So far we discussed the data obtained from commercially available isopropoxides. We also synthesized Zr(O i Pr) and observed much slower decomposition kinetics (up to 6 times slower). Nevertheless, the synthesized precursors gave the same trends as the com-mercial ones: hafnium isopropoxide decomposes slower than zirconium isopropoxide (Figure ). These results explain certain observations during the synthesis of core/shell nanocrystals. We observed secondary nucleation of the shelling material when we used commercial Hf(O i Pr) 4 • i PrOH but not when using the in-house synthesized one. The faster precursor decomposition of commercial Hf(O i Pr) 4 • i PrOH leads to a build-up of decomposed precursor, which is not consumed fast enough by growth on existing cores and instead, nucleates new particles. Similar phenomena have been described in literature. The same reasoning explains why we observed secondary nucleation with zirconia as shelling material, but not with hafnia (due to its slower kinetics).