Rare Earth Oxide Nanoparticles Research Articles

D-Band Center of Rare Earth Oxides Determines Biotransformation-Induced Cell Membrane Damage.

Biotransformation of rare earth oxide (REO) nanoparticles on biological membranes may trigger a series of adverse health effects in biosystems. However, the physicochemical mechanism of the complicated biotransformation behavior remains elusive. By investigating the distinctly different biotransformation behavior of two typical REOs (Gd2O3 and CeO2) on erythrocyte membranes, we demonstrate that dephosphorylation by stripping phosphate from phospholipids correlates highly with the membrane destructive effects of REOs. Density functional theory calculations decode the decisive role of the d-band center in dephosphorylation. Furthermore, using the d-band center as an electronic descriptor, we unravel a universal structure-activity relationship of the membrane-damaging capability of 13 REOs (R2 = 0.82). The effect of ion release on dephosphorylation and physical damage to cell membranes by Gd2O3 are largely excluded. Our findings depict a clear physicochemical microscopic picture of the biotransformation of REOs on the nano-bio interface, providing a theoretical basis for safe application of REOs.

135 Downregulation of ABCG1 and ABCG4 Transporters by rare Earth Oxide Nanoparticles Induces the Pulmonary Alveolar Proteinosis

Abstract Pulmonary alveolar proteinosis (PAP) is rare disease that accumulates alveolar surfactant. PAP can be induced by nanoparticles (NPs), but there is little information about PAP-producing NPs and their mechanism. Here, we evaluated PAP-producing NPs including 6 of rare earth oxide (REO) NPs and NiO NPs and investigated the magnitude and related gene expression (ATP-binding cassette, ATP) of PAP at 1 and 6 months after single intratracheal instillation to Wistar rats. Furthermore, we evaluated morphological change of REO NPs because biotransformation is critical to understand the toxicity. The 6 REO NPs (Dy2O3, Eu2O3, In2O3, Pr6O11, Sm2O3, and Tb4O7) and NiO NPs caused PAP at 1 month, while only In2O3 NPs showed a persistent PAP at 6 months. All the REO NPs transformed sea urchin-shaped within the alveolar macrophage up to 6 months. The levels of phospholipids, indicators of PAP, showed good correlation with gene expression of five ABC transporters (ABCA1, ABCB4, ABCB8, ABCG1, and ABCG4), which effluxing phospholipids in PAP. Among them, ABCG1 and ABCG4 might be key transporters involved in PAP development because both showed negative correlation with the magnitude of PAP, while others might be compensatory transporters for PAP recovery, as they showed a positive correlation. In conclusion, the identification of seven PAP-producing NPs implies that PAP may be an emerging occupational disease and that ABCG1 and ABCG4 may be therapeutic targets for PAP. In this regard, we are studying therapeutic agent for PAP induced by NPs using medicine related PPAR-gamma, which is upstream mechanism of ABCG1 and ABCG4.

Emerging Nanoparticles in Food: Sources, Application, and Safety.

Nanoparticles (NPs) are small-sized, with high surface activity and antibacterial and antioxidant properties. As a result, some NPs are used as functional ingredients in food additives, food packaging materials, nutrient delivery, nanopesticides, animal feeds, and fertilizers to improve the bioavailability, quality, and performance complement or upgrade. However, the widespread use of NPs in the industry increases the exposure risk of NPs to humans due to their migration from the environment to food. Nevertheless, some NPs, such as carbon dots, NPs found in various thermally processed foods, are also naturally produced from the food during food processing. Given their excellent ability to penetrate biopermeable barriers, the potential safety hazards of NPs on human health have attracted increased attention. Herein, three emerging NPs are introduced including carbon-based NPs (e.g., CNTs), nanoselenium NPs (SeNPs), and rare earth oxide NPs (e.g., CeO2 NPs). In addition, their applications in the food industry, absorption pathways into the human body, and potential risk mechanisms are discussed. Challenges and prospects for the use of NPs in food are also proposed.

Synthesis of Core-Shell CeO2/CeF3 Nanoparticles Using Tetrafluoroethane R-134a

In this paper, we report the synthesis, characterization, and optical properties of core-shell CeO2/CeF3 nanoparticles. Fabrication of these composite nanoparticles was carried out by fluorination of CeO2 nanoparticles with tetrafluoroethane R-134a gas at high temperatures (800–1200 °C) in a special vacuum furnace with a tubular graphite heater. The obtained X-ray diffraction spectra (XRD) and luminescence measurements confirm the formation of composite CeO2/CeF3 nanoparticles. Simulation of XRD spectra and calculation of lattice parameters were carried out. A proposed method of synthesis can be used for other rare-earth oxide nanoparticles to fabricate core-shell oxyfluoride nanosized composites that combine the properties of oxide and fluoride nanoparticles.

Phytotoxicity and the molecular response in yttrium oxide nanoparticle-treated Arabidopsis thaliana seedlings.

Due to the widespread application of rare earth oxide nanoparticles in various fields, their release into the environment is inevitable, and their potential toxicity and ecological impact have become a concern. Yttrium oxide nanoparticles are important rare earth oxide nanoparticles; however, their impact on plants and the molecular mechanism underlying their influence on plant growth and development are unclear. In this study, we found that yttrium oxide nanoparticles at concentrations exceeding 2mM significantly inhibited the growth of Arabidopsis seedlings. Using Arabidopsis marker lines for auxin signaling, we found that the application of yttrium oxide nanoparticles resulted in disordered auxin signaling in root cells. Auxin signaling in the cells of the quiescent center and columella stem cells decreased, while auxin signaling in the cells of the stele was enhanced. In addition, trypan blue staining showed that yttrium oxide nanoparticles induced root cell death. Transcriptome analysis showed that the nanoparticles specifically inhibited the expression of lignin synthesis-related genes, activated the MAPK signaling pathway, and enhanced the ethylene and abscisic acid signaling pathways in plants. This study demonstrates the phytotoxicity of yttrium oxide nanoparticles at the molecular level in Arabidopsis, and it provides a new perspective on how plants respond to rare earth oxide stress.

Sintering of high-entropy nanoparticles obtained by polyol process: A case study of (La0.2Y0.2Nd0.2Sm0.2Gd0.2)2Ce2O7-δ

High-entropy (HE) ceramics nanoparticles have received much attention due to their interesting properties. However, very limited studies have been conducted on their sintering. Here, we report the sintering behavior of HE A2B2O7 type rare earth oxide nanoparticles obtained by polyol process. HE cerate (HECe) (La0.2Y0.2Nd0.2Sm0.2Gd0.2)2Ce2O7-δ is chosen as an exemplary case, which is considered as a good candidate for thermal insulation. HECe nanoparticles with size of 2.6–7.1 nm can be synthesized through polyol process followed by annealing in air at 300–700 °C. HECe nanoparticle compact can be densified by directly sintering at 1500 °C. The sintering temperature could be further decreased using a two-step sintering process, i.e., 1500 °C 5 min-1300 °C 5 h. Our results show that fine particle and abundant oxygen vacancies probably dominate the densification process. By controlling the sintering regime, we can tune the microstructure of HECe ceramics and thermal conductive properties accordingly.

Temperature assisted size dependent synthesis and magnetic properties of rare-earth chromium oxide nanoparticles

We report the synthesis of homogeneous single-phase nanoparticles of RCrO4 and RCrO3 (R = Sm, Gd, Dy, and Er) compounds using a modified sol–gel hydrothermal method followed by heat treatment. Annealing of the as-prepared powder sample at ambient pressure enables chromium to remain in the metastable Cr5+ (4s03d1) state by crystallizing into a zircon-type tetragonal RCrO4 (S.G. I41/amd, D4h19 symmetry) structure at 773 K, while it chooses to form orthorhombic RCrO3 (S.G. Pbnm, D4h19 symmetry) structure with a stable Cr3+ (4s03d3) state at 973 K. The analysis of DC magnetization (M) versus temperature (T) in an external magnetic field, H = 100 Oe for polycrystalline RCrO4 indicates the magnetic transition temperatures, TC ∼ 20 K. The derivative of zero-field cooled magnetic susceptibility with respect to T, dχZFCdT, versus T, indicates the presence of competing magnetic interactions due to the ferromagnetic (FM) and antiferromagnetic (AFM) ordering of Cr5+ and R3+ in RCrO4 respectively near magnetic transition. This feature specifies magnetic frustration that leads to metamagnetism in RCrO4. The fit of non-linear magnetic susceptibility, χ=MH, to χ=χ0+CT-θ, with a non-zero χ0 determined from high-T data gives effective magnetic moment, μeff, which is in accordance with the theoretical value. The analysis of M vs. T indicates that RCrO3 undergoes a paramagnetic (PM) to canted-antiferromagnetic (CAFM) transition of Cr sublattices at Néel temperature (TNCr) because of antisymmetric Dzyaloshinskii-Moriya (DM) interaction due to Cr–O–Cr superexchange with a possible antiferromagnetic (AFM) ordering of the rare-earth at low temperature (TNR < 20 K). The linear fit of χ-1 vs. T with a zero χ0 shows Curie-Weiss law is more appropriate at T>TC resulting expected μeff values for RCrO3.

Structural and optical investigations in undoped and rare-earth doped zinc oxide nanoparticles for photon upconversion based applications

The present work reports comprehensive investigations of the physical properties of undoped and rare-earth (RE3+) doped ZnO based upconversion nanoparticles. X-ray diffraction analysis of these nanoparticles reveals the hexagonal wurtzite structure. The induced-strain value of the RE3+ doped ZnO nanoparticles increased by almost one order of magnitude, and their mean particle size reduced from 36 nm to 17 nm. The scanning electron microscopic images showed that the particles retained the spherical shape in the undoped and doped conditions. The elemental maps confirmed the uniform distribution of the RE3+ dopants. The recorded absorbance spectrum for the doped nanoparticles showed significant absorption in ultraviolet and near infra-red regions owing to the band-band transitions and the deep defect level transitions that are induced due to intrinsic and extrinsic defect states. A detailed analysis of the defect states of these samples is described based on the Urbach energy studies. An intense peak observed at 980 nm suggests the possibility of photon upconversion in the doped nanoparticles. A simplified energy diagram (as depicted below) has demonstrated the multi-photon absorption and possible upconversion mechanisms. The optical absorption spectrum of RE3+ doped ZnO nanocrystals encourages the promising application of these materials in diverse fields, particularly in biomedical and photovoltaic applications.

Boosting overall electrochemical water splitting via rare earth doped cupric oxide nanoparticles obtained by co-precipitation technique

The development of electrocatalyst based on nonprecious metals has been a persistent issue as electrochemical water splitting requires electrocatalyst with advanced activity and stability. Further, the electrocatalyst must require low overpotential above the standard potential (>1.23 V) of water splitting to produce hydrogen. This study presents the facile co-precipitation derived rare earth dysprosium (Dy) doped cupric oxide nanoparticles (Cu1−xDyxO) as a non-noble transition metal oxide nanoparticle. The 3 % Dy doped CuO (3 % Dy/CuO) and 1 % Dy doped CuO (1 % Dy/CuO) electrocatalysts showed excellent Oxygen Evolution Reaction (OER) at 1.55 V vs RHE and Hydrogen Evolution Reaction (HER) at − 0.036 V vs RHE in aqueous 1 M KOH aqueous electrolyte to attain the benchmark current density (10 mA cm−2). The stability of the driven electrocatalyst in a bi-functional electrocatalytic setup was monitored for 24 h and was found to be exhibiting a cell voltage of about 2.1 V at 30 mA cm−2 constant current density. Further, the retention capability of the electrode was observed to be 99 % with a very minimal loss. This study hugely suggests the promising consequence of doping rare earth onto a non-precious metal oxide-based electrocatalyst, making it a highly effective bifunctional material for water splitting.

CeO2-Zn Nanocomposite Induced Superoxide, Autophagy and a Non-Apoptotic Mode of Cell Death in Human Umbilical-Vein-Derived Endothelial (HUVE) Cells.

In this study, a nanocomposite of cerium oxide-zinc (CeO2-Zn; 26 ± 11 nm) based on the antioxidant rare-earth cerium oxide (CeO2) nanoparticles (NPs) with the modifier zinc (Zn) was synthesized by sintering method and characterized. Its bio-response was examined in human umbilical-vein-derived endothelial (HUVE) cells to get insight into the components of vascular system. While NPs of CeO2 did not significantly alter cell viability up to a concentration of 200 µg/mL for a 24 h exposure, 154 ± 6 µg/mL of nanocomposite CeO2-Zn induced 50% cytotoxicity. Mechanism of cytotoxicity occurring due to nanocomposite by its Zn content was compared by choosing NPs of ZnO, possibly the closest nanoparticulate form of Zn. ZnO NPs lead to the induction of higher reactive oxygen species (ROS) (DCF-fluorescence), steeper depletion in antioxidant glutathione (GSH) and a greater loss of mitochondrial membrane potential (MMP) as compared to that induced by CeO2-Zn nanocomposite. Nanocomposite of CeO2-Zn, on the other hand, lead to significant higher induction of superoxide radical (O2•−, DHE fluorescence), nitric oxide (NO, determined by DAR-2 imaging and Griess reagent) and autophagic vesicles (determined by Lysotracker and monodansylcadeverine probes) as compared to that caused by ZnO NP treatment. Moreover, analysis after triple staining (by annexin V-FITC, PI, and Hoechst) conducted at their respective IC50s revealed an apoptosis mode of cell death due to ZnO NPs, whereas CeO2-Zn nanocomposite induced a mechanism of cell death that was significantly different from apoptosis. Our findings on advanced biomarkers such as autophagy and mode of cell death suggested the CeO2-Zn nanocomposite might behave as independent nanostructure from its constituent ones. Since nanocomposites can behave independently of their constituent NPs/elements, by creating nanocomposites, NP versatility can be increased manifold by just manipulating existing NPs. Moreover, data in this study can furnish early mechanistic insight about the potential damage that could occur in the integrity of vascular systems.

Constructing Multiple Heterostructures on Nickel Oxide Using Rare‐earth Oxide and Nickel as Efficient Bifunctional Electrocatalysts for Overall Water Splitting

AbstractConstructing heterostructured electrocatalyst is a promising strategy to explore inexpensive and effective catalysts towards oxygen evolution reaction (OER), hydrogen evolution reaction (HER) and the overall water splitting (OWS). Here, amorphous NiO 2D layers decorated with Ni and rare earth oxide (REOx) nanoparticles, which possess multiple heterostructures (Ni−NiO and REOx‐NiO), have been synthesized by the sequential electrodeposition on carbon cloth. The electrocatalytic performances for the prepared Er2O3/Ni−NiO and CeO2/Ni−NiO have been evaluated, exhibiting improved HER (39 mV@10 mA cm−2) and OER (318 mV@50 mA cm−2) activities in contrast to the single component, respectively. Additionally, the two‐electrode system (Er2O3/Ni−NiO//CeO2/Ni−NiO) presents an excellent OWS property which displays a low potential of 1.58 V to reach 10 mA cm−2. This work helps to deepen the understanding of the synergetic interaction between dissimilar materials in heterostructured catalyst, and provides guidance for the further exploration and evolution of nanomaterials in green energy conversion technology.

Rare-earth metal oxide nanoparticles decouple the linkage between soil bacterial community structure and function by selectively influencing potential keystone taxa

Excessive production and application of rare-earth metal oxide nanoparticles warrants assessment of their environmental risks. Little is known about the impact of these nanoparticles on soil bacterial communities. We quantified the effects of nano-Gd2O3 and nano-La2O3, at the different concentrations and exposure regimes, on soil bacterial community structure and function as well as the structure-function relationship. Further, we constructed and analyzed a co-occurrence network to identify and characterize potential keystone taxa that were related to the enzyme activities and responded to the increasing concentrations of nanoparticles. Both nano-Gd2O3 and nano-La2O3 significantly altered the bacterial community structure and function in a concentration-dependent manner; however, these negative effects were observed on day 1 or day 7 but not on day 60, indicating that these effects were transient and the bacterial communities can mitigate the effect of these nanoparticles over time. Interestingly, the nanoparticle exposure decoupled the relationship between the structure and function of the soil bacterial communities. The decoupling was due to changes in the composition and relative abundances of potential keystone taxa related to bacterial community functions. Altogether, we provide insights into the interactions between the rare-earth metal oxide nanoparticles and soil bacterial communities. Our results facilitate the environmental risk assessment and safe usage of rare-earth metal oxide nanoparticles.

Nano-La2O3 Induces Honeybee (Apis mellifera) Death and Enriches for Pathogens in Honeybee Gut Bacterial Communities.

Honeybees (Apis mellifera) can be exposed via numerous potential pathways to ambient nanoparticles (NPs), including rare earth oxide (REO) NPs that are increasingly used and released into the environment. Gut microorganisms are pivotal in mediating honeybee health, but how REO NPs may affect honeybee health and gut microbiota remains poorly understood. To address this knowledge gap, honeybees were fed pollen and sucrose syrup containing 0, 1, 10, 100, and 1000mgkg−1 of nano-La2O3 for 12days. Nano-La2O3 exerted detrimental effects on honeybee physiology, as reflected by dose-dependent adverse effects of nano-La2O3 on survival, pollen consumption, and body weight (p<0.05). Nano-La2O3 caused the dysbiosis of honeybee gut bacterial communities, as evidenced by the change of gut bacterial community composition, the enrichment of pathogenic Serratia and Frischella, and the alteration of digestion-related taxa Bombella (p<0.05). There were significant correlations between honeybee physiological parameters and the relative abundances of pathogenic Serratia and Frischella (p<0.05), underscoring linkages between honeybee health and gut bacterial communities. Taken together, this study demonstrates that nano-La2O3 can cause detrimental effects on honeybee health, potentially by disordering gut bacterial communities. This study thus reveals a previously overlooked effect of nano-La2O3 on the ecologically and economically important honeybee species Apis mellifera.

A Glance on Rare Earth Oxides: Importance, Reserves, De mand, Applications, Critical Uncertainties, Global Economy, and Zeta Potential Characterization

Background: Innovation mission in materials science requires new approaches to form functional materials, wherein the concept of its formation begins in nano/micro scale. Rare earth oxides with general form (RE2O3; RE from La to Lu, including Sc and Y) exhibit particular proprieties, being used in a vast field of applications with high technological content since agriculture to astronomy. Despite of their applicability, there is a lack of studies on surface chemistry of rare earth oxides. Zeta potential determination provides key parameters to form smart materials by controlling interparticle forces, as well as their evolution during processing. This paper reports a study on zeta potential with emphasis for rare earth oxide nanoparticles. A brief overview on rare earths, as well as zeta potential, including sample preparation, measurement parameters, and the most common mistakes during this evaluation are reported. Methods: A brief overview on rare earths, including zeta potential, and interparticle forces are presented. A practical study on zeta potential of rare earth oxides - RE2O3 (RE as Y, Dy, Tm, Eu, and Ce) in aqueous media is reported. Moreover, sample preparation, measurement parameters, and common mistakes during this evaluation are discussed. Results: Potential zeta values depend on particle characteristics such as size, shape, density, and surface area. Besides, preparation of samples which involves electrolyte concentration and time for homogenization of suspensions are extremely valuable to get suitable results. Conclusion: Zeta potential evaluation provides key parameters to produce smart materials seeing that interparticle forces can be controlled. Even though zeta potential characterization is mature, investigations on rare earth oxides are very scarce. Therefore, this innovative paper is a valuable contribution on this field.

Introduction of Rare-Earth Oxide Nanoparticles in CNT-Based Nanocomposites for Improved Detection of Underlying CNT Network.

Epoxy resins for adhesive and structural applications are widely employed by various industries. The introduction of high aspect ratio nanometric conductive fillers, i.e., carbon nanotubes, are well studied and are known to improve the electrical properties of the bulk material by orders of magnitude. This improved electrical conductivity has made carbon nanotube-based nanocomposites an attractive material for applications where their weight savings are at a premium. However, the analytical methods for validating carbon nanotube (CNT) nanofiller dispersion and for assuring that the properties they induce extend to the entire volume are destructive and inhibited by poor resolution between matrix and tube bundles. Herein, rare-earth oxide nanoparticles are synthesized on CNT walls for the purpose of increasing the contrast between their network and the surrounding matrix when studied by imaging techniques, alleviating these issues. The adherence of the synthesized nanoparticles to the CNT walls is documented via transmission electron microscopy. The crystalline phases generated during the various fabrication steps are determined using X-ray diffraction. Deep ultraviolet-induced fluorescence of the Eu:Y2O3-CNT nanostructures is verified. The impacts to nanocomposite electrical properties resulting from dopant introduction are characterized. The scanning electron microscopy imaging of CNT pulp and nanocomposites fabricated from untreated CNTs and Eu:Y2O3-CNTs are compared, resulting in improved contrast and detection of CNT bundles. The micro-CT scans of composites with similar results are presented for discussion.

Tuning of thermoelectric transport properties via the formation of hierarchical structures in Bi‐doped Gd 2 O 3 /Bi 0. 5 Sb 1 . 5 Te 3 nanocomposites

In this study, we developed hierarchical nanostructures by incorporating bismuth-doped and undoped rare earth oxide (Gd1.98Bi0.02O3 and Gd2O3) nanoparticles (NPs) into Bi0.5Sb1.5Te3 (BST) matrix. The influence of Gd2O3 and Gd1.98Bi0.02O3 nano-inclusions on microstructure and thermoelectric properties of BST composites have been investigated. The results reveal that the addition of 2 wt% Gd1.98Bi0.02O3 (bismuth-doped RE-oxide) into the matrix forms hierarchical structures that cause an enhanced electrical conductivity attributed to increasing carrier concentration as the substitution of bismuth preserves the comprehensive structure type and charge carrier concentration. Simultaneously, the Seebeck coefficient increases for the composite samples compared with a bare sample, due to an increase of effective mass by carrier energy filtering, while the total thermal conductivity decreased significantly by an enhanced phonon scattering at the nanoparticles, which is about 9% lower than that of BST matrix. Consequently, the ZT reached 0.87 at 300 K for BST/Gd1.98Bi0.02O3 composite, which is 30% higher than BST matrix. The result indicates that the Bi-doped rare earth oxide (Gd1.98Bi0.02O3) incorporation into BST could improve the thermoelectric properties of the BST-based materials. Furthermore, this work presumes that the doping effect of bismuth into the gadolinium oxide can reduce the initial defects in the structure of the synthesized Gd2O3.

A Review on Development of Rare Earth Based Contrast Agents for Dual Modal Imaging of Cancer Cells

The risk of developing cancer is becoming higher due to the genetic and environmental factors. Diagnosing cancer at an early stage is a very big challenge to clinicians and researchers. Several imaging modalities are being used in hospitals for diagnostic purposes. But each imaging modality has some limitations to identify the cancer cells at their early stage. Magnetic resonance imaging can be combined with optical imaging for better diagnosis of cancer. This concept of combining two imaging modalities is termed as ‘dual modal imaging’. In dual modal imaging, the limitation of one technique becomes the advantage of other. This review article focuses on the dual modal imaging which is achieved by using rare earth doped gadolinium oxide nanoparticles. By doping the rare earth ions into the gadolinium oxide matrix, both the optical and magnetic properties of the material are shared.

Biotransformation of rare earth oxide nanoparticles eliciting microbiota imbalance

BackgroundDisruption of microbiota balance may result in severe diseases in animals and phytotoxicity in plants. While substantial concerns have been raised on engineered nanomaterial (ENM) induced hazard effects (e.g., lung inflammation), exploration of the impacts of ENMs on microbiota balance holds great implications.ResultsThis study found that rare earth oxide nanoparticles (REOs) among 19 ENMs showed severe toxicity in Gram-negative (G−) bacteria, but negligible effects in Gram-positive (G+) bacteria. This distinct cytotoxicity was disclosed to associate with the different molecular initiating events of REOs in G− and G+ strains. La2O3 as a representative REOs was demonstrated to transform into LaPO4 on G− cell membranes and induce 8.3% dephosphorylation of phospholipids. Molecular dynamics simulations revealed the dephosphorylation induced more than 2-fold increments of phospholipid diffusion constant and an unordered configuration in membranes, eliciting the increments of membrane fluidity and permeability. Notably, the ratios of G−/G+ reduced from 1.56 to 1.10 in bronchoalveolar lavage fluid from the mice with La2O3 exposure. Finally, we demonstrated that both IL-6 and neutrophil cells showed strong correlations with G−/G+ ratios, evidenced by their correlation coefficients with 0.83 and 0.92, respectively.ConclusionsThis study deciphered the distinct toxic mechanisms of La2O3 as a representative REO in G− and G+ bacteria and disclosed that La2O3-induced membrane damages of G− cells cumulated into pulmonary microbiota imbalance exhibiting synergistic pulmonary toxicity. Overall, these findings offered new insights to understand the hazard effects induced by REOs.

Optical nanomaterials with focus on rare earth doped oxide: A Review

Optical nanomaterials (ONMs) have attracted significant attention of the global research community owing to their several superior advantages. Some of the ONMs depict negligible photobleaching, bright emission, large electron-hole overlap integral, ease of coating on any surface, large Stoke/Antistoke shifts, higher photostabilites, easy to incorporate inside human body etc. These properties make them technologically highly efficient which helps in minimizing the global issue of energy crisis and improving the standard of living of common man. Several aspects of ONMs such as plasmonic nanomaterials, quantum dots, photonic crystals, and rare earth doped nanoparticles have been discussed. For covering various categories of luminescent nanomaterials (LNMs) based on composition, a brief introduction and importance of metal nanoclusters, carbon nano dots, organic-inorganic nanocomposites, and metal doped nanoparticles have been also included. This review article gives very concise overview of rare earth doped oxide nanoparticles covering several important aspects such as rare earth ion (RE) as dopant, oxide-based host, nanophosphors etc. The importance of LNMs, their advantages as well as drawbacks are also highlighted. Technologically important types of RE doped oxide nanoparticles pertaining to downconversion, upconversion, persistence and radioluminescence are also explained and covered in detail in this review article. Several recent applications involving LNMs in bioimaging, solar cell, thermal sensor, biosensor, anti-counterfeiting etc are explained. In the last section of the review, a comparison between nano and bulk rare earth doped oxide LNMs are discussed in terms of several photophysical properties such as dopant local symmetry, Stark splitting, emission intensity, luminescence lifetime, host to dopant energy transfer, quantum yield etc. Finally, this review article is concluded with summary, outlook, challenges, and future scope on the use of LNMs. Several important aspects of LNMs with focus on RE doped oxide nanoparticles have been covered in this review article which will help general readers in their further research, in this important area, for development of both fundamental sciences and applications involving LNMs.

Effect of samarium oxide nanoparticles on degradation and invitro biocompatibility of magnesium

Benefitting from the advantages of being bioresorbable and having an elastic modulus, density and mechanical properties that closely match load-bearing bones, magnesium (Mg)-based materials are emerging as superior alternatives to permanent implants like titanium and stainless steel in orthopedic and craniofacial trauma fixation. To inhibit faster degradation of magnesium in physiological environments that has greatly limited its widespread clinical applicability, thermally stable metal-oxide nanoparticles have been used as a reinforcement to simultaneously improve the biomechanical and corrosion properties. Against this background, the objective of this study was to develop non-toxic magnesium-based nanocomposites incorporating rare earth oxides (REOs) synthesized by powder metallurgy technique followed by microwave sintering. The influence of rare-earth oxide (Sm2O3) nanoparticles on the microstructure, degradation, and biological performance of magnesium was investigated. The immersion test for 28 days revealed the rate of corrosion in Mg/1.5 vol.% Sm2O3 was 1.028 mm/year, reflecting a 25 % improvement compared to Mg. The viabilities of MC3T3-E1 cells for up to 1 vol.% Sm2O3 addition was >70 % indicating good in-vitro cytocompatibility while the lactate dehydrogenase (LDH) assay revealed all the nanocomposites exhibited Level ‘0’ cytotoxicity. The potential of rare-earth oxide reinforced magnesium nanocomposites, as explored in this work, was found to be suitable for temporary implant instead of rare-earth alloying addition to magnesium, which has known to cause potential toxicity.