NanoTiO₂@DNA complex: a novel eco, durable, fire retardant design strategy for cotton textiles

A strategy for the design of cotton flame retardant coatings is described, exploiting the natural intumescent formulation of nucleic acids, the intrinsic thermal inertia of TiO₂ ceramic phase and the strong affinity that TiO₂ nanoparticles shows for amphiphilic biomolecules (e.g. proteins, nucleic acids) and hydrophilic substrates. Two different self-assembled TiO₂@DNA systems are obtained by mixing two opposite charged TiO₂ nanoparticles suspensions with DNA solution. The colloidal behavior of separate and mixed phases was investigated, as well as the morphological, chemical structure and thermal properties of resulting coatings, in order to make some hypothesis on the observed synergic effects. Scanning electron microscopy (SEM) and Attenuated Total Reflectance (ATR) spectroscopy demonstrated the homogeneous distribution of nano-TiO₂@DNA based coatings on the treated fabrics. The washing fastness tests evidenced the highly improved performance of hybrid coatings if compared with DNA alone. The flammability and cone calorimetry test results confirmed this positive synergy that resulted quite effective in slowing down (or even blocking) the propagation of a flame within the treated substrates and in improving the resistance of the fabrics to the applied heat flux, these latter leaving increased residues at the end of the test.