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Received: April 17, 2018; Revised: May 29, 2018; Accepted: May 30, 2018
Abstract: The aim of this work is the attainment of the TiO2-nanotube photocatalytic-growth condition using anodization, whereby the NH4F–H2O weight ratio is appropriately controlled. We fabricated the TiO2 nanotubes using a two-step anodization (first step is 1 hr; second step is 30 hr) under the ambient pressure and the room temperature at 60 V in ethylene-glycol solutions to investigate the effects of the NH4F(0.1,0.3,0.5wt%) and H2O(1–3wt%) on the TiO2-nanotube geometry and the photocatalytic efficiency. Further, the decomposition efficiency of the methylene blue on the TiO2 nanotubes by the UN radiation depended on the geometrical change of the nanotube geometry, indicating the proportionality of the decomposition efficiency to the surface area that was affected by the NH4F and H2O concentrations. As the NH4F weight was increased, the surface area initially decreased but slightly increased later, and the length consistently increased. As the H2O weight was increased, the surface area and length initially increased, but later decreased with the 3 wt% H2O.