Although addition of CoCp*2 solution results in a simultaneous increase in the LSPR extinction and frequency for all samples, the maximum LSPR shift is significantly affected by the NC diameter and Sn doping concentration. To separate the effects of each of these parameters on the LSPR shift, we compare a Sn:In2O3 doping series with consistent diameter and a size series with consistent Sn doping concentration. Increasing the Sn doping concentration while keeping the diameter nearly constant leads to a decrease in the maximum LSPR shift (Figure and). Highly doped NCs have a thin depletion layer and a plasmonic core with a high initial concentration of electrons, which changes little when extra electrons are added, thus limiting the change in LSPR frequency. Similarly, when we increase the diameter of the NCs while keeping the doping percentage almost constant, we observe a decrease in the maximum LSPR shift (Figure and). In larger NCs, added electrons are also accommodated mostly in the depletion layer with the electron concentration in the plasmonic core remaining nearly unchanged. Conversely, in smaller, lightly doped NCs, the band bending due to depletion extends through much of the NC volume, so adding electrons in this region does significantly increase the electron concentration responsible for the LSPR. To summarize, increasing the NC diameter or the Sn doping concentration leads to a decrease in the depletion layer volume fraction and corresponding maximum LSPR shift. These trends with size and Sn doping are all in excellent correlation with prior observations regarding electrochemical charging made by Zandi et al. These maximum LSPR shift trends are confirmed across all other size and doping series (Figures ). For all NC diameters, the maximum LSPR shift decreases with increasing Sn doping concentration (Figure ). However, the maximum LSPR shift changes only moderately because at the relatively high doping concentrations studied here, the initial electron concentrations are already high, so a large change in electron population is needed to significantly shift the LSPR. Independent of the Sn doping concentration, increasing the NC diameter similarly leads to a decrease in the LSPR shift (Figure ). The change with NC diameter is more drastic than with dopant concentration because a small change in the NC diameter causes a large change in the volume fraction of the depletion region and ultimately the maximum LSPR shift.