Highly transparent polymethylsilsesquioxane xerogel monoliths with nanopores around 10 nm via ambient pressure drying: A potential host for nano-functional materials

Abstract

Silica aerogels are ideal templates for nanomaterial encapsulation due to high porosity and narrow pore size distribution (<10 nm) but suffer from poor mechanical strength. Polymethylsilsesquioxane (PMSQ) aerogels present better strength and transparency, yet their large pore size (10–30 nm) limits nanoparticle embedding. This study employed surface modification using hexamethyldisilazane (HMDZ) combined with ambient pressure drying (APD) to fabricate transparent, crack-free PMSQ xerogel monoliths featuring ∼10 nm nanopores, improved mechanical robustness and enhanced hydrophobicity. The effects of preparation conditions on the microstructure, transmittance, and thermal conductivity of the xerogels were systematically investigated. Furthermore, HMDZ-modified PMSQ xerogel monoliths were effectively utilized as mesoporous hosts for CsPbBr₃ quantum dots (QDs). The resulting CsPbBr₃ QDs@PMSQ composite monolith combined the high transparency, low density and hydrophobicity of PMSQ xerogels with the strong luminescence of QDs. The composites exhibited a PLQY of 37% along with outstanding moisture stability, photostability, and thermal stability. A white LED fabricated using the CsPbBr₃ QDs@PMSQ composite monolith, red K₂SiF₆: Mn⁴⁺ phosphors and a blue GaN chip exhibits bright emission with CIE coordinates of (0.23, 0.24), a luminous efficiency of 100 lm/W and approximately 132% coverage of the NTSC 1931 color gamut with outstanding long-term device stability. These results highlight the potential of HMDZ-modified PMSQ xerogel monoliths as promising mesoporous hosts for nano-functional materials, especially for stabilizing perovskite QDs in optoelectronic applications.