A Viable Route for Lithium Ion Detection

Quartz substrates were first functionalized with 4-ClCH2C6H4SiCl3 and then allowed to react, in a covalent fashion, with 5-(4'-pyridylazo)-25,26,27-tris(ethoxycarbonylmethoxy)-28-hydroxy-calix[4]arene molecules, to yield a hybrid material based on an immobilized monolayer of a chromogenic sensing agent. The structural characterization of this ionophore monolayer on silica surfaces was carried out by X-ray photoelectron spectroscopy. This technique was also used to investigate, together with UV-vis spectroscopy, the ionophoric properties of the monolayer that was found to reversibly recognize and bind lithium ions at ppm levels even in the presence (in a comparable concentration) of highly competitive cations such as Na+. Overall, our procedure shows that a single molecule property can be successfully transferred to a solid-state device.