Study on the endocytosis and the internalization mechanism of aminosilane-coated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles in vitro

In this study, the endocytosis and the internalization mechanism of aminosilane-coated Fe₃O₄ nanoparticles into human lung cancer cell line SPC-A1 was studied compared with human lung cell line WI-38 in vitro. The particle endocytosis behavior was studied by using Transmission Electron Microscope (TEM) and Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). It was found that aminosilane-coated Fe₃O₄ nanoparticles could be greatly taken up by SPC-A1 human cancer cells (202 pg iron/cell) but not by WI-38 human lung cells (13 pg iron/cell). The particles could be retained in SPC-A1 cells over a number of generations in vitro. Different endocytosis was observed by TEM after SPC-A1 cells were treated with different temperature or with/without Cytochalasin B (Inhibitor of phagocytosis) at 37 °C. No nanoparticles were taken up by SPC-A1 after the endocytosis inhibited in low temperature. Restoring the endocytosis activity at 37 °C, the process of nanoparticles from coated pit to endosomes and lysosomes was observed by TEM. Endocytosis activity was effectively inhibited by the presence of Cytochalasin B at 37 °C, while a lot of nanoparticles were uptaken to the cytoplasm of SPC-A1 cells in the control group. Our results suggest that the process of endocytosis of aminosilane-coated Fe₃O₄ nanoparticles can efficiently takes place in lung cancer cells and nanoparticles can be kept in cancer cells for generations. Phagocytosis may be involved in the internalization process of aminosilane-coated Fe₃O₄ nanoparticles.     

Structure of multilayer ZrO<Subscript>2</Subscript>/SrTiO<Subscript>3</Subscript>

Multilayered oxide heteroepitaxial systems, including that of a 1-nm-thick Y₂O₃-stabilised ZrO₂ (YSZ) sandwiched between layers of SrTiO₃ (STO) [1], have been a subject of much interest lately due to their significantly enhanced ionic conductivities as compared to the bulk materials. We aim to provide the foundation for understanding this increase in conductivity by considering the atomic configurations at the interfaces of such systems, specifically a ZrO₂/STO multilayer system. Possible stable lattice structures of pure ZrO₂ in the system are explored using a genetic algorithm in which the interatomic interactions are modelled by simple pair potentials. The energies of several of the more stable of these structures are then evaluated more accurately within density functional theory (DFT). We find that the fluorite ZrO₂ phase is unstable as a coherently strained epitaxial layer in the multilayer system. Instead, anatase-, columbite-, rutile-, and pyrite-like ZrO₂ epitaxies are found to be more stable, with the anatase-like epitaxy being the most stable structure over a wide range of chemical potential of the components. We also find a high energy metastable structure resembling the tetragonal fluorite structure which is predicted by DFT to be stabilised by SrO-terminated STO but not by TiO₂-terminated STO.     

Short-range antiferromagnetic correlations and large magnetic entropy change in (La<Subscript>0.5</Subscript>Pr<Subscript>0.5</Subscript>)<Subscript>0.67</Subscript>Ca<Subscript>0.33</Subscript>MnO<Subscript>3</Subscript>

We report a detailed study of magnetic properties in manganite (La_0.5Pr_0.5)_0.67Ca_0.33MnO₃. In contrast to the usual beliefs, it shows an abnormal upturn deviation from the Curie–Weiss law on the inverse susceptibility curve. Such a non-Griffiths-like phase is further confirmed from the inverse double integrated intensities of electron paramagnetic resonance spectrum. Because La\(^{3+}\) ions are substituted by Pr\(^{3+}\) ions with 50% concentrations, the ratio of three ions (La\(^{3+}\), Pr\(^{3+}\), Ca\(^{2+}\)) is close to 1 on A-site sublattice. As a result, some short-range antiferromagnetic (CO AFM) phases come into being in the system due to the existence of localized charge ordering states. Therefore, the upturn deviation from Curie–Weiss law originates from the appearance of short-range CO AFM correlations above \(T_{\text{C}}\). Additionally, a magnetic field-driven-metamagnetic transition is found, which gives a main contribution for the large magnetic entropy change (MEC) observed in this sample. Both the Arrott plot and the renormalized MEC curves testify that this transition belongs to first-order magnetic transition. The insignificant hysteresis loop indicate that the inevitable thermal hysteresis can be ignored in the present first-order material implying that it is a potential candidate for the cryogenic temperature magnetic refrigeration.     

Synthesis of amphiphilic [PEO(PCL)<Subscript>2</Subscript>] triarm star-shaped block copolymers: a promising system for <Emphasis Type="Italic">in cell</Emphasis> delivery

The paper reports on a simple method of synthesizing [PEO(PCL)₂] triarm star-shaped copolymers by a combination of Michael-addition type reaction and ring-opening polymerization. A Michael-addition reaction yielded a PEO end-capped by two hydroxyl groups—a [PEO(OH)₂] macroinitiator—which was used for sequential building of PCL blocks. The macroinitiator and copolymers were analyzed by FTIR, ¹H NMR spectroscopy and SEC. The self-assembly behavior of the copolymers in aqueous media was studied by UV–Vis spectroscopy. The size and morphology of the obtained micelles were determined by TEM. None of the polymers had cytotoxic effects in vitro. Cellular uptake studies showed the accumulation of neutral red loaded micelles in the perinuclear area of human hepatocellular carcinoma cells revealing a cellular uptake associated with macropinocytosis and caveolae mediated endocytosis. The accumulation had a sustained effect over 3 days pointing at the potential application of the copolymers micelles as a drug delivery system.     

Crystal structure of KNa<Subscript>3</Subscript>[(UO<Subscript>2</Subscript>)<Subscript>5</Subscript>O<Subscript>6</Subscript>(SO<Subscript>4</Subscript>)]

The crystal structure of a previously unknown compound KNa₃[(UO₂)₅O₆(SO₄)] [space group Pbca, a = 13.2855(15), b = 13.7258(18), c = 19.712(2) Å, V = 3594.6(7) ų] was solved by direct methods and refined to R ₁ = 0.055 for 3022 reflections with |F _hkl | ≥ 4σ |F _hkl |. In the structure there are five sym-metrically nonequivalent uranyl cations. They are linked by cationcation (CC) interactions to form a pentamer whose central cation is U(2)O ₂ ²⁺ forming two three-centered CC bonds. All the uranyl ions are coordinated in the equatorial plane by five O atoms, which leads to the formation of pentagonal bipyramids sharing common edges to form layers parallel to the (100) plane. The sulfate tetrahedron links the uranyl layers into a 3D framework. The K⁺ and Na⁺ cations are arranged in framework voids. A brief review of CC interactions in U(VI) compounds is presented.     

The influence of the cooling rate on bulk metallic glass formation in Mg<Subscript>80</Subscript>Cu<Subscript>15</Subscript>Y<Subscript>5</Subscript> and Mg<Subscript>80</Subscript>Cu<Subscript>10</Subscript>Y<Subscript>10</Subscript>

The Mg–Cu–Y system is known to be one of the best glass formers among the various existing magnesium alloys. The compositions chosen for the current study were Mg₈₀Cu₁₅Y₅ and Mg₈₀Cu₁₀Y₁₀. Different casting processes yielded four different microstructures that were analyzed by means of X-ray diffraction, scanning electron microscopy, high resolution scanning electron microscopy, and energy-dispersive X-ray spectroscopy chemical analysis. The different casting procedures were gravity castings of 3 mm diameter specimens into a copper mold held at different temperatures (cooled to −195 °C with the aid of liquid nitrogen, held at room temperature and heated up to 300 °C) and melt-spinning. Detailed microstructure study was then performed on the melt-spun specimen using transmission electron microscopy and high resolution transmission electron microscopy. The above-mentioned investigation revealed a crystalline rather than amorphous structure. The observed microstructure could not be explained on the basis of current models referring to the frequency of nucleation events.     

N-TiO<Subscript>2</Subscript>/g-C<Subscript>3</Subscript>N<Subscript>4</Subscript>/Up-conversion phosphor composites for the full-spectrum light-responsive deNO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> photocatalysis

The ternary composites consisted of nitrogen-doped titanium dioxide, carbon nitride and up-conversion phosphors (UP) were successfully prepared by a solvothermal method. The heterojunction could be formed when N-TiO₂ and g-C₃N₄ were combined together. The composite of N-TiO₂/g-C₃N₄@UP had excellent ultraviolet, visible and infrared light absorption, indicating the possibility for the utilization of full spectrum of solar light. When N-TiO₂ was coupled with g-C₃N₄ and up-conversion phosphors to form a composite, the visible light and NIR light absorption of the samples increased. The ternary composite N-TiO₂/g-C₃N₄@G-UP presented reasonable deNO _x performance of about 8.0% under the irradiation of IR light of 980 nm. The intensification of the photocatalysis might be realized by utilizing up-conversion phosphors, which could convert low-energy NIR light into high-energy photons (visible light) and increase the efficient irradiation on the surface of photocatalyst.     

Crystal structures of zeolites with the general formula CaAl<Subscript>2</Subscript>Si<Subscript>4</Subscript>O<Subscript>12</Subscript> · <Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O

The structures of chabazite, laumontite, and wairakite are analyzed using literature data with the aim of revealing their similar and dissimilar features. The framework of the three zeolites contain chains made up of alternating six-and four-membered rings. A distinguishing feature of chabazite is a network of oxygen-hydrogen bonds between intraframework oxygens (which link silicon (aluminum) atoms) and water molecules and between water molecules. A characteristic feature of laumontite is the ordered arrangement of the silicon and aluminum sites in the framework in the form of alternating aluminum and silicon layers. A distinguishing feature of wairakite is that there are no oxygen-hydrogen bonds between water molecules. The transition from the chabazite framework to the laumontite framework can be interpreted in terms of the ordering and displacement of aluminum and silicon atoms. In addition to the differences between the frameworks of laumontite and wairakite, which are attributable to the fact that these zeolites were formed at different temperatures and pressures, they differ in the relative arrangement of the water molecules and calcium atoms, which cannot be accounted for by different formation conditions.     

Visible photocatalytic degradation of methylene blue on magnetic semiconducting La<Subscript>0.2</Subscript>Sr<Subscript>0.7</Subscript>Fe<Subscript>12</Subscript>O<Subscript>19</Subscript>

Methylene blue (MB) is a representative of a class of dyestuffs resistant to biodegradation. This paper presents a novel photocatalytic degradation of MB by La_0.2Sr_0.7Fe₁₂O₁₉ compound, which is a traditional permanent magnet and displays a large magnetic hysteresis (M–H) loop. The remnant magnetic moment and coercive field are determined to be 52 emu/g and 5876 Oe, respectively. UV–Visible optical spectroscopy reveals that La_0.2Sr_0.7Fe₁₂O₁₉ is simultaneously a semiconductor, whose direct and indirect band gap energies are determined to be 1.47 and 0.88 eV, respectively. The near infrared band gap makes it a good candidate to harvest sunlight for photocatalytic reaction or solar cell devices. This magnetic compound demonstrates excellent photocatalytic activity on degradation of MB under visible illumination. The colour of MB dispersion solution changes from deep blue to pale white and the absorbance decreases rapidly from 1.8 down to zero when the illumination duration extends to 6 h. Five absorption bands did not make any blue shifts along with the reaction time, suggesting a one-stepwise degradation process of MB, which makes La_0.2Sr_0.7Fe₁₂O₁₉ a unique magnetic catalyst and differs from TiO₂ and other conventional catalysts.     

Dielectric and impedance spectroscopy study of Ba<Subscript>0.8</Subscript>Bi<Subscript>2.133</Subscript>Nb<Subscript>1.6</Subscript>Ta<Subscript>0.4</Subscript>O<Subscript>9</Subscript> ferroelectric ceramics,prepared by chemical route

Nanocrystalline ceramic powder of Ba_0.8Bi_2.133Nb_1.6Ta_0.4O₉ was synthesized by chemical precursor decomposition method. The single-phase formation of the compound was confirmed using an X-ray diffraction technique and was found to be a tetragonal phase at room temperature. Average crystallite size and particle size were found to be 41 and 48.5 nm, which were analyzed through XRD and TEM respectively. The dielectric constant and tangent loss were measured in the frequency range 1 kHz–1 MHz after sintering the sample at 900 °C for 4 h. The polarization behavior was studied at an applied voltage of 6.2 kV/cm. Electrical properties of the material were investigated using complex impedance spectroscopy (CIS) technique, which revealed the presence of both grain and grain-boundary effects in the materials, which is also evidenced from the scanning electron microscope image. Grain conductivity indicated Arrhenius-type thermally activated process. AC conductivity spectrum obeys Jonscher’s universal power law. The electric modulus analysis suggests the possibility of hopping mechanism for electrical processes in the system with a non-debye type relaxation, which is supported by the impedance data.     

Liquid-phase epitaxy of NdAl<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript> and Yb-doped YAl<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript>

Epitaxial layers of NaAl₃(BO₃)₄ (NAB) and YAl₃(BO₃)₄〈Yb〉 (YAB〈Yb〉) containing up to 10 at % Yb have been grown by liquid-phase epitaxy on YAB substrates. Their growth kinetics have been studied at relative supersaturations of the high-temperature solution from 2 × 10^?2 to 16 × 10^?2. The ytterbium concentration in YAB〈Yb〉 has been shown to vary little during the epitaxial process. Near the edges of the substrate, the surface morphology of the layers is complicated by vicinals, which have a spiral form in the case of YAB〈Yb〉. On \(\{ 10\overline 1 1\} \) YAB substrates, homogeneous single-crystal NAB films have been grown.     

Fluorination of Bi<Subscript>1.8</Subscript>Fe<Subscript>1.2</Subscript>SbO<Subscript>7</Subscript> pyrochlore solid solutions

A technique has been developed for fluorinating the pyrochlore oxide Bi_1.8Fe_0.2FeSbO₇, and a compound with the composition Bi_1.8Fe_1.2SbO_7–x/2F_x has been obtained. The synthesized oxyfluoride also has the pyrochlore structure (sp. gr. Fd3m), with a lattice parameter a = 10.4443(1) Å (R _wp = 5.2). It has been shown that the charge balance upon fluorine substitution for oxygen is maintained not through partial reduction of Fe³⁺ to Fe²⁺ but through the incorporation of fluorine into oxygen vacancies. The magnetic behavior of the fluorinated pyrochlore phase is determined by the persisting frustration of the octahedral sublattice, which is responsible for the development of a spin glass state below T _f = 12 K. The fluorination-induced changes in the anion sublattice led to an increase in the antiferromagnetic exchange interaction between neighboring Fe³⁺ ions and changes in the dynamic properties of the spin glass phase.     

Laser multi-layer cladding of Zr<Subscript>65</Subscript>Al<Subscript>7.5</Subscript>Ni<Subscript>10</Subscript>Cu<Subscript>17.5</Subscript> amorphous alloy on magnesium substrates

A coating about 3-mm thick of the amorphous alloy, Zr₆₅Al_7.5Ni₁₀Cu_17.5 was fabricated on magnesium substrates using the technique of laser multi-layer cladding protected under an atmosphere of argon gas. The coating exhibited a graded microstructure, which could be generally categorized into three classes: an amorphous phase, an amorphous–nanocrystalline composite, and one which is predominantly crystalline. Formation of the latter two was due to the reheating effect of the laser cladding process. With regard to properties, the microhardness and the wear resistance of the composite material were both higher than that of the monolithic amorphous material; both materials showed excellent corrosion resistance in a 3.5% NaCl solution.     

Polymorphism of ZrO<Subscript>2</Subscript> nanopowders and mechanochemical synthesis of Zr<Subscript>0.88</Subscript>Sc<Subscript>0.1</Subscript>Ce<Subscript>0.01</Subscript>Y<Subscript>0.01</Subscript>O<Subscript>1.955</Subscript>

The structure of ZrO₂ powders prepared by dehydration of zirconium hydroxide and milling (including techniques with the introduction of grinding additives, such as NaF, CaF₂, diamond, and Cu) was investigated using x-ray powder diffraction and Raman spectroscopy. Samples containing crystallites with the smallest size were synthesized in the presence of copper additives. Ceramic powders of the composition Zr_0.88Sc_0.1Ce_0.01Y_0.01O_1.955 with an improved quality for the use as solid electrolytes in fuel cells were prepared by the mechanochemical synthesis from nanoprecursors and then were characterized. An analysis of the X-ray powder diffraction patterns revealed that the symmetry of the structure of strongly aggregated nanopowders of metastable zirconia increases as a result of twinning, which is favored by a high concentration of vacancies.     

Low-loss,high-purity (TeO<Subscript>2</Subscript>)<Subscript>0.75</Subscript>(WO<Subscript>3</Subscript>)<Subscript>0.25</Subscript> glass

By melting a mixture of high-purity oxides in a platinum crucible under flowing purified oxygen, we have prepared (TeO₂)_0.75(WO₃)_0.25 glass with a total content of 3d transition metals (Fe, Ni, Co, Cu, Mn, Cr, and V) within 0.4 ppm by weight, a concentration of scattering centers larger than 300 nm in size below 10² cm⁻³, and an absorption coefficient for OH groups (λ ∼ 3 μm) of 0.008 cm⁻¹. The absorption loss in the glass has been determined to be 115 dB/km at λ = 1.06 μm, 86 dB/km at λ = 1.56 μm, and 100 dB/km at λ = 1.97 μm. From reported specific absorptions of impurities in fluorozirconate glasses and the impurity composition of the glass studied here, the absorption loss at λ ∼ 2 μm has been estimated at ≤100 dB/km. The glass has been drawn into a glass-polymer fiber, and the optical loss spectrum of the fiber has been measured.     

Graphite intercalation in the graphite-H<Subscript>2</Subscript>SO<Subscript>4</Subscript>-R (R = H<Subscript>2</Subscript>O,C<Subscript>2</Subscript>H<Subscript>5</Subscript>OH,C<Subscript>2</Subscript>H<Subscript>5</Subscript>COOH) systems

The electrochemical behavior of graphite in polar solvent-H₂SO₄ electrolytes is studied in a wide range of H₂SO₄ concentrations. The results demonstrate that, with decreasing H₂SO₄ concentration, the charging curves become smoother and shift to higher potentials, the stage index increases, and intercalation compounds are more difficult to obtain. At H₂SO₄ concentrations of 50% and lower, graphite polarization is accompanied by a significant overoxidation, as evidenced by the anomalously small intercalate layer thicknesses: 7.75–7.85 Å. Anodic polarization of graphite in electrolytes consisting of H₂SO₄ and a polar solvent (H₂O and C₂H₅OH) follows the same mechanism as in the case of the formation of graphite bisulfate. In going from water to C₂H₅OH, a less polar solvent, the intercalation threshold increases from 30 to 70% H₂SO₄. It is shown using a set of characterization techniques that, in the graphite-H₂SO₄-R (R = H₂O, C₂H₅OH) systems, the solvent is not intercalated into graphite. Stage I–III ternary graphite intercalation compounds (TGICs) are synthesized for the first time in the graphite-H₂SO₄-C₂H₅COOH system: stage I TGICs at H₂SO₄ concentrations above 70%, stage II in the range 30–70% H₂SO₄, and stage III at H₂SO₄ concentrations down to 10%. The intercalate layer thickness in the TGICs is 7.94 Å. The mechanism of TGIC formation in this system is shown to differ from those in mixtures of H₂SO₄ and other organic acids. Thermal analysis in combination with spectroscopic analysis of gaseous products provides clear evidence for intercalation of propionic acid into the TGIC and indicates that the thermal stability of this compound is lower than that of graphite bisulfate.Translated from Neorganicheskie Materialy, Vol. 41, No. 2, 2005, pp. 162–169.Original Russian Text Copyright © 2005 by Shornikova, Sorokina, Maksimova, Avdeev.     

Improvement in synthesis of (K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>)NbO<Subscript>3</Subscript> powders by Ge<Superscript>4+</Superscript> acceptor doping

In this paper, the effects of doping with GeO₂ on the synthesis temperature, phase structure and morphology of (K_0.5Na_0.5)NbO₃ (KNN) ceramic powders were studied using XRD and SEM. The results show that KNN powders with good crystallinity and compositional homogeneity can be obtained after calcination at up to 900°C for 2 h. Introducing 0.5 mol.% GeO₂ into the starting mixture improved the synthesis of the KNN powders and allowed the calcination temperature to be decreased to 800°C, which can be ascribed to the formation of the liquid phase during the synthesis.     

Phase transitions and transport properties of Cu<Subscript>3</Subscript>Co<Subscript>0.5</Subscript>Se<Subscript>2</Subscript> crystals

We have synthesized a solid solution with the composition Cu₃Co_0.5Se₂ and investigated its structural phase transitions by high-temperature X-ray diffraction on a D8 Advance diffractometer. The results demonstrate that, in the range 100–773 K, the solid solution undergoes two phase transitions: at 560 K, the low-temperature, orthorhombic phase (α) transforms into an intermediate, primitive cubic phase (β); at 765 K, the β-phase transforms into a high-temperature phase (γ, sp. gr. Fm3m). The thermoelectric power, electrical conductivity, and Hall coefficient of the solid solution were measured in the temperature range 80–350 K. The observed temperature variation of its thermoelectric power and conductivity can be accounted for under the assumption that its conduction band has an additional subband due to the cobalt atoms.     

XPS study of the initial oxidation of the bulk metallic glass Zr<Subscript>46.75</Subscript>Ti<Subscript>8.25</Subscript>Cu<Subscript>7.5</Subscript>Ni<Subscript>10</Subscript>Be<Subscript>27.5</Subscript>

The surface oxidation behaviour of the bulk metallic glass Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_27.5 was investigated in situ by using X-ray photoelectron spectroscopy (XPS). The initial stages of oxidation at room temperature were studied by exposing the clean alloy specimen surface to varying doses of pure oxygen (up to 1,000 L) in an UHV chamber. Progressive oxidation of Zr, Be and Ti was observed with increasing doses, the major species in the oxide layer being Zr(IV) and Be(II) possibly existing as ZrO₂, BeO, while Cu and Ni remained in their elemental forms. High temperature in situ oxidation in the temperature range 423–653 K for a fixed oxygen dose of 300 L was also investigated. Oxidation of Be was observed at all temperatures, while a sharp decrease in the oxidation of Zr and Ti was observed for temperatures at 573 K and above. The results show a preferential oxidation of Be and Zr at room temperature, while at higher temperatures oxidation is controlled by the reduction of oxides of Zr and Ti and the diffusion of oxygen into the alloy bulk. The role of the dissolved carbon impurity in the reduction of the oxides is discussed.     

Fabrication and characterization of epitaxial Ba<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>TiO<Subscript>3</Subscript>/LaNiO<Subscript>3 </Subscript>heterostructures

Epitaxial Ba0.6Sr0.4TiO3 (BST)/LaNiO3 (LNO) heterostructures were fabricated on LAO (100) substrates using pulsed laser deposition (PLD). Their structural properties were investigated by X-ray diffraction (XRD). The θ–2θ scans showed single crystalline BST and LNO layers with a (100) orientations perpendicular to the substrate plane. Phi scans (ϕ) on the (220) plane of BST layer indicated that the films have two in-plane orientations with respect to the substrate. The atomic force microscope (AFM) surface morphologies showed a smooth and crack-free surface with the average grain size of 55 nm and the root-mean-square (RMS) of 4.53 nm for BST films. Capacitance–voltage curves are measured. From the capacitance, a dielectric constant of 762, tunabilty of 82.81% and loss tangent of 0.032 are obtained. The current–voltage curve shows that the leakage current is 2.41 × 10⁻⁷ A/cm² under an applied voltage of 2 V.