Fig. 1 (a1) SEM image of bulk ZnO, (a2) TEM image of nanosized ZnO, (b1) SEM image of bulk PbO, (a2) TEM image of nanosized PbO, (c1) SEM image of bulk SnO, (c2) SEM image of nanosized SnO, (d1) SEM image of bulk Ga2O3, (d2) TEM images of nanosized Ga2O3.




Fig. 2 XRD patterns of the as-prepared (a) ZnO (JCPDS No. 79-205), (b) tetragonal PbO (JCPDS No. 05-0561), (c) SnO (JCPDS No. 06-0395) and (d) Ga2O3 (JCPDS No. 43-1012).

Pinhua Zhang, et al, CrystEngComm 14, 5937 (2012)
https://doi.org/10.1039/c2ce25398d

(1) Most of the metal oxide nanocrystals (NCs) can be prepared by calcination, decomposition, dehydration, ion-exchange reaction and so on.
(2) In a typical synthesis, Ga2O3, oleic acid, and Oleylamine were loaded into a three-necked flask, heated, immediately cooled to room temperature to quench the reaction by mixing 1.5 mL cold toluene, extracted by adding methanol and precipitated with the addition of excess acetone.
(3) The synthesis of nanosized SnO requires the protection of inert gas due to its characteristic of facile oxidation in the atmosphere. When the reaction was conducted under air atmospheres, the products were SnO2 NCs due to the presence of oxygen.
(4) The as-synthesized Ga2O3 appear to be porous structures, which are self-assembled by a number of nano-flakes.
(5) Dissolution–recrystallization involves the dissolution of metal oxides, the form of metal-oleic acid complexes and the crystallization into their crystalline form from solution, leading to a change in the morphology and size.