Iron phosphate nanostructures synthesized by microwave method and their applications in biosensing

A fast, simple microwave heating method has been developed for synthesizing iron phosphate (FePO4) nanostructures. The nanostructures were characterized and confirmed by transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), x-ray photoelectron spectroscopy (XPS), x-ray powder diffraction (XRD), Fourier transform infrared (FT-IR), and UV-vis spectroscopy. The morphology and the size of the nanomaterials are significantly influenced by the concentration of the precursors and the kinds of surfactants. The nanostructures have been employed as an electrode substrate to immobilize myoglobin (Mb) and to facilitate the direct electron transfer (DET) reaction of the protein. After being immobilized on the nanomaterials, Mb can keep its natural structure and undergo effective DET reaction with a pair of well-defined redox peaks at -(330 +/- 3.0) mV (pH 6.8) and an apparent electron transfer rate constant of 5.54 s(-1). The Mb-FePO4/GC electrode displays good features in the electrocatalytic reduction of H2O2, and thus can be used as a biosensor for detecting substrates with a low detection limit (5 +/- 1 mu M), a wide linear range (0.01-2.5 mM), a high sensitivity (ca. 85 +/- 3 mu A mM(-1) cm(-2)), as well as good stability and reproducibility. Therefore, FePO4 nanomaterials can become a simple and effective biosensing platform for the integration of proteins/enzymes and electrodes, which can provide analytical access to a large group of enzymes for a wide range of bioelectrochemical applications.