Influence of surface modification by organic molecules on optical properties of Eu3+-doped ZnO nanocrystals

Abstract

Abstract We have fabricated Eu3+-doped ZnO (ZnO:Eu) nanocrystals (NCs) surface-modified with organic molecules such as dodecylamine (DDA) and tri-n-octylphosphine oxide (TOPO) and have studied their optical properties. In the ZnO:Eu NCs without surface modification, strong broad photoluminescence (PL) band due to surface defects is observed, so the Eu3+ PL peaks are not observed because they are covered by the strong surface-defect PL band. In the DDA-capped ZnO:Eu NCs, the Eu3+ PL and the exciton PL are observed because of suppression of the surface-defect PL caused by the inactivation of the surface defects. Contrary to expectations, the surface modification with TOPO suppressed not only the surface-defect PL but also the exciton PL. As a result, the ZnO:Eu NCs with red PL due to the Eu3+ ions have been successfully prepared. We discuss the influence of surface modification by DDA and TOPO on optical properties.