Preparation and Characterization of Near-Infrared Luminescent Bifunctional Core/Shell Nanocomposites

Abstract

Bifunctional nanocomposites with superparamagnetic and NIR luminescent properties were synthesized by a layer-by-layer and a modified Stöber method. Fe3O4 nanoparticles as the core were coated with NaYF4:Ln3+ (Ln = Nd, Er, Pr, or Ho) to form the first layer. Then, the second layer was coated with silica to improve the chemical stability and photostability. The X-ray diffraction patterns showed that a cubic spinel structure of Fe3O4 and the coexistence of a cubic and hexagonal structure of NaYF4 were obtained. Energy dispersive X-ray (EDX) spectroscopy analysis confirmed the core/shell structure of Fe3O4@NaYF4:Ln3+. Transmission electron microscopy images revealed that the bifunctional nanocomposites consisted of crystalline Fe3O4@NaYF4:Ln3+ cores and amorphous SiO2 shells, in a spherical shape with a narrow size distribution. Magnetic measurements showed that the obtained bifunctional nanocomposites exhibited superparamagnetic behavior. Emission spectra indicated that the bifunctional nanocomposites possessed a high near-infrared (NIR) luminescent intensity. Moreover, the hexagonal phase NaYF4:Ln3+ showed NIR emission 10 to 15 times stronger than the cubic phase.

2D l‐Di‐toluoyl‐tartaric acid Lanthanide Coordination Polymers: Toward Single‐component White‐Light and NIR Luminescent Materials

“…[22] The NIR emission spectrum of complex 4 (Figure 4a,p ink spectrum) exhibits an arrow band at 980 nm, which is assigned to the f-f transitions of . [23] To the best of our knowledge, NIR spectra of Er 3 + complexes exhibiting only two peaks around 950 nm and 1240 nm were seldom reported. Previously,a lmost all NIR luminescent spectra of Er [24] The NIR luminescent lifetimef or complexes 2-4 is in the order of 2 (4.6 ms) > 4 (4.0 ms) > 3 (1.0 ms).…”

Upconversion Nanoparticle-Based Nanocomposites

“…On the other hand, the size of the obtained core/shell hybrid nanostructure can be easily controlled below 100 nm, which increases the biocompatibility of the materials. So, we can extend this seedmediated growth method to the synthesis of the UCNPs-MNPs multi-functional nanocomposites [124][125][126]. Xia et al [124] synthesized new core/shell-structured NaYF4:Yb 3+ ,Tm 3+ @Fe x O y nanoparticles, with 20-nm Yb 3+ , Tm 3+ codoped NaYF 4 nanoparticles as a core, and 5-nm Fe x O y nanoparticles as a shell.…”

“…The second approach is based on combining upconversion nanoparticles and magnetic nanocrystals assisted by cross-linker [1,[121][122][123]. The third way is based on the seed-mediated growth method [124][125][126].…”

Luminescent magnetic particles: structures, syntheses, multimodal imaging, and analytical applications

“…However, the in vivo application of QDs is still under discussion due to the high inherent toxicity. The necessity of an adequate protecting matrix is known for a long time, and various solutions for this issue have been presented in literature [50,53,55,64,65]. The question is if a component consisting of highly toxic elements (Cd, Hg, Se, Te, In, As, Pb) will ever be approved or widely accepted for in vivo medical applications.…”

“…12). These luminescent nanocomposites were consequently coated with a thin silica layer, which rendered the LuMaPs biocompatible and stable [65]. Yang et al [66] coated YVO 4 :Eu onto pores in mesoporous, magnetic silica particles.…”