Photocatalytic TiO2 Nanorod Spheres and Arrays Compatible with Flexible Applications

In the present study, titanium dioxide nanostructures were synthesized through microwave irradiation. In a typical microwave synthesis, nanorod spheres in the powder form were simultaneously produced with nanorod arrays grown on polyethylene terephthalate (PET) substrates. The syntheses were performed in water or ethanol with limited temperature at 80 ◦C and 200 ◦C. A simple and low-cost approach was used for the arrays growth, which involved a PET substrate with a zinc oxide seed layer deposited by spin-coating. X-ray diffraction (XRD) and Raman spectroscopy revealed that synthesis in water result in a mixture of brookite and rutile phases, while using ethanol as solvent it was only observed the rutile phase. Scanning electron microscopy (SEM) showed that the synthesized spheres were in the micrometer range appearing as aggregates of fine nanorods. The arrays maintained the sphere nanorod aggregate structures and the synthesis totally covered the flexible substrates. Transmission electron microscopy (TEM) was used to identify the brookite structure. The optical band gaps of all materials have been determined from diffuse reflectance spectroscopy. Photocatalytic activity was assessed from rhodamine B degradation with remarkable degradability performance under ultraviolet (UV) radiation. Reusability experiments were carried out for the best photocatalyst, which also revealed notable photocatalytic activity under solar radiation. The present study is an interesting and competitive alternative for the photocatalysts existing nowadays, as it simultaneously results in highly photoactive powders and flexible materials produced with low-cost synthesis routes such as microwave irradiation.