Modification of Nanocrystalline TiO2 with Phosphonate- and Bis(phosphonate)-Bearing Macrocyclic Complexes: Sorption and Stability Studies
Abstract
The first systematic study of chemical adsorption and desorption of phosphonic acid and geminal bisphosphonic acid on/from the surface of anatase nanoparticles is reported. Stable TiO2 colloidal nanodispersions were used in the study.
The colloidal stability is preserved upon the nanoparticle modification. Macrocyclic lanthanide(III) complex, attached through phosphonic/ bisphosphonic group to TiO2 surface allowed precise quantification of sorption parameters via ICP-AES.
Results show different behavior of phosphonate and bisphosphonate groups. For phosphonate, a monomolecular layer formation was observed and the desorption rate depends on the sorption conditions.
It is probably caused by different phosphonate binding modes on the surface. Excess of phosphate in washing media accelerates desorption rate of the phosphonate.
The bisphosphonate is adsorbed on the surface in large quantities forming multilayers which resist desorption even in the presence of phosphate ions and, thus, bisphosphonate moiety is a suitable group for anchoring of other molecules on the TiO2 particles surface.