Recent advances in TiO2 nanotube layers – A mini review of the latest developments in nanotube preparation and applications in photocatalysis and microwave sensing

Abstract Self‐organized anodic TiO2 nanotube (TNT) layers prepared by anodization of Ti substrates have attracted great interest within the last 20 years, due to their unique properties and low‐cost synthesis. This mini review article aims to shortly summarize the most recent developments in the TNT layer synthesis and applications. It presents the synthesis of high aspect ratio (HAR) TNT layers in a short time by accelerating the TNT layer growth rates in lactic acid containing electrolytes. Furthermore, the etching of TNT layers towards TNT bundles of homogeneous size and single tube powders is discussed, as well as the possibility to grow TNT layers on non‐planar Ti substrates, which cannot be directly connected to the potentiostat (e.g., Ti spheres or 3D Ti meshes). As a relatively new application, the employment of TNT layers in microwave resonator sensors is introduced. Last, but not least, approaches of upscaling the TNT layer size from the laboratory scale towards significantly larger scale are outlined and reviewed.