Nonaqueous synthesis, assembly and formation mechanisms of metal oxide nanocrystals
authors Niederberger, M; Garnweitner, G; Ba, JH; Polleux, J; Pinna, N
nationality International
journal INTERNATIONAL JOURNAL OF NANOTECHNOLOGY
author keywords assembly; nonaqueous synthesis; solvothermal synthesis; metal oxides; nanoparticles; formation mechanism
keywords SOL-GEL PROCESS; SOLUBLE MAGNETITE NANOCRYSTALS; LOW-TEMPERATURE SYNTHESIS; SIZE-CONTROLLED SYNTHESIS; CAPPED ZNO NANOCRYSTALS; IN2O3 THIN-FILMS; HIGHLY CRYSTALLINE; TIO2 NANOCRYSTALS; PHYSICOCHEMICAL PROPERTIES; GAMMA-FE2O3 NANOPARTICLES
abstract Nonaqueous solution routes to metal oxide nanoparticles are a valuable alternative to the well-known aqueous sol-gel processes, offering advantages such as high crystallinity at low temperatures, robust synthesis parameters and avoidance of surfactants in order to control the crystal growth. In the first part of this paper we give an over-view of the various solution routes to metal oxides in organic solvents, with a strong focus on surfactant-free processes developed in our group. In most of these synthesis approaches, the organic solvent plays the role of the reactant that provides the oxygen for the metal oxide, controls the crystal growth, influences particle shape and, in come cases, also determines the assembly behaviour. In general, these routes involve the reaction of metal oxide precursors such as metal halides, alkoxides, or acetylacetonates with benzyl alcohol, benzylamine or carbonyl compounds like ketones and aldehydes. Whereas the reaction between metal halides,and benzyl alcohol enables the direct synthesis of crystalline nanoparticles via simple beaker chemistry, the other reaction systems require a solvothermal treatment at temperatures between 200 degrees C and 250 degrees C. The metal halide-benzyl alcohol system additionally allows for an insitu functionalisation process, where the surface of the nanoparticles can be modified during nanoparticle synthesis in order to tailor the solubility as well as the assembly behaviour. This is an important step towards the use of metal oxides as nanobuilding blocks for the fabrication of structures like nanowires or mesoporous materials. In the second part, various reaction pathways to nanoparticle formation are discussed. Solvothermal processes are not easy to monitor insitu. In order to elucidate possible formation mechanisms, we analyse the reaction solution obtained after synthesis of the nanoparticles as well as after reference experiments with altered reaction conditions. The organic species found in the mixtures allow us to propose possible formation mechanisms. As an important example, we will discuss the formation mechanism of ceria nanoparticles synthesised from cerium(III) isopropoxide and benzyl alcohol, involving a C-C bond formation between the isopropoxy ligand and benzyl alcohol. This reaction pathway was also found to lead to the formation of BaTiO3 nanoparticles. The last part of this paper deals with possible applications of metal oxide nanoparticles, especially with regard to gas sensing devices.
publisher INDERSCIENCE ENTERPRISES LTD
issn 1475-7435
year published 2007
volume 4
issue 3
beginning page 263
ending page 281
digital object identifier (doi) 10.1504/IJNT.2007.013473
web of science category Nanoscience & Nanotechnology; Materials Science, Multidisciplinary
subject category Science & Technology - Other Topics; Materials Science
unique article identifier WOS:000247842700006
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journal analysis (jcr 2017):
journal impact factor 0.512
5 year journal impact factor 0.433
category normalized journal impact factor percentile 4.587
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