Shape-controlled synthesis and self-assembly of highly uniform upconverting calcium fluoride nanocrystals

• Published in: Inorganic chemistry frontiers Vol. 11; no. 1; pp. 278 - 285
• Main Authors: Paik, Taejong, Greybush, Nicholas J, Najmr, Stan, Woo, Ho Young, Hong, Seong Vin, Kim, Seung Hyeon, Lee, Jennifer D, Kagan, Cherie R, Murray, Christopher B
• Format: Journal Article
• Language: English
• Published: London Royal Society of Chemistry 20.12.2023
• Subjects: Calcium fluoride; Liquid crystals; Lithium; Lithium fluoride; Luminescence; Nanocrystals; Nanospheres; Nanowires; Optical properties; Precursors; Self-assembly; Superlattices
• ISSN: 2052-1553; 2052-1545; 2052-1553
• DOI: 10.1039/d3qi01864d

Herein, the size- and shape-controlled synthesis of nearly-monodisperse, lanthanide-doped calcium fluoride (CaF 2 ) nanocrystals (NCs) is reported. The sizes and shapes of CaF 2 NCs are controlled by tailoring the reaction conditions, such as the concentration of lithium fluoride precursors, reaction time and temperature, and the procedure for adding the calcium trifluoroacetate precursors in the reaction mixture. Highly uniform CaF 2 NCs are synthesized with several morphologies, such as nanospheres, truncated octahedra, nanoplates, and nanowires. The shape-controlled CaF 2 NCs self-assemble into NC superlattices with long-range orientational and positional order forming crystalline and liquid crystalline structures. The near-infrared-to-visible upconversion luminescence properties are investigated by varying the types of dopants as well as the sizes and shapes of the CaF 2 NCs. A novel synthetic method to tailor the shapes of highly uniform upconverting CaF 2 NCs is demonstrated. We investigate the shape-dependent self-assemblies, and size, shape, and dopant composition-dependent upconversion luminescence of CaF 2 NCs.