Monazite LaPO₄:Eu³⁺ nanorods as strongly polarized nano-emitters

Orientation analyses of macromolecules or artificial particles are vital for both fundamental research and practical bio-applications. An accurate approach is monitoring the polarization spectroscopy of lanthanide-doped nanocrystalline materials. However, nanomaterials are often far from ideal for the colloidal and polarization luminescence properties. In the present study, we synthesize well-dispersed LaPO₄:Eu³⁺ nanomaterials in an anisotropic rod shape. Microwave heating with excess addition of phosphate precursor invokes a rapid phase transition of rhabdophane into monazite. The colloidal stability of the nanorod suspension is outstanding, demonstrated by showing liquid crystalline behaviors. The monazite nanorods are also superior in luminescence efficiency with limited defects. The emission spectrum of Eu³⁺ consists of well-defined lines with prominent polarization dependencies for both the forced electric dipole transitions and the magnetic dipole transitions. All the results demonstrate that the synthesized monazite nanorods can serve as an accurate probe in orientation analyses and potential applications, such as in microfluidics and biological detections.