| Abstract
| - We here report on the covalent grafting of various phosphated species (phosphoric acid, phenylphosphonicacid, and octyl phosphate) onto the surface of monoclinic zirconia nanoparticles obtained by hydrothermaltreatment of zirconium acetate. The initial particles are 60 nm aggregates of nanometric primary grainsand present an inner porosity. Small-angle X-ray scattering shows that the high specific area of the colloidalparticles (450 m2·g-1) decreases to 150 m2·g-1 upon drying. Therefore, phosphated reactants can accessthe whole internal surface of the aggregates only before drying. The surface of the particles can be coveredwith functional groups bound through a variable number of Zr−O−P bonds. Several factors probablyenhance the reaction between the particles and the phosphates or phosphonates: the large specific areaof the particles, a fully accessible porous network, and a large concentration of surface terminal groups.At the same time, the morphology of the particles is well preserved upon grafting. This is due to the goodcrystallinity of the primary grains that constitute the particles. In addition, the grafting drastically modifiesthe surface properties of the colloids. For example, the polarizability of the particles decreases in thesequence −POH > as-prepared ZrO2> −PC6H5> −POC8H17. Furthermore, the grafting of octyl phosphateallows exclusion of water from pores of 2 nm radius, up to hydrostatic pressures of 20 MPa.
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