Synthesis of Hydroxyapatite/Iron Oxide Composite and Comparison of Selected Structural,Surface, and Electrochemical Properties

The paper presents the synthesis of a hydroxyapatite/iron oxide composite utilizing the wet chemical method, as well as the comparison of several selected material characteristics. As follows from the literature reports, hydroxyapatite is a common mineral possessing numerous significant properties. Nowadays, there is an increase in the amount of research on possible modifications of this compound. The promising way to improve hydroxyapatite features is its combination with iron oxide. Particularly, there can be two forms that are distinguished, namely Fe₃O₄ and γ-Fe₂O₃. These oxides exhibit valuable properties, particularly magnetism. A combination of the mentioned materials leads to multifunctional composite formation with many potential applications, as follows from several studies. However, this area of science is not fully developed. There are still many aspects to be examined. The synthesized composite and its components were analyzed by employing the following methods. The X-ray diffraction analysis revealed formation of hydroxyapatite and Fe₂O₃ crystalline phases. Moreover, porosimetry proved a larger specific area for the composite sample in comparison with other materials. The results obtained using the SEM method confirmed an external layer of hydroxyapatite and spherical shapes of internal Fe₂O₃ particles. Furthermore, the X-ray photoelectron spectroscopy data presented characteristic peaks of Fe, Ca, P, and O atoms in all samples. The Fourier Transform Infrared spectra displayed all the specific vibrations typical of the analyzed materials. What is more, the Vibrating Sample Magnetometer method confirmed the paramagnetic nature of the samples. It could be concluded that the synthesized composite has intermediate properties between the components used in the formation process. The results suggest that these composites are superparamagnetic. This type of material architecture would be well suited for biomedical applications.     

Preparation of LuAG Powders with Single Phase and Good Dispersion for Transparent Ceramics Using Co-Precipitation Method

The synthesis of pure and well dispersed lutetium aluminum garnet (LuAG) powder is crucial and important for the preparation of LuAG transparent ceramics. In this paper, high purity and well dispersed LuAG powders have been synthesized via co-precipitation method with lutetium nitrate and aluminum nitrate as raw materials. Ammonium hydrogen carbonate (AHC) was used as the precipitant. The influence of aging time, pH value, and dripping speed on the prepared LuAG powders were investigated. It showed that long aging duration (>15 h) with high terminal pH value (>7.80) resulted in segregation of rhombus Lu precipitate and Al precipitate. By decreasing the initial pH value or accelerating the dripping speed, rhombus Lu precipitate was eliminated and pure LuAG nano powders were synthesized. High quality LuAG transparent ceramics with transmission >75% at 1064 nm were fabricated using these well dispersed nano LuAG powders.     

磁性能可控的聚（N 异丙基丙烯酰胺）基纳米复合水凝胶的制备与表征

以N--异丙基丙烯酰胺（NIPAM）为单体、焦磷酸钠改性的无机锂皂石（Clay-S）为物理交联剂,制备了温敏性的纳米复合水凝胶（NC gels）,通过原位化学沉淀法引入Fe3O4纳米粒子,制备了聚（N-异丙基丙烯酰胺）基磁性纳米复合水凝胶（MNC gels）。使用傅里叶变换红外光谱（FT-IR）、X射线衍射（XRD）、扫描电子显微镜（SEM）、能量色散X射线光谱（EDX）、差示扫描量热分析（DSC）、综合物性测量系统（PPMS）等测试方法表征了凝胶网络的结构形态、磁性粒子的晶型及其分布、凝胶的温敏性和磁性能。重点研究了制备过程中的浸泡液铁盐浓度、预聚液的单体浓度及黏土含量对凝胶磁性能的影响,并对上述影响因素进行了分析和模拟。结果表明：MNC gels同时具有温敏性和磁敏性,且其磁性能受浸泡液铁盐浓度、预聚液的单体浓度及黏土含量影响;根据影响因素显著性水平建立了可预测MNC gels磁性能的模型,使磁性能的可控制备成为可能。     

Fabricated Flexible Composite for a UV-LED Color Filter and Anti-Counterfeiting Application of Calcium Molybdate Phosphor Synthesized at Room Temperature

Crystalline CaMoO₄ and rare-earth-doped CaMoO₄:RE³⁺ (RE = Tb, Eu) phosphors were synthesized at room temperature using a co-precipitation method. The crystal structure of the synthesized powder was a tetragonal structure with a main diffraction peak (112) phase. When CaMoO₄ was excited at 295 nm, it showed a central peak of 498 nm and light emission in a wide range of 420 to 700 nm. Rare-earth-ion-doped CaMoO₄:Tb³⁺ was excited at 288 nm and a green light emission was observed at 544 nm, and CaMoO₄:Eu³⁺ was excited at 292 nm and a red light emission was observed at 613 nm. To take advantage of the light-emitting characteristics, a flexible composite was manufactured and a color filter that could be used for UV-LEDs was manufactured. In addition, it was suggested that an ink that could be checked only by UV light could be produced and applied to banknotes so as to prevent counterfeiting.     

Efficient Green Synthesis of (Fe3O4) and (NiFe2O4) Nanoparticles Using Star Anise (Illicium verum) Extract and Their Biomedical Activity against Some Cancer Cells

Magnetite Fe₃O₄ and spinel (2:1) and (4:1) NiFe₂O₄ magnetic nanoparticles (MNPs) were prepared by simple and affordable co-precipitation methods using an extract of star anise (Illicium verum) as a green reducing agent. The morphology and chemical composition of these MNPs were confirmed by field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, UV–visible spectroscopy, and X-ray diffraction (XRD). The synthesized magnetite Fe₃O₄ and spinel (2:1) and (4:1) NiFe₂O₄ MNPs were in the size range of 0.1–1 µm. The MNPs had irregular clustered platelets (magnetite Fe₃O₄) and pyramidal structures (spinel (2:1) and (4:1) NiFe₂O₄ NPs). The average sizes of the synthesized magnetite Fe₃O₄, and spinel (2:1) and (4:1) NiFe₂O₄ MNPs calculated using XRD analysis were 66.8, 72.5, and 72.9 nm, respectively. In addition to the characteristic absorption peaks of magnetite Fe₃O₄, those of spinel (2:1) and (4:1) NiFe₂O₄ MNPs were detected at ~300–350 nm and ~700 nm, respectively. Overall, the results of this study indicate that the synthesized magnetite Fe₃O₄, and spinel (2:1) and (4:1) NiFe₂O₄ MNPs showed high biomedical activities against liver carcinoma cells and non-small lung adenocarcinoma cells.     

Silicate Removal in Aluminum Hydroxide Co-Precipitation Process

The removal mechanisms of silicate using an aluminum hydroxide co-precipitation process was investigated and compared with an adsorption process, in order to establish an effective and validated method for silicate removal from wastewater. Adsorption isotherms, XRD and FT-IR analyses showed that silicate uptake occurred by adsorption to boehmite for initial Si/Al molar ratios smaller than two, but by precipitation of poorly crystalline kaolinite for the ratios larger than two, in both co-precipitation and adsorption processes. Silicate was removed by two steps: (i) an initial rapid uptake in a few seconds; and (ii) a slow uptake over several hours in both processes. The uptake rate in the first step was higher in the co-precipitation process than in adsorption process, presumably due to increased silicate adsorption to boehmite and rapid precipitation of kaolinite. These results suggest that silicate removal using aluminum salts could be effectively achieved if the pH adjustment and aluminum concentration are strictly controlled.     

共沉淀法制备复合Al_2O_3-Cr_2O_3超微粒子粉末

探讨了文题的方法,研究了溶液的pH值、反应物浓度及配比、反应温度对合成的Al_2O_3-Cr_2O_3粒子的粒径、粒径分布以及组成的影响规律。结果表明,合成粒子的最佳pH值范围为4.4～5.0;粒子的组成仅取决于反应物初始浓度的配比,改变反应物初始浓度及配比可以十分有效地控制粒子的性能;反应温度对粒子的粒径及分布影响很小。制得的复合Al_2O_3-Cr_2O_3超微粒子呈球形、组成均一。     

Structure,Luminescence, and Magnetic Properties of Crystalline Manganese Tungstate Doped with Rare Earth Ion

The precursor prepared by co-precipitation method was sintered at various temperatures to synthesize crystalline manganese tungstate (MnWO₄). Sintered MnWO₄ showed the best crystallinity at a sintering temperature of 800 °C. Rare earth ion (Dysprosium; Dy³⁺) was added when preparing the precursor to enhance the magnetic and luminescent properties of crystalline MnWO₄ based on these sintering temperature conditions. As the amount of rare earth ions was changed, the magnetic and luminescent characteristics were enhanced; however, after 0.1 mol.%, the luminescent characteristics decreased due to the concentration quenching phenomenon. In addition, a composite was prepared by mixing MnWO₄ powder, with enhanced magnetism and luminescence properties due to the addition of dysprosium, with epoxy. To one of the two prepared composites a magnetic field was applied to induce alignment of the MnWO₄ particles. Aligned particles showed stronger luminescence than the composite sample prepared with unsorted particles. As a result of this, it was suggested that it can be used as phosphor and a photosensitizer by utilizing the magnetic and luminescent properties of the synthesized MnWO₄ powder with the addition of rare earth ions.     

Organized Silica Films Generated by Evaporation-Induced Self-Assembly as Hosts for Iron Oxide Nanoparticles

In this work, we prepared oriented mesoporous thin films of silica on various solid substrates using the pluronic block copolymer P123 as a template. We attempted to insert guest iron oxide (Fe_xO_y) nanoparticles into these films by two different methods: (a) by co-precipitation—where iron precursors are introduced in the synthesis sol before deposition of the silica film—and subsequent oxide production during the film calcination step; (b) by preparing and calcining the silica films first then impregnating them with the iron precursor, obtaining the iron oxide nanoparticles by a second calcination step. We have examined the structural effects of the guest nanoparticles on the silica film structures using grazing incidence X-ray scattering (GISAXS), high-resolution transmission electron spectroscopy (HRTEM), spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), and Raman microscopy. Formation of nanoparticles by co-precipitation may induce substantial changes in the film structure leading, in our adopted process, to the appearance of lamellar ordering in the calcination stage. On the contrary, impregnation-based approaches perturb the film structures much more weakly, but are also less efficient in filling the pores with nanoparticles.     

Room Temperature Co-Precipitation Synthesis of Magnetite Nanoparticles in a Large pH Window with Different Bases

Magnetite nanoparticles (Fe₃O₄) represent the most promising materials in medical applications. To favor high-drug or enzyme loading on the nanoparticles, they are incorporated into mesoporous materials to form a hybrid support with the consequent reduction of magnetization saturation. The direct synthesis of mesoporous structures appears to be of interest. To this end, magnetite nanoparticles have been synthesized using a one pot co-precipitation reaction at room temperature in the presence of different bases, such as NaOH, KOH or (C₂H₅)₄NOH. Magnetite shows characteristics of superparamagnetism at room temperature and a saturation magnetization (Ms) value depending on both the crystal size and the degree of agglomeration of individual nanoparticles. Such agglomeration appears to be responsible for the formation of mesoporous structures, which are affected by the pH, the nature of alkali, the slow or fast addition of alkaline solution and the drying modality of synthesized powders.