| Sample | Reagent (15 mmol)/Solvent (70 ml) | Urea (mmol)/PVP (g) | Temperature (˚C)/Time (h) |
| nanocloud Co3O4 | Co(NO3)2/CH3OH | 30/0 | 180, 12 |
| nanosphere Co3O4 | Co(NO3)2/(CH2OH)2 | 30/0 | 180, 12 |
| nanobook Co3O4 | Co(AC)2/H2O | 75/0.15 | 100, 12 |
| nanoflower Co3O4 | Co(NO3)2/H2O | 75/0 | 140, 12 |
| nanorods Co3O4 | CoCl2/H2O | 75/0 | 100, 12 |