Experimental study on the surface modification of Y₂O₃:Tm³⁺/Yb³⁺nanoparticles to enhance upconversion fluorescence and weaken aggregation

Abstract

In order to improve the solubility of doped nanoparticles in solutions, Y(2)O(3):Tm(3+)/Yb(3+) nanoparticles were synthesized using the Pechini-type sol-gel method, and their surfaces were modified with amino or carboxylic functional groups using ligand-capped and ligand-exchanging methods. The nanoparticles with modified surfaces were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and zeta potential (ζ), and their photoluminescence was studied by fluorescence spectrophotometry. The results indicate that the upconversion fluorescence of amine- and carboxyl-modified nanoparticles was enhanced after the surfaces of nanoparticles were modified. Compared to the upconversion fluorescence intensity of non-modified nanoparticles, the upconversion fluorescence intensities of amine- and carboxyl-modified nanoparticles were enhanced by 9.4 and 1.4 times, respectively. These results are attributed to the formation of the chemical bonds between Y(2)O(3):Tm(3+)/Yb(3+) core and non-crystalline SiO(2) shell via Y-O-Si bridges, which activate the 'dormant' Tm(3+)/Yb(3+) ions on the surfaces of nanoparticles. The results of the solubility investigations for amine- and carboxyl-modified nanoparticles indicate that severe aggregation can be weakened by adhering amino or carboxylic functional groups to the surfaces of nanoparticles. It is therefore concluded that the good hydrophilicity resulting from active functional groups in solutions and more intense upconversion fluorescence enable the doped core-shell nanoparticles to have great potential to be used as fluorescence biolabels in the future.

Identification on Mantle Cell Lymphoma Using CD20 and CD5 Coupled Upconversion Fluorescent Nanoprobes

“…The upconversion enhancement mechanism is approximatively similar to those of the core-shell type upconversion nanoparticles from our previous works [52][53][54] and is simply explained in supplemental data III.…”

Preparation and luminescence properties of monodisperse silica/aminosilane-coated Y2O3:Yb,Ho upconversion nanoparticles

“…There exists a need to develop a simple but effective method that will allow the secondary nucleation of silica particles to be avoided when applying silica coatings Because thick shells will prevent upconversion nanocrystals from behaving as bioprobes [22], only the effect of thin shells on the luminescence properties of Y-Y-H has been investigated. As shown in Figure 3 Recently, Lü et al [20,21] reported that in addition to the decrease of surface defects, a coating could also change the crystal field around the dopant ions at the surface of the nanoparticles. However, it is thought that the silica/aminosilane coating used herein has little influence on the crystal field around the dopant ions at the surface because the position and shape of the emission bands do not change upon addition of the coating (see Figure 3) [32,33].…”

“…Yttria-based upconversion nanocrystals (YUNs) are well known as an excellent candidates for upconversion fluorescent bioprobes because of their favorable chemical and thermal stability, nontoxicity and high emissive intensity [12][13][14][15][16][17][18][19][20][21]. However, unmodified YUNs tend to agglomerate in water and lack surface groups capable of coupling biomolecules, which limits their application in bioassays.…”

“…However, unmodified YUNs tend to agglomerate in water and lack surface groups capable of coupling biomolecules, which limits their application in bioassays. Various methods have been developed to solve these problems *Corresponding author (email: whcao@online.ln.cn) [17][18][19][20][21], among which surface coating the YUNs with silica and/or siloxane layers is the simplest and effective method. To date, the silica or silica/siloxane layers coated on the aggregated YUNs are relatively thick (more than 20 nm), and the particles coated are larger than 100 nm.…”

A facile single-step procedure for the synthesis of luminescent Ln3+:YVO4 (Ln=Eu or Er+Yb)-silica nanocomposites

“…Moreover, it has been reported that the efficiency of the Ln emission processes and photostability may be also improved by the silica layer, which minimises the quenching of the excited states in the Ln cations located on the nanoparticles surface through interaction with surface OH groups [7] and [8]. Usually, these lanthanide nanophosphors-silica composites are prepared by different liquid phase procedures [4], [5] and [6], which involve an initial synthesis and purification of the luminescent nanoparticles and in a second stage, the surface precipitation of the silica layers.…”