Zinc ion-hydroxyl interactions at undecanol-functionalized fused silica/water interfaces using the eisenthal X ⁽³⁾ technique

The interaction of Zn ²⁺ ions with undecanol-functionalized fused silica/water interfaces was studied directly at the aqueous/solid interface. We characterized the surface functionalization using vibrational sum frequency generation (SFG) and X-ray photoelectron spectroscopy (XPS). We then employed the SHG ξ ⁽³⁾ technique to determine the degree of silane functionalization, track Zn ²⁺ adsorption directly at the hydroxyl-terminated undecanol silane-functionalized fused silica/aqueous interface at pH 7 and 10 mM NaCl concentration, determine the electrostatic and thermodynamic binding parameters, quantify the change in interfacial potential upon zinc ion adsorption, and compare these values to our previous work with glucosamine-functionalized and bare fused silica/water interfaces. The results from the calculated adsorption free energy suggest that 2:1 hydroxyl/metal coordination complexes, which have not been observed with natural carbohydrates in the bulk aqueous phase, are possible in interfacial environments, with direct implications for controlling and predicting coordination chemistry.