Viable route for switching of an engineered silica surface using Cu2+ ions at sub-ppm levels

Abstract

Quartz substrates were functionalized with a covalent 4-ClCH₂C₆H₄SiCl₃ monolayer. To this, N-(4-hydroxyphenethyl)-4,5-di[(2-picolyl)amino]-1,8-naphthalimide molecules were then covalently bonded, producing a new monolayer of these molecules on silica substrates. The surface chemical characterization of this hybrid material was carried out by X-ray photoelectron spectroscopy. The switching properties of this monolayer were studied at room temperature by UV-vis and XPS measurements. The system has reversible recognition properties for Cu²⁺ ions at sub-ppm levels and, therefore, can be reversibly switched using Cu ions as input and the absorbance intensity as output between two states represented by the free base and its copper complex. The adopted synthetic procedure has proven effective to transfer molecular properties to a solid state device.