Water-soluble PEGylated silicon nanoparticles and their assembly into swellable nanoparticle aggregates

Water-soluble silicon nanoparticles were synthesized by grafting PEG polymers onto functionalized silicon nanoparticles with distal alkyne or azide moieties. The surface-functionalized silicon nanoparticles were produced in one step from the reactive high-energy ball milling (RHEBM) of silicon wafers with a mixture of either 5-chloro-1-pentyne in 1-pentyne or 1,7 octadiyne in 1-hexyne to afford air and water-stable chloroalkyl or alkynyl-terminated nanoparticles, respectively. Nanoparticles with the xchloroalkyl substituents were easily converted to xazidoalkyl groups through the reaction of the Si nanoparticles with sodium azide in DMF. The azidoterminated nanoparticles were then grafted with mono-alkynyl-PEG polymers using a coppercatalyzed alkyne-azide cycloaddition (CuAAC) reaction to afford core–shell silicon nanoparticles with a covalently attached PEG shell. Covalently linked Si nanoparticle clusters were synthesized via the CuAAC ‘‘click’’ reaction of functional Si NPs with a,xfunctional PEG polymers of various lengths. Dynamic light scattering studies show that the flexible globular nanoparticle aggregates undergo a solvent-dependent change in volume (ethanol [ dichloromethane [ toluene) similar in behavior to hydrogel nanocomposites.