Abstract: Methods for preparing core/shell nanocrystals are provided, using mismatched shell precursors and an electron transfer agent to control the nucleation and growth phases of particle formation. One method includes forming a reaction mixture comprising a plurality of nanocrystals, a first shell precursor, a second shell precursor, a weak electron transfer agent, and optionally a solvent, wherein, the first shell precursor and the second shell precursor have different oxidation states; and heating the reaction mixture to a temperature high enough to induce formation of the shell on each of the plurality of nanocrystals.