well as the power factor is experimentally found with numerical description covering a full pH range. The applied technique and the resulting optimized thermoelectric properties and possible bio-compatibility not only provide a fundamental understanding of the thermoelectric conducting polymers but widely disclose a variety of potential applications in the future. (C) 2014 Elsevier B. V. All rights reserved.
A Facile Surface Treatment Utilizing Binary Mixtures of Ammonium Salts and Polar Solvents for Multiply Enhancing Thermoelectric PEDOT: PSS Films
(2014-12-01)
Tsai, Tsung-Che
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Chen, Tsung-Han
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Chang, Hsiu-Cheng
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Chen, Chun-Hua
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Huang, Yi-Chia
Addressable Cell Microarrays via Switchable Superhydrophobic Surfaces
(2010)
Shiu, Jau-Ye
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Kuo, Chiung Wen
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Whang, Wha-Tzong
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Chen, Peilin
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材料科學與工程學系
Here we describe an approach to fabricate addressable cell microarrays, which are based on the patterned switchable superhydrophobic surfaces. The switchable superhydrophobic surfaces were prepared by roughening the surfaces of fluoropolymers on the electrodes. Upon the application of 150 V to the underneath electrodes, the water contact angle on the roughened fluoropolymer surfaces could be decreased from 163 degrees to less than 10 degrees allowing the deposition of fibronectin, which could guide the growth of the cells. Our result indicated that it was possible to control the spatial distribution of two different cells on the cell microarrays. (C) Koninklijke Brill NV, Leiden, 2010
All-solution-processed inverted polymer solar cells on granular surface-nickelized polyimide
(2009-07-01)
Hsiao, Yu-Sheng
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Chen, Chih-Ping
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Chao, Ching-Hsun
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Whang, Wha-Tzong
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材料科學與工程學系
In this study, we prepared all-solution-processed inverted polymer solar cells (PSCs) incorporating two solution-processed electrodes-surface-nickelized polyimide films (NiPI films) as cathodes and high-conductivity poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) films as anodes-and an active layer with a bulk heterojunction morphology of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C(61)-buytyric acid methyl ester (PCBM). The granular Ni thin films, which exhibited good adhesion and high-conductivity (ca. 2778 S cm(-1)) on the polyimide (PI) substrates and possessed a work function different from that of pure Ni metal (WF, 5.4 eV). Using ultraviolet photoelectron spectroscopy, we determined that the WF of the NiPI films was ca. 3.9 eV. Prior to the coating of the photoactive layer, the surface of the NiPI films were treated with titanium(diisopropoxide)bis(2,4-pentanedionate) (TIPD) solution to facilitate the deposition of high-quality active layer and further as a hole blocking layer. The solution processed anodes (solvent-modified PEDOT:PSS films) were further coated and subjected to mild oxygen plasma treatment on the active layer. Short exposure (5 s) to the plasma improved the quality of the surface of the active layer for PEDOT:PSS deposition. These inverted PSCs on flexible granular NiPI films provided a power conversion efficiency of 2.4% when illuminated under AM 1.5 conditions (100 mW cm(-2)). The phenomenon of light absorption enhancement in those inverted PSCs was observed as indicated in reflective UV-vis, haze factor and external quantum efficiency (EQE) responses. The resulting fill factor (FF) of 0.43 is still significantly lower than the FF of 0.64 for standard devices. When compared to the planar structure, the improvement of absorbance of light and good haze factors was obtained for granular structure which suggests NiPI as a better back contact electrode through enhancing the light trapping and scattering in inverted PSCs. (C) 2009 Elsevier B.V. All rights reserved.
An in situ fabrication process for highly electrical conductive polyimide/MWCNT composite films using 2,6-diaminoanthraquinone
(2013-10-18)
Huang, Yi-Chia
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Lin, June-Hua
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Tseng, I-Hsiang
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Lo, An-Ya
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Lo, Teng-Yuan
We present a valuable in situ fabrication process for synthesizing high electrical conductive polyimide/multiwalled carbon nanotube (PI/MWCNT) composite films. The success of this process was achieved the addition of 2,6-diaminoanthraquinone (DAAQ). The DAAQ is not only an excellent dispersion agent to stably disperse pristine MWCNTs in solvent but also a monomer to directly synthesize PI. The strong interaction between DAAQ with MWCNT was verified by FTIR, UV-Vis, Raman, and fluorescence spectra. The highest value of electrical conductivity of 55.6 S/cm are achieved by the PI composite containing 40 wt.% of MWCNT. Moreover, the electrical conductivity of this film further enhanced to 106 S/cm after the thermal compression process. The MWCNT content at the percolation threshold of conductivity is 0.50 wt.% (or 0.32 vol.%) and the critical exponent is equal to 2.52. The developed in situ fabrication process through DAAQ-derived molecules can also be applied to synthesize other polymers requiring diamine structure. (C) 2013 Published by Elsevier Ltd.
Anti-corrosion characteristics of polyimide/h-boron nitride composite films with different polymer configurations
(2014-12-15)
Huang, Yi-Chia
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Lo, Teng-Yuan
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Chao, Cheun-Guang
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Whang, Wha-Tzong
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材料科學與工程學系
Anti-corrosive polyimide/hexagonal boron nitride (PI/h-EN) composite films were prepared with different monomers to offer different polymer configurations: rigid and soft. In PI/h-BN composite films, different configurations of polymers show different crystallinity trends of the polymer matrix. In our study, the degree of crystallinity in rigid polymer decreases with the EN content; in flexible polymers it is independent of the BN content. It is worth noting that BN in different PI matrices can effectively enhance the protection of steel from corrosion. With a flexible PI matrix, the PI/h-BN coating exhibited better resistance to water vapor and better anti-corrosion. Only 5 wt.% of h-BN in the composite is enough to offer high anti-corrosion, a positive corrosion voltage. (C) 2014 Elsevier B.V. All rights reserved.
Behavior of single DNA molecules in the well-ordered nanopores
(2008-10-03)
Shiu, Jau-Ye
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Whang, Wha-Tzong
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Chen, Peilin
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材料科學與工程學系
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Department of Materials Science and Engineering
Here we describe a simple approach to fabricate robust three-dimensional periodic porous nanostructure inside the microchannels. In this approach, the colloidal crystals were first grown inside the microchannel using an evaporation-assisted self-assembly process. Then the void spaces among the colloidal crystals were filled with epoxy-based negative tone photoresist. After subsequent development and nanoparticle removal, the well-ordered nanoporous structures inside the microchannel could be fabricated. Depending on the size of the colloidal nanoparticles, periodic porous nanostructures inside the microchannels with cavity size of 330 and 570 nm have been obtained. The dimensions of interconnecting pores for these cavities were around 40 and 64 nm, respectively. The behavior of single X-phage DNA molecules in these nanoporous structures was studied using fluorescence microscopy. It was found that the length of DNA molecules oscillated in the nanoporous structures. The measured length for A-phage DNA was larger in the 330 nm cavity than those measured in the 570 nm cavity. (C) 2008 Elsevier B.V. All rights reserved.
Catalyst-free, low-temperature growth of high-surface area carbon nanoflakes on carbon cloth
(2009-01-01)
Hung, Tsung-Chi
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Chen, Chia-Fu
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Chen, Chien-Chung
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Whang, Wha-Tzong
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材料科學與工程學系
We have used a microwave plasma-enhanced chemical vapor deposition system to synthesize two-dimensional (2D) and three-dimensional (3D) structures of carbon nanoflakes (CNFs). This catalyst-free, low-temperature synthesis involved introducing CO(2) and CH(4) as reactants at a specified ratio of 2:3. We obtained uniform 2D arrays of CNFs at lower microwave powers (200 or 300 W) and substrate temperatures (up to 420 degrees C); their thickness was close to 1 mm. At a microwave power of 400 W, we obtained a 3D architecture comprising the smallest nanoflakes reported to date. The specific surface area of the 3D structure was double that of the corresponding 2D arrays. We suspect that such structured carbon materials might have great potential for energy storage applications. (C) 2008 Elsevier B. V. All rights reserved.
Chemical formation of palladium-free surface-nickelized polyimide film for flexible electronics
(2008-04-30)
Hsiao, Yu-Sheng
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Whang, Wha-Tzong
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Wu, Sheng-Chang
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Chuang, Kuen-Ru
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材料科學與工程學系
Flexible polyimide (PI) films for flexible electronics were surface-nickelized using a fully solution-based process and excellent adhesion between the nickel and polyimide phases was observed. Polyimide substrates were modified by alkaline hydrolysis, ion exchange, reduction and nickel electroless deposition without palladium. Atomic force microscopy and field emission scanning electron microscopy were used to follow the growth of nickel nanoparticles (Ni-NPs) and nickel layers on the polyimide surface. The surface resistances of the Ni-NPs/PI films and Ni/PI films, measured using a four-point probe, were 1.6x10(7) and 0.83 Omega/cm(2), respectively. The thicknesses of Ni-NPs and the Ni layer on the polyimide surface were 82 nm and 382 nm, respectively, as determined by transmission electron microscopy, and the Ni layer adhered well to PI, as determined by the adhesive tape testing method. (c) 2008 Elsevier B.V. All rights reserved.
Co-doping with polysquaraine enhances the holographic optical data storage of PMMA/PQ photopolymers
(2011)
Ko, Cheng-Jung
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Chang, Yeh-Lu
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Hsiao, Yi-Nan
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Chen, Po-Lin
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Lin, Shiuan-Huei
In this study, we synthesised poly(3-octylpyrrole-co-squaric acid) (PSQ3), a polysquaraine, through the reaction of 3-octylpyrrole and squaric acid, and then co-doped it with phenanthrenequinone (PQ) into poly(methyl methacrylate) (PMMA) to improve the holographic data storage characteristics of the photopolymer. The photopolymers co-doped with relatively small amounts of PSQ3 exhibited greatly improved holographic recording characteristics, including superior diffraction efficiency and dynamic range (M#). Among the samples co-doped with PQ and PSQ3, the maximum diffraction efficiency reached 54.8% (cf. 9.0% for PMMA/PQ) without further downgrade and the value of M# reached 1.05 (cf. 0.46 for PMMA/PQ). Therefore, the holographic data storage characteristics of the photopolymer PMMA/PQ were improved through co-doping with PSQ3.
Controlling vertical alignment of phthalocyanine nanofibers on transparent graphene-coated ITO electrodes for organic field emitters
(2012)
Huang, Kuo-Jung
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Hsiao, Yu-Sheng
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Huang, Jen-Hsien
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Chu, Chih-Wei
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Chen, Peilin
In this study, we developed a simple and efficient approach-using graphene coatings on ITO as transparent electrodes-for inducing the growth of 29H,31H-phthalocyanine (H2Pc) nanofiber arrays through a thermal evaporation process, with potential use in organic field emitters (FEs). By controlling the surface energy and temperature of the electrodes during evaporation, H2Pc molecules readily self-assemble, forming an out-of-plane morphology on reduced graphene oxide surfaces (rGO; surface energy: ca. 50 mJ m(-2)). The devices fabricated on rGO/indium tin oxide (FE-rGO) exhibited not only excellent FE performance but also outstanding anti-degradation capability during stability tests. This facile approach toward rGO coatings opens a new avenue for the transformation of small organic molecule films into vertically standing nanostructures on transparent electrodes, with various organic electronics applications.
Copolymer and platinum ion assisted growth of functionalized gold nanonests
(2015-01-01)
Yang, Jing-Cyuan
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Chang, Yi-Hsiang
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Whang, Wha-Tzong
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Chen, Chun-Hua
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Wu, Ren-Jye
This paper describes a facile low-toxicity synthesis of two different types of Au nanonests and one binary Au-Pt core-shell nanonest with high yield and excellent uniformity in size and morphology using block copolymer P123 (EO20PO70EO20) as a soft template and the main reductant in an ice water bath. The introduction of a suitable second metallic source, i.e. Pt ions in the present case, was proven to be a unique strategy for effectively governing the reduction sites of P123 for Au nucleation, which leads to significant changes especially in the crystallite size of the grown Au nanonests. The Au nanonests exhibited a distinct morphology-dependent surface plasmon resonance (SPR) that is red-shifted by similar to 140 nm from the spherical particles wavelength, and significant surface-enhanced Raman scattering (SERS), allowing the rapid determination of rare malachite green oxalate (MGO).
Deposition of Carbon Nanowall Flowers on Two-Dimensional Sheet for Electrochemical Capacitor Application
(2009)
Hung, Tsung-Chi
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Chen, Chia-Fu
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Whang, Wha-Tzong
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材料科學與工程學系
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Department of Materials Science and Engineering
We have used bias-assisted microwave plasma chemical vapor deposition to synthesize (i) two-dimensional carbon nanowalls [(2D CNWs), monolayer] and (ii) three-dimensional carbon nanowalls [(3D CNWs), double-layer] on carbon cloth in a CH(4)/CO(2) system. The specific surface area of the 3D CNW electrode (1580 m(2)/g) was considerably larger than that of the 2D CNW electrode (364 m(2)/g). This higher surface area and more porous structure of the 3D CNW electrode resulted in its capacitance reaching as high as ca. 198 F/g at a scan rate of 10 mV/s. Electrochemical measurements suggested that this 3D electrode is a promising material for application in electrical storage devices.
Dibenzothiophene/oxide and quinoxaline/pyrazine derivatives serving as electron-transport materials
(2006-07-21)
Huang, Tai-Hsiang
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Whang, Wha-Tzong
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Shen, Jiun Yi
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Wen, Yuh-Sheng
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Lin, Jiann T.
A series of 2,8-disubstituted dibenzothiophene and 2,8-disubstituted dibenzothiophene-SS-dioxide derivatives containing quinoxaline and pyrazine moieties are synthesized via three key steps: i) palladium-catalyzed Sonogashira coupling reaction to form dialkynes; ii) conversion of the dialkynes to diones; and iii) condensation of the diones with diamines. Single-crystal characterization of 2,8-di(6,7-dimethyl-3-phenyl-2-quinoxalinyl)-5H-5 lambda(6)-dibenzo[b,d]thiophene-5,5-dione indicates a triclinic crystal structure with space group P1 and a non-coplanar structure. These new materials are amorphous, with glass-transition temperatures ranging from 132 to 194 degrees C. The compounds (Cpd) exhibit high electron mobilities and serve as effective electron-transport materials for organic light-emitting devices. Double-layer devices are fabricated with the structure indium tin oxide (ITO)/Qn/Cpd/LiF/Al, where yellow-emitting 2,3-bis[4-(N-phenyl-9-ethyl-3-carbazolylamino)phenyl]quinoxaline (Qn) serves as the emitting layer. An external quantum efficiency of 1.41 %, a power efficiency of 4.94 lm W-1, and a current efficiency of 1.62 cd A(-1) are achieved at a current density of 100 mA cm(-2).
Effect of alkyl position of pyrrole on structures and properties of conjugated polysquaraines
(2010-05-01)
Lu, Hsiao-Chi
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Whang, Wha-Tzong
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Cheng, Bing-Ming
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材料科學與工程學系
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Department of Materials Science and Engineering
Poly(1-octylpyrrolyl)squaraine and poly(3-octylpyrrolyl)squaraine were synthesized from squaric acid with 1-octylpyrrole and 3-octylpyrrole under identical conditions of condensation. Visible absorption spectra, photoluminescence spectra, TGA curves, and IR spectra were recorded to characterize the structures of these polymers as synthesized: the measured optical and thermal properties are consistent with backbone structures. The polysquaraine from 3-octylpyrrole possesses mostly zwitterionic repeating units (>97%), but the polymer from 1-octylpyrrole consists of zwitterionic and covalent repeating units in a ratio 2:1. Observations from the visible absorption and photoluminescence spectra in varied solvents, TGA curves, and thermal IR measurements for these two polymers reconciled to their structures. This result indicates that the position of the alkyl group in the pyrrole derivative affects the conformation in the condensation of poly(pyrrolyl)squaraine. These polysquaraines are stable below temperature 155 C and their visible absorption and photoluminescence properties in hydrogen-bonding solvents exhibit negative solvatochromism. (C) 2010 Elsevier B.V. All rights reserved.
Effect of backbone on the biaxial retardation of polyimide films in uniaxial stretch
(2007-05-15)
King, Jinn-Shing
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Whang, Wha-Tzong
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Lee, Wen-Chin
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Chang, Li-Ming
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材料科學與工程學系
A biaxial-retardation film prepared from the uniaxial-stretched polyimide (PI) film was developed for compensating the viewing angle of liquid-crystal displays. Good uniformity of in-plane bireffingence in well-stretched PI films was observed visually with two crossed polarizers. The prism coupling method was used to measure the n(x), n(y), n(z), and thickness of the stretched PI films. The birefringence variations of n, - n, (difference of refractive indices between x- and y-axes) and n(x) - n(z) during the stretching process were highly affected by PI structure. The polarizability tensors and intrinsic birefringences of the PI repeat units were estimated by Gaussian 98W. It was found that the stretch-induced birefringence is more related to the average polarizability per volume at the low elongation period. (C) 2006 Elsevier B.V. All rights reserved.
Effect of crosslinking agents on the dispersive behaviour of polymer particles in seed swelling polymerisation
(2017-07-25)
Kao, Yu-Chen
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Whang, Wha-Tzong
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Chen, Yi-Chun
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Chen, Kai-Chi
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材料科學與工程學系
This study focused on the effect of crosslinker structure between PMMA on the dispersity of crosslinked particles in seed swelling polymerisation. We used five different crosslinking agents in an assessment of the dispersity of crosslinking monodisperse particles using PMMA seed particles in seed swelling polymerisation. These results show that the structure of the crosslinking agent affects the dispersity during the swelling stage. According to the solubility parameter theory of computation, the departure of similar solubility parameter causes the swollen particles to segregate into more dispersity. (C) 2017 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.
Effect of doping metal ion on holographic storage characteristics of PQ/poly(hydroxyethyl methacrylate-co-methyl methacrylate) hybrids
(2007-01-01)
Cheng, Wei-Sheng
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Whang, Wha-Tzong
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Chang, Yu-Chia
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Chen, Po-Lin
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Hsiao, Yi-Nan
Holographic Storage Characteristics of PQ/poly(methyl methacrylate) have been significantly improved by doping metallic ion Yb+3 and Er+3. The hybrid materials display significant enhancement in the holographic 13 +3 characteristics. The diffraction efficiency promote to 59% with Yb+3, to 47% with Er from the undoped sample is 40%. The increment is up to 47% in Yb+3 sample; the dynamic range enhance to 2.12 and 1.58 on Yb+3 and Er+3 containing sample individually in comparison to 1.16 for the undoped copolymer. The increment of dynamic range is up to 82% for Yb+3 containing sample. The related mechanism of these changes is preliminary discussed with the analysis of UV-vis, FT-IR and Photoluminescence spectroscopy.
Effect of doping metal ion on holographic storage characteristics of PQ/poly(hydroxyethyl methacrylate-co-methyl methacrylate) hybrids - art. no. 66201K
(2007)
Cheng, Wei-Sheng
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Whang, Wha-Tzong
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Chang, Yu-Chia
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Chen, Po-Lin
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Hsiao, Yi-Nan
Holographic Storage Characteristics of PQ/poly(methyl methacrylate) have been significantly improved by doping metallic ion Yb+3 and Er+3. The hybrid materials display significant enhancement in the holographic 13 +3 characteristics. The diffraction efficiency promote to 59% with Yb+3, to 47% with Er from the undoped sample is 40%. The increment is up to 47% in Yb+3 sample; the dynamic range enhance to 2.12 and 1.58 on Yb+3 and Er+3 containing sample individually in comparison to 1.16 for the undoped copolymer. The increment of dynamic range is up to 82% for Yb+3 containing sample. The related mechanism of these changes is preliminary discussed with the analysis of UV-vis, FT-IR and Photoluminescence spectroscopy.
Effect of Ionic Liquid on Structure and Properties of Polysquaraines
(2012-04-10)
Ho, Mei-Chan
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Chao, Ching-Hsun
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Chen, Chun-Hua
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Wu, Ren-Jye
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Whang, Wha-Tzong
Polycondensation of 4-bis[2-(1-methylpyrrol-2-yl)vinyl]-2,5-didodecyloxybenzene and squaric acid yielded the polysquaraine SQ with two isomeric subunits-1,3-addition (zwitterionic) and 1,2-addition (diketonic) moieties in the main chain structure. The former featured a C-O/C=O infrared (IR) absorption frequency at 1622 cm(-1); the latter, a C=O signal at 1716 cm(-1). Traditional synthesis yielded SQ as a powder with metallic luster that could not be cast as a polymer film from solution. When the ionic liquid [Oct(3)NMe][TfO] (IL) was present in the cosolvent of BuOH and benzene (1:3), however, the resulting SQI(x) polymers (x = 0.01-5 wt %) did not precipitate from solution, making it possible to cast continuous free-standing films with a large area (>1 X 1 cm(2)). A greater content of IL in the solution favored the formation of the 1,3-addition zwitterionic subunits in the SQI(x) polymer main chains, thereby changing the physical and optical properties of the polysquaraine, as evidenced in IR and optical absorption spectra. The features in the UV-Vis-NIR absorption spectra of SQ and SQL(x) were dependent on the IL concentration and the nature of the solvent. Among our synthesized SQI(x) polymers, SQI(0.01) and SQI(0.1) formed flexible free-standing films with metallic luster, smooth surfaces, and good semiconductivities (2.27 x 10(-5) and 4.74 x 10(-5) S/cm, respectively). X-ray diffraction patterns revealed that the presence of IL in the polymerization medium increased the SQI(x) interchain packing distance. SQI(0.01), and SQI(0.1) possessed thermal stabilities comparable with that of SQ. Our successful use of IL in the preparation of SQI(x) polymers appears to have great potential for application in ionic liquid-related organic or polymeric preparation and processing.