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Item Applications of Carbohydrate-Gold Nanoparticles for Volumetric Flow Measurements Using an Opto-Acoustic Technique(Taipei, Taiwan, R.O.C. ： The Chinese Chemical Society, 2008-02-01) C.-Y. Yang; C.-W.Wei; Y.-P. Lin; H.-C. Tseng; Y.-N. Wu; Chia-Chun Chen; D.-B. Shieh; P.-C. LiGold nanoparticles with carbohydrate ligands attached on their surface have been synthesized and characterized with various techniques. The new nanoparticle conjugates have shown great potentials as a contrast agent for opto-acoustic imaging. Hemocompatibility measurements of human blood for the carbohydrate-gold nanoparticles have shown that the conjugates are feasible for in vivo testing. Preliminary quantitative flow measurements using the conjugates were also studied in this work based on the indicator-dilution theory. In vitro phantom experiments were designed and conducted, and results were discussed.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 Blueshift of yellow luminescence band in self-ion-implanted n-GaN nanowire(American Institute of Physics (AIP), 2004-05-03) S. Dhara; A Datta; C.-T. Wu; Z.-H. Lan; K.-H. Chen; Y. -L. Wang; Y.-F. Chen; C.-W. Hsu; L.-C. Chen; H.-M. Lin; Chia-Chun ChenOptical photoluminescence studies are performed in self-ion (Ga+)-implanted nominally dopedn-GaNnanowires. A 50 keV Ga+focused ion beam in the fluence range of 1×1014–2×1016 ions cm−2 is used for the irradiation process. A blueshift is observed for the yellow luminescence (YL) band with increasing fluence. Donor–acceptor pair model with emission involving shallow donor introduced by point-defect clusters related to nitrogen vacancies and probable deep acceptor created by gallium interstitial clusters is responsible for the shift. High-temperature annealing in nitrogen ambient restores the peak position of YL band by removing nitrogen vacancies.Item Carrier Transfer Induced Photoluminescence Change in Metal-Semiconductor Core-Shell Nanostructures(American Institute of Physics, 2006-04-17) H.-Y. Lin; Y.-F. Chen; J.-G. Wu; D.-I. Wang; Chia-Chun ChenMetal-semiconductor core-shell nanostructures have been synthesized to explore the influence of metal nanostructures on the photoluminescence of semiconductors. Up to 40 times enhancement in the emission intensity was observed in the Au–CdS core-shell nanostructures. The mechanism where the excited electrons on Au surface by surface plasmon wave transfer to the conduction band of the CdS shell and recombine with holes in the valence band was proposed to interpret the enhancement. Our model can also be used to explain the quenched emission in FePt–CdS core-shell nanostructures and Au–CdSe nanodumbbells.Item Catalytic Growth and Characterization of Gallium Nitride Nanowires(American Chemical Society, 2001-03-28) Chia-Chun Chen; C.-C. Yeh; C.-H. Chen; M.-Y. Yu; H.-L. Liu; J.-J. Wu; K.-H. Chen; L.-C. Chen; J.-Y. Peng; Y.-F. ChenThe preparation of high-purity and -quality gallium nitride nanowires is accomplished by a catalytic growth using gallium and ammonium. A series of catalysts and different reaction parameters were applied to systematically optimize and control the vapor−liquid−solid (VLS) growth of the nanowires. The resulting nanowires show predominantly wurtzite phase; they were up to several micrometers in length, typically with diameters of 10−50 nm. A minimum nanowire diameter of 6 nm has been achieved. Temperature dependence of photoluminescence spectra of the nanowires revealed that the emission mainly comes from wurtzite GaN with little contribution from the cubic phase. Moreover, the thermal quenching of photoluminescence was much reduced in the GaN nanowires. The Raman spectra showed five first-order phonon modes. The frequencies of these peaks were close to those of the bulk GaN, but the modes were significantly broadened, which is indicative of the phonon confinement effects associated with the nanoscale dimensions of the system. Additional Raman modes, not observed in the bulk GaN, were found in the nanowires. The field emission study showing notable emission current with low turn-on field suggests potential of the GaN nanowires in field emission applications. This work opens a wide route toward detailed studies of the fundamental properties and potential applications of semiconductor nanowires.Item A Chain-Structure Nanotube: Growth and Characterization of Single-Crystal Sb2S3 Nanotubes via a Chemical Vapor Transport Reaction(Wiley-VCH Verlag, 2004-04-01) J. Yang; Y.-C. Lin; H.-M. Liu; Chia-Chun ChenSingle-crystal Sb2S3 nanotubes with chain-like structures (see Figure) have been successfully synthesized by chemical vapor transport using sulfur as the transport agent. Detailed characterization of the nanotubes shows the growth direction of Sb2S3 nanotubes is determined by the crystallographic orientation of the chain-like building blocks. A mechanism explaining the formation of the nanotubes is presented.Item Characterization of Nanodome on GaN Nanowires Formed with Ga Ion Irradiation(Nihon Kinzoku Gakkai, 2004-01-01) S. Muto; S. Dahara; A. Datta; C.-W. Hsu; C.-T. Wu; C.-H. Shen; L. -C. Chen; K.-H. Chen; Y.-L. Wang; T. Tanabe; T. Maruyama; H.-M. Lin; Chia-Chun ChenStructure of nano-domes formed by Ga+ ion irradiation with a focused ion beam (FIB) apparatus onto GaN nanowires (NWs) was examined with conventional transmission electron microscopy (CTEM), electron energy-loss spectroscopy (EELS) and energy-filtering TEM (EF-TEM). The nano-dome consisted of metallic gallium, covered by a GaN layer, the structure of which is amorphous or liquid. It is considered that the dome structure is formed by preferential displacement of lighter element (N) and agglomeration of heavier one (Ga). 1 MeV electron irradiation onto the sample pre-irradiated by Ga+ ions at a dose below the threshold for the dome formation induced the N2 bubble formation without segregating Ga atoms, which suggests the radiation-enhanced diffusion (RED) of heavy atoms plays an important role in the nano-dome formation.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 Chemical Transformation from FePt to Fe1-xPtMx (M = Ru, Ni, Sn) Nanocrystals by a Cation Redox Reaction: X-ray Absorption Spectroscopic Studies(American Chemical Society, 2007-02-14) D.-Y. Wang; C.-H. Chen; H.-C. Yen; Y.-L. Lin; P.-Y. Huang; B.-J. Hwang; Chia-Chun ChenNew ternary metal nanocrystals of Fe1-xPtMx (M = Ru3+, Sn2+, or Ni2+) were synthesized by chemical transformation from FePt nanocrystals using a cation redox reaction in a solution. The structure and composition of resulting nanocrystals were characterized by high-resolution transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and X-ray photoemission spectroscopy (XPS). Moreover, X-ray absorption near-edge spectroscopy (XANES) was employed to confirm the chemical transformation from FePt to Fe1-xPtRux nanocrystals. The analyses of extended X-ray absorption find structure (EXAFS) revealed the detailed binding structures and coordination numbers of both FePt and Fe1-xPtRux nanocrystals. The results suggested that iron atoms of FePt lattices were oxidized to be Fe2+ and Fe3+ ions and were replaced by ruthenium atoms from the reduction of Ru3+ ions in solution to form Fe1-xPtRux lattices. Our method has opened a new route to easily and rapidly prepare a solid-solution type of ternary metal nanocrystals for catalytic 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 Controlled growth of aligned alpha-helical-polypeptide brushes for tunable electrical conductivity(American Institute of Physics, 2011-03-28) J.-C. Wu; Chia-Chun Chen; K.-H. Chen; Y.-C. ChangPolypeptide based molecular diode with high rectification ratio (∼122 at ±0.422 V) is formed by controlling molecular order and orientation. A film of tethered poly(γ-benzyl-L-glutamate) (PBLG) with high degree of molecular orientation was formed by solvent pair (good/bad) treatment. I-V characterization of the well aligned polypeptides showed that the rectification ratio of PBLG was sufficiently large for potential diode and transistor applications.Item Controlled Growth of Aluminium Nitride Nanorod Arrays via Chemical Vapour Deposition(IOP Publishing, 2006-06-14) J. Yang; T.-W. Liu; C.-W. Hsu; L.-C. Chen; K.-H. Chen; Chia-Chun ChenLarge-area and high-density arrays of AlN nanorods were synthesized at low temperature via a template-free and catalyst-free chemical vapour deposition. The quasi-aligned AlN nanorods were identified to grow along the c-axis and preferentially orient with their growth direction perpendicular to the substrate. Further studies showed that the AlN nanorods were grown on a buffer layer formed at the beginning of the reaction. By changing the flow rate of the carrier gas at the beginning of the reaction, we successfully obtained nanorods with different orientations on the substrate. The Raman spectrum and cathodoluminescence spectrum of the AlN nanorods at room temperature reveal the existence of oxygen-related defects in the nanorods.Item Controlled Growth of Cubic Cadmium Sulfide Nanoparticles Using Patterned Self-Assembled Monolayers as a Template(Wiley-VCH Verlag, 2001-01-01) Chia-Chun Chen; J.-J. LinSpheres, rods, and wires are the most usual morphologies of semiconductor nanoparticles. Here, in contrast, cube-shaped crystals of cadmium sulfide (e.g., see Figure) are reported. The “nanocubes” are produced on self-assembled monolayers of alkanethiolates on gold, and the size of the cubes can be controlled through the use of different solvents during the synthesis.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 Crystallization, Melting and Morphology of PEO in PEO/MWNT-g-PMMA Blends(ELSEVIER, 2005-11-21) Y.-T. Shieh; G.-L. Liu; K.-C. Huang; Chia-Chun ChenThe dispersion of multi-walled carbon nanotubes (MWNTs) in crystalline poly(ethylene oxide) (PEO) is significantly improved by grafting with poly(methyl methacrylate) (PMMA) on surface of MWNTs via emulsion reactions. The synthesized MWNTs-g-PMMA is soluble in solvents that can dissolve PMMA and is well dispersed in PEO. The effects of the MWNTs-g-PMMA on PEO crystallization and its use as a reinforcement for PEO are investigated using DMA, DSC, POM, and SAXS. DMA data show that the PEO/MWNTs-g-PMMA blends containing up to 30 wt% MWNTs-g-PMMA are compatible. DSC data show the crystallization of PEO is enhanced by the MWNTs-g-PMMA, accompanying with a decreased thickness of crystal layers and an increased thickness of amorphous layers of the PEO lamellar stacks, in combination with SAXS data.Item Diethylene Glycol Ether-Linked 3, 4, 5,-Trihydroxybenzamides as Triple Branched Dendritic Anchors to CdSe/ZnS Core/Shell Type Nanoparticles: Potential Hydrophilic Fluorescent Probes(Royal Society of Chemistry, 2005-05-21) C.-T. Chen; V.-D. Pawar; Y.-S. Munot; Chia-Chun Chen; C.-R. HsuFunctionalized N-2-mercaptoethyl-gallamides bearing three or five hydroxyl units that are tethered with diethylene glycol ether(s) allow for transferring hydrophobically pyridine-capped CdSe/ZnS core/shell nanoparticles from an organic to an aqueous layer with intact fluorescent profiles.Item Direct evidence of type II band alignment in nanoscale P3HT/CdSe heterostructures(IOP Publishing, 2011-02-11) C.-H. Wang; C.-W. Chen; Y.-T. Chen; C.-T. Chen; Y.-F.Chen; S.-W. Chou; Chia-Chun ChenDue to inherent advantages of both constituent materials, organic/inorganic hybrid composites have attracted increasing attention. One of the fundamental issues needed to be resolved is their band alignment, which governs most of the electrical and optical properties. Here, we report the investigation of optical transition in poly(3-hexylthiophene) (P3HT)/CdSe nano-composites (NCs). It is found that the relaxation dynamics of photo-carriers in NCs is dominated by charge separation effects. Based on the band bending effect and the quantum confinement energy of electrons in the conduction band of CdSe quantum dots, we provide direct evidence of type II band alignment in P3HT/CdSe NCs. The establishment of a type II transition in NCs is very useful for the future design of efficient optoelectronic devices based on conjugated polymer/semiconductor hybrid systems.Item 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 DNA-Gold Nanorod Conjugates for Remote Control of Localized Gene Expression by Near Infrared Irradiation(American Chemical Society, 2006-03-22) Chia-Chun Chen; Y.-P. Lin; C.-W. Wang; H.-C. Tzeng; C.-H. Wu; Y.-C. Chen; C.-P. Chen; L.-C. Chen; Y.-C. WuGold nanorods were attached to the gene of enhanced green fluorescence protein (EGFP) for the remote control of gene expression in living cells. The UV−vis spectroscopy, electrophoresis, and transmission electron microscopy (TEM) were used to study the optical and structural properties of the EGFP DNA and gold nanorod (EGFP−GNR) conjugates before and after femto-second near-infrared (NIR) laser irradiation. Upon NIR irradiation, the gold nanorods of EGFP−GNR conjugates underwent shape transformation that resulted in the release of EGFP DNA. When EGFP−GNR conjugates were delivered to cultured HeLa cells, induced GFP expression was specifically observed in cells that were locally exposed to NIR irradiation. Our results demonstrate the feasibility of using gold nanorods and NIR irradiation as means of remote control of gene expression in specific cells. This approach has potential applications in biological and medical studies.Item Efficient light harvesting and carrier transport in PbS quantum dots/silicon nanotips heterojunctions(IOP Publishing, 2011-03-02) C.-Y. Huang; D.-Y. Wang; C.-H. Wang; Y.-T. Wang; Y.-T. Jiang; Y.-J. Yang; Chia-Chun Chen; Y.-F. ChenLight harvesting from nanocomposites consisting of silicon (Si) nanotips and PbS quantum dots (QDs) has been investigated. We show that Si nanotips provide direct carrier transport paths, additional interfacial area and light trapping. We observe that there is a dramatic enhancement in short-circuit current (from 9.34 to 14.17 mA cm−2) with nanotips structure than that of the bulk Si wafer. In addition, with an additional electron blocking layer, the photovoltaic performance can be further increased. The nanocomposites consisting of QDs and Si nanotips therefore open a promising route for efficient light harvesting from visible to infrared with improved power conversion efficiency.