Preparation and photochromic properties of PEG-400 assisted WO3–TiO2–ZnO composite films

WO3–TiO2–ZnO composite films were successfully prepared on glass substrates via a sol–gel method using polyethylene glycol 400 (PEG-400) as an organic additive. The influence of PEG-400 on microstructure and photochromic properties of the composite films was studied by Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) and UV–vis–NIR spectrophotometer. The addition of PEG-400 could increase the amount of the adsorbed water in the WO3–TiO2–ZnO composite films, which plays a vital role in the photochromic process. SEM observation indicated that the aggregation of the particles in the films became serious when the addition amount of PEG-400 was above 0.5 g, for which a molecular ratio of WO3 and PEG-400 was 117:1. The photochromic property of the composite film firstly increased and then decreased with increasing amount of PEG-400. The WO3–TiO2–ZnO composite film with 0.5 g PEG-400 addition presented a best photochromism, which showed saturated photochromism in 60 s and bleached back to initial state in 10 h.