热处理条件对硅酸盐玻璃中原位形成银纳米颗粒的影响

用离子交换结合热处理法制备银(Ag)纳米颗粒-玻璃复合材料.用透射电镜、高分辨透射电子显微镜、Ruthefford背散射谱和紫外-可见光吸收光谱研究了热处理条件对玻璃中原位形成Ag纳米颗粒的影响.结果显示:随着热处理温度升高,玻璃表面的Ag原子逐渐向玻璃内部扩散,其表面摩尔浓度逐渐降低.提高热处理温度和延长热处理时间都有利于提高玻璃中Ag纳米颗粒的体积分数.空气中,高温热处理高掺Ag量的白玻璃样品时发生二次成核,因此,Ag纳米颗粒尺寸呈双峰分布.Ag纳米颗粒尺寸的双峰分布导致其等离子体共振吸收峰出现双峰.在氢气气氛中,在250℃热处理2min,即可在玻璃中形成大量Ag纳米颗粒,颗粒尺寸小于空气中高温热处理样品的尺寸,从而引起表面等离子体共振吸收峰发生蓝移.     

Ag-Cu双金属纳米颗粒在硅酸盐玻璃中的形成过程

利用两步离子交换结合H2气氛热处理的方法,制备出Ag-Cu双金属纳米颗粒/硅酸盐玻璃复合材料.结合吸收光谱和X射线光电子能谱研究了不同工艺条件下Ag、Cu在玻璃中的深度分布、价态变化及其玻璃网络结构的变化.结果表明:掺杂后的玻璃中银和铜的含量随深度不同有所不同.Ag+-Na+离子交换过程中,Ag+与非桥氧结合形成Si-O-Ag键,样品中的银主要以离子状态存在.H2气氛中热处理后,大部分与非桥氧相连的Ag+被还原,H+随即取代Ag+位置,与非桥氧形成-OH结构,还原出来的Ag0经成核和生长形成银纳米颗粒.第二次Cu+-Na+离子交换后,Cu+被引入硅酸盐玻璃,并有二价铜离子存在,再经过H2热处理后,铜离子被还原,在表层聚集生成铜纳米颗粒.     

铜纳米颗粒在硅酸盐玻璃中的形成及其局部结构

用离子交换结合H2气氛热处理的方法制备出铜纳米颗粒/硅酸盐玻璃复合材料.利用光学吸收谱和X射线吸收精细结构谱分析了铜纳米颗粒在玻璃中的形成机理及其局部结构.结果表明:提高H2气氛处理温度有利于提高Cu纳米颗粒在玻璃中的体积分数,在其它工艺条件相同的情况下,离子交换时间从0.5 h延长到1.0 h对cu纳米颗粒在玻璃中的体积分数影响不大.Cu在离子交换硅酸盐玻璃中仅存在Cu-O配位结构,热处理后铜原子在玻璃中存在2种局域结构环境:一是处于铜氧化物的配位环境:另一是处于金属铜的配位环境.玻璃中铜离子以-价存在,其周围存在2个氧配位,Cu-O键长在0.185～0.186 nm之间.随着Cu颗粒尺寸的降低和Cu小分子团簇质量分数的增加,Cu-Cu配位的无序度增大.含小分子铜团簇多的样品,Cu-Cu最近邻原子间距离与铜体材料中的Cu-Cu最近邻原子间距离(0.255 nm)相比发生收缩;含铜纳米颗粒较多的样品,Cu-Cu最近邻原子间距离与铜体材料中的Cu-Cu最近邻原子间距离相比发生膨胀.     

银纳米颗粒/玻璃复合材料的吸收光谱特征

利用离子交换结合热处理方法,制备出Ag纳米颗粒掺杂硅酸盐玻璃复合材料。通过改进的Mie理论拟合了不同制备条件下Ag纳米颗粒的吸收光谱,得到了它们的尺寸和体积分数。拟合结果表明:在热处理条件相同时,离子交换时间越长,样品中Ag纳米颗粒的尺寸越大,体积分数越高;在离子交换条件相同时,随着后续热处理时间的延长或温度升高,样品中Ag纳米颗粒的尺寸变大,体积分数提高。相比于空气热处理,氢气热处理可以显著降低样品中Ag纳米颗粒的形成温度和时间。氢气气氛下形成的Ag纳米颗粒小于空气气氛下形成的Ag纳米颗粒,导致其等离子体共振吸收峰相对空气中热处理的样品发生蓝移。     

用原位透射电镜技术观察微晶玻璃结晶过程的研究进展（英文）

总结了利用原位透射电子显微镜(TEM)技术观察纳米颗粒在玻璃介质中结晶过程的研究进展。原位TEM技术可以提供一个实时记录纳米颗粒形核结晶以及长大的动力学平台,该技术为理解和优化微晶玻璃中纳米颗粒生长机理提供了方法,从而为实现优化纳米颗粒结晶性、形貌以及其物理特性提供了直接途径。此外,还总结了微晶玻璃中纳米颗粒的成核机理,详细讨论了温度和电子束(E-beam)对纳米颗粒在玻璃介质中生长动力学过程的影响,并提出了原位TEM技术在微晶玻璃材料中应用的机遇和挑战。     

聚苯胺-木质素磺酸纳米复合物的制备及吸附性能

以木质素磺酸(LS)为分散剂,采用静态聚合法制备了聚苯胺-木质素磺酸(PANI-LS)纳米复合物。通过扫描电子显微镜、透射电子显微镜、红外光谱、紫外可见光谱和广角X射线衍射对纳米复合物的形貌、结构和性能进行了表征。同时,研究了该纳米复合物对银离子的吸附性能。在银离子初始浓度为0.03 mol·L^-1时,PANI-LS纳米复合物对银离子的最大吸附容量为500 mg·g^-1。对吸附后纳米复合物的透射电子显微镜和广角X射线衍射的研究表明,PANI-LS纳米复合物对银离子具有还原作用,吸附后纳米复合物表面有直径为2～7 nm的单质银纳米粒子生成。     

晶种生长法制备银纳米片:老化过程对产物的影响

晶种生长法是获得形貌尺寸可控纳米银材料的常用方法.本文采用晶种生长法制备银纳米片.通过紫外吸收光谱及透射电子显微镜研究了老化过程对产物形貌的影响;同时通过在晶种生长阶段使用不同稀释浓度的晶种溶液,验证了硼氢化钠浓度对产物的影响.结果表明,经充分老化后的晶种溶液,残留的硼氢化钠分解更充分,以此溶液作为晶种进行后续生长时,银离子在琥珀酸作用下缓慢还原并逐渐沉积到晶种上,由于晶种(111)面被柠檬酸根保护,银离子在非(111)面的优先沉积导致片状结构的生成,产物以银纳米片为主.而未经充分老化的晶种溶液中含有未完全反应的硼氢化钠,后续加入的银离子将被残留在晶种溶液中的硼氢化钠迅速还原成银颗粒,而不能缓慢沉积在晶种表面,最终产物以银纳米颗粒为主.     

植物还原法制备Au-Ag合金纳米材料及其拉曼应用

以菠萝蜜叶提取液作为保护剂和还原剂制备金银合金纳米颗粒,在333 K和363 K时制备的合金纳米颗粒的金与银的组成比分别约为3：1和1：1。采用紫外-可见分光光度法分别测定金与银纳米颗粒的成核生长动力学,温度对银的成核生长影响更加明显,在363 K时两者成核生长速度相差不到2倍,容易形成比例相当的合金纳米颗粒。对提取液中植物分子反应前后红外分析,得出333 K时有部分银离子没有完全还原而使得合金中相应含量比例较低。而组成约为1：1的合金纳米颗粒在罗丹明的检测中显示出较强的拉曼增强效应。     

植物还原法制备Au-Ag合金纳米材料及其拉曼应用

以菠萝蜜叶提取液作为保护剂和还原剂制备金银合金纳米颗粒,在333 K和363 K时制备的合金纳米颗粒的金与银的组成比分别约为3:1和1:1。采用紫外-可见分光光度法分别测定金与银纳米颗粒的成核生长动力学,温度对银的成核生长影响更加明显,在363 K时两者成核生长速度相差不到2倍,容易形成比例相当的合金纳米颗粒。对提取液中植物分子反应前后红外分析,得出333 K时有部分银离子没有完全还原而使得合金中相应含量比例较低。而组成约为1:1的合金纳米颗粒在罗丹明的检测中显示出较强的拉曼增强效应。     

电场诱导银离子扩散硅酸盐玻璃的光致发光光谱

利用直流电场诱导银离子向硅酸盐玻璃基片内部扩散,并进行后续热处理.采用透射电镜观察玻璃基片中纳米颗粒形貌,测量了样品的吸收光谱和光致发光谱.结果表明:随着对玻璃基片热处理时间的延长,吸收峰的强度有明显的增强,峰的位置稍有蓝移,并在410 nm附近出现明显的等离子共振吸收现象;玻璃基体中出现尺寸为小于10 nm的银单晶颗粒.电场诱导银离子扩散后的玻璃在277 nm与325 nm光激发下,发光峰分别在380 nm和440 nm附近,其发光强度随着电场强度的增加呈现先增大后减小的变化趋势.     

Immobilization of metal nanoparticles on polyurethane membranes: synthesis and electrical properties

Ag and Cu nanoparticles were immobilized into crosslinked polyurethane (PU) membranes by taking advantage of the swelling characteristics of the membranes. The formation, shape and size of the nanoparticles inside the post‐swollen PU membranes were observed by transmission electron microscopy and atomic force microscopy. X‐ray diffraction indicated the presence of the pure Ag and Cu embedded in the amorphous PU matrix. Because of their compatibility, the nanoparticles improved the thermal stability and increased the glass transition temperature of PU. The membranes exhibited interesting conducting behavior with increasing temperature. The metal immobilization increased the ionic conductivity which further increased with temperature, with an activation energy of 0.15 eV indicating a thermally activated conduction mechanism. The optical and electrical properties of these starch‐based membranes can be utilized in the development of novel sensors for biomedical applications. Copyright © 2012 Society of Chemical Industry     

Highly Efficient Room Temperature Synthesis of Silver‐Doped Zinc Oxide (ZnO:Ag) Nanoparticles: Structural,Optical, and Photocatalytic Properties

Synthesis of silver‐doped zinc oxide (ZnO:Ag) nanoparticles through precipitation method has been reported. The synthesis was conducted at room temperature and no subsequent thermal treatment was applied. ZnO nanoparticles were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), fourier transmission infrared spectroscopy (FTIR), and ultraviolet‐visible (UV–Vis) spectroscopy. Detailed crystallographic investigation was accomplished through Rietveld refinement. The effect of silver content on structural and optical properties of resultant ZnO nanoparticles has been reported. It was found that silver doping results in positional shifts for the XRD peaks and the absorption band edge of ZnO. These were attributed to the substitutional incorporation of Ag⁺ ions into Zn²⁺ sites within the ZnO crystal. In addition, higher silver incorporation resulted in smaller size for ZnO nanoparticles. The photocatalytic activity of the ZnO:Ag nanoparticles was also determined by methylene orange (MO) degradation studies and compared to that of undoped ZnO. Improved photocatalytic activity was obtained for ZnO:Ag nanoparticles. It has been shown that an optimum amount of silver dopant is required to obtain maximum photocatalytic activity.     

Interfacial heterogeneous precipitation of Ag nanoparticles in soda-lime silicate glass for improved toughness and conductivity

The fracture toughness and thermal conductivity of soda-lime glass were enhanced by an interfacial precipitation of Ag. Large quantities of silver nanoparticles (AgNPs) are formed on the surface and subsurface layers of the Ag–Na ion exchanged glass powders during the heat-treatment in H₂ for various times, and are fully densified by subsequent spark plasma sintering (SPS). The AgNPs with particle sizes above 50 nm are mainly located near the interfaces with the original glass particles, whereas smaller AgNPs are observed inside the glass particles. Moreover, the thickness of the precipitated Ag layer is seen to increase with increasing heat-treatment time. The incorporation of AgNPs is shown to enhance the fracture toughness of the soda-lime glass due to ductile deformation, crack deflection, and crack bridging. Finally, a maximum fracture toughness of 1.14 MPa m^1/2, and a maximum thermal conductivity of 1.20 W m^?1K^?1, are obtained for the glass powders that were subjected to the entire process of ion-exchange, heat-treatment, and SPS densification.     

Silver/polystyrene nanocomposites: Optical and thermal properties

Nanocomposites consisted of different quantities of silver (Ag) nanoparticles incorporated in a polystyrene (PS) matrix have been prepared by solution mixing method. Transmission electron microscopy was applied to determine the size distribution of the Ag nanoparticles, while the morphology of fractured surfaces of pure PS and Ag/PS nanocomposites was examined by scanning electron microscopy. Absorption spectra of nanocomposites were compared with theoretically calculated spectra based on the Maxwell‐Garnett effective medium theory. The influence of Ag content on thermal properties of Ag/PS nanocomposites was investigated by thermogravimetric analysis and differential scanning calorimetry. Thermal and thermo‐oxidative stability of the host polymer were improved by introduction of silver nanoparticles. The glass transition temperature of the prepared Ag/PS nanocomposites was lower in comparison with the neat PS and decreased with the increase of the Ag content due to the very weak interfacial interaction between Ag nanoparticles and polymer matrix. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Zirconia gradation and thermal expansion compatibility between infiltration glass and antimicrobial glass

This study evaluated an infiltration glass over zirconia in order to form a graded layer with thermal expansion coefficient compatibility and antimicrobial capacity. 210 discs of 3Y-TZP were polished and divided into groups: YZ sintered (Sintered), YZ glazed (Glaze), YZ + Ag 5% (Ag 5%), YZ + Ag 4% (Ag 4%), YZ glass infiltrated (INF.), YZ glass infiltrated + Ag 5% (INF. + Ag 5%) and YZ glass infiltrated + Ag 4% (INF. + Ag 4%). Analyzes of biaxial flexural strength, X-ray diffraction (XRD), EDS, translucency, scanning electron microscopy (SEM) and fractographic were performed. The biofilm was quantified by counting the colony forming units (CFU/mL) of S. mutans. Strength values (MPa), translucency and CFU data were analyzed by one-way ANOVA and Tukey's test (α = 0.05). Weibull analysis was performed to calculate the material's modulus (m) and characteristic strength (95% CI). Infiltrated zirconia glass (INF.: 1149.7; INF. + Ag 4%: 928.2; INF. + Ag 5%: 791.5), sintered (819.0) or glazed (790.8) showed higher flexural strength (MPa) than silver-doped soda-lime glass zirconia without infiltration glass (Ag 5%: 612.1; Ag 4%: 519.2). Diffractograms showed combeite crystals in INF. + Ag 4%/5%. EDS analysis of Ag 5% group showed the higher quantity of silver when compared to INF. + Ag 5% group. Silver-doped soda-lime glass did not affect the translucency, while infiltration glass decreased the values. SEM showed irregularities on the surface of the silver-doped soda-lime glass groups and a smooth surface on the glass and glaze groups. Fracture origin of all groups was in the glaze layer and silver-doped soda-lime glass, while it was inside the zirconia in the INF. group. Lowest colony growth was observed in the Ag 5%. Glass-infiltrated zirconia showed greater strength, while Ag 5% presented greater antimicrobial capacity. The application of silver-doped soda-lime glass did not influence zirconia translucency, while glass infiltration decreased it.     

Mixed-Alkali Effect and Interdiffusion of Na and K Ions in Glass

When 2 alkali ions are present in a glass, its electrical conductivity is reduced compared to that of glasses containing only one of these ions. Measurements of electrical mobility and tracer diffusion show that the mobilities of individual ions are reduced by the presence of a second ion. Thus, theories have been proposed to explain the mixed-alkali effect in terms of ionic interactions. However, experiments on interdiffusion of Na and Ag or K ions in soda-lime glass indicate that at sufficiently low temperatures the mobilities of the interdiffusing ions are not influenced by the presence of the second ion. Therefore, it is postulated that structural rearrangement of the glass is required for the mixed-alkali effect.     

Luminescence Enhancement of CdS Quantum Dots in Glass by Ag+ Ion Exchange

Luminescence of CdS quantum dots (QDs) enhanced by the induction of Ag nanoparticles (NPs) in glasses was investigated. Ag⁺ ions diffused into glasses containing CdS QDs by ion exchange, then formed Ag NPs after subsequent heat treatment. Luminescence intensity of CdS QDs increased approximately three times when the ion‐exchange duration was 1 min, but was severely quenched when the duration was extended to 30 min. Increasing the amount of Ag⁺ ions increased the number of Ag NPs and decreased the average distance between Ag NPs and CdS QDs. This decrease in the average distance induced the changes of luminescence intensity.     

Small AgNP in the Biopolymer Nanocomposite System

In this work, ultra-small and stable silver nanoparticles (AgNP) on chitosan biopolymer (BP/AgP) were prepared by in situ reduction of the diamminesilver(I) complex ([Ag(NH₃)₂]⁺) to create a biostatic membrane system. The small AgNP (3 nm) as a stable source of silver ions, their crystal form, and homogeneous distribution in the whole solid membrane were confirmed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The X-ray photoelectron spectroscopy (XPS) and Auger analysis were applied to investigate the elemental composition, concentration, and chemical state of surface atoms. It was found that ultra-small metallic nanoparticles might form a steady source of silver ions and enhance the biostatic properties of solid membranes. Ultra-small AgNP with disturbed electronic structure and plasmonic properties may generate interaction between amine groups of the biopolymer for improving the homogeneity of the nanometallic layer. In this work, the significant differences between the typical way (deposition of ex-situ-prepared AgNP) and the proposed in-situ synthesis approach were determined. The improved thermal stability (by thermogravimetry and differential scanning calorimetry (TG/DSC) analysis) for BP/AgP was observed and explained by the presence of the protective layer of a low-molecular silver phase. Finally, the antibacterial activity of the BP/AgP nanocomposite was tested using selected bacteria biofilms. The grafted membrane showed clear inhibition properties by destruction and multiple damages of bacteria cells. The possible mechanisms of biocidal activity were discussed, and the investigation of the AgNP influence on the bacteria body was illustrated by AFM measurements. The results obtained concluded that the biopolymer membrane properties were significantly improved by the integration with ultra-small Ag nanoparticles, which added value to its applications as a biostatic membrane system for filtration and separation issues.