Preparation of VO2@SiO2 @TiO2 nanoparticles. First, the as-prepared VO2@SiO2 nanoparticlesweredispersedinanethanolsolutionunderstrongstirringfor30 min. Then,therequiredamount oftetrabutyl titanate(TBOT) wasquickly added.Finally, an ethanol solution containing 0.03 mL of NH3?H2O was added drop-wise to the solution over 5 min. The reaction was maintained at 45uC for 24 h. When the reaction was complete, the sample was collected by centrifugation, washed with deionised water and ethanol several times, and dried at 50uC for 6 h31. Please see the reference for further information on the preparation of VO2 nano- particles and VO2@SiO2 nanoparticles19.