CeF3, CeF3:Tb3+, and CeF3:Tb3+/LaF3 (core/shell) nanoparticles were prepared by the polyol method
and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray
photoelectron spectra (XPS), UV−vis absorption spectra, photoluminescence (PL) spectra, and lifetimes.
The results of XRD indicate that the obtained CeF3, CeF3:Tb3+, and CeF3:Tb3+/LaF3 (core/shell)
nanoparticles crystallized well at 200 °C in diethylene glycol (DEG) with a hexagonal structure. The
TEM images illustrate that the CeF3 and CeF3:Tb3+ nanoparticles are spherical with a mean diameter of
7 nm. The growth of the LaF3 shell around the CeF3:Tb3+ core nanoparticles resulted in an increase of
the average size (11 nm) of the nanopaticles as well as in a broadening of their size distribution. These
nanocrystals can be well-dispersed in ethanol to form clear colloidal solutions. The colloidal solutions of
CeF3 and CeF3:Tb3+ show the characteristic emission of Ce3+ 5d−4f (320 nm) and Tb3+
5D4−7FJ (J =
6−3, with 5D4−7F5 green emission at 542 nm as the strongest one) transitions, respectively. The emission
intensity and lifetime of the CeF3:Tb3+/LaF3 (core/shell) nanoparticles increased with respect to those of
CeF3:Tb3+ core particles. This indicates that a significant amount of nonradiative centers existing on the
surface of CeF3:Tb3+ nanoparticles can be eliminated by the shielding effect of LaF3 shells. Finally, the
energy transfer from Ce3+ to Tb3+ was investigated in CeF3:Tb3+ nanoparticles in detail.
In the Letter, we demonstrate an improved electroless plating method for the synthesis of bimetallic shell particles. The procedure involves a combination of surface reaction, seeding growth, and removal of supporting cores. We modified ammonical AgNO3 in ethanol with a controlled amount of HCHO in the seeding process and a uniform and relatively dense coverage of silver nanoparticle seeds on colloid cores was achieved. Following the second kind of metal plating, we extended this method to prepare continuous bimetallic core-shell and hollow particles with a submicrometer diameter. The morphologies of the bimetallic Cu/Ag and Pt/Ag particles were studied with transmission electron microscopy and scanning electron microscopy, and their crystallinity and chemical composition were confirmed by X-ray diffraction. The prepared materials may be of applied value in areas such as catalysis, optics, and plasmonics.
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