Magnetic nanoparticles of Fe 3 O 4 doped by different amounts of Y 3+ (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 Fe 3 O 4 sample with 1% Y 3+ 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 Fe 3 O 4 with 0.1% Y 3+ ions (SAR = 194 W/g and ILP = 1.85 nHm 2 /kg for a magnetic field of 16 kA/m with the frequency of 413 kHz). The excellent biocompatibility with low cell cytotoxicity of Fe 3 O 4 :Y nanoparticles was observed. Immediately after magnetic hyperthermia treatment with Fe 3 O 4 :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 Fe 3 O 4 doped by Y 3+ ions are suitable for biomedical applications, especially for hyperthermia treatment.
Inorganic nanomaterials able to generate reactive oxygen species (ROS) are promising components for modern medical applications. Activated by near-infrared light, up-converting b-NaYF 4 doped with Er 3+ -Yb 3+ and Tm 3+ -Yb 3+ pair ions nanoparticles (UCNPs), have a wide range of applications in biological imaging as compared to traditional reagents excited by ultra-violet or visible light. We analysed the green-red and the blue-red luminescence to explain the mechanism of the upconversion depended on the surface condition. The influence of SiO 2 coating on the cytotoxicity of the as-produced UCNPs towards HeLa cancer cells was reported. We demonstrated a possibility of a direct UCNPs application to photodynamic therapy, without need to attach additional molecules to their surface. The presence of Tm 3+ -Yb 3+ pair ions, thus ROS generation capability, renders the SiO 2 shell coated nanoparticles to become potentially useful theranostic agent.
Water-soluble upconversion nanoparticles (UCNPs), based on polyvinylpyrrolidone (PVP)-coated NaYF:Er,Yb,Gd, with various concentrations of Gd ions and relatively high upconversion efficiencies, were synthesized. The internalization and cytotoxicity of the thus obtained UCNPs were evaluated in three cell lines (HeLa, HEK293 and astrocytes). No cytotoxicity was observed even at concentrations of UCNPs up to 50 μg ml. The fate of the UCNPs within the cells was studied by examining their upconversion emission spectra with confocal microscopy and confirming these observations with transmission electron microscopy. It was found that the cellular uptake of the UCNPs occurred primarily by clathrin-mediated endocytosis, whereas they were secreted from the cells via lysosomal exocytosis. The results of this study, focused on the mechanisms of the cellular uptake, localization and secretion of UCNPs, demonstrate, for the first time, the co-localization of UCNPs within discrete cell organelles.
Bulk semiconductors doped with copper ions have been heavily studied and employed as phosphors in early display technologies. The properties of copper-doped semiconductor nanostructures are much less studied. In particular, the spin properties of photoexcited carriers in copper-doped colloidal quantum dots are virtually unknown. Understanding the spin processes in these materials can lead to applications in novel information technologies. Moreover, the spin structure of the excited states in Cu-doped dots is analogous to that of Cu(I) molecular complexes, which are widely studied with respect to applications in organic light-emitting diodes. Thus, understanding the spin properties of Cu-doped dots can have broad ramifications for other material systems. In this work, we study the dynamics of spin relaxation processes in photoexcited Cu-doped CdSe colloidal quantum dots at helium temperatures and in magnetic fields up to 8 T. We find that a spin polarization is induced by application of the magnetic field. However, this polarization develops extremely slowly: about 2 orders of magnitude slower than in reference Cu-free CdSe dots, at time scales on the order of 1 μs at 2 K and fields below 1 T. As the magnetic field and/or temperature is increased the spin relaxation accelerates, but in the entire field and temperature range remains much slower than in CdSe dots. We discuss various mechanisms responsible for the development of the spin polarization and conclude that the slow spin dynamics is related to the nature of the photoexcited state, which limits the carrier interaction with uncompensated spins at the dot surface. Our results thus underline the role of surface states in spin relaxation processes in colloidal quantum dots in general.
Nanostructures as color-tunable luminescent markers have become major, promising tools for bioimaging and biosensing. In this paper separated molybdate/GdO doped rare earth ions (erbium, Er and ytterbium, Yb) 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-[Formula: see text] (∣F, T〉) 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 GdO: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.
Introducing copper impurities to semicoductor quantum dots (QDs) lead to an appearance of a new photoluminescence (PL) band related to the recombination of a delocalized conduction band electron and a hole trapped at the copper d orbital. This new PL band is characterized by a large line width, large Stokes shift, and a multiexponential temporal decay, with origins not well understood. In this work, we employ density functional theory to investigate the impact of the copper dopant location inside a QD on absorption and PL properties. We find that impurities incorporated closer to the surface give rise to PL transitions at lower energies, with lower probabilities, and larger Stokes shifts than impurities at the QD center. We show that the effect arises as a result of site-dependent distortion of the dopant vicinity: larger distortions occur for impurities closer to the surface and result in stronger energy relaxations. The conclusions from the theoretical calculations are supported by measurements of PL dynamics. Our results provide a novel interpretation of the heterogeneous optical properties of Cu-doped QDs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.