Polymeric platform for the growth of chemically anchored ZnO nanostructures by ALD

Abstract

The synthesis of hybrid nano-composites in which an inorganic layer is grown on a polymeric surface via chemical bonds, is a challenging goal for many applications from photocatalysis, to sensing and optoelectronics. Herein, we describe on the growth of ZnO nanostructures by an Atomic Layer Deposition (ALD) technique on polyetherimide (poly(2,2′-bis(3,4-dicarboxyphenoxy)phenylpropane)-2-phenylendiimide ULTEM® 1000) substrates. A surface modification consisting of a thermal photo-oxidization process, applied for different exposure times, has been properly performed on the polymer to promote the production of ALD suitable functionalities as reactive surface-sites. The chemical anchoring of the inorganic species from the gas-phase is demonstrated by spectroscopy and mass analyses to exclusively occur on the pre-oxidized films, whilst the ZnO growth does not occur in the untreated ULTEM® films in the operative ALD conditions. Notably, we demonstrate that two different regimes of growth take place in the oxidized polymer as a function of the photo-exposure time. In particular, the formation of a nanostructured coating of ZnO on the polyetherimide surface is found in the case of short-time photo-exposed polyetherimide (ALD-like regime), whilst an intermixed organic/polymer layer is found on the long-time oxidized films (Vapor Phase Infiltration, VPI-like regime). The photocatalytic activity of the synthesized materials has been tested through the degradation of methylene blue dye in aqueous solution under UV light irradiation, to give a proof of concept of a possible application of the nano-composites.