1. Positive SECM feedback vs. tunneling
glass NP O R - e A
+e-
-e- B
Pt tip
Schematic representation of the SECM feedback at the floating metal NP (A) and tunnelling experiment (B) in which the overall charge-transfer process involves diffusion of redox species to the NP, faradaic reaction at its surface, and tunnelling between the tip and NP

2. Pt tip approaching a Au NP in 1 mM FcMeOH solution and zoom in of the tunneling region
glass Fc
Fc+ Au
glass Fc
Fc+
a = 30 nm, rp = 50 nm
tunneling
feedback
zoom-in
solid line – experiment
symbols - simulations

3. Tunneling mode image of a Pd cube
edge length 14 nm; tip radius, 10 nm