Silicon nanoparticles synthesised through reactive high-energy ball milling: enhancement of optical properties from the removal of iron impurities

Alkyl-terminated silicon nanoparticles (SiNPs) were prepared through reactive high-energy ball milling with contamination of iron from the steel milling materials. Iron impurities in the form of iron nanoparticles cause a decrease of photoluminescence intensity and an increase of the UV absorption. The iron impurities were removed either by gel permeation chromatography separation or by treatment with an aqueous HCl solution. The photoluminescence properties of the SiNPs were enhanced after the removal of iron. Transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and proton nuclear magnetic resonance were used to determine morphology, elemental composition and surface passivation of SiNPs.