Williamson ether synthesis: an efficient one-step route for surface modifications of silicon nanoparticles

A new synthetic route to mechanochemically produce silicon nanoparticles modified with biocompatible and chromophoric molecular compounds using the Williamson ether synthesis is described. This reaction allows a direct grafting of organic compounds such as phenol, hydroquinone and tetraethylene glycol to the silicon nanoparticle surface in an efficient fashion. Specifically, the formation of (phenoxy) hexyl silicon, (tetraethyleneglycoxy) hexyl silicon and (p-hydroxyphenoxy) hexyl silicon nanoparticles using the Williamson ether synthesis on chloroalkyl-terminated silicon nanoparticle is described. The resulting physical properties of the individual functionalised silicon nanoparticles were characterised by transmission electron microscopy, energy dispersive spectroscopy and photoluminescence, ultraviolet–visible, nuclear magnetic resonance and Fourier transformed infrared spectroscopies. The spectroscopic results show a direct bonding of the biocompatible and chromophoric molecules to the nanoparticles. Photoluminescence results show that the modified nanoparticles exhibit fluorescence in the blue spectral regions, consistent with other functionalised silicon nanoparticles formed by mechanochemistry, but that phenol and hydroquinone moieties result in silicon nanoparticles with broad, overlapping luminescence peaks, while the functionalisation with tetraethylene glycol has little effect on the overall optical properties.