A new method for the preparation of rare-earth doped inverse opal materials is reported. Template structures consisting of ordered stacks of PMMA-spheres were infiltrated with colloidal solutions of luminescent LaPO 4 :Ln (Ln= Tb 3þ , Eu 3þ ) nanocrystals containing a small amount of prehydrolyzed tetramethoxysilane as binder. After calcination of the PMMA-template, light-emitting photonic materials with inverse opal structure are obtained. Under UV-excitation the materials display the characteristic luminescence line emission of the lanthanide component. We show that by adjusting the diameter of the PMMA-spheres of the template the photonic band structure of the material can be controlled in a way that modifies the lanthanide luminescence.

The growth of NdPO4 nanocrystals in diphenyl ether based reaction medium has been monitored by optical spectroscopy. Since the crystal field splitting and the intensity of the Nd3+ f−f transitions are affected by the coordination of the Nd3+ ions, different stages of the growth of NdPO4 nanocrystals can be distinguished by UV−visible absorption spectroscopy. It is found that a first reaction in homogeneous solution occurs already at room temperature when the phosphate-containing precursor solution is combined with the solution of the molecular Nd3+ precursor. Our results clearly indicate that a sol of NdPO4 nanoparticles with a mean particle diameter below 3 nm is thereby formed as the first product. Upon heating to 200 °C, this first product undergoes a complex sol−gel−sol transition, leading to a colloidal solution of 4−5 nm diameter NdPO4 nanocrystals. Further heating at 200 °C leads to annealing of the nanocrystalline lattice, but not to further particle growth if the amine concentration is sufficiently high.