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.

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.

Design of advanced porous silver powder with high-sintering activity to improve silicon solar cells

Silver(Ag)paste is widely used in semiconductor metallization,especially in silicon solar cells.Ag powder is the material with the highest proportion in Ag paste.The morphology and structure of Ag powder are crucial which determine its characteristics,especially for the sintering activity.In this work,a simple method was developed to synthesize a type of microcrystalline spherical Ag particles(SP-A)with internal pores and the structural changes and sintering behavior were thoroughly studied by combining ultra-small-angle X-ray scattering(USAXS),small-angle X-ray scattering(SAXS),in-situ heating X-ray diffraction(XRD),focused ion beam(FIB),and thermal analysis measurement.Due to the unique internal pores,the grain size of SP-A is smaller,and the coefficient of thermal expansion(CTE)is higher than that of traditional solid Ag particles.As a result,the sintering activity of SP-A is excellent,which can form a denser sintered body and form silver nanoparticles at the Ag–Si interface to improve silver silicon contact.Polycrystalline silicon solar cell built with SP-A obtained a low series resistance(Rs)and a high photoelectric conversion efficiency(PCE)of 19.26%.These fill a gap in Ag particle structure research,which is significant for the development of high-performance electronic Ag particles and efficient semiconductor devices.

化学还原法制备纳米银粉及性能表征

在低温反应条件下,通过化学还原的方法以双氧水还原银氨配离子,制备了Ag纳米粉,并利用X射线衍射(XRD)、透射电子显微镜(TEM)对样品的成分、形貌、晶体结构、粒度及其分布进行性能表征;用红外吸收光谱(FT-IR)对结构组成进行定性分析;采用热失重分析(TGA)和差示扫描量热分析(DSC)研究了在热处理过程中的物相转变。结果表明:在所选择的实验条件下制备了类球形分布、分散性好的Ag纳米颗粒,其粒径主要分布在10￣50nm范围,平均粒径为26nm,晶体结构与相应的块体材料基本相同,为fcc结构,样品具有很强的吸附性。

纳米银粉在水溶液中的分散及粒径表征

利用直流电弧等离子体蒸发冷凝法制备纳米银粉,采用X射线衍射分析对纳米银粉的结构进行表征,采用纳米激光粒度仪研究不同超声分散工艺与不同离子类型的分散剂聚乙烯吡咯烷酮、十六烷基三甲基溴化氨、十二烷基硫酸钠对纳米银粉在水溶液中分散性能的影响,获得纳米银粉的最佳分散工艺与激光粒径分布,对比研究纳米银粉的激光粒径与透射电镜统计的粒径的差异。结果表明:纳米银颗粒为立方晶系多晶体,颗粒的结晶性良好;以十六烷基三甲基溴化氨为分散剂的效果最理想,最佳超声波功率为600 W;当十六烷基三甲基溴化氨的质量浓度为0.5 g/L时,纳米银颗粒的分散稳定性较好;激光粒径反映的纳米颗粒的动态二次粒径略大于从透射电镜图像统计得到的粒径。

Antibiotic-loaded amphora-shaped pores on a titanium implant surface enhance osteointegration and prevent infections

Artificial prostheses for joint replacement are indispensable in orthopedic surgery.Unfortunately,the implanted surface is attractive to not only host cells but also bacteria.To enable better osteointegration,a mechanically stable porous structure was created on a titanium surface using laser treatment and metallic silver particles were embedded in a hydrophilic titanium oxide layer on top.The laser structuring resulted in unique amphora-shaped pores.Due to their hydrophilic surface conditions and capillary forces,the pores can be loaded preoperative with the antibiotic of choice/need,such as gentamicin.Cytotoxicity and differentiation assays with primary human osteoblast-like cells revealed no negative effect of the surface modification with or without gentamicin loading.An in vivo biocompatibility study showed significantly enhanced osteointegration as measured by push-out testing and histomorphometry 56 days after the implantation of the K-wires into rat femora.Using a S.aureus infection model,the porous,silver-coated K-wires slightly reduced the signs of bone destruction,while the wires were still colonized after 28 days.Loading the amphora-shaped pores with gentamicin significantly reduced the histopathological signs of bone destruction and no bacteria were detected on the wires.Taken together,this novel surface modification can be applied to new or established orthopedic implants.It enables preoperative loading with the antibiotic of choice/need without further equipment or post-coating,and supports osteointegration without a negative effect of the released dug,such as gentamicin.