Rapid preparation of α-FeOOH and α-Fe2O3 nanostructures by microwave heating and their application in electrochemical sensors

• Simple microwave method leads to the rapid formation of the goethite and hematite.
• Homogenous nucleation and growth of particles are controlled by synthesis time.
• Modified electrode with α-FeOOH nanoplates improved the electrochemical response.
• The sample is directly heated by microwaves and its crystallization is accelerated.
• Fe3+ nanostructures are promising for development of electrochemical sensors.

α-FeOOH (goethite) and α-Fe2O3 (hematite) nanostructures have been successfully synthesized using the microwave-assisted hydrothermal (MAH) method and by the rapid burning in a microwave oven of the as-prepared goethite, respectively. The orthorhombic α-FeOOH to rhombohedralα-Fe2O3 structural transformation was observed by X-ray diffraction (XRD) and Raman spectroscopy results. Plates-like α-FeOOH prepared in 2 min and rounded and quasi-octahedral shaped α-Fe2O3 particles obtained in 10 min were observed using field emission gun scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The use of microwave heating allowed iron oxides to be prepared with shorter reaction times when compared to other synthesis methods. α-FeOOH nanoplates were incorporated into graphite-composite electrodes, which presented electrocatalytic properties towards the electrochemical oxidation of ascorbic acid in comparison with unmodified electrodes. This result demonstrates that such α-FeOOH nanostructures are very promising chemical modifiers for the development of improved electrochemical sensors.

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