Hematite (α-Fe2O3) films with a high quality surface morphology have been formed at the liquid–vapor interface using a novel approach. The surface morphology/size of the nanoparticles constituting the film is tuned in a controlled manner. It is observed that the concentration of polyvinyl alcohol in the precursor Fe3+/Fe2+ solution, the concentration of ammonia (NH3) vapor, and the annealing temperature are factors influencing the surface morphology/size of nanoparticles. The diameter of the α-Fe2O3 nanoparticles inside the film is controlled to be 2–15 nm by varying the synthesis conditions, and accordingly the films have roughness in the 1.34–6.8 nm range. The prepared α-Fe2O3 films are crystalline in nature and exhibit superparamagnetic behavior at room temperature.

A novel method for controlled synthesis of nanosized hematite (α-Fe 2 O 3 ) thin film on liquid–vapor interface

Monodispersed α–Fe2O3 nanoparticle aggregates with diameter ∼15 nm were successfully prepared by polyol process. The finite size effects in α–Fe2O3 nanoparticles were studied by X‐ray diffraction, transmission electron microscopy, diffuse reflectance spectroscopy and ac‐magnetic susceptibility. The optical band gap of α–Fe2O3 nanoparticles was significantly reduced compared to that of precursor. The α–Fe2O3 nanoparticles exhibited superparamagnetic behavior at room temperature, with blocking temperature TB = 100 K at 313 Hz and its value shifted to 124 K at 3.13 KHz. Analysis of ac‐magnetic susceptibility data gives a superparamagnetic relaxation time (τo) of 4×10−9 s.

M. S. Ramachandra Rao

Papers

Optical And Magnetic Properties Of Monodispersed α–Fe2O3 Nanoparticle Aggregates