Tailoring iridium-palladium nanoparticles with Ir-rich skin: a highly durable anode electrocatalyst for acidic water electrolysis via a facile microwave-assisted chemical reduction method.

Electrochemical water splitting under acidic conditions is a clean way towards producing hydrogen fuels. The slow kinetics of the oxygen evolution reaction (OER) at the anode is currently a bottleneck for commercial acceptance of this technology. Therefore, arriving at more efficient and sustainable OER electrocatalysts is highly desirable. We here demonstrate the synthesis of iridium-palladium (IrPd) alloy nanoparticles (2-5 nm) with variable average composition (Ir : Pd = 1 : 0, 1 : 1, 1 : 3, 1 : 6, 1 : 9 and 0 : 1) using a facile one-pot microwave-assisted chemical reduction method. The IrPd nanoparticles show structure- and composition-dependent OER performance in acidic media. Utilizing different reduction strengths and precursor ratios, successful alloy catalysts were prepared with Ir-rich skin and sublayers of different Pd compositions. Their structures were revealed using high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and hydrogen underpotential deposition (Hupd) studies. It turned out that (1) the alloy OER catalyst also has a high electrochemically active surface area for hydrogen adsorption/desorption, (2) the OER performance is strongly dependent on the surface Ir contribution and (3) the intact Ir skin is essential for electrocatalyst stability.

The efficient magneto-mechanical actuation of cancer cells using a very low concentration of non-interacting ferrimagnetic hexaferrite nanoplatelets.

Magneto-mechanical actuation (MMA) using the low-frequency alternating magnetic fields (AMFs) of magnetic nanoparticles internalized into cancer cells can be used to irreparably damage these cells. However, nanoparticles in cells usually agglomerate, thus greatly augmenting the delivered force compared to single nanoparticles. Here, we demonstrate that MMA also decreases the cell viability, with the MMA mediated by individual, non-interacting nanoparticles. The effect was demonstrated with ferrimagnetic (i.e., permanently magnetic) barium-hexaferrite nanoplatelets (NPLs, ∼50 nm wide and 3 nm thick) with a unique, perpendicular orientation of the magnetization. Two cancer-cell lines (MDA-MB-231 and HeLa) are exposed to the NPLs in-vitro under different cell-culture conditions and actuated with a uniaxial AMF. TEM analyses show that only a small number of NPLs internalize in the cells, always situated in membrane-enclosed compartments of the endosomal-lysosomal system. Most compartments contain 1-2 NPLs and only seldom are the NPLs found in small groups, but never in close contact or mutually oriented. Even at low concentrations, the single NPLs reduce the cell viability when actuated with AMFs, which is further increased when the cells are in starvation conditions. These results pave the way for more efficient in-vivo MMA at very low particle concentrations.

Inflammatory, Oxidative Stress and Small Cellular Particle Response in HUVEC Induced by Debris from Endoprosthesis Processing.

We studied inflammatory and oxidative stress-related parameters and cytotoxic response of human umbilical vein endothelial cells (HUVEC) to a 24 h treatment with milled particles simulating debris involved in sandblasting of orthopedic implants (OI). We used different abrasives (corundum-(Al2O3), used corundum retrieved from removed OI (u. Al2O3), and zirconia/silica composite (ZrO2/SiO2)). Morphological changes were observed by scanning electron microscopy (SEM). Concentration of Interleukins IL-6 and IL-1ß and Tumor Necrosis Factor α (TNF)-α was assessed by enzyme-linked immunosorbent assay (ELISA). Activity of Cholinesterase (ChE) and Glutathione S-transferase (GST) was measured by spectrophotometry. Reactive oxygen species (ROS), lipid droplets (LD) and apoptosis were measured by flow cytometry (FCM). Detachment of the cells from glass and budding of the cell membrane did not differ in the treated and untreated control cells. Increased concentration of IL-1ß and of IL-6 was found after treatment with all tested particle types, indicating inflammatory response of the treated cells. Increased ChE activity was found after treatment with u. Al2O3 and ZrO2/SiO2. Increased GST activity was found after treatment with ZrO2/SiO2. Increased LD quantity but not ROS quantity was found after treatment with u. Al2O3. No cytotoxicity was detected after treatment with u. Al2O3. The tested materials in concentrations added to in vitro cell lines were found non-toxic but bioactive and therefore prone to induce a response of the human body to OI.

Saturation magnetisation as an indicator of the disintegration of barium hexaferrite nanoplatelets during the surface functionalisation.

Barium hexaferrite nanoplatelets (BHF NPLs) are permanent nanomagnets with the magnetic easy axis aligned perpendicular to their basal plane. By combining this specific property with optimised surface chemistry, novel functional materials were developed, e.g., ferromagnetic ferrofluids and porous nanomagnets. We compared the interaction of chemically different phosphonic acids, hydrophobic and hydrophilic with 1-4 phosphonic groups, with BHF NPLs. A decrease in the saturation magnetisation after functionalising the BHF NPLs was correlated with the mass fraction of the nonmagnetic coating, whereas the saturation magnetisation of the NPLs coated with a tetraphosphonic acid at 80 °C was significantly lower than expected. We showed that such a substantial decrease in the saturation magnetisation originates from the disintegration of BHF NPLs, which was observed with atomic-resolution scanning transmission electron microscopy and confirmed by a computational study based on state-of-the-art first-principles calculations. Fe K-edge XANES (X-ray absorption near-edge structure) and EXAFS (Extended X-ray absorption fine structure) combined with Fourier-transformed infrared (FTIR) spectroscopy confirmed the formation of an Fe-phosphonate complex on the partly decomposed NPLs. Comparing our results with other functionalised magnetic nanoparticles confirmed that saturation magnetisation can be exploited to identify the disintegration of magnetic nanoparticles when insoluble disintegration products are formed.

Adaptation of the Crystal Structure to the Confined Size of Mixed-oxide Nanoparticles.

Chemical composition and crystal structure are central to defining the functional properties of materials. But when a material is prepared in the form of nanoparticles, the structure and, as a consequence, the composition will also frequently change. Understanding these changes in the crystal structure at the nanoscale is therefore essential not only for expanding fundamental knowledge, but also for designing novel nanostructures for diverse technological and medical applications. The changes can originate from two thermodynamically driven phenomena: (i) a crystal structure will adapt to the restricted size of the nanoparticles, and (ii) metastable structural polymorphs that form during the synthesis due to a lower nucleation barrier (compared to the equilibrium phase) can be stabilized at the nanoscale. The changes to the crystal structure at the nanoscale are especially pronounced for inorganic materials with a complex structure and composition, such as mixed oxides with a structure built from alternating layers of several structural blocks. In this article the complex structure of nanoparticles will be presented based on two examples of well-known and technologically important materials with layered structures: magnetic hexaferrites (BaFe12O19 and SrFe12O19) and ferroelectric Aurivillius layered-perovskite bismuth titanate (Bi4Ti3O12).

Ferroelectric bismuth-titanate nanoplatelets and nanowires with a new crystal structure.

Two different morphologies of ferroelectric bismuth titanate (Bi4Ti3O12) nanoparticles, i.e., nanoplatelets and nanowires, were synthesized by changing the concentration of NaOH during a hydrothermal treatment of precipitated Ti4+ and Bi3+ ions. The nanoparticles' crystal structures were characterized using atomic-resolution imaging with a CS-probe-corrected scanning-transmission electron microscope in combination with X-ray diffractometry and Raman spectroscopy. The nanoplatelets (10 nm thick and from 50 nm to 200 nm wide) exhibit the Aurivillius-type layered-perovskite crystal structure that is characteristic of Bi4Ti3O12, whereas the nanowires (from 15 nm to 35 nm wide and from several hundreds of nm to several µm long) exhibit an entirely new structure with an orthorhombic unit cell (a = 3.804(1) Å, b = 11.816(3) Å, and c = 9.704(1) Å). The nanowire structure is composed of two structural layers alternating along the orthorhombic c-direction: a structural layer composed of two parallel layers of Bi atoms that resembles the (Bi2O2)2+ layer of the Aurivillius structure, and a structural layer composed of two parallel layers of Ti atoms, where every sixth Ti is replaced with Bi. Observations of the ferroelectric domains with transmission electron and piezo-response force microscopy indicated the ferroelectric nature of both nanostructures. The nanowire structure is a metastable polymorph of the bismuth titanate stabilized at the nanoscale. With annealing at temperatures above 500 °C the nanowire structure topotactically transforms into the Aurivillius structure.

Synthesis of a precursor of D-fagomine by immobilized fructose-6-phosphate aldolase.

Fructose-6-phosphate aldolase (FSA) is an important enzyme for the C-C bond-forming reactions in organic synthesis. The present work is focused on the synthesis of a precursor of D-fagomine catalyzed by a mutant FSA. The biocatalyst has been immobilized onto several supports: magnetic nanoparticle clusters (mNC), cobalt-chelated agarose (Co-IDA), amino-functionalized agarose (MANA-agarose) and glyoxal-agarose, obtaining a 29.0%, 93.8%, 89.7% and 53.9% of retained activity, respectively. Glyoxal-agarose FSA derivative stood up as the best option for the synthesis of the precursor of D-fagomine due to the high reaction rate, conversion, yield and operational stability achieved. FSA immobilized in glyoxal-agarose could be reused up to 6 reaction cycles reaching a 4-fold improvement in biocatalyst yield compared to the non-immobilized enzyme.

Standardization of esophageal adenocarcinoma in vitro model and its applicability for model drug testing.

FLO-1 cell line represents an important tool in esophageal adenocarcinoma (EAC) research as a verified and authentic cell line to study the disease pathophysiology and antitumor drug screenings. Since in vitro characteristics of cells depend on the microenvironment and culturing conditions, we performed a thorough characterization of the FLO-1 cell line under different culturing conditions with the aim of (1) examining the effect of serum-free growth medium and air-liquid interface (A-L) culturing, which better reflect physiological conditions in vivo and (2) investigating the differentiation potential of FLO-1 cells to mimic the properties of the in vivo esophageal epithelium. Our study shows that the composition of the media influenced the morphological, ultrastructural and molecular characteristics of FLO-1 cells, such as the expression of junctional proteins. Importantly, FLO-1 cells formed spheres at the A-L interface, recapitulating key elements of tumors in the esophageal tube, i.e., direct contact with the gas phase and three-dimensional architecture. On the other hand, FLO-1 models exhibited high permeability to model drugs and zero permeability markers, and low transepithelial resistance, and therefore poorly mimicked normal esophageal epithelium. In conclusion, the identified effect of culture conditions on the characteristics of FLO-1 cells should be considered for standardization, data reproducibility and validity of the in vitro EAC model. Moreover, the sphere-forming ability of FLO-1 cells at the A-L interface should be considered in EAC tumor biology and anticancer drug studies as a reliable and straightforward model with the potential to increase the predictive efficiency of the current in vitro approaches.

Magneto-mechanical actuation of barium-hexaferrite nanoplatelets for the disruption of phospholipid membranes.

HYPOTHESIS: The magneto-mechanical actuation (MMA) of magnetic nanoparticles with a low-frequency alternating magnetic field (AMF) can be used to destroy cancer cells. So far, MMA was tested on different cells using different nanoparticles and different field characteristics, which makes comparisons and any generalizations about the results of MMA difficult. In this paper we propose the use of giant unilamellar vesicles (GUVs) as a simple model system to study the effect of MMA on a closed lipid bilayer membrane, i.e., a basic building block of any cell. EXPERIMENTS: The GUVs were exposed to barium-hexaferrite nanoplatelets (NPLs, ~50 nm wide and 3 nm thick) with unique magnetic properties dominated by a permanent magnetic moment that is perpendicular to the platelet, at different concentrations (1-50 µg/mL) and pH values (4.2-7.4) of the aqueous suspension. The GUVs were observed with an optical microscope while being exposed to a uniaxial AMF (3-100 Hz, 2.2-10.6 mT). FINDINGS: When the NPLs were electrostatically attached to the GUV membranes, the MMA induced cyclic fluctuations of the GUVs' shape corresponding to the AMF frequency at the low NPL concentration (1 µm/mL), whereas the GUVs were bursting at the higher concentration (10 µg/mL). Theoretical considerations suggested that the bursting of the GUVs is a consequence of the local action of an assembly of several NPLs, rather than a collective effect of all the absorbed NPLs.

Formation of Fe(III)-phosphonate Coatings on Barium Hexaferrite Nanoplatelets for Porous Nanomagnets.

Amorphous coatings formed with mono-, di-, and tetra-phosphonic acids on barium hexaferrite (BHF) nanoplatelets using various synthesis conditions. The coatings, synthesized in water with di- or tetra-phosphonic acids, were thicker than that could be expected from the ligand size and the surface coverage, as determined by thermogravimetric analysis. Here, we propose a mechanism for coating formation based on direct evidence of the surface dissolution/precipitation of the BHF nanoplatelets. The partial dissolution of the nanoplatelets was observed with atomic-resolution scanning transmission electron microscopy, and the released Fe(III) ions were detected with energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy in amorphous coating. The strong chemical interaction between the surface Fe(III) ions with phosphonic ligands induces the dissolution of BHF nanoplatelets and the consequent precipitation of the Fe(III)-phosphonates that assemble into a porous coating. The so-obtained porous nanomagnets are highly responsive to a very weak magnetic field (in the order of Earth's magnetic field) at room temperature, which is a major advantage over the classic mesoporous nanomaterials and metal-organo-phosphonic frameworks with only a weak magnetic response at a few kelvins. The combination of porosity with the intrinsic magneto-crystalline anisotropy of BHF can be exploited, for example, as sorbents for heavy metals from contaminated water.

Magnetic Heating of Nanoparticles Applied in the Synthesis of a Magnetically Recyclable Hydrogenation Nanocatalyst.

Utilization of magnetic nanoparticle-mediated conversion of electromagnetic energy into heat is gaining attention in catalysis as a source of heat needed for a substrate's chemical reaction (electrification of chemical conversions). We demonstrate that rapid and selective heating of magnetic nanoparticles opens a way to the rapid synthesis of a nanocatalyst. Magnetic heating caused rapid reduction of Ru3+ cations in the vicinity of the support material and enabled preparation of a Ru nanoparticle-bearing nanocatalyst. Comparative synthesis conducted under conventional heating revealed significantly faster Ru3+ reduction under magnetic heating. The faster kinetic was ascribed to the higher surface temperature of the support material caused by rapid magnetic heating. The nanocatalyst was rigorously tested in the hydrotreatment of furfural. The activity, selectivity and stability for furfural hydrogenation to furfuryl alcohol, a valuable biobased monomer, remained high even after four magnetic recycles.

Nanocomposites comprised of homogeneously dispersed magnetic iron-oxide nanoparticles and poly(methyl methacrylate).

Nanocomposites with a high, uniform loading of magnetic nanoparticles are very desirable for applications such as electromagnetic shielding and cancer treatment based on magnetically induced hyperthermia. In this study, a simple and scalable route for preparing nanocomposites with a high, uniform loading of magnetic nanoparticles is presented. The magnetic iron-oxide nanoparticles were functionalized with a methacrylate-based monomer that copolymerized in a toluene solution with the methyl methacrylate (MMA) monomer. The resulting suspension of magnetic nanoparticles decorated with poly(methyl methacrylate) (PMMA) chains in toluene were colloidal, even in the presence of a magnetic field gradient. Nanocomposites were precipitated from these suspensions. The transmission electron microscopy investigation of the prepared nanocomposites revealed that the magnetic nanoparticles were homogeneously dispersed in the PMMA matrix, even in amounts up to 53 wt %. The uniform dispersion of the nanoparticles in the PMMA matrix was attributed to the good solvation of the grafted PMMA chains from the magnetic nanoparticles by the PMMA chains of the matrix. The nanocomposites were superparamagnetic and exhibited large values for the saturation magnetization of up to 36 emu/g. Moreover, the nanocomposite with the largest amount of incorporated nanoparticles exhibited relatively large values for the specific power loss when subjected to alternating magnetic fields, giving this material great potential for the magnetically induced hyperthermia-based treatment of cancer.

Synthesis of metastable hard-magnetic ε-Fe2O3 nanoparticles from silica-coated akaganeite nanorods.

We present a simple preparation route to obtain a nanoscale metastable hard-magnetic ε-Fe2O3 phase, using silica coated ß-FeOOH nanorods as a precursor and an annealing process. The synthesized ε-Fe2O3 nanoparticles exhibit large coercivity (HC ∼ 20 kOe at 300 K and HC ∼ 1.6 kOe at 400 K), confirming their high potential for practical applications.

Amphiphilic coatings for the protection of upconverting nanoparticles against dissolution in aqueous media.

Upconverting nanoparticles (UCNPs) of ß-NaYF4, co-doped with Yb3+ and Tm3+ and 21-36 nm large, were synthesized using a modified thermal decomposition method. The as-synthesized UCNPs were coated with oleic acid and dispersed in nonpolar media. Their morphology, size and crystal structure were analysed with transmission electron microscopy and X-ray diffraction. The UCNPs showed a fluorescence emission spectrum characteristic of Tm3+. Their dissolution in water (pH ∼ 4-5) and phosphate buffered saline (PBS, pH = 7.4) was determined from the fraction of dissolved fluoride ions using a fluoride-ion-selective electrode. The dissolution of bare UCNPs was much more prominent in PBS than in water. Two amphiphilic coatings, poly(maleic anhydride-alt-1-octadecene)-bis(hexamethylene)triamine (PMAO-BHMT) and d-α-tocopheryl polyethylene glycol succinate (TPGS) were tested for their effects on the dissolution of the UCNPs. The coatings were formed directly on the as-synthesized UCNPs as was confirmed with electrokinetic measurements, infrared spectroscopy and thermogravimetric analyses. Both coatings enabled the dispersion of UCNPs in water, and improved the fluorescence emission intensity with respect to the bare UCNPs. However, only the PMAO-BHMT coating provided an effective protection against the dissolution of the UCNPs and long-term colloidal stability in PBS, and did not show cytotoxicity in EAhy926 endothelial cells.

Harmful at non-cytotoxic concentrations: SiO2-SPIONs affect surfactant metabolism and lamellar body biogenesis in A549 human alveolar epithelial cells.

The pulmonary delivery of nanoparticles (NPs) is a promising approach in nanomedicine. For the efficient and safe use of inhalable NPs, understanding of NP interference with lung surfactant metabolism is needed. Lung surfactant is predominantly a phospholipid substance, synthesized in alveolar type II cells (ATII), where it is packed in special organelles, lamellar bodies (LBs). In vitro and in vivo studies have reported NPs impact on surfactant homeostasis, but this phenomenon has not yet been sufficiently examined. We showed that in ATII-like A549 human lung cancer cells, silica-coated superparamagnetic iron oxide NPs (SiO2-SPIONs), which have a high potential in medicine, caused an increased cellular amount of acid organelles and phospholipids. In SiO2-SPION treated cells, we observed elevated cellular quantity of multivesicular bodies (MVBs), organelles involved in LB biogenesis. In spite of the results indicating increased surfactant production, the cellular quantity of LBs was surprisingly diminished and the majority of the remaining LBs were filled with SiO2-SPIONs. Additionally, LBs were detected inside abundant autophagic vacuoles (AVs) and obviously destined for degradation. We also observed time- and dose-dependent changes in mRNA expression for proteins involved in lipid metabolism. Our results demonstrate that non-cytotoxic concentrations of SiO2-SPIONs interfere with surfactant metabolism and LB biogenesis, leading to disturbed ability to reduce hypophase surface tension. To ensure the safe use of NPs for pulmonary delivery, we propose that potential NP interference with LB biogenesis is obligatorily taken into account.

Biotransformation of copper oxide nanoparticles by the pathogenic fungus Botrytis cinerea.

Two plant pathogenic fungi, Botrytis cinerea and Alternaria alternata, isolated from crop plants, were exposed to Cu in ionic (Cu2+), microparticulate (MP, CuO) or nanoparticulate (NP, Cu or CuO) form, in solid and liquid culturing media in order to test fungal response and toxic effects of the mentioned compounds for the potential use as fungicides. B. cinerea has shown pronounced growth and lower levels of lipid peroxidation compared to A. alternata. Its higher resistance/tolerance is attributed mainly to biotransformation of CuO and Cu NPs and CuO MPs into a blue compound at the fungal/culturing media interface, recognized by Cu K-edge EXAFS analysis as Cu-oxalate complex. The pronounced activity of catechol-type siderophores and organic acid secretion in B. cinerea induce leaching and mobilization of Cu ions from the particles and their further complexation with extracellularly secreted oxalic acid. The ability of pathogenic fungus to biotransform CuO MPs and NPs hampers their use as fungicides. However the results show that B. cinerea has a potential to be used in degradation of Cu(O) nanoparticles in environment, copper extraction and purification techniques.

Sonochemically-fabricated Ga@C-dots@Ga nanoparticle-aided neural growth.

In this paper, we report the fabrication of an antibacterial material, Ga-doped C-dots on Ga nanoparticles (Ga@C-dots@Ga NPs), which is deposited on a glass substrate for neural growth. A one-step sonochemical process is applied for the simultaneous fabrication and coating of Ga@C-dots@Ga NPs using PEG 400 and molten gallium. The physical and chemical characteristics of the synthesized materials were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), fluorescence analysis, dynamic light scattering (DLS) and other techniques. SH-SY5Y cells were plated on the substrates. The effect of the Ga@C-dots@Ga NPs on the development of neurites during the initiation and elongation growth phases was studied and compared with C-dots, Ga@C-dots and Ga NPs. Our research focuses on the influence of the physical and chemical properties of composites on neurite growth. We observed that cells grown on a Ga@C-dots@Ga-coated substrate exhibit a 97% increase in the number of branches originating from the soma. We found that surface modification and particle morphology play a significant role in the neural growth.

Design and Fabrication of Magnetically Responsive Nanocarriers for Drug Delivery.

Magnetically-assisted delivery of therapeutic agents to the site of interest, which is referred to as magnetic drug targeting, has proven to be a promising strategy in a number of studies. One of the key advantages over other targeting strategies is the possibility to control remotely the distribution and accumulation of the nanocarriers after parenteral administration. However, preparation of effective and robust magnetically responsive nanocarriers based on superparamagnetic iron oxide nanocrystals (SPIONs) still represents a great scientific challenge, since spatial guidance of individual SPIONs is ineffective despite the presence of high magnetic field gradient. A strategy to overcome this issue is the clustering of SPIONs to achieve sufficient magnetic responsiveness. In this mini-review, we address current and future strategies for the design and fabrication of magnetically responsive nanocarriers based on SPIONs for magnetically-targeted drug delivery, including the underlying physical requirements, the possibility of drug loading, and the control of drug release at the targeted site.

The role of PVP in the bioavailability of Ag from the PVP-stabilized Ag nanoparticle suspension.

We assessed the bioavailability of Ag from Ag nanoparticles (NPs), stabilized with polyvinylpyrrolidone (PVP), to terrestrial isopods which were exposed to 10, 100 and 1000 µg Ag NPs/g of dry food. Different Ag species were determined in the NP suspension that was fed to isopods: (i) total Ag by atomic absorption spectroscopy, (ii) the sum of Ag-PVP complexes and free Ag+ by anodic stripping voltammetry at the bismuth-film electrode, and (iii) free Ag+ by ion-selective potentiometry. The amounts of Ag species in the consumed food were compared to the masses of Ag accumulated in the isopod digestive glands. Our results show that all three Ag species (Ag NPs, Ag-PVP complexes and free Ag+) could be the source of bioaccumulated Ag, but to various degrees depending on the exposure concentration and transformations in the digestive system. We provide a proof that (i) Ag NPs dissolve and Ag-PVP complexes dissociate in the isopod digestive tract; (ii) the concentration of free Ag+ in the suspension offered to the test organisms is not the only measure of bioavailable Ag. The type of NP stabilizer along with the NP transformations in the digestive system needs to be considered in the creation of new computational models of the nanomaterial fate.

Influence of the Synthesis Parameters on the Properties of NaYF4:Yb3+,Tm3+ Nanoparticles.

Fluorescent nanoparticles, especially fluorides, have received a great deal of interest due to their optical properties, making them suitable for applications in bio-imaging. For this reason they need to exhibit a superior chemical stability in aqueous media. We have studied the influence of the synthesis parameters on the chemical stability of NaYF(4) nanoparticles co-doped with Yb(3+) and Tm(3+). These nanoparticles have different crystal structures, and were synthesized hydrothermally or with thermal decomposition. The samples were characterized with X-ray diffraction and transmission electron microscopy. The up-conversion fluorescence of nanoparticles dispersed in water was measured at 400-900 nm. The partial dissolution of the fluorine in water was detected with an ion-selective electrode for all the samples. The dissolution of the other constituent ions was analysed with an optical emission spectrometer using inductively coupled plasma. The nanoparticles with a hexagonal crystal structure and sizes of around 20 nm that were synthesized with thermal decomposition showed a superior chemical stability in water together with a superior up-conversion fluorescence yield.