教師著作
Permanent URI for this collectionhttp://rportal.lib.ntnu.edu.tw/handle/20.500.12235/37076
Browse
54 results
Search Results
Item Biomimetic Synthesis of Silica Films Directed by Polypeptide Brushes.(American Chemical Society, 2008-10-14) J.-C. Wu; Y.-L. Wang; Chia-Chun Chen; Y.-C. ChangBiomimetic porous silica films have been synthesized by polycondensation of tetraethoxysilane on a soft template formed by an “end-tethered poly(l-lysine)” (“t-PLL”) monolayer with a brushlike configuration. The silica formation occurs spontaneously inside the t-PLL at neutral pH and room temperature. The growth of silica fully conforms to the original t-PLL film thicknesses and lateral micropatterns, regardless of a prolonged reaction time and the monomer concentration. The morphologies of biomimetic silica are changed from continuous pleated, discrete spherical to fibrous forms according to the initial t-PLL chain length and surface density. After the t-PLL template is burned off, TEM images show the creation of nanochannel arrays in silica with an average diameter of 10 nm. Overall, our approach has provided a straightforward and environmentally friendly route to directly generate silica films with controllable morphology, thickness, and porosity.Item Low methanol-permeable polyaniline/Nafion composite membrane for direct methanol fuel cells(Elsevier, 2009-05-15) C.-H. Wang; Chia-Chun Chen; H.-C. Hsu; H.-Y. Du; C.-R. Chen; J.-Y. Hwang; L.-C. Chen; H.-C. Shih; J. Stejskal; K.-H. ChenProtonated polyaniline (PANI) is directly polymerized on Nafion 117 (N117), forming a composite membrane, to act as a methanol-blocking layer to reduce the methanol crossover in the direct methanol fuel cell (DMFC), which is beneficial for the DMFC operating at high methanol concentration. The PANI layer grown on the N117 with a thickness of 100 nm has an electrical conductivity of 13.2 S cm−1. The methanol permeability of the PANI/N117 membrane is reduced to 59% of that of the N117 alone, suggesting that the PANI/N117 can effectively reduce the methanol crossover in the DMFC. Comparison of membrane-electrode-assemblies (MEA) using the conventional N117 and the newly developed PANI/N117 composite shows that the PANI/N117-based MEA outputs higher power at high methanol concentration, while the output power of the N117-based MEA is reduced at high methanol concentration due to the methanol crossover. The maximum power density of the PANI/N117-based MEA at 60 °C is 70 mW cm−2 at 6 M methanol solution, which is double the N117-based MEA at the same methanol concentration. The resistance of PANI/N117 composite membrane is reduced at elevated methanol concentration, due to the hydrogen bonding between methanol and PANI pushes the polymer chains apart. It is concluded that the PANI/N117-based MEA performs well at elevated methanol concentration, which is suitable for the long-term operation of the DMFC.Item Correlated Electric Fluctuations in GaN Nanowire Devices(American Scientific Publishers, 2009-02-01) L.-C. Li; S.-Y. Huang; J.-A. Wei; Y.-W. Suen; M.-W. Lee; W.-H. Hsieh; T.-W. Liu; Chia-Chun ChenWe report an experimental study on the correlation spectrums between different sections of a multi-contact GaN nanowire device. Our results indicate that there exists a negative correlation between the voltage fluctuations of adjacent sections of the nanowire separated by a metal contact in the transition region between the low-frequency 1/f noise and the high-frequency white thermal noise. We suggest that this correlation is caused by the voltage fluctuation under the contact area.Item Chemical Enhancer Induced Changes in the Mechanisms of Transdermal Delivery of Zinc Oxide Nanoparticles(Elsevier, 2009-06-01) T.-R. Kuo; C.-L.Wu; C.-T. Hsu; W. Lo; S.-J. Chiang; S.-J. Lin; C.-Y. Dong; Chia-Chun ChenThe overlapping wavelength of photoluminescence (PL) of zinc oxide nanoparticles (ZnO NPs) and autofluorescence (AF) from the stratum corneum (SC) has for a long time held back researchers from investigating the chemically enhanced penetration pathways of ZnO NPs into the SC lipids. However, the non-linear polarization effect of second harmonic generation (SHG) may be used for ZnO NPs to be distinguished from the AF of the SC. This study combined the SHG of ZnO NPs and the AF of the SC to image the transdermal delivery of ZnO NPs under the chemical enhancer conditions of oleic acid (OA), ethanol (EtOH) and oleic acid-ethanol (OA-EtOH). In addition to qualitative imaging, the microtransport properties of ZnO NPs were quantified to give the enhancements of the vehicle-to-skin partition coefficient (K), the SHG intensity gradient (G) and the effective diffusion path length (L). The results showed that OA, EtOH and OA-EtOH were all capable of enhancing the transdermal delivery of ZnO NPs by increasing the intercellular lipid fluidity or extracting lipids from the SC.Item Silver-Nanoparticle-Conjugated Polypeptide Brushes for Surface-Enhanced Raman Scattering(American Chemical Society, 2009-08-06) D.-Y. Wang; T.-S Teng; Y.-C. Wu; Y.-C. Lee; K.-H. Chen; C.-H. Chen; Y.-C. Chang; Chia-Chun ChenA soft surface-enhanced Raman scattering (SERS) substrate was fabricated based on a three-dimensional (3D) structure of biocompatible end-tethered poly(l-lysine) (“t-PLL”) with a brushlike configuration conjugated with silver nanoparticles (Ag NPs) (Ag NP-t-PLL film). The conjugation procedures were carefully adjusted to generate the films with different interval widths (W) between Ag NPs and diameters (D) of Ag NPs. The resulting film was then characterized by zeta potential, CD spectropolarimeter, and scanning electron microscopy. Furthermore, the studies of SERS enhancements using Ag NP-t-PLL film as a substrate were performed. The significant increases of SERS enhancements have been obtained as W/D was decreased from 0.9 to 0.2. Our results not only afford a facile fabrication of a 3D soft substrate for SERS with high sensitivity and biocompatibility but also offer great potentials for the development of new biosensors.Item Extended Red Light Harvesting in a Poly(3-hexylthiophene)/Iron Disulfide Nanocrystal Hybrid Solar Cell(IOP Publishing, 2009-10-07) Y.-Y. Lin; D.-Y.Wang; H.-C. Yen; H.-L. Chen; Chia-Chun Chen; C.-M. Chen; C.-Y. Tang; C.-W. ChenA polymer solar cell based on poly(3-hexylthiophene) (P3HT)/iron disulfide (FeS2) nanocrystal (NC) hybrid is presented. The FeS2 NCs of 10 nm in diameter were homogeneously blended with P3HT to form an active layer of a solar cell. An extended red light harvesting up to 900 nm resulting from the NCs in the device has been demonstrated, compared to a typical absorption edge of 650 nm of a pristine P3HT. The environmentally friendly and low-cost FeS2 NCs can be used as a promising candidate for an acceptor in the polymer solar cell device application with an enhanced photovoltaic response in the extended red light region.Item On-chip Fabrication of Well-aligned and Contact-barrier-free GaN Nanobridge Devices with Ultrahigh Photocurrent Responsivity(Wiley-VCH Verlag, 2008-07-01) R.-S. Chen; S.-W. Wang; Z.-H. Lan; J. T.-H. Tsai; C.-T. Wu; L.-C. Chen; K.-H. Chen; Y.-S. Huang; Chia-Chun ChenBuilding nanobridges: Direct integration of an ensemble of GaN nanowires (n) onto a microchip produces a viable nanobridge (NB) device with good alignment and contact performance, the design of which demonstrates the potential of nanowires for sensor development. These GaN NBs have strong surface-enhanced photoconductivity with ultrahigh responsivityItem Direct-growth of Polyaniline Nanowires for Enzyme-immobilization and Glucose Detection(Elsevier, 2009-04-01) Y.-Y. Horng; Y.-K. Hsu; A. Ganguly; Chia-Chun Chen; L.-C. Chen; K.-H. ChenAmperometric enzyme biosensor based on the glucose oxidase (GOx) incorporated polyaniline nanowires (PANI-NWs) on carbon cloth (CC) electrode was demonstrated. The simple, direct-growth of PANI-NWs on CC, via electrochemical polymerization, provides free-standing, template-independent, hence almost (interfacial) defects-free nanostructures. The defect-free interfaces, along with the excellently sensitive organic nanostructured-surface, as evident from its significantly large effective surface area (24 times the geometric area) for redox-sensing, allows efficient entrapment/immobilization and sensing of biomolecules, via rapid electron-transfer at NWs-CC. The GOx-immobilized PANI-NWs/CC, even in initial unoptimized stage, exhibited an excellent sensitivity, ∼2.5 mA mM−1 cm−2, to glucose, over detection range 0–8 mM, adequate for clinical monitoring of human glucose levels. The report clearly reveals a cost-effective simple system possessing enormous potentiality for biosensors, bioenergy and bioelectronics applications.Item Controlled Growth and Magnetic Property of FePt Nanostructure: Cuboctahedron, Octapod, Truncated Cube and Cube(American Chemical Society, 2009-10-27) S.-W. Chou; C.-L. Zhu; S. Neeleshwar; C.-L. Chen; Y.-Y. Chen; Chia-Chun ChenThe strategy for shape control of alloy FePt nanocrystal was studied systematically. By the careful adjustments of reaction parameters in a solution reaction, surfactant−facet bindings on the growth seed were controlled delicately. FePt octapod, cuboctahedron, truncated cube, and nanocube were successfully prepared from cuboctahedral seed and examined by high-resolution transmission electron microscopy. The formations of FePt nanostructures were mainly attributed to the differences in the growth rate between the {111} and {100} planes of cuboctahedral seeds. The magnetic measurements showed that the order of volume, V(nanocube) > V(octapod) > V(cuboctahedron) obviously reflected the order of saturated magnetization (Ms), Ms (nanocube) > Ms (octapod) > Ms (cuboctahedron). Furthermore, the measurements of octapod exhibited the highest coercivity and blocking temperature because of its higher surface to volume ratio and more structural facets.Item High-phase-purity zinc-blende InN on r-plane sapphire substrate with controlled nitridation pretreatment(American Institute of Physics (AIP), 2008-03-17) C.-L. Hsiao; T.-W. Liu; C.-T. Wu; H.-C. Hsu; G.-M. Hsu; L.-C. Chen; W.-Y. Shiao; C.-C. Yang; A. Gaellstroem; P.-O. Holtz; Chia-Chun Chen; K.-H. ChenHigh-phase-purity zinc-blende (zb) InN thin film has been grown by plasma-assisted molecular-beam epitaxy on r-plane sapphire substrate pretreated with nitridation. X-ray diffraction analysis shows that the phase of the InN films changes from wurtzite (w) InN to a mixture of w-InN and zb-InN, to zb-InN with increasing nitridation time. High-resolution transmission electron microscopy reveals an ultrathin crystallized interlayer produced by substrate nitridation, which plays an important role in controlling the InN phase. Photoluminescence emission of zb-InN measured at 20 K shows a peak at a very low energy, 0.636 eV, and an absorption edge at ∼0.62 eV is observed at 2 K, which is the lowest bandgap reported to date among the III-nitride semiconductors.