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Gd2O3:1% Er3+, 18% Yb3+, x% Mg2+ (x = 0; 2.5; 4; 5; 6; 8;10; 20; 25; 50) and Gd2O3:1% Er3+, 18% Yb3+, 2,5% Mg2+, y% Li+ (y = 0.5–2.5) nanoparticles were synthesized by homogenous precipitation method and calcined at 900 °C for 3 h in air atmosphere. Powder x-ray diffraction, scanning electron microscopy, cathodoluminescence, transmission electron microscopy, energy dispersive x-ray spectroscopy and photoluminescence techniques were employed to characterize the obtained nanoparticles. We observed a 8-fold increase in red luminescence for samples suspended in DMSO solution for 2.5% of Mg2+ doping. The x-ray analysis shows that for the concentration of 2.5% Mg, the size of the crystallites in the NPs is the largest, which is mainly responsible for the increase in the intensity of the upconversion luminescence. But the addition of Li+ ions did not improve the luminescence of the upconversion due to decreasing of crystallites size of the NPs. Synthesized nanomaterials with very effective upconverting luminescence, can act as luminescent markers in in vivo imaging. The cytotoxicity of the nanoparticles was evaluated on the 4T1 cell line for the first time. [ABSTRACT FROM AUTHOR]

Self-aligned and equal-spaced zinc oxide (ZnO) nanotube arrays were fabricated with anodic aluminum oxide (AAO)-assisted growth and the ALD technique. The near band-edge (NBE) emission was strongly affected by the nanotube's geometrical parameters, such as a packing density and thickness of the nanotube walls. The NBE emission was further enhanced with Al 2 O 3 coating. The effect was analyzed by X-ray photoelectron spectroscopy (XPS) and ascribed to the surface defect passivation and a ZnAl 2 O 4 spinel formation. The NBE emission enhancement was greater in ZnO nanotubes with thicker walls. A smaller UV enhancement factor was explained by less uniform and integral Al 2 O 3 coverage of the ZnO nanotubes with thinner walls; this, possibly induced a variation of the Al 2 O 3 refractive index along the nanotubes. As a result, the optical conditions at the ZnO/Al 2 O 3 /air interfaces was changed and the light extraction efficiency was reduced in the latter samples. [ABSTRACT FROM AUTHOR]

Gd 2 O 3 :1% Er 3+ , 18% Yb 3+ , x % Mg 2+ ( x  = 0; 2.5; 4; 5; 6; 8;10; 20; 25; 50) and Gd 2 O 3 :1% Er 3+ , 18% Yb 3+ , 2,5% Mg 2+ , y % Li + ( y  = 0.5-2.5) nanoparticles were synthesized by homogenous precipitation method and calcined at 900 °C for 3 h in air atmosphere. Powder x-ray diffraction, scanning electron microscopy, cathodoluminescence, transmission electron microscopy, energy dispersive x-ray spectroscopy and photoluminescence techniques were employed to characterize the obtained nanoparticles. We observed a 8-fold increase in red luminescence for samples suspended in DMSO solution for 2.5% of Mg 2+ doping. The x-ray analysis shows that for the concentration of 2.5% Mg, the size of the crystallites in the NPs is the largest, which is mainly responsible for the increase in the intensity of the upconversion luminescence. But the addition of Li + ions did not improve the luminescence of the upconversion due to decreasing of crystallites size of the NPs. Synthesized nanomaterials with very effective upconverting luminescence, can act as luminescent markers in in vivo imaging. The cytotoxicity of the nanoparticles was evaluated on the 4T1 cell line for the first time., (Creative Commons Attribution license.)

Nanostructures as color-tunable luminescent markers have become major, promising tools for bioimaging and biosensing. In this paper separated molybdate/Gd 2 O 3 doped rare earth ions (erbium, Er 3+ and ytterbium, Yb 3+ ) core-shell nanoparticles (NPs), were fabricated by a one-step homogeneous precipitation process. Emission properties were studied by cathodo- and photoluminescence. Scanning electron and transmission electron microscopes were used to visualize and determine the size and shape of the NPs. Spherical NPs were obtained. Their core-shell structures were confirmed by x-ray diffraction and energy-dispersive x-ray spectroscopy measurements. We postulated that the molybdate rich core is formed due to high segregation coefficient of the Mo ion during the precipitation. The calcination process resulted in crystallization of δ/ξ (core/shell) NP doped Er and Yb ions, where δ-gadolinium molybdates and ξ-molybdates or gadolinium oxide. We confirmed two different upconversion mechanisms. In the presence of molybdenum ions, in the core of the NPs, Yb 3+ -[Formula: see text] (∣ 2 F 7/2 , 3 T 2 〉) dimers were formed. As a result of a two 980 nm photon absorption by the dimer, we observed enhanced green luminescence in the upconversion process. However, for the shell formed by the Gd 2 O 3 :Er, Yb NPs (without the Mo ions), the typical energy transfer upconversion takes place, which results in red luminescence. We demonstrated that the NPs were transported into cytosol of the HeLa and astrocytes cells by endocytosis. The core-shell NPs are sensitive sensors for the environment prevailing inside (shorter luminescence decay) and outside (longer luminescence decay) of the tested cells. The toxicity of the NPs was examined using MTT assay.

It is shown that the growth of II-VI diluted magnetic semiconductor nanowires is possible by the catalytically enhanced molecular beam epitaxy (MBE). Zn(1-x)MnxTe NWs with manganese content up to x=0.60 were produced by this method. X-ray diffraction, Raman spectroscopy, and temperature dependent photoluminescence measurements confirm the incorporation of Mn(2+) ions in the cation substitutional sites of the ZnTe matrix of the NWs.