Electrochromics of single crystalline WO3 · H2O nanorods

Single crystalline WO3 · H2O nanorods have been prepared using a facile solution route for the first time, in which PVA-124 is used as a structure-directing agent and glacial acetic acid as a stabilizer. The results prove that the x value in the fully reduced form of MxW6+(1−x)W5+xO3 is close to 1 for the rod-type WO3 · H2O nanocrystals instead of 0.7 for the platelet-type WO3 · H2O nanocrystals. The electrochromic performance of the rod-type WO3 · H2O nanocrystals is significantly improved in terms of fast response time and high contrast due to the plane with wider lattice spacing of d = 5.36 Å is parallel to the growth direction and faces towards the electrolyte.