Methanobactin-Mediated One-Step Synthesis of Gold Nanoparticles

Preparation of gold nanoparticles with a narrow size distribution has enormous importance in nanotechnology. Methanobactin (Mb) is a copper-binding small peptide that appears to function as an agent for copper sequestration and uptake in methanotrophs. Mb can also bind and catalytically reduce Au (III) to Au (0). In this study, we demonstrate a facile Mb-mediated one-step synthetic route to prepare monodispersed gold nanoparticles. Continuous reduction of Au (III) by Mb can be achieved by using hydroquinone as the reducing agent. The gold nanoparticles have been characterized by UV-visible spectroscopy. The formation and the surface plasmon resonance properties of the gold nanoparticles are highly dependent on the ratio of Au (III) to Mb in solution. X-ray photoelectron spectroscopy (XPS), fluorescence spectra and Fourier transform-infrared spectroscopy (FT-IR) spectra suggest that Mb molecules catalytically reduce Au (III) to Au (0) with the concomitant production of gold nanoparticles, and then, Mb statically adsorbed onto the surface of gold nanoparticles to form an Mb-gold nanoparticles assembly. This avoids secondary nucleation. The formed gold nanoparticles have been demonstrated to be monodispersed and uniform by transmission electron microscopy (TEM) images. Analysis of these particles shows an average size of 14.9 nm with a standard deviation of 1.1 nm. The gold nanoparticles are extremely stable and can resist aggregation, even after several months.     

Microwave Synthesis and Characterization of Spinel-type Zinc Aluminate Nanoparticles

In the present work, ZnAl₂O₄ nanoparticles have been synthesized with the aid of Zn(OAc)₂·2H₂O and Al(NO₃)₃·9H₂O as starting reagents in the presence of microwave irradiation. Besides, the effect of preparation parameters such as microwave power and irradiation time on the morphology and particle size of products was studied by SEM images. The as-prepared ZnAl₂O₄ nanoparticles were characterized extensively by techniques like XRD, TEM, SEM, FT-IR, PL, and EDS. Photoluminescence studies of the ZnAl₂O₄ nanoparticles displayed quantum confinement behavior with band gap of 3.2 eV. The XRD studies showed that pure orthorhombic ZnAl₂O₄ nanoparticles have been produced after calcination.     

Low-Temperature Synthesis of Zinc Oxide Nanoparticles

Crystalline zinc oxide nanoparticles have been prepared by mixing aqueous solutions of zinc nitrate and hexamethylenetetramine (HMT) at 60°C and 80°C. Transmission electron microscopy and X-ray diffraction show that the ZnO nanoparticles of diameters ranging from 15–33 nm and 25–43 nm long are formed. Aspect ratio is observed to range from 1.18 to 1.74 at 60°C and 1.22 to 1.70 at 80°C as the HMT to zinc nitrate concentration ratio increases from 10 to 150. Nanoparticle size decreases as the concentration of HMT increases. Much larger ZnO particles are formed with ammonium hydroxide as a hydrolysis agent without HMT. In summary, HMT is an ammonium-hydroxide source in the reaction, a surfactant for retaining nanosize, and not necessarily a template for ZnO nucleation.     

Synthesis,Crystal Structure,Spectroscopic and Thermal Analysis of Strontium Pyrophosphate Dihydrate Nanoparticles

Various pyrophosphates are very useful as bioceramics; for instance, strontium pyrophosphate is one of the emerging forms of alkaline phosphate. Strontium pyrophosphate dihydrate (Sr₂P₂O₇2H₂O) nanoparticles were synthesized by the surfactant‐mediated approach and characterized by different techniques. From the powder XRD study, the average crystallite size was evaluated by applying Scherrer's formula, which was found to be 33.57 nm. The average crystallite size and internal strain were also evaluated using Williamson–Hall (W‐H) method. The FT‐IR spectroscopy study confirmed the presence of symmetric and asymmetric stretching vibrations of P–O–P and PO₃. The UV‐NIR absorption spectroscopy over the spectral range of 210–1200 nm was employed, and the energy band gap was calculated from Tauc's plot which was found to be 4.9 eV. Thermogravimetric analysis (TGA) confirmed the presence of two water molecules in the sample. From TGA, it was found that the sample become anhydrous and on heating above 410–800°C, the sample remained almost stable with slight weight gain due to adsorption of purged gas. Various kinetic parameters and thermodynamic parameters were evaluated for dehydration process.     

水热法制备纳米氧化铁的研究

对水热法制备纳米氧化铁以及氧化氢氧化铁进行了研究。通过实验制得了多种不同形貌的纳米氧化铁以及纳米氧化氢氧化铁,利用X射线电子衍射(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)对所得产物进行了表征,研究了反应时间、温度对最终产物形貌、粒径的影响,对产物的变化规律进行了总结。     

金属氧化物纳米颗粒溶胶-凝胶合成概述

文章介绍了金属氧化物纳米颗粒的水溶胶-凝胶合成与非水溶胶-凝胶合成的一般工艺过程和影响合成工艺的主要因素,总结了常见合成反应的类型与简单反应机理.并对作水合成中的表面活性剂控制与溶剂控制两种方法的优缺点进行了比较.     

Synthesis and Characterization of Coralline Magnesium Oxide Nanoparticles

Magnesium oxide (MgO) nanoparticles were prepared using sol–gel process. The nanoparticles were then dried using a supercritical drying process. The particles were characterized for surface morphology, crystal structure, and surface functionality. The nanoparticles show a coralline structure with an average particle size of 200–300 nm with a surface area of 257 m²/g. The X-ray diffraction spectra of these materials are also obtained. The MgO particles, when contacted with a model explosive component 2, 4 dinitrotoluene in water at 50°C, showed a concentration reduction of 96%.     

Mechanochemical Synthesis of Lanthanum Aluminate by Grinding Lanthanum Oxide with Transition Alumina

Grinding lanthanum oxide (La₂O₃) with Al₂O₃ was conducted to investigate their mechanochemical reactions to form lanthanum aluminate (LaAlO₃) powder using a planetary ball mill. Grinding for 120 min allowed us to obtain single-phase LaAlO₃ with a large surface area when transition alumina was used, whereas no formation of LaAlO₃ was achieved when α-Al₂O₃ was used. The mechanochemical process can be applied to synthesize other rare-earth (RE) aluminates (REAlO₃) from mixtures of a rare-earth oxide and transition alumina.     

Characteristics of Strontium Aluminate Crystals Used for Long-Duration Phosphors

Sr₃Al₂O₆, SrAl₂O₄, SrAl₄O₇, and SrAl₁₂O₁₉ that have been doped with Eu²⁺ and Dy³⁺ ions have been grown by a floating-zone technique for application as long-duration phosphors. Long-duration phosphorescence with a variety of colors has been observed in SrA_l2O₄, SrAl₄O₇, and SrAl₁₂O₁₉ crystals that have been doped with Eu²⁺ and Dy³⁺ ions. The peak wavelength of the phosphorescence is 520 nm for SrAl₂O₄, 480 nm for SrAl₄O₇, and 400 nm for SrAl₁₂O₁₉. The phosphorescence is characterized by decay times that have been analyzed by a curve-fitting technique.     

无放射性铝酸盐夜光材料的研究进展

夜光材料是指经过紫外光或可见光等光源的短时间照射后,离开光源,依旧能持续发光很长时间的功能材料。稀土铝酸盐发光材料由于其辉度高、发光时间长、安全无毒等特点受到了广泛关注与应用。本文综述并分析了铝酸盐体系蓄光型自发光材料的制备方法,同时阐述了蓄光型发光材料的应用及其发展前景。     

氧化物添加剂在合成和烧结镁铝尖晶石过程中的作用

在钢铁窑炉以及水泥和石灰回转窑中镁铝尖晶石砖已经成功地替代了镁铬砖。利用软件和热力学基本数据解释添加剂在尖晶石形成过程中所起到的作用。为了使镁基耐火材料形成更好的结合结构,分析了镁铝合金粉末添加二价和四价氧化物添加剂在相对较低的温度下合成和烧结过程中所起的作用。利用X-射线衍射图谱中峰位移动的数据研究了活性阳离子在氧化镁-尖晶石和尖晶石-尖晶石的表面扩散情况。     

F掺杂SnO2纳米粉体的燃烧合成

以金属锡和HF为原料采用燃烧合成法合成得到了F掺杂SnO2纳米颗粒。燃烧反应中甘氨酸为燃料,硝酸为氧化剂。采用XRD,BET,TEM和EDS等分析手段对合成得到的FTO进行了表征。结果显示,F的掺杂促进了SnO2基体晶粒的长大,所得到的粉体团聚较少,呈单分散状态。     

Solution Combustion Synthesis of Complex Oxide Semiconductors

This is a perspective of the role that combustion synthesis, specifically solution combustion synthesis, has played in the development of ternary and quaternary metal oxide semiconductors, and materials derived from these compounds such as composites, solid solutions, and doped samples. The attributes of materials, collectively termed ‘complex oxides’ within the context of this discussion, are discussed in terms of their applicability in the generation of solar fuels from water splitting and CO₂ reduction, and environmental pollution remediation via heterogeneous photocatalysis.     

Synthesis of Lithium-Cobalt Oxide Nanoparticles by Flame Spray Pyrolysis

Crystalline LiCoO2nanoparticles were synthesized from an aqueous solution of acetate compounds of lithium and cobalt by a flame spray pyrolysis, and characterized by TEM, XRD, and BET method. We investigated the evolution of LiCoO2nanoparticles from liquid droplets sprayed along the flame and observed disintegration of aqueous precursor droplets about 10μm into smaller fragments around 50 nm in the high temperature flame, as well as decomposition/oxidation of the precursor and coalescence/coagulation. We also examined effects of process variables such as molar concentrations of the precursors and flow rates of combustible gases on the particle size and crystal structure. The average particle diameter increased with an increase in the molar concentration of the precursor. Raising the maximum flame temperature by controlling the gas flow rates also led to an increase in the average diameter of the particles. The crystalline nanoparticles synthesized were nearly spherical, and their average primary particle diameters ranged from 11 to 35 nm.     

Nonaqueous and Surfactant-Free Synthesis Routes to Metal Oxide Nanoparticles

Nonaqueous sol–gel routes to metal oxide nanoparticles have become a promising alternative to aqueous methods, allowing the controlled synthesis of a variety of metal oxides as highly crystalline products at comparably low temperatures. The use of solvents like benzyl alcohol that also function as surface modifiers makes the addition of surfactants superfluous, resulting in improved product purity. In addition to a short overview of such nonaqueous routes to binary and ternary metal oxides, the facile synthesis of sodium and potassium niobates as well as of sodium tantalate and barium stannate nanoparticles via straightforward, surfactant-free pathways is reported.     

一步法合成二苯甲酰基甲烷(DBM)

以二甲苯为溶剂 ,甲醇钠为催化剂 ,一定比例的苯乙酮和苯甲酸甲酯在 1 35～ 1 4 0℃下缩合 ,反应 4～6h。然后经 30 %硫酸酸洗、1 0 %Na2 CO3 溶液碱洗、水洗等后处理操作 ,一步合成了产物二苯甲酰基甲烷。收率 >87% ,纯度 >99% (GC) ,熔点为 77～ 78℃。得到了优化的工艺条件 :n(苯乙酮 )∶n(苯甲酸甲酯 )∶n(甲醇钠 )∶n(二甲苯 ) =1∶4∶1 6∶1 0 ;反应保温时间为 5h。     

Synthesis and Characterization of Luminescent Yttrium Oxide Doped with Tm and Yb

Combustion synthesis was used to obtain nanocrystalline Y_{(2− x − y )}Tm _x Yb _y O₃ blue-emitting phosphors. From X-ray diffraction (XRD) it was determined that the powders in the as-synthesized state were in a state of high strain. Upon thermal treatment, the strain in the lattice decreased, which resulted in an improvement in the photoluminescence emission intensity of these phosphors. Fourier-transform infrared spectrometry analysis showed that there is a negligible difference in the absorbed impurities with heat-treatment temperature and time. Hence, it was concluded that the surface impurities do not play a role in the increase in luminescence intensity of these phosphors. The optimum activator concentrations were determined to be approximately x =0.02 and y =0.01.     

Magnetic Iron Oxide Nanoparticles: Synthesis and Surface Functionalization Strategies

Surface functionalized magnetic iron oxide nanoparticles (NPs) are a kind of novel functional materials, which have been widely used in the biotechnology and catalysis. This review focuses on the recent development and various strategies in preparation, structure, and magnetic properties of naked and surface functionalized iron oxide NPs and their corresponding application briefly. In order to implement the practical application, the particles must have combined properties of high magnetic saturation, stability, biocompatibility, and interactive functions at the surface. Moreover, the surface of iron oxide NPs could be modified by organic materials or inorganic materials, such as polymers, biomolecules, silica, metals, etc. The problems and major challenges, along with the directions for the synthesis and surface functionalization of iron oxide NPs, are considered. Finally, some future trends and prospective in these research areas are also discussed.     

铝酸锌类陶瓷发光粉的初步研究

以ZnAc2和Al（NO3）3为原料,掺杂Eu（NO3）3和Dy（NO3）3后,采用燃烧法制备ZnAl2O4：Eu荧光粉。本文探讨在固定基质组成的条件下,加入了不同量的稀土,在不同反应温度下和反应时间内对荧光粉发光的影响。结果发现,当稀土加入量Eu2＋/Al3＋=1/25,Dy3＋/Al3＋=0,反应温度700℃,反应时间30 min.时制得的荧光粉发光效果最好。     

Sol-Gel Synthesis of Lithium Aluminate

LiAlO₂ was prepared by two sol-gel methods using simultaneous hydrolysis of the reagents: aluminum sec -butoxide/ lithium methoxide and aluminum sec -butoxide/LiOH. The resulting ceramic powders were compared with those prepared by two conventional methods (i.e., solid-state fusion and peroxide). The sol-gel method provided powders with a very high γ-LiAlO₂ content after calcining at temperatures as low as 700°C when LiOH was used. The solids were characterized by AAS, DTA, TGA, XRD, and SEM.