Preparation of VO₂/Al-O core-shell structure with enhanced weathering resistance for smart window

VO₂/Al-O core-shell structure (V/AO) was synthesized by a facile method and its application for thermochromic film on smart window was investigated. Comparisons of thermochromic properties and stabilities in different environments between VO₂ and annealed V/AO nanoparticles were made. As a result, VO₂ nanoparticle was easily oxidized and lost thermochromic property. In contrast, with the protection provided by Al-O-based shell, the VO₂ core remained stable at a high temperature (350 °C in air) and in H₂O₂ solution. Especially, thermochromic films made by annealed V/AO nanoparticles almost kept thermochromic performance in damp heating environment (T=60 °C, RH=90%) for 20 days while VO₂ films lost their thermochromic properties after 3 days. Besides, the degradation progress of VO₂ and V/AO nanoparticles in damp heating environment was also explored. Results indicate that Al-O-based shell provides a good protection for the VO₂ core originated from the compact structure of shell, which effectively prevents oxygen and water from eroding VO₂. In summary, the VO₂ nanoparticles coated with Al-O-based shell exhibit a great potential in the application of smart window.