Mixed Zirconium Phosphate Bis-Phosphonomethyl Glycine from Nanocrystalline α-Zirconium Phosphate: A Tailored Suite for Gold Nanoparticles.

Abstract

A novel synthetic approach was investigated for the preparation of nanoplatelets of mixed zirconium phosphate bis-phosphonomethyl glycine, ZPGly, by the reaction of a gel of nanocrystalline α-type zirconium phosphate with N,N-bis-phosphonomethyl glycine, H3Gly. The syntheses were carried out in the absence of hydrofluoric acid by changing both the reagent relative amounts and temperature. An H3Gly/Zr molar ratio >2 did not significantly improve the degree of crystallinity of the materials, while an increase of temperature from 80 °C to 120 °C improved the crystallinity; the best result was obtained with H3Gly/Zr molar ratio = 2 and with a temperature reaction of 120 °C. The sample consisted of nanoplatelets with the size in the range 20-40 nm, and it was successfully exfoliated by treatment with a solution of methylamine. By treatment of the ZPGly colloidal dispersions with HAuCl4, a color change from white to red-violet was observed, indicating the formation of gold nanoparticles. The size and morphology of the gold particles were affected by the degree of crystallinity and, in turn, by the composition of the ZPGly support. As a matter of fact, large micrometric Au particles with a cubo-octahedral morphology were obtained by using the less crystalline ZPGly_R2-80 sample, while interconnected Au particles, with a size of about 16 nm, were obtained by using ZPGly_R2-120. The samples exhibited an absorption maximum in the visible region due to the surface plasmon resonance of gold nanoparticles.