Energy Aggregation for Illuminating Upconversion Multicolor Emission Based on Ho³⁺ Ions

Lanthanide-doped upconversion luminescent nanoparticles (UCNPs) have garnered extensive attention due to their notable anti-Stokes shifts and superior photostability. Notably, Ho³⁺-based UCNPs present a complex energy level configuration, which poses challenges in augmenting their luminescence efficiency. Herein, a rational design strategy was used to enhance the upconversion luminescence intensity of Ho³⁺ ions by improving the photon absorption ability and energy utilization efficiency. Efficient absorption and transfer of excitation light energy were achieved through carefully selected host materials, precisely controlled sensitizers, and the design of external energy antennas using organic dyes, enhancing upconversion luminescence. Due to the attenuation effect of hydroxyl vibration on upconversion luminescence, the nanomaterials exhibit multicolor luminescent characteristics in different solution environments. Significantly, the composites exhibit intense upconversion of red light in aqueous solution, showing great application potential in biomedicine and colorimetry.