were performed with a Nanoscope V MultiMode scanning probe microscope
(Bruker, Santa Barbara, CA) equipped with a closed-loop “vertical
engage” J-scanner and a sealed tapping fluid cell. Images were
acquired with silicon cantilevers (VISTAprobes) with spring constants
of ∼0.1 N/m, scan rates of ∼2 Hz, and drive frequencies
ranging from ∼8 to 10 kHz. AFM images were processed and analyzed
using MATLAB and its image processing toolbox (Mathworks, Natick,
MA), as previously described.83 (link)