Novel VO2(M)–ZnO heterostructured dandelions with combined thermochromic and photocatalytic properties for application in smart coatings

Abstract

Hierarchical VO₂(M)–ZnO dandelions with ZnO nanorods grown radially on VO₂(M) nanoparticle cores have been successfully fabricated for the first time. In these dandelions, the VO₂(M) NPs were prepared by a TiO₂ seed-assisted hydrothermal method and the dandelion-like ZnO nanorods were formed over two steps: heteroseed-induced nucleation and the subsequent heteroepitaxial growth processes. The coupled ZnO could increase the chemical stability of VO₂(M) at relatively high temperatures. In addition, the VO₂(M)–ZnO composite film with decreased phase transition temperature (T_c = 62.6 °C) simultaneously displayed an enhanced visible transmission (T_vis-l = 52.2%) and solar modulating ability (ΔT_sol = 9.3%) as compared with the pure VO₂(M) film. Besides, the VO₂(M)–ZnO dandelions also exhibited improved photocatalytic performance, likely due to the synergistic effect of the VO₂(M)–ZnO heterojunction, unique dandelion-like hierarchical structure and high specific surface area. This is the first report of such a single VO₂(M)–ZnO dandelions structure with energy saving and environmental protection effects that offer significant potential for creating a multifunctional smart coating.