Steps in growth of Nb-doped layered titanates with very high surface area suitable for water purification Marija Milanovi  c a, * , Ljubica M. Nikoli  c a , Ivan Stijepovi  c a , Athanassios G. Kontos b , Konstantinos P. Giannakopoulos b a Department of Materials Engineering, Faculty of Technology Novi Sad, University of Novi Sad, Bulevar cara Lazara 1, 21000 Novi Sad, Serbia b Institute for Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, NCSR “Demokritos”, Agia Paraskevi, 15310 Athens, Greece highlights graphical abstract  Nb-doped layered titanates have been prepared by a hydrothermal procedure.  Introduction of Nb to precursor lowers the rate of layered titanate formation.  Steps in growth of Nb-doped layered titanates are considered.  Nb-doped layered titanates show high/fast MB adsorption from concentrated solution. article info Article history: Received 24 February 2014 Received in revised form 20 August 2014 Accepted 30 August 2014 Available online 17 September 2014 Keywords: A. Ceramics A. Nanostructures B. Chemical synthesis D. Adsorption abstract Nb-doped layered titanates, as highly efficient adsorbents, have been synthesized by hydrothermal re- action for variable duration and at 150  C in a highly alkaline solution with NbCl 5 as the Nb source. The results have shown the formation of nanosheets already after 1 h of hydrothermal processing, but morphology and phase composition change as the reaction proceeds. The prepared layered titanates have been structurally investigated via scanning and transmission electron microscopy, X-ray diffraction, as well as Raman and Fourier transform infrared spectroscopies. The steps of layered titanate growth have been followed and an intermediate layered anatase phase is identified. Thus optimized growth of mesoporous titanate materials with 10% Nb atomic content present very high specific surface area of 345.3 m 2 g 1 , and perform as very efficient adsorbents for wastewater treatment applications. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Since Kasuga et al. [1] applied the alkaline hydrothermal method for the synthesis of titania nanotubes, substantial effort has been devoted to obtain various nanostructured titanates with specific elongated morphologies, including nanorods, nanofibers and nanosheets. Elongated titanate nanostructures possess unique combinations of structural and physicochemical properties (high surface area, large ion-exchange capabilities and electro- conductivity) that can provide a wide range of possible applica- tions, such as those in photocatalysis, lithium batteries, sensor applications, hydrogen production and storage, water purification etc. [2e4]. Recently, a lot of scientific interest has been directed towards investigations of two dimensional (2D) titanates (nanolayers or nanosheets) as a group of elongated titanates, from several points of view [5]. * Corresponding author. Tel.: þ381 21 485 3750; fax: þ381 21 450 413. E-mail addresses: majam@uns.ac.rs (M. Milanovi c), ljunik@uns.ac.rs (L.M. Nikoli c), ivan.stijepovic@gmail.com (I. Stijepovi c), akontos@chem. demokritos.gr (A.G. Kontos), kyann@imel.demokritos.gr (K.P. Giannakopoulos). Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys http://dx.doi.org/10.1016/j.matchemphys.2014.08.064 0254-0584/© 2014 Elsevier B.V. All rights reserved. Materials Chemistry and Physics 148 (2014) 874e881