ZnO
nanoparticles are still a hot area for research even after
ample work has been done by researchers across the world. It is a
versatile material for doping of different transition metals among
other metal oxides. Having a large family of morphological structures,
high electron mobility, and n-type carrier defects, it is suitable
for a number of applications such as memory devices, spintronics,
optoelectronic devices, solar cells, and sensors. Here, we have emphasized
a review of the effects of transition metal (TM) doping on the different
physical properties of ZnO nanoparticles and their applications. We
have gone through some theoretical models which were used by most
of the researchers for explaining the variations in physical properties.
Explanation of the sensing, photocatalytic, and optoelectronic processes
in different classes of devices is briefly described. Lastly, the
comparative studies of different devices are also made available for
clear understanding.