Surface charge microscopy: novel technique for mapping charge-mosaic surfaces in electrolyte solutions

Area of Science:

• Surface Science
• Colloid and Interface Science
• Geochemistry

Background:

• Zeta potential and streaming potential are crucial for understanding particle-surface interactions but typically yield average values.
• Real-world materials often exhibit surface heterogeneities, limiting the applicability of average electrokinetic measurements.
• Accurate, spatially resolved surface potential mapping is needed to characterize heterogeneous materials.

Purpose of the Study:

• To develop and demonstrate a novel technique for mapping surface potential heterogeneities.
• To investigate the surface charge distribution across different phases of multiphase volcanic rock.
• To assess the capability of atomic force microscopy (AFM) for high-resolution surface potential analysis.

Main Methods:

• Utilized atomic force microscopy (AFM) with a silicon nitride cantilever to measure interaction forces on volcanic rock.
• Conducted experiments in electrolyte solutions with varying ionic strengths and pH.
• Acquired force-distance curves across phase boundaries and calculated surface charge densities using the DLVO theory.

Main Results:

• Observed significant differences in surface charge densities between adjacent phases of the volcanic rock.
• Detected gradual transitions in surface charge density at the interfaces between different phases.
• Demonstrated the ability to examine one- and two-dimensional surface potential distributions.

Conclusions:

• AFM provides a powerful tool for characterizing spatially resolved surface potential and charge heterogeneities.
• The developed method overcomes the limitations of traditional electrokinetic measurements for heterogeneous surfaces.
• This technique offers valuable insights into the surface properties of complex geological materials.