Preparation and optical characterization of hydroxyapatite and ceramic systems with titanium and zirconium formed by dry high-energy mechanical alloying

Calcium phosphate-based bioceramics, mainly in the form of hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂—HAP, is the main mineral constituent of teeth and bones with excellent biocompatibility with hard and muscle tissues. These materials exhibit several problems of handling and fabrication, which can be overcome by mixing them with a suitable binder. The dry milling process of fabrication of HAP presents the advantage that melting is not necessary and the powder obtained is nanocrystalline. The high efficiency of the dry milling process opens a new way to produce commercial amount of nanocrystalline HAP and others bioceramic. In this work dry mechanical alloying has been used to produce nanocrystalline powders of HAP using three different experimental procedures (HAPA: Ca(H₂PO₄)₂ + Ca(OH)₂; HAPB: Ca(H₂PO₄)₂ + CaCO₃; and HAPC: CaHPO₄ + CaCO₃). HAP was obtained after 5, 10 and 15 h of milling in the reactions HAPA and HAPB, but it is necessary 15 h of milling in the reaction HAPC to obtain HAP. In order to improve the mechanical properties of HAP calcium phosphate ceramics, with titanium (CaP-Ti) and zirconium (CaP-Zr), have been prepared by dry ball milling using two different experimental procedures: CaP-Ti1: Ca(H₂PO₄)₂ + TiO₂; CaP-Ti2: CaHPO₄ + TiO₂; and CaP-Zr1: Ca(H₂PO₄)₂ + ZrO₂, CaP-Zr2: CaHPO₄ + ZrO₂. The calcium titanium phosphate phase, CaTi₄P₆O₂₄, was obtained in the reaction CaP-Ti1. In the reactions CaP-Ti2, CaP-Zr1 and CaP-Zr2, it was not observed the formation of any calcium phosphate phase even after 15 h of dry mechanical alloying. The milled HAP and the ceramics systems obtained were characterized by X-ray powder diffraction, infrared and Raman scattering spectroscopy.     

Hydrothermal synthesis of precursors of neodymium oxide nanoparticles

The nanometric precursors of neodymium oxide of various morphologies were prepared via a hydrothermal reaction route. The precursors and their thermal evolution to neodymium oxide phase were characterised by means of X-ray diffraction (XRD), transmission electron microscopy (TEM, HRTEM), thermal analysis (TG, DTA, EGA-MS), FTIR and atomic force microscopy (AFM). It was found that the reaction conditions (temperature, pressure) played a key role for the product formation of desired morphology and structure. At mild conditions (140 °C) precursor with unusual fibrous morphology and Nd(OH)_2.45(Ac)_0.550.45H₂O stoichiometry was obtained. Upon heating this phase transformed, via intermediate cubic oxide, into trigonal Nd₂O₃ at 800 °C. Nd(OH)₃ hydroxide obtained at severe conditions (180 °C) transformed upon heating into cubic Nd₂O₃ phase at about 500 °C and this phase was stabilised even at 800 °C. The fibrous precursors appeared to be a convenient material for preparation of homogeneous thin coatings on planar substrates is shown.     

Selective Synthesis of Primary Anilines from NH3 and Cyclohexanones by Utilizing Preferential Adsorption of Styrene on the Pd Nanoparticle Surface

Dehydrogenative aromatization is one of the attractive alternative methods for directly synthesizing primary anilines from NH₃ and cyclohexanones. However, the selective synthesis of primary anilines is quite difficult because the desired primary aniline products and the cyclohexanone substrates readily undergo condensation affording the corresponding imines (i.e., N‐cyclohexylidene‐anilines), followed by hydrogenation to produce N‐cyclohexylanilines as the major products. In this study, primary anilines were selectively synthesized in the presence of supported Pd nanoparticle catalysts (e.g., Pd/HAP, HAP=hydroxyapatite, Ca₁₀(PO₄)₆(OH)₂) by utilizing competitive adsorption unique to heterogeneous catalysis; in other words, when styrene was used as a hydrogen acceptor, which preferentially adsorbs on the Pd nanoparticle surface in the presence of N‐cyclohexylidene‐anilines, various structurally diverse primary anilines were selectively synthesized from readily accessible NH₃ and cyclohexanones. The Pd/HAP catalyst was reused several times though its catalytic performance gradually declined.     

Synergistic Effects of Fluorine and Carbonate on Cd2+Binding Properties of Apatites

Abstract

Most of the studies on heavy metals binding ability of apatites have been carried out on hydroxyapatites (HAP). (HA_p)[Ca₁₀(P0₄)₆(OH)₂]. As the chemical characteristics of apatite depend substantially on the substitutions in its structure, the apatites with F substitution for OH and CO₃ ² for PO₄ ³ were studied.     

Au/FeOx-羟基磷灰石催化CO氧化反应中羟基磷灰石和FeOx的作用

近期我们报道了Au/FeO_x-羟基磷灰石(HAP, Ca₁₀(PO₄)₆(OH)₂)催化剂应用于CO氧化反应的研究结果,该催化剂不仅具有很高的低温CO氧化活性和反应稳定性, 同时也具有很好的高温抗烧结性能, 即使600℃焙烧后依然能够维持很好的CO氧化反应活性. 为了进一步研究Au/FeO_x-HAP催化CO氧化反应中HAP和FeO_x的作用, 本文对该催化剂进行了更加深入的表征. X射线光电子能谱结果表明, HAP能与Au和FeO_x形成强相互作用, 进而在高温条件下稳定Au和FeO_x纳米粒子. 根据原位漫反射红外结果, FeO_x则主要通过改变反应路径和中间产物的方式起到促进催化剂CO氧化活性的作用. 结合透射电镜, 穆斯堡尔谱和原位漫反射红外结果可知, Au/FeO_x-HAP催化剂良好的反应稳定性源于其优异的抗碳酸盐累积能力.     

In Situ Engineering of Intracellular Hemoglobin for Implantable High‐Performance Biofuel Cells

The key challenge for the broad application of implantable biofuel cells (BFCs) is to achieve inorganic–organic composite biocompatibility while improving the activity and selectivity of the catalysts. We have fabricated nanoengineered red blood cells (NERBCs) by an environmentally friendly method by using red blood cells as the raw material and hemoglobin (Hb) embedded with ultrasmall hydroxyapatite (HAP, Ca₁₀(PO₄)₆(OH)₂) as the functional BFC cathode material. The NERBCs showed greatly enhanced cell performance with high electrocatalytic activity, stability, and selectivity. The NERBCs maintained the original biological properties of the natural cell, while enhancing the catalytic oxygen reduction reaction (ORR) through the interaction between ?OH groups in HAP and the Hb in RBCs. They also enabled direct electron transportation, eliminating the need for an electron‐transfer mediator, and showed catalytic inactivity for glucose oxidation, thus potentially enabling the development of separator‐free BFCs.     

Synthesis of hydroxyapatite by hydrolysis of α-Ca<Subscript>3</Subscript>(PO<Subscript>4</Subscript>)<Subscript>2</Subscript>

Conditions for hydroxyapatite (HAP) synthesis in aqueous solutions by hydrolysis of α-Ca₃(PO₄)₂ were studied. Temperature exerts a substantial effect on the rate of α-Ca₃(PO₄)₂ hydrolysis and also changes the morphology of the reaction products. At 40 °C, the plate-like intersecting (perpendicular to the surface of the initial particles) crystals of HAP grow. Their maximum size after the 24-h hydrolysis is 1–2 µm. Needle like HAP crystals are formed upon boiling of the suspension. The morphology observed for the HAP particles agrees well with the conclusions obtained by analysis of the kinetics of tricalcium phosphate hydrolysis.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 78–85, January, 2005.     

Formation of Mg(OH)<Subscript>2</Subscript> nanowhiskers on LTA zeolite surfaces using a sol–gel method

A facile three step sol–gel-precipitation process is used to synthesize Mg(OH)₂ nanowhiskers on micron-sized zeolite 5A particle surfaces at room temperature. The putative amorphous gelation product, Mg(OH)_n(OR)_2−n, forms first by a controlled hydrolysis and condensation reaction involving magnesium isopropoxide and water, ultimately leading to precipitation to form Mg(OH)₂ structures on the zeolite surface. The optimum conditions for one dimensional Mg(OH)₂ whisker formation are found to be six times the stoichiometric amount of water using 1 M HCl as the catalyst for the sol–gel reaction. The one-dimensional Mg(OH)₂ whiskers have an average diameter of 5–10 nm and length of 50–100 nm. The zeolite micropores are not affected by the Mg(OH)₂ whiskers formed on the surface. The surface roughened zeolite 5A, with a Mg(OH)₂ content of about 9 wt%, showed improved adhesion between the zeolite and the polymer in a mixed-matrix composite membrane.     

Fabrication of mesoporous ZnO nanosheets from precursor templates grown in aqueous solutions

Mesoporous ZnO nanosheets were successfully prepared by pyrolytic transformation of zinc carbonate hydroxide hydrate, Zn₄CO₃(OH)₆·H₂O. The nanosheets were initially formed as assemblies on glass substrates during chemical bath deposition (CBD) in aqueous solutions of urea and zinc acetate dihydrate, zinc chloride, zinc nitrate hexahydrate, or zinc sulfate heptahydrate at 80°C. It was key to induce heterogeneous nucleation of Zn₄CO₃(OH)₆·H₂O by promoting a gradual hydrolysis reaction of urea and controlling the degree of supersaturation of zinc hydroxide species. Morphology of Zn₄CO₃(OH)₆·H₂O was largely influenced by the anions present in the CBD solutions. The Zn₄CO₃(OH)₆·H₂O nanosheets were transformed into wurtzite ZnO by heating at 300°C in air without losing the microstructural feature.     

Tetrakis(trimethysilyl)hypophosphate P2O2(OTMS)4: Synthesis,reactivity and application as flame retardant

The preparation of tetrakis(trimethy‐ silyl)hypophosphate, P₂O₂(OTMS)₄ (TMS = SiMe₃), which is easily obtained from cheap starting materials, is reported. Reaction with protic substrates (H₂O, alcohols) proceeds under stepwise cleavage of silylethers, ROTMS, and formation of hypophosphoric acid, P₂O₂(OH)₄. Amines in the presence of molecular sieves lead to desilylation and formation of ammonium salts of the [P₂O₂(OTMS)₂(O⁻)₂] dianion. On cotton fabrics, P₂O₂(OTMS)₄ hydrolyzes to give P₂O₂(OH)₄ within about 1 h when exposed to air, and this compound acts as an efficient flame retardant (limiting oxygen index >26%) even at low loadings (P content <3%). © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:721–731, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20373     

纳米羟基磷灰石纳米管的一种简便制备方法及其对溶液中重金属离子的吸附

采用简便的方法合成了20~40 nm长、56 m^2·g^-1的比表面积的羟基磷灰石纳米管(HAP)。然后用制备的HAP纳米管在水溶液中同时吸附Pb^2+、Cd^2+、Cu^2+、Co^2+、Ni^2+、Zn^2+和Hg^2+,其具有高的吸附能力,并能实现快速去除。此外,制备的HAP纳米管对7种重金属离子的脱附率均小于1%,表现出较强的稳定性。实验数据采用Langmuir等温线模型和Freundlich等温线模型进行分析。2个方程的应用结果表明,吸附平衡最适合Langmuir模型,单层饱和吸附能力为958.28 mg·g^-1,具有较好的吸附性能。通过能量色散X射线光谱(EDS)和X射线衍射(XRD)图进一步研究了吸附机理,结果表明,当溶液中Pb^2+离子数量足够时,吸附机理为Pb取代了HAP中的Ca,形成了更稳定的Pb5(PO4)3(OH)。上述实验研究预测了利用HAP纳米管处理含铅废水在环境污染治理中的可行性。     

High-Quality Thin Films of UiO-66-NH2 by Coordination Modulated Layer-by-Layer Liquid Phase Epitaxy

We report the fabrication of macroscopically and microscopically homogeneous, crack-free metal-organic framework (MOF) UiO-66-NH₂ (UiO: Universitetet i Oslo; [Zr₆O₄(OH)₄(bdc-NH₂)₆]; bdc-NH₂²⁻: 2-amino-1,4-benzene dicarboxylate) thin films on silicon oxide surfaces. A DMF-free, low-temperature coordination modulated (CM), layer-by-layer liquid phase epitaxy (LPE) using the controlled secondary building block approach (CSA). Efficient substrate activation was determined as a key factor to obtain dense and smooth coatings by comparing UiO-66-NH₂ thin films grown on ozone and piranha acid-activated substrates. Films of 2.60 μm thickness with a minimal surface roughness of 2 nm and a high sorption capacity of 3.53 mmol g⁻¹ MeOH (at 25 °C) were typically obtained in an 80-cycle experiment at mild conditions (70 °C, ambient pressure).     

Synthesis of a Magnetic Carnation-like Hydroxyapatite/Basic Calcium Carbonate Nanocomposite and Its Adsorption Behaviors for Lead Ions in Water

Calcium-enriched compounds have great potential in the treatment of heavy-metal contaminated wastewater. Preparing stable basic calcium carbonate (BCC), which is a calcium-enriched compound, and applying it in practice is a great challenge. This work investigated the formation process of hierarchical hydroxyapatite (HAP)/BCC nanocomposites and their adsorption behaviors regarding lead ions (Pb²⁺). The morphology of the HAP/BCC nanocomposite was controlled by the addition of monododecyl phosphate (MDP). The carnation-like HAP/BCC nanocomposite was achieved with the addition of 30 g of MDP. The carnation-like HAP/BCC nanocomposite had a high Pb²⁺ adsorption capacity of 860 mg g⁻¹. The pseudo-second-order and Freundlich model simulation results indicated that the adsorptions of Pb²⁺ on the nanocomposites belonged to the chemisorption and multilayer adsorption processes. The main effective adsorption components for the nanocomposites were calcium-enriched HAP and BCC. Through the Ca²⁺ ions exchanging with Pb²⁺, the HAP and BCC phases were converted to hydroxyl-pyromorphite (Pb-HAP) and hydrocerussite (Pb₃(CO₃)₂(OH)₂), respectively. The carnation-like HAP/BCC nanocomposite has great potential in the treatment of heavy metal ions. This facile method provides a new method for preparing a stable HAP/BCC nanocomposite and applying it in practice.     

Ethylene glycol-modified cobalt and iron oxalates as precursors for the synthesis of oxides as extended microsized and nanosized objects

The reactions of ethylene glycol with iron and cobalt oxalates upon heating in air are reported. Heat treatment of mixtures of oxalate powders with ethylene glycol yields new compounds (solvates) via the replacement of the water molecules in the oxalate structure by ethylene glycol molecules: MC₂O₄ · 2H₂O + HOCH₂CH₂OH = MC₂O₄(HOCH₂CH₂OH)+2H₂O↑. The crystals resulting from this reaction are elongated, and their shape is inherited by their thermolysis products. Thermolysis in air yields microwhiskers and nanowhiskers of Fe₂O₃ and Co₃O₄, and thermolysis in an inert atmosphere affords Fe₃O₄ and Co whiskers. The thermolysis of FeC₂O₄(HOCH₂CH₂OH) in helium yields a new structural modification of FeC₂O₄ as an intermediate product. The resulting compounds and their thermolysis products were characterized by X-ray powder diffraction, microscopy, IR spectroscopy, and thermogravimetric and chemical analyses. The particle shape and size were determined by scanning electron microscopy.     

Coordination chemistry of ester-functionalized cp ligands: synthesis and catalytic activity of [Rh{CpCO2(CHPh)2OH}(NBD)] and [Rh{CpCO2(CH2)3OH}(NBD)]

Two new sodium hydroxyalkoxycarbonylcyclopentadienide salts Na[rac-CpCO₂(CHPh)₂OH] (1) and Na[(2S,3S)-CpCO₂(CHPh)₂OH] (2) were prepared by reaction of NaCp with the five-membered cyclic carbonates cis-4,5-diphenyl-1,3-dioxolan-2-one and (4S,5S)-4,5-diphenyl-1,3-dioxolan-2-one. The reaction of these salts with [Rh(NBD)Cl]₂ gave [Rh{rac-CpCO₂(CHPh)₂OH}(NBD)] (3) and (−)-[Rh{(2S,3S)-CpCO₂(CHPh)₂OH}(NBD)] (4) whose catalytic activity in the hydroformylation of hex-1-ene and styrene has been investigated and compared with that of the previously reported rhodium complexes [Rh{CpCO₂(CHR)₂OH}(NBD)] (R=H, Me). In addition we also discuss some preliminary results regarding the behavior of these complexes in the hydrogenation of the same substrates. The reactivity of NaCp toward the six-membered cyclic carbonate 1,3-dioxan-2-one has also been studied and it has been found that the reaction leads to two cyclopentadienide anions [CpCO₂(CH₂)₃OH]⁻ (5) and [CpCO₂(CH₂)₃OC(O)O(CH₂)₃OH]⁻ (6) in amounts strictly dependent on the carbonate/NaCp stoichiometric ratio.     

Morphology-controlled nonaqueous synthesis of anisotropic lanthanum hydroxide nanoparticles

The preparation of lanthanum hydroxide and manganese oxide nanoparticles is presented, based on a nonaqueous sol-gel process involving the reaction of La(OiPr)₃ and KMnO₄ with organic solvents such as benzyl alcohol, 2-butanone and a 1:1 vol. mixture thereof. The lanthanum manganese oxide system is highly complex and surprising results with respect to product composition and morphology were obtained. In dependence of the reaction parameters, the La(OH)₃ nanoparticles undergo a shape transformation from short nanorods with an average aspect ratio of 2.1 to micron-sized nanofibers (average aspect ratio is more than 59.5). Although not directly involved, KMnO₄ plays a crucial role in determining the particle morphology of La(OH)₃. The reason lies in the fact that KMnO₄ is able to oxidize the benzyl alcohol to benzoic acid, which presumably induces the anisotropic particle growth in [0 0 1] direction upon preferential coordination to the ±(1 0 0), ±(0 1 0) and ±(−110) crystal facets. By adjusting the molar La(OiPr)₃-to-KMnO₄ ratio as well as by using the appropriate solvent mixture it is possible to tailor the morphology, phase purity and microstructure of the La(OH)₃ nanoparticles. Postsynthetic thermal treatment of the sample containing La(OH)₃ nanofibers and β-MnOOH nanoparticles at the temperature of 800 °C for 8 h yielded polyhedral LaMnO₃ and worm-like La₂O₃ nanoparticles as final products.     

Adsorption monitoring of phospho-l-serine on hydroxyapatite

The adsorption of the aminoacid phospho-l-serine (PLS) on the surface of hydroxyapatite {Ca₅(PO₄)₃OH, HAP}, was investigated using streaming potential measurements. Solutions saturated with respect to HAP, containing different concentrations of PLS, were brought in contact under carefully controlled flow conditions through plugs made of well dispersed HAP powder. The measurement of PLS adsorption during the equilibration of the solute with the HAP substrate, showed a plateau regime corresponding, according to geometrical considerations, to monolayer surface coverage. The PLS uptake measurements on HAP suggested that it is possible to monitor in situ adsorption during the monolayer surface coverage measuring the streaming potential of HAP. Analysis of the surface potential measurements suggested that during the monolayer surface coverage step, the negatively charged (HL^2?) PLS species were adsorbed. The adsorbed HL^2? was located at the inner Helmholtz plane of the electrical double layer, forming surface complexes with the positively charged ≡CaOH ₂ ⁺ sites on the surface of HAP. The rate constants of adsorption and desorption were calculated from the kinetics of adsorption of PLS on HAP.     

Structural Diversity of F-Element Monophthalocyanine Complexes

The preparation and structural characterization of a series of lanthanide and uranium(IV) phthalocyanine halide complexes were achieved by reaction of the corresponding metal halide with Li₂Pc. A preliminary survey of their reactivity includes ring reduction of Li(THF)₄[PcUCl₃] with KC₈ leading to the first structurally characterized Pc⁴⁻ actinide complex, hydrolysis of PcDyCl(DMSO) to PcDyOH(H₂O)₃ and preparation of a unique trimeric triangular Li(PcDy)₃(OH)₄(H₂O) cluster.     

Hydroxidcarbonate von Magnesium und Zink

Zusammenfassung Nach der Methode der Homogenfällung durch Komplex-acidolyse wurden Mg₅(OH)₂(CO₃)₄·4H₂O und Zn₅(OH)₆(CO₃)₂ formelgerecht und röntgenographisch gut kristallin dargestellt. Während das erstere Präparat, so gewonnen, dem Mineral Hydromagnesit sofort entspricht, wird das letztere dem Mineral Hydrozinkit erst durch Altern bei 100° unter der Mutterlauge völlig analog.

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The compounds Mg₅(OH)₂(CO₃)₄·4H₂O and Zn₅(OH)₆(CO₃)₂ with exact stoichiometric composition were prepared by the method of homogeneous precipitation and complex-acidolysis. They were obtained in a well crystalline state, as shown by their X-ray powder diagrams. While the first of these preparations corresponds to hydromagnesite, the latter needs ageing at 100° in the mother liquor to become completely analogous to the mineral hydrozinkite.

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4. Mitt.:E. Hayek undP. Inama, Mh. Chem.96, 85 (1965).     

碳酸钙晶须合成过程中可溶性磷酸盐的作用机理研究

以可溶性磷酸盐为控制剂,一步碳化法制备了文石相碳酸钙晶须。借助于XRD和FTIR,分析了可溶性磷酸盐在碳酸钙晶须合成过程中的作用机理。研究结果表明：通入CO₂进行碳化反应前,可溶性磷酸盐与Ca(OH)₂反应生成了热力学上最稳定的磷酸钙化合物——羟基磷灰石;在通入CO₂初期,[CO₃^2-(OH)]进入到羟基磷灰石的晶格,部分替代[PO₄^3-],生成碳酸羟基磷灰石,然后以此为结晶中心诱导文石相的异相成核,Ca²⁺、CO₃^2-不断叠加,进而生长为碳酸钙晶须。