Study on the effect of electrostatic interaction on core-shell nanoparticles preparation with microemulsion technique

The routine method for preparation of silica core-shell nanoparticles （NPs） is to carry out nucleation and shell coating through the hydrolysis of silane in water in oil （W/O） microemulsion to form three-dimensional netted silica shell. We found that electrostatic interaction of the core materials with shell materials would determine whether the stable core-shell silica NPs formed or not. The traditional important factors such as molecular weight of core materials or the thickness of the shell have no obvious relationship with it. And the stability of the core-shell silica NPs can be improved after changing the electric charge polarity by regulating the experiment condition of relevant materials ff some core materials cannot be doped inside to form the stable core-shell silica NPs based on the traditional method, which provided experimental and theoretic foundation for preparation and application of the core-shell silica NPs.     

Nbn(n=2-15)小团簇的第一性原理研究

【目的】研究纳米尺寸Nbn小团簇的结构演变过程,为进一步讨论Nbn小团簇的催化氧化性质提供参考。【方法】采用基于密度泛函理论(包括PW91和BLYP函数)的第一性原理计算方法对Nbn(n=2-15)小团簇的几何结构进行优化计算。【结果】随着原子数n的增加,Nbn(n=2-15)小团簇的结构及其特性具有明显的变化,平均每原子结合能(Binding Energy)随着原子数的增加呈递减趋势。【结论】Nbn(n=2-15)小团簇随尺寸变化具有明显的奇偶震荡性,n为偶数时比n为奇数时的结构稳定,其中Nb4、Nb6、Nb8、Nb10、Nb12小团簇结构较为稳定。     

Effect of milling process on the core-shell structures and dielectric properties of fine-grained BaTiO3-based X7R ceramic materials

Fine-grained BaTiO₃-based X7R ceramic materials were prepared and the effects of milling process on the core-shell structures and dielectric properties were investigated using scanning electron microscope, transmission electron microscope, and energy dispersive spectroscopy (EDS). As the milling time extends, the dielectric constant of the ceramics increases, whereas the temperature coefficient of capacitance at 125℃ drops quickly. The changes in dielectric properties are considered relevant to the microstructure evolution caused by the milling process. Defects on the surface of BaTiO₃ particles increase because of the effects of milling process, which will make it easier for additives to diffuse into the interior grains. As the milling time increases, the shell region gets thicker and the core region gets smaller; however, EDS results show that the chemical inhomogeneity between grain core and grain shell becomes weaker.     

TiO<Subscript>2</Subscript>@MgO core-shell film: Fabrication and application to dye-sensitized solar cells

In this study,TiO2@MgO core-shell film was obtained by using a simple chemical bath deposition method to coat a thin MgO film around TiO2 nanoparticles. The core-shell configuration was characterized by X-ray diffractometer (XRD),scanning elec-tron microscopy (SEM),energy dispersive X-ray spectroscopy (EDX),and high-resolution transmission electron microscopy (HRTEM). Lattice fringes were observed for the TiO2 particles,and the MgO shell showed an amorphous structure,revealing a clear distinction between the core and shell materials. Applying the core-shell film as photoanode to the dye-sensitized solar cells (DSSCs),it shows a superior performance compared to the pure TiO2 electrode. Under the illumination of simulated sunlight (75 mW-cm-2),the short circuit photocurrent (Jsc),the open circuit photovoltage (Voc),and the fill factor (fF) are 8.80 mA-cm-2,646 mV,and 0.69,respectively,and the conversion efficiency (η) in-creased by 21.8% (from 4.32% to 5.26%) when dipping for opti-mum condition.     

<Emphasis Type="Italic">Ab initio</Emphasis> study of the effects of Ag/Mn doping on the electronic structure of LiFePO<Subscript>4</Subscript>

Based on density functional theory （DFT） of the first-principle for the cathode materials of lithium ion battery, the electronic structures of Li（Fe1-x）PO4 （Me = Ag/Mn, x = 0-0.40） are calculated by plane wave pseudo-potential method using Cambridge serial total energy package （CASTEP） program. The calculated results show that the Fermi level of mixed atoms Fe1-xAgx moves into its conduction bands （CBs） due to the Ag doping. The Li（Fe1-xAgx）PO4 system displays the periodic direct semiconductor characteristic with the increase of Ag-doped concentration. However, for Fe1-xMnx mixed atoms, the Fermi level is pined at the bottom of conduction bands （CBs）, which is ascribed to the interaction between Mn（3d） electrons and Fe（4s） electrons. The intensity of the partial density of states （PDOS） near the bottom of CBs becomes stronger with the increase of Mn-doped concentration. The Fermi energy of the Li（Fe1-xMnx）PO4 reaches maximum at x = 0.25, which is consistent with the experimental value of x = 0.20. The whole conduction property of Mn-doped LiFePO4 is superior to that of Ag-doped LiFePO4 cathode material, but the structural stability is reverse.     

Visible-light-driven Ag/Ag3PO4-based plasmonic photocatalysts: Enhanced photocatalytic performance by hybridization with graphene oxide

An efficient visible-light-driven plasmonic photocatalyst with regard to graphene oxide(GO) hybridized Ag/Ag3PO4(Ag/Ag3PO4/GO) nanostructures has been facilely synthesized via a deposition-precipitation method.The synthesized nanostructures have been characterized by means of scanning electron microscopy(SEM),energy-dispersive X-ray spectroscopy(EDX),X-ray diffraction(XRD),UV-vis spectra,Fourier transform infrared spectra(FT-IR),X-ray photoelectron spectroscopy(XPS),and Raman spectra.It has been disclosed that compared with the bare Ag/Ag3PO4 nanospecies,the GO hybridized nanostructures display enhanced photocatalytic activity for the photodegradation of methyl orange pollutant under visible-light irradiation.It is suggested that the reinforced charge transfer and the suppressed recombination of electron-hole pairs in Ag/Ag3PO4 /GO,the smaller size of Ag/Ag3PO4 nanospecies in Ag/Ag3PO4/GO,all of which are the consequences of the hybridization of GO,are responsible for the enhanced photocatalytic performance.The investigation might open up new opportunities to obtain highly efficient Ag3PO4-based visible-light-driven plasmonic photocatalyst for the photodegradation of organic pollutants.     

Cd类核壳型纳米粒子的制备及表征

以巯基乙酸为稳定剂,在水溶液中合成CdSe和CdTe及CdSexTe1-x核纳米粒子,用ZnS纳米粒子包覆核纳米粒子,制备出水溶性CdSe/ZnS和CdTe/ZnS及CdSexTe1-x/ZnS核壳型纳米粒子.用荧光光谱、高倍透射电镜等技术对核纳米粒子及核壳纳米粒子进行表征,以荧光光谱研究了时间、稳定剂用量等因素对核壳型纳米粒子光谱特性的影响.     

Transient photoconductivity in a-(Se80Te20)100 xAgx (0rxr4) thin films

Bulk material of (Se80Te20)100 xAgx (0rxr4) system was prepared by using a conventional melt quenching technique. Thin films of a-(Se80Te20)100 xAgx (0rxr4) were deposited by the vacuum evaporation technique at a base pressure of 10 4 mbar onto well-cleaned glass substrates. Temperature dependence of electrical conductivity in the temperature range of 263–333 K has been studied. There is increase in the value of conductivity with increase in temperature as well as with Ag content. The measurements of intensity dependence of photoconductivity show that the photoconductivity increases with intensity as a power law where the power is found to be between 0.5 and 1.0, representing the continuous distribution of traps. Rise and decay of photocurrent with time at room temperature at different light intensities for (Se80Te20)98Ag2 thin film samples have also been reported. The results have been explained on the basis of the Dember voltage and interaction between photoexcited holes and the trapped electrons on the surface.     

Mechanism of Ag and Al on improving the glass forming ability of CuZr-based alloys

By a mean field theoretical computation, the equilibrium distributions of additional Ag and Al in the crystalline phase of CuZr-based alloys were determined to occupy the two sublattices of the B2 structure randomly. With the molecular dynamics technique, the effects of Ag and Al on the enthalpy difference (ΔH) between the supercooled melt and the crystalline phase were evaluated. The improved glass forming ability of Cu₄₅Zr₄₅Al₁₀and Cu₄₅Zr₄₅Ag₁₀ can be attributed to their remarkably smaller ΔH than that of CuZr. The calculated diffusion coefficients are more sensitive to the atomic weight of the component atoms than to their interaction strength. As the component atom with the largest mass, the additional Ag increases the viscosity of the supercooled melt significantly and the experimentally stronger glass formation ability of Cu₄₅Zr₄₅Ag₁₀ than Cu₄₅Zr₄₅Al₁₀ can be well understood.     

Size-controlled synthesis of Fe3O4 and Fe3O4@SiO2 nanoparticles and their superparamagnetic properties tailoring

Superparamagnetic properties and fine-tuning of colloidal Fe₃O₄nanoparticles are important for their widespread biomedical applications. Herein, colloidal Fe₃O₄nanoparticles(NPs) of different sizes(8–20 nm) were prepared,and their hydrophilization with SiO₂shell coating to be Fe₃O₄@SiO₂core-shell had been realized successively.The size of Fe₃O₄NPs was controlled by different heating rate...     

Ag@Pt核壳结构纳米粒子催化剂在电催化过程中的失效分析

通过种子生长法和自组装技术合成Ag@Pt核壳结构纳米粒子(以下简称Ag@Pt粒子),测量和比较在电催化循环伏安扫描(以下简称CV扫描)过程中失效前后的Ag@Pt粒子对甲醇的电催化性能的变化,采用透射电镜、高分辨电镜、X射线光电子能谱等方法研究其失效机理.结果表明：Ag@Pt粒子在循环伏安扫描的过程中会发生空化现象,其临界电压为0.5 V,空化现象随时间的增长而变得明显;Ag@Pt粒子空化后形成由Ag包覆空心Pt壳的纳米粒子,这是导致其在对甲醇进行电催化氧化过程中催化性能明显下降的原因.     

一维Cu@C核壳结构纳米复合材料的制备与表征

以氯化铜作为铜源,六次甲基四胺（HMT）作还原剂和碳源,十六烷基三甲基溴化铵（CTAB）作表面活性剂,在水热条件下合成了一维Cu@C核壳结构纳米复合材料,并进行了表征分析。结果表明,制备的Cu@C核壳结构纳米复合材料为立方相铜晶体,无杂质出现。长度在几微米到十几微米,直径大约200-400nm。产物由铜、碳2种元素构成;从透射电镜照片可以清楚的看出明暗对比,表明产物的核壳结构。在反应过程中,十六烷基三甲基溴化铵（CTAB）起到了形状控制剂的作用。     

Structural and electrical properties of HCl-polyaniline-Ag composites synthesized by polymerization using Ag-coated (NH4)2S2O8 powder

Ag nanoparticles were sputter-deposited on ammonium persulfate ((NH₄)₂S₂O₈) powder to obtain (NH₄)₂S₂O₈-Ag powder, which was used to synthesize the HCl-doped polyaniline-Ag (HCl-PANI-Ag) composite via a polymerization procedure. The Ag nanoparticles were dispersed in the HCl-PANI matrix, and their sizes mainly ranged from 3 to 6 nm. The Ag nanoparticles did not affect the structure of emeraldine salt in the composite, and they increased the ordered crystalline regions in the HCl-PANI matrix. The HCl-PANI-Ag composite had a conductivity of (6.8 ±0.1) S/cm, which is about four times larger than that of the HCl-PANI. The charge transport mechanism in the composite is explained by the three-dimensional Mott variable-range hopping (3D-Mott-VRH).     

单分散聚苯乙烯/二硫化钼纳米复合微球的制备与分散性

以二硫化钼为核,聚苯乙烯为壳,通过种子乳液聚合方法,成功制备了具有核壳结构的聚苯乙烯/二硫化钼(PS/MoS2)有机-无机纳米复合微球。利用紫外可见吸收光谱、透射电镜、扫描电镜、能量色散谱仪等多种方法,对PS/MoS2纳米微球的形貌、结构进行了表征,同时,利用分散性试验考察了PS/MoS2纳米微球在油溶性单体双环戊二烯(DCPD)中的分散性。试验结果表明:聚苯乙烯包覆在MoS2的表面,形成核壳结构;纳米粉体呈球形且粒径尺寸均一。分散性试验表明PS/MoS2纳米微球在DCPD中具有极佳的分散性。     

Cylindrical PCL brushes on the surface of lanthanum hydroxide nanowires by ring-opening polymerization

A core-shell hybrid nanostructure,a hard core of single-crystalline lanthanum hydroxide nanowires and a soft shell of brushes of poly (ε-caprolactone) (PCL), has been successfully prepared by ring-opening polymerization (ROP) on the surface of nanowires. Such special structures were proved by TEM images. Meanwhile, the thickness of polymer layers was measured. The chemical component and the grafted PCL quantity of the sample were characterized by FTIR and TGA, which provides a simple and universal method to...     

Co3O4/Fe2O3核-壳粒子的制备及光学性能研究

在单分散准球形-αFe2O3纳米颗粒的悬浮液中,在氨碱催化下,CoCl2水解产生的Co(OH)2沉积在-αFe2O3纳米颗粒表面,形成核-壳粒子.经500℃热处理后,壳层物质晶化为立方晶系Co3O4,壳层厚度约为6 nm.不同的氨碱液对核-壳结构产生影响,在1 mol.L-1尿素溶液的催化下,得到均匀的核-壳结构.应用TEM和XRD分析了产物结构,并利用UV-Vis光谱对复合材料的光吸收特性进行了研究.与-αFe2O3纳米颗粒的吸收光谱比较,在光激发下,Co3O4/Fe2O3核-壳粒子光吸收特性发生改变,在可见光区产生新的强吸收峰.     

Synthesis and characterization of high density and high aspect ratio Ag<Subscript>2</Subscript>S nanoparticle nanowires from a paired cell method

Ag₂S nanoparticle nanowires were prepared in a porous anodic aluminum oxide template by a simple paired cell method,and were characterized by XRD,FESEM,HRTEM and EDS.The results showed that the as-prepared nanowires were composed of monoclinic Ag₂S nanoparticles.The nanowire diameters ranged from 165 to 270 nm,and Ag₂S nanoparticles were nearly spherical with diameters of 40 to 60 nm.The paired cell method is simple,low cost and easy to control for the fabrication of high density and high aspect ratio Ag₂S nanoparticle nanowires.A formation mechanism for the nanoparticle nanowires was suggested.     

新型银-二氧化硅核-壳型复合纳米粒子的合成与表征

利用正四甲氧基硅在微乳液介质中的水解反应合成新型银 -二氧化硅核 -壳型复合纳米粒子 .通过化学反应调控 ,直径为 5～ 1 0 nm的金属银纳米粒子可以以单核或多核形式嵌入并分布于球型二氧化硅粒子中 .透射电子显微镜照片表明 ,该复合粒子具有高度均匀的粒径分布 .     

CNTs/mesostructured silica core-shell nanowires via interfacial surfactant templating

Carbon nanotubes (CNTs)/mesostructured silica core-shell nanowires with a carbon nanotube core and controllable highly ordered periodic mesoporous silica shell are syntheiszed via the interfacial surfactant template. The core-shell nanowires are characterized by transmission electron microscope (TEM), X-ray diffraction pattern (XRD) and nitrogen sorption/desorption. The results indicate that the core-shell nanowires have highly ordered periodic mesoporous silica shell (space group p6mm), high BET surface area and narrow pore size distribution. Moreover, the morphology of core-shell nanowires can be controlled by the pH value. The core-shell nanowires have promising applications in biosensors, nanoprobes and energy storage due to their good dispersibility in polar solvents. Supported by the Australian Research Council (ARC) through Discovery Project program (DP0452461)     

Preparation,characterization and release of methyl viologen from a novel nanoparticle delivery system with double shells of silica and PLGA

The use of nanotechnology in drug delivery is a rapidly expanding field. Biodegradable or nontoxic nanomaterials have the most promising application potentials in nanomedicine. Herein, we report a novel core-shell nanoparticle with double shell coatings (silica and poly(D,L-lactide-co-glycolide) (PLGA)) with the total shell thickness of (8.7 ± 1.3) nm. The outer shell of PLGA is biodegradable and used for controlled and sustained release, and the inner shell of silica is mesoporous for the preservation of t...