Structure, Luminescence, and Dynamics of Eu₂O₃ Nanoparticles in MCM-41

Abstract

The structure, luminescence spectroscopy, and lifetime decay dynamics of Eu 2 O 3 nanoparticles formed in MCM-41 have been investigated. Both X-ray diffraction and high-resolution transmission electron microscopic observations indicate that Eu 2 O 3 nanoparticles of monoclinic structure are formed inside channels of MCM-41 by heating at 140 °C. However, heat treatment at 600 or 700 °C causes migration of Eu 2 O 3 from the MCM-41 channels, forming nanoparticles of cubic structure outside the MCM-41 channels. After heating to 900 °C, some of the cubic Eu 2 O 3 particles change to monoclinic Eu 2 O 3 , and the MCM-41 structure breaks down and a different or disordered phase is formed. The feature of the hypersensitive 5 D 0 f 7 F 2 emission profile of Eu 3+ is used to follow the structural changes. In the luminescence spectrum of the sample prepared at 140 °C, the emission spectrum is dominated by peaks at 615 and 623 nm, while in the other samples a peak at 612 nm is prevalent. Photoluminescence lifetimes show the existence of short (<1 µs) and long (microsecond to millisecond) components for each sample. The fast decay is attributed to quenching by surface states of the nanoparticles or energy transfer to the MCM-41, while the longer time decays show the effects of concentration quenching. The monoclinic sample prepared at 140 °C shows a higher luminescence intensity than the cubic samples or the bulk powder. These observations indicate that MCM-41 as a template can be used for making and stabilizing monoclinic rare earth oxides, which normally are stable only at high temperatures and high pressures. More importantly, the nanophase Eu 2 O 3 /MCM-41 composite materials formed at low temperatures might represent a new type of efficient luminescence material with fast response, with potential applications in lighting and displays.

Effect of annealing temperature on luminescence of Eu3+ ions doped nanocrystal zirconia

“…Chen et al thought the difference of 5 D 0 ! 7 F 2 emission peaks in relative positions was due to the difference of the effects of the crystal field perturbation on the individual f-f transitions [19]. The fluorescence intensity ratios I of 604 nm emission to 612 nm emission increase and then decrease with annealing temperature increase.…”

Local structure in CeO2 and CeO2–ZrO2 nanoparticles probed by Eu luminescence

“…We also note that the characteristic phonon modes of cubic Eu 2 O 3 phase, characterized by an intense mode around 340 cm −1 [27] were not detected. Finally, siteselective luminescence measurements do not evidence any trace of Eu 2 O 3 , which is generally characterized by strong emission around 618 nm [28]. Since the sensitivity of our set-up to luminescence signal of Eu-CeO 2 is around 0.05% doping level, it is likely that the presence of Eu 2 O 3 , if any, is below this value.…”

Luminescent Properties of BaSi2O5:Eu2+Phosphor Film Fabricated by Spin-Coating of Ba-Eu Precursor on SiO2Glass

“…Chen et. al reported on appearance of pure monoclinic Eu2O3 formed at low temperatures and pressure in air [17]. BaO phases are not found in spin-coated BaO:Eu film.…”