Synthesis of luminescent ZnO 1-D nanorods functionalized with phosphonic acid-based monolayers for the covalent anchoring of functional molecules

ZnO nanostructures have attracted great interest in the preparation of systems of high surface area in several applicative fields ranging from dye-sensitized solar cells (DSSCs) to high selectivity chemical sensors. In this perspectives, the controlled synthesis of hybrid systems consisting of ZnO functionalized with specific molecules is a key factor for the design of high performance devices. Herein we report a study on the synthesis of a nanostructured hybrid material consisting of luminescent ZnO nanorods, obtained by Metal-Organic Chemical Vapor Deposition and/or Chemical Bath Deposition, covalently functionalized with monolayers of various linear phosphonic acids (namely propylphosphonic acid, 3- aminopropylphosphonic acid, 3-phosphonopropionic acid and 16- phosphonohexadecanoic acid). Specific functional molecules have been covalently anchored through the aminic or carboxylic groups of the phopsphonic monolayer. The obtained organic/inorganic material has been characterised by X-Ray Photoelectron Spectroscopy, Attenuated Total Reflection-FTIR spectroscopy and luminescence measurements. The overall film morphology, hence, the surface area, as well as the nature of the phosphonic monolayer strongly affects the surface density, the packing and the total amount of the anchored functional molecules. These results give insights on the synthesis of ZnO nanostructures as multifunctional hybrid material.