Yingxia Wang

Comparative study on corrosion resistance and in vitro biocompatibility of bulk nanocrystalline and microcrystalline biomedical 304 stainless steel

OBJECTIVES SUS 304 stainless steels have been widely used in orthodontics and implants such as archwires, brackets, and screws. The purpose of present study was to investigate the biocompatibility of both the commercial microcrystalline biomedical 304 stainless steel (microcrystalline 304ss) and novel-fabricated nanocrystalline 304 stainless steel (nanocrystalline 304ss). METHODS Bulk nanocrystalline 304ss sheets had been successfully prepared by microcrystalline 304ss plates using severe rolling technique. The electrochemical corrosion and ion release behavior immersion in artificial saliva were measured to evaluate the property of biocorrosion in oral environment. The cell lines of murine and human cell lines from oral and endothelial environment were co-cultured with extracts to evaluate the cytotoxicity and provide referential evidence in vivo. RESULTS The polarization resistance trials indicated that nanocrystalline 304ss is more corrosion resistant than the microcrystalline 304ss in oral-like environment with higher corrosion potential, and the amount of toxic ions released into solution after immersion is lower than that of the microcrystalline 304ss and the daily dietary intake level. The cytotoxicity results also elucidated that nanocrystalline 304ss is biologically compatible in vitro, even better than that of microcrystalline 304ss. SIGNIFICANCE Based on the much higher mechanical and physical performances, nanocrystalline 304ss with enhanced biocorrosion property, well-behaved in vitro cytocompatibility can be a promising alternative in orthodontics and fixation fields in oral cavity.

PKU-9: An Aluminogermanate with a New Three-Dimensional Zeolite Framework Constructed from CGS Layers and Spiro-5 Units

PKU-9, an aluminogermanate synthesized hydrothermally, crystallizes in a new zeolite framework composed of CGS layers and spiro-5 units. It contains three-dimensional intersecting 10- and 8-ring channels, has a low framework density, and represents the first example of a porous aluminogermanate containing spiro-5 units.

In vitro study on Zr-based bulk metallic glasses as potential biomaterials

With pure Ti and pure Zr as controls, the corrosion resistance, ion release behavior, and in vitro biocompatibility of Be-containing Zr₄₁Ti₁₄Cu₁₂Ni₁₀Be₂₃ bulk metallic glass (BMG) (LM1), Zr₄₄Ti₁₁Cu₁₀Ni₁₀Be₂₅ BMG (LM1b), and Be-free Zr₅₇Nb₅Cu₁₅.₄Ni₁₂.₆Al₁₀ BMG (LM106) were investigated in terms of electrochemical measurements in simulated body fluid (SBF) with pH value 7.4 and artificial saliva (AS) with pH value 6.3, and 3-[4,4-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay using L929 and NIH3T3 cells, aiming to assess the feasibility of Zr-based BMGs as potential biomaterial. It was found that LM1b showed superior corrosion resistance to LM106 and LM1 in both SBF and AS, and comparable with pure Ti and pure Zr. After 7200 s immersion, a two-layer structure oxide film was formed on LM1, LM1b, and pure Zr surfaces, while one-layer structure oxide film was formed on LM106 and pure Ti surfaces. The pitting corrosion potentials of LM1b were much higher than that of LM1, LM106, and pure Zr, resulting in very few ions releasing into the electrolytes. No Be ion could be detected but a little amount of Cu ion was detected for LM106, LM1, and LM1b after immersion in Dulbeccos modified Eagles medium for 72 h at 37 °C. The indirect cytotoxicity results show that LM106, LM1, and LM1b extracts had no cytotoxicity to L929 and NIH3T3 cells. The direct cytotoxicity results show that cells could adhere well on the Zr-based BMG surface as in pure Ti and Zr. Lower cell proliferation rate of LM106 and LM1 is observed when compared with LM1b, which was found to be caused by Cu ion releasing rather than by Be ion.

Synthesis and structure of an aluminum borate chloride consisting of 12-membered borate rings and aluminate clusters.

A new aluminum borate chloride (PKU-8) was synthesized in a flux of boric acid, and the structure was established using powder X-ray diffraction techniques. PKU-8 contains an unusual framework structure of a large cage consisting of 12-membered borate rings [B 12O 30] and aluminate octahedra clusters [Al 7O 24].

Syntheses and crystal structures of two new bismuth hydroxyl borates containing [Bi2O2]2+ layers: Bi2O2[B3O5(OH)] and Bi2O2[BO2(OH)].

Two new bismuth hydroxyl borates, Bi(2)O(2)[B(3)O(5)(OH)] (I) and Bi(2)O(2)[BO(2)(OH)] (II), have been synthesized under hydrothermal conditions. Their structures were determined by single-crystal and powder X-ray diffraction data, respectively. Compound I crystallizes in the orthorhombic space group Pbca with the lattice constants of a = 6.0268(3) Å, b = 11.3635(6) Å, and c = 19.348(1) Å. Compound II crystallizes in the monoclinic space group Cm with the lattice constants of a = 5.4676(6) Å, b = 14.6643(5) Å, c = 3.9058(1) Å, and β = 135.587(6)°. The borate fundamental building block (FBB) in I is a three-ring unit [B(3)O(6)(OH)](4-), which connects one by one via sharing corners, forming an infinite zigzag chain along the a direction. The borate chains are further linked by hydrogen bonds, showing as a borate layer within the ab plane. The FBB in II is an isolated [BO(2)(OH)](2-) triangle, which links to two neighboring FBBs by strong hydrogen bonds, resulting in a borate chain along the a direction. Both compounds contain [Bi(2)O(2)](2+) layers, and the [Bi(2)O(2)](2+) layers combine with the corresponding borate layers alternatively, forming the whole structures. These two new bismuth borates are the first ones containing [Bi(2)O(2)](2+) layers in borates. The appearance of Bi(2)O(2)[BO(2)(OH)] (II) completes the series of compounds Bi(2)O(2)[BO(2)(OH)], Bi(2)O(2)CO(3), and Bi(2)O(2)[NO(3)(OH)] and the formation of Bi(2)O(2)[B(3)O(5)(OH)] provides another example in demonstrating the polymerization tendency of borate groups.

Generation of high-flux attosecond extreme ultraviolet continuum with a 10 TW laser

We report a laser system that delivers 15 fs pulses with 200 mJ energy at a 10 Hz repetition rate. The broadband spectrum extending from 700 nm to 900 nm was obtained by seeding a two-stage Ti:sapphire chirped-pulse power amplifier with sub-mJ white-light pulses from a gas-filled hollow-core fiber. With this laser, an extreme ultraviolet (XUV) super-continuum supporting 230 as isolated attosecond pulses at 35 eV was generated using the generalized double optical gating technique. The XUV pulse energy was ∼100 nJ at the exit of the argon gas target.

In vitro and in vivo studies on Ti-based bulk metallic glass as potential dental implant material

In this study, a high glass forming system, Ti41.5Zr2.5Hf5Cu37.5Ni7.5Si1Sn5 (TZHCNSS) bulk metallic glass (BMG), is studied in terms of microstructure, surface analysis, mechanical properties, corrosion resistance, in vitro cytotoxicity and in vivo biocompatibility. It is found that the as-prepared TZHCNSS samples are fully amorphous by XRD and TEM observations, as well as DSC curve. Comparing with pure Ti, TZHCNSS BMG shows superior mechanical properties with higher hardness and better wear resistance. Due to the oxide film formed on its surface, TZHCNSS BMG shows great corrosion resistance close to pure Ti in electrochemical measurements. The pitting corrosion potential in artificial saliva solution is much higher than that in SBF solution. The indirect and direct cytotoxicity results show that TZHCNSS extracts had obvious low cell viability on both L929 and NIH3T3 cells. However, the in vivo testing results proved that TZHCNSS BMG could integrate with bone tissue, showing excellent osseointegration.

Syntheses, Structure, and Luminescent Properties of Novel Hydrated Rare Earth Borates Ln(2)B(6)O(10)(OH)(4)center dot H(2)O (Ln = Pr, Nd, Sm, Eu, Gd, Dy, Ho, and Y)

Ln(2)B(6)O(10)(OH)(4)•H(2)O (Ln = Pr, Nd, Sm-Gd, Dy, Ho, and Y), a new series of hydrated rare earth borates, have been synthesized under hydrothermal conditions. A single crystal of Nd analogue was used for the structure determination by X-ray diffraction. It crystallizes in the monoclinic space group C2/c with lattice constants a = 21.756(4), b = 4.3671(9), c = 12.192(2) Å, and β = 108.29(3)°. The other compounds are isostructural to Nd(2)B(6)O(10)(OH)(4)•H(2)O. The fundamental building block (FBB) of the polyborate anion in this structure is a three-membered ring [B(3)O(6)(OH)(2)](5-). The FBBs are connected by sharing oxygen atoms forming an infinite [B(3)O(5)(OH)(2)](3-) chain, and the chains are linked by hydrogen bonds, establishing a two-dimensional (2-D) [B(6)O(10)(OH)(4)•H(2)O](6-) layer. The 2-D borate layers are thus interconnected by Ln(3+) ions to form the complex three-dimensional structure. Ln(2)B(6)O(10)(OH)(4)•H(2)O dehydrates stepwise, giving rise to two new intermediate compounds Ln(2)B(6)O(10)(OH)(4) and Ln(2)B(6)O(11)(OH)(2). The investigation on the luminescent properties of Gd(2-2x)Eu(2x)B(6)O(10)(OH)(4)•H(2)O (x = 0.01-1.00) shows a high efficiency of Eu(3+) f-f transitions and the existence of the energy transfer process from Gd(3+) to Eu(3+). Eu(2)B(6)O(10)(OH)(4)•H(2)O and its two dehydrated products, Eu(2)B(6)O(10)(OH)(4) and Eu(2)B(6)O(11)(OH)(2), present the strongest emission peak at 620 nm ((5)D(0) → (7)F(2) transition), which may be potential red phosphors.

Multicolour and up-conversion fluorescence of lanthanide doped Vernier phase yttrium oxyfluoride nanocrystals

Multicolour and up-conversion fluorescent nanocrystals of lanthanide doped orthorhombic yttrium oxyfluorides were prepared via a facile precursor route for the first time. The stepwise fabrication procedure involves room-temperature coprecipitation of Y3+ ions with CO32− and F− in water and subsequent thermal decomposition. Powder X-ray diffraction studies confirmed that all of the undoped and lanthanide ion-doped samples annealed at 400 °C were pure Vernier phase adopting an orthorhombic structure. The crystal structure, synthetic details, morphologies, and luminescence properties of the nanocrystals were investigated by means of TEM, thermal and spectroscopic measurements. In the structure, Y atoms occupy four crystalline sites with different coordination by O2−/F−, giving rise to complex environments for the doping of rare earth ions. Green emission bands were observed from the Tb3+ doped samples under UV excitation (λex = 284, 377 nm), while the Eu3+ doped nanocrystals exhibited bright red emission upon both UV and blue irradiation (λex = 381, 465 nm). Those nanocrystals codoped with Yb3+/Er3+, Yb3+/Ho3+ and Yb3+/Tm3+ show intense red, green and blue up-conversion fluorescence respectively upon irradiation at 980 nm with a diode laser. The Vernier phase yttrium oxyfluoride phosphors have the potential for use in applications such as bioprobes, optical nanodevices, and chromatic displays.

Correlation between corrosion performance and surface wettability in ZrTiCuNiBe bulk metallic glasses

The corrosion properties of two Zr-based bulk metallic glass, Zr41Ti14Cu12Ni10Be23 (LM1) and Zr44Ti11Cu10Ni10Be25 (LM1b) were investigated by electrochemical measurements in simulated body fluid with pH value 7.4. With much lower current density and higher impedance values, as well as higher pitting potential, LM1b showed superior corrosion resistance to LM1. Under identical sample preparation and testing conditions, the difference in corrosion performance is found to relate closely to their surface wettability difference, as contact angle tests showed that LM1b is more hydrophobic than LM1. The excess free volume was measured and found having a close correlation with the wettability or the surface energy.