Non-templated hydrothermal growth of anisotropic magnetite nanostructures using hexamine as the directing agent

Anisotropic growth of magnetite (Fe ₃O ₄) nanoparticles is achieved in a hydrothermal growth process using hexamine to play a dual role of oxide forming and directing agent. The samples are characterized by X-ray diffraction, scanning electron microscopy, high resolution transmission electron microscopy, squid magnetometry, ferromagnetic resonance technique, diffuse reflectance spectroscopy and Mössbauer spectroscopy, which collectively establish the formation of Fe ₃O ₄ phase. Anisotropic structures such as nanorods and nanotubules are revealed and these are shown to exhibit good humidity sensing properties.