Low-temperature stability and high-temperature reactivity of iron-based core-shell nanoparticles.

Iron-based core-shell nanoparticles have been prepared that exhibit low-temperature stability and high-temperature reactivity toward oxygen in solution. The concentration of oxygen was determined from the fluorescence decay of pyrene. At low temperatures (<110 degrees C), the decays are short, indicating oxygen in solution. At higher temperatures (>110 degrees C), the decays become long and are consistent with no oxygen in solution. The change is abrupt, occurring over a narrow temperature range, and reproducible.