Core-Shell Nanostructured Mixed Ligand Directed ZnO Nanoparticles with Excellent Structural, Optical and Electronic Properties for Application in Light Emitting Devices
In the present study, three salicylaldehyde based surface directing agents (L1, L2, L3) were synthesized from the same amine, but different aldehydes using condensation reaction for their employment as capping layer. Surface decorated zinc oxide (ZnO) nanoparticles (N1, N2 and N3) were then synthesized by wet chemical precipitation. The optical studies of mixed ligand directed ZnO nanoparticles were carried out using ultraviolet-visible (UV-Vis) absorption spectroscopy and photoluminescence techniques. The capping with ligand resulted in the successful amendment of surface of ZnO nanoparticles as it reduced the surface defects and controlled the defect-related emissions. The photoluminescence studies of surface modified ZnO nanoparticles N1, N2 and N3 were further carried out to check their binding ability. N2 and N3 exhibited selective behavior towards Al(III) and Cu(II) respectively with change in the fluorescence emission profile; however, no such change was noticed for other metal ions. An increased fluorescence intensity together with narrow spectrum is observed in N2 with the addition of Al(III) ion. The surface modified ZnO nanoparticles demonstrated semiconducting behavior when incorporated in Light emitting diode (LED) structure with steady-state current densities of up to 1.9 A/cm2.