Browsing by Author "Lee, Tai-Jung"

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Characterization and drug release behavior of chip-like amphiphilic chitosan-silica hybrid hydrogel for electrically modulated release of ethosuximide: an in vitro study
(2011)
Huang, Wei-Chen
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Lee, Tai-Jung
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Hsiao, Chi-Sheng
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Chen, San-Yuan
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Liu, Dean-Mo
The hydrogel response under environmental induction often decreases with time because of the mechanical weakness of polymeric hydrogels. Therefore, to reinforce the conventional hydrogels with improved responsiveness and service performance to an external stimulus, a hybrid hydrogel consisting of an amphiphilic chitosan and inorganic silica with a minimal concentration of organic cross-linker was made in order to ascertain the biocompatibility of resulting hydrogels and improve stimulus-induced responsiveness. The hybrid hydrogels generally illustrated a rapid drug (ethosuximide, ESM) release profile over a time period of less than 60 minutes. However, after assembling the hybrid hydrogels into a chip-like device, the sandwiched hybrid showed, under a number of applied DC voltages, a variety of release profiles from a burst-like to slow-elution pattern. A release mechanism was proposed and can be successfully explained as a result of combined effects of electrophoretic and electroosmotic operations. Kinetic analysis indicated that the ESM released from the chip-like device is essentially a shuttle between the swelling-controlled pattern and the diffusion-controlled mechanism, depending on the chemical compositions that were used to prepare the hybrid hydrogels under a given DC electrical field. The hybrid hydrogel chip-like device designed in this work has experimentally proved its technical potential as an electrically responsive drug delivery system to meet various biomedical demands.
CO2 Sorbents with Scaffold-like CaAl Layered Double Hydroxides as Precursors for CO2 Capture at High Temperatures
(2013-06-01)
Chang, Po-Hsueh
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Lee, Tai-Jung
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Chang, Yen-Po
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Chen, San-Yuan
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材料科學與工程學系
A highly stable high-temperature CO2 sorbent consisting of scaffold-like Ca-rich oxides (CaAlO) with rapid absorption kinetics and a high capacity is described. The Ca-rich oxides were prepared by annealing CaAlNO3 layered double hydroxide (LDH) precursors through a sol-gel process with Al(OiP)3 and Ca(NO3)2 with Ca2+/Al3+ ratios of 1:1, 2:1, 4:1, and 7:1. XRD indicated that only LDH powders were formed for Ca2+/Al3+ ratios of 2:1. However, both LDH and Ca(OH)2 phases were produced at higher ratios. Both TEM and SEM observations indicated that the CaAlNO3 LDHs displayed a scaffold-like porous structure morphology rather than platelet-like particles. Upon annealing at 600 degrees C, a highly stable porous network structure of the CaO-based CaAlO mixed oxide (CAMO), composed of CaO and Ca12Al14O33, was still present. The CAMO exhibited high specific surface areas (up to 191m2g-1) and a pore size distribution of 3-6nm, which allowed rapid diffusion of CO2 into the interior of the material, inducing fast carbonation/calcination and enhancing the sintering-resistant nature over multiple carbonation/calcination cycles for CO2 absorption at 700 degrees C. Thermogravimetric analysis results indicated that a CO2 capture capacity of approximately 49wt% could be obtained with rapid absorption from the porous 7:1 CAMO sorbents by carbonation at 700 degrees C for 5min. Also, 94-98% of the initial CO2 capture capability was retained after 50cycles of multiple carbonation/calcination tests. Therefore, the CAMO framework is a good isolator for preventing the aggregation of CaO particles, and it is suitable for long-term cyclic operation in high-temperature environments.
Morphological and structural evolution of mesoporous calcium aluminate nanocomposites by microwave-assisted synthesis
(2014-01-01)
Chang, Yen-Po
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Chang, Po-Hsueh
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Lee, Yuan-Tse
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Lee, Tai-Jung
;
Lai, Yen-Ho
Novel special dual-structure calcium aluminate nanocomposites consisting of mesoporous Ca-containing Al2O3 nanonetworks with Ca12Al14O33 polycrystalline nanorods have been successfully synthesized using the microwave-hydrothermal (M-H) process in an alcohol solution consisting of calcium nitrate and mesoporous alumina, followed by calcination at a lower temperature (e.g., less than 600 degrees C). The mesoporous Ca-containing aluminate nanocomposites possessed a specific surface area of 51 m(2) g(-1) and a broad pore size distribution of 4-12 nm in diameter, as observed from N-2 adsorption/desorption measurements. The results showed that highly dispersed Ca12Al14O33 nanorods grown on the mesoporous nanostructure were obtained by varying the molar ratio of Ca/Al or by controlling microwave heating time, as characterized by scanning electron microscopy (SEM), transmission electron microscopy/electronic energy loss spectroscopy (TEM/EELS) and powder X-ray diffraction (PXRD). The Ca12Al14O33 nanorods with diameters of 50-100 nm and lengths of 200-400 nm were grown in and on the one-dimensional mesochannels. A formation mechanism of the mesoporous Ca-containing aluminate nanocomposites involving amorphous mesoporous hydrated-Al2O3 was also proposed. (C) 2013 Elsevier Inc. All rights reserved.
Self-Reactivated Mesostructured Ca-Al-O Composite for Enhanced High-Temperature CO2 Capture and Carbonation/Calcination Cycles Performance
(2015-03-25)
Chang, Po-hsueh
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Huang, Wei-Chen
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Lee, Tai-Jung
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Chang, Yen-Po
;
Chen, San-Yuan
In this study, highly efficient high-temperature CO2 sorbents of calcium aluminate (Ca-Al-O) mesostructured composite were synthesized using presynthesized mesoporous alumina (MA) as a porous matrix to react with calcium nitrate through a microwave-assisted process. Upon annealing at 600 degrees C, a highly stable mesoporous structure composed of poorly crystalline Ca(12)A(14)O(33) phase and the CaO matrix was obtained. The Ca-Al-O mesostructured sorbents with a Ca2+/Al3+ ratio of 5:1 exhibit an enhanced increasing CO2 absorption kinetics in the CO2 capture capacity from 37.2 wt % to 48.3 wt % without apparent degradation With increasing carbonation/calcination cycling up to 50 at 700 degrees C due to the strong self-reactivation effect of the mesoporous Ca-Al-O microstructure. Remarkable improvements in the CaO-CaCO3 conversion attained from the mesostructured Ca-Al-O composite can be explained using the concept combined with available mesoporous structure and Ca12Al14O33 phase content. However, a high Ca2+/Al3+ =8:1 Ca-Al-O composite causes degradation because the pores become blocked and partial sintering induces CaO agglomeration.