Browsing by Author "Suranan Anantachaisilp"

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    Chemical and structural investigation of lipid nanoparticles: Drug-lipid interaction and molecular distribution
    (2010-03-19) Suranan Anantachaisilp; Siwaporn Meejoo Smith; Alongkot Treetong; Sirapat Pratontep; Satit Puttipipatkhachorn; Uracha Rungsardthong Ruktanonchai; Mahidol University; Thailand National Science and Technology Development Agency; King Mongkut's Institute of Technology Ladkrabang
    Lipid nanoparticles are a promising alternative to existing carriers in chemical or drug delivery systems. A key challenge is to determine how chemicals are incorporated and distributed inside nanoparticles, which assists in controlling chemical retention and release characteristics. This study reports the chemical and structural investigation of γ-oryzanol loading inside a model lipid nanoparticle drug delivery system composed of cetyl palmitate as solid lipid and Miglyol 8121as liquid lipid. The lipid nanoparticles were prepared by high pressure homogenization at varying liquid lipid content, in comparison with the γ-oryzanol free systems. The size of the lipid nanoparticles, as measured by the photon correlation spectroscopy, was found to decrease with increased liquid lipid content from 200 to 160nm. High-resolution proton nuclear magnetic resonance (1H-NMR) measurements of the medium chain triglyceride of the liquid lipid has confirmed successful incorporation of the liquid lipid in the lipid nanoparticles. Differential scanning calorimetric and powder x-ray diffraction measurements provide complementary results to the1H-NMR, whereby the crystallinity of the lipid nanoparticles diminishes with an increase in the liquid lipid content. For the distribution of γ-oryzanol inside the lipid nanoparticles, the1H-NMR revealed that the chemical shifts of the liquid lipid in γ-oryzanol loaded systems were found at rather higher field than those in γ-oryzanol free systems, suggesting incorporation of γ-oryzanol in the liquid lipid. In addition, the phase-separated structure was observed by atomic force microscopy for lipid nanoparticles with 0% liquid lipid, but not for lipid nanoparticles with 5 and 10% liquid lipid. Raman spectroscopic and mapping measurements further revealed preferential incorporation of γ-oryzanol in the liquid part rather than the solid part of in the lipid nanoparticles. Simple models representing the distribution of γ-oryzanol and lipids (solid and liquid) inside the lipid nanoparticle systems are proposed. © 2010 IOP Publishing Ltd.
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    Nature of red luminescence in oxygen treated hydrothermally grown zinc oxide nanorods
    (2015-08-11) Suranan Anantachaisilp; Siwaporn Meejoo Smith; Cuong Ton-That; Soraya Pornsuwan; Anthony R. Moon; Christian Nenstiel; Axel Hoffmann; Matthew R. Phillips; University of Technology Sydney; Mahidol University; Technical University of Berlin
    © 2015 Published by Elsevier B.V. A strong broad red luminescence (RL) peak centered at 1.69 eV (FWHM=0.57 eV) at 15 K [1.78 eV (FWHM=0.69 eV) at 300 K] is formed in ZnO nanorods hydrothermally grown at low temperature following thermal annealing at 650 °C for 30 min in an O2 gas environment. The optical properties of this peak were comprehensively studied using a range of characterization techniques, including photoluminescence and cathodoluminescence spectroscopy, X-ray absorption near edge spectroscopy and electron paramagnetic resonance spectroscopy. With decreasing temperature the RL peak position red shifted and its FWHM became narrower in accordance with the configuration coordinate model. Using these results, the RL has been assigned to highly lattice coupled VZn-related acceptor-like centers. No correlation was found between the observed red luminescence and nitrogen impurities.
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    Tailoring deep level surface defects in ZnO nanorods for high sensitivity ammonia gas sensing
    (2014-01-01) Suranan Anantachaisilp; Siwaporn Meejoo Smith; Cuong Ton-That; Tanakorn Osotchan; Anthony R. Moon; Matthew R. Phillips; University of Technology Sydney; Mahidol University
    © 2014 American Chemical Society. The influence of deep level surface defects on electrical and gas sensing properties of ZnO nanorods NH3(g) sensors was studied. ZnO nanorods 50-60 nm in diameter were synthesized via low-temperature hydrothermal growth at 90°C on sapphire substrates. The as-grown nanorods exhibited a cathodoluminescence (CL) peak centered at 1.90 eV (YL), attributed to LiZndeep acceptors or O interstitials. Subsequent annealing in O2at 1 atm and Zn vapor at 650°C produced broad CL peaks centered at 1.70 eV (RL) and 2.44 eV (GL), respectively. The RL and GL have been ascribed to acceptor-like VZnand donor-like VOrelated centers, respectively. Electrical and gas sensing measurements established that the NH3gas response sensitivity was 22.6 for O2anneal (RL), 1.4 for Zn vapor anneal (GL), and 4.1 for the as-grown (YL) samples. Additionally, treatment in H-plasma quenched the RL and inverted the NH3electrical response due to the incorporation of H donors. Changes in the gas sensing response are explained by a shift in the position of the ZnO Fermi level relative to the chemical potential of NH3gas due to the creation of near surface donor or acceptors. These data confirm that ZnO nanorods arrays can be tailored to detect specific gas species. (Chemical Equation Presented).