Microemulsion-based synthesis of V1−xWxO2@SiO2 core–shell structures for smart window applications

Microemulsion technology was introduced to prepare V1−xWxO2@SiO2 core–shell nanostructures with various morphologies (nanorod, nanosphere, and their combination) by controlling the pH of the microemulsion. Flexible foils coated with the core–shell nanoparticles exhibited high optical performance with solar regulation efficiencies up to 12.55, 14.17, and 12.90% and fairly high visible transmittance of 53.20, 45.26 and 39.41 for 0 at%, 1 at%, and 2 at% of W-doped VO2 particles, respectively. The results suggested that the current foil was very suitable for application in smart windows. Interestingly, W doping did not deteriorate the solar regulation ability, which has not been reported before. The SiO2 shell played multifunctional roles because it can not only depress the aggregation and secondary growth of the nanoparticles during the process of annealing but also obviously enhance the thermal stability of V1−xWxO2. The amazing results provide significant progress in VO2-based thermochromic coating with a Mott phase transition temperature near room temperature and pave the way for practical application to smart windows.