Synthesis and characterization of plate-like VO2(M)@SiO2 nanoparticles and their application to smart window

• Rectangular and plate-like VO2(M)@SiO2 nanoparticles of ~10 nm thickness were formed.
• SiO2 shells over VO2(B) protect the nanoplates from aggregation after heat treatment.
• Nanopores in VO2(M)@SiO2 contribute to a higher optical performance.

Rectangular and plate-like VO2(M)@SiO2 nanoparticles were fabricated by a combination method of hydrothermal synthesis and post annealing process. Rectangular VO2(B) nanoplates of 20–30 nm in thickness were hydrothermally synthesized, and VO2(B)@SiO2 core–shell structure was formed using a modified Stober method. Protected by inert SiO2 shell, after post annealing the VO2(B)@SiO2 was transformed to VO2(M)@SiO2 without deteriorating its original plate-like morphology. Much interestingly, numerous nanopores were formed inside VO2(M)@SiO2 nanoparticles due to the difference in density between VO2(B) and VO2(M), which contributes to higher optical transmittance and thermal insulation. Thermochromic foils were fabricated using the core–shell nanoparticles, showing promising potential for smart window.