We have synthesized highly porous nanoclusters of pure and
transition metal (Mn, Co and Ni) doped ZnO through a soft chemical
route. XRD analysis revealed the formation of single phase
wurtzite ZnO structure and their nanocrystalline nature. The transition
metal ions, Mn, Ni and Co were successfully doped into the
ZnO structure and are uniformly distributed in the samples. These
spherical porous structures are comprised of numerous nanocrystals
and are fairly stable, well-defined and discrete. However, the
pore shapes are irregular and the pore sizes are non-uniform.
The presence of a pronounced hysteresis loop in the N2 adsorption–desorption
isotherm curves indicates the 3D intersection network
of the pores and it increases with doping of transition metal
ions possibly due to the formation of smaller average nanocrystals
which in turn increase the porous network. It has been observed
that both pure and doped ZnO samples are predominantly mesoporous
in nature. The mesoporus ZnO nanoclusters exhibit excellent
photocatalytic activity for the degradation of methylene blue
under UV light as compared to transition metal (Mn, Ni and Co)
doped ZnO. Furthermore, these mesoporus structures may also
find applications in areas such as drug delivery, energy storage
and sensors. In addition, the general strategy involved here can
be readily extended to other transition metal oxide systems.