(Invited) Designing, Synthesis and Optical Properties of Ultrasmall β-NaYF₄ Nanocrystals Doped by Lanthanides Ions for Bio-Medical Applications

Abstract

In this work, structural and optical properties of ultrasmall hexagonal NaYF4 nanocrystals will be discussed as a function of different lanthanide ions combinations.

On the nature of carrier relaxation and ion–ion interactions in ultrasmall β-NaYF4:Eu3+nanocrystals – effect of the surface

“…The size of the smallest reported NCs, usually nanophosphors crystallized in the hexagonal (b) phase (25-50 nm), is not optimal for use as bioimaging probes. To the best of our knowledge, only several groups including ours [11][12][13][14] have reported hexagonal NaYF 4 nanoparticles ($6 to 8 nm) smaller than 10 nm. The reduction of the diameter of the NCs is an important goal, as nanoparticles smaller than 10 nm undergo more efficient body clearance.…”

“…For the reasons stated above, a number of papers were recently published that are related to NaYF 4 NCs that are doped or co-doped by lanthanide ions. [4][5][6][7][8][9][10][11] However, in most cases, the obtained NCs are characterised by their size of tens of nanometres (20-200 nm), wide size and shape distribution, and are crystallised in the cubic or a mixture of cubic and hexagonal phases. Moreover, most of them are designed to be excited in the infrared spectral range for up-converting phosphor applications.…”

Ostwald-ripening and particle size focussing of sub-10 nm NaYF4 upconversion nanocrystals

“…In fact, sub-10 nm particles NaYF 4 :Yb,Er were successfully prepared by replacing part of the yttrium by gadolinium 17,52,53 and by doping NaYF 4 with Eu and Tb. 54 To the best of our knowledge, however, only two papers report on the successful synthesis of nearly monodisperse β-NaYF 4 :Yb,Er particles with sizes below 10 nm without additional doping. 32,55 The smallest NaYF 4 : Yb,Er particles with diameters down to 4.5 nm were described by Ostrowski et al 32 Studies that unravel the parameters which determine the final size of β-NaREF 4 nanocrystals are complicated by the fact that not only particles of the hexagonal β-phase but also those of the cubic α-phase can nucleate and grow during the decomposition of the molecular precursors.…”

(Invited) Lanthanides Fluorides Doped Nanocrystals for Biomedical Applications

“…Doping nanocrystals with a different lanthanide ions allow to tune their optical, temporal as well as structural properties [45]. Figure 1 (a) shows the emission spectra obtained for three different systems: β-NaGdF 4 :Eu 3+ , β-NaGdF 4 :Yb 3+ ,Er 3+ and β-NaGdF 4 :Yb 3+ ,Tm 3+ .…”