Composite Silica Spheres with Magnetic and Luminescent Functionalities

Abstract

A new class of highly fluorescent, photostable, and magnetic core/shell nanoparticles in the submicrometer size range has been synthesized from a modified Stöber method combined with the layer‐by‐layer (LbL) assembly technique. Luminescent magnetic nanoparticles are prepared via two main steps. The first step involves controlled addition of tetraethoxysilane to a dispersion of Fe3O4/γ‐Fe2O3 nanoparticles, which are thereby homogeneously incorporated as cores into monodisperse silica spheres. The second step involves the LbL assembly of polyelectrolytes and luminescent CdTe quantum dots onto the surfaces of the silica‐coated magnetite/maghemite particles, which are finally covered with an outer shell of silica. These spherical particles have a typical diameter of 220 ± 10 nm and a saturation magnetization of 1.34 emu g–1 at room temperature, and exhibit strong excitonic photoluminescence. Nanoparticles with such a core/shell architecture have the added benefit of providing a robust platform (the outer silica shell) for incorporating diverse functionalities into a single nanoparticle.

Influence of quantum dot concentration on Förster resonant energy transfer in monodispersed nanocrystal quantum dot monolayers

“…[31][32][33] Artificially designed microparticles and nanoparticles with multiple functionality can be synthesized with the help of the LbL technique and have been proposed for applications in areas such as quantum-information processing, optoelectronics, or biotechnology. [34][35][36] As the LbL deposition allows for the positioning of layers in nanometer steps, it is also beneficial for the investigation of energy transfer processes 17,19,21,22 as well as the interaction of surface plasmons with QDs. [37][38][39] Previous research reported in the literature has shown that nanocrystal to nanocrystal energy transfer can be appropriately described using Förster resonant energy transfer theory despite the inhomogeneous broadening of the QD ensembles and their relatively large size compared to the typical Förster radii of 2-10 nm.…”

Enhanced oxidation resistance of hydrothermally-encapsulated CdS nanoparticles in SiO2-CeO2 matrices

“…The encapsulation of a secondary nano-sized phase, such as semiconductors, 19) metal nanocrystals 15) and nano-oxide, 1),2) by a thermally-stable phase is of great importance. The method presented in this research has the advantage in stabilizing nanomaterials to a higher temperature with a simple hydrothermal treatment.…”

Polymeric nanoparticles for optical sensing

“…Magnetic SNPs can be integrated with optical reporters for simultaneous cellular imaging and bioseparation, both for in vivo and in vitro applications (Corr et al, 2008;Hwang et al, 2010;Kim et al, 2008;Salgueiriño-Maceira et al, 2006). Likewise, paramagnetic iron oxide NPs and QDs can be embedded within the same polymeric matrix (Figure 7).…”