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.