Atomic structure and surface defects at mineral-water interfaces probed by in situ atomic force microscopy

Area of Science:

• Materials Science
• Surface Chemistry
• Nanotechnology

Background:

• Atomic scale surface structure is critical for solid-liquid interfaces.
• Macroscopic techniques offer averaged data, while high-resolution imaging reveals defect roles.

Purpose of the Study:

• To visualize and characterize the morphology and atomic structure of clay mineral nanoparticles at solid-liquid interfaces.
• To investigate the role of surface defects on clay nanoparticles in ambient water.

Main Methods:

• High-resolution dynamic Atomic Force Microscopy (AFM) was employed.
• Imaging was performed on various clay mineral nanoparticles (gibbsite, kaolinite, illite, Na-montmorillonite) adsorbed to solid surfaces in ambient water.

Main Results:

• Atomically resolved images of the (001) basal planes were obtained for all investigated clay minerals.
• Regions of perfect crystallinity and extensive surface defects, including vacancies, steps, and adsorbed species, were routinely observed.
• The presence of defects was confirmed across both natural and synthetic samples.

Conclusions:

• Surface defects are ubiquitous on clay nanoparticle basal planes in contact with water.
• These defects significantly influence the physical and chemical properties of clay nanoparticle-water interfaces.
• Understanding these atomic-scale features is essential for solid-liquid interface science.