Figure 9a shows Qext-spr as a function of the coating thickness(tcoat) in water (nmed ) 1.333, solid line) and in toluene (nmed )1.50,24 dotted line) where the ncoat value was chosen to be typical for an optically transparent organic compound (ncoat ) 1.42, 0).
In the case of water as the surrounding medium (solid line in Figure 9a) Qext-spr increases by 13% when the coating is 4 nm thick (compared to the uncoated particle). Not surprisingly, Qext-spr approaches a value for thicker coatings, which is typical for an
uncoated particle in a medium having a real refractive index of