Sn-doped ZnO nanostructure deposited with free-catalyst chemical vapor deposition route: optical, electrical and photocatalytic properties

In this work, the free-catalyst chemical vapor deposition technique is used for synthesizing SnxZn1-xO, x = 0.00, 0.02, 0.04, 0.06, and 0.08 nanostructures. X-ray diffraction analysis demonstrates that all of the samples have crystallized into a pure hexagonal-wurtzite structure without any impurities or secondary phases. The effect of adding Sn on the structural parameters, including crystallite size, bond length, lattice strain, unit cell, volume, and dislocation density of ZnO, is studied. Electron microscopy investigation proves that increasing the Sn concentration is associated with a transformation in the morphology from needles- to flakes-like shape. A blue shift in the optical energy gap is observed when Sn4+ cations are incorporated into the ZnO network structure, according to the UV-visible spectra in coincidence with the Burstein-Moss model. The electrical conductivity measurements reveal typical semiconductor features of the synthesized nanostructures where the thermally activated electrical conduction mechanism dominates. The photocatalytic mechanism is defined, and the rate constants and photodegradation efficiency are calculated. It is found that the photocatalytic properties are improved at an optimum doping ratio rather than rising linearly with the doping level. The Sn0.04Zn0.96O compound demonstrates the best photocatalytic capacity when exposed to UV light and attains the maximum degradation efficacy of 63.8% after irradiation for 180 min (photodegradation rate constant of 5.2 x 10-3).