Synthesis and electrocatalytic activity of haemin-functionalised iron(II, III) oxide nanoparticles.

Haemin-functionalised magnetic iron(II, III) oxide (Fe3O4) nanoparticles (Fe3O4/haemin) were synthesised by changing the acidity of a solution of the two compounds. The nanoparticles were characterised by transmission electron microscopy, UV-vis absorption spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, measurement of magnetisation, and electrochemical techniques. The properties of both haemin and Fe3O4 were retained. Thus, Fe3O4/haemin nanoparticles exhibited pronounced electrocatalytic activity towards trichloroacetic acid (TCA) like haemin itself. Interestingly, electrocatalytic activity towards TCA was affected by detection temperature, which was controlled via electrically heated carbon paste electrodes. The maximal catalytic current was 5.8 times higher at 60°C than at room temperature (25°C). This proposed electrochemical sensor for TCA possessed a linear detection range of 5-80 μM and a detection limit of 0.3 μM at 60°C.