5 results on '"Li, Lee"'
Search Results
2. Application of Raman Microscopy to Biodegradable Double-Walled Microspheres.
- Author
-
Widjaja, Effendi, Wei Li Lee, and Say Chye Joachim Loo
- Subjects
- *
RAMAN effect , *MICROSPHERES , *ENTROPY , *DICHLOROMETHANE , *PHTHALOCYANINES , *CALCITE , *SCANNING electron microscopy - Abstract
Raman mapping measurements were performed on the cross section of the ternary-phase biodegradable double-walled microsphere (DWMS) of poly(D,L-lactide-co-gly-colide) (50:50) (PLGA), poly(L-lactide) (PLLA), and polyfc-caprolactone) (PCL), which was fabricated by a one-step solvent evaporation method. The collected Raman spectra were subjected to a band-target entropy minimization (BTEM) algorithm in order to reconstruct the pure component spectra of the species observed in this sample. Seven pure component spectral estimates were recovered, and their spatial distributions within DWMS were determined. The first three spectral estimates were identified as PLLA, PLGA 50:50, and PCL, which were the main components in DWMS. The last four spectral estimates were identified as semicrystalline polyglycolic acid (PGA), dichloromethane (DCM), copper-phthalocyanine blue, and calcite, which were the minor components in DWMS. PGA was the decomposition product of PLGA. DCM was the solvent used in DWMS fabrication. Copper-phthalocyanine blue and calcite were the unexpected contaminants. The current result showed that combined Raman microscopy and BTEM analysis can provide a sensitive characterization tool to DWMS, as it can give more specific information on the chemical species present as well as the spatial distributions. This novel analytical method for microsphere characterization can serve as a complementary tool to other more established analytical techniques, such as scanningelectron microscopy and optical microscopy. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
3. Polymorphic Layered MoTe2 from Semiconductor, Topological Insulator, to Weyl Semimetal.
- Author
-
Raman Sankar, Rao, G. Narsinga, Muthuselvam, I. Panneer, Butler, Christopher, Kumar, Nitesh, Murugan, G. Senthil, Shekhar, Chandra, Tay-Rong Chang, Cheng-Yen Wen, Chun-Wei Chen, Wei-Li Lee, Lin, M.-T., Horng-Tay Jeng, Felser, Claudia, and Chou, F. C.
- Subjects
- *
POLYMORPHIC transformations , *SEMICONDUCTOR characterization , *TOPOLOGICAL insulators , *WEYL fermions , *X-ray diffraction - Abstract
Large size (~2 cm) single crystals of layered MoTe2 in both 2 H- and 1 T ′-types were synthsized using TeBr4 as the source of Br2 transport agent in chemical vapor transport growth. The crystal structures of the as-grown single crystals were fully characterized by X-ray diffraction, Raman spectroscopy, scanning transmission electron microscopy, scanning tunneling microscopy (STM), and electrical resistivity (ρ) measurements. The resistivity ρ( T ), magnetic susceptibility χ( T ), and heat capacity C p( T ) measurement results reveal a first order structural phase transition near ~240 K for 1 T ′-MoTe2, which has been identified to be the orthorhombic T d-phase of MoTe2 as a candidate of Weyl semimetal. The STM study revealed different local defect geometries found on the surface of 2H - and T d-types of MoTe6 units in trigonal prismatic and distorted octahedral coordination, respectively. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
4. Magnetic Orderings in Li2Cu(WO4)2 with Tungstate-Bridged Quasi-1D Spin-1/2 Chain.
- Author
-
Muthuselvam, I. Panneer, Sankar, Raman, Singh, Viveka Nand, Rao, G. Narsinga, Wei-Li Lee, Guang-Yu Guo, and Fang-Cheng Chou
- Subjects
- *
LITHIUM compounds , *ELECTRONIC structure , *MAGNETIC properties of metals , *ANTIFERROMAGNETISM , *TUNGSTATES , *SEMICONDUCTORS - Abstract
By both experimental measurements and theoretical calculations, we investigated the magnetic and electronic properties of Li2Cu(WO4)2 as a tungstate-bridged quasi-one-dimensional (1D) copper spin-(1/2) chain system. Interestingly, magnetic susceptibility χ(T) and specific heat measurements show that the system undergoes a three-dimensional antiferromagnetic (AF)-like ordering at TN ≈ 3.7 K, below a broad χ(T) maximum at ~8.9 K indicating a low-dimensional short-range AF spin correlation. Bonner-Fisher model fitting of χ(T) leads to an AF intrachain exchange constant of J/kB = 15.8 ± 0.1 K, and mean-field theory estimation gives an interchain coupling constant of J⊥/kB = 1.6 K, which supports the quasi-1D nature of this spin system. Theoretical evaluation of exchange coupling constants within the generalized gradient approximation (GGA) plus on-site Coulomb interaction (U) shows that the dominant AF exchange interaction is of ~13.9 K along the a-axis with weak interchain coupling, in agreement with the experimental result of a quasi-1D spin-(1/2) chain system. The GGA+U calculations also predict that Li2Cu(WO4)2 is a charge transfer-type AF semiconductor with a direct band gap of 1.5 eV. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
5. Two-Site Adsorption Model for the (√1b× √3)-R30° Dodecanethiolate Lattice on Au(111) Surfaces.
- Author
-
Xavier Torrelles, Carolina Vericat, María Elena Vela, Mariano H. Fonticelli, María Antonieta Daza Millone, Roberto Felici, Tien-Li Lee, Jorg Zegenhagen, Guadalupe Muñoz, José A. Martín-Gago, and Roberto C. Salvarezza
- Subjects
- *
ADSORPTION (Chemistry) , *SURFACE chemistry , *PROPERTIES of matter , *SCANNING tunneling microscopy - Abstract
The surface structure of dodecanethiolate self-assembled monolayers (SAMs) on Au(111) surfaces, formed from the liquid phase, have been studied by grazing incidence X-ray diffraction (GIXRD), scanning tunneling microscopy (STM), and electrochemical techniques. STM images show that the surface structure consists of (√1b× √3)-R30° domains with only a few domains of the c(4 × 2) lattice. The best fitting of GIXRD data for the (√1b× √3)-R30° lattice is obtained with alkanethiolate adsorption at the top sites, although good fittings are also obtained for the fcc and hcp hollow sites. On the basis of this observation, STM data, electrochemical measurements, and previously reported data, we propose a two-site model that implies the formation of incoherent domains of alkanethiolate molecules at top and fcc hollow sites. This model largely improves the fitting of the GIXRD data with respect to those observed for single adsorption sites and, also, for the other possible two-site combinations. The presence of alkanethiolate molecules adsorbed at the less favorable top sites could result from the adsorption pathway that involves an initial physisorption step which, for steric reasons, takes place at on top sites. Once the molecules are chemisorbed, the presence of energy barriers for alkanethiolate surface diffusion, arising mostly from chain−chain interactions, “freezes” some of them at the on top sites, hindering their movement toward fcc hollow sites. By considering the length of the hydrocarbon chain and the adsorption time, the two-site model could be a tool to explain most of the controversial results on this matter reported in the literature. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.