Huanrong Li, Hebei University of Technology, China, and Gion Calzaferri, University of Bern, Switzerland, have shown how the luminescence of europium(III) complexes trapped in zeolite L pores is enhanced when they are plugged with stopper molecules.

Trivalent lanthanide complexes have a variety of applications, but they suffer from issues such as low stability and poor conduction properties. Encapsulation of the complexes in zeolite cavities is one way of overcoming these problems. The researchers then went one step further and investigated what happened if the channels were stoppered with an imidazolium salt, which can, for example, stop small molecules from entering or stop the host from leaving the channels. What was completely unexpected was that the luminescence intensity of the europium(III) complex increased dramatically upon stoppering, which was surprising as the stopper does not sensitize the europium(III) emission.

Further studies showed that the emission enhancement occurs as the proton activity inside the zeolite channels decreases upon stoppering. The stopper molecules that coat the zeolites also result in a more basic local environment. The team also produced thin films of the loaded zeolites that could potentially be used in sensors or optoelectronic devices.

• Luminescence Enhancement after Adding Stoppers to Europium(III) Nanozeolite L,
  Peng Li, Yige Wang, Huanrong Li, Gion Calzaferri,
  Angew. Chem. Int. Ed. 2014.
  DOI: 10.1002/anie.201310485