Lanthanide-Doped Upconversion Nanomaterials: Recent Advances and Applications

Lanthanide-doped upconversion nanomaterials are well known for converting near-infrared (NIR) excitation photons into visible, ultraviolet, and NIR emission photons. Excitation of NIR light offers low autofluorescence background and high penetration depth in biological environments due to the reduced light scattering. Consequently, these have attracted considerable interest because their exceptional optical properties have led to applications in diverse areas such as bioassays, biomedical imaging, and forensics; these properties are, namely: large anti-Stokes shifts, sharp emission spectra and long excited-state lifetimes. The nanomaterials can be utilized for a variety of applications including detection of various analytes, bioimaging, therapies, energy conversion, and security. In this review, we briefly describe the upconversion luminescence process, effective synthetic approaches, and recent literature that elucidate the exceptional properties of these materials and its applications.