Magnetite FesO

Fe/HjO system Figure 1.15 (top) is a simplified version of the Fe-H O potential-pH equilibrium diagram [the region of stability of magnetite (FesO ) is not included] and it is instructive to consider some of the more important equilibria involved ... 

Zhao et al. prepared magnetite (FesO nanoparticles modified with electroactive Prussian Blue [44]. These modified NPs were drop-cast onto glassy-carbon electrodes. They observed the redox processes commonly observed for PB (similar to that seen in Figure 4.8), and also demonstrated that the Prussian White material produced by PB reduction at 0.2 V served as an electrocatalyst for Fi202 reduction. They also prepared LbL films in which PB NPs and glucose oxidase were alternated between PD DA layers [99]. These were demonstrated to act as electrocatalysts for Fi202 reduction. Based on the ability to sense the product of the enzymatic reaction, these structures were shown to act as glucose sensors. 

Elementary iron is difficult to isolate because it combines most readily with oxygen. Iron implements therefore rust easily, forming an iron oxide. And it is not surprising to find that the most plentiful iron ores are oxides such as hematite (FesOs), with two atoms of iron and three of oxygen in each molecule, or magnetite (FesO ). 

The Ores of Iron. The chief ores of iron are its oxides hematite. Fe- Og, and magnetite, Fe O, and its carbonate side rite, FeCO.,. The hydrated ferric oxides such as limonite are also important. The sulfide pyrite, FeSo, is used as a source of sulfur dioxide, but the impure iron oxide left from its roasting is not satisfactory for smelting iron, because the remaining sulfur is a troublesome impurity. 

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