Cathodoluminescence study of ZnO bulk and nanostructures

Thesis (Ph. D. in Engineering)--University of Tsukuba, (A), no. 5306, 2010.3.25Includes bibliographical reference

Preparation of nitrogen doped zinc oxide nanoparticles and thin films by colloidal route and low temperature nitridation process

International audienceNitrogen doped zinc oxide (ZnO) nanoparticles have been synthesized using a colloidal route and low temperature nitridation process. Based on these results, 200 nm thick transparent ZnO thin films have been prepared by dip-coating on SiO2 substrate from a ZnO colloidal solution. Zinc peroxide (ZnO2) thin film was then obtained after the chemical conversion of a ZnO colloidal thin film by H2O2 solution. Finally, a nitrogen doped ZnO nanocrystalline thin film (ZnO:N) was obtained by ammonolysis at 250°C. All the films have been characterized by scanning electron microscopy, X-ray diffraction, X-Ray photoelectron spectroscopy and UV-Visible transmittance spectroscopy

Fabrication of Octahedral Tantalum Cluster Film by Electrophoretic Deposition

The octahedral Ta6Br14.8H2O cluster, one of the [M6Li12La6]n- octahedrons (M= Nb, Ta; Li= halogen, La= halogen or chalcogen), exhibits interesting oxido-reduction properties in solution1. The application of the [Ta6Bri12]2+ cores has been potentially studied in biotechnologies2, optical devices3, photovoltaic cells4 and catalysis5. Originating from the expectation to block the UV and NIR light on low-emissivity window, the Ta6Br14.8H2O cluster thin film on ITO glass has been fabricated by electrophoretic deposition (EPD) process, a fairly rapid and low cost two-step process well-known for ceramic shaping, conductive surface coating and easily scalable to industrial level. The interesting characteristic has been recognized that the green [Ta6Bri12]2+ cores (adsorbing Ultra-Visible range) easily transfers to brown [Ta6Bri12]3+/4+ cores (absorbing near-infrared range) when dissolved in different solvents. Therefore, selecting the medium and optimizing the concentration of water in solvent to obtain the green homogeneous suspension with high dissolution is the main purpose of study. Considering the green color and transmittance of solution, as well as FE-SEM surface morphology of the green film, 0.02 mL H2O per mL acetone was selected as the optimal ratio to obtain the green transparent suspension and possibility to fabricate the green film by EPD process. However, the [Ta6Bri12]2+ green film has been essentially incorporated with poly vinyl pyrrolidone (PVP) in order to improve the dispersion of Ta6Br14.8H2O clusters inside the suspension and effectively prevent the performance of new [Ta6Bri12]3+/4+ clusters (brown-color) by oxidizing reactions. Reference [1] A. Vogler et al., Inorg. Chem., 1983, 23 (10), 1360. [2] J. Knablein et al., J. Mol. Biol., 1997, 270, 1. [3] S. Cordier et al., J. Inorg. Organomet. Polym., 2015, 25, 189. [4] A. Renaud et al., Chemistry Select., 2016, 1, 2284. [5] A. Barras et al., Appl. Catal. B: Environ., 2012, 123,

SYNTHESIS AND CHARACTERIZATION OF NANOCOMPOSITES COATING BASED ON INORGANIC OCTAHEDRAL CLUSTER UNITS FABRICATED BY ELECTROPHORETIC DEPOSITION PROCESS

Composite nanoarchitectures represent a new class of nanostructured entities that integrate various dissimilar nanoscale building blocks including clusters, particles, wires and films [1]. The heterogeneous composite nanostructured materials are composed by definition of multi-(nano)components, each tailored to address different requirements. As one of the nanocomponents, nanometer sized transition metal clusters (\u3c2 nm), which consist of less than a few dozens of metal atoms, could be defined as a link between atom and nanoparticle [2-7]. In this presentation, the first preparation of functional thin films based on octahedral molybdenum metal clusters deposited on ITO glass substrate by EPD will be discussed in detail [8]. More generally, we will focus on our recent results on thin films for optical and energy applications [9-10]. References [1] R. Liu et al., Chem. Commun., 2011, 47, 1384 [2] F. A. Cotton, Inorg. Chem., 1964, 3, 1217 [3] A. Perrin et al., C. R. Chimie, 2012, 15, 815 [4] Y. Luab et al., Chem. Soc. Rev., 2012, 41, 3594 [5] V. Fedorov, J. Clust. Sci., 2015, 26, 3 [6] S. Cordier et al., J. Inorg. Organomet. Polym., 2015, 25 189 [7] F. Grasset et al., Adv. Mater., 2008, 20, 1710 [8] T.K.N Nguyen et al., ECS J. Solid State Sci. Technol., 2016, (10) R178-R186 [9] T. G. Truong et al., Sci. Technol. Adv. Mat., 2016, 17(1), 443 [10] A. Renaud et al., ChemistrySelect, 2016, 1, 228

Effect of Size-Dependent Thermal Instability on Synthesis of Zn2 SiO4-SiOx Core–Shell Nanotube Arrays and Their Cathodoluminescence Properties

Vertically aligned Zn2SiO4-SiOx(x < 2) core–shell nanotube arrays consisting of Zn2SiO4-nanoparticle chains encapsulated into SiOx nanotubes and SiOx-coated Zn2SiO4 coaxial nanotubes were synthesized via one-step thermal annealing process using ZnO nanowire (ZNW) arrays as templates. The appearance of different nanotube morphologies was due to size-dependent thermal instability and specific melting of ZNWs. With an increase in ZNW diameter, the formation mechanism changed from decomposition of “etching” to Rayleigh instability and then to Kirkendall effect, consequently resulting in polycrystalline Zn2SiO4-SiOx coaxial nanotubes, single-crystalline Zn2SiO4-nanoparticle-chain-embedded SiOx nanotubes, and single-crystalline Zn2SiO4-SiOx coaxial nanotubes. The difference in spatially resolved optical properties related to a particular morphology was efficiently documented by means of cathodoluminescence (CL) spectroscopy using a middle-ultraviolet emission at 310 nm from the Zn2SiO4 phase