Figure 2.

SEM images of the top surface of NPA used as nanopore sensing platform with different pore diameters (A) small pore around 25 ± 2 nm (B) medium size pore around 45 ± 2 nm (C) large pore around 65 ± 2 nm, prepared in 0.3 M oxalic acid electrolyte using different anodization voltages 30–70 V and times between 20 to 180 min to achieve the same pore length (D) Cross section SEM images of NPA with the inset figure (scale bar 100 nm) showing well-ordered and aligned pores through the full thickness of the membrane.