Selective Sensing of Alkaline Cations by Calixarene Monolayers

The design of effective sensing agents that retain and possibly enhance their molecular recognition properties at the solid-state interface is a major challenge.1 Moreover, in both technological and pharmacological applications, the detection of alkaline cations is clinically significant in relation to lithium-, sodium- potassium- and calcium-based therapies for the treatment of diseases such as blood hypertension, osteoporosis, maniac-depressive illness (bipolar disorders) and other neurodegenerative diseases –such as Alzheimer’s and Parkinson’s– and amyotrophic lateral sclerosis.2 To this end, we have prepared a prototype (4-pyridylazo)-25,26,27-tris(ethoxycarbonylmethoxy)-28-hydroxy-calix[4]arene monolayer (Figure 1) that was covalently bound to silica-functionalized substrates to act as a Stimuli Responsive Material for selective alkaline cation detection. A detailed characterization of the monolayer (by UV-vis, XPS and AFM) will be provided together with a thorough spectrophotometric investigation of its ionophoric properties. Absorbance data will show that the hybrid material obtained is able to selectively and reversibly sense cation analytes at the ppm level (even in the presence of highly competitive ions), ultimately demonstrating that single molecule properties can be successfully transferred to a solid-state device.