Intrinsic structural/morphological and photochromic responses of WO3 co-doped MoO3 nanocomposites based on varied drying methods

A series of reversible photochromic nanocomposite materials based on WO3 co-doped MoO3 was prepared from deep eutectic solvent (DES) with water as co-solvent via a facile one-pot in-situ synthesis under ambient conditions. The nanocomposites were characterized by various techniques to ascertain the effect of different drying methods on the intrinsic morphology and photochromic responses of the materials. The FT-IR results show an interaction between the metal salts and DES. XRD patterns reveal monoclinic diffraction planes while TGA shows the thermal stability of the materials under all the drying methods at elevated temperatures. The SEM images reveal unevenly distributed and clustered prismatic-shaped crystallites which were confirmed with TEM. The vacuum-dried nanocomposite materials displayed an improved photochromic response with an instant visible color change from pale yellow to blue after 5 s of irradiation with UV-lamp, and further deepen after 300 s of irradiation. The reverse-bleaching process of the vacuum-dried nanocomposites was achieved under a dark condition in an oxygen environment for 90 min. The overall results show that drying methods may have an effect on the intrinsic morphology of nanocomposites but the vacuum drying method was the best, as the method reduces resistance to mass transfer with little or no effect on the microstructure in the material.