The Upconversion Luminescence of Ca3Sc2Si3O12:Yb3+,Er3+ and Its Application in Thermometry.

To develop novel luminescent materials for optical temperature measurement, a series of Yb3+- and Er3+-doped Ca3Sc2Si3O12 (CSS) upconversion (UC) phosphors were synthesized by the sol-gel combustion method. The crystal structure, phase purity, and element distribution of the samples were characterized by powder X-ray diffraction and a transmission electron microscope (TEM). The detailed study of the photoluminescence emission spectra of the samples shows that the addition of Yb3+ can greatly enhance the emission of Er3+ by effective energy transfer. The prepared Yb3+ and Er3+ co-doped CSS phosphors exhibit green emission bands near 522 and 555 nm and red emission bands near 658 nm, which correspond to the 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 transitions of Er3+, respectively. The temperature-dependent behavior of the CSS:0.2Yb3+,0.02Er3+ sample was carefully studied by the fluorescence intensity ratio (FIR) technique. The results indicate the excellent sensitivity of the sample, with a maximum absolute sensitivity of 0.67% K-1 at 500 K and a relative sensitivity of 1.34% K-1 at 300 K. We demonstrate here that the temperature measurement performance of FIR technology using the CSS:Yb3+,Er3+ phosphor is not inferior to that of infrared thermal imaging thermometers. Therefore, CSS:Yb3+,Er3+ phosphors have great potential applications in the field of optical thermometry.

Efficient Luminescence Enhancement of Mg2TiO4:Mn4+ Red Phosphor by Incorporating Plasmonic Ag@SiO2 Nanoparticles.

One of prospective ways for boosting efficiency of luminescent materials is their combination with noble metal nanoparticles. Collective, so-called plasmon, oscillations of surface electrons in a nanoparticle can resonantly interact with incident or fluorescent light and cause an increase in the light absorption cross section or radiative rate for an adjacent emitter. Plasmonic inorganic phosphors require gentle host crystallization at which added noble nanoparticles will not suffer from aggregation or oxidation. The prospective plasmonic Mg2TiO4:Mn4+ phosphor containing core@shell Ag@SiO2 nanoparticles is prepared here by spare low-temperature annealing of a sol-gel host precursor. It is revealed that Mn4+ luminescence nonmonotonously depends on the size and concentration of 40 and 70 nm silver nanoparticles. It is demonstrated that luminescence of the Mg2TiO4:Mn4+ phosphor can be up to a 1.5 times increase when Mn4+ excitation is supported by localized surface plasmon resonance in Ag@SiO2 nanoparticles.

White Light Emission and Enhanced Color Stability in a Single-Component Host.

Eu3+ ion can be effectively sensitized by Ce3+ ion through an energy-transfer chain of Ce3+-(Tb3+) n-Eu3+, which has contributed to the development of white light-emitting diodes (WLEDs) as it can favor more efficient red phosphors. However, simply serving for WLEDs as one of the multicomponents, the design of the Ce3+-(Tb3+) n-Eu3+ energy transfer is undoubtedly underused. Theoretically, white light can be achieved with extra blue and green emissions released from Ce3+ and Tb3+. Herein, the design of the white light based on these three multicolor luminescence centers has been realized in GdBO3. It is the first time that white light is generated via accurate controls on the Ce3+-(Tb3+) n-Eu3+ energy transfer in such a widely studied host material. Because the thermal quenching rates of blue, green, and red emissions from Ce3+, Tb3+, and Eu3+, respectively, are well-matched in the host, this novel white light exhibits superior color stability and potential application prospect.

Tunable Magnetization Dynamics through Solid-State Ligand Substitution Reaction.

The dimeric molecule [Dy2(acac)6(MeOH)2(bpe)]·bpe·2MeOH (1, acac = acetylacetonate, bpe = 1,2-bis(4-pyridyl)ethylene) undergoes a solid-state ligand substitution reaction upon heating, leading to the one-dimensional chain [Dy(acac)3(bpe)]n (2). This structural transformation takes advantage of the potential coordination of the guest bpe molecules present in 1. In both complexes the Dy(III) ions adopt similar octacoordinated D4d geometries. However, the different arrangement of the negatively charged and neutral ligands alters the direction of magnetic anisotropy axis and the energy states, thus resulting in largely distinct magnetization dynamics, as revealed by the CASSCF/RASSI calculations.