Figure 1. Single particle spectroscopy on iron nanoparticles.

(a) Schematic of the PEEM setup for in-situ single nanoparticle spectro-microscopy. (b) SEM image of iron nanoparticles of nine different sizes (from 6 to 80 nm in diameter) in a 4 × 4 μm² field-of-view fabricated using top-down nanofabrication with a height of 2.5 nm (scale bar 1 μm). (c) Elemental contrast image in the PEEM at Fe L₃ edge where each bright spot corresponds to an iron nanoparticle. (d) XAS spectra at Fe L₃ edge during different stages of annealing of a selected single 60 nm particle and obtaining pure iron by in-situ temperature-controlled reduction of surface oxide. (e) Evolution of XAS spectra of the 60 nm particle at different intervals of oxidation at 1 × 10⁻⁸ mbar. XAS spectra at Fe L₃ edge of four different particle sizes (6, 10, 40, 80 nm) after (f) annealing at 450 °C where all the spectra are similar and resemble that of metallic iron, (g) after 5 minutes of oxygen dosage at 1 × 10⁻⁸ mbar showing largest extend of oxidation of the smaller nanoparticle.