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.

Role of La 5p in Bulk and Quantum-Confined Solids Probed by the La 5p54f1 3D1 Excitonic Final State of Resonant Inelastic X-ray Scattering

“…We can now utilize our established sensitivity of La 5p by looking at the changes in delocalization undergoing geometrical quantum confinement. ,, By keeping the bond length, coordination, and local geometry equivalent in LaPO 4 , namely, monoclinic structure, we prepared 0D, 1D nanostructure and bulk samples: LaPO 4 :Ce,Tb quantum dots (QD), LaPO 4 quantum wires (QW), and bulk-like LaPO 4 microcrystals. Diffuse reflectance spectroscopy (DRS) measurements (Figure S7) show confinement for the nanoscale objects, and only the bulk samples possess clear band-like absorption in the lower energy window.…”

“…Amorphous powder: La 2 O 3 (99.9%, Alfa Aesar). Nanoparticles: LaPO 4 :Ce,Tb quantum dot (QD), LaPO 4 30 nm quantum wire (QW, synthesis modified from Riwotzki et al), and LaPO 4 microrod (synthesis modified from Wang et al) . Characterization and detailed synthesis are provided in Supporting Information Figures S4–S6.…”

“…The f-block rare-earth (RE) elements (La–Lu) are present in many compounds with a wide range of applications, including phosphors, − scintillators, , superconductors, , and solid-state lasers , as well as catalysts. − The RE elements are generally considered to be atomically localized species, mainly caused by their highly localized frontier orbitals. − This is in strong contrast to actinides, where the 5f orbital is spatially more diffused and evidenced to be involved in covalent bond formation. − However, recently both theoretical and experimental work suggested that the REs contribute to band formation and screening. − Do the 4f-block REs participate in chemical bonding, and which orbitals contribute to covalency? How can this be linked to material functionality?…”

Cerium‐Modified Mesoporous Antimony Doped Tin Oxide as Intercalation‐Free Charge Storage Layers for Electrochromic Devices

“…[34,35] The latter should help to induce the redox reactions of the cerium compound on the surface considering the high positive redox potential of the Ce 3+ /Ce 4+ couple. [36,37] Especially when small nanoparticles are used to form the scaffold, the resulting mesoporous layers provide a large internal surface area that can be modified and are still able to achieve fast switching times, regardless of the size of the non-intercalating cations in the electrolyte. [33] Herein, we report on the fabrication of mesoporous ATO electrodes and the deposition of a redox-active cerium compound on their surface by a simple immersion method.…”