We also explored a two-phase direct exchange that involved stirring oleate-capped UCNPs in hexanes with an immiscible layer of NMF containing dissolved Sn2S6 4-ligands. After stirring for 24 h, the UCNPs were observed to have either aggregated at the solvent interface or in the polar phase. Upon extraction, these UCNPs were unable to be redispersed in either a non-polar hexane solution or a polar NMF solution, implying that the ligand exchange was incomplete, i.e., UCNPs were only partially coated with Sn2S6 4-ligands.