New Hybrid Properties of TiO2 Nanoparticles Surface Modified With Catecholate Type Ligands

Surface modification of nanocrystalline TiO2 particles (45 Å) with bidentate benzene derivatives (catechol, pyrogallol, and gallic acid) was found to alter optical properties of nanoparticles. The formation of the inner-sphere charge–transfer complexes results in a red shift of the semiconductor absorption compared to unmodified nanocrystallites. The binding structures were investigated by using FTIR spectroscopy. The investigated ligands have the optimal geometry for chelating surface Ti atoms, resulting in ring coordination complexes (catecholate type of binuclear bidentate binding–bridging) thus restoring in six-coordinated octahedral geometry of surface Ti atoms. From the Benesi–Hildebrand plot, the stability constants at pH 2 of the order 103 M−1 have been determined

Negative influence of Ag and TiO2 nanoparticles on biodegradation of cotton fabrics

Recently, many efforts have been made to efficiently impregnate different textile materials with metal and metal oxide nanoparticles in order to provide antimicrobial, UV protective or self-cleaning properties. Evidence of their environmental risks is limited at this point. The aim of this study was to explore the influence of Ag and TiO2 nanoparticles on biodegradation of cotton fabrics. Biodegradation behavior of cotton fabrics impregnated with Ag and TiO2 NPs from colloidal solutions of different concentrations was assessed according to standard test method ASTM 5988-03 and soil burial test. Degradation of cotton fabrics was also evaluated by enzymatic hydrolysis with cellulase. The morphology of fibers affected by biodegradation was analyzed by scanning electron microscopy (SEM). In order to get better insight into biodegradation process, dehydrogenase activity of soil has been determined. Ag and particularly TiO2 nanoparticles suppressed the biodegradation of cotton fabrics. The dehydrogenase activity of soil with cotton fabrics impregnated with TiO2 nanoparticles was the weakest. Severe damage of cotton fibers during the biodegradation process was confirmed by SEM