ABSTRACT
A facile bottom-up method for the synthesis of lithium titanate nanoplates using a peroxo titanium complex ion precursor is reported. Instead of employing complicated treatment with high alkali concentration, the self-organization reaction between lithium and titanium ions in the prepared ion precursor can enable the formation of layered lithium titanate crystals (Li2-xHxTi2O5, where x = 0.1 and 1.52 for as-synthesise and acid-treated samples, respectively) under low alkaline conditions. We demonstrate that layered lithium titanate crystals can be grown anisotropically into individual nanoplates. Our work presents an easy and useful platform for the production of titanate materials with various morphologies based on the interaction with ionic species.
ABSTRACT
Ultrathin ZnS and ZnO films grown by atomic layer deposition (ALD) were employed as interfacial passivation layers (IPLs) for HfO2 films on InP substrates. The interfacial layer growth during the ALD of the HfO2 film was effectively suppressed by the IPLs, resulting in the decrease of electrical thickness, hysteresis, and interface state density. Compared with the ZnO IPL, the ZnS IPL was more effective in reducing the interface state density near the valence band edge. The leakage current density through the film was considerably lowered by the IPLs because the film crystallization was suppressed. Especially for the film with the ZnS IPL, the leakage current density in the low-voltage region was significantly lower than that observed for the film with the ZnO IPL, because the direct tunneling current was suppressed by the higher conduction band offset of ZnS with the InP substrate.
ABSTRACT
The optical properties of quantum dots (QDs) are altered by exposure to air and light; upon such exposure, the quantum yield is typically reduced. Improved understanding of surface oxidation and oxide-layer behavior, both of which influence the photoluminescence of QDs, is necessary for advancing the use of QDs. In this study, the oxide layer properties of QDs are investigated. The QDs are synthesized and subsequently oxidized by heat treatment in atmospheric conditions, and the luminescence properties of the resultant QDs are investigated. The emission properties of QDs are characterized by photoluminescence. The composition and bonding structure of oxidized CdSe QDs are investigated by X-ray photoelectron spectroscopy (XPS). The XRD peaks of oxidized CdSe QDs match CdSe and CdO peaks. CdO is formed by partial oxidation of CdSe QDs. Transmission electron microscopy (TEM) image is confirmed morphology of oxidation before and after of CdSe QDs.
ABSTRACT
Ultra-long NiFe2O4 nanofibers were synthesized by a simple electrospinning process followed by thermal treatment. The NiFe2O4 nanofibers are polycrystalline with average diameter of 218 nm and lengths up to several millimeters. When evaluated for their lithium-storage properties, the electrospun NiFe2O4 nanofibers exhibit a high specific capacity that can exceed 660 mA h g(-1) after 100 cycles, along with enhanced cycling stability.
Subject(s)
Electric Power Supplies , Electrodes , Ferric Compounds/chemistry , Lithium , Nanofibers , Nickel/chemistry , Microscopy, Electron, Scanning , Microscopy, Electron, TransmissionABSTRACT
To investigate the microstructural effects of the synthesized TiO2 nanopowders such as particle size, specific surface area, pore size and pore distributions for the application of an anode material of dye-sensitized solar cells (DSSC), size-controlled and well-dispersed TiO2 nanopowders were synthesized by chemical vapor condensation (CVC) process in the range of 800-1000 degreesC under a pressure of 50 mbar. The average particle size of synthesized TiO2 nanopowders was increased with increasing temperature from 13 nm for 800 degreesC, 15 nm for 900 degreesC and 26 nm. The specific surface area of synthesized nanoparticles were measured as 119.1 m2/g for 800 degreesC, 104.7 m2/g for 900 degreesC and 59.5 m2/g for 1000 degreesC, respectively. The conversion efficiency values (eta%) of DSSC with the synthesized TiO2 nanopowders at 800 degreesC, 900 degreesC, and 1000 degreesC were 2.59%, 5.96% and 3.66%, respectively. The highest conversion efficiency obtained in the 900 degreesC (5.96%) sample is thought to be attributable to homogeneous particle size and pore distributions, large specific surface area, and high transmittance in regions of dye absorption wavelength.
Subject(s)
Coloring Agents/chemistry , Electric Power Supplies , Nanostructures/chemistry , Nanostructures/ultrastructure , Solar Energy , Titanium/chemistry , Equipment Design , Equipment Failure Analysis , Gases/chemistry , Materials Testing , Particle Size , PowdersABSTRACT
An ultrathin silicon dioxide (SiO(2)) layer with 0.65-1.5 nm thickness has been formed by approximately 100% nitric acid (HNO(3)) vapor oxidation, and its electrical characteristics and physical properties are investigated. The oxidation kinetics follows a parabolic law except for the ultrathin (
