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

Abstract

An alkoxysilane derivative bearing a 10-vertex closodecaborate nanocluster (B 10 H 10 2−) was successfully synthesized and immobilized in a SiO 2 aerogel matrix. closo-Decaboratecontaining SiO 2 aerogels showed high specific surface (∼750 m 2 / g), open porosity (∼95%), and extremely low apparent density (80 mg/cm 3 ) as well as increased thermal stability of the closodecaborate 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.

Selective Functionalization of Carbonyl Closo-Decaborate [2-B10H9CO]− with Building Block Properties via Grignard Reagents

“…Recently, Yorov et al immobilized an alkoxysilane derivative bearing a 10-vertex closo -decaborate nanocluster in a silica (SiO 2 ) aerogel matrix. The silica nanomaterial loaded with 1.2 mol % closo -decaborate possessed high specific surface area (740 m 2 /g), low apparent density (80 mg/cm 3 ) and exhibited low toxicity towards normal cells and considerable cytotoxicity towards malignant glioblastoma cells [ 23 ]. The strategy was first introduced in 2014, where the authors reported the first-in-class borate-alkoxysilane derivatives via the functionalization of the carbonyl- and diazo-derivatives of closo -decaborate and validated the integrity/activity of the precursors to integrate into the matrix, pores and surfaces of silica-based nanomaterial (biologically compatible mesoporous silica and silica nanoparticles) as proof of concept [ 24 , 25 ].…”