The effect of the silicon incorporation on the hydroxylapatite structure. A neutron diffraction study

Nominal stoichiometric hydroxylapatite, Ca₁₀(PO₄)₆(OH)₂ and silicon-substituted HA, containing 0.9 wt% in silicon, were prepared by the ceramic method. The samples were analyzed by elemental chemical analysis, Fourier transformed infrared spectroscopy (FTIR) and the structural study was carried out by Rietveld analysis combining powder X-ray (XRD) and neutron diffraction (ND). The refinements of the occupancies at the 4e Wyckoff position shows that the OH⁻/O²⁻ ratio is higher when SiO₄⁴⁻ substitutes PO₄³⁻. The observation of the Fourier maps points out that also the HPO₄²⁻ formation from PO₄³⁻ is also higher when Si is included in the HA structure. For the first time, the atomic coordinates for the H atoms of HPO₄²⁻ anions are provided.     

Characterization and corrosion properties of Ti‐O/HA composite coatings on Mg‐Zn alloy

Biodegradable magnesium alloys have been widely investigated in the field of biomaterials because they can be gradually dissolved and absorbed by the human body without long‐term existence. However, it was found that bare magnesium implants suffered from rapid corrosion. Surface modification is applied to improve the corrosion resistance and biocompatibility of magnesium implants. In this study, Ti‐O/HA composite coatings including typical flakes and nanofibers were fabricated on the Mg‐Zn alloy. The Ti‐O films were deposited on the magnesium alloy by direct current magnetron sputtering, and subsequently coated with HA flakes and nanofibers by electrochemical deposition, respectively. The obtained coatings were investigated by X‐ray diffraction, Fourier Transform Infrared spectroscopy and scanning electron microscopy. The corrosion resistance was evaluated by potentiodynamic polarization and hydrogen evolution tests in simulated body fluid at 37 °C. The results show that the compact Ti‐O films are composed of particles within the size of 100 nm, the outermost HA coatings are predominantly composed of HA and doped with Na⁺, Mg²⁺ ions and functional groups. The stronger diffraction and broader peak in nanofibers than typical flakes around 25.8° are ascribed to the preferential growth in orientation (002). The morphology of HA coatings changed from typical flakes into nanofibers with the addition of NaF, the mechanism to explain the difference is also discussed. The corrosion resistance was improved significantly by the coatings, the corrosion rates in the 10 days were 4.13, 1.77, 0.96 and 0.85 mm/y, respectively. Copyright © 2011 John Wiley & Sons, Ltd.     

Calcium Phosphate Hybrid Nanoparticles: Self‐Assembly Formation,Characterization, and Application as an Anticancer Drug Nanocarrier

Calcium phosphate hybrid nanoparticles (CaP‐HNPs) have been synthesized in aqueous solution through self‐assembly by using two oppositely charged polyelectrolytes (poly(diallyldimethylammonium chloride) (PDADMAC) and poly(acrylate sodium) (PAS)) as dual templates. First, the PAS/Ca²⁺ and PDADMAC/PO₄^3? complexes form through electrostatic interactions and then two complexes self‐assemble into CaP‐HNPs after mixing them together. The as‐prepared CaP‐HNPs exhibit a spherical morphology with a narrow size distribution, good dispersibility, and high colloidal stability in water. The CaP‐HNPs are explored as a nanocarrier for the anticancer drug docetaxel (Dtxl). The CaP‐HNPs show excellent biocompatibility, high drug‐loading capacity, pH‐sensitive drug‐release behavior, and high anticancer effect after being loaded with Dtxl. Therefore, the as‐prepared CaP‐HNPs are promising drug nanocarriers for cancer therapy.     

Influence of sputter power on structural and electrical properties of TiO2 films for Al/TiO2/Si gate capacitors

Titanium dioxide (TiO₂) thin films were deposited onto p‐Si substrates held at room temperature by reactive Direct Current (DC) magnetron sputtering at various sputter powers in the range 80–200 W. The as‐deposited TiO₂ films were annealed at a temperature of 1023 K. The post‐annealed films were characterized for crystallographic structure, chemical binding configuration, surface morphology and optical absorption. The electrical and dielectric properties of Al/TiO₂/p‐Si structure were determined from the capacitance–voltage and current–voltage characteristics. X‐ray diffraction studies confirmed that the as‐deposited films were amorphous in nature. After post‐annealing at 1023 K, the films formed at lower powers exhibited anatase phase, where as those deposited at sputter powers > 160 W showed the mixed anatase and rutile phases of TiO₂. The surface morphology of the films varied significantly with the increase of sputter power. The electrical and dielectric properties on the air‐annealed Al/TiO₂/p‐Si structures were studied. The effect of sputter power on the electrical and dielectric characteristics of the structure of Al/TiO₂/p‐Si (metal‐insulator‐semiconductor) was systematically investigated. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of inorganic ions on the photocatalytic degradation of humic acid

The article studies on the effects of six inorganic ions (Ca²⁺, Mg²⁺, Cl^?, SO ₄ ^2? , H₂PO ₄ ^? , and HCO ₃ ^? ) on titanium dioxide (TiO₂)-based photocatalytic degradation of humic acid (HA). We focus on the effects of the inorganic ions on HA characters, adsorption of HA on TiO₂ and photocatalytic degradation of HA. The results indicate that Ca²⁺ and Mg²⁺ with HA can form complexes which can decrease the solubility of HA, and then increase the HA adsorbed on TiO₂. However, the complex is more difficult to be degraded than HA. The effects of Cl^? and SO ₄ ^2? are closely related to their influences on HA solubility. The solubility changes of HA to some extent can enhance the adsorption of HA on TiO₂, and promote the photocatalytic degradation. Nevertheless, great solubility decreasing of HA can weaken the photocatalytic degradation. HCO ₃ ^? and H₂PO ₄ ^? can inhibit the photocatalytic degradation process seriously, because HCO ₃ ^? and H₂PO ₄ ^? are the strong scavengers of hydroxyl radicals, and can weaken the adsorption of HA on TiO₂ due to adsorption competition.     

Inter‐diffusion effects in as‐deposited Al/Ni polycrystalline multi‐layers

Al/Ni multi‐layers, deposited by magnetron sputtering at room temperature have been studied by complementary techniques; XPS, sputter depth profiling, electron‐induced X‐ray emission spectroscopy (XES) and X‐ray diffraction (XRD). XPS depth profile technique evidenced an atomic diffusion dominated by Ni atoms. Moreover, the Ni diffusion results in the formation of an amorphous phase with a stoichiometry close to the Al₃Ni aluminide. Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation and characterization of Pd-Ag alloy composite membrane with magnetron sputtering

A Pd-Ag (24 wt%) alloy composite membrane was prepared by the magnetron sputtering. A γ-Al_2O_3 membrane was synthesized by the sol-gel method and used as substrate of the Pd-Ag alloy film. The process parameters of the magnetron sputtering were optimized as a function of the compactness of the Pd-Ag alloy film. The best membrane with a thickness of 1 μm was produced with a sputtering pressure of 2.7 Pa and a substrate temperature of 400℃. The membrane had an H_2/N_2 permselectivity of 51.5--1000 and an H_2 permeation rate of 0.036--1.17×10~(-5)cm~3/cm~2·s· Pa, depending on operating conditions.     

Intermetallic GaPd2 Thin Films for Selective Hydrogenation of Acetylene

The preparation of single-phase and catalytically active GaPd₂ coatings was accomplished via DC magnetron sputtering using an intermetallic sputter target. Thin and uniform layers were deposited on borosilicate glass, Si(111) and planar as well as micro-structured stainless steel foils. The specimens were examined regarding their phase composition, film morphology and microstructure. Thin films of different layer thickness were catalytically characterized in the semi-hydrogenation of acetylene, which was conducted at 473 K and a feed gas composition of 0.5 vol.% C₂H₂, 5 vol.% H₂ as well as 50 vol.% C₂H₄ in helium. Pre-reduction of the catalyst was found to be essential to enhance the catalytic selectivity. Sputtered GaPd₂ showed a high selectivity of 73 % for the hydrogenation to ethylene at conversion levels above 80 %. The surface-specific activity was strongly increased to 8.97 mol_acetylene · (A₀ · h)^–1 compared to bulk- or nanoscale GaPd₂ (1.93 and 0.30 mol_acetylene · (A₀ · h)^–1, respectively) caused by the high specific surface area of the thin films.     

Characterization and cytocompatibility of polydopamine on MAO‐HA coating supported on Mg‐Zn‐Ca alloy

Magnesium has been suggested as a potential biodegradable metal for the usage as orthopaedic implants. However, high degradation rate in physiological environment remains the biggest challenge, impeding wide clinical application of magnesium‐based biomaterials. In order to reduce its degradation rate and improve the biocompatibility, micro‐arc oxidation coating doped with HA particles (MAO‐HA) was applied as the inner coating, and polydopamine (PDA) film was synthesized by dopamine self‐polymerization as the outer coating. The microstructure evolution of the coating was characterized using scanning electron microscopy (SEM), atomic force microscope (AFM), X‐ray diffraction analyses (XRD), Fourier transform infrared spectroscopy (FT‐IR), and X‐ray photoelectron spectroscopy (XPS). The results showed that PDA film had covered the entire surface of MAO‐HA coating and the pore size of MAO‐HA coating decreased. The root mean square (RMS) roughness of PDA/MAO‐HA coatings was approximately 106.46 nm, which was closer to the optimum surface roughness for cellular attachment as compared with MAO‐HA coatings. Contact angle measurement indicated that the surface wettability had been transformed from hydrophobic to hydrophilic due to the introduction of PDA. The PDA/MAO‐HA coatings exhibited better corrosion resistance in vitro, with the self‐corrosion potential increasing by 150 mV and the corrosion current density decreasing from 2.09 × 10^?5 A/cm ² to 1.46 × 10^?6 A/cm ² . In hydrogen evolution tests, the corrosion rates of the samples coated with PDA/MAO‐HA and MAO‐HA were 4.40 and 5.95 mm/y, respectively. MTS assay test and cell‐surface interactions experiment demonstrated that PDA/MAO‐HA coatings exhibited good cellular compatibility and could promote the adhesion and proliferation of MC3T3‐E1 cells.     

Organic / inorganic bioactive materials Part I: Synthesis, structure and in vitro assessment of collagen/silicocarnotite biocoatings

The silicocarnotite, as an inorganic part of the coatings, has been synthesized using a polystep sol-gel method. The chemical composition of the prepared silicocarnotite sol is described as 58.12 CaO, 29.42 P₂O₅, 12.45 SiO₂ (wt%), where Ca/P+Si = 1,67. The acid soluble type I collagen, as an organic part of the obtained coatings, was mixed with silicocarnotite powder in a weight ratio of 25:75 and 75:25 weight ratio without cross-linkage. The acidity of the obtained mixture was readjust with 25% NH₄OH to pH = 9.0. The mixture was then dried at 37°C for 12 h. The growth of B-type carbonate containing hydroxyapatite (B-type CO₃HA) in which CO₃ ²⁺→PO₄ ³⁻ on the surface of collagen/silicocarnotite coatings soaked in 1.5 simulated body fluid (1.5 SBF) was observed. The nucleation of B-type CO₃HA was estimated on the obtained coatings after 3 days immersion in 1.5 SBF. The negatively charged carboxylate groups from the collagen surface may be responsible for the HA deposition. This was confirmed by the “red shift” of carboxylate groups of collagen molecules in the FTIR spectra. After soaking in 1.5 SBF, the morphology of prepared coatings and HA formation was observed by SEM.     

Enhanced photocatalytic activity of Ag3PO4 via Fullerene C60 modification

Fullerene‐C₆₀‐modified Ag₃PO₄ photocatalysts (C₆₀/Ag₃PO₄) were prepared via facile chemical precipitation. The structures, morphology and photocatalytic properties of C₆₀/Ag₃PO₄ were characterized by X‐ray diffractometry (XRD), transmission electron microscopy (TEM), photoluminescence (PL) spectrometry, and ultraviolet–visible (UV–vis) absorption spectrometry. C₆₀/Ag₃PO₄ exhibits considerably higher photocatalytic activity for degradation of Methyl Orange. The degradation conversion reached 93% after 8 min of light irradiation. Besides, the enhancement of photocatalytic activity could be attributed to the active species ?OH_, which can be ascribed to strong synergistic effect between Fullerene C₆₀ and Ag₃PO₄.     

pH‐Dependent Degradation of Layered Black Phosphorus: Essential Role of Hydroxide Ions

The practical application of layered black phosphorus (LBP) is compromised by fast decomposition in the presence of H₂O and/or O₂. The role of H₂O is controversial. Herein, we propose a hydroxide ion (OH^?)‐initiated degradation mechanism for LBP to elucidate the role of H₂O. We found that LBP degraded faster in alkaline solutions than in neutral or acidic solutions with or without O₂. Degradation rates of LBP increased linearly from pH 4 to 10. Density functional theory (DFT) calculations showed that OH^? initiated the decomposition of LBP through breaking the P?P bond and forming a P?O bond. The detection of hypophosphite, generated from OH^? reacting with P atoms, confirmed the hypothesis. Protons acted in a way distinctive from OH^?, by inducing deposition/aggregation or forming a cation–π layer to protect LBP from degradation. This work reveals the degradation mechanism of LBP and thus facilitates the development of effective stabilization technologies.     

Degradation of poly(acrylates) under SF5+ primary ion bombardment studied using time‐of‐flight secondary ion mass spectrometry. 3. Poly(hydroxyethyl methacrylate) with chemical derivatization

Molecular depth profiling of polymers by secondary ion mass spectrometry (SIMS) has focused on the use of polyatomic primary ions due to their low penetration depth and high damage removal rates in some polymers. This study is the third in a series of systematic characterizations of the effect of polymer chemistry on degradation under polyatomic primary ion bombardment. In this study, time‐of‐flight SIMS (ToF‐SIMS) was used to assess 5 keV SF₅⁺‐induced damage of ～90 nm thick spin‐cast poly(2‐hydroxyethyl methacrylate) (PHEMA) and ～130 nm thick trifluoroacetic anhydride‐derivatized PHEMA (TFAA‐PHEMA) films. The degradation of these polymers under extended SF₅⁺ bombardment (～2 × 10¹⁴ ions cm^?2) was compared to determine the effect of the pendant group chemistry on their degradation. The sputter rate and ion‐induced damage accumulation rate of PHEMA were similar to a poly(n‐alkyl methacrylate) of similar pendant group length, suggesting that the addition of a terminal hydroxyl group to the alkyl pendant group does not markedly change the stability of poly(n‐alkyl methacrylates) under SF₅⁺ bombardment. The sputter rate and ion‐induced damage accumulation rate of TFAA‐PHEMA were much higher than a poly(n‐alkyl methacrylate) of similar pendant group length, suggesting that derivatization of the terminal hydroxyl group can significantly reduce degradation of the polymer under SF₅⁺ bombardment. This result is in good agreement with the literature on the thermal and radiation‐induced degradation of fluorinated poly(alkyl methacrylates), which suggests that the electron‐withdrawing fluorinated pendant group increases the probability of depolymerization. Copyright © 2004 John Wiley & Sons, Ltd.     

Development of Na+-sensitive membranes based on sputtered Na-Al-Si glasses

Na⁺-sensitive microdevices are of increasing interest for integration in microanalytical systems e.g. for biomedical applications or for industrial process control. In order to produce ultra thin Na⁺-sensitive layers with fixed and reproducible composition and, in particular, defined Na concentration by means of RF sputtering, an off-axis geometry of a magnetron with cylindrical target was chosen for minimizing back-sputtering effects from the already deposited material. With this inverted cylindrical magnetron (ICM) it was possible to obtain reproducible and controllable sodium aluminosilicate glass layers on semiconductor substrates. Several surface and thin layer analytical techniques were applied for characterization of the membranes and for stoichiometry control. Especially by the non-destructive nuclear reaction analysis method a constant Na profile throughout the glass layer and — together with AES depth profiles — the diffusion barrier effect of an Si₃N₄ interface layer could be verified. Electrochemical measurements proved Nernstian sensitivity down to 10^–4 M Na⁺ in solutions of pH 7, supporting sufficient stability and reproducibility of the sputtered Na⁺-sensitive layers.     

Dye degradation studies of Mo‐doped TiO2 thin films developed by reactive sputtering

TiO₂ thin films with various Mo concentrations have been deposited on glass and n‐type silicon (100) substrates by this radio‐frequency (RF) reactive magnetron sputtering at 400°C substrate temperature. The crystal structure, surface morphology, composition, and elemental oxidation states of the films have been analyzed by using X‐ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and X‐ray photoelectron spectroscopy, respectively. Ultraviolet‐visible spectroscopy has been used to investigate the degradation, transmittance, and absorption properties of doped and undoped TiO₂ films. The photocatalytic degradation activity of the films was evaluated by using methylene blue under a light intensity of 100 mW cm⁻². The X‐ray diffraction patterns show the presence of anatase phase of TiO₂ in the developed films. X‐ray photoelectron spectroscopy studies have confirmed that Mo is present only as Mo⁶⁺ ions in all films. The Mo/TiO₂ band gap decreases from ~3.3 to 3.1 eV with increasing Mo dopant concentrations. Dye degradation of ~60% is observed in Mo/TiO₂ samples, which is much higher than that of pure TiO₂.     

New horizons in sputter depth profiling inorganics with giant gas cluster sources: Niobium oxide thin films

X‐ray photoelectron spectroscopy is used to study a wide variety of material systems as a function of depth (“depth profiling”). Historically, Ar⁺ has been the primary ion of choice, but even at low kinetic energies, Ar⁺ ion beams can damage materials by creating, for example, nonstoichiometric oxides. Here, we show that the depth profiles of inorganic oxides can be greatly improved using Ar giant gas cluster beams. For NbO_x thin films, we demonstrate that using Ar_x⁺ (x = 1000‐2500) gas cluster beams with kinetic energies per projectile atom from 5 to 20 eV, there is significantly less preferential oxygen sputtering than 500 eV Ar⁺ sputtering leading to improvements in the measured steady state O/Nb ratio. However, there is significant sputter‐induced sample roughness. Depending on the experimental conditions, the surface roughness is up to 20× that of the initial NbO_x surface. In general, higher kinetic energies per rojectile atom (E/n) lead to higher sputter yields (Y/n) and less sputter‐induced roughness and consequently better quality depth profiles. We demonstrate that the best‐quality depth profiles are obtained by increasing the sample temperature; the chemical damage and the crater rms roughness is reduced. The best experimental conditions for depth profiling were found to be using a 20 keV Ar₂₅₀₀⁺ primary ion beam at a sample temperature of 44°C. At this temperature, there is no, or very little, reduction of the niobium oxide layer and the crater rms roughness is close to that of the original surface.     

Highly Efficient Photocatalytic Remediation of Simulated Polycyclic Aromatic Hydrocarbons (PAHs) Contaminated Wastewater under Visible Light Irradiation by Graphene Oxide Enwrapped Ag3PO4 Composite.

Effective removal of polycyclic aromatic hydrocarbons (PAHs) from wastewater before their discharge into the environment is an ever pressing requirement. In this study, for the first time, simulated PAHs contaminated wastewater was photocatalytically remediated with graphene oxide (GO) enwrapped silver phosphate as visible light‐driven photocatalysts. The GO/Ag₃PO₄ photocatalysts exhibited superior photocatalytic activity and stability compared with pure Ag₃PO₄, g‐C₃N₄ and TiO₂ (P25). The degradation efficiency of naphthalene, phenanthrene and pyrene could reach 49.7%, 100.0% and 77.9%, rspectively within 5 min irradiation. The apparent rate constants of photocatalytic degradation of 3 wt% GO/Ag₃PO₄ composite photocatalyst were 0.14, 1.21 and 2.46 min⁻¹ for naphthalene, phenanthrene and pyrene, respectively. They were about 1.8, 1.5 and 2.0 times higher than that of pure Ag₃PO₄, and much higher than that of g‐C₃N₄ and TiO₂. Meanwhile, the efficiencies of 44.6%, 95.2% and 83.8% were achieved for naphthalene, phenanthrene and pyrene degradation even after 5 times of recycling in the GO/Ag₃PO₄‐PAHs photocatalysis system. Reactive species of ∙O₂⁻ and h⁺ were considered as the main participants for oxidizing naphthalene, phenanthrene and pyrene.     

Nanotome cluster bombardment to recover spatial chemistry after preparation of biological samples for SIMS imaging

A C₆₀⁺ cluster ion projectile is employed for sputter cleaning biological surfaces to reveal spatio-chemical information obscured by contamination overlayers. This protocol is used as a supplemental sample preparation method for time of flight secondary ion mass spectrometry (ToF-SIMS) imaging of frozen and freeze-dried biological materials. Following the removal of nanometers of material from the surface using sputter cleaning, a frozen-patterned cholesterol film and a freeze-dried tissue sample were analyzed using ToF-SIMS imaging. In both experiments, the chemical information was maintained after the sputter dose, due to the minimal chemical damage caused by C₆₀⁺ bombardment. The damage to the surface produced by freeze-drying the tissue sample was found to have a greater effect on the loss of cholesterol signal than the sputter-induced damage. In addition to maintaining the chemical information, sputtering is not found to alter the spatial distribution of molecules on the surface. This approach removes artifacts that might obscure the surface chemistry of the sample and are common to many biological sample preparation schemes for ToF-SIMS imaging.     

Kinetics and mechanism of reaction between zirconium‐lactate and pentane‐2,4‐dione in excess lactate

The kinetics of the reaction of pentane‐2,4‐dione (HA) with Zr^IV has been studied at 25.0°C in an excess lactate (L^?) media. The equilibrium reaction was found to be: Zr₂L₆+HA?HL+Zr₂AL₅. The equilibrium was approached from either direction and a plausible mechanism has been proposed with kinetic constants, but individual reactivities of the keto and the enol tautomers of pentane‐2,4‐dione could not be apportioned. However, it was found that both the uncatalyzed and acid‐catalyzed paths contribute to the reverse reaction. But 2‐thenoyltrifluoroacetone (HT) forms a stronger chelate with Zr^IV, so its reaction with less reactive Zr₂L₅(OH₂) could not be detected; reactivity of the more reactive Zr₂L₅(OH₂)(OH) could be found. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 725–729, 2011     

Laser‐induced Graphene‐based Non‐enzymatic Sensor for Detection of Hydrogen Peroxide

In this study, a laser‐induced graphene (LIG) loaded platinum nanoparticles (PtNPs) was prepared for precise, rapid and non‐enzymatic electrochemical detection of hydrogen peroxide (H₂O₂). The commercial PI films were used as the substrate of LIG. In order to improve the electrochemical performance of LIG, a layer of PtNPs catalyst was fabricated through a magnetron sputtering process on the surface of LIG (PtLIG). Under optimized conditions, a linear relationship between H₂O₂ reduction current and H₂O₂ concentration was recorded, the correlation coefficient R² is 0.9919 with the detection limit of 0.1 μM (S/N=3) and the sensitivity of 248.4 μA mM^?1cm^?2. Moreover, the PtLIG exhibits excellent selectivity, reproducibility and repeatability. Because of these remarkable advantages, we believe that PtLIG will provide a wider range of applications in biosensors and bioelectronic devices.