Question

why does nanoparticles of iron is brown​

Answer 1

In addition to the above answer, Magnetite can get oxidized to maghemite. Magnetite is essentially a spinel FeO.Fe2O3, and the FeO part can get oxidized to form maghemite (overall crystal structure changes very little). This phase also has a reddish brown color. Powder XRD cannot distinguish between magnetite and maghemite (especially for nanoparticles). Maghemite is a distinct phase that is quite different from the very weakly magnetic heamatite (orange-red).

Pliss mark me brainliest.......