All extinction spectra produced in the titration experiments were fit with the HEDA model, resulting in uniformly excellent fits (Figure and). The electron concentration in the plasmonic core (ne) increases progressively as CoCp*2 is added to the NC dispersion (Figure and S13), a result of electron transfer from CoCp*2 to the NCs. The associated standard deviation in the electron concentration (σne) does not change significantly with increased addition of CoCp*2 (Figure ). Concomitantly, there is also an increase in the volume fraction of the undepleted core (fe), so added electrons are distributed both in the core (where they increase ne) and in the depletion layer (causing the core to expand) (Figure ). These results validate our interpretation of the increasing LSPR frequency as arising from higher ne in the core and reveal that the increasing extinction upon with addition of CoCp*2 is due to the addition of electrons in an increasingly large plasmonic core. This is also in general agreement with previous observations on electrochemical doping of Sn:In2O3 NCs, however, previous interpretations have been complicated by the presence of inter-NC plasmonic coupling, which partially obscured the increasing electron density in the plasmonic core. While the electron density at saturation is comparable for different sizes (Figure ), the maximum number of electrons per NC scales with NC volume (Figure and S15), similar to previous reports. While the smallest NC (8 nm) accommodates a maximum of ~270 electrons per NC, 21 nm NCs are able to hold as many as 4650 electrons per NC.