Preparation of cobalt oxide nanoparticles and cobalt powders by solvothermal process and their characterization

Co₃O₄ nanoparticles and cobalt (fcc-Co) powders were successfully synthesized by solvothermal process from a single precursor. The reaction of Co(Ac)₂ with sodium dodecylbenzenesulfonate (SDBS) shows evident-dependent temperature effect. At 180 °C, Co(Ac)₂ reacts with SDBS to produce precursor CoCO₃ plate structures, which are assembled by small nanoparticles. At the temperature of 250 °C, the precursor CoCO₃ can be gradually decomposed to form Co₃O₄ nanoparticles with diameter of ca. 70 nm. While, at 250 °C, the reaction of Co(Ac)₂ with SDBS also produce precursor CoCO₃ nanoparticles/plates, but the CoCO₃ nanoparticles/plates would only decompose to give metal Co. In this process, SDBS acts as not only a surfactant but also a reagent. Magnetic measurements reveal that the as-prepared Co₃O₄ nanoparticles exhibit weak ferromagnetic properties and Co powders show ferromagnetic properties. In addition, a possible formation mechanism was elaborately discussed.     

Novel mechanochemical process for synthesis of magnetite nanoparticles using coprecipitation method

A novel coprecipitation method using a high mechanical energy field as the synthesis reaction system of magnetite (Fe₃O₄) has been developed for preparing the superparamagnetic Fe₃O₄ nanoparticles with high crystallinity in water system. In the synthesis process, the suspension containing the precipitates of ferrous hydroxide and goethite was treated in a tumbling ball mill under a cooling condition. The mechanical energy generated by collision of ball media promoted the Fe₃O₄ formation reaction and simultaneously crystallized the formed Fe₃O₄ nanoparticles without using any conventional heating techniques by means of the mechanochemical effect. The collision energy of ball media was numerically analyzed by discrete element simulation of their motion in the ball mill. Size, crystallinity and magnetization of the Fe₃O₄ nanoparticles obtained under different ball-milling conditions were almost the same regardless of the amount of the collision energy. However, the reaction rate of Fe₃O₄ formation increased with the collision energy, which was analogous to increase of the reaction rate caused by increase of the heat energy applied to the reaction system. The reaction rate depended strongly on the number of collisions with the energy larger than a threshold value corresponding to the activation energy in this reaction system.     

Preparation and characterization of ATO nanoparticles by various coprecipitation

A series of Sb doped SnO₂ (ATO) nanoparticles, with Sb doping levels 0–20 at.% has been prepared by two different coprecipitation routes. Effect of preparation process, Sb doping concentration and calcination temperature on the crystallinity and morphology of ATO nanoparticles were investigated and analyzed. The prepared nanoparticles were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, selective area electron diffraction, X-ray diffraction and energy dispersive X-ray spectroscopy. Results indicated that the prepared ATO nanoparticles were tetragonal, and isostructural with rutile lattice structure as known from bulk SnO₂. The ATO nanoparticles prepared via process I (homogeneous coprecipitation) presented obviously weaker crystallinity, smaller average crystallite size and harder agglomeration than that prepared via process II (heterogeneous coprecipitation). The crystallinity and average crystallite size of ATO nanoparticles prepared via process II increased with increasing calcination temperatures and reducing Sb doping concentrations, respectively. The increased crystallinity, dispersibility and average crystallite size for ATO nanoparticles prepared via process II may be due to the formation of ATO crystal nuclei, leading to an improved formation dynamics of ATO nanoparticles.     

仿生法合成纳米氧化锌及性能表征

采用了一种全新的表面活性剂——酵母。以硝酸锌为原料，氨水和尿素为沉淀剂，运用仿生法与均匀沉淀法相结合制取纳米氧化锌，并利用多种测试手段进行性能表征。试验结果表明，制得的氧化锌颗粒较小，加入酵母后，氧化锌的性能有了显著提高，烧结温度在300和600℃时的氧化锌具有很好的光催化性。     

微波加热制备尺寸各向异性纳米金属钌颗粒

采用微波加热Polyol法以PVP作为稳定剂,首先快速合成了晶粒尺寸为2～6nm具有不同长宽比的各向异性的单分散金属钌胶体颗粒.以单分散胶体颗粒为晶种,获得不同团聚程度的纳米金属钌颗粒.高分辨电子显微镜(HRTEM)研究表明,树枝状纳米金属钌是由随机取向的金属钌单晶颗粒组成的.     

Formation of zinc oxide nanoparticles by mechanochemical reaction

Abstract

The synthesis of zinc oxide (ZnO) nanocrystallites by mechanochemical reaction of ZnCl₂ and Na₂CO₃ with NaCl as diluent and following thermal treatment was investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Calcination of the as milled powder at 600°C in air and removal of NaCl through washing formed ZnO nanocrystallites with an average crystal size of ~ 21 nm, which increased with increasing thermal treatment temperature. Milling time and NaCl/ZnCl₂ molar ratio exerted prominent effects on the crystal size of the ZnO nanoparticles. The mechanism of nanocrystallite growth is discussed.     

Preparation and characterization of honokiol nanoparticles

In this paper, honokiol nanoparticles were prepared by emulsion solvent evaporation method. The prepared honokiol nanoparticles were characterized by particle size distribution, morphology, zeta potential and crystallography. Results showed that the obtained honokiol nanoparticles at size of 33 nm might be amorphous, and could be well dispersed in water. Due to the great dispersibility in water, the obtained honokiol nanoparticles might have great potential in medical field.     

Preparation and characterization of pyrazoline nanoparticles

Nanoparticles of 1-phenyl-3-naphthyl-5-((dimethylamino)phenyl)-2-pyrazoline ranging from tens to hundreds of nanometers were prepared by the reprecipitation method. Their excitonic transitions responsible for absorption and emission, as compared with those of dilute solution, have been investigated as a function of nanoparticle size. We found that pyrazoline nanoparticles possess a special size dependence on their optical properties. As the nanoparticle size decreased, the molecular absorption peak of pyrazoline nanoparticles was observed to shift to the high-energy side due to size effect.     

纳米碲粉体的制备及表征

利用惰性气体保护蒸发-冷凝法制备了碲（Te）纳米粉体颗粒。通过热力学计算得到碲的蒸汽压随温度的变化关系。利用X射线衍射（XRD）、透射电子显微镜（TEM）、激光粒度仪观测了碲纳米颗粒的晶体结构、形貌,并研究了粉末粒径、分布及形貌与蒸发冷凝过程中气氛压力的关系。结果表明,随着气氛压力的增加,粉末粒径分布范围变窄,粉末粒度...     

The use of de-aggregating agents in ZnSe mechanochemical synthesis

Conventional mechanochemical synthesis of zinc selenide, ZnSe nanoparticles was performed in a planetary ball mill by high-energy milling of zinc (Zn) and selenium (Se) powders with the de-aggregating agents ZnCl₂ and phthalic acid (aromatic dicarboxylic acid, C₈H₆O₄). Physical–chemical and optical properties of the prepared ZnSe nanoparticles were studied and compared. The mechanochemically synthesized products were characterized by X-ray diffraction analysis (XRD) that confirmed the presence of cubic-Stilleite and hexagonal ZnSe phases after 18, 25, 30, 40, 45 and 50 min of milling with various amounts of the added de-aggregating agents. Size of crystallites calculated from XRD patterns was from 20 to 31 nm for cubic ZnSe prepared with ZnCl₂. For ZnSe synthesized with phthalic acid the crystallite size ranged from 16 to 73 nm. Size, phase composition, morphology, and crystallinity of ZnSe nanoparticles were studied by transmission electron microscopy (TEM) and selected area electron diffraction (SAED). Photoluminescence spectra (PL) at room temperature have shown a broad red emission bands, and the presence of de-aggregating agent has altered the intensity of the PL signal as well.     

Preparation of multicomponent oxides by mechanochemical methods

A large variety of synthesis strategies and processing techniques are currently being used to obtain new multicomponent oxides and/or modify existing ones. Among them, mechanochemical processing has become very popular because it is simple to implement, solvent free, and capable of providing enough volume of the target material in an economically viable manner. The preparation of complex oxides can benefit from mechanochemical methods for two important reasons: First, it is not a diffusion-controlled process and thus, high-rate solid state reactions can be promoted between oxides with different physical and chemical properties without using high temperatures; secondly, because reactants are processed under non-equilibrium conditions, uncommon metastable phases are frequently obtained featuring flexible crystal structures, small particle size, high concentration of defects, and off-stoichiometry. Furthermore, conversion to the “true” equilibrium phases induced by additional processing (e.g., firing) offers the possibility of isolating fairly stable intermediate states with unusual and desirable properties that are inaccessible for more conventional processing techniques. As oxide particles are hard and brittle, the number of oxide systems prepared by means of mechanochemical methods grew rapidly only in recent years when more powerful milling devices and abrasion-resistant milling tools became available. This article summarizes recent work carried out in the field; only dry milling of oxides (and occasionally carbonates) in the absence of additives is considered. Some of the main challenges of mechanochemical processing are also highlighted and discussed.     

Preparation and characterization of dendritic silver nanoparticles

Dendritic silver nanoparticles have been prepared by a soft solution technique from the aqueous solution of silver nitrate and poly (vinyl pyrrolidone) (PVP) in the presence of ethanol used as a reducing agent. The resultant silver nanoparticles were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive analyses of X-ray (EDX), and UV-Visible absorption spectroscopy. It was found that the well-defined dendritic silver nanoparticles which had the length 0.5–1 m and the width of 100–200 nm.     

Preparation and characterization of cuprous iodide nanoparticles

A new technique for the preparation of CuI nanoparticles from CuSO₄ and KI ethanol solutions has been developed. Preparation conditions were optimized through a series of experiments. Under these conditions, the yield of CuI reached 95.39%. The product was characterized and the reaction kinetics was studied. The results show that the product takes a roughly spherical shape with an average particle size of less then 50 nm. The activation energy of the formation of CuI is found to be E _a = 0.58 × 10² kJ/mol, and the preexponential factor in the Arrhenius equation is k ₀ = 7.43 × 10¹⁶ mol/(l s). The text was submitted by the authors in English.     

Preparation of iron oxide nanoparticles by microwave synthesis and their characterization

In this study production of fine particle Fe2O3 via microwave processing of Fe(NO3)3.nH2O followed by low temperature annealing was reported. XRD was used to characterize the structural properties of nanoparticles. Approximate particle sizes were between 3-13 nm according to Scherrer's equation. Single point BET measurement results also show that samples have large surface area and they are nanometer sized particles. TEM study was conducted to examine the structure of the nanoparticles. TEM figure is in good agreement with the results obtained from Scherrer's equation using XRD spectra. In order to characterize the magnetic properties of the nanoparticles VSM (Vibrating Sample Magnetometer) was used. From these results it can be concluded that the sample containing only maghemite phase exhibits superparamagnetic behaviour, on the other hand sample containing both hematite and maghemite phases shows paramagnetic behaviour above 300 K, superparamagnetic behavior at lower temperatures.     

Preparation and characterization of iron nanoparticles protected by an oxide film

Iron nanopowders ranging in particle size from 20 to 100 nm have been synthesized by reducing a 1-mm-thick iron(III) hydroxide layer in flowing hydrogen at 400°C and then passivated for 6–60 min in flowing argon containing 3% air. Our results demonstrate that the passivated iron nanopowders do not oxidize in air for six months. The iron nanoparticles have been characterized by X-ray diffraction (crystallite size evaluation), Auger electron spectroscopy, and polymolecular adsorption. The passivated iron nanoparticles have been shown to consist of a metallic core and oxide shell 2–4 nm in thickness.     

Preparation and characterization of silica-coated ZnSe nanowires with thermal stability and photoluminescence

Silica-coated ZnSe nanowires with well-controlled the thickness of sheath in the range of 10-60 nm have been synthesized through a simple sol-gel process. The thickness of silica coating could be controlled through altering reaction parameters such as volume ratio of TEOS and ammonia. XRD, high-resolution TEM, X-ray photoelectron spectroscopy (XPS), Raman spectra, thermogravimetric analysis (TGA), and photoluminescence (PL) spectra were used to characterize the core/sheath nanostructures. Room-temperature PL measurements indicate these silica-coated ZnSe nanowires remarkably improve the PL intensity. Meanwhile, the thermal stability has been enhanced greatly, which is useful for their potential applications in advanced semiconductor devices.     

Preparation and characterization of camptothecin solid lipid nanoparticles

Camptothecin (CA), an antitumor drug, was incorporated into solid lipid nanoparticles (SLNs) prepared by high-pressure homogenization. A Taguchi orthogonal experimental design was used to study the influence of four different variables, with each variable having three value levels on nanoparticle size. Analysis of variance (ANOVA) has been used to evaluate the preparation of CA-SLNs and perform product optimization. The optimized CA-SLNs suspension was lyophilized using mannitol and glucose as cryoprotectants. The physicochemical characteristics of CA-SLNs were evaluated using transmission electron microscopy (TEM), electrophoresis, and differential scanning calorimetry (DSC). The release of camptothecin from CA-SLNs in various media was evaluated using a high-performance liquid chromatography (HPLC) method. The results showed that the concentration of emulsifier and the homogenization pressure had a significant influence on the particle size. The optimized CA-SLNs had an average diameter of about 200 nm, exhibited monodispersity with Dw/Dn of 1.06, and carried a negative charge. The optimal cryoprotectants consisted of 10% mannitol and 5% glucose in nanoparticle suspension. Lyophilized product was reconstituted in distilled water within 0.5 min without change of nanoparticle size. Camptothecin might exist in an amorphous state in SLNs. In vitro results showed that drug release was achieved for up to one week, and the released camptothecin quickly changed to open carboxylate form in the biological pH phosphate buffer. The results indicate that SLNs might be good potential sustained-release delivery vehicles for camptothecin or other lipophilic drugs.     

亲油性LaF3纳米粒子的制备及表征

在醇-水混合溶剂中合成了表面为油酸修饰的LaF3纳米粒子,并用透射电子显微镜、红外光谱和X射线粉末衍射仪对修饰LaF3纳米粒子进行了表征.结果表明:所制备的修饰LaF3纳米粒子大小均匀,粒径约为8nm;其纳米核为六方结构的LaF3;由于表面修饰剂油酸与LaF3纳米粒子表面之间发生化学键合作用,使得油酸修饰LaF3纳米粒子在苯及润滑油中的分散性明显提高.