ABSTRACT
Single-crystalline hexagonal alpha-Fe(2)O(3) nanorods/nanobelts have been created by a simple iron-water reaction in the low-temperature range of 350-450 degrees C. Scanning electron microscopy examination shows that the needle-like products, radiating from and perpendicular to the original large iron particle surfaces, are up to a few micrometers in length with an average diameter from 20 nm (tip) to 100 nm (base). X-ray photoelectron spectroscopy and FTIR spectroscopy reveal that the outermost surface of the nanorods consists of Fe(2)O(3) without organic impurity contaminants, which could possibly result from other methods, such as hydrothermal growth. Nanobelt-like structures are believed to result from a combination of increased reaction temperature and time. The initial formation and subsequent growth of alpha-Fe(2)O(3) nanorods may be explained by the iron metal corrosion mechanism.
Subject(s)
Crystallization/methods , Ferric Compounds/chemistry , Nanostructures/chemistry , Nanostructures/ultrastructure , Nanotechnology/methods , Water/chemistry , Macromolecular Substances/chemistry , Materials Testing , Molecular Conformation , Particle Size , Solutions , Surface PropertiesABSTRACT
WO(x) (2 < x < 3) and WS(2) nanostructures have been widely praised due to applications as catalysts, solid lubricants, field emitters, and optical components. Many methods have been developed to fabricate these nanomaterials; however, most attention was focused on the same dimensional transformation from WO(x) nanoparticles or nanorods to WS(2) nanoparticles or nanotubes. In a solid-vapor reaction, by simply controlling the quantity of water vapor and reaction temperature, we have realized the transformation from quasi-zero-dimensional WS(2) nanoparticles to one-dimensional W(18)O(49) nanorods, and subsequent sulfuration reactions have further converted these W(18)O(49) nanorods into WS(2) nanotubes. The reaction temperature, quantity of water vapor, and pretreatment of the WS(2) nanoparticle precursors are important process parameters for long, thin, and homogeneous W(18)O(49) nanorods growth. The morphologies, crystal structures, and circling transformation mechanisms of sulfide-oxide-sulfide are discussed, and the photoluminescence properties of the resulting nanorods are investigated using a Xe lamp under an excitation of 270 nm.
