Oxidation of Magnetite Nanoparticles. Brus, L E
abstract   bibtex   
The oxidation of magnetite to maghemite in aqueous solution has been studied using spectroscopy in the near IR. As the reaction progresses absorbance in the near IR region decreases proportionately. This reaction has been studied at various temperatures from 0°C to 80°C. Consistent with previous literature reports, a diffusion model best fits the observed rate of oxidation. This model predicts that the iron diffuses to the surface and is then oxidized. In this way, the concentration gradient necessary for diffusion is formed. The temperature dependence of the corresponding diffusion constant is described by an Arrhenius type equation with energy of activation of approximately 21.0 kcal/mole, which agrees well with literature reports in bulk at higher temperatures (170°C to 190°C). There is some debate as to whether UV light can help to catalyze the oxidation process. We have studied this effect using a 100mW multi-line 351/363 nm argon laser. The effect at 0°C is equivalent to a 7°C increase in temperature, which is not insignificant. However, it is still not significant enough to say that it is a photochemical process.
@article{brus_oxidation_nodate,
	title = {Oxidation of {Magnetite} {Nanoparticles}},
	abstract = {The oxidation of magnetite to maghemite in aqueous solution has been studied using spectroscopy in the near IR. As the reaction progresses absorbance in the near IR region decreases proportionately. This reaction has been studied at various temperatures from 0°C to 80°C. Consistent with previous literature reports, a diffusion model best fits the observed rate of oxidation. This model predicts that the iron diffuses to the surface and is then oxidized. In this way, the concentration gradient necessary for diffusion is formed. The temperature dependence of the corresponding diffusion constant is described by an Arrhenius type equation with energy of activation of approximately 21.0 kcal/mole, which agrees well with literature reports in bulk at higher temperatures (170°C to 190°C). There is some debate as to whether UV light can help to catalyze the oxidation process. We have studied this effect using a 100mW multi-line 351/363 nm argon laser. The effect at 0°C is equivalent to a 7°C increase in temperature, which is not insignificant. However, it is still not significant enough to say that it is a photochemical process.},
	language = {en},
	author = {Brus, L E},
	pages = {12},
}

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