In conclusion, chemical doping allows a clear elucidation of the effects of surface depletion on the dynamic optical properties of doped metal oxide NCs, without convoluting effects of LSPR coupling. Volumetric additions of the reducing agent CoCp*2 to colloidal dispersions of Sn:In2O3 NCs systematically shift the LSPR energy and increase the extinction. The maximum shift in the LSPR was found to depend on NC diameter and Sn doping concentration, qualitatively consistent with reports on electrochemical charging, but quantitatively the maximum shift was significantly larger for chemical doping. By fitting the LSPR extinction data with a recently developed Drude model that accounts for heterogeneity in doping and NC diameter and the effects of surface depletion, we extracted the electron densities and undepleted core volume fractions during the chemical titration and found that the increase in LSPR energy was accompanied by a simultaneous increase in both quantities. We established that the maximum electron density achievable through chemical titration is independent of the NC diameter and depends only on the doping percentage, thus generalizing the conclusions of previous reports on photodoping of a single size of Sn:In2O3 NCs that were analyzed by electron counting titrations. Larger (smaller) NCs have a higher (lower) as-synthesized electron density, so they can accommodate less (more) additional electron density through chemical doping leading to an almost size-independent maximum electron density. We propose that an equilibration of the chemical potential of NCs with the reducing agents restricts the additional transfer of electrons beyond a dopant concentrationdependent maximum electron concentration. These results provide a systematic understanding of post-synthetic modulation of LSPR as it occurs in individual doped metal oxide NCs and lays an important foundation for interpreting modulation in thin films, like those investigated for smart window applications. Similar investigations using chemical titrations to interrogate other doped metal oxide NC compositions will shed light on the relevance of surface depletion in understanding properties across this emerging class of plasmonic nanocrystals, with implications for their potential applications in catalysis, sensing, therapeutics, and more. Experimental Section: Chemicals: For the synthesis and characterization of Sn-doped In2O3 (Sn:In2O3) nanocrystals (NCs), all chemicals were acquired commercially and employed without further purification prior to their use. Indium(III) acetate (STREM, ≥99.99%), tin(IV) acetate (Sigma-Aldrich 99.99%), oleyl alcohol (Sigma-Aldrich, 85%) and oleic acid (Sigma-Aldrich, 90%) were used for the synthesis of different Sn-doped In2O3 NCs. Oleylamine (Sigma-Aldrich, 70%), ethanol (Fischer Chemical, 90%), hexane (Fischer Chemical ≥99.9%), tetrahydrofuran (Sigma-Aldrich, ≥99.9%) and toluene (Sigma-Aldrich, 99.8%) were utilized for washing the resulting nanocrystals and characterizing them through different techniques. For chemical reduction of Sn:In2O3 NCs with decamethylcaboltocene, Sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate and Bis(pentamethylcyclopentadienyl)cobalt(II) were acquired from Sigma-Aldrich and dried prior to their use.