We demonstrate the autonomous synthesis of iron (hydr)oxide (green rust, magnetite, and lepidocrocite) nanoparticles by precipitating iron(II) ions using hydroxide ions generated in situ with the methylene glycol-sulfite (MGS) reaction, a pH-clock. We show that the nature of the products can be predetermined by tuning the initial iron(II) concentration.
Keywords: clock reaction; formaldehyde; iron oxides; lepidocrocite; magnetite; materials programming; pH; self-assembly; sulfite; systems chemistry.