Accessing the surface chemistry of silicate minerals with nc-AFM

Abstract

Silicate minerals underpin key processes in geochemistry, atmospheric science, and materials technology, yet their atomic-scale surface chemistry remains insufficiently understood. Their intrinsic heterogeneity and electrical insulation have long limited experimental characterization, leaving most mechanistic insight to simulations. Here, we extend the capabilities of noncontact atomic force microscopy (NC-AFM) in ultrahigh vacuum to achieve genuine atomic and chemical resolution on natural silicates (muscovite mica [1, 2], feldspar microcline [3], wollastonite [4]) that had previously remained unresolved. Our measurements, complemented by density functional theory, provide direct, real-space evidence for processes central to mineral reactivity, such as ion hydration, ice nucleation, and carbonation reactions. They demonstrate that atomically resolved NC-AFM can access mechanistic insight previously restricted to theory and offer benchmark data to guide and challenge emerging computational models of mineral–water–gas interactions. [1] Franceschi et al., Nat. Commun. 14, 208 (2023) [2] Franceschi et al., Faraday Disc. 249, 84 (2024) [3] Franceschi et al., JPCL 15, 15 (2023) [4] Conti et al., submitted (2025)