Table 1.

Wüstite nanocrystals – atom counts and detection sensitivity.

Diameter (nm)	5	10	20	50	100
Number of iron atomsa	3,118	24,941	199,530	3,117,649	24,941,194
Detection limitsb	32 fmol	4 fmol	501 amol	32 amol	4 amol

^aThe number of Fe atoms per nanocrystal was estimated with Equation 2.

^bThe detection limits of wüstite nanocrystals are calculated for ferrozine assay performed in 96-well plates with the detection limit of ferrous ions equal to 0.1 nmol (Figure 1A).