and phase-controlled
AFM was performed on positively functionalized mica (TedPella, Inc.)
substrates.43 (link) The mica surface was cleaved
and incubated for 1 min with 10 μL of 0.5% (v/v) (3-aminopropyl)triethoxysilane
(APTES) from Sigma-Aldrich (St. Louis, MO), in Milli-Q water. Then,
the substrate was rinsed three times with 1 mL of Milli-Q water and
dried by a gentle stream of nitrogen gas. 5 μM samples containing
Aβ-ZnO, Aβ-CuO, Aβ-AlO, or Aβ-FeO were then
deposited onto the functionalized mica surfaces. The droplet was incubated
for 10 min, then rinsed with 1 mL of Milli-Q water, and dried by a
gentle stream of N2. The preparation was carried out at
room temperature. AFM maps were realized by means of a JPK nanowizard2
system operating in tapping mode and equipped with a silicon tip (μmasch,
2 N m–1) with a nominal radius of 10 nm. Images
were flattened by using the SPIP software (Image Metrology, Hørsholm,
Denmark).