] -, likely through intercalation of chargebalancing H + ions in the NCs. Subsequent addition of 5 µL aliquots of 0.02 M CoCp*2 to a mixture of NCs and [H(OEt2)] + [BAr -acid causes a systematic shift of the LSPR energy to higher wavenumbers and an increase of the LSPR extinction even while the concentration of the NCs is being diluted (Figure ). Both observations suggest that there is a transfer of electrons from CoCp*2 to the Sn:In2O3 NCs which increases the electron density and overall electron population and, thus, the increased LSPR energy and extinction, respectively. The use of CoCp*2 as a reducing agent, the mechanism of protoncoupled electron transfer, and the role of -as a counter ion have been elucidated in previous reports and won't be further described in the current manuscript. Both LSPR energy and extinction reach a saturation point around the same amount of added reducing agent (Figure ). Further addition of CoCp*2 aliquots results in broadening of the LSPR linewidth and decrease in the LSPR extinction signifying partial loss in the colloidal stability of the NCs. This suggests that NCs have been charged beyond their thermodynamic ability to take up electrons within the conduction band and their spontaneous precipitation may be associated with other charging pathways, for example leading to a build-up of surface charge. The maximum LSPR shift throughout the manuscript is therefore reported as the difference in the LSPR energy of the saturation point and that of the original NC dispersion, ∆𝜔 𝐿𝑆𝑃𝑅 = 𝜔 𝑠𝑎𝑡𝑢𝑟𝑎𝑡𝑒𝑑 𝐿𝑆𝑃𝑅 -𝜔 𝑎𝑠-𝑠𝑦𝑛𝑡ℎ𝑒𝑠𝑖𝑧𝑒𝑑 𝐿𝑆𝑃𝑅 . The increase in the LSPR energy can be completely reversed by the addition of an oxidizing agent such as 2,4,6-Tri-tert-butyl-phenoxy radical validating that the LSPR modulation is due to a change in electron density in the NCs, rather than changes in the dielectric environment, for example. As expected, the maximum LSPR shift for a given NC composition (size, dopant concentration) is independent of the concentration in dispersion over a wide range (Figure ). This consistent saturation behavior suggests that CoCp*2 makes an excess of electrons available, always exceeding the maximum number that can be added to the NCs. Therefore, the maximum LSPR frequency shift can be compared across samples, regardless of differences in NC concentration. Furthermore, to confirm reproducibility of the maximum LSPR shift values, each NC composition was measured in triplicate under the same conditions and the average of their maximum LSPR shift values are reported with uncertainties obtained from statistical analysis.