Stratum‐Confined Solid‐State Reaction (SC‐SSR) toward Colloidal Silicon‐Based Hollow Nanostructures for Bioapplications

Abstract Silicon nanostructures (SiNSs) can provide multifaceted bioapplications; but preserving their subhundred nm size during high‐temperature silica‐to‐silicon conversion is the major bottleneck. The SC‐SSR utilizes an interior metal‐silicide stratum space at a predetermined radial distance inside silica nanosphere to guide the magnesiothermic reduction reaction (MTR)‐mediated synthesis of hollow and porous SiNSs. In depth mechanistic study explores solid‐to‐hollow transformation encompassing predefined radial boundary through the participation of metal‐silicide species directing the in‐situ formed Si‐phase accumulation within the narrow stratum. Evolving thin‐porous Si‐shell remains well protected by the in‐situ segregated MgO emerging as a protective cast against the heat‐induced deformation and interparticle sintering. Retrieved hydrophilic SiNSs (<100 nm) can be conveniently processed in different biomedia as colloidal solutions and endocytosized inside cells as photoluminescence (PL)‐based bioimaging probes. Inside the cell, rattle‐like SiNSs encapsulated with Pd nanocrystals can function as biorthogonal nanoreactors to catalyze intracellular synthesis of probe molecules through C‐C cross coupling reaction.