IP: 95.181.177.34 On: Sun, 21 Apr 2019 04:17:32 Copyright: American Scientific Publishers Delivered by Ingenta Copyright © 2019 American Scientific Publishers All rights reserved Printed in the United States of America Article Journal of Nanoscience and Nanotechnology Vol. 19, 5211–5219, 2019 www.aspbs.com/jnn Synthesis of Ruthenium-Doped TiO 2 Nanotube Arrays for the Photocatalytic Degradation of Terasil Blue Dye A. Sandoval González 1 , J. C. Solis-Cortazar 2 , C. A. Pineda-Arellano 3 , E. Ramírez-Morales 2 , A. Espinosa de los Monteros 2 , and S. Silva-Martínez 1 2 ∗ 1 Centro de Investigación en Ingeniería y Ciencias Aplicadas, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, Col. Chamilpa, Cuernavaca, Morelos C.P. 62209, México 2 Universidad Juárez Autónoma de Tabasco, Avenida Universidad S/N, Col. Magisterial, C.P: 86040, Villahermosa, Tabasco, México 3 CONACYT-Centro de Investigaciones en Óptica A.C. Prol. Constitución 607, Fracc. Reserva Loma Bonita. Aguascalientes, Aguascalientes, Código Postal 20200, México The oxidation of terasil blue dye (TB) has been achieved by photocatalysis under UV light using well organized nanotubes of Ti/TiO 2 doped with ruthenium (Ru/Ti/TiO 2 . Ru/Ti/TiO 2 were fabricated by Ti anodization followed by impregnation with 0.04, 0.08 and 0.16 wt% of RuCl 3 · x H 2 O or KRuO 4 as precursor salts. Ti foil anodization was carried out in non-aqueous solutions and in aqueous solutions at pH 7 and pH 12.6. Scanning electron microscopy analyses revealed a morphology of well-defined, organized nanotubes of Ti/TiO 2 and Ru/Ti/TiO 2 . The ruthenium was evenly distributed over Ti/TiO 2 surface. Cluster formation was also observed for 0.16 wt% Ru loading. The X-ray diffraction spectra showed anatase and rutile phase in pure Ti/TiO 2 and Ru/Ti/TiO 2 nanotubes. Therefore, ruthenium doping did not modify the crystalline phase of Ti/TiO 2 . Raman spectra did not reveal the rutile phase of TiO 2 in the composites which is attributed to the laser characteristics used. The optical band gap energies of the Ti/TiO 2 and Ru/Ti/TiO 2 nanotube arrays showed that ruthenium-doping on Ti/TiO 2 had slight effect on the band-gap energy. A decrease in the band gap energy of pure Ti/TiO 2 (E g = 2.88 eV) was observed by Ru loading of 0.04 wt% in the Ti/TiO 2 nano- tube arrays (E g = 2.60 eV). The kinetic rate constant of the photocatalytic oxidation of TB, using 0.08 wt% Ru load, was 1.56 and 1.39 times of that on Ti/TiO 2 composite (0.01 min -1  synthetized at pH 12.6 impregnated in RuCl 3 (0.0156 min -1  and KRuO 4 (0.0139 min -1  solutions, respectively. Nevertheless, the highest rate constant value of TB degradation (87.8%) was 0.0172 min -1 using 0.16 wt% Ru loading on Ti/TiO 2 composite synthetized at pH 7 impregnated in RuCl 3 ; this rep- resents 1.15 times of that on Ti/TiO 2 composite (0.0150 min -1 ; 81.4% color removal) synthetized under the same conditions. Keywords: Ru-Doped, TiO 2 Nanotubes, Anodization, Photocatalytic Activity. 1. INTRODUCTION Several environmental problems have arisen with the exploitation of natural resources that leads to water pol- lution and environmental damage, causing affectation in humans. The advanced oxidation processes (AOP) repre- sent a friendly environmental alternative for the removal of bio recalcitrant compounds from wastewater. TiO 2 -based photocatalysis is among the AOP that has been extensively studied for water and wastewater treatment applications as it is non-toxic, photochemical stable and inexpensive [1]. ∗ Author to whom correspondence should be addressed. TiO 2 properties and its performance depend partially on its morphology and crystalline form, for instance, TiO 2 nanotubes (TiO 2 -NT) offer some advantages over TiO 2 films due to TiO 2 -NT provide large surface-to-volume ratio and unidirectional electrical channel [2]. Thus, tita- nium anodization is a promising technique for the for- mation of micro and nano structures of TiO 2 for several applications such as gas sensor [3], orthopedic applica- tions [4], water treatment by photocatalysis and photo- electrocatalysis [5, 6], photovoltaic cells [7, 8], amongst some others. Many studies have reported titania modifi- cation with metal oxides (like CdS, Fe 2 O 3 , NiO, RuO 2 , J. Nanosci. Nanotechnol. 2019, Vol. 19, No. 8 1533-4880/2019/19/5211/009 doi:10.1166/jnn.2019.16823 5211