Er Nanoparticles Research Articles

Maximizing Upconversion Luminescence of Co-Doped CaF₂:Yb, Er Nanoparticles at Low Laser Power for Efficient Cellular Imaging.

Upconversion nanoparticles (UCNPs) are well-reported for bioimaging. However, their applications are limited by low luminescence intensity. To enhance the intensity, often the UCNPs are coated with macromolecules or excited with high laser power, which is detrimental to their long-term biological applications. Herein, we report a novel approach to prepare co-doped CaF2:Yb3+ (20%), Er3+ with varying concentrations of Er (2%, 2.5%, 3%, and 5%) at ambient temperature with minimal surfactant and high-pressure homogenization. Strong luminescence and effective red emission of the UCNPs were seen even at low power and without functionalization. X-ray diffraction (XRD) of UCNPs revealed the formation of highly crystalline, single-phase cubic fluorite-type nanostructures, and transmission electron microscopy (TEM) showed co-doped UCNPs are of ~12 nm. The successful doping of Yb and Er was evident from TEM-energy dispersive X-ray analysis (TEM-EDAX) and X-ray photoelectron spectroscopy (XPS) studies. Photoluminescence studies of UCNPs revealed the effect of phonon coupling between host lattice (CaF2), sensitizer (Yb3+), and activator (Er3+). They exhibited tunable upconversion luminescence (UCL) under irradiation of near-infrared (NIR) light (980 nm) at low laser powers (0.28-0.7 W). The UCL properties increased until 3% doping of Er3+ ions, after which quenching of UCL was observed with higher Er3+ ion concentration, probably due to non-radiative energy transfer and cross-relaxation between Yb3+-Er3+ and Er3+-Er3+ ions. The decay studies aligned with the above observation and showed the dependence of UCL on Er3+ concentration. Further, the UCNPs exhibited strong red emission under irradiation of 980 nm light and retained their red luminescence upon internalization into cancer cell lines, as evident from confocal microscopic imaging. The present study demonstrated an effective approach to designing UCNPs with tunable luminescence properties and their capability for cellular imaging under low laser power.

Ultrathin Polyelectrolyte Multilayer Films with Silver Nanoparticles as a Potential Antibacterial Coating

Silv er nanoparticles (AgNPs) are already used as antibacterial agents for medical devices and food packaging materials. However, concerns about its toxicity still exist. AgNPs can be incorporated into ultrathin polyelectrolyte multilayer (PEM) films to minimize this risk. With PEMs, full surface coverage can be achieved with minimal AgNPs, minimizing human exposure. In this study, a simple protocol to fabricate ultrathin PEM/AgNP films using sodium ascorbate as a reductant was developed. The effects of the number of bilayers and ionic strength (0.05 to 0.50 M) on film thickness and amount of AgNPs were investigated. UV/VIS spectra show that increasing the number of bilayers from 1 to 5 would lead to a corresponding increase in film thickness and amount of synthesized AgNPs. Thicker layers and more AgNPs were deposited when the films were fabricated under higher ionic strengths. Films with thicknesses ranging from 15.67 to 87.13 nm were fabricated. The sizes of the incorporated AgNPs were between 54.32 and 259.26 nm, as characterized by scanning electron microscopy. All films were stable when submerged in water for 240 h, suggesting the migration of Ag/Ag+ from the films was minimal. The antibacterial efficacy of the films against Staphylococcus aureus was also assessed. Only the PEM/AgNP films fabricated with the highest salt concentration (0.50 M) showed antibacterial activity under resazurin assay. However, the Kirby Bauer method showed inhibition zones for all films fabricated under all salt concentrations, indicating antibacterial activity at the interface of the bacterial lawn and the films, even with the slow migration of Ag/Ag+. Thus, PEM/AgNP films have the potential to be used as an antibacterial coating.

Enhanced performance of perovskite solar cell via up-conversion YLiF4:Yb, Er nanoparticles

We report a simple and effective method for producing lanthanide ion-doped lithium-fluoride-based nanocrystals (YLiF4). We utilized those nanoparticles for up-conversion in fabricated perovskite solar cells. The obtained results shows that the up-conversion YLiF4:Yb, Er nanoparticles improve alignment of energy levels at interface between titanium dioxide and perovskite layer. This increases power conversion efficiency of fabricated perovskite solar cells from 19.45 % to 21.32 %. To enhance comprehension of the recombination mechanism and its correlation with the conduction band offset and defects, device models are additionally integrated into the SCAPS simulator. Subsequently, the obtained J-V simulation outcomes exhibit a favorable concordance with the experimental observations.

Toxicity of Large and Small Surface-Engineered Upconverting Nanoparticles for In Vitro and In Vivo Bioapplications.

In this study, spherical or hexagonal NaYF4:Yb,Er nanoparticles (UCNPs) with sizes of 25 nm (S-UCNPs) and 120 nm (L-UCNPs) were synthesized by high-temperature coprecipitation and subsequently modified with three kinds of polymers. These included poly(ethylene glycol) (PEG) and poly(N,N-dimethylacrylamide-co-2-aminoethylacrylamide) [P(DMA-AEA)] terminated with an alendronate anchoring group, and poly(methyl vinyl ether-co-maleic acid) (PMVEMA). The internalization of nanoparticles by rat mesenchymal stem cells (rMSCs) and C6 cancer cells (rat glial tumor cell line) was visualized by electron microscopy and the cytotoxicity of the UCNPs and their leaches was measured by the real-time proliferation assay. The comet assay was used to determine the oxidative damage of the UCNPs. An in vivo study on mice determined the elimination route and potential accumulation of UCNPs in the body. The results showed that the L- and S-UCNPs were internalized into cells in the lumen of endosomes. The proliferation assay revealed that the L-UCNPs were less toxic than S-UCNPs. The viability of rMSCs incubated with particles decreased in the order S-UCNP@Ale-(PDMA-AEA) > S-UCNP@Ale-PEG > S-UCNPs > S-UCNP@PMVEMA. Similar results were obtained in C6 cells. The oxidative damage measured by the comet assay showed that neat L-UCNPs caused more oxidative damage to rMSCs than all coated UCNPs while no difference was observed in C6 cells. An in vivo study indicated that L-UCNPs were eliminated from the body via the hepatobiliary route; L-UCNP@Ale-PEG particles were almost eliminated from the liver 96 h after intravenous application. Pilot fluorescence imaging confirmed the limited in vivo detection capabilities of the nanoparticles.

Hierarchically synthesis of M@CeO2 (M = Ba, Er) nanoparticles for Antibacterial efficacy

Cerium oxide fine particles injected with metallic nanoparticles were produced using the co-precipitation method and characterized using various techniques such as XRD, SEM, FTIR, UV–Vis, and PL. Both injected and non-doped ceria nanoparticles exhibited a crystallographic structure similar to calcium fluoride. The nanoparticles ranged in size from 25 to 74 nm and had an inconsistent spherical shape. EDX analysis confirmed the presence of Erbium (Er) and Barium (Ba) in the ceria nanocrystal lattices. UV–Vis experiments showed that the optical band gap efficiency of purified CeO2 NPs was 3.1 eV, while doped CeO2 NPs had an energy level of 2.9 eV. The nanoparticles exhibited a sharp emission peak at approximately 347 nm. The synthesized CeO2 NPs showed antibacterial activity against Gram-positive and Gram-negative bacteria, including Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Overall, the results demonstrate that the doping of ceria nanoparticles with metallic nanoparticles can significantly enhance their antibacterial properties. This research paves the way for the development of novel antibacterial agents with potential applications in various fields such as medicine, food packaging, and water treatment.

Laser-induced changes on the upconversion luminescence properties of BiF3:Yb,Er nanoparticles

BiF3 nanoparticles doped with Yb3+ and Er3+ ions in varying ratios were prepared by co-precipitation method and its upconversion luminescence (UCL) properties were investigated in detail before and after high-intensity laser treatment. Green-to-red ratio (GRR) of luminescence from cubic-BiF3:Yb,Er nanoparticles is found to increase with an increase in laser power for as prepared sample. Unlike this, for conventional Yb,Er doped upconversion nanoparticles (UCNPs) such as cubic NaYF4:Yb,Er and hexagonal-NaYF4:Yb,Er, a decrease in GRR values is observed with an increase in laser power. This has been explained based on the reduced extent of Er3+-Er3+ interaction in BiF3:Yb,Er nanoparticles compared to that existing in cubic and hexagonal forms of NaYF4:Yb,Er, nanoparticles. Reduced interaction is brought about by higher lattice parameter of BiF3 host compared to the NaYF4 host which leads to a lesser extent of cross-relaxation in the former host thereby favoring the population of 4S3/2 and 2H11/2 levels of Er3+. Effect of high-intensity laser (180W/cm2) irradiation on BiF3:Yb,Er nanoparticles resulted in an irreversible five-fold increase in upconversion luminescence intensity and this is attributed to combined effect of partial conversion of BiF3 to cubic Bi2O3 and removal of adsorbed water molecules. These inferences are confirmed by XRD and TEM measurements carried out on laser-treated sample. Improved luminescence intensity from the laser-treated sample is also confirmed by the high-contrast clear images obtained from impressions made using high-intensity laser irradiation on BiF3:Yb,Er nanoparticles. BiF3:Yb,Er nanoparticles showed an excellent thermal sensitivity of 0.3% K−1 at room temperature and the value is comparable with that of conventional β-NaYF4:Yb,Er nanoparticles.

Opto-magnetic nanoparticles with upconverting properties for optical imaging and photothermal therapies

Multifunctional opto-magnetic nanoparticles (NPs) with upconverting properties were designed for cancer detection and treatment. The upconversion was achieved from NaYF4 doped by 20 %Yb and 2 % Er nanoparticles (UCNPs). The UCNPs were coated by a thin SiO2 shell and decorated with 6 nm magnetic Fe3O4 that resulted in the formation of NaYF4:Yb,Er@SiO2@Fe3O4 multifunctional nanoplatform. The connection between UCNPs and Fe3O4 NPs was proved by SEM, TEM, SQUID, absorption, and luminescence techniques. The specific absorption rate (SAR) values for prepared colloids were calculated for colloidal suspension of heterostructures after 808 and 880 nm laser irradiation as a function of lasers power. The highest conversion effectiveness was obtained for an 880 nm light source with 1600 mW (SAR = 87 W/g). The low MDA-MB-231 cells cytotoxicity of NaYF4:Yb,Er@SiO2@Fe3O4 NPs was observed (up to 500 µg/ml). At the same time, a strong upconverting signal after 980 nm of excitation was observed from the sites of the cells without autofluorescence from its components. This phenomenon with relatively good SAR parameters suggested that multifunctional nanoconstructs for simultaneous cancer detection (imaging) and photothermal therapy have been successfully obtained.

Growth and luminescence characteristics of LiYF4: Yb,Er nanoparticles

The morphology and size of LiYF4:Yb,Er nanoparticles were controlled using an automatic nanomaterial synthesizer by changing the reaction time at high temperature. It was found that the nanoparticles underwent a growth and change process from small to large and then to small, and then remained at a basically stable size, reflecting the different growth stages of the nanoparticles, such as nucleation, growth, phase transition, and internal Ostwald ripening, etc. XRD analyses showed that LiF nanocrystals were first formed during the reaction process, and then all the products were converted into LiYF4 nanocrystals. Under the excitation of a 980 nm laser, the LiYF4:Yb,Er nanoparticles showed regular downconversion and upconversion luminescence properties, which was basically consistent with the regularity of nanocrystal growth. The experimental results showed that the upconversion luminescence and downconversion luminescence intensities of nanocrystals increasd rapidly when the synthesis time was between 0 and 50 min, and they increased slowly after the synthesis time exceeded 50 min.

Development of a novel flexible thin PWO(Er)/ZnO(Ag) nanocomposite for ionizing radiation sensing

Radiation dosimetry is an essential aspect of modern radiotherapy. Optically stimulated luminescence (OSL) dosimetry is a promising technique that uses materials to measure radiation doses. However, current OSL dosimeters are limited in their ability to provide comprehensive validation of spatial dose distributions, particularly in flexibility radiation sensitivity. In this regard, a novel flexible PWO(Er)/ZnO(Ag) nanocomposite sensor has been developed by a solvothermal procedure and its ionization radiation responses were investigated under UV, proton, laser 980 nm, and 241Am sources. The calculated alpha detection efficiency showed that the prepared PWO(Er)/ZnO(Ag) sensor is highly sensitive to alpha radiation (99.6 %) with good stability/repeatability and linear response. According to the Photo/Ionoluminescence study, the doped dual nanocomposite sample showed the strongest blue, green, and yellow emissions at room temperature compared with pure and single doped samples with an exciton lifetime of τ = 143.30 ±0.07 μs. The XRD, FTIR, Raman, and EDX results indicated that the prepared pure and doped nanocomposites have two-phase compositions of PWO and ZnO and related chemical compounds/elements in the nanocomposite structure. The morphologies of the PWO and PWO(Er) nanoparticles (NPs) were mostly cubic and heterogeneous with average particle sizes of 125 and 82 nm. ZnO and ZnO(Ag) had hexagonal, spherical, and rod-shaped particles with typical particle diameters of 130 and 90 nm, respectively. Our results indicate the prepared luminescent nanocomposites are transparent, flexible, highly stable, highly sensitive to ionizing radiation, and have the potential for practical use in optoelectronics and medical imaging in the future.

Effect of heat treatment temperature on the morphology and upconversion properties of LaF3:Yb,Er nanoparticles

LaF3:5%Yb3+,0.5%Er3+ upconverting nanoparticles were synthesized with co-precipitation method and heat treated at temperatures 300–600 °C. The morphology of the particles was characterized by high-resolution transmission electron microscopy coupled with energy-dispersive spectrometry and dynamic light scattering. Crystal structure was studied by X-ray diffraction (XRD), and thermal behaviour was investigated by simultaneous thermogravimetry and differential thermal analysis (TG/DTA). Upconversion behaviour was studied in detail by fluorescence spectroscopy, with 980 nm excitation. Particle sizes increased with increasing heat treatment temperature, and samples showed significant aggregation above 500 °C. Hexagonal LaF3 crystal structure was identified for all samples, with increased crystallinity after heat treatment at 400 °C, which was corroborated with TG/DTA results. XRD and energy-dispersive spectrometry results revealed that at higher temperatures new crystal phases formed, as some Yb3+ and Er3+ dopant ions segregated into new nanocrystals, made of, for example, YbOF and YbOOH, which caused a significant decrease in the upconversion emission of the samples. The highest upconversion emission was achieved after heat treatment at 400 °C.

Effects of plasma treatment on surface insulation properties of epoxy composites

The surface of epoxy composite material working in DC electric field for a long time is easy to accumulate charge and cause flashover, which seriously reduces its insulation level and poses a threat to the safe operation of electrical equipment. In this study, SiO x films were deposited on the surface of nano-SiO2/ER nanoparticles by atmospheric pressure dielectric barrier discharge plasma vapor deposition technology using ethyl nor-silicate as a precursor. The effects of different deposition time on the deposition effect and the pressure level of the film surface were studied. Scanning electron microscope and atomic force microscope were used to characterize the surface morphology of the material, and the flashover voltage before and after deposition was measured. The results show that SiO x films of different thicknesses can be formed on the surface of the material at different times of plasma deposition. After extending the deposition time of the film, the film becomes more uniform and dense, the surface roughness of the material decreases continuously, and the electrical conductivity and flashover voltage along the surface increases continuously. After 10 min plasma treatment, the conductivity increased from 1.78×10−16 S to 2.3×10−13 S, while the flashover voltage along the surface increased from 19.29 kV to 22.66 kV, an increase of about 17.5%.

Novel PWO/ ZnO heterostructured nanocomposites: Synthesis, characterization, and photocatalytic performance

Photocatalytic degradation is becoming an increasingly attractive method for addressing environmental remediation challenges. In this work, the novel pure PWO/ZnO and doped PWO: Er/ZnO: Ag heterostructure nanocomposites with premier photocatalytic efficiency were synthesized via a simple co-precipitation method followed by a solvothermal procedure. X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX), and ultraviolet–visible (UV–Vis) absorbance measurements techniques were employed to characterize the structural and optical properties. HRTEM images prove the possibility of intimate contact formation at the pure and doped PWO/ZnO heterostructure nanocomposite interfaces. The photocatalytic performance of the PWO/ZnO heterostructure nanocomposites in the degradation of the methylene blue (MB) and methyl orange (MO) dyes under UVA light was evaluated. The photocatalysts’ ability in the mineralization of organic pollutants was confirmed by the TOC test. BET and zeta potential analyses were used to study the dye adsorption mechanisms. Additionally, adsorption isotherms and kinetics have been investigated to describe the adsorption of MB and MO into the samples. The degradation rates of MB with PWO/ZnO and PWO: Er/ZnO: Ag heterostructure nanocomposites were 4.7 and 6.6 times higher than those of PWO and PWO: Er nanoparticles. This rate for MO degradation is 5.2 and 3.5 times higher than that of pure PWO and PWO: Er nanoparticles, respectively. This study outlines an easy method to develop innovative, highly effective heterostructure nanocomposites capable of converting UVA light into photocatalytic performance.

Ultrasmall Day-Night Photocatalysts of LnYVO4:Eu3+ (Ln = Nd, Tm, and Er) Nanoparticles.

Day-night photocatalysts that can persistently generate reactive oxygen species (ROS) after ceasing light attracted intensive attention in diverse fields. However, current strategies of combining a photocatalyst and an energy storage material can hardly fulfill the demands, especially in size. We herein present a one-phase sub-5 nm day-night photocatalyst via simply doping Nd, Tm, or Er into YVO4:Eu3+ nanoparticles, efficiently producing ROS in both day and night modes. We demonstrate that the rare earth ions acted as a ROS generator, and Eu3+ and defects contributed to the long persistency. Furthermore, the ultrasmall size led to remarkable bacterial uptake and bactericidal efficacy. Our finding suggests an alternative mechanism of day-night photocatalysts that could be ultrasmall and thus may shed light on disinfection and other applications.

Polymer-coated hexagonal upconverting nanoparticles: chemical stability and cytotoxicity.

Large (120nm) hexagonal NaYF4:Yb, Er nanoparticles (UCNPs) were synthesized by high-temperature coprecipitation method and coated with poly(ethylene glycol)-alendronate (PEG-Ale), poly (N,N-dimethylacrylamide-co-2-aminoethylacrylamide)-alendronate (PDMA-Ale) or poly(methyl vinyl ether-co-maleic acid) (PMVEMA). The colloidal stability of polymer-coated UCNPs in water, PBS and DMEM medium was investigated by dynamic light scattering; UCNP@PMVEMA particles showed the best stability in PBS. Dissolution of the particles in water, PBS, DMEM and artificial lysosomal fluid (ALF) determined by potentiometric measurements showed that all particles were relatively chemically stable in DMEM. The UCNP@Ale-PEG and UCNP@Ale-PDMA particles were the least soluble in water and ALF, while the UCNP@PMVEMA particles were the most chemically stable in PBS. Green fluorescence of FITC-Ale-modified UCNPs was observed inside the cells, demonstrating successful internalization of particles into cells. The highest uptake was observed for neat UCNPs, followed by UCNP@Ale-PDMA and UCNP@PMVEMA. Viability of C6 cells and rat mesenchymal stem cells (rMSCs) growing in the presence of UCNPs was monitored by Alamar Blue assay. Culturing with UCNPs for 24h did not affect cell viability. Prolonged incubation with particles for 72h reduced cell viability to 40%-85% depending on the type of coating and nanoparticle concentration. The greatest decrease in cell viability was observed in cells cultured with neat UCNPs and UCNP@PMVEMA particles. Thanks to high upconversion luminescence, high cellular uptake and low toxicity, PDMA-coated hexagonal UCNPs may find future applications in cancer therapy.

Multiplet–resonance control and enhancement of upconversion luminescence of NaYF4:Yb,Er nanoparticles in grating–incorporated Metal–DBR cavities

Multiplet–resonance control and enhancement of upconversion luminescence of NaYF4:Yb,Er nanoparticles in grating–incorporated Metal–DBR cavities

Upconversion Luminescence Response of a Single YVO4:Yb, Er Particle.

We present the results of the luminescence response studies of a single YVO4:Yb, Er particle of 1-µm size. Yttrium vanadate nanoparticles are well-known for their low sensitivity to surface quenchers in water solutions which makes them of special interest for biological applications. First, YVO4:Yb, Er nanoparticles (in the size range from 0.05 µm up to 2 µm), using the hydrothermal method, were synthesized. Nanoparticles deposited and dried on a glass surface exhibited bright green upconversion luminescence. By means of an atomic-force microscope, a 60 × 60 µm2 square of a glass surface was cleaned from any noticeable contaminants (more than 10 nm in size) and a single particle of 1-µm size was selected and placed in the middle. Confocal microscopy revealed a significant difference between the collective luminescent response of an ensemble of synthesized nanoparticles (in the form of a dry powder) and that of a single particle. In particular, a pronounced polarization of the upconversion luminescence from a single particle was observed. Luminescence dependences on the laser power are quite different for the single particle and the large ensemble of nanoparticles as well. These facts attest to the notion that upconversion properties of single particles are highly individual. This implies that to use an upconversion particle as a single sensor of the local parameters of a medium, the additional studying and calibration of its individual photophysical properties are essential.

Er-doped gadolinium oxide nanoparticles for enhanced UV-VIS energy conversion: Structural features, optical properties and quantum efficiency

We present comprehensive study of the UV-VIS energy conversion in Gd2O3:Er nanoparticles. Based on our previous research, it was shown that Gd2O3:Er nanoparticles are promising for energy applications due to alternative channel of UV-VIS conversion through the Gd3+def →Er3+ energy transfer. However, a number of important issues, such as the influence of the structural features of the matrix (defectiveness and nonequivalence of cation positions) as well as the concentration of the activator ion on the processes of excitation-relaxation, were poorly understood. In this work we established and explained the mechanisms and regularities of UV-VIS energy conversion in Gd2O3:Er with a wide range of Er3+ concentration (0,25-8%).It was shown that with an increase in the Er3+ ion concentration, the mechanism of Gd3+def →Er3+ energy transfer changes from dipole-quadrupole interaction to exchange interaction due to a decrease in the average donor-acceptor distance. The evolution of the temperature dependences of Er3+ luminescence revealed two structurally (C2 and S6 positions in cubic Gd2O3) and energetically non-equivalent donor Gd3+def ions. It was determined that the distortions in the local environment of Gd3+def ions lead to the transformation of the barrier for emission quenching from discrete to dispersed distribution. The final efficiency of a complex UV-VIS conversion process was obtained accounting a number of factors: role of different channels of Er3+ excitation; bimodal distribution of energy barrier for emission quenching and influence of phonon states on non-radiative losses. The results demonstrate new possibilities for improving the functional characteristics of Gd2O3 nanoparticles for energy conversion devices. As one of the possible practical applications of the results of work, we made and tested prototypes of Si/Gd2O3:Er cells with enhanced efficiency of photovoltaic energy conversion.

Structural, optical, and photocatalytic activity of ZnS:Er nanoparticles

ZnS and Er (2 at%) doped ZnS nanoparticles (NPs) were synthesized through coprecipitation process. EDAX analysis confirmed that the presence of Er (III) ions in the prepared sample with an anticipated stoichiometry. TEM analyses displayed that the prepared NPs showed near spheroid shapes with an average size ranging from 4.8 to 5.2 nm. XRD measurements confirmed the authentic incorporation of Er (III) ions in the ZnS lattice. DRS measurements certified that Er (III) doping declines the ZnS bandgap from 3.72 to 3.56 eV. Magnetic measurements revealed that the Er-doped ZnS NPs displayed soft ferromagnetism and became better at higher doping concentrations. The Er (2 at%) doped ZnS NPs exhibited a higher rhodamine B dye degradation rate than the ZnS. Hence, the Er doped ZnS NPs are promising materials for dye degradation and optoelectronics.

Chemical and Colloidal Stability of Polymer-Coated NaYF4:Yb,Er Nanoparticles in Aqueous Media and Viability of Cells: The Effect of a Protective Coating.

Upconverting nanoparticles (UCNPs) are of particular interest in nanomedicine for in vivo deep-tissue optical cancer bioimaging due to their efficient cellular uptake dependent on polymer coating. In this study, particles, ca. 25 nm in diameter, were prepared by a high-temperature coprecipitation of lanthanide chlorides. To ensure optimal dispersion of UCNPs in aqueous milieu, they were coated with three different polymers containing reactive groups, i.e., poly(ethylene glycol)-alendronate (PEG-Ale), poly(N,N-dimethylacrylamide-co-2-aminoethylacrylamide)-alendronate (PDMA-Ale), and poly(methyl vinyl ether-co-maleic acid) (PMVEMA). All the particles were characterized by TEM, DLS, FTIR, and spectrofluorometer to determine the morphology, hydrodynamic size and ξ-potential, composition, and upconversion luminescence. The degradability/dissolution of UCNPs in water, PBS, DMEM, or artificial lysosomal fluid (ALF) was evaluated using an ion-selective electrochemical method and UV-Vis spectroscopy. The dissolution that was more pronounced in PBS at elevated temperatures was decelerated by polymer coatings. The dissolution in DMEM was relatively small, but much more pronounced in ALF. PMVEMA with multiple anchoring groups provided better protection against particle dissolution in PBS than PEG-Ale and PDMA-Ale polymers containing only one reactive group. However, the cytotoxicity of the particles depended not only on their ability to rapidly degrade, but also on the type of coating. According to MTT, neat UCNPs and UCNP@PMVEMA were toxic for both rat cells (C6) and rat mesenchymal stem cells (rMSCs), which was in contrast to the UCNP@Ale-PDMA particles that were biocompatible. On the other hand, both the cytotoxicity and uptake of the UCNP@Ale-PEG particles by C6 and rMSCs were low, according to MTT assay and ICP-MS, respectively. This was confirmed by a confocal microscopy, where the neat UCNPs were preferentially internalized by both cell types, followed by the UCNP@PMVEMA, UCNP@Ale-PDMA, and UCNP@Ale-PEG particles. This study provides guidance for the selection of a suitable nanoparticle coating with respect to future biomedical applications where specific behaviors (extracellular deposition vs. cell internalization) are expected.

Frail room temperature ferromagnetism and H2 evolution of ZnS:Er nanoparticles through simple chemical co-precipitation route

Frail room temperature ferromagnetism and H2 evolution of ZnS:Er nanoparticles through simple chemical co-precipitation route