Urea-assisted cooperative assembly of phosphorus dendrimer–zinc oxide hybrid nanostructures

Abstract

Herein, phosphorus dendrimer-assisted sol–gel mineralisation of molecular zinc species is explored to access porous dendrimer–zinc oxide hybrid materials. Screening of various second-generation dendrimers peripherally-functionalized by phosphonate, catechol, ammonium and acetylacetonate groups showed a marked difference in terms of their morphology and hybrid composition, thereby highlighting the importance of surface-chemistry for the nucleation and growth of the zinc oxide inorganic phase. The homogeneous composition and distribution of the two dissimilar dendritic and metal oxide building-blocks is reached using phosphonate-terminated and catechol-terminated dendrimers. In contrast, significant leaching occurs in the case of ammonium-terminated and acetylacetonate-terminated dendrimers, leading rather to an enriched zinc oxide monophasic system. When urea was added as a ternary component, beyond improving mineralisation, interesting cooperative assembly was observed, particularly in the case of phosphonate-terminal dendrimers, which resulted in the formation of mesoporous phosphorus-containing lamellar zinc oxide hybrid materials.