[B₁₀H₁₀]^2– Nanoclusters Covalently Immobilized to Hybrid SiO₂ Aerogels for Slow Neutron Shielding Applications

An alkoxysilane derivative bearing a 10-vertex closo-decaborate nanocluster (B10H102–) was successfully synthesized and immobilized in a SiO2 aerogel matrix. closo-Decaborate-containing SiO2 aerogels showed high specific surface (∼750 m2/g), open porosity (∼95%), and extremely low apparent density (80 mg/cm3) as well as increased thermal stability of the closo-decaborate moiety. Despite the low boron content (∼1.2 mol % of boron nanoclusters comprising natural mixture of boron isotopes), the aerogel nanomaterial demonstrated excellent neutron capture properties exceeding lightweight polymer-based analogues. Cell viability assessment indicated the pronounced dose-dependent toxicity of the borylated aerogel with respect to malignant cells (U251 MG glioblastoma line) and low toxicity with respect to normal cells (dental pump stem cells). The combination of the properties of closo-decaborate-modified silica aerogels makes them good candidate material for shielding of patients and healthcare personnel during boron neutron capture therapy procedures.