Synthesis and characterization of pure anatase TiO<Subscript>2</Subscript> nanoparticles

Pure anatase TiO₂ nanoparticles were synthesized by microwave assisted sol–gel method and further characterized by powder X-ray diffraction (XRD), energy dispersive x-ray analysis (EDAX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Visible spectrophotometer, SEM images showed that TiO₂ nanoparticles were porous structure. The XRD patterns indicated that TiO₂ after annealed at 300 °C for 3 h was mainly pure anatase phase. The crystallite size was in the range of 20–25 nm, which is consistent with the results obtained from TEM images. Microwave heating offers several potential advantages over conventional heating for inducing or enhancing chemical reactions.     

Fabrication and characterization of Ag/calcium silicate core-shell nanocomposites

The Ag/calcium silicate nanocomposite with core-shell nanostructure has been successfully synthesized using Ag solution, Ca(NO₃)₂·4H₂O and Na₂SiO₃·9H₂O in ethanol/water mixed solvents at room temperature for 48 h. Ag solution was previously prepared by microwave-assisted method in ethylene glycol (EG) at 150 °C for 10 min. The nanocomposites consisted of Ag core and an amorphous calcium silicate shell. The XRD and EDS results confirmed that the product was the Ag/calcium silicate nanocomposite. The TEM micrographs indicated that the Ag/calcium silicate nanocomposite was core-shell nanoparticles. The effects of Ca(NO₃)₂·4H₂O and Na₂SiO₃·9H₂O concentration on the shells of Ag/calcium silicate nanocomposite were investigated. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectra (EDS). This method is simple, fast and may be extended to the synthesis of the other kinds of core-shell nanocomposites.     

On the transformations of the ψ-AlCuFe icosahedral phase

In the present investigation, different alloy compositions close to the ternary composition values, where the icosahedral phase in AlFeCu is obtained, have been studied. The specimens were obtained using a rapid solidification technique with subsequent thermal treatments of 600°C, 700°C, 800°C and 900°C. The obtained specimens were characterized with X-ray diffraction patterns (XRD) and transmission electron microscopy (TEM). The experimental results show different transformations of the icosahedral phase to crystalline phases between 800°C and 700°C .The cubic β-phase is a solid solution which regulates the formation and decomposition of the ψ-Al₆Cu₂Fe phase to different crystalline phases such as the tetragonal (Al₇Cu₂Fe) and monoclinic (Al₁₃Fe₄) phases.     

Preparation and photoluminescence of surface N-doped ZnO nanocrystal

ZnO nanoparticles doped with nitrogen on surface were prepared by calcinating pure ZnO nanoparticles at 550 and 600 °C in NH₃ atmosphere. Uniform N-doped ZnO nanocrystal was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and XPS. A Strong violet photoluminescence (PL) at 400nm was observed at room temperature when excited with 300 nm light, and the emission peak increases with the increase of nitrogen atoms concentration. The violet PL originated from the electron transition from shallow donor levels of oxygen vacancies and doping nitrogen atoms to the top of valence band level.     

钯纳米颗粒的形貌控制合成

为优化钯纳米颗粒的化学还原法制备工艺,本文以氯钯酸(H₂PdCl₄)为前驱体,抗坏血酸(C₆H₈O₆)为还原剂,聚丙烯酸钠(PAAS)为表面活性剂制备钯纳米颗粒。采用正交实验探究不同工艺参数对钯纳米颗粒粒径和形貌的影响。通过 X射线粉末衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、透射电子显微镜(TEM)及电化学工作站对制备产物的结构、物相、形貌、电催化性能进行了表征。结果表明:在相同的工艺体系下,通过温度的改变,40 ℃条件下可以得到粒径大小为64.5 nm,球形度较好,分散性高的钯纳米颗粒;90 ℃条件下可以得到粒径大小为45.9 nm的立方体钯纳米颗粒。所制备的球形和立方体钯纳米颗粒对甲酸的电氧化催化活性分别为商业钯黑的1.57倍和1.49倍,在催化剂制备领域有广泛的应用前景。     

Characterization of Zr-based MCM-41 mesoporous molecular sieves obtained by microwave irradiation or hydrothermal method

Zr-based MCM-41 mesoporous molecular sieves (ZrMCM-41) were successfully synthesized by microwave irradiation method and hydrothermal method, respectively. The obtained samples were characterized by XRD, TEM, FT-IR and N₂ physical adsorption. The results show that the samples synthesized by the two different methods both possess typical hexagonal mesoporous structure of MCM-41 and high specific surface areas (over 800 m²/g). After calcination at 750°C for 3 h or hydrothermal treatment at 100°C for 6 days, the mesoporous structure of the samples still retained, however, the mesoporous ordering is poor. Under the comparable conditions, the reaction time required in the synthesis of ZrMCM-41 by microwave irradiation method was greatly reduced, and microwave irradiation method is eco-friendly and is easy to operate.     

Investigation of ethanol gas sensing properties of Dy-doped SnO<Subscript>2</Subscript> nanostructures

In this paper we report doping induced enhanced sensor response of SnO₂ based sensor towards ethanol at a working temperature of 200 °C. Undoped and dysprosium-doped (Dy-doped) SnO₂ nanoparticles were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). XRD and Raman results verified tetragonal rutile structure of the prepared samples. It has been observed that crystallite size reduced with increase in dopant concentration. In addition, the particle size has been calculated from Raman spectroscopy using phonon confinement model and the values match very well with results obtained from TEM and X-ray diffraction investigations. Dy-doped SnO₂ sensors exhibited significantly enhanced response towards ethanol as compared to undoped sensor. The optimum operating temperature of doped sensor reduced to 200 °C as compared to 320 °C for that of undoped sensor. Moreover, sensor fabricated from Dy-doped SnO₂ nanostructures was highly selective toward ethanol which signifies its potential use for commercial applications. The gas sensing mechanism of SnO₂ and possible origin of enhanced sensor response has been discussed.     

Study of preparation and magnetic properties of silica-coated cobalt ferrite nanocomposites

The structure and the magnetic properties of silica-coated cobalt ferrite nanoparticles (80 wt% CoFe₂O₄), prepared by sol–gel method and submitted to thermal treatments in the range 800–1,000 °C, were investigated through XRD, FT-IR, TEM and VSM. The effects of thermal treatment temperatures on the structure and magnetic properties of nanoparticles were examined. A silica shell thickness of about 5 nm was synthesized on top of cobalt ferrite nanoparticles. The non-crystalline silica confines the growth of cobalt ferrite nanoparticles, i.e., the particle sizes are almost independent of the thermal treatment. Saturation magnetization (Ms) was decreased slightly and coercivity (Hc) was increased, when the non-crystalline silica was coated on the surface of cobalt ferrite nanoparticles.     

Preparation and characterization of nanosized cobalt ferrite particles by co-precipitation method with citrate as chelating agent

Cobalt ferrite (CoFe₂O₄) nanoparticles were synthesized by a facile novel co-precipitation method with citrate as chelating agent. The synthesized cobalt ferrite nanoparticles were calcinated at 400, 600 and 800 °C and characterized by using XRD and TGDTA. From XRD it confirms that CoFe₂O₄ nano particles belongs to spinel type lattice of space group Fd3m. The CoFe₂O₄ nano particles calcinated at 600 °C were further characterized by using FE-SEM with EDAX, FE-TEM with SAED pattern, DLS zeta potential and CV. The linear relationship between particle size and calcination temperatures of CoFe₂O₄ nanoparticles was noticed. The surface morphology of CoFe₂O₄ studied through FE-SEM and FE-TEM indicate that the particles are found crystalline and are in cubic shape. EDAX analysis revealed the presence of Co, Fe and O. Zeta potential exposes the good stability of the prepared CoFe₂O₄ nanoparticles. Capacitance value 609 F g^?1 was observed for the scanning rate of 2 mV s^?1 from the CV study and concluded it is suitable for super capacitor application.     

The effect of molybdenum on optical properties of ZnO nanoparticles in Ultraviolet–Visible region

Zn_1?xMo_xO (x = 0.0, 0.01, 0.03, and 0.05) nanoparticles (NPs) are synthesized by using gelatin, via the sol-gel method. A calcination temperature of 600 °C is maintained for 2 h. The influence of molybdenum concentration on the structural and optical properties of these NPs is demonstrated. Synthesized NPs are characterized using X-ray diffraction (XRD), UV–vis spectroscopy, and transmission electron microscopy (TEM). XRD patterns reveal the crystallite nature of samples that exist in the hexagonal wurtzite phase. TEM images manifest the existence of nearly spherically-shaped NPs. The UV–vis spectroscopy results showed that the absorption edge of ZnO nanoparticles is red-shifted by adding molybdenum. Finally, the optical parameters of the refractive index and permittivity of the synthesized samples were calculated using Kramers-Kronig relations using the UV–vis spectra.     

Synthesis and characterization of anatase and rutile TiO2 nanorods by template-assisted method

Well-aligned anatase and rutile TiO₂ nanorods and nanotubes with a diameter of about 80–130 nm have successfully been fabricated via sol-gel template method. The prepared samples were characterized by using thermogravimetric (TG) and differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The XRD results indicated that the TiO₂ nanorods were crystallized in the anatase and rutile phases, after annealing at 400–800 °C for different periods of time from 0.2 to 10 h.     

2-Methoxycycloocta-1,5-dienyl platinum complexes as precursors for platinum nanoparticles

Thermolysis of [Pt₂(μ-OR)₂(C₈H1₂OMe)₂] (R = Me or Ac) in hexadecylamine (HDA) at 210°C under argon atmosphere gave platinum nanoparticles which were characterized by XRD, EDAX and TEM analysis. Both spherical (∼ 10 nm) and rod-like (∼ 19 nm length with aspect ratio of 2·3) face centred cubic (fcc) platinum metal nanoparticles could be isolated. The thermogravimetric analyses of these complexes revealed that they undergo a single step decomposition leading to the formation of platinum metal powder.     

Thermal stability of heat-treated flame-synthesized anatase TiO<Subscript>2</Subscript> nanoparticles

In this article, TiO₂ nanoparticles were synthesized by using O₂-enriched coflow, hydrogen, diffusion flames. We investigated the thermal stability of the flame-synthesized TiO₂ nanoparticles by examining the crystalline structures of the nanoparticles and by analyzing the photocatalytic degradations of methylene blue solutions. Also, the results were compared with those of commercial P-25 nanoparticles. The maximum centerline temperature of the flame was measured to be 1,743 °C. Under this synthesis condition, TiO₂ nanoparticles, which were spherical with diameters approximately ranging from 30 to 60 nm, were synthesized. From the XRD analyses, about 96 wt.% of the synthesized nanoparticles were anatase-phase. After the heat-treatment at 800 °C for 30 min, the synthesized TiO₂ nanoparticles showed no significant changes of their shapes and crystalline phases. On the other hand, most of the commercial particles sintered with each other and changed to the rutile-phase. Whereas the photocatalytic ability of heat-treated commercial particles deteriorated, that of the flame-synthesized particles improved. On the basis of the improved result of photocatalytic degradation of methylene blue by using the heat-treated flame-synthesized nanoparticles, it is believed that the flame-synthesized TiO₂ nanoparticles have higher thermal stability at 800 °C than the commercial particles.     

Gold nanoparticles developed in sol–gel derived apatite—bioactive glass composites

The study is focussed on synthesis and characterisation of a new sol–gel derived composite system consisting of nanocrystalline apatite, bioactive glass and gold nanoparticles, which are of interest both for regenerative medicine and for specific medical applications of the releasable gold nanoparticles. Samples dried at 110°C and then heat treated for 30 min at 300 and 500°C were investigated by thermal analysis (DTA/TG), X-ray diffraction (XRD), UV–VIS–NIR, Fourier Transform Infrared (FTIR) spectroscopy, X-ray Photoelectron(XPS) spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Gold nanoparticles and nanocrystalline apatite are developed already after heat treatment at 300°C. XPS analysis clearly revealed the presence of both metallic and ionic gold species. The development of gold nanoparticles was evidenced by UV–VIS–NIR and TEM analysis, and their size increased from few nanometers to 25 nm by increasing the treatment temperature from 300 to 500°C. The bioactivity of the samples immersed in simulated body fluid was demonstrated by XRD and SEM results.     

Synthesis and Magnetic Properties of Mn-Doped and SnO2 Nanoparticles

This paper reports the synthesis of Sn_1?x Mn _x O₂ (for x=0, 0.01, 0.05 and 0.10) nanoparticles using the co-precipitation method. X-ray diffraction (XRD) results show that all samples are single phase with tetragonal crystalline structure. Rietveld refinements from XRD patterns show that the samples present particle average sizes of 4–30 nm confirmed by scanning electron microscopy. Magnetization results for SnO₂ nanoparticles at 5% and 10% of Mn synthesized at 800?°C exhibit a ferromagnetic behavior at room temperature and an increasing of the magnetization for increasing doping concentration. On the other hand, samples synthesized at 300?°C are paramagnetic.     

Stability and transport properties of microcrystalline Si1−xGex films

The crystallization evolution of boron and phosphorus doped amorphous Si_1−xGe_x films (5×10¹⁷–5×10²⁰ cm⁻³), deposited on SiO₂/Si(001) substrates by molecular beam in high vacuum at room temperature, were studied by XRD, TEM and SEM. The amorphous Si_1−xGe_x films were fully crystallized at ∼600°C. Up to 800°C no morphology changes were observed. Between 800 and 950°C, voids and hillocks were gradually developed in the films, which consequently collapsed. The Hall concentration and mobility were characterized in the Si_1−xGe_x films, annealed between 600 and 800°C. The mobility and conductivity of p-Si_0.5Ge_0.5 films at room temperature were found to be relative high: 60 cm²/V s and 2000 (Ω cm)⁻¹, respectively.     

Effect of Zn Addition on the Reduction of the Ordering Temperature of FePt Nanoparticles

Monodisperse FePt nanoparticles with an average size of 4.11 nm were successfully synthesized via chemical co-reduction of iron acetylacetonate, Fe(acac)₃, and platinum acetylacetonate, Pt(acac)₂, by 1,2hexadecanediol as a reducing agent. Also (FePt)₈₇Zn₁₃ nanoparticles with average size of 4.24 nm were synthesized using the same method. The structural and magnetic properties of the prepared samples were respectively studied by XRD, TEM and VSM. L1₀ FePt ordered phase is formed at lower annealing temperature by addition of Zn. The (FePt)₈₇Zn₁₃ nanoparticles starts ordering after annealing at 400 °C, whereas FePt nanoparticles at 400 °C are still disordered alloys with superparamagnetic behavior. Additive Zn is very effective in decreasing the ordering temperature and enhancing the chemical ordering in (FePt)₈₇Zn₁₃ particles, So that coercivity 5200 Oe was measured for (FePt)₈₇Zn₁₃ nanoparticles annealed at 500 °C, compared with 1800 Oe for samples without Zn. This reduction in ordering temperature significantly reduces FePt particle coalescence and loss in positional order.     

Synthesis and characterization of nanocrystalline Nd3+-doped gadolinium scandium aluminum garnet powders by a gel-combustion method

Nd³⁺-doped gadolinium scandium aluminum garnet (Nd:GSAG) precursor was synthesized by a gel combustion method using metal nitrates and citric acid as raw materials. The structure and morphology of the precursor and the sintered powders were studied by means of X-ray diffraction (XRD), infrared spectroscopy (IR) and transmission electron microscopy (TEM). The results showed that the precursor transformed into pure GSAG polycrystalline phase at about 800 °C, and the powders sintered at 800–1000 °C were well-dispersed with average particle sizes in the range of 30–80 nm. Optical properties of Nd:GSAG nano-powders were characterized by using photoluminescence spectroscopy. The highest photoluminescence intensity was achieved for the powder sintered at 900 °C.     

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.     

Effects of ZrO2 addition on phase stability and photocatalytic activity of ZrO2/TiO2 nanoparticles

ZrO₂/TiO₂ nanoparticles with various Zr/Ti ratios (0–0.9) were prepared by a polymer complex solution method (PCSM). The prepared samples were characterized using transmission electron microscopy (TEM), the Brunauer, Emmett & Teller (BET) method, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FT-IR). The ZrO₂/TiO₂ photocatalyst showed a high specific area and small crystal size. The XRD pattern for the Zr/Ti = 0.1 sample indicated that the addition of ZrO₂ stabilized the anatase phase of TiO₂ up to 800 °C. The photocatalytic activity of Zr/Ti = 0.1 sample was higher than that of the TiO₂ sample and commercially available Degussa P25. The high photocatalytic activity can be attributed to stronger adsorption in the visible light region, higher specific area, smaller crystal size and increased surface OH groups.