Controllable Synthesis of Upconversion Nanophosphors toward Scale‐Up Productions

Abstract

Upconversion nanophosphors (UCNPs) are considered as an important synthesis arm within biomedical and energy sectors due to their unique optical characteristics, which can convert near‐infrared light into higher energy emissions. However, key challenges, cost, compatibility of the materials, etc. have to be taken into serious consideration to transform this in‐lab UCNPs technology into scale‐up production for wider commercial needs. This review highlights the fundamental concepts of synthetic approaches for UCNPs and recaps recent advances in terms of large‐scale production. A number of typical synthesis routes in both batch and continuous processes are reviewed, alongside their limitations and potential improvements when being considered for mass production. By discussing and exploiting the technical compacity for the potential synthetic trends, key challenges, and expectations of future synthesis methods for UCNPs are also outlined.

Low-temperature open-air synthesis of PVP-coated NaYF 4 :Yb,Er,Mn upconversion nanoparticles with strong red emission

“…Further, synthesis requires high-temperature reactions for extended durations, e.g. up to 24 h [35][36][37][38][39]. UCNP synthesis at approximately 200°C typically produces α-phase UCNPs, whereas synthesis at greater than approximately 300°C produces β-phase UCNPs (see electronic supplementary material, figure S1) [36].…”

Top-Down Synthesis of Luminescent Microplastics and Nanoplastics by Incorporation of Upconverting Nanoparticles for Environmental Assessment

“…This approach allows the use of a single batch of phosphors to be further dispatched in multiple assays, therefore maintaining a homogeneous luminescence response over all samples. 31,32 As we noticed that a slow and separate introduction of fluoride and sodium sources via syringe pumps to the rare earth oleate mixture led to a dramatic size reduction, 33 we decided to adapt this strategy to the efficient protocol described by Zhang et al, known to yield 40 nm NaYF4-based UCNPs. 34 W collected regular hexagonal prism-shaped erbium-doped NaYF4:Yb30% and Er2% UCNPs (NaREF4, where RE= 2% Er; 30% Yb; 68% Y) with an average size of 21.8±1.3 nm even on an 11.6 mmol scale: up to 3 g of bright green emissive UCNPs could be obtained in this way.…”

Lanthanide-Ion-Doping Effect on the Morphology and the Structure of NaYF4:Ln3+ Nanoparticles

“…Combining the magnetic and luminescent properties of lanthanides provides a possibility to create bimodal materials for molecular imaging and non-invasive optical diagnostics of tissues of living organisms in vivo using magnetic resonance imaging (MRI), as well as materials for the detection and targeted treatment of cancer cells at early stages of the disease [ 13 , 14 , 15 , 16 ]. The optical and magnetic properties of doped rare-earth-element ions are well known to be sensitive in one’s own way to the host matrix type, crystal structure, morphology and size of substances, and rare-earth-element concentration [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ].…”