Hydrothermal Synthesis of Thermochromic VO2 for Energy-Efficient Windows

This chapter describes the hydrothermal synthesis of vanadium dioxide (VO₂) polymorphs and the thermochromic property of VO₂ with various nanostructures, like nanoparticles (NPs), nanowires, and nanosheets. The principle of hydrothermal synthesis involves a process of dissolution-supersaturation and subsequent crystallization in which the temperature, pressure, and time are the three most common parameters to be considered. The nanothermochromic concept was thus proposed to indicate VO₂ NPs in a dielectric host, which opens new avenues in energy-efficient fenestration. Hydrothermal synthesis will still play an important role in promoting the practical application of VO₂ nanostructured materials in smart windows for improving the human living environment, saving energy, and reducing greenhouse gases in the future. A one-step hydrothermal method is cost effective and facile to directly obtain VO₂(M/R), but it is still subjected to many limitations, including phase purity, high hydrothermal temperature, long reaction time, and less rich nanostructures.