Sonochemical synthesis and characterization of zinc tungstate nanoparticles and investigation of its photocatalyst application

Zinc tungstate nanoparticles were synthesized via a sonochemical method based on the reaction between zinc (II) nitrate hexahydrate and sodium tungstate dihydrate in water. The structural, morphological and optical properties of as-obtained products were characterized by techniques such as X-ray diffraction, scanning electron microscopy, energy dispersive X-ray microanalysis, and ultraviolet–visible spectroscopy. The samples indicated a ferromagnetic behavior, as evidenced by using vibrating sample magnetometer at room temperature. To evaluate the catalytic properties of nanocrystalline zinc tungstate, the photocatalytic degradation of methyl orange under ultraviolet light irradiation was carried out.     

Large-scale synthesis of single crystal silver nanowires by a sodium diphenylamine sulfonate reduction process

Silver nanowires with high aspect ratios of up to more than 60 were synthesized on a large scale by the redox reaction between silver nitrate and sodium diphenylamine sulfonate at room temperature and in the absence of surfactant and hard-template and seed. When the molar ratio of reductant sodium diphenylamine sulfonate and silver nitrate < or =1, most products were all the nanowires. When the molar ratio increases to 2:1, silver nanowires and nanobelts were concomitantly formed. The redox product N, N'-diphenylbenzidinedisulfonate and sodium diphenylamine sulfonate all play an important role in the formation of silver nanostructures. The structure, morphology, and composition of the silver nanowires were characterized by the X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray energy dispersive microanalysis (EDX), and UV-Vis spectroscopy respectively. High-resolution transmission microscopy (HRTEM) and selected area electron diffraction (SAED) reveal the single-crystal nature of the silver nanowires.     

Ag/AgCl纳米枝状结构的制备及其光催化性能研究

采用离子液体法,以离子液体(DESs)为溶剂,柠檬酸三钠为还原剂,氯金酸为晶种,硝酸银为银源,制备了Ag/AgCl纳米枝状结构。利用SEM、XRD、EDS对样品的形貌、成分、结构进行了表征分析,并测试了样品的光催化性能。结果表明,当反应温度为160℃,反应时间为24h时,可获得完整的Ag/AgCl纳米枝状结构;枝状结构的形成是基于AgCl在还原剂作用下不断向Ag转换过程的结果;产物具有较好的光催化效果,并且随着反应时间的延长,产物的光催化性能减弱。     

过氧化银老化行为的研究

通过对过氧化银相关化学反应的热力学计算,分解机理函数的推导,贮存寿命的计算及贮存性能的研究,得出过氧化银分解为氧气和氧化银的反应是老化的主要原因,分解机理函数为G（a）=[LN（1--a）]^0.5,在室温下贮存寿命大于60年,且硅酸钠处理的过氧化银表现出较好的贮存性能。     

Synthesis and mechanistic study of stable water-soluble noble metal nanostructures

Sodium salt of poly(4-styrenesulfonic acid-co-maleic acid) (PSSMA) has been employed to prepare a series of stable nanosized metal colloids such as silver, gold, palladium, platinum, and silver-gold alloy nanostructures. All of the as-synthesized products are very stable in water. The metal nanostructures have been directly confirmed by ultraviolet-visible spectroscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected area electron diffraction (SAED), and also characterized by techniques such as Fourier transform infrared spectroscopy (FT-IR) and (1)H NMR. Intensive study has found that the metal ions are most probably reduced by organic radicals, generated from the thermal degradation of PSSMA.     

Simple preparation and properties of surface-modified mechanochemically synthesised copper sulphide semiconductor

Nanostructured semiconductor, copper sulphide, CuS prepared by a mechanochemical synthesis in a large-scale operation industrial mill was modified by surfactant-assisted milling in a planetary mill. Surface modified CuS with cetrimonium bromide, and sodium dodecyl sulphate surfactants were characterised by particle size distribution and compared to mechanochemically synthesised CuS. X-ray diffraction, Fourier-transform infrared spectroscopy and elemental analysis confirmed the binding of surfactants to the CuS structure. Transmission electron microscopy has revealed that the particles composed of nanocrystallites are embedded in the surfactant matrix. Their optical properties were studied using ultraviolet–visible and photoluminescence spectroscopies. The optical band gap energies were determined to be 1.70 and 1.63?eV for CuS modified with cetrimonium bromide and sodium dodecyl sulphate.     

Near infrared nonlinearity in silver telluride-core/carbon-sheath and tellurium-core/carbon-sheath nanostructures synthesized by reduction carbonization approach

A reduction-carbonization approach for the formation of one-dimensional (1D) silver telluride nanocables and tellurium nanorods with a sheath of amorphous carbon are proposed. Here the carbon shell is obtained with the assistance of glucose which behaves as carbonizing agent; silver nitrate and sodium tellurite are utilized as precursors and ethylene glycol acts as reducing agent. The results demonstrate the Ag₂Te/C and Te/C nanostructures with average diameters of 150 and 100 nm, respectively. The crystal structures, morphology, and composition are studied using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and Energy-dispersive X-ray spectroscopy characterizations. The formation mechanism of amorphous carbon sheath and finally core–shell nanostructures is elaborated on the basis of the experimental results. In addition, nonlinear absorption and refraction coefficients along with 3rd order nonlinear optical properties are investigated by open/closed-aperture Z-scan measurements using femtosecond pulse laser at 800 nm in a systematic way. This study provides a guide to the nonlinear properties, which may hold promise as advanced materials for various applications.     

低对称性SiO2/Ag核壳复合纳米结构的银镜反应制备及表面增强拉曼散射活性研究

利用银镜反应在自组装的SiO2纳米粒子单层膜上制备了低对称性的SiO2/Ag核壳复合纳米结构.通过透射电镜(TEM)、扫描电镜(SEM)和紫外-可见分光光度计(UV-Vis)对核壳复合纳米结构的表面形貌和光学性质进行了表征.以亚甲基蓝作为探针分子,研究了低对称性SiO2/Ag核壳复合纳米结构的表面增强拉曼散射(SERS)活性.     

Combination of photocatalytic and antibacterial effects of silver oxide loaded on titania nanotubes

Silver nanoparticles were photodeposited on titania nanotubes and their antibacterial activity was tested. Investigation of the structure and morphology of the nanostructures showed nanometer size silver oxide particles homogeneously distributed on titania nanotubes. Furthermore the modified titania nanotubes were spin-coated as thin films and their antibacterial activity was examined under visible light irradiation and in complete darkness. Although silver oxide loaded titania nanotubes (TiNT-AgO) has a potential for antibacterial activity in both conditions with and without light irradiation, enhanced activity was observed in visible light irradiation condition.     

A simple sonochemical synthesis and characterization of CdWO<Subscript>4</Subscript> nanoparticles and its photocatalytic application

Cadmium tungstate (CdWO₄) nanoparticles were synthesized via a sonochemical method based on the reaction between cadmium(II) nitrate hexahydrate and sodium tungstate dihydrate in an aqueous solution. To the best of authors’ knowledge, it is the first time that cadmium tungstate was synthesized by ultrasonic method. The structural, morphological, and optical properties of as-obtained products were characterized by X-ray diffraction, Scanning electron microscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray microanalysis (EDS), and ultraviolet–visible spectroscopy. The as-synthesized cadmium tungstate indicated a ferromagnetic behavior which evidenced by using vibrating sample magnetometer at room temperature. To evaluate the photocatalysts properties of nanocrystalline cadmium tungstate, the photocatalytic degradation of methyl orange under ultraviolet light irradiation was carried out.     

Study on gelatin-silver nanoparticle composite towards the development of bio-based antimicrobial film

Nano-scale silver particle stabilized by gelatin protein was prepared through the reduction of aqueous silver nitrate solution by sodium borohydride. Gelatin concentration was varied against a fixed concentration of silver nitrate to optimize the gelatin to metal ratio. Gelatin-protected Ag-nanoparticle was characterized by UV-VIS spectroscopy and transmission electron microscopy (TEM). All the samples exhibited similar yellow color with a characteristic plasmonic band of silver nanoparticles at 412 nm. TEM micrographs also showed the presence of nanoscale silver particles of approximately 3.9 nm. Since silver has strong bactericidal properties and at the same time relatively less toxic to human cell, silver in various forms is ideally suited for a wide range of applications in consumer, industrial and medical products The antimicrobial properties of gelatin-silver nanocomposites were tested by 'cup-plate zone of inhibition' method. The nanocomposites exhibited significant antibacterial and antifungal activity.     

Self-assembly of alpha-MnO2 nanorods into spheres: synthesis and electrochemical properties

The alpha-MnO2 spherical assemblies were prepared via a facile hydrothermal approach in the presence of sodium dodecyl sulfate (SDS). The assembled nanostructures were composed of the MnO2 nanorods with 150-200 nm in width and several micrometers in length. The products were characterized by SEM, TEM and XRD. The electrochemical characterization was carried out by cyclic voltammetry, which indicated that the alpha-MnO2 spherical assemblies were of an excellent electrode material for supercapacitor.     

Atomic force microscopy and X-ray photoelectron spectroscopy study on nanostructured silver thin films irradiated by atomic oxygen

Nanostructured silver thin films irradiated by atomic oxygen (AO) generated in a ground simulation apparatus were investigated by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). AFM results show that after irradiation, all the grain sizes of the thin films became more or less small, and the compact surface became rough and sparse. From XPS depth profile of an AO-irradiated silver thin film, it can be found that the silver oxides formed exist as two valences, that is, at the surface, the oxide is mainly AgO, and gradually change to Ag₂O, the content of unoxidized silver also increase with depth of film.     

Inorganic template directed assembly of dendritic LDH nanostructures and their properties of morphological preservation and facile exfoliation

We report a novel approach to assembling layered double hydroxide (LDH) into uniform dendritic nanostructures, called nanotrees, in bulk aqueous solution. The key factor of this method lies in the use of inorganic iron hydroxide colloid (IHC), acting as templates to stabilize the LDH layers and gluing them into nanotrees. In this approach, traditional organic templates, such as sodium dodecyl sulfate and urea, are completely avoided. The obtained LDH nanotrees readily show exfoliation properties and can be completely delaminated after modification with silane.     

Room temperature aqueous synthesis of bipyramidal silver nanostructures

The proposed strategy demonstrates a simple method to synthesize the pentagonal right bipyramidal silver nanostructures in aqueous phase at room temperature. Aqueous synthesis enables the materials for direct use in biological systems. The sharp edges of silver nanostructures multiply SERS (surface enhanced Raman spectroscopy) signals by many folds. We have explored a combination of a cationic surfactant, namely, cetyl tri-methyl ammonium bromide (CTAB) and a well-known polymer, polyvinyl pyrrolidone (PVP) for capping preferential crystallographic facets of silver nanosurface. The structural transformation of these anisotropic nanostructures was studied by following various factors, such as, effect of Ag seed concentration, the ratio of concentration of CTAB to the concentration of silver nitrate, the effect of PVP, the ascorbic acid concentration dependence and the effect of pH. CTAB functions as template directing agent while PVP acts as a shape directing agent. Zeta potential measurements and Fourier Transform Infra-red (FTIR) spectral analysis reveal that PVP substitutes CTAB over the facets of silver nanobypiramids.     

Template and template-free preparation of one-dimensional metallic nanostructures

In this article, we have studied and developed two approaches for organizing metallic nanoparticles into one-dimensional assemblies. The first uses DNA as a ‘template’ and allows the preparation of various silver nanostructures (‘beads-on-a-string’ or rod-like wires). The conductance of such nanostructures was demonstrated by employing a powerful technique, Electrostatic Force Microscopy (EFM). This technique gave us ‘contactless’ information about the electrical properties of silver nanostructures, aligned on a SiO₂/Si surface. Additionally, I–V characteristics of a single silver nanowire crossing two microelectrodes were recorded. The nanowire resistivity was estimated at 1.46 × 10⁻⁷ Ω m (at 300 K), which is one order of magnitude higher than that of bulk silver (1.6 × 10⁻⁸ Ω m). The second approach is a ‘template-free’ one, and exploits the binding ability of l-arginine, which favours the self-assembling of capped gold nanoparticles into gold nanochains. The results suggest that gold nanochains were formed due to dipole–dipole interaction between adjacent nanoparticles, which fuse together through an oriented attachment mechanism. Atomic force microscopy, TEM, UV–vis spectroscopy and X-ray diffraction were used to characterize the morphological, optical and structural properties of these metallic nanostructures.     

Morphology and size-controllable preparation of silver nanostructures through a wet-chemical route at room temperature

In this letter a simple wet-chemical route was developed to prepare silver nanostructures. The formation of the silver nanostructures occurs in a single process, carried out by mixing an AgNO₃ aqueous solution and a para-phenylenediamine solution at room temperature without the introduction of other reducing agents and morphology controlling agents. It is found that both the morphology and the size of such silver nanostructures can be facilely controlled by the molar ratio and concentration of the reactants as well as the solvent that was used to dilute para-phenylenediamine aqueous solution. As-formed silver nanostructures were examined by scanning electron microscopy.     

Surface-Enhanced Infrared Absorption Spectroscopic Investigation of Benzamide Thin-Film Formation,Stability, and Catalysis on Gold and Silver Nanostructures

Benzamide (BA), a simple molecule that can be utilized in material chemistry and chemical engineering as well as pharmacological and medicinal applications, has been characterized on vacuum-evaporated silver and gold nanostructures with SEIRA spectroscopy and density functional theory (DFT) calculation under ambient conditions. Assessments of thin-film formation on the metal nanoparticles indicated that BA readily ionizes in both the monolayer and multilayer when deposited from nonpolar solvents. Investigation on the stability of BA on metal nanostructures showed that unionized BA desorbs from the nanosurface within days while ionized BA on silver nanostructures can undergo further oxidation over time, producing surface-adsorbed phenyl isocyanate. Also, a brief investigation on variables influencing IR signal enhancement provided by the metal nanosurfaces was conducted; in general, gold nanostructures provide more enhancement than silver.     

Synthesis and electrochromic application of surfactants tailored WO3 nanostructures

As WO₃ is excellent material for electrochromic displays more investigation is needed to find the good and low cost method for preparation of WO₃ nanostructures with uniform morphology and narrow distributions using a surfactant mediated method. In this study, the synthesis of WO₃ nanostructures was accomplished using various surfactants such as polyethylene glycol, sodium chloride and sodium dodecyl sulfate and sodium tungstate and diethyl sulfate as the inorganic precursors. All samples were characterized for their opto-structural and morphological studies by UV-Vis spectrophotometer, X-ray diffractometer and scanning electron microscopy techniques. The electrochromic performance of these samples was studied in LiClO₄/PC as electrolyte for Li⁺ insertion/extraction. The use of surfactants has been employed to enhance the uniformity of WO₃ samples.     

Formation of novel assembled silver nanostructures from polyglycol solution

This paper described a simple and mild chemical reduction approach to prepare novel silver nanostructures with different morphologies. Dendritic silver nanostructure was obtained by a fast reduction reaction using hydrazine as a reducing agent in aqueous solution of polyglycol, while both the zigzag and linear Ag nanostructures were slowly assembled using polyglycol as a reducing agent. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM) and field emission scanning electron microscopy (FE-SEM) were used to characterize the obtained silver nanostructures. Fourier transform infrared absorption (FT-IR) spectra were recorded to show that there exists a certain coordination of the oxygen atoms in the polyglycol with Ag⁺ ions in aqueous solution of the AgNO₃/polyglycol. Furthermore, the examination of the morphologies of the products obtained at different stages of the reaction of Ag⁺ ions with polyglycol revealed that such a coordination is of utmost importance for the formation of the silver nanostructures, namely polyglycol provided lots of active sites for the coordination, nucleation, growth and serves as backbones for directing the assembly of the metal particles formed. The formation mechanism of the dendritic silver nanostructure was called a coordination–reduction–nucleation–growth–fractal growth process. The strong surface plasmon absorption bands at 470 nm for the zigzag silver and at 405 nm for the dendritic silver were found.