Yttrium-Doped Iron Oxide Nanoparticles for Magnetic Hyperthermia Applications.

Magnetic nanoparticles of Fe3O4 doped by different amounts of Y3+ (0, 0.1, 1, and 10%) ions were designed to obtain maximum heating efficiency in magnetic hyperthermia for cancer treatment. Single-phase formation was evident by X-ray diffraction measurements. An improved magnetization value was obtained for the Fe3O4 sample with 1% Y3+ doping. The specific absorption rate (SAR) and intrinsic loss of power (ILP) values for prepared colloids were obtained in water. The best results were estimated for Fe3O4 with 0.1% Y3+ ions (SAR = 194 W/g and ILP = 1.85 nHm2/kg for a magnetic field of 16 kA/m with the frequency of 413 kHz). The excellent biocompatibility with low cell cytotoxicity of Fe3O4:Y nanoparticles was observed. Immediately after magnetic hyperthermia treatment with Fe3O4:0.1%Y, a decrease in 4T1 cells' viability was observed (77% for 35 µg/mL and 68% for 100 µg/mL). These results suggest that nanoparticles of Fe3O4 doped by Y3+ ions are suitable for biomedical applications, especially for hyperthermia treatment.

Structural, optical and magnetic properties of Y3-0.02-xEr0.02Yb x Al5O12 (0 < x < 0.20) nanocrystals: effect of Yb content.

The paramagnetic Y3-0.02-x Er0.02Yb x Al5O12 (x = 0.02, 0.06, 0.10, 0.12, 0.18, 0.20) nanocrystals (NCs) were synthesized by the microwave-induced solution combustion method. The XRD, TEM and SEM techniques were applied to determine the NCs' structures and sizes. The XRD patterns confirmed that the NCs have for the most part a regular structure of the Y3Al5O12 (YAG) phase. The changes of the distance between donor Yb3+ (sensitizer) and acceptor Er3+ (activator) were realized by changing the donor's concentration with a constant amount of acceptor. Under 980 nm excitation, at room temperature, the NCs exhibited strong red emission near 660 and 675 nm, and green upconversion emission at 550 nm, corresponding to the intra 4f transitions of Er3+ (4F9/2, 2H11/2, 4S3/2) â†’ Er3+ (4I15/2). The strongest emission was observed in a sample containing 18% Yb3+ ions. The red and green emission intensities are respectively about 5 and 12 times higher as compared to NCs doped with 2% of Yb3+. In order to prove that the main factor responsible for the increase of the upconversion luminescence efficiency is reduction of the distance between Yb3+ and Er3+, we examined, for the first time the influence of hydrostatic pressure on luminescence and luminescence decay time of the radiative transitions inside donor ion. The decrease of both luminescence intensity and luminescence decay times, with increasing hydrostatic pressure was observed. After applying hydrostatic pressure to samples with e.g. 2% and 6% Yb3+, the distance between the donor and acceptor decreases. However, for higher concentrations of the donor, this distance is smaller, and this leads to the effective energy transfer to Er3+ ions. With increasing pressure, the maximum intensity of near infrared emission is observed at 1029, 1038 and 1047 nm, what corresponds to 2F5/2 â†’ 2F7/2 transition of Yb3+.

Luminescent-Magnetic Cellulose Fibers, Modified with Lanthanide-Doped Core/Shell Nanostructures.

Novel luminescent-magnetic cellulose microfibers were prepared by a dry-wet spinning method with the use of N-methylmorpholine-N-oxide. The synthesized luminescent-magnetic core/shell type nanostructures, based on the lanthanide-doped fluorides and magnetite nanoparticles (NPs)-Fe3O4/SiO2/NH2/PAA/LnF3, were used as nanomodifiers of the fibers. Thanks to the successful incorporation of the bifunctional nanomodifiers into the cellulose structure, the functionalized fibers exhibited superior properties, that is, bright multicolor emission under UV light and strong magnetic response. By the use of the as-prepared fibers, the luminescent-magnetic thread was fabricated and used to sew and make a unique pattern in the glove material, as a proof of concept for advanced, multimodal cloths'/materials' protection against counterfeiting. The presence and uniform distribution of the modifier NPs in the polymer matrix were confirmed by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analysis (EDX). The concentration of the modifier NPs in the fibers was determined by inductively coupled plasma mass spectrometry, EDX, and magnetic measurements. The luminescence characteristics of the materials were examined by photoluminescence spectroscopy, and their magnetic field-responsive behavior was investigated by a superconducting quantum interference device.