(a) Topography image
and height profile of kaolinite particle adsorbed
on sapphire imaged in 10 mM NaCl solution at pH 4. (c) Force map showing
tip sample interaction forces on the kaolinite particle in 10 mM NaCl
solution at pH 4. Note: The map is shown at 1 nm distance from the
surface. (d) Surface charge map calculated by analyzing the tip sample
interaction forces with DLVO theory. Force vs distance curves along
with theoretical calculated forces (black lines) on (b) silica and
(b′) gibbsite facet in 10 mM NaCl solution at pH 4, 6, and
9. Note: Representative force curves corresponding to each condition
are taken from the area marked on the force maps at kaolinite particle.
Tip parameters: for silica facet, Q = 2.16, f0= 16.97 kHz, kc= 0.367 N/m, and R= 13 ± 2 nm; for gibbsite
facet, Q = 2.37, f0=
17.06 kHz, kc= 0.448 N/m, and R= 18 ± 2 nm.