Water under nano-confinement is different from normal water. It is relevant to life and geoscience because much of the hydration phenomenon in nature occurs in narrowly confined water. Studying confined water will help one to understand the physicochemical effect of water and its interaction with solutes in crowded environment. Mesoporous silica materials with uniform pore size will be the confining media in our study. By using neutron and X-ray scattering techniques, we studied the density and diffusion of water under nanoconfinement. By confining solutes, solubility of a hydrophobic molecule such as Xe in water under nanoconfinement will impact several related problems, (a) solubility of methane in water within nanopores of rock under fracking condition, (b) understanding how hydrophobic effect would be changed in confined water, (c) how protein hydration would change under confinement.
We studied hydration behavior of Xe in water confined in mesoporous silica using Xe-NMR chemical shifts. Temperature change of the signal allows us to determine the enthalpy of hydration. It was found that in pore confined water, the hydration of Xe is more energetically favorable than in bulk water. The increased solubility of Xe in nanopore is in the same trend with computer simulation results of confined methane.
Next, we employed mesoporous silica of matching pore sizes to confine lysozyme in order to mimic enzyme in a crowded environment. The stability and activity of lysozyme immobilized in mesoporous silica nanoparticle (MSN) of various pore sizes were studied and correlated to spectroscopic data of the immobilized enzyme. It was found that the activity of the lysozyme immobilized in the 5.6 nm mesopores of MSNs was higher than those of native enzymes. The enhanced activity was attributed to subtle change in hydration of lysozyme due to increased stability of hydrophobic solvation.
經歷：美國奧勒崗大學博士後研究(民64-66)、美國普渡大學博士後研究(民66-67)、臺灣大學化學系副教授(民67-71)、臺灣大學化學系教授 (民71-)、比利時布魯塞爾自由大學訪問學者(民72-73) 、台灣教育改革審議委員會委員(民82-84)、臺灣大學化學系主任(民93-96)、遠哲科學教育基金會董事(民87-100)、天下文化出版顧問(民 80-) 、國科會化學審議會學門召集人(民88-90)、奈米科技國家型計畫顧問(民91-96)、國家科學委員會副主任委員(民101-103)、國立台灣大學 講座教授(民103-)、中央研究院院士(民105)、亞洲太平洋催化聯盟主席(民105)。
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Transport Properties of Solids and
Computation methods including density-functional theory (DFT), tight-binding (TB) as well as effective bond-orbital model (EBOM), and k.p model for calculation of optical and transport properties of solids and nanostructures will be discussed. Transport properties of nanostructure junctions modeled by non-equilibrium Green function method will also be presented. Examples include optical excitations of solids and nanostructures including the electron-hole interaction obtained within symmetry-adapted basis, time-dependent DFT calculations of optical excitations of semiconductor alloys, and tunneling current spectra as well as thermoelectric characteristics of coupled-quantum dot junctions.
Yia-Chung Chang received his bachelor degree from National Cheng-KungUniversity, master degree and doctoral degree from California Institute of Technology. He joined the Physics Department, University of Illinois at Urbana-Champaign in 1980 as a visiting research assistant professor, and became an assistant professor in 1982, associate professor in 1986, and professor in 1991. In 2005, he joined Academia Sinica, Taiwan as a Distinguished Research Fellow and Director of the Research Center for Applied Sciences (RCAS). In 2012, he completed his two terms of directorship and remained as a Distinguished Research Fellow in RCAS. He is a fellow of American Physical Society and Academy of Nanoscience and Nanotechnology. He received the Distinguished Alumni Award of National Cheng-Kung University in 2009 and the Taiwan-France Science-technology Prize in 2015. He is a Thomson ISI highly cited scientist with nearly 10000 citations.
Dr. Yia-Chung Chang’s main research interests are in condensed matter theory, semiconductor electronics, photonic materials, and optoelectronic devices. In the last three decades he has worked on a series of related topics including shallow impurities and excitons in semiconductor superlattices and quatum wells, electronic and optical properties of semiconductors, surfaces and interfaces, and nanostructures, phonons and electron-phonon couplings in semiconductors and nanostructures, non-linear optical properties, many-body effects, exciton condensation, magnetic multilayers and giant magentoresistance, photonic crystals, optical metrology, detectors, lasers, quantum transport properties of nanostructures, spintronics, and quantum computing.
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