Luminescence intensification of lanthanide complexes by silver nanoparticles incorporated in sol-gel matrix

We present how the luminescence of europium RR-2-P-oxides complexes can be increased by interaction of electronic levels of the complex with the radiation field of silver nanoparticles （NPs）. The procedure by which silver NPs are formed in a sol-gel polyurethane matrix precursor was elaborated. The formed Ag NPs were combined with Eu complex incorporated in ormocer matrix. The emission spectra of the complexes without silver NPs were compared with spectra of the same complexes with addition of silver NPs. As the result of the interaction of the electronic levels of lanthaaide ligands with silver plasmons, dramatic increase of luminescence was observed.

On the fluorescence enhancement mechanism of Er^(3+) in germanate glass containing silver particles

The spectral properties of trivalent erbium ions（Er^3＋） are systematically studied in a melt-quenched germanate glass（60 GeO2-20PbO-10BaO-10K2O-0.1Ag2O） containing silver（Ag） particles.Thermal treatment of the material leads to the precipitation of Ag particles as observed by transmission electron microscopy and confirmed by absorption spectrum for the obvious surface plasmon resonance peak of Ag particles.The fluorescence from Er^3＋ in the 10-min-annealed sample with Ag particles is found to be 4.2 times enhanced compared with the unannealed sample excited by 488-nm Ar＋ laser.A comparison is made between a spectral study performed on the unannealed Er^3＋-doped sample and the one annealed for 20 min.The data of absorption cross section and Judd-Ofelt intensity parameters show the agreement between the two samples no matter whether there are Ag particles,indicating that the introduction of Ag particles by post-heat treatment has no effect on the crystal field environment of Er^3＋ ions.The fluorescence enhancement is attributed to the surface plasmon oscillations of Ag particles in germanate glass.

The Role of PVP for Preparation of Size-controllable Silver Nanoparticles

In this work,silver nanoparticles were successfully.The particles were characterized by Transmission electron microscope,UV-visible spectroscopy,particle size analyzer.The results show that particles were about 35nm,and ratio between PVP and AgNO3was the key factors of the synthesis process,which can affect the size and shape of silver nanoparticles.The work implied that the method can also be suitable to fabricate other metal nanostructures.

Highly Conductive Fractal-structured Silver Particles for Preparing Flexible Printed Circuits via Screen Printing

Fractal-structured silver particles(FSSPs)are conductive materials with a micron-scale trunk and nanoscale branches,and are characterized with high electrical conductivity and high connectivity.In this study,FSSPs were added to an aqueous additive solution for synthesizing a conductive ink,which was used to prepare two types of printing electrodes via screen printing.The first type included two flexible printed electrodes(FPEs):an FPE on a polyethylene terephthalate(PET)film and an FPE on paper.The second one was a polydimethylsiloxane(PDMS)-embedded FPE.The PETbased FPE exhibited high electrochemical stability when its sheet resistance was 0.38Ω/sq for a 50%(w/w)content of FSSPs in the prepared conductive ink.Moreover,the embedded FPE demonstrated excellent mechanical properties and high chemical stability.In addition,the embedded structure was endowed with stretchability,which is important for different devices,such as flexible biomedical sensors and flexible electronics.

Production of nanocrystalline silver particles by hydrogen reduction of silver nitrate aerosol droplets

Nanocrystalline silver particles were produced by hydrogen reduction of silver nitrate aerosol droplets formed by high frequency ultrasonic generator.The dependences of the particle size,morphology and crystallite size on the precursor concentration and the reaction temperature were investigated.Ultrasonic spray pyrolysis process was combined with hydrogen reduction to research the effects on the silver particle production.Nanocrystalline silver particles including slight oxide structure were prepared at temperature as low as 200 ℃ from silver nitrate under hydrogen atmosphere.X-ray diffraction（XRD） studies showed that pure silver particles were obtained above 200 ℃ reaction temperature.The crystallite sizes of the samples ranged from 29 to 47 nm.The results indicate that the crystallite sizes hardly ever depended on the reaction temperature.Crystallites slightly enlarged by increasing precursor concentration.SEM observations showed that particles were obtained in spherical morphology with particle sizes between 210 and 525 nm.Reaction temperature and precursor concentration strongly influenced the particle size.

Removal of Stabilized Silver Nanoparticles from Surface Water by Conventional Treatment Processes

Engineered nanomaterials are used in many applications, including pollution sensors, photovoltaics, medical imaging, drug delivery and environmental remediation. Due to their numerous applications, silver nanoparticles (Ag NPs) are receiving a large amount of attention. Ag NPs may occur in drinking water sources either during manufacturing, consumption and/or disposal processes. This potentially leads to the presence of Ag NPs in finished drinking water, which could have public health impacts. The objective of this research was to investigate the removal of several types of stabilized Ag NPs by potable water treatment processes. Specifically, this research achieved these objectives through: 1) Synthesis of Citrate-reduced Ag NPs, Polyvinylpyrrolidone stabilized (PVP) Ag NPs and Branched polyethyleneimine stabilized (BPEI) Ag NPs, 2) Characterization of synthesized Ag NPs to determine their aggregation potential, Zeta potential profiles, (pHpzc) and obtain morphological data from SEM images, and 3) An evaluation of the efficacy of conventional water treatment processes (i.e., coagulation, flocculation, sedimentation and sand filtration) in removing stabilized Ag NPs from natural water. The three NPs were found to be stable at the nano size in natural water. Alum coagulation had no impact on the PVP and BPEI Ag NPs. Flocculation and settling were found to be key steps for removal of these NPs. The three Ag NPs were not permanently removed by means of conventional water treatment processes employed in this study.

Impact of Sulfidation of Silver Nanoparticles on Established<i>P. aeruginosa Biofilm</i>

Silver nanoparticles (Ag-NPs), one of the most common types of nanomaterials in medical fields and consumer products, are known to have antimicrobial effects;these materials also undergo a series of chemical and biological transformations in the environment. Although the pristine form of silver nanoparticles has been studied, less is known about the impacts of the transformed Ag-NPs on biological systems. This knowledge gap hinders the progress of effectively assessing the impacts of Ag-NPs on the environment and human health. In this study, we demonstrate that the most common form of transformed Ag-NPs, sulfidized silver nano-particles (Ag2S-NPs), show less damage on established Pseudomonas aeruginosa GFP (ATCC? 10145 GFP?) biofilm than the pristine form of the nanoparticle. At a dosage of 0.625 mg/L, the total biomass in the biofilm decreased 64% after being exposed to Ag-NPs and 44% after exposure to Ag2S-NPs. Live biofilms were also interrogated. We observed high reduction in live population for biofilm exposed to Ag-NPs and relatively low reduction by Ag2S-NPs at exposure concentrations higher than 0.625 mg/L. Compared with Ag-NPs, the lower solubility of Ag2S-NPs results in less Ag+ diffusion into established biofilms. Our results suggest that the sulfidation of Ag-NPs reduces their impacts on established biofilms, indicating that the transformed Ag-NPs may have less environmental or human health risks.

Temperature Dependent Surface Resistivity Measures of Commercial, Multiwall Carbon Nanotubes (MWCNT), and Silver Nano-Particle Doped Polyvinyl Alcohol (PVA) Films

Pure and doped Polyvinylidene difluoride (PVDF) films, for the detection of infrared radiation, have been well documented using the mechanism of pyroelectricity. Alternatively, the electrical properties of films made from Polyvinyl Alcohol (PVA) have received considerable attention in recent years. The investigation of surface resistivities of both such films, to this point, has received far less consideration in comparison to pyroelectric effects. In this research, we report temperature dependent surface resistivity measurements of commercial, and of multiwall carbon nanotubes (MWCNT), or Ag-nanoparticle doped PVA films. Without any variation in the temperature range from 22°C to 40°C with controlled humidity, we found that the surface resistivity decreases initially, reaches a minimum, but rises steadily as the temperature continues to increase. This research was conducted with the combined instrumentation of the Keithley Model 6517 Electrometer and Keithley Model 8009 resistivity test fixture using both commercial and in-house produced organic thin films. With the objective to quantify the suitability of PVDF and PVA films as IR detector materials, when using the surface resistivity phenomenon, instead of or in addition to the pyroelectricity, surface resistivity measurements are reported when considering bolometry. We found that the surface resistivity measurements on PVA films were readily implemented.

Silver Hollow Microspheres: Large-scale Synthesis, Characterization and Electromagnetic Shielding Property

A facile and large-scale synthesis method to fabricate silver hollow microspheres with controllable morphologies and shell thickness is described using low-cost glass microspheres as templates. The method mainly involves two steps of the preparation of silver-coated glass microsphere core–shell particles by a controllable liquid reduced reaction of Ag[（NH3）2]＋ solution, which only produces silver nanoparticles anchored on the surface of the thiolated glass microsphere templates, and the removal of glass microspheres by wet chemical etching with HF solution. The products are well characterized by field emitted scanning electron microscopy （SEM）, transmitted electron microscopy （TEM）, X-ray photoelectron spectra （XPS）, X-ray diffraction （XRD） and energy dispersive X-ray （EDX） etc. The as-prepared core-shell particles and hollow particles have even and compact silver shells. The electromagnetic shielding coatings based on the silver hollow microspheres are demonstrated to have high conductivity, excellent shielding effectiveness and long durability, suggesting that the silver hollow microspheres obtained here are a novel light-weight electromagnetic shielding filler and will have extensive applications in the electromagnetic compatibility fields.

Application of Nanogold Probe Coupled with Silver Enhancement in Rapid cTnI Colorimetric Immunoassay

A rapid, inexpensive, reliable, and flexible quantitative immunoassay for cardiac troponin I （cTnI） based on the concepts of one-step dual monoclonal antibody “sandwich” principle. The low density protein array, the nanogold probe, and the silver enhancement on the gold particle were provided. The whole detection procedure of the assay could be fulfilled within 40 min with the pretreated colloidal gold-labeled detection antibody and supporting substrate. The assay showed good specific response to cTnI with very low cross-reactivity ratio to the skeletal isoforms of troponin I （sTnI）, cardiac troponin T （cTnT）, and myoglobin. 588 serum samples were assayed simultaneously by enzyme-linked immuno sorbent assay （ELISA） and this colloidal gold method to test the validity of the method and the data were analyzed using the statistical package SPSS version 11.0 （SPSS Inc.）. There was no significant difference between these two assays （P=0.66〉0.05）. The agreement between this method （〉 or 〈0.3 ng/mL） and ELISA was 86%.

Silver removal from molten lead through zinc powder injection

A silver removal process was carried out on a Pb-Ag alloy through zinc powder injection of three different sizes （3.55, 44.4 and 734.8μm） with a top submerged lance using nitrogen as carrying gas. The higher silver removal was obtained for the zinc powder size of 44.4μm, while the lowest silver removal efficiency was attained for the smaller particle size. The AgZn phase was detected in the slag for the 44.4 and 734.8μm particle sizes by XRD, which was in agreement with SEM-EDS analysis. Experimental behavior was explained according to the melting and residence time of the injected particles.

Cluster-Associate Model of Viscosity of Silver Chloridein Comparison with Frenkel Model

The purpose of the research is to develop the temperature dependence of the dynamic viscosity for silver chloride. The data were calculated on the basis of a new cluster and associate equation, which was derived using the concept of randomized particles. The calculated data are given in the temperature range from the melting point to the boiling point. The cluster and associate model is compared with the Frenkel’s equation in logarithmic coordinates, showing the mutual correspondence and complementarity of these models.

基于无颗粒银导电墨水在不锈钢表面镀银工艺研究

目的采用无颗粒银导电墨水对不锈钢表面进行镀银研究,以绿色环保工艺替代传统电镀银技术。方法主要研究适用于不锈钢基材的前驱体银源、络合剂种类、不锈钢前处理方法、烧结固化温度对不锈钢表面银层微观结构及性能的影响,获得不锈钢基材上微观结构致密、性能良好的银层。采用X射线衍射仪、扫描电子显微镜、激光共聚焦显微镜、数字兆欧表对在不锈钢表面银膜层进行表征。结果不锈钢通过1,2丙二胺溶液处理后,采用银源草酸银为前驱体,此时银层微观结构最致密,具有最佳的附着力等级(5B)和最低的粗糙度(1.237μm),与1,2-丙二胺络合,乙醇为溶剂时,制备出的银层有机物挥发完全,微观结构致密,并且具有最低的接触电阻0.7Ω和粗糙度0.80μm。烧结固化温度为200℃时银层导电性最好。结论采用无颗粒银导电墨水对不锈钢表面进行镀银的新型工艺银层性能良好,可以简化传统电镀技术复杂的操作流程,减少传统电镀工艺所使用氰化物对人体造成的危害,并弥补应用受限的缺点。

亚微米银焊膏的低温无压烧结性能研究

烧结银焊膏具备高导热、高导电、低弹性模量和高可靠性等优异性能,可以最大程度地发挥出SiC和GaN器件的潜能,因此具有广阔的应用前景.为了降低银焊膏的制备成本,同时改善银焊膏的烧结性能,使用球形和片状两种亚微米银颗粒制备了3种烧结银焊膏,通过分析银焊膏在200~250℃低温无压烧结后的电阻率、剪切强度和微观形貌,研究了不同形貌亚微米银颗粒及混合颗粒的低温无压烧结性能.研究表明:球形银颗粒制备的银焊膏在250℃烧结后,具有52.4 MPa的高剪切强度,同时其电阻率仅为6.28×10^(-8)Ω·m;银片制备的银焊膏烧结后的剪切强度始终较低且电阻率始终较大,在250℃烧结后,剪切强度为21.5 MPa,电阻率为15.54×10^(-8)Ω·m,这归因于银片的径向尺寸较大、振实密度较低和银片层层堆叠的烧结结构;混合颗粒的银焊膏展现出了在更低温度下烧结的潜力,在200℃烧结后,剪切强度为28.2 MPa,电阻率为7.77×10^(-8)Ω·m,这得益于银片可促进所选有机组分更早地去除和混合颗粒具有更高的初始堆积密度.本文研究成果有助于亚微米银颗粒焊膏的成熟稳定制备,也为低温无压烧结的高性能银焊膏的研发提供了新的思路.

热处理对银包铜粉表面光滑度的影响

为解决银包铜粉在导电浆料中的应用问题,本文采用化学镀与浸涂法结合制备银包铜粉,通过控制热处理工艺来改善镀银层表面的平整光滑性,并利用扫描电镜、电阻测试仪等研究了热处理工艺对银包铜粉镀银层形貌、抗氧化性、导电性和吸油率的影响。研究发现:采用化学镀与浸涂法结合的方法,可以制备表面更光滑的银包铜粉;随着热处理温度的升高,银层愈加光滑平整;但当热处理温度为700℃时,银包铜粉会出现破裂团聚的现象,且随着热处理时间的延长,银包铜粉结构发生畸变和团聚。研究表明,控制热处理工艺可以改善银层表面平整光滑性,从而降低其在电子浆料中的吸油率,提高抗氧化性和导电性。当热处理温度为600℃,保温时间10 min时,制备得到的银包铜粉形貌最好,综合性能最佳。

非水溶液体系中晶种法制备球形银纳米颗粒

以丙三醇作溶剂,硝酸银为原料,聚乙烯吡咯烷酮(PVP)为分散剂,硼氢化钠为还原剂制备了银纳米晶种;以此银纳米粒子作为初级晶种,以丙三醇作溶剂和还原剂,通过升温提高丙三醇的还原性制备银纳米颗粒。研究分散剂种类、生长液银浓度、晶种加入量对银粉的影响,采用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)对制备产物的结构、物相、形貌进行表征。结果表明,通过改变条件可以制备出分散性良好、粒径均匀的70nm左右的球形银粉。

Pb-PL/AgNPs复合阳极的制备及电化学性能

Pb-Ag阳极是锌电积中目前最常用的不溶性阳极,但其存在析氧电位高和耐腐蚀性差等问题。本文通过木质素磷酸化改性并在其表面负载纳米银颗粒,制备了磷酸化木质素/纳米银复合材料(PL/AgNPs),采用场发射扫描电子显微镜(FESEM)、傅立叶变换红外光谱法(FTIR)、X射线光电子能谱测试(XPS)、热重分析(TGA)对PL/AgNPs的微观形貌、结构组成、银含量进行分析。采用粉末冶金和机械合金化技术制备出Pb-PL/AgNPs复合阳极,在模拟锌电积条件下,采用循环伏安法(CV)、线性扫描伏安法(LSV)、电化学阻抗谱分析法(EIS)等对Pb-PL/AgNPs复合阳极的电化学性能和耐腐蚀性能进行分析。结果表明:Pb-0.5%PL/AgNPs复合阳极具有最佳的电化学和耐腐蚀性能,其银的用量较Pb-0.75%Ag阳极减少了96.7%。Pb-0.5%PL/AgNPs复合阳极的伏安电荷量为1.0611 C/cm^(2),分别是纯Pb阳极和Pb-Ag阳极的1.8倍和1.25倍;其析氧稳态电位为1.436 V,比纯Pb阳极和Pb-Ag阳极分别低194 mV和97 mV;其耐腐蚀性比纯Pb阳极和Pb-Ag阳极分别提升约86.8%和84%。

低温烧结无颗粒型银导电墨水的制备及其性能研究

导电墨水是柔性印制电子发展的关键,然而,目前导电墨水的烧结温度仍较高,限制了其在某些柔性基材上的使用。本文以乙酸银作为前驱体、氨水为络合剂、乙醇为助剂、甲酸为还原剂,制备了一种可低温烧结的无颗粒型银导电墨水。将该导电墨水滴涂到PET基材后于烘箱中进行烧结成银膜,采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、傅里叶红外光谱仪(FTIR)等测试设备对制备的导电墨水和薄膜进行表征。系统研究了还原剂甲酸以及助剂乙醇对导电墨水及薄膜的性能影响。结果表明,该导电墨水具备良好的稳定性,经过90℃低温烧结60 min,其电阻率为11.83μΩ·cm。通过调控墨水配方,银薄膜的粗糙度和均匀性得到显著改善,且薄膜具有良好的弯折性能。

太阳能电池用球形银颗粒的液相法制备研究

本工作以硝酸银为银前驱体,抗坏血酸为还原剂,结合表面活性剂的作用,制备了平均粒径为(1.88±0.25)μm的球形银颗粒,同时,研究了还原体系中表面活性剂对银颗粒形貌及尺寸分布的影响,结果表明,柠檬酸三钠能够促进片状纳米银的形成。片状纳米银在长链表面活性剂(阿拉伯树胶、聚乙烯吡咯烷酮、聚乙二醇4000的质量比为4∶1∶1)存在时能够发生有序的自组装,得到表面相对光滑、粒径分布均匀的高球形度银颗粒。抗坏血酸的还原能力随着pH值的增加而逐渐增强。此外,本工作将所得银颗粒与有机载体及玻璃粉混合,通过丝网印刷于硅基底上,850℃烧结后,得到电阻率为3.11μΩ·cm的导电厚膜。

纳米银的制备及其负载化应用

纳米银是一种纳米级别的银粒子,具有微小的尺寸、大比表面积以及较强的化学反应活性和优异的抗菌性能,可以广泛应用于医疗、食品、环境等领域。纳米银粒子的制备方法包括化学还原法、气相沉积法、溶胶-凝胶法、电化学法、生物还原法、植物还原法等。综述了纳米银的制备方式以及负载化应用,生物法制备是一种绿色环保高效的方法,纳米银的形貌可控是下一步的研究重点。