Molybdenum trioxide nanostructures prepared by thermal oxidization of molybdenum

doi:10.1016/j.jcrysgro.2006.07.004

Journal of Crystal Growth

Volume 294, Issue 2, 4 September 2006, Pages 304-308

https://doi.org/10.1016/j.jcrysgro.2006.07.004 Get rights and content

Abstract

Molybdenum trioxide (MoO₃) nanobelts and microballs were prepared by oxidization of molybdenum metal in an ambient atmosphere. Their lattice structures and morphologies were carefully studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The as-synthesized nanobelts and mircoballs are orthorhombic and monoclinic structured, respectively. The nanobelts are up to several hundred microns long, several hundred nanometers to several microns wide, with ratio of width to thickness between 5 and 10. HRTEM suggests the nanobelts grow along the [0 0 1] direction. The microballs are 3–10 μm in diameter. Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR) studies revealed the stretching vibration modes of Mo–O bonds as in α-MoO₃ nanobelts. The possible growth mechanism of the nanobelts was discussed.

Introduction

Quasi-one-dimensional (1D) nanostructures with different morphologies such as nanotubes, nanowires, and nanobelts have attracted more and more attention over the past decade due to their remarkable physical/chemical properties and wide range of applications [1], [2]. Interest in layered crystal MoO₃ has been growing in recent years for its multifaced functional properties. Its applications include catalyst in selective oxidation reactions [3], secondary batteries [4], information display systems [5], sensors [6], [7], lubricants [8], photochromic and electrochromic systems [9], [10], [11]. For these applications, large surface area has been found to be the efficient parameter. Compared with its bulk counterpart, a significantly large surface area and high aspect ratio could be expected in 1D nanostructures. A variety of techniques have been developed to control the morphologies of MoO₃, such as electrochemical method [12], solvothermal method [13], nanotubes template [14], acidification of ammonium heptamolybdate tetrahydrate [15], [16]. By passing a current through a spiral coil of molybdenum, Zhao et al. [17] prepared MoO₃ nanostructures. Li et al. [18] synthesized MoO₃ nanobelts through a solution method. Song et al. [19] have synthesized nanofibers and nanobelts with multilamellar mesostructured MoO₃ by a surfactant-templated hypothermal process. Although successful synthesis of 1D MoO₃ nanostructures has been realized in these strategies, the study on the synthesis of MoO₃ nanobelts based on thermal oxidation process is still limited. Our group has published some examples on the fabrication of oxide nanostructures by thermal oxidation of corresponding metals [20], [21]. In this work, we report a simple and effective technique of preparing MoO₃ nanostructures by direct oxidization a molybdenum wire in an ambient condition. In comparison with others, the method we introduced here is much cheaper, and convenient for large quantity production.

Section snippets

Experimental procedure

The fabrication of MoO₃ nanostructures was based on thermal oxidization of molybdenum metal in an ambient condition. In this experiment, a molybdenum wire (diameter 0.4 mm, length 3–5 cm) was placed in the center of a quartz tube (diameter 1 cm, length 50 cm). Both ends of the tube were open to the ambient atmosphere. After the tube furnace being raised to the pre-established temperature, the quartz tube was inserted into it for the oxidation reaction. Within several seconds, white product could be

Results and discussion

SEM is employed to describe the morphologies of the products. Fig. 1 shows SEM images of the samples prepared at 1150 °C. As shown in Fig. 1(a), the products away from the center are nanobelts with length up to several hundred microns, several hundred nanometers to several microns in width, and 5–10 in width-thickness ratio. Although some rod-like product can been detected (labeled by square in Fig. 1(b)), higher amplificatory SEM image (Fig. 1(c)) shows that it is still a nanobelt. Besides the

Conclusion

In summary, bulk quantities single-crystal orthorhombic structured MoO₃ nanobelts and some monoclinic structured MoO₃ microballs were prepared by direct oxidization of molybdenum metal in air. HRTEM suggests the nanobelts grow along the [0 0 1] direction. Raman and FTIR studies reveal the stretching vibration modes of Mo–O bonds in α-MoO₃ nanobelts. From the energy viewpoint, the possible growth mechanism was discussed. Because the molybdenum was mostly transformed into MoO₃ nanobelts, the method

Acknowledgements

This work was supported by the Natural Science Foundation of China (nos. 60577002 and 60390072), Natural Science Foundation of Jiangsu Province (BK2006111) and The National Key Project for Basic Research (2005CB623605).

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Molybdenum trioxide nanostructures prepared by thermal oxidization of molybdenum

Abstract

Introduction

Section snippets

Experimental procedure

Results and discussion

Conclusion

Acknowledgements

J. Non-Cryst. Solids

Appl. Surf. Sci.

J. Solid State Chem.

Solid State Ion.

Spectrochim. Acta A

J. Crystal Growth

Annu. Rev. Mater. Res.

J. Phys. C: Cond. Matter. Phys.

J. Am. Chem. Soc.

Chem. Mater.

Appl. Phys.

Chem. Mater.

Chem. Mater.

J. Phys. Chem. B