Available online 6 July 2011.
Molybdenum oxide nanowires have been found to show promise in a diverse range of applications, ranging from electronics to energy storage and micromechanics. This review focuses on recent research on molybdenum oxide nanowires: from synthesis and device assembly to fundamental properties. The synthesis of molybdenum oxide nanowires will be reviewed, followed by a discussion of recent progress on molybdenum oxide nanowire based devices and an examination of their properties. Finally, we conclude by considering future developments.
- Device assembly and properties
- Battery device assembly and Li storage performance
- Field emission devices
- Single nanowire devices and electrical transport
- Mechanical properties of single nanowires
The field of transition metal oxides represents an exciting and rapidly expanding research area that spans the border between the physical and engineering sciences, ,  and . Molybdenum oxides (MoOx) are one of the most attractive metal oxides due to their special structural characteristics. MoOx comprises two simple binary oxides, namely, MoO3 and MoO2. MoO3 has several polymorphs, such as the thermodynamically stable α-MoO3 (space group Pnma), metastable β-MoO3 (P21/c), -MoO3 (P21/m), and hexagonal metastable h-MoO3 (P63/m)5. MoO2, with its distorted rutile structure, is an unusual but interesting transition metal oxide because of its low metallic electrical resistivity (8.8 × 10−5Ω·cm at 300 K in bulk samples), high melting point, and high chemical stability6. MoO2 has been used as a catalyst for alkane isomerization, , ,  and , oxidation reactions12, and as a gas sensor13. It is also a promising anode material for Li-ion batteries14 N. Sharma et al., Chem Mater 16 (3) (2003), p. 504., , ,  and .
As nanotechnology has developed, nanostuctrues have received significant attention. Interesting physical phenomena appear as the scale of the building blocks approaches the nanoscale, such as the size effect, quantum conductance, and coulomb blockades. Nanowires are one of these building blocks that possess several distinct, practical properties, such as well-controlled dimensional composition, electronic radial transport, and crystallinity; this helps organize the nanoscale building blocks into assemblies and, ultimately, useful systems. Although research on molybdenum oxide (MoOx) nanowires started relatively late, MoOx nanowires are now showing potential for both fundamental research and applications in industry. MoOx nanowires represent attractive building blocks for active nanodevices. By controlling the growth and organization, they can be used to produce a number of novel, highly-efficient, robust, integrated nanoscale devices, including field emission devices (FED) and photodetectors.
Nanowires and nanorods are typically cylindrical, hexagonal, square, or triangular in cross-section. Nanobelts are typically rectangular in cross-section, with highly anisotropic dimensions. In this article, nanobelts and nanorods are regarded as special kinds of nanowire. Nowadays, the bottom-up technique is usually used for the assembly of MoOx nanowires and devices. A bottom-up design necessitates building with precisely controlled nanomaterial parameters (including chemical composition and structure), which determine the final performance of the device and . Fig. 1 shows the bottom-up procedure for MoOx nanowire device fabrication. To date, there has been no review that systematically summarizes the recent advances in MoOx nanowires from synthesis to devices and their properties. In this article, we focus on recent advances on MoOx nanowires based on our group's work.