Suppression of Cation Intermixing Highly Boosts the Performance of Core–Shell Lanthanide Upconversion Nanoparticles

Abstract

Lanthanide upconversion nanoparticles (UCNPs) have been extensively explored as biomarkers, energy transducers, and information carriers in wide-ranging applications in areas from healthcare and energy to information technology. In promoting the brightness and enriching the functionalities of UCNPs, core–shell structural engineering has been well-established as an important approach. Despite its importance, a strong limiting issue has been identified, namely, cation intermixing in the interfacial region of the synthesized core–shell nanoparticles. Currently, there still exists confusion regarding this destructive phenomenon and there is a lack of facile means to reach a delicate control of it. By means of a new set of experiments, we identify and provide in this work a comprehensive picture for the major physical mechanism of cation intermixing occurring in synthesis of core–shell UCNPs, i.e., partial or substantial core nanoparticle dissolution followed by epitaxial growth of the outer layer and ripening of the entire particle. Based on this picture, we provide an easy but effective approach to tackle this issue that enables us to produce UCNPs with highly boosted optical properties.

Dual heterogeneous interfaces enhance X-ray excited persistent luminescence for low-dose 3D imaging

“…19 ). Despite the possible presence of cation intermixing during shell growth 24 , 29 , 30 , the XEPL intensity of core@shell NPs with a heterogeneous structure remained stronger than that of their homogeneous counterparts (Supplementary Fig. 20 and Supplementary Note 2 ).…”

Efficient monodisperse upconversion composite prepared using high-density local field and its dual-mode temperature sensing

“…Lanthanide-doped upconversion nanoparticles (UCNPs) can absorb two or more low-energy photons to produce a single high-energy photon. 1–4 Owing to their extraordinary advantages of high chemical stability, excellent photostability, narrow-band peak emission, no background, and deep tissue penetration, 5–7 UCNPs have found important applications in solar cells and high-performance biolabeling. 8–10 However, the increase in the efficiency of UCNPs remains a challenge, which is fundamentally limited by the forbidden nature of f–f in lanthanide elemental ions and non-radiative processes mediated by the bulk and surface defects.…”

Understanding of Lanthanide-Doped Core–Shell Structure at the Nanoscale Level

“…The utility of heterogeneous core-shell structure design as an advanced strategy to modulate the properties of nanomaterials is remarkable. In recent years, scientific researchers have been exploring the phenomenon of cationic interfacial mixing and strain effects induced by lattice mismatch, and this advancement has enabled us to tackle the complex challenges at the atomic level in a more refined manner [56][57][58][59][60][61][62][63][64][65]. This review focuses on the fundamental research of rare-earth core-shell nanomaterials, which includes synthesis and characterization strategies, recent advances in interfacial ion-mixing phenomena and interfacial strain effects, as well as how to utilize the core-shell structure to achieve the efficient modulation of luminescent properties of upconverted nanoparticles.…”