2.5. Synthesis of CuO, NiO, and Co3O4 nanocrystals in mesoporous silica (MS)
spheres
The encapsulated particles were finally dispersed in urea solution at a concentration
of 0.1 M. The mixtures were then heated to 95 ◦C and dried at the same
temperature for 24 h to obtain the solid sample (assigned as as-prepared-1, asprepared-2,
and as-prepared-3, respectively). Then the as-prepared samples were
further calcined at 550 ◦C in air for 2 h. The resulting samples were denoted as
CuO/MS, NiO/MS, and Co3O4/MS, respectively