Self-Assembled Colloidal Photonic Structures for Directional Radioluminescence of Gd and Ta Oxide Scintillators

Radiation detection is being revolutionized by integrating photonic elements into scintillators. In this study, a scalable and cost-effective method is proposed to achieve tuneable emission enhancement across the visible spectrum by colloidal self-assembly of photonic crystals on scintillator surfaces. This concept is demonstrated for Eu³⁺/Tb³⁺-doped Gd and Ta oxides. Widely available and affordable colloidal nanospheres of SiO₂ or polymethyl methacrylate are self-assembled on these scintillators. The size of the nanospheres is carefully optimized to match the desired emission lines of Eu³⁺/Tb³⁺. The result is homogeneous and closely-packed structures with clear photonic bandgap in the visible range. Under X-ray excitation, the scintillators covered with the photonic layers exhibit enhanced light extraction in the direction perpendicular to the surface, compared to isotropic emission in the bare scintillator. Such scintillation directionality, when optically matched with a proper detector, will result in higher efficiency of the overall detection system. Moreover, X-ray imaging demonstrates an enhancement of 25% in system resolution of the scintillator supplemented with the photonic layer compared to unmodified scintillators. The proposed method is scintillator- and nanosphere-agnostic, thus offering a promising versatile approach for directing the scintillation light toward a photodetector and increasing detection system performance, including high-resolution imaging applications.