Harnessing the Aqueous Chemistry of Silicon: Self-Assembling Porous Silicon/Silica Microribbons.

The synthesis of microribbons based on the assembly of porous silicon nanoparticles (pSiNPs) in a silica matrix is reported. The formation of these structures is driven by dissolution and reprecipitation of silica derived from the NPs upon drying of an aqueous colloidal dispersion. The process generates composite films that fracture into filaments due to geometric stresses associated with drying of the film on a curved surface. By controlling NP concentration, solvent, and temperature during the evaporation process, well-defined microribbons with a rectangular cross section of ∼25 × 100 microns and lengths on the order of 1 cm are formed. Partial thermal oxidation of the ribbons generates luminescent Si-SiO2 core-shell composites, and complete oxidation generates porous SiO2 ribbons with retention of the mesoporous nanostructure. The pores can be infiltrated with daunorubicin as a model drug, and the resulting material shows sustained release of the chemotherapeutic for more than 70 days.