Fluoride coordination provides a beneficial, sometimes crucial chemical environment to optical phenomena generated from rare earth ions. Examples may be found in several luminescence effects. Due to high ionicity and correspondingly low phonon frequencies, access to efficiency can be gained in the NIR emission range and eventually NIR to VIS upconversion. Furthermore, especially in materials based on Eu³⁺, low lying charge transfer states can be suppressed, as required for e.g. two photon emission (downconversion, quantum cutters).
Hosted by nanoporous silicate matrices, initially, parent fluoride complexes were prepared in the voids of the matrix and subsequently converted into encapsulated nanoscaled fluoride and oxifluoride particles by thermal decomposition. In the resulting host-guest hybrid materials the porous structure of the matrices can be maintained, such that surface coordination effects of the nanoparticles to the matrix and subsequently penetrating water or other volatile chemicals can in suitable rare earth systems be monitored using luminescence spectroscopy, despite encapsulation.
TEM measurements, absorption spectra ranging from VUV to NIR, accompanying luminescent properties and stoichiometric parameters of both, zeolite based materials and sol-gel derived silicas as hosts are elucidated.

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1. Potential of nano-sized Rare Earth fluorides in optical applications