  The structural stability, electronic properties and NH$_3$ adsorption
properties of pristine, Ti, Zr and F substituted $\alpha$-MoO$_3$
nanostructures are successfully studied using density functional theory with
B3LYP/LanL2DZ basis set. The structural stability of $\alpha$-MoO$_3$
nanostructures is discussed in terms of formation energy. The electronic
properties of pristine, Ti, Zr and F incorporated $\alpha$-MoO$_3$
nanostructures are discussed in terms of HOMO-LUMO gap, ionization potential
and electron affinity. $\alpha$-MoO$_3$ nanostructures can be fine-tuned with
suitable substitution impurity to improve the adsorption characteristics of
ammonia, which can be used to detect NH$_3$ in a mixed environment. The present
work gives an insight into tailoring $\alpha$-MoO$_3$ nanostructures for NH$_3$
detection.
