Nitroaromatic explosive sorption and sensing using electrochemically processed polyaniline-titanium dioxide hybrid nanocomposite Yong X. Gan a, * , Rachel H. Yazawa b , James L. Smith c , Jimmie C. Oxley c , Guang Zhang c , Jonathan Canino c , Joanna Ying c , Gerald Kagan c , Lihua Zhang d a Department of Mechanical Engineering, California State Polytechnic University-Pomona, 3801 W Temple Avenue, Pomona, CA 91768, USA b Department of Civil Engineering, California State Polytechnic University-Pomona, 3801 W Temple Avenue, Pomona, CA 91768, USA c Department of Chemistry, University of Rhode Island, Kingston, RI 02881, USA d Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA highlights graphical abstract  Titanium oxide nanotube/polyaniline hybrid composites were made.  Explosive sorption tests were conducted.  Nanostructured titanium oxide nanotube sorbs more TNT than pure titanium.  Polyaniline coated titanium dioxide nanotube changes color after it sorbs TNT.  Nanotubes coated with polyaniline show UV responses in TNT solutions. article info Article history: Received 30 September 2013 Received in revised form 8 November 2013 Accepted 29 November 2013 Keywords: Nanostructures Polymers Oxides Electrochemical techniques Electron microscopy Surface properties abstract This work deals with synthesis and characterization of polyaniline and titanium dioxide nanocomposites for explosive detection and mitigation. The titanium dioxide nanotube array was prepared through electrochemical oxidation of pure titanium in a fluorine ion-containing ethylene glycol water solution followed by annealing at 450  C in air. Polyaniline was obtained by electrochemical polymerization from an aniline and sulfuric acid solution. Both polyaniline and the nanotube show sorption of 2,4,6- trinitrotoluene (TNT) vapor at 60  C. Polyaniline modified by alginic acid sodium salt caused color change of TNT solutions. Polyaniline-based sensor showed decrease of electrical resistance in TNT acetonitrile solutions. Ultraviolet light response tests revealed that TNT caused significant drop in open circuit voltage of the titanium dioxide nanotube. In addition, the polyaniline/titanium oxide nano- composites show colorimetric responses in the explosive solution, which makes them have multiple response mechanisms for nitro-aromatic explosive detection and mitigation. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Nanostructured sensors have large surface areas and high sorption capability. They can generate fast measureable responses to accumulation of trace amounts of materials on their surfaces [1]. Several types of nanosensors have attracted attention. They can be made from carbon [2], polymers [3], metal nanoparticles [4], and various inorganic nanomaterials including silicon [5,6], sulfides * Corresponding author. Department of Mechanical Engineering, College of En- gineering, California State Polytechnic University-Pomona, 3801 W Temple Avenue, Pomona, CA 91768, USA. Tel.: þ1 909 869 2388; fax: þ1 909 869 4341. E-mail address: yxgan@csupomona.edu (Y.X. Gan). Contents lists available at ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys 0254-0584/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matchemphys.2013.11.059 Materials Chemistry and Physics 143 (2014) 1431e1439