Photo-Electrochemical Device Enabling Luminescence Switching of LaPO4:Ce,Tb Nanoparticle Layers

Abstract

The luminescence properties of LaPO4:Ce,Tb nanoparticles are known to depend on the oxidation state of the cerium ions. However, their assembly into thin films exhibiting reasonable fast Ce3+/4+ electrochemistry is not trivial. Herein, the electrochemical luminescence switching of LaPO4:Ce,Tb nanoparticles, assembled as nonconducting thin films, using two electrocatalytic processes, is demonstrated. Due to the insulating nature of these nanoporous films, redox shuttles are used to access the redox active Ce3+/4+ species for electrochemical reactions. A series of redox shuttles with various redox potentials are employed to investigate their capability to electrochemically oxidize Ce3+ within the nanoparticles. Thereby the formal redox potential of the Ce3+/4+ couple in LaPO4:Ce,Tb nanoparticles is determined to lie within 0.89 and 1.15 V versus Ag/AgCl. In situ observation of repetitive luminescence switching is realized by assembling a device that allows UV light to enter the nanoparticle layer. With two redox shuttles present in the electrolyte, one for the oxidation of Ce3+ and the other for reduction of Ce4+, quenching and restoration of the luminescence is monitored. The resulting device represents the first down-sizable logical AND gate with UV light and voltage inputs and a vis light output based on a solid state LaPO4:Ce,Tb layer.