Chemical and electrocatalytical interaction: influence of non-electroactive ceramic nanoparticles on nickel electrodeposition and composite coating

This article focuses on the nanoparticle electrocatalytical action on electrodeposition of nickel and the chemical combination state between nanoparticles and matrix metal in composite coating. The electrochemical behavior, from common and composite brush electroplating solution, is investigated by cyclic voltammetry. The interaction between nanoparticles and matrix metal nickel is researched by X-Ray Photoelectron Spectrometry (XPS). The microstructure and morphology of coating are observed with Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM). The results show that nanoparticles not only can obviously induce the increasing of the current efficiency and decreasing of overpotential, but also can distinctly refine the metal crystal grains of composite coating. The experimental results demonstrate that nanoparticles take part in the electrode reaction and can evidently catalyze nickel electrodeposition. Part of the unsaturated oxygen atoms on nanoparticles surface can combine with some of the absorbed nickel atoms and form nickel-oxygen chemical bonds. There is chemical binding interaction at the interface between nanoparticles’ surface and matrix metal nickel.     

Electrocatalytic action of nano-SiO2 with electrodeposited nickel matrix

The present work focuses on the electrocatalytic effect of nano-SiO₂ on nickel electrodeposition and chemical interaction between nano-SiO₂ and nickel in composite coating. The electrochemical behavior from n-SiO₂/Ni composite brush plating system and quick nickel solution are investigated using cyclic voltammetry. The interaction between n-SiO₂ particles and matrix metal nickel is researched by X-ray photoelectron spectrometry. The results show that the n-SiO₂ take part in the electrode reaction during nickel electrocrystallization and can catalyze the nickel electrodeposition. The unsaturated bond of oxygen on n-SiO₂ particles surface can capture some of the absorbed nickel atoms and form nickel–oxygen chemical bond. It is proved that the chemical binding interaction exists in the interface between nanoparticles surface and matrix metal nickel.     

Cu-Fe基粉末烧结金刚石复合材料界面结合特性

以Cu-Fe基粉末为基体材料,在真空压力烧结条件下制备了金刚石复合材料。利用扫描电镜、能谱仪、X射线衍射仪等研究粉末与金刚石颗粒界面结合特性。结果表明,930℃、15MPa烧结温度和压力下,烧结胎体中Fe原子向金刚石表面扩散,形成一定厚度的扩散层,并与金刚石中的C发生化学反应生成Cfe15,呈非连续层片状分布于金刚石颗粒表面,实现了金刚石颗粒与金属的化学键结合。     

A renewable electrochemical magnetic immunosensor based on gold nanoparticle labels

A particle-based renewable electrochemical magnetic immunosensor was developed by using magnetic beads and gold nanoparticle labels. Anti-IgG antibody-modified magnetic beads were attached to a renewable carbon paste transducer surface by magnet that was fixed inside the sensor. Gold nanoparticle labels were capsulated to the surface of magnetic beads by sandwich immunoassay. Highly sensitive electrochemical stripping analysis offers a simple and fast method to quantify the capatured gold nanoparticle tracers and avoid the use of an enzyme label and substrate. The stripping signal of gold nanoparticles is related to the concentration of target IgG in the sample solution. A transmission electron microscopy image shows that the gold nanoparticles were successfully capsulated to the surface of magnetic beads through sandwich immunoreaction events. The parameters of immunoassay, including the loading of magnetic beads, the amount of gold nanoparticle conjugate, and the immunoreaction time, were optimized. The detection limit of 0.02 microg ml(-1) of IgG was obtained under optimum experimental conditions. Such particle-based electrochemical magnetic immunosensors could be readily used for simultaneous parallel detection of multiple proteins by using multiple inorganic metal nanoparticle tracers and are expected to open new opportunities for disease diagnostics and biosecurity.     

Observation of sulfur on the surface of giant aurothiol nanoclusters

We report the study of aurothiol nanoclusters using high-resolution electron microscopy, energy loss spectroscopy, X-ray photoelectron spectroscopy, Auger spectroscopy, and microscopy. It is concluded that the sulfur atoms are located on the surface of the gold nanoparticles in both (100) and (111) microfacets. The X-ray photoelectron spectroscopy data show that there is a Au-Au bond as well as a Au-S bond. Auger depth profile measurements made by sputtering of the nanoparticles corroborates that the sulfur is located on the surface of the nanoparticle. Quantitative Auger analysis indicates a ratio Au/S between approximately 1.79 and 1.98.     

Surface states at the nanoparticle-polymer matrix interface

The energy barriers for hole injection in polymeric nanocomposites representing a poly(p-xylylene) (PPX) matrix containing dispersed lead or iron nanoparticles were determined by means of photoconductivity spectroscopy. The barriers for hole injection from metal particles in nanocomposites measured in vacuum are 3.6 eV for iron and 3.0 eV for lead; upon oxygen admission, these values decrease to ～3.2 and ～2.75 eV, respectively. A shift between the vacuum energy levels of PPX and metal nanoparticles amounts to 1.0 and 0.1 eV for iron and lead, respectively. The greater value for iron suggests the formation of a surface electric dipole, probably as a result of the chemical interaction at the metal nanoparticle-matrix interface.     

Chemical Immobilization Effect on Lithium Polysulfides for Lithium–Sulfur Batteries

Despite great progress in lithium–sulfur batteries (LSBs), great obstacles still exist to achieve high loading content of sulfur and avoid the loss of active materials due to the dissolution of the intermediate polysulfide products in the electrolyte. Relationships between the intrinsic properties of nanostructured hosts and electrochemical performance of LSBs, especially, the chemical interaction effects on immobilizing polysulfides for LSB cathodes, are discussed in this Review. Moreover, the principle of rational microstructure design for LSB cathode materials with strong chemical interaction adsorbent effects on polysulfides, such as metallic compounds, metal particles, organic polymers, and heteroatom‐doped carbon, is mainly described. According to the chemical immobilizing mechanism of polysulfide on LSB cathodes, three kinds of chemical immobilizing effects, including the strong chemical affinity between polar host and polar polysulfides, the chemical bonding effect between sulfur and the special function groups/atoms, and the catalytic effect on electrochemical reaction kinetics, are thoroughly reviewed. To improve the electrochemical performance and long cycling life‐cycle stability of LSBs, possible solutions and strategies with respect to the rational design of the microstructure of LSB cathodes are comprehensively analyzed.     

A facile method to prepare noble metal nanoparticles modified Self-Assembly (SAM) electrode

Noble metal nanoparticles (NPs) modified electrodes have shown promising applications in the areas of catalysis, (electro)chemical analysis and biosensing due to their unique characters. In this paper, we introduced a so-called ligand exchange method to prepare self-assembly (SAM) electrode modified with noble metal nanoparticles. The noble metal nanoparticles protected by weakly adsorbed tetraoctylammonium bromide (TOAB) were synthesized firstly, then self-assembly (SAM) dithiol-modified Au electrode (Au-SH_SAM) was immersed into the solutions containing TOAB-protected nanoparticles. Due to the strong interaction between the dithiol groups on the electrode and noble metal nanoparticles, the weakly adsorbed TOAB on the surface of noble metal NPs were replaced by dithiol groups. As a result, the TOAB protected NPs were anchored on the Au-SH_SAM template electrode surface by ligand exchange, obtaining noble metal NPs modified electrode with high quality and stability. By adjusting the soaking time, the coverage of nanoparticles on the Au-SH_SAM electrode surface could be controlled. The morphology and distribution of noble metal NPs on Au-SH_SAM surface was analysis by scanning tunneling microscope (STM), and their electrochemical property was studied by cyclic voltammetry (CV) in H₂SO₄ solution. The approach is proved as a universal way to prepare noble metal NPs modified SAM electrode.     

SiC陶瓷与Zn界面结合特性的第一性原理研究

低温焊接SiC陶瓷是金属/陶瓷连接领域非常重要的研究方向,而与之相关的理论研究相对匮乏,同时,通过实验手段难以描述金属/陶瓷界面原子之间的相互作用。为研究低温Zn基钎料与SiC陶瓷的界面结合方式,采用第一性原理方法,计算了Zn(0001)和SiC(0001)的表面能,6种不同堆垛方式的Zn(0001)/SiC(0001)界面模型的分离功,并分析了其中最稳定两种模型的电荷密度图、电荷密度差分图和Mulliken布局。结果表明:Zn/SiC界面只形成了Zn-Si离子键,Si终端孔穴型界面的Zn-Si键结合强度高于C终端孔穴型。     

单分散金属硫化物纳米颗粒的简单制备方法

提出了一种制备单分散金属硫化物纳米颗粒的简单方法。在低热条件下疏水性三硫代碳酸盐分解释放出活性硫元素和硫醇,可分别作为反应体系的供硫剂和表面活性剂,产物金属硫化物纳米晶因吸附硫醇而保持良好的分散性。通过该法制备了A＆s和cu2s纳米颗粒,在对其形貌和尺寸表征的基础上,对其形成机制进行了讨论。     

Synthesis and magnetic properties of nickel nanoparticles in magnesium fluoride matrix

A new composite material, comprising a diamagnetic matrix (magnesium fluoride) containing metal nanoparticles (nickel), has been synthesized in a high-vacuum laser-based universal cluster ablation system. The structure and magnetic properties of the composite were studied by transmission electron microscopy (TEM) and ferromagnetic resonance (FMR). According to TEM data, the nickel nanoparticles have a spherical shape and their dimensions are described by a narrow distribution function with an average value of 3.2 nm. An analysis of the FMR spectra reveals strong interaction between nickel nanoparticles in the composite, which accounts for an out-of-plane magnetic anisotropy and suggests the formation of granular magnetic films.     

The effect of cysteine on electrodeposition of gold nanoparticle

The most applications of gold nanoparticles are in the photo-electronical accessories and bio-chemical sensors. Chloride solution with cysteine additive was used as electrolyte in gold nanoparticles electrodeposition. The nucleation and growing mechanism were studied by electrochemical techniques such as cyclic voltammetry and chronoamperometry, in order to obtain a suitable nano structure. The deposition mechanism was determined as instantaneous nucleation and the dimension of particles was controlled in nanometric particle size range. Atomic Force Microscope was used to evaluate the effect of cysteine on the morphology and topography of gold nanoparticles. Finally the catalytic property of gold nanoparticle electrodeposited was studied in KOH solution, where oxygen reduction on the gold nanoparticle surface was eight times greater than that on the conventional gold deposits.     

UV/Vis visible optical waveguides fabricated using organic-inorganic nanocomposite layers

Nanocomposite layers based on silica nanoparticles and a methacrylate matrix are synthesized by a solvent-free process and characterized in order to realize UV/Vis transparent optical waveguides. Chemical functionalization of the silica nanoparticles permits to interface the polymers and the silica. The refractive index, roughness and wettability and the machinability of the layers can be tuned changing the silica nanoparticle concentration and chemical modification of the surface of the nanoparticles. The optical transparency of the layers is affected by the nanoparticles organization between the organic chains, while it increased proportionally with respect to silica concentration. Nanocomposite layers with a concentration of 40 wt% in silica reached UV transparency for a wavelength of 250 nm. UV/Vis transparent waveguides were micromilled through nanocomposite layers and characterized. Propagation losses were measured to be around 1 dB cm(-1) at a wavelength of 350 nm.     

Controllable synthesis of uncapped metal nanoparticle assembly at the air–water interface

A two-dimensional self-assembly of uncapped Ag nanoparticles was prepared at the air–water interface. In the experiment, ethanol was added into the Ag-based colloid to reduce the surface charge density on the nanoparticles and the air–water interfacial energy, leading to the nanoparticles adsorption and assembling at the air–water interface. It was found that the array structure was controllable. The ordered nanoparticle array could be changed to a fractal structure by varying gradually the amount of the added ethanol. Moreover, it was demonstrated that the assembly was sensitive to the surface charge density on the particles, the Debye length in the colloid and the interfacial tension between nanoparticle/water (air).     

Study of DNA interaction with cobalt ferrite nanoparticles

Interaction of cobalt ferrite nanopowder and nucleic acid was investigated. Superparamagnetic cobalt ferrite nanoparticles (6-12 nm) were prepared by mechanochemical synthesis. Structure of the nanopowder was characterized using X-ray diffraction. It was shown that cobalt ferrite nanoparticles were associated with ssDNA and dsDNA in Tris-buffer resulting in bionanocomposite formation with mass weight relation nanoparticles: DNA 1:(0.083 +/- 0.003) and 1:(0.075 +/- 0.003) respectively. The mechanism of interaction between a DNA and cobalt ferrite nanoparticles was considered basing on the whole set of obtained data: FTIR-spectroscopy, analyzing desorption of DNA from the surface of the particles while changing the chemical content of the medium, and on the modeling interaction of specific biomolecule fragments with surface of a inorganic material. It was supposed that the linkage was based on coordination interaction of the phosphate groups and oxygen atoms heterocyclic bases of DNA with metal ions on the particle surface. These data can be used to design specific magnetic DNA-nanoparticles hybrid structures.     

Effect of Co and Ni nanoparticles formation on carbon nanotubes growth via PECVD

The effect of cobalt (Co) and nickel (Ni) nanoparticle catalysts on the growth of carbon nanotubes (CNTs) were studied, where the CNTs were vertically grown by plasma enhanced chemical vapour deposition (PECVD) method. The growth conditions were fixed at a temperature of 700 °C with a pressure of 1000 mTorr for 40 minutes with various thicknesses of sputtered metal catalysts. Only multi-walled carbon nanotubes are present from the growth as large average diameter of outer tube (～10–30 nm) were measured for both of the catalysts used. Experimental results show that high density of CNTs was observed especially towards thicker catalysts layers where larger and thicker nanotubes were formed. The nucleation of the catalyst with various thicknesses was also studied as the absorption of the carbon feedstock is dependent on the initial size of the catalyst island. The average diameter of particle size increases from 4 to 10 nm for Co and Ni catalysts. A linear relationship is shown between the nanoparticle size and the diameter of tubes with catalyst thicknesses for both catalysts. The average growth rate of Co catalyst is about 1.5 times higher than Ni catalyst, which indicates that Co catalyst has a better role in growing CNTs with thinner catalyst layer. It is found that Co yields higher growth rate, bigger diameter of nanotube and thicker wall as compared to Ni catalyst. However, variation in Co and Ni catalysts thicknesses did not influence the quality of CNTs grown, as only minor variation in I_G/I_D ratio from Raman spectra analysis. The study reveals that the catalysts thickness strongly affects not only nanotube diameter and growth rate but also morphology of the nanoparticles formed during the process without influencing the quality of CNTs.     

Encapsulation of Single Plasmonic Nanoparticles within ZIF‐8 and SERS Analysis of the MOF Flexibility

Hybrid nanostructures composed of metal nanoparticles and metal‐organic frameworks (MOFs) have recently received increasing attention toward various applications due to the combination of optical and catalytic properties of nanometals with the large internal surface area, tunable crystal porosity and unique chemical properties of MOFs. Encapsulation of metal nanoparticles of well‐defined shapes into porous MOFs in a core–shell type configuration can thus lead to enhanced stability and selectivity in applications such as sensing or catalysis. In this study, the encapsulation of single noble metal nanoparticles with arbitrary shapes within zeolitic imidazolate‐based metal organic frameworks (ZIF‐8) is demonstrated. The synthetic strategy is based on the enhanced interaction between ZIF‐8 nanocrystals and metal nanoparticle surfaces covered by quaternary ammonium surfactants. High resolution electron microscopy and tomography confirm a complete core–shell morphology. Such a well‐defined morphology allowed us to study the transport of guest molecules through the ZIF‐8 porous shell by means of surface‐enhanced Raman scattering by the metal cores. The results demonstrate that even molecules larger than the ZIF‐8 aperture and pore size may be able to diffuse through the framework and reach the metal core.     

Assembly of phase transferred nickel nanoparticles at air-water interface using Langmuir-Blodgett technique

Development of simple and efficient protocol for the synthesis of Ni nanoparticles in aqueous media and their subsequent phase transfer to organic media is reported. The synthesis of nickel nanoparticles in aqueous medium is accomplished by reducing the nickel nitrate with sodium borohydride in presence of oleic acid. It results in the formation of nickel nanoparticles capped with oleic acid. The pristine oleic acid capped nickel nanoparticles were then phase transferred to nonpolar solvents such as toluene using stearic acid. The phase transfer was effective probably due to the space exchange between the oleic acid moiety and stearic acid molecules. The hydrophobized Ni thus obtained was organized at the air-water interface and it was observed that by controlling the pressure and concentration of hydrophobized Ni nanoparticles at air-water interface, linear ribbon like assemblies could be obtained. The organization process was followed by surface pressure-area isotherm measurement and Brewster Angle Microscopy.     

Development of organic dye-doped silica nanoparticles for bioanalysis and biosensors

The combination of two silica precursors, tetraethylorthosilicate and phenyltriethoxysilane, were utilized to synthesize organic dye-doped silica nanoparticles. The hydrophobic nature of phenyltriethoxysilane keeps the organic dye in the silica matrix, whereas the hydrophilic tetraethylorthosilicate-formed silica allows the resulting nanoparticles to be dispersed in aqueous solutions. Characterization of the nanoparticles showed that they could be synthesized in the nanometer range with high photostability and minimal dye leakage. The silica matrix of the nanoparticles allows different routes of surface biomolecular modification for biosensor and bioanalysis applications. We have shown different applications of the nanoparticles in bioanalysis and in biosensing. Biotin interaction of avidin-coated nanoparticles can be used for the determination of biotinylated bovine serum albumin, and the immobilization of glutamate dehydrogenase on the nanoparticle surfaces enables the nanoparticles to be used as biosensors for glutamate determination.     

XRD, TEM, IR and 29Si MAS NMR characterization of NiO-SiO2 nanocomposites

The present study focuses on the structural properties of a NiO-SiO₂nanocomposite with 14 mol % of nickel oxide obtained by a sol-gel method and a gradual heating the gel in the 350–900°C range. NiO nanoparticles and their dispersion in the amorphous silica matrix were studied through TEM and XRD. The behaviour at the nanoparticle/matrix interface was investigated through IR and ²⁹Si MAS NMR spectroscopy comparing the spectra of the nanocomposite with that of a silica sample obtained with the same preparation method and submitted to the same thermal treatments. The results indicate that nanoparticles, formed in cavities of the silica matrix, act as an obstacle towards the spontaneous silica polymerization process with heat treatments.