Role of precursor dependent nanostructures of ZnO on its optical and photocatalytic activity and influence of FRET between ZnO and methylene blue dye on photocatalysis

Abstract

Role of different precursors on the nanostructure of hydrothermally synthesised ZnO is studied here. Well defined pencil like nanorods obtained from zinc acetate precursor are found to exhibit the highest photoluminescence intensity. Photoluminescence spectra as well as Commission Internationale de l'Eclairage (CIE) plots of all the samples show blue emission. To get an idea of the applicability of ZnO nanorods as the emissive layer in light emitting diodes, external electroluminescence efficiency (ELE) is determined using a mathematical model. ELE of pencil like nanorods reveals 1.2% external electroluminescence quantum efficiency at turn-on voltage of 2.6 V. The Forster resonance energy transfer (FRET) among ZnO (donor) and methylene blue (acceptor) can play a vital role on the photocatalytic activity of ZnO. In our case due to less overlap between absorption spectrum of methylene blue and emission spectrum of all the ZnO samples, FRET cannot occur between ZnO and methylene blue (MB) for a longer distance of separation between them. Hence ZnO synthesised from zinc chloride having lower particle size leads to less separation between ZnO and MB molecules compared to other two ZnO samples and shows the highest photocatalytic activity.