Synthesis of Submicron-Sized, Monodisperse Spherical V 2 O 5 Particles
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Synthesis of Submicron-Sized, Monodisperse Spherical V2O5 Particles S. Yamamoto, M. Takano and Y. Shimakawa Institute for Chemical Research, Kyoto University Uji, Kyoto 611-0011, Japan
ABSTRACT We have succeeded in preparing submicron-sized monodisperse spherical V2O5 particles by hydrolysis of vanadium isopropoxide (VO(OiPr)3) in acetone/pyridine (Py) mixture solution for the first time. These particles had almost perfect spherical shape and were non-agglomerated. Their size could be easily controlled from 200 to 800 nm by changing the concentration of pyridine while keeping narrow size distribution (standard deviation, ca. 7%). Elemental and Fourier Transform Infrared analyses revealed that these particles have a composition of V2O5 ·xPy ·yH2O (x ≈ 0.8, y ≈ 0.9) independent of their size. X-ray diffraction studies revealed that these particles have layered structure similar to that of V2O5·nH2O xerogel with an interlayer spacing of ca. 1.05 nm independent of their size, possibly due to the intercalation of H2O and pyridine between the V2O5 sheets.
INTRODUCTION Submicron-sized, monodisperse spherical metal oxide particles have been widely investigated due to their importance in many areas of science and technology, e.g., pigments, catalyst, raw materials of advanced ceramics, and opal-based photonic crystals [1,2]. A number of methods have been developed to prepare them [1,3-10]. Among these methods, hydrolysis of metal alkoxide in homogeneous solution is one of the most effective methods to prepare high purity spherical metal oxide particles with narrow size distribution. However, application of this method has been limited to relatively inactive metal alkoxides. Only a few examples have been reported, i.e., oxides of silicon [6], titanium [7], zirconium [8], and tantalum [9] and mixed oxides [10] of these metals. Hydrolyzing the other alkoxides usually results in the formation of gel or agglomerates. In this communication, we report the synthesis of submicron-sized monodisperse spherical V2O5 particles (VOP) with narrow size distribution via hydrolysis of a vanadium alkoxide in a homogenous solution for the first time. V2O5 has been extensively studied as an important material in many areas, e.g., catalysis [11], lithium ion battery [12], electrochromic
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device [13], sensors [14] and actuators [15]. Although the preparation of monodisperse spherical V2O5 particles may be highly appreciated in such areas, no methods have been developed so far. Hydrolysis of vanadium alkoxides in homogeneous solution has been reported to form only V2O5·nH2O xerogel for their high reactivity [16]. In our method, monodisperse spherical VOP with various sizes can be prepared by simply hydrolyzing vanadium isopropoxide (VO(OiPr)3) in acetone/pyridine (Py) mixture solution under air.
EXPERIMENTAL DETAILS Monodisperse spherical VOP were prepared by adding VO(OiPr)3 (0.06 ml, donated by Nichia Co. Ltd.) to acetone/pyridine mixture solutions (total weight 8 g) with vigorous stirring under air at around 20 oC. Almost s
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