Lanthanide-doped LiLuF(4) upconversion nanoprobes for the detection of disease biomarkers.

Lanthanide-doped upconversion nanoparticles (UCNPs) have shown great promise in bioapplications. Exploring new host materials to realize efficient upconversion luminescence (UCL) output is a goal of general concern. Herein, we develop a unique strategy for the synthesis of novel LiLuF4 :Ln(3+) core/shell UCNPs with typically high absolute upconversion quantum yields of 5.0 % and 7.6 % for Er(3+) and Tm(3+) , respectively. Based on our customized UCL biodetection system, we demonstrate for the first time the application of LiLuF4 :Ln(3+) core/shell UCNPs as sensitive UCL bioprobes for the detection of an important disease marker ß subunit of human chorionic gonadotropin (ß-hCG) with a detection limit of 3.8 ng mL(-1) , which is comparable to the ß-hCG level in the serum of normal humans. Furthermore, we use these UCNPs in proof-of-concept computed tomography imaging and UCL imaging of cancer cells, thus revealing the great potential of LiLuF4 :Ln(3+) UCNPs as efficient nano-bioprobes in disease diagnosis.

Unraveling the Electronic Structures of Neodymium in LiLuF4 Nanocrystals for Ratiometric Temperature Sensing.

Nd3+-doped near-infrared (NIR) luminescent nanocrystals (NCs) have shown great promise in various bioapplications. A fundamental understanding of the electronic structures of Nd3+ in NCs is of vital importance for discovering novel Nd3+-activated luminescent nanoprobes and exploring their new applications. Herein, the electronic structures of Nd3+ in LiLuF4 NCs are unraveled by means of low-temperature and high-resolution optical spectroscopy. The photoactive site symmetry of Nd3+ in LiLuF4 NCs and its crystal-field (CF) transition lines in the NIR region of interest are identified. By taking advantage of the well-resolved and sharp CF transition lines of Nd3+, the application of LiLuF4:Nd3+ NCs as sensitive NIR-to-NIR luminescent nanoprobes for ratiometric detection of cryogenic temperature with a linear range of 77-275 K is demonstrated. These findings reveal the great potential of LiLuF4:Nd3+ NCs in temperature sensing and also lay a foundation for future design of efficient Nd3+-based luminescent nanoprobes.