A Comprehensive Review of Substitutional Silicon-Doped C₆₀ Fullerenes and Their Endohedral/Exohedral Complexes:...

Silicon-doped C₆₀ fullerenes represent a distinctive class of heterofullerenes with tunable structural, electronic, and chemical properties arising from substitutional incorporation of Si atoms into the carbon cage. This review provides a comprehensive analysis of substitutional Si-C₆₀ systems and their endohedral and exohedral complexes, with emphasis on synthesis strategies, structural features, and theoretical investigations. Experimental methods, including laser vaporization and arc discharge of Si-containing graphite targets, have enabled the preparation of Si-doped fullerenes, although challenges remain in controlling the dopant number, position, and distribution. Computational studies, dominated by density functional theory and molecular dynamics simulations, elucidate the effects of Si substitution on cage geometry, HOMO-LUMO modulation, charge localization, aromaticity, and finite-temperature stability. Exohedral functionalization and endohedral encapsulation of Si-doped cages significantly enhance their potential for applications in sensing, catalysis, energy storage, and nanomedicine. Si incorporation consistently strengthens adsorption of small molecules, pharmaceuticals, biomolecules, and environmental pollutants, often transforming weak physisorption into strong chemisorption with pronounced electronic and spectroscopic changes. The synergistic insights from experimental and theoretical work establish Si-doped fullerenes as versatile, electronically responsive nanoplatforms, offering a balance between stability, tunability, and reactivity, and highlighting future opportunities for targeted synthesis and application-specific design.