Towards developing an efficient sensitive element for trinitrotoluene detection: TiO2 thin films functionalized with molecularly imprinted copolymer films

Abstract In this study, TiO 2 films were successfully grown in-situ onto a FTO substrate by a hydrothermal method, using TiCl 4 as Ti precursor, and further on functionalized with a 2,4,6-trinitrotoluene-molecularly imprinted polymer (TNT-MIP) film as a preliminary step in developing a trinitrotoluene (TNT) reusable sensor to overcome the international security issues. For investigating the TiO 2 film thickness, crystalline structure and morphology, the films were autoclaved at 200 °C at different times. The X-ray diffraction showed that TiO 2 films possessed a rutile structure, with no cracks visible by atomic force microscopy (AFM), and the films morphology observed by scanning electron microscopy (SEM) was highly dependent upon the hydrothermal treatment time. Yet, the TiO 2 films with a more porous surface were more suitable for TNT-MIP film deposit. Rheology of precursor polymer film solutions, based on poly (acrylonitrile- co -acrylic acid), poly (acrylonitrile- co -methacrylic acid) or poly (acrylonitrile- co -itaconic acid), and the structure and adherence of TNT-MIP films were investigated in order to establish the correct recipe of the MIP. The removal yield of TNT from the imprinted films, the thickness, the porosity and the compatibility with the inorganic TiO 2 film were adequate for the poly (acrylonitrile- co -acrylic acid) system with an acrylonitrile: acrylic acid practical ratio of 86.1:13.9 (wt./wt.). Farmore, AFM morphology corroborated with SEM results highlighted the effect of TNT imprinting in the copolymer matrix as the surface of the imprinted layer was quite different from that of the non-imprinted layer.