Source:College of Physical Science and Technology and Institute of Science and Technological Innovation, Hebei University

Recently, the Luminescence and Display Research Group of the Physics Institute has made significant progress in the field of surface reconstruction-induced enhanced upconversion luminescence over a wide temperature range. The related work "Bright upconversion over extended temperatures enabled by an organic surface layer" was published as the first author institution of Hebei University in "Nature Communications". Doctor Su Hao is the first and corresponding author of the paper, graduate student Zhao Peihang is the co-first author, and Professor Wang Feng from City University of Hong Kong is the co-corresponding author.

Rare earth upconversion nanocrystals are a new type of anti-Stokes luminescent materials, which have important applications in information security, biomedicine, and optoelectronic technology. However, nanocrystals are highly susceptible to surface quenching effects in practical applications, and their luminescence efficiency will further decrease at high temperatures. To date, no efficient upconversion nanocrystals with high luminescence in a wide temperature range have been developed. In response to these scientific issues, this paper reports a general strategy for synthesizing convenient nanocrystals without changing their size. By using surface-anchored organic molecules as an energy protection barrier, the upconversion luminescence can be significantly enhanced over a wide temperature range. The mechanism study reveals that the organic-inorganic hybrid surface layer can effectively resist defects and decouple high-energy oscillations, thereby inhibiting surface dissipation of excitation energy. The effect of this hybrid surface barrier increases with temperature rise, and the nanocrystals coated with ligands show enhancements of more than three and six orders of magnitude at room temperature and 443 K, respectively. Through the design of core-shell structures, the precise control of the upconversion energy protection sealing effect is achieved, and a high-brightness full-color thermochromic upconversion luminescence is established. This work provides a new idea for the development of high-performance upconversion nanocrystals and is expected to promote their practical applications in nanophotonics and biophotonics.  

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