Vertically Oriented Films of Layered Rare Earth Hydroxides Grown Directly on Flat and Tubular Substrates

Abstract Layered rare earth hydroxides (LRHs) have emerged as novel optical materials for various applications, but an effective method for orientation controlled growth of LRH films is not yet well established. Exfoliated nanosheets of LRHs are generally employed as building blocks for the construction of highly oriented films. In these cases, assembled LRH nanosheets tend to orient themselves parallel to the substrate surface. In the present work, direct growth of LRH sheets in a direction preferably perpendicular to flat glass and quartz tube substrates is successfully accomplished by adopting the chemical bath deposition technique. In particular, Tb³⁺‐doped layered yttrium hydroxide (LYH:Tb) films are grown under several different conditions to evaluate their effects on film growth. Both slide glass and a quartz tube coated with LYH:Tb film are further used as a replaceable adsorbent kit to detect and remove Cr(VI) ions utilizing the typical luminescence quenching of Tb³⁺ by the filter effect of adsorbed Cr(VI). Owing to high surface roughness caused by the microscale hierarchical architecture, the wettability of the LYH:Tb film can be also easily changed from superhydrophilic to superhydrophobic by a simple stearic acid treatment.