Browsing by Author "Zhu, Chao-Yuan"

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A cross-linkable triphenylamine derivative as a hole injection/transporting material in organic light-emitting diodes
(2015-01-01)
Shih, Hsi-Kang
;
Chu, Yu-Lin
;
Chang, Feng-Chih
;
Zhu, Chao-Yuan
;
Kuo, Shiao-Wei
We have synthesized TPABZ, a new thermally cross-linkable triphenylamine derivative containing a benzoxazine functional group, for application in organic light-emitting diodes (OLEDs). We used differential scanning calorimetry, thermogravimetric analysis, UV-Vis spectroscopy, and cyclic voltammetry to investigate the thermal, physical, and electrochemical properties of TPABZ, which is readily polymerized, through ring-opening polymerization of its benzoxazine unit, upon heating at 220 degrees C for 30 min. The cured TPABZ (P-TPABZ) is suitable for use as a hole injection/transport material in OLEDs because it has an appropriate HOMO energy level (-5.16 eV) to form a stepwise energy ladder and a high LUMO energy level (-1.68 eV) with great potential for electron blocking. We fabricated multilayered OLEDs (ITO/TPABZ or P-TPABZ/NPB/Alq(3)/LiF/Al) through successive spin-coating and vacuum deposition processes; the device incorporating P-TPABZ exhibited good performance (EQE: 2.44%; LEmax: 8.42 cd A(-1); PEmax: 4.34 lm W-1).
A solvent-resistant azide-based hole injection/transporting conjugated polymer for fluorescent and phosphorescent light-emitting diodes
(2015-01-01)
Huang, Cheng-Wei
;
Chang, Feng-Chih
;
Chu, Yu-Lin
;
Lai, Cheng-Chang
;
Lin, Tzu-En
Interfacial mixing of polymers is a critical issue when attempting to improve the charge transport and stabilize the operation of solution-processed organic light-emitting diodes (OLEDs). Herein, we describe a simple methodology for overcoming interfacial mixing, based on the use of a photo-crosslinkable hole injection/transporting material (HITM). We synthesized a conjugated polymer, PTCAzide, bearing ready crosslinking ability and investigated its suitability for use as an HITM. Photo-crosslinking of the PTCAzide copolymer gave X-PTCAzide, which exhibited much higher thermal stability (the glass transition temperature increased by 21 K relative to that of PTCAzide), remarkable electrochemical stability, and excellent solvent-resistance, thereby expanding the operation time of corresponding electronic devices. Such a tris(8-hydroxy-quinolinato) aluminum-based trilayer device reached a maximum brightness of 52 971 cd m(-2), and the maximum luminance efficiency (LE) and power efficiency (eta E) are both higher than those of the corresponding device based on commercial PEDOT:PSS. In addition, a solution-processed phosphorescent OLED device incorporating X-PTCAzide also exhibited good performance (external quantum efficiency: 7.93%; LE: 29.6 cd A(-1); eta E: 14.3 lm W-1; maximum brightness: 34484 cd m(-2)). The efficient and simple photocrosslinking without adding an initiator could facilitate the fabrication process. Thus, PTCAzide appears to be a promising next-generation HITM for the development of highly efficient and inexpensive OLEDs. Its photo-crosslinkable nature allows improvements in morphological stability and hole injection/transporting ability, leading to more stable devices with better operation, without disrupting molecular packing or charge transport.
Characteristics of high-water-uptake activated carbon/Nafion hybrid membranes for proton exchange membrane fuel cells
(2013-03-15)
Chien, Hung-Chung
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Tsai, Li-Duan
;
Lai, Chien-Ming
;
Lin, Jiunn-Nan
;
Zhu, Chao-Yuan
A cost-effective and high-throughput method for producing high-water-uptake membranes is developed by combining high-porosity and superior-surface-area activated carbon with Nation. The resultant activated carbon/Nafion hybrid composite exhibits high water uptake and an improved proton conductivity, which can be exploited in a proton exchange membrane fuel cell (PEMFC). This hybrid membrane displays a superior performance to that of the commercial Nation 211 when used in fuel-cell measurements. Electrochemical impedance spectroscopy (EIS) is used to simulate the changes in resistance during the operation of the fuel cells and conclusively explains the improved performance of the composite membranes. (C) 2012 Elsevier B.V. All rights reserved.
Functional Supramolecular Polypeptides Involving pi-pi Stacking and Strong Hydrogen-Bonding Interactions: A Conformation Study toward Carbon Nanotubes (CNTs) Dispersion
(2016-08-09)
Huang, Cheng-Wei
;
Mohamed, Mohamed Gamal
;
Zhu, Chao-Yuan
;
Kuo, Shiao-Wei
;
應用化學系
New supramolecular polypeptides have been prepared through simple ring-opening polymerization and "click" reactions. Postfunctionalization with diaminopyridine (DAP) moieties, capable of multiple hydrogen bonding, was an efficient approach toward forming a-helical-dominant polypeptides. The physically cross-linked networks produced upon self-organization of the DAP units increased the glass transition temperature (T-g) of the polymers and sustained the secondary structures of the polypeptides. Additional thermal responsivity resulted from dynamic noncovalent bonding on the polymer side chains. Molecular recognition through heterocomplementary DAP thymine (T) base pairs was revealed spectroscopically and then used to construct poly(y-propargylL-glutamate)-g-N-(6-acetamidopyridin-2-y1)-11-undecanamide/thyminylpyrene (PPLG-DAP/Py-T) supramolecular complexes. Transmission electron microscopy images revealed that this complex was an efficient dispersant of carbon nanotubes (CNTs). Indeed, it could disperse CNTs in both polar and nonpolar media, the direct result of combining two modes of secondary noncovalent bonding: multiple hydrogen bonding and pi-pi interactions. Furthermore, CNT composites fabricated with biocompatible polymers and high value of T-g should enable the development of bio-inspired carbon nanostructures and lead the way toward their biomedical applications.
Highly hydrated Nafion/activated carbon hybrids
(2012-10-12)
Chien, Hung-Chung
;
Tsai, Li-Duan
;
Kelarakis, Antonios
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Lai, Chien-Ming
;
Lin, Jiunn-Nan
The incorporation of highly porous activated carbon (aC) to Nafion membranes confers unprecedented levels of water uptake (4 times higher for 10 wt% aC compared to neat Nafion) at a minimal dimensional swelling and results in dramatic enhancements in ionic conductivity at low relative humidity. This behavior reveals the development of a robust network of water nanochannels formed by the carbon pores and the polymeric ionic domains which are structurally stabilized by the rigid Nafion backbone and the non-deformable aC particles. (c) 2012 Elsevier Ltd. All rights reserved.
Photo-Crosslinking of Pendent Uracil Units Provides Supramolecular Hole Injection/Transport Conducting Polymers for Highly Efficient Light-Emitting Diodes
(2015-05-01)
Shih, Hsi-Kang
;
Chen, Yi-Han
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Chu, Yu-Lin
;
Cheng, Chih-Chia
;
Chang, Feng-Chih
A new process for modifying a polymeric material for use as a hole injection transport layer in organic light-emitting diodes has been studied, which is through 2 + 2 photodimerization of a DNA-mimetic -conjugated poly(triphenylamine-carbazole) presenting pendent uracil groups (PTC-U) under 1 h of UV irradiation. Multilayer florescence OLED (Organic light-emitting diodes) device with the PTC-U-1hr as a hole injection/transport layer (ITO (Indium tin oxide)/HITL (hole-injection/transport layer) (15 nm)/N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPB) (15 nm)/Tris-(8-hydroxyquinoline)aluminum (Alq(3)) (60 nm)/LiF (1 nm)/Al (100 nm)) is fabricated, a remarkable improvement in performance (Q(max) (external quantum efficiency) = 2.65%, B-max (maximum brightness) = 56,704 cd/m(2), and LE (luminance efficiency)(max) = 8.9 cd/A) relative to the control PTC-U (Q(max) = 2.40%, B-max = 40,490 cd/m(2), and LEmax = 8.0 cd/A). Multilayer phosphorescence OLED device with the PTC-U-1hr as a hole injection/transport layer (ITO/HITL (15 nm)/Ir(ppy)(3):PVK (40 nm)/BCP (10nm)/Alq(3) (40 nm)/LiF (1 nm)/Al (100 nm)) is fabricated by successive spin-coating processes, a remarkable improvement in performance (Q(max) = 9.68%, B-max = 41,466 cd/m(2), and LEmax = 36.6 cd/A) relative to the control PTC-U (Q(max) = 8.35%, B-max = 34,978 cd/m(2), and LEmax = 30.8 cd/A) and the commercial product (poly(3,4-ethylenedioxythiophene):polystyrenesulfonate) PEDOT:PSS (Q(max) = 4.29%, B-max = 15,678 cd/m(2), and LEmax = 16.2 cd/A) has been achieved.
Poly(ethylene glycol) modified activated carbon for high performance proton exchange membrane fuel cells
(2013-08-30)
Tsai, Li-Duan
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Chien, Hung-Chung
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Wang, Cheng-Hong
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Lai, Chien-Ming
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Lin, Jiunn-Nan
A high water retention membrane is developed by co-assembling poly(ethylene glycol) (PEG) grafted activated carbon (AC-PEG) with Nafion. The AC-PEG is prepared via a sol gel process. The use of PEG as a transporting medium in AC-PEG shows a largely improved water retention ability, a higher proton conductivity and a reduced swelling ratio, making it well suited for proton exchange membrane fuel cells (PEMFCs). Further, the composite membranes show improved mechanical properties at high temperature, thus ensuring the structural stability of membranes during the fuel cell operation. Compositional optimized AC-PEG/Nafion composite membrane (15 wt% compared to Nafion) demonstrates a better performance than the commercially available counterpart, Nafion 212, in fuel cell measurements. To identify the key factor of the improved performance, current interrupt technique is used to quantitatively verify the changes of resistance under different relative humidity environment. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Stimuli-responsive supramolecular materials: photo-tunable properties and molecular recognition behavior
(2016)
Huang, Cheng-Wei
;
Wu, Pei-Wei
;
Su, Wei-Hung
;
Zhu, Chao-Yuan
;
Kuo, Shiao-Wei
A new homopolymer of polystyrene (PS) presenting pendant diaminopyridine (DAP) moieties has been prepared using controlled free radical polymerization and a CuAAC "click" reaction. Through directional complementary multiple hydrogen bonding, this PVB-DAP polymer underwent complexation with a thymine-functionalized azobenzene (Azo-T). The resulting supramolecular complex exhibited amorphous and chromophoric behavior without microphase separation. This strategy allowed the fabrication of homogeneous stimuli-responsive thin films with photocontrollable behavior through photoinduced trans-cis isomerization. The PVB-DAP/Azo-T supramolecular complex facilitated the dispersion of an azo-dye through noncovalent interactions; the resulting complex was used to fabricate a surface relief grating displaying an interference pattern. The "recordability" and "rewritability" of these supramolecular complexes suggest that they are promising materials for optical applications and therefore advance the pathway for supramolecular development.
Stimuli-responsive supramolecular materials: photo-tunable properties and molecular recognition behavior
(2016-01-01)
Huang, Cheng-Wei
;
Wu, Pei-Wei
;
Su, Wei-Hung
;
Zhu, Chao-Yuan
;
Kuo, Shiao-Wei
A new homopolymer of polystyrene (PS) presenting pendant diaminopyridine (DAP) moieties has been prepared using controlled free radical polymerization and a CuAAC "click" reaction. Through directional complementary multiple hydrogen bonding, this PVB-DAP polymer underwent complexation with a thymine-functionalized azobenzene (Azo-T). The resulting supramolecular complex exhibited amorphous and chromophoric behavior without microphase separation. This strategy allowed the fabrication of homogeneous stimuli-responsive thin films with photocontrollable behavior through photoinduced trans-cis isomerization. The PVB-DAP/Azo-T supramolecular complex facilitated the dispersion of an azo-dye through noncovalent interactions; the resulting complex was used to fabricate a surface relief grating displaying an interference pattern. The "recordability" and "rewritability" of these supramolecular complexes suggest that they are promising materials for optical applications and therefore advance the pathway for supramolecular development.
Strong Hydrogen Bonding with Inorganic Pendant Polyhedral Oligomeric Silsesquioxane Nanoparticles Provides High Glass Transition Temperature Poly(methyl methacrylate) Copolymers
(2018-01-01)
Yeh, Shu-Ling
;
Zhu, Chao-Yuan
;
Kuo, Shiao-Wei
;
應用化學系
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Department of Applied Chemistry
We report a series of poly(methyl methacrylate) (PMMA) copolymers containing small amounts of methacrylamide (MAAM) and pendant polyhedral oligomeric silsesquioxane (POSS) methyl acrylate (MAPOSS) segments. The hydrogen bonding interactions of the MAAM monomer units and the inorganic POSS nanoparticle units improved the thermal and mechanical properties of the PMMA copolymers. For example, PMMA copolymerization with 5 wt% PMAAM and 5 wt% PMAPOSS monomers could enhance the glass transition temperature to 142 degrees C, with higher modulus, higher water contact angle, and reasonably high transparency. Such copolymers have potential to replace PMMA homopolymers in optical applications.
Ternary polybenzoxazine/POSS/SWCNT hybrid nanocomposites stabilized through supramolecular interactions
(2016)
Shih, Hsi-Kang
;
Hsieh, Chun-Cheng
;
Mohamed, Mohamed Gamal
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Zhu, Chao-Yuan
;
Kuo, Shiao-Wei
In this study we linked zero-dimensional polyhedral oligomeric silsesquioxane (POSS) with one-dimensional single-walled carbon nanotubes (SWCNTs) as dual-dimensional nanohybrid complexes within polybenzoxazine matrices, stabilized through noncovalent supramolecular interactions. First, we synthesized a new bifunctionalized benzoxazine (Py-Bz-T), presenting thymine (T) and pyrene (Py) units, that displayed excellent thermal properties after thermal curing, because its T moieties increased the physical cross-linking density. Second, we prepared Py-Bz-T/OBA-POSS [octuply adenine (A)-functionalized POSS] nanocomposites and investigated, using nuclear magnetic resonance and Fourier transform infrared spectroscopies, the multiple hydrogen bonding A center dot center dot center dot T interactions between Py-Bz-T and OBA-POSS. Finally, we prepared Py-Bz-T/OBA-POSS/SWCNT ternary hybrid complexes dispersed in THF, stabilized through both multiple hydrogen bonding and pi-pi stacking interactions. Transmission electron microscopy revealed that the SWCNTs were highly dispersed and covered by the Py-Bz-T/OBA-POSS nanocomposites; these ternary hybrid complexes were stabilized through pi-pi interactions between Py-Bz-T/OBA-POSS and the SWCNTs, as evidenced using fluorescence spectroscopy.
Visible-light photocatalytic activity of Ni-doped TiO2 from ab initio calculations
(2012-04-16)
Lin, Yan-Ming
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Jiang, Zhen-Yi
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Zhu, Chao-Yuan
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Hu, Xiao-Yun
;
Zhang, Xiao-Dong
The geometrical structures and electronic properties of Ni-doped anatase and rutile TiO2 were successfully calculated and simulated by a plane wave pseudopotential method based on density functional theory (OFT). Our results show that most Ni 3d states are located in the forbidden band of substitutional Ni to O-doped anatase and rutile TiO2, and mix with O 2p states, resulting in a decrease of the photon excitation energy and red-shift of absorption edge compared to pure anatase and rutile. For substitutional Ni to Ti-doped anatase TiO2 under O-rich growth condition, the band gap has a slight decline of about 0.05 eV compared with pure anatase TiO2 and contains a series of impurity energy levels, which may be responsible for the experimental photocatalytic activity and red-shift of absorption edge. (C) 2012 Elsevier B.V. All rights reserved.