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Title: Single and multi-layered core-shell structures based on ZnO nanorods obtained by aerosol assisted chemical vapor deposition

Abstract

Core–shell nanorod structures were prepared by a sequential synthesis using an aerosol assisted chemical vapor deposition technique. Several samples consisting of ZnO nanorods were initially grown over TiO{sub 2} film-coated borosilicate glass substrates, following the synthesis conditions reported elsewhere. Later on, a uniform layer consisting of individual Al, Ni, Ti or Fe oxides was grown onto ZnO nanorod samples forming the so-called single MO{sub x}/ZnO nanorod core–shell structures, where MO{sub x} was the metal oxide shell. Additionally, a three-layer core–shell sample was developed by growing Fe, Ti and Fe oxides alternately, onto the ZnO nanorods. The microstructure of the core–shell materials was characterized by grazing incidence X-ray diffraction, scanning and transmission electron microscopy. Energy dispersive X-ray spectroscopy was employed to corroborate the formation of different metal oxides. X-ray diffraction outcomes for single core–shell structures showed solely the presence of ZnO as wurtzite and TiO{sub 2} as anatase. For the multi-layered shell sample, the existence of Fe{sub 2}O{sub 3} as hematite was also detected. Morphological observations suggested the existence of an outer material grown onto the nanorods and further microstructural analysis by HR-STEM confirmed the development of core–shell structures in all cases. These studies also showed that the individual Al, Fe,more » Ni and Ti oxide layers are amorphous; an observation that matched with X-ray diffraction analysis where no apparent extra oxides were detected. For the multi-layered sample, the development of a shell consisting of three different oxide layers onto the nanorods was found. Overall results showed that no alteration in the primary ZnO core was produced during the growth of the shells, indicating that the deposition technique used herein was and it is suitable for the synthesis of homogeneous and complex nanomaterials high in quality and purity. In addition, materials absorptance determined from the total transmittance and reflectance spectra revealed a broader absorption interval including visible light, indicating potential uses of these nanostructures on solar energy appliances. - Graphical abstract: Display Omitted - Highlights: • Uniform ZnO nanorods (core)–metal oxide (shell) were obtained sequentially by AACVD. • Shells were structured of homogeneous single or multi-layered non-mixed metal oxides. • ZnO nanorod core was preserved during the shell synthesis. • Optical absorptance revealed visible interval absorption for FeO{sub x} shell samples. • Materials can be suitable for photocatalytic or photovoltaic applications.« less

Authors:
; ; ; ; ;
Publication Date:
OSTI Identifier:
22476111
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 105; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
77 NANOSCIENCE AND NANOTECHNOLOGY; ABSORPTION; AEROSOLS; BOROSILICATE GLASS; CHEMICAL VAPOR DEPOSITION; FERRITES; HEMATITE; IRON OXIDES; MICROSTRUCTURE; NANOMATERIALS; NANOSTRUCTURES; PHOTOCATALYSIS; PHOTOVOLTAIC EFFECT; SOLAR ENERGY; SUBSTRATES; SYNTHESIS; TITANIUM OXIDES; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION; X-RAY SPECTROSCOPY; ZINC OXIDES

Citation Formats

Sáenz-Trevizo, A., Amézaga-Madrid, P., Pizá-Ruiz, P., Antúnez-Flores, W., Ornelas-Gutiérrez, C., and Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx. Single and multi-layered core-shell structures based on ZnO nanorods obtained by aerosol assisted chemical vapor deposition. United States: N. p., 2015. Web. doi:10.1016/J.MATCHAR.2015.04.020.
Sáenz-Trevizo, A., Amézaga-Madrid, P., Pizá-Ruiz, P., Antúnez-Flores, W., Ornelas-Gutiérrez, C., & Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx. Single and multi-layered core-shell structures based on ZnO nanorods obtained by aerosol assisted chemical vapor deposition. United States. doi:10.1016/J.MATCHAR.2015.04.020.
Sáenz-Trevizo, A., Amézaga-Madrid, P., Pizá-Ruiz, P., Antúnez-Flores, W., Ornelas-Gutiérrez, C., and Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx. 2015. "Single and multi-layered core-shell structures based on ZnO nanorods obtained by aerosol assisted chemical vapor deposition". United States. doi:10.1016/J.MATCHAR.2015.04.020.
@article{osti_22476111,
title = {Single and multi-layered core-shell structures based on ZnO nanorods obtained by aerosol assisted chemical vapor deposition},
author = {Sáenz-Trevizo, A. and Amézaga-Madrid, P. and Pizá-Ruiz, P. and Antúnez-Flores, W. and Ornelas-Gutiérrez, C. and Miki-Yoshida, M., E-mail: mario.miki@cimav.edu.mx},
abstractNote = {Core–shell nanorod structures were prepared by a sequential synthesis using an aerosol assisted chemical vapor deposition technique. Several samples consisting of ZnO nanorods were initially grown over TiO{sub 2} film-coated borosilicate glass substrates, following the synthesis conditions reported elsewhere. Later on, a uniform layer consisting of individual Al, Ni, Ti or Fe oxides was grown onto ZnO nanorod samples forming the so-called single MO{sub x}/ZnO nanorod core–shell structures, where MO{sub x} was the metal oxide shell. Additionally, a three-layer core–shell sample was developed by growing Fe, Ti and Fe oxides alternately, onto the ZnO nanorods. The microstructure of the core–shell materials was characterized by grazing incidence X-ray diffraction, scanning and transmission electron microscopy. Energy dispersive X-ray spectroscopy was employed to corroborate the formation of different metal oxides. X-ray diffraction outcomes for single core–shell structures showed solely the presence of ZnO as wurtzite and TiO{sub 2} as anatase. For the multi-layered shell sample, the existence of Fe{sub 2}O{sub 3} as hematite was also detected. Morphological observations suggested the existence of an outer material grown onto the nanorods and further microstructural analysis by HR-STEM confirmed the development of core–shell structures in all cases. These studies also showed that the individual Al, Fe, Ni and Ti oxide layers are amorphous; an observation that matched with X-ray diffraction analysis where no apparent extra oxides were detected. For the multi-layered sample, the development of a shell consisting of three different oxide layers onto the nanorods was found. Overall results showed that no alteration in the primary ZnO core was produced during the growth of the shells, indicating that the deposition technique used herein was and it is suitable for the synthesis of homogeneous and complex nanomaterials high in quality and purity. In addition, materials absorptance determined from the total transmittance and reflectance spectra revealed a broader absorption interval including visible light, indicating potential uses of these nanostructures on solar energy appliances. - Graphical abstract: Display Omitted - Highlights: • Uniform ZnO nanorods (core)–metal oxide (shell) were obtained sequentially by AACVD. • Shells were structured of homogeneous single or multi-layered non-mixed metal oxides. • ZnO nanorod core was preserved during the shell synthesis. • Optical absorptance revealed visible interval absorption for FeO{sub x} shell samples. • Materials can be suitable for photocatalytic or photovoltaic applications.},
doi = {10.1016/J.MATCHAR.2015.04.020},
journal = {Materials Characterization},
number = ,
volume = 105,
place = {United States},
year = 2015,
month = 7
}
  • ZnO nanorods were synthesized by aerosol assisted chemical vapor deposition onto TiO{sub 2} covered borosilicate glass substrates. Deposition parameters were optimized and kept constant. Solely the effect of different nozzle velocities on the growth of ZnO nanorods was evaluated in order to develop a dense and uniform structure. The crystalline structure was characterized by conventional X-ray diffraction in grazing incidence and Bragg–Brentano configurations. In addition, two-dimensional grazing incidence synchrotron radiation diffraction was employed to determine the preferred growth direction of the nanorods. Morphology and growth characteristics analyzed by electron microscopy were correlated with diffraction outcomes. Chemical composition was established bymore » X-ray photoelectron spectroscopy. X-ray diffraction results and X-ray photoelectron spectroscopy showed the presence of wurtzite ZnO and anatase TiO{sub 2} phases. Morphological changes noticed when the deposition velocity was lowered to the minimum, indicated the formation of relatively vertically oriented nanorods evenly distributed onto the TiO{sub 2} buffer film. By coupling two-dimensional X-ray diffraction and computational modeling with ANAELU it was proved that a successful texture determination was achieved and confirmed by scanning electron microscopy analysis. Texture analysis led to the conclusion of a preferred growth direction in [001] having a distribution width Ω = 20° ± 2°. - Highlights: • Uniform and pure single-crystal ZnO nanorods were obtained by AACVD technique. • Longitudinal and transversal axis parallel to the [001] and [110] directions, respectively. • Texture was determined by 2D synchrotron diffraction and electron microscopy analysis. • Nanorods have its [001] direction distributed close to the normal of the substrate. • Angular spread about the preferred orientation is 20° ± 2°.« less
  • SnO{sub 2} thin films were deposited by radio-frequency inductively coupled plasma-enhanced chemical vapor deposition. Postplasma treatments were used to modify the microstructure of the as-deposited SnO{sub 2} thin films. Uniform nanorods with dimension of null-set 7x100 nm were observed in the plasma-treated films. After plasma treatments, the optimal operating temperature of the plasma-treated SnO{sub 2} thin films decreased by 80 deg. C, while the gas sensitivity increased eightfold. The enhanced gas sensing properties of the plasma-treated SnO{sub 2} thin film were believed to result from the large surface-to-volume ratio of the nanorods' tiny grain size in the scale comparable tomore » the space-charge length and its unique microstructure of SnO{sub 2} nanorods rooted in SnO{sub 2} thin films.« less
  • Atmospheric pressure chemical vapor deposition (CVD) of Ag-Pd,Cu-Pd, and Ag-Cu alloys using aerosol precursor delivery over a range of preheating temperatures, 70-80{degrees}C and substrate temperatures, 250-300{degrees}C is described. The precursors were (hfac)Ag(SEt{sub 2}), (hfac)Cu{sup I}(1,5-COD), Cu(hfac){sub 2}, Pd(hfac){sub 2}, and Pd(hfac){sub 2}(SE5{sub 2}) dissolved in toluene with 10% H{sub 2} in Ar as carrier gas. The films were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction. The X-ray diffraction results showed the Ag PD films consisted of AgNO{sub 3} and volatile (hfac)Ag(SEt{sub 2}) as precursors to Ag films were consistent with a chemical vapor deposition (CVD)more » process. Reactivity studies between precursors and H{sub 2} suggested Pd(hfac){sub 2} is likely to undergo a small amount (<2%) of decomposition during the aerosol-assisted CVD experiments, and Pd(hfac){sub 2}(SEt{sub 2})/Pd(hfac){sub 2{minus}}(SEt{sub 2}) in different ratios in toluene solution. The films were characterized by X-ray diffraction and the results showed the composition of the films was dependent upon the solution stoichiometry. The possible rate-limiting steps are discussed, and it is proposed that the deposition rate is limited by the feed rate of the precursors to the reactor. These predictions were consistent with a study of deposition rate as a function of substrate temperature at constant feed rate in the (hfac)Ag(SEt{sub 2})/Pd(hfac){sub 2}(SEt{sub 2}) system, which showed no variation in the deposition rate over a 75{degrees}C temperature range. It was concluded that conditions of feed-rate or diffusion-rate limited deposition are useful approaches to control film composition. 42 refs., 12 figs., 1 tab.« less
  • Cited by 2
  • A simple and novel method, water-assisted chemical vapor deposition (CVD) was developed to functionalize multi-walled carbon nanotubes (MWCNTs) during the synthesis process. The functionalized MWCNTs were characterized using Raman spectroscopy, XPS, TGA, NH{sub 3}-TPD, SEM and HR-TEM. It was found that new defects are introduced and the amount of acidic groups is increased on the MWCNT surface during the water-assisted CVD process. The amount of C-OH and C-O group on the MWCNT surface is found to be increased from 21.1% to 42% with water vapor assistance. Density functional theory (DFT) was employed to study the chemical behavior of water vapormore » molecule on the catalyst particle surface of Ni(1 1 1) cluster. Based on the experimental and DFT simulation results, a mechanism for functionalization of MWCNTs by water-assisted CVD is proposed. - Graphical abstract: Water is adsorbed and activated on Ni surface, then dissociated into OH and O species, followed by part of OH and O species desorbed from the surface. Finally, the desorbed OH and O species oxidize the unsaturated carbon atoms of carbon nanotubes, form defects and oxygen-containing groups. Highlights: Black-Right-Pointing-Pointer MWCNTs were functionalized by water-assisted CVD method. Black-Right-Pointing-Pointer Defects and weak-medium acidic sites were created on the MWCNT sidewalls. Black-Right-Pointing-Pointer Oxygen-containing groups in functionalized MWCNT were increased from 21.1% to 42%. Black-Right-Pointing-Pointer A mechanism for the influence of water vapor on MWCNTs was proposed.« less