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A Viable Route for Lithium Ion Detection



Quartz substrates were first functionalized with 4-ClCH2C6H4SiCl3 and then allowed to react with 5-(4′-pyridylazo)-25,26,27-tris(ethoxycarbonylmethoxy)-28-hydroxycalix[4]arene in a covalent fashion to yield a hybrid material with an immobilized monolayer of a chromogenic sensing agent. The structural characterization of this ionophore monolayer on silica surfaces was performed by X-ray photoelectron spectroscopy. This technique was also used together with UV/Vis spectroscopy to investigate the ionophoric properties of the monolayer, which 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.