Synthesis of ZnO nanoparticles through the impregnated layer combustion synthesis process

Zinc oxide nanopowders were synthesized by a solution combustion technique named impregnated layer combustion synthesis (ILCS), involving the impregnation of an active layer with the reactant solution and subsequently the combustion of the impregnated system. In this work three different organic fuels and two different ignition modes were tested in order to optimize the final microstructure and specific surface area (SSA) of the ZnO nanopowders. In particular, the ignition mode was found to significantly affect the final products, discriminating between an explosion procedure (flame combustion) and a self-propagating mode (smoldering combustion). The nitrate–glycine mixture and the smoldering combustion way were found to be the most suitable conditions, giving rise to softly agglomerated nanopowders with an average size of 20 nm and a very high SSA, without the need of any further crystallization treatment.     

Size-controllable synthesis of catalyst of gold nanoparticles with capping agents of natural chitosan

In this study, size-controllable gold nanoparticles (NPs) are synthesized by using sonoelectrochemical methods in the presence of natural chitosan (Ch). First, positively charged Au-containing complexes were prepared in 0.1 N NaCl by using oxidation–reduction cycle (ORC) treatment to Au substrate. Then size-controllable Au NPs, ranging from 10 to 80 nm in diameter, were synthesized by varying the addition quantities of Ch from 1 to 2 g/L, respectively, in solutions under using sonoelectrochemical reduction. Experimental results indicate that the optimal molar ratio of used Ch to synthesized Au NPs is ca. 3 for obtaining the smallest Au NPs. Moreover, the catalytic activity of the size-controllable Au NPs on the decomposition of acetaldehyde in solution was examined. Au NPs with 10 nm in diameter demonstrate significantly catalytic activity. However, bigger Au NPs with 80 nm in diameter are almost inert for the decomposition of acetaldehyde.     

Structure control synthesis of iron oxide polymorph nanoparticles through an epoxide precipitation route

Iron oxide polymorph nanoparticles (magnetite, goethite and lepidocrocite) were synthesised through a novel epoxide precipitation route. Epoxide, as a precipitating agent, induced the precipitation of iron(II) ions in the form of hydroxide through its reaction with aquocomplexes of Fe²⁺ ions. The organic intermediate, which was produced from the ring-opening reaction of epoxide, functionalised the surface of the formed precipitate in situ, resulting in the minimisation of the nanoparticles’ aggregation. Another advantage of this route is its simple procedure for the preparation of iron oxide nanoparticles with different structures and their well-defined morphology. Magnetite, goethite and lepidocrocite nanoparticles were obtained just by the pH regulation and air oxidation at room temperature.     

Metal nanoparticles generated by laser ablation

We study a new method for producing ultrafine metal particles (nanopartides) that employs Laser Ablation of Microparticles (LAM). Pulsed excimer laser radiation at 248 nm wavelength was used to ablate ~2 μm feedstock of silver, gold, andpermalloy (Ni₈₁%:Fe_19%) under both normal atmospheric conditions and in other gases and pressures. A model for nanoparticle formation by LAM is proposed that includes plasma breakdown and shock-wave propagation through the initial microparticle. Behind the shock a large fraction of the original microparticle mass is converted to nanoparticles that diffuse to silicon substrates and TEM grids for collection and analysis. Nanoparticle morphologies are spherical except for gold nanoparticles >100 nm that are generally cubes. Electron micrographs of the samples were analyzed by computer-aided image processing to determine the effect of irradiation conditions on the nanoparticle size distribution. The results showed that mean particle diameters were normally in the range from 10 to 100 nm and that the particle size distributions were generally log-normal, with dispersion (diameter/standard deviation) ranging from 0.2 to 0.5. For metallic microparticle feedstock, the mean size of the produced nanoparticles generally increased with increasing laser fluence and were smallest for fluences not too far above the breakdown threshold.     

Mechanochemical synthesis of nanoparticles

The results of recent investigation of the mechanochemical synthesis of inorganic nanoparticles are reviewed. It was demonstrated that, by selecting suitable chemical reaction paths, stoichiometry of starting materials and milling conditions, mechanochemical processing can be used to synthesise a wide range of nanocrystalline particles dispersed within a soluble salt matrix. Selective removal of the matrix phase by washing the resulting powder with appropriate solvents can yield nanoparticles of the desired phase. This technique has been shown to have advantages over other methods of producing nanoparticles in terms of low cost, small particle sizes, low agglomeration, narrow size distributions and uniformity of crystal structure and morphology.     

High-pressure synthesis of diamond from phenolic resin

Two kinds of phenolic resin, novolak and resols, have been studied with an addition of cobalt at pressures between 2 and 4 GPa and at temperatures from 1300 to 1900 °C, all under thermodynamically graphite-stable conditions. Diamond was synthesized from these resins which had been pre-fired at 500–1000 °C. From such resins, carbon precursors carrying a great number of radicals, being nearly free of hydrogen and oxygen, and turbostratic in structure, can be constructed. The pressure–temperature conditions suitable for the diamond synthesis were dependent on the pre-firing temperatures. The cobalt served as a catalyst–solvent, similar to the case of conventional diamond synthesis from graphite under diamond-stable conditions. Well-defined single crystals cubo-octahedral in shape, measuring 0.3–0.7 mm across and classified as type Ib were obtained. This revised version was published online in November 2006 with corrections to the Cover Date.     

Enhanced formation of ruthenium oxide nanoparticles through green synthesis for highly efficient supercapacitor applications

Ruthenium oxide nanoparticles (RuO₂ NPs) are one of the most promising materials at nanoscale, for energy storage devices. In the present work, a bottom up approach was utilized to synthesize RuO₂ NPs using biological resources, as reducing agent. Root extract of traditionally important medicinal plant, Akarkara (Anacyclus pyrethrum), was used in this study as the reducing agent. The investigation was carried out without the addition of any external reaction catalyzing agent. The Characterization studies were performed to analyze the conformational nature of the nanoparticles through XRD, SEM, TEM with SAED and FTIR spectroscopy was done to assess the functional moieties. Cyclic voltammetric (CV) studies were carried out to investigate the electrochemical potential of the synthesized RuO₂ NPs using the extract. The results demonstrated that the biologically reduced nanoparticles were crystalline, spherical and with an average size of 13 nm. The RuO₂ NPs were observed to be highly stable even after repeated usage. CV analysis revealed that capacitance behavior was reversible in nature and the specific capacitance of RuO₂ NPs using Akarkara (Anacyclus pyrethrum) coated over carbon sheet was 209 Fg⁻¹ at a scan rate of 5 mV/s. These results proved that green biosynthesis of RuO₂ can be used for supercapacitor applications.     

Polysaccharides and phytochemicals: a natural reservoir for the green synthesis of gold and silver nanoparticles

Currently, sustainability initiatives that use green chemistry to improve and/or protect our global environment are becoming focal issues in many fields of research. Instead of using toxic chemicals for the reduction and stabilisation of metallic nanoparticles, the use of various biological entities has received considerable attention in the field of nanobiotechnology. Among the many possible natural products, polysaccharides and biologically active plant products represent excellent scaffolds for this purpose. Polysaccharides have hydroxyl groups, a hemiacetal reducing end, and other functionalities that can play important roles in both the reduction and the stabilisation of metallic nanoparticles. Among the various categories of compounds in plants that have potent biological activities, phytochemicals are emerging as an important natural resource for the synthesis of metallic nanoparticles. The focus of this review is the application of polysaccharides and phytochemicals in the green synthesis of gold and silver nanoparticles to afford biocomposites with novel uses in nanomedicine and as nanocomposites.     

Metal oxide nanoparticles for advanced energy applications

Hot-wire chemical vapor deposition (HWCVD) has been employed as an economically scalable method for the deposition of crystalline molybdenum oxide nanoparticles at high density. Under optimal synthesis conditions, only crystalline nanostructures with a smallest dimension of ~ 3-50 nm are observed with extensive transmission electron microscopy analyses. The incorporation of crystalline molybdenum oxide nanoparticles into battery electrodes has led to profound advancements in state-of-the-art negative electrodes (anodes) in lithium-ion batteries. The nanoparticle materials exhibit a high rate capability as anticipated for the reduced solid-state Li-ion diffusion length.     

Microwave-assisted synthesis of nickel nanoparticles

Nickel nanoparticles with uniform, monomorphic self-assembled flower-like microstructure were synthesized by reduction of nickel chloride with hydrazine hydrate in the presence of polyvinylpyrrolidone (PVP) in ethylene glycol under microwave irradiation. An appropriate amount of Na₂CO₃ was necessary for the formation of monomorphic and uniform Ni nanoflowers. Small amount of NaOH and a higher concentration of hydrazine were beneficial to the formation of Ni nanoflowers with a smaller diameter and a narrower distribution. The transmission electron microscopy (TEM) and X-ray diffraction measurements manifested that the as-synthesized Ni nanoflower was the assembles self-organized by hundreds of smaller primary nanoparticles with an average dimension of about 6.3 nm.     

Microfluidic synthesis of Fe nanoparticles

A microfluidic reactor process is demonstrated for the synthesis of worm-like Fe nanoparticles (NPs) at room temperature. These high aspect ratio shaped Fe NPs can be further transformed into large ellipsoid species with refined crystal structures and increased aggregation by way of a sonication process, evidenced by their transmission electron microscope (TEM) images, selected area electron diffraction (SAED), X-ray Diffraction (XRD), X-ray absorption near K-edge structure (XANES) and extended X-ray absorption fine-structure (EXAFS). Due to the compensation effects on the magnetic properties of NPs from their increased size, enhanced magnetic coupling, refined crystal structure and the reduced aspect ratio, the sonication-treated Fe NPs show a slightly enlarged coercivity (Hc), an enhanced saturation magnetization (Ms) and a slight suppress in the increased blocking temperature (Tb).     

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。     

Hot-wire synthesis of Si nanoparticles

The viability of producing silicon nanoparticles using the HWCVD process is investigated. A system is assembled and particles are produced from silane at pressures between 0.2 and 48 mbar, with hydrogen dilutions of 0-80%, at a total flow rate of 50 sccm and with a tungsten filament maintained at 1650 °C. The as-prepared powder varies in colour from yellowish to dark brown and is deposited on all surfaces inside the reaction chamber. The material is a highly porous agglomeration of nanoparticles of primary size in the order of 40 nm, with a narrow size distribution. The nanoparticles produced are mostly amorphous, hydrogenated and have a partially oxidised surface.     

Microwave-assisted synthesis of ceria nanoparticles

Nanocrystalline ceria (CeO₂) particles have been successfully prepared by microwave-assisted heating technique from an aqueous solution containing ammonium Ce(IV) nitrate and sodium hydroxide. Further thermal treatment of the as-prepared powder at 500 °C resulted in the formation of the well-crystallized CeO₂ nanoparticles with an average crystal size of about 8 nm, varying with the heating temperature. The as-prepared powder and the CeO₂ nanoparticles were examined using X-ray diffraction (XRD) and transmission electron microscope (TEM) techniques. It was found that the morphologies of the synthesized powder show from rod-like for the as-prepared sample to sphere-like for the heat-treated nanoparticles. Mechanism of CeO₂ nanocrystallite growth during annealing is primarily investigated.     

Tailor-made nanoparticles via gas-phase synthesis

Gas-phase synthesis is a well-known chemical manufacturing technique for an extensive variety of nanoscale particles. Since the potential of ultrafine and, in particular, nanoscale particles in high-performance applications has been identified, scientific and commercial interest has increased immensely, thus identifying this field as a most important technology of the future. However, nanomaterials can perform their multifunctional tasks only if they are customized in terms of chemical composition, size, and morphology to suit the application at hand. Profound knowledge of the synthesis and precise process control is crucial in meeting the stringent specifications. Although the gas-phase synthesis of ultrafine materials has been known and commercially exploited for decades, existing knowledge is based almost exclusively on empirical know-how. Process simulation is a very suitable tool for expanding the understanding of the synthesis-relevant processes, particle formation mechanisms, and operating parameters. Based on the resulting expertise some special nanoscale gas-phase products of high innovative potential have been developed.     

One-step synthesis and characterization of anisotropic silver nanoparticles: application for enhanced antibacterial activity of natural fabric

A simple one-step chemical reduction method was employed for the synthesis of truncated triangular silver nanoparticles (Ag-NPs). The reduction of Ag ions by sodium borohydride was performed in the presence of poly(vinyl pyrrolidone) as a stabilizing agent. The synthesized Ag-NPs were characterized by UV–Vis spectroscopy, transmission electron microscopy, dynamic light scattering, FT-Raman spectrometer and X-ray diffraction in order to study optical, morphological, compositional, and structural properties. The UV–Vis spectrum showed three plasmon peaks located at 340, 412, and 700 nm, confirmed the anisotropic Ag-NPs. The average edge length of 22 ± 5 nm was observed from TEM images for truncated triangular Ag-NPs. From XRD pattern it was confirmed that the Ag-NPs were polycrystalline in nature, with preferential orientation along (111) lattice plane. The antibacterial susceptibility of Ag-NPs-treated fabrics were tested by Kirby–Bauer disk-diffusion test and American Association of Textile Chemists and Colorists (AATCC) test method 100-2004 against Gram-positive and Gram-negative bacteria. The Ag-NPs treated fabrics showed more pronounced antibacterial activity against Gram-negative bacteria than that of Gram-positive bacteria.     

Analysis of growth parameters for hydrothermal synthesis of ZnO nanoparticles through a statistical experimental design method

Nanocrystalline ZnO particles were synthesized from an aqueous solution composed of zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O) and urea (H₂NCONH₂). A precipitating precursor, basic zinc carbonate (Zn₅(CO₃)₂(OH)₆), was first formed by hydrothermally treating the solution at 120 °C for 2–4 h. Nanocrystalline ZnO particles were then obtained by calcining the precursors at 350–650 °C for 0.5–2 h. The synthesis products were characterized using thermogravimetry–differential scanning calorimetry–mass spectrometry, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and photoluminescence techniques. Based on the experimental results, a possible reaction mechanism for the ZnO formation was proposed. The effects of experimental parameters (namely, the hydrothermal treatment time, the calcination time, and the calcination temperature) on the characteristics of the resulting ZnO products (i.e., the crystalline size and the photoluminescence properties) were analyzed by the Taguchi method to attain the optimum synthesis conditions. By using the appropriate parameters derived from this method, we verified that the optimized synthesis provided a yield of ~70% and that the resulting ZnO particles possessed the characteristics of a ~25 nm crystalline size and a satisfactory photoluminescence property.     

Metal nanoparticles incorporation during the photopolymerization of polypyrrole

In this work we present a route to prepare intrinsically conducting polymer (ICPs)/Silver nanoparticles composite through the photon polymerization process. The method consists to use the transition metals ions assisted by UV light to polymerize the pyrrole monomer. At the same time that the monomer is polymerized the silver ions are reduced and the silver metal particle are produced and incorporated to the polymer matrix. The composite films were characterized by conductivity measurements, UV/vis and FTIR spectroscopy, X-ray diffraction, and scanning electronic microscopy. The morphological properties of incorporated silver nanoparticles were examined with respect to the nature of substrates, exposure time and monomer ratios. Soon after a silver nitrate solution containing Pyrrol is excited by an UV light, a black deposition appears on glass walls or other substrates, such PET (poly(ethylene terephthalate) immersed in the solution, however if the solution is set aside and protected from light, the same black films takes more than 48 h to form. The UV–visible absorption, X-ray diffraction, infrared analysis and conductivity measurements confirm the formation of silver particles and pyrrole polymerization with composite conductivity in the order of 10⁻³ S cm⁻¹.     

新型含联苯结构环氧树脂的合成与性能

合成了一种新型含联苯结构的环氧树脂,并以DDS为固化荆,比较了它与双酚A环氧树脂,邻甲酚醛环氧树脂的耐热性及耐湿性.结果表明,含联苯结构的环氧树脂具有更好的耐热性,同时在耐湿性方面也有很大改进,有利于应用在电子封装材料领域.     

环氧化酚醛耐温胶粘剂的合成及性能研究

通过在酚醛树脂的分子中引入环氧基团合成了一种环氧化酚醛胶粘剂。通过实验得出了制备热塑性酚醛树脂及环氧化反应的最佳条件,对产物的性能进行了测定,用红外吸收光谱对其分子结构进行了表征。结果表明,该胶粘剂剪切强度可达28.8MPa,凝胶时间为82s,产物可在250℃高温下长期使用;合成工艺简单,有望用于工业化生产。