Jia-Yaw Chang

National Tsing Hua University, Hsinchu, Taiwan, Taiwan

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Publications (16)32.57 Total impact

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    ABSTRACT: In situ chemical polymerization is used to prepare composites of multiwalled carbon nanotubes (MWCNTs) that are either wrapped with polyaniline (PANI) (MWP), or with perpendicular aligned PANI (MAP). Systematic study of morphology, composition, structure, thermal stability, and electrical properties is performed as a function of temperature to understand the composite formation. Orientation of PANI chains and the direction of electron transport in MWCNTs and PANI play an important role in conductivity. At room temperature (RT), MWP, wherein PANI and MWCNTs are aligned parallel, exhibits high conductivity, which decreases gradually above RT. Contrary in MAP, the conductivity at RT is lower because of the perpendicular alignment of PANI on the MWCNTs. However, it increases with the increase in temperature, as short chains of PANI switchover and get adsorbed onto the MWCNTs forming a near parallel orientation, in which, aromatic amines of PANI graft to the MWCNTs. Eventually, morphology becomes a dominating factor which influences the conductivity and thermoelectric properties of the composites, above 150 °C. The results show that the morphology, interfacial contact, and the dopant concentration are the key factors in governing the conductivity of MWP and MAP composites at RT and above. These observations are supported by X-ray diffraction, X-ray photoelectron spectroscopy, and time of flight-secondary ionization mass spectrometry study.
    Current Nanoscience 01/2010; 6(1):59-68. · 1.36 Impact Factor
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    ABSTRACT: Simultaneous thermogravimetric analysis and thermo-Raman spectroscopy (TRS) measurements for in situ monitoring of wet chemical reaction of Ni(OH)2·4H2O and Al(OH)3 forming NiO–Al2O3 nanoparticles is studied and compared with the solid-state reaction. Herein, a different approach of synthesis and monitoring of NiO–Al2O3 by TRS is presented, in which, in situ thermo-Raman spectra are recorded at every degree interval from 25 to 800°C to understand the structural and compositional changes in NiO–Al2O3 as a function of temperature. Slow controlled heating of the sample as in TRS, enables better control over morphology and particle size distribution (∼10–20nm diameter). The X-ray diffraction (XRD) shows that smaller particle size is obtained using wet chemical reaction than the solid-state reaction (∼25nm diameter). TRS studies also reveal that, the bulk NiAl2O4 forms at temperatures above 800°C, although, the onset of formation is around 600°C. Condensation of Al(OH)3 forming Al2O3 is also monitored, wherein, presence of hydrocarbon is found to contribute to the observed fluorescence background. Based on the TRS and complementary characterizations using XRD, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray analysis, the formation of supported NiO–Al2O3 is discussed.
    Materials Chemistry and Physics - MATER CHEM PHYS. 01/2010; 119(1):86-92.
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    ABSTRACT: Surface modification of quantum dots (QDs) for improved photo and physicochemical properties is a topic of potential technological interest. Herein, we report on the synthesis of aggregation free 11-mercaptoundecanoic acid and tetraaniline (TA) capped CdS QDs with narrow size distribution (∼2.3nm diameter), which are further characterized using UV–visible spectroscopy, photoluminescence spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The TA capped CdS QDs show improved photoluminescence and photostability, which is attributed to the effective grafting of TA on CdS QDs through N-atoms, changing the surface chemical environment and facilitating charge transfer.
    Materials Chemistry and Physics - MATER CHEM PHYS. 01/2010; 123(2):742-746.
  • Carbon. 01/2007; 45(7):1586-1589.
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    ABSTRACT: High quality zinc oxide (ZnO) nanorods are synthesized using a seed-mediated sol–gel method. Systematic studies reveal that the use of nanosized ZnO seeds along with critical growth parameters facilitate the formation of ZnO nanorods with high aspect ratio and low oxygen-vacancy defect density, which might find potential applications in nanodevices.
    Scripta Materialia - SCRIPTA MATER. 01/2006; 54(3):411-415.
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    ABSTRACT: The design and formation of a linear assembly of gold nanorods using a biomolecular recognition system are described. Anti-mouse IgG was immobilized on the {111} end faces of gold nanorods through a thioctic acid containing a terminal carboxyl group. The biofunctionalized nanorods can be assembled with the desired length using mouse IgG for biorecognition and binding. The gold nanorods can be assembled to extended nanorod chains, which can be as long as 3 microm. These assembled nanostructures may be used as the precursors for future nanodevices.
    Chemical Communications 03/2005; · 6.38 Impact Factor
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    ABSTRACT: For Abstract see ChemInform Abstract in Full Text.
    ChemInform 01/2004; 35(27).
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    ABSTRACT: Multiwall carbon nanotubes (MWNTs) with different morphology were prepared using supercritical water (SCW) oxidation and investigated by transmission electron microscope (TEM) and electron energy-loss spectroscopy (EELS). TEM results indicate that the peeling and sharpening of MWNTs are influenced by the etching process in SCW oxidation, of which oxidation time and amount of oxygen used is crucial. A simplified etching model is proposed, which indicates that the difference of mean etching rate between two adjoining blocks causes the morphological variation of MWNTs. The EELS results show change in characteristic energy-loss peaks as a function of total shell numbers along longitudinal axis of individual peeled tube.
    Applied Physics Letters 01/2004; 85. · 3.79 Impact Factor
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    ABSTRACT: Bismuth molybdate (α-Bi2Mo3O12 phase) nanorods (av. diameter =10 nm) are synthesized for the first time, by pyridine intercalative sonochemical route and characterized for phase purity, composition, and morphology by Raman spectroscopy, thermal analysis, NMR, time of flight secondary ionization mass spectrometer, X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray analysis. A possible sonochemical mechanism for formation of the α-Bi2Mo3O12 phase nanorods is discussed.
    Chemical Physics Letters 01/2004; 383(1):208-213. · 2.15 Impact Factor
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    ABSTRACT: A method has been developed for the determination of endocrine disruptors (EDs) (containing hydroxyl groups) in surface water from different sources. The surface water samples from different sites including school and local dormitory sewage effluents, lake water and river water were collected and analyzed. In this method, the pretreated sample is directly analyzed by GC-MS using on-line derivatization, where tetramethylammonium hydroxide (TMA-OH) was used as the derivatizing agent. Use of large-volume direct sample introduction (DSI) and co-injection of the sample and TMAOH avoids external contaminations as observed in conventional derivatization protocols. Additionally, the use of chemical ionization (CI) and CI-MS/MS could enable detection of EDs at lower concentrations and reduce the matrices' interference thereby enhancing detection sensitivity of EDs for quantification. In this work, the use of dichloromethane as CI reagent for EDs is reported for the first time and could detect EDs to concentrations as low as 0.5 pg/mL. The recovery ranged from 74 to 112 % and the relative standard derivations for replicate analyses ranged from 5 to 17 %. We hope that this method will be applicable for routine analysis of EDs with hydroxyl functional groups.
    01/2004;
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    ABSTRACT: Supercritical water (SCW) as a highly destructive environment has been utilized to open multiwall carbon nanotubes (MWNTs) and to break silver aggregates into nanoparticles (diameter 2-20 nm). Water was drawn into open-ended MWNTs by capillary suction, pulling Ag nanoparticles into the MWNTs. The Ag nanoparticles (solid), presumably transported in the nanochannels of MWNTs by the fluidity of SCW, stacked, and fused to form nanorods, suggesting SCW associated with MWNTs (hollow interior) might be exploited as a nanoreactor.
    Chemical Communications 10/2003; · 6.38 Impact Factor
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    ABSTRACT: The analytical potential of furan as a chemical ionization (CI) reagent was evaluated for selectivity with nine monosubstituted naphthalene compounds. The ion-molecule reactions of furan and tetrahydrofuran (THF) were compared with those of methane, methanol and acetonitrile (prominently producing [M + H](+) ion base peaks) with naphthalene compounds in chemical ionization mass spectrometry (CI-MS). Reactions with furan predominantly show M(+) and [M + 39](+) ions. Based on this phenomenon, investigations were carried out for some of the molecular factors such as proton affinity, substituent effects and the preferred site of [C(3)H(3)](+) ion attachment that influence reactivity in furan CI. High selectivity with different substituents is observed in the formation of [M + 39](+) adduct ion, suggesting its usefulness as selective ionization reagent liquid. The selectivity and sensitivity are illustrated in the analysis of mixture of amino acids. Furthermore, the structure determination and reaction mechanism study is characterized by collision-activated dissociation experiments in CI-MS/MS and CI-MS/MS/MS.
    Journal of Mass Spectrometry 05/2003; 38(4):401-8. · 3.21 Impact Factor
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    ABSTRACT: Two types of electronic nose (EN), different in operational principle, were used to identify the source of spilled oil in an accident. The suspected sources considered were petroleum oil reservoirs and pipelines located near the site of the accident. Gas chromatography/mass spectrometry (GC/MS), operated in both EI and CI modes, was employed to confirm the identified source. The advantage of multisensors in spatially resolved sensing for direct multicomponent analysis was explored to minimize tedious sample preparation procedures. Subsequent principal component analysis helped in identifying the source. The advantage of fast separation in temporally resolved sensing was explored to rapidly yield compositional information; the resulting graphical representations helped clarify the source. Traditional GC/MS not only confirms the identified spilled oil source, but also provides detailed diagnostic information such as total petroleum hydrocarbons, polycyclic aromatic hydrocarbons and their C1-C4 alkylated homologues, as well as the n-alkanes, which are essential for follow-up remedial and regulatory actions. The main use of the electronic nose was demonstrated to be as a simple and rapid screening method for identifying a spilled oil source.
    Rapid Communications in Mass Spectrometry 02/2003; 17(16):1873-80. · 2.51 Impact Factor
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    ABSTRACT: The ion/molecule reactions of nine monosubstituted naphthalene compounds in chemical ionization mass spectrometry (CI-MS) were studied using tetrahydrofuran (THF) as CI reagent. Proton affinity factors, substituent effects and the preferred site of adduct ion attachment were examined. Good correlation was observed between proton affinity and the formation of [M](+*) and [M+H](+) ions. The influence of substituents on protonation and site-specific adduct [M+13](+) and [M+41](+) ion formation is also observed, with the cyano substituent showing the most stable [M+41](+) ion. Collision-activated dissociation experiments were used to characterize the variety of adducts formed under CI conditions, and provided insight into product ion structures and mechanisms of dissociation and condensation during CI-MS/MS.
    Rapid Communications in Mass Spectrometry 02/2003; 17(8):811-5. · 2.51 Impact Factor
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    ABSTRACT: Supercritical water (SCW) serves as a medium alone for fragmenting silver (Ag) aggregates and organizes the resulting Ag nanoparticles into chain-like nanowires and nanobanners. A variety of 1D and 2D nanostructured assemblies were formed from the nanoparticles by variations in pressure, temperature, and time. The size distribution of Ag nanoparticles is controllable in the range of 2–20 nm. Under appropriate conditions, the SCW medium allows the merging of Ag nanoparticles to form Ag nanowires with diameters of ∼60 nm, and nanobanners of triangle-shaped morphology with lengths of several hundred μm.
    Chemical Physics Letters 01/2003; · 2.15 Impact Factor
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    ABSTRACT: Supercritical water (SCW) in the presence and absence of oxygen is used for the first time for the opening and thinning of multiwall carbon nanotubes (MWNTs). The influence of variation of pressure, temperature, and time on the opening and thinning of MWNTs is examined. In SCW, opening and thinning of MWNTs is observed both in the presence and absence of oxygen. In addition, the presence of oxygen ($2 mmol) shows improved thinning of MWNTs with the collapsed outer graphene layers tending towards the inner layers. The morphology of MWNTs are critically analyzed using transmission electron micrographs (TEM) and Raman spectra. Ó 2002 Elsevier Science B.V. All rights reserved.
    Chemical Physics Letters 01/2002; 363(5). · 2.15 Impact Factor