Use of NMR spectroscopy in the synthesis and characterization of air- and water-stable silicon nanoparticles from porous silicon

Air- and water-stable silicon nanocrystals were prepared by the bromine oxidation of porous silicon nanoparticles followed by reaction with n-butyllithium. Transmission electron microscopy suggests that the vigorous oxidation of porous silicon under reflux conditions removes the porous layer from the nanoparticle to expose a crystalline silicon core that can be passivated with organic ligands. A combination of infrared, ultraviolet/visible, and photoluminescence demonstrate the presence of small crystalline silicon particles and saturated hydrocarbon ligands, while solid- and liquid-state nuclear magnetic resonance spectroscopies establish that butyl ligands are localized on the nanocrystal surface. All of these analytical methods suggest that the product of this synthesis is stable in air and water indefinitely.