Emerging Frontiers of Upconversion Nanoparticles

Lanthanide-doped upconversion nanoparticles capable of converting near-infrared excitation into UV and visible emissions have attracted considerable research interests in recent years. Low-density near-infrared light needed for excitation of these nanoparticles is nondestructive and highly penetrating, offering significant technological advantages for biological and photonic applications such as remote neuron modulation, super-resolution imaging, and short-wavelength lasing. In this review, we describe several emerging classes of upconversion nanoparticles that have been developed to promote these technological applications by providing boosted emission intensities. We explain how heavy doping, thermal stimulating, and hybridizing can be harnessed to maximize absorption of excitation light and minimize quenching processes in these nanomaterials.