Optical properties of Laser Ablated Zn@ZnO in Water, Ethanol and Methanol

摘要

Laser ablation of Zn was employed to successfully synthesis different Zn@ZnO nanoparticles in water, ethanol and methanol. Zn@ZnO growth and oxidation is controlled by varying ambient surrounding liquid. The band gap was obtained as 3.49 and 3.67 eV respectively for Zn-water and Zn-ethanol from the tau plot, but show respective particle size 13.5 and 16.4 nm in TEM analysis. Discrepancy in absorption spectra and TEM is clearly due to the restricted oxidation in bigger Zn-ethanol nanoparticles. Zn-water nanoparticles were irregular in shape and agglomerated whereas well dispersed and clearly spherical nanoparticle was observed in Zn-ethanol. In emission spectra Zn-water showed dominant excitonic emission but defect green emission dominated in Zn-ethanol and Zn-methanol. Zn-methanol showed strong oxygen deficiency even after one week and presented an intense green emission. In water Zn undergone fast oxidation into ZnO nanoparticle, but their stability was very poor and sediment within one week. Whereas in ethanol Zn experienced slow oxidation but held intense absorption as well as emission spectra and they displayed high stability.