Optical Property of Vanadium Oxide Nanotube Suspensions
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Optical Property of Vanadium Oxide Nanotube Suspensions L. Q. Mai1, W. Chen *, H. Yu, Y. Y. Qi, Y. Dai, J. F. Peng Institute of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070 Hubei, P. R. China 1 Key Laboratory of Silicate Materials Science and Engineering (WUT), Ministry of Education, Wuhan University of Technology, Wuhan 430070 Hubei, P. R. China ABSTRACT Vanadium oxide nanotube dispersions were investigated in water suspensions and characterized by TEM, absorption spectroscopy and optical limiting testing. The results show that the nanotubes are unrolled and oxidized after 6-day aging, resulting in some change of optical limiting property at the two wavelengths (532 and 1064 nm). The 1.27-eV absorption band is assigned as a superposition of both V d d and V4+ V5+ charge-transfer excitations, and the features at 2.9 eV are attributed to O 2p V 3d charge-transfer excitations.
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INTRODUCTION In recent years, nanoscale one-dimensional materials have attracted much attention due to their remarkable optic properties and their great potential for nanodevices [1, 2]. The vanadium oxide nanotubes (VONTs) are especially interesting since vanadium oxides are widely applied due to their outstanding structural versatility [3-5]. Further, as a transition metal, vanadium can exist in a variety of oxidation states and thereby allows for several possible stoichiometries of the nanotubes outer shell. Through this, if optical control of chemical reactivity in these materials could be achieved, exciting possibilities for optically addressed sensor applications would be realized. Recently, some studies have been devoted to investigate the optical properties of VONTs including optical absorption and infrared and Raman spectroscopy, optical limiting investigations, etc [6-10]. Despite these studies, there are no systematic reports in the literature of aging effects on the optical properties of a VONTs suspension. In this letter, we report the effects of aging on the structure and optical properties of the VONT by using TEM, absorption spectroscopy and optical limiting investigation. EXPERIMENTAL DETAILS The VOx nanotubes were prepared in a rheological phase reaction followed by self-assembling process. The preparation and characterization of these nanotubes have been described in detail in the literature [8, 11]. Briefly, 10 mmol V2O5 and 10 mmol hexadecylamine was mixed with 5 ml distilled water. After stirring for 1 hour, 15 ml distilled water was added to the orange solution. After aging for 48 hours, the resulting rheological suspension was transferred into a Teflon-lined autoclave with a stainless steel shell. The autoclave was kept at 180 for about a week. The final black product was washed with distilled water and dried at 80 for 8 h, resulting in a phase-pure product consisting of tubes only[11]. For optical
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* The corresponding author. E-mail: [email protected]
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measurements, these nanotubes were dispersed in distilled water using sodium dodecyl sulfate (S
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