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.

Cyanide-free silver electroplating process in thiosulfate bath and microstructure analysis of Ag coatings

Cyanide-free silver electroplating was conducted in thiosulfate baths containing AgNO3 and AgBr major salts, respectively. The effects of major salt content and current density on surface quality, deposition rate and microhardness of Ag coatings were investigated. The optimized electroplating parameters were established. The adhesion strength of Ag coating on Cu substrate was evaluated and the grain size of Ag coating was measured under optimized electroplating parameters. The optimized AgNO3 content is 40 g/L with current density of 0.25 A/dm2. The deposited bright, smooth, and well adhered Ag coating had nanocrystalline grains with mean size of 35 nm. The optimized AgBr content was 30 g/L with current density of 0.20 A/dm2. The resultant Ag coating had nanocrystalline grains with mean size of 55 nm. Compared with the bath containing AgBr main salt, the bath containing AgNO3 main salt had a wider current density range, and corresponding Ag coating had a higher microhardness and a smaller grain size.

Size and crystallinity effect on the ultrafast optical response of chemically synthesized silver nanoparticles

The excited localized surface plasmon(LSP)in metallic nanoparticles is known to relax through several processes such as electron-electron scattering,electron-phonon coupling,and phonon-phonon scat-tering.In the current research,the ultrafast electron-phonon(e-ph)coupling relaxation processes for different average sizes and crystallinity of chemically synthesized silver nanoparticles were evaluated utilizing transient absorption spectroscopy.The nanoparticle size and crystallinity of similar linear dimension polycrystalline spherical and monocrystalline cubic nanoparticles ranging from ca.30-60 nm was related to their electron relaxation time constants and revealed very different dependencies.For the monocrystalline nanocubes,the electron-phonon coupling was not dependent on the cube edge length,while for the polycrystalline nanospheres,it was linearly decreasing with diameter.We demonstrate that the e-ph coupling time constant could be used to evaluate crystallinity and crystallite size in plasmonic metal nanoparticles when the size(surface area)of the nanoparticle is known.

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.

Preparation of Highly Concentrated Silver Nanoparticles in Reverse Micelles of Sucrose Fatty Acid Esters through Solid-Liquid Extraction Method

Silver nanoparticles were synthesized in reverse micelles consisting of sucrose fatty acid esters by dissolving reactant powder in the water pool of reverse micelles through the solid-liquid extraction. Silver nanoparticles having various sizes and shapes were obtained at high concentration. The size of silver nanoparticles was controlled by reaction temperature. Moreover, the size of silver nanoparticles was dependent upon the average esterification degree of sucrose fatty acid esters forming reverse micelles. The wavelength in the peaks, which corresponded upon the localized surface plasmon resonance of resultant silver nanoparticles, was correlated with their sizes.

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.

Preparation of Micron Co₃O₄by Liquid-Phase Precipitation

Co3O4 powder has a wide range of applications in the fields of catalysts, magnetic materials and electrochemistry. Especially after the 1990s, the demand for lithium ion battery industry has grown tremendously. The traditional wet preparation of Co3O4 powder cannot meet the requirements of the battery industry. Exploring suitable methods and theories for controlling particle size and morphology is of great significance for the preparation of battery-grade Co3O4 powder. CoCl2 was used as the cobalt source, NH4HCO3 was used as the precipitant, and the precursor was prepared and further calcined to obtain Co3O4 powder. The results show that the molar ratio is the main factor affecting the precursor phase in the preparation of Co3O4 in CoCl2-NH4HCO3 system. The suitable process conditions for the system are a molar ratio of NH4HCO3 to CoCl2 of 4.5:1, a concentration of CoCl2 of 13 g/L, a reaction temperature of 600C, and a reaction time of 10 hours. The median diameter of Co3O4 prepared by the reaction conditions is about 9 μm.

Surface Plasmon Spectroscopic Study on Morphology Tuning and Oxidation Monitoring of Silver Nanoparticles

Silver nanoparticles(Ag NPs)have attracted enormous attention since they open up exciting applications in the fields of waveguides,chemical/biological sensors,molecular rulers and surface enhanced Raman scattering(SERS).All of these applications are based on localized surface plasmon resonance(LSPR).Previous extensive studies have shown that LSPR is highly sensitive to the nanoparticle composition,size,shape,and dielectric environment[1].Hence,the LSPR resonance wavelength is highly tunable over a wide range by changing only the size and shape of the nanoparticle.In another word,the surface plasmon spectroscopy of metal NPs can in turn examine the changes of its morphology.Here,we tuned the morphology of Ag NPs by oxygen plasma pretreatment of polymer substrates.Then the Ag NPs were prepared with physical sputtering deposition.In addition,we present a study to demonstrate that the oxidation of Ag NPs is monitored in real-time by using surface plasmon spectroscopy[2].

Stachytarpheta cayennensis Aqueous Extract,a New Bioreactor towards Silver Nanoparticles for Biomedical Applications

This study reports the preparation and characterization of silver nanoparticles synthesized by the mediation of the plant weed Stachytarpheta cayennensis through solution method. Ultraviolet visible spectroscopy (UV-Vis) determines the presence of nanoparticles in the solution. Infrared spectroscopy (IR) proves organic molecules at the particles interface. Powder X-ray diffraction (PXRD) provides phase composition and crystallinity. Shape was showed by scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) demonstrated the elemental mapping of the silver nanoparticles. Hydrogen peroxide scavenging and phosphomolybdenum antioxidant assays, egg albumin denaturation anti-inflammation study, and the formation mechanism complete the study. The particles have been found composed of pure silver Ag and silver chloride AgCl nanocrystallites. The average crystallite sizes were found to be 13 nm and 20 nm for Ag and AgCl respectively. A Rietveld refinement based XRD pattern data followed by Williamson-Hall plot allows a size and strain analysis. Based on SEM, spherical agglomerates materials were formed and EDX proved the presence of Cl- ions. The reaction formation mechanism of Ag and AgCl is proposed to be simultaneous and competitive. The silver nanoparticles moderately inhibit the denaturation of egg albumin and exhibit antioxidant action;hence, the nanoparticles could be considered as a potential source for biomedical applications.

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。

用于人体运动监测的微球结构柔性压力传感器

针对微结构柔性压力传感器的工艺复杂和高灵敏度压力区间小等问题,本文提出了一种基于微米(μm)级金属铜(Cu)微球结构的柔性可穿戴式压力传感器,用于人体运动信号的个性化监测。该传感器利用Cu微球的高导电性及其丰富的表面形态在硅胶表面构造了一层独特的摩擦结构,与聚对苯二甲酸乙二醇酯(PET)薄膜进行摩擦,增大了摩擦系数,提高了灵敏度和稳定性。柔性材料的应用使其能够适应人体皮肤曲面,实现高效的压力检测。该传感器具有28.7 nA/kPa的压力灵敏度,能响应0~20 Hz压力,并且在工作1000个周期后仍具有良好的稳定性。

载银sod基纳米分子筛的合成及抗菌性能

采用两步法合成了sod基系列分子筛(EMT、FAU、SOD),并通过离子交换法引入Ag^(+)得到载银分子筛,通过X射线衍射(XRD)、扫描电子显微镜(SEM)证明离子交换前后分子筛骨架结构和晶粒尺寸没有发生明显变化;通过红外光谱(IR)、热重(TG)证明制得的载银分子筛具有良好的稳定性;对获得的载银分子筛进行了Ag^(+)释放实验与抗菌能力测试,考察了分子筛种类和晶粒尺寸对抗菌性能的影响。结果表明具有笼状结构的FAU与EMT分子筛因可储存更多的Ag^(+)而具有更好的抗菌性能,而具有超笼结构的FAU分子筛抗菌性能最优。通过对比不同晶粒尺寸载银FAU分子筛抗菌数据发现,晶粒尺寸为100 nm的载银FAU分子筛因外表面丰富的抗菌活性位点以及其内部可以储存并不断释放Ag^(+)而具有最优的抗菌性能和抗菌寿命。而晶粒尺寸为10 nm的载银FAU分子筛由于晶粒尺寸较小、外比表面积大、扩散路径短,Ag^(+)的释放速率最快,抗菌效率最高。

利用羧甲基壳聚糖制备小尺寸绿色银纳米粒子的研究

对羧甲基壳聚糖、氯离子和日光合成银纳米粒子(AgNPs)的绿色方法进行改进,研究了氯离子浓度对小尺寸AgNPs制备的影响,以及所得AgNPs对金黄色葡萄球菌与大肠杆菌的抑菌效果。结果发现,控制反应溶液的氯离子浓度在0.2~0.8 mmol/L之间,可以获得小于10 nm的AgNPs。在氯离子浓度为0.2 mmol/L时,金黄色葡萄球菌比大肠杆菌对AgNPs更为敏感。通过调节反应体系的氯离子浓度,仅使用羧甲基壳聚糖、氯离子和日光即可实现小粒径绿色AgNPs的制备,制备的纳米粒子对革兰氏阳性菌具有更好的抗菌效果,实际应用中可根据治疗对象和药物剂型选择合适的制备条件。

Preparation and crystallization kinetics of micron-sized Mg（OH）2 in a mixed suspension mixed product removal crystallizer

Magnesium hydroxide is an important chemi- cal, and is usually obtained from seawater or brine via precipitation process. The particle size distribution of magnesium hydroxide has great effects on the subsequent filtration and drying processes. In this paper, micron-sized magnesium hydroxide with high purity, large particle size and low water content in filter cake was synthesized via simple wet precipitation in a mixed suspension mixed product removal （MSMPR） crystallizer. The effects of reactant concentration, residence time and impurities on the properties of magnesium hydroxide were investigated by X-Ray diffraction （XRD）, Scanning Electron Micro- scopy （SEM） and Malvem laser particle size analyzer. The results show that NaOH concentration and residence time have great effects on the water content and particle size of Mg（OH）2. The spherical Mg（OH）2 with uniform diameter of about 30 μm was obtained with purity higher than 99% and water content less than 31%. Furthermore, the crystallization kinetics based on the population balance theory was studied to provide the theoretical data for industrial enlargement, and the simulation coefficients （R2） based on ASL model and C-R model are 0.9962 and 0.9972, respectively, indicating that the crystal growth rate of magnesium hydroxide can be well simulated by the size- dependent growth models.

Magnéli相亚氧化钛陶瓷的制备及其应用研究进展

Magnéli相亚氧化钛是一系列非化学计量比氧化钛的统称,主要包括Ti_(4)O_(7)、Ti_(5)O_(9)、Ti_(6)O_(11)和Ti_(8)O_(15)等相,其中以Ti_(4)O_(7)的导电性最好,其理论电导率可达1500 S·cm^(-1),约为石墨的二倍。此外,Magnéli相亚氧化钛在强酸、强碱环境中均表现出极强的耐蚀性能,并且能够在水溶液中保持3.0 V以上的稳定电位窗口。Magnéli相亚氧化钛优异的性能使其在化学电源如铅蓄电池、液流电池、锂硫电池、可再生燃料电池,电解水的催化剂载体,热电及光电材料,光催化制氢以及电催化氧化降解有机污染物等领域中展现出良好的应用前景。目前,科研人员已经开发出一系列制备亚氧化钛的方法。但是在高纯度、单相、纳米或亚微米尺度亚氧化钛粉体,大尺寸的一体式亚氧化钛电极和金属基亚氧化钛涂层电极的规模化生产和应用中依然存在许多问题,限制了亚氧化钛系列产品在上述领域中的广泛应用。基于Magnéli相亚氧化钛陶瓷的固有特性,重点介绍了亚氧化钛粉体、一体式电极和涂层电极的制备方法及应用现状,同时对亚氧化钛相关材料的应用前景进行了简要概述,为科研院所及相关企业提供了参考依据、研究思路和解决办法。

石墨烯-银纳米粒子复合墨水的制备及直写打印研究

高性能导电墨水的研究与开发是实现印刷电子器件不断发展的关键。石墨烯的二维结构使其本身具有良好的柔性和导电性,但由于片层间范德华力的相互作用使其容易发生团聚和堆积,通过复合的方式引入金属纳米粒子,既可以防止发生团聚又可以降低石墨烯片层间的接触电阻,使复合材料的导电性增强。鉴于此,本工作采用原位化学还原的方法制备石墨烯(rGO)和银纳米粒子(AgNPs)组成的复合墨水,以实现AgNPs在rGO纳米片层上的均匀分布。通过直写打印技术将墨水打印在基底上,得到的印刷图案具有优异的导电性,典型的电阻率为1.48×10^(-6)Ω·m。经过数百次弯曲循环后,印刷图案的电阻值仅略有增加,表明图案具有极佳的稳定性和机械柔韧性。这对于印刷电子器件的发展具有重要意义。

基于生信分析纳米银对斑马鱼的毒性和机制

依托GEO数据库的GSE50718、GSE61186和GSE89653数据集,从中提取斑马鱼的转录组相关数据,通过生物信息学分析鉴定不同粒径和涂层的纳米银对斑马鱼进行暴露产生的显著差异基因,并比较相关差异基因的数量和上、下调关系.研究发现,斑马鱼的差异表达基因数量按从多到少的排序为:PVP-AgNPs-50nm> AgNO_(3)> PVP-AgNPs-150nm;Maltose-AgNPs> AgNPs.通过GO、KEGG和GSEA富集分析,本研究发现纳米银差异基因主要在免疫相关通路中有显著富集,而硝酸银则主要影响细胞周期及代谢途径.这一发现暗示纳米银与硝酸银在分子层面上的作用机制存在明显的差异.推测纳米银的毒性作用不仅源于释放的银离子,还与其“颗粒特异性”紧密相关.此外,纳米银的表面涂层亦对其毒性产生影响.这些发现为纳米银的安全有效应用提供了有益的参考和策略性建议.

微米活性液滴场致荷电效果及煤尘润湿性能研究

水雾荷电与溶液活性处理作为2种增效降尘手段,独立使用时均表现出良好的降尘效果。为探究二者联合使用对微细粉尘的沉降效果,选取十二烷基硫酸钠表面活性剂配置活性溶液,利用紫铜芒刺环形电极进行电晕荷电,在微米尺度液滴场致荷电的背景下,探究了微米活性液滴的荷电效果及其对无烟煤的润湿性。结果表明:活性溶液相较于纯水对电场的响应更为敏感;水雾荷电与溶液活性处理对于增强液滴破碎、减小液滴粒径及增强溶液润湿性能表现出协同效应;微米荷电活性水雾相较于普通水雾对无烟煤尘的捕集效率更高,对全尘、呼吸性粉尘的沉降效率分别高达91.77%、90.45%。

化学还原法制备银粉及其在导电胶中的应用

研究化学还原法制备银粉过程中Ag~+浓度、还原液滴加方式、分散体系对银粉形貌的影响机理,获得一款适合用于导电胶制备的银粉。采用硝酸银为银源,分别以明胶、阿拉伯树胶以及聚乙烯吡咯烷酮(简称PVP)和明胶混合体系作为分散剂,研究不同分散体系对银粉形貌及粒径等性能。结果表明银粉粒径随着溶液中Ag~+浓度升高呈现变大趋势;不同分散体系制备的银粉形貌差别较大,而粒径差别不大。以明胶为分散剂制备的银粉为规则的球状,以阿拉伯树胶为分散剂制备的银粉为规则的片簇状,以PVP和明胶混合体系作为分散剂制备的银粉形貌为球状与片状的混合。还原液加入方式对银粉粒径也有较大影响,以一次加入方式制备的银粉粒径分布范围较大。此外,银粉粒径随反应温度升高呈现逐渐变大的趋势。通过对比发现最适合用于导电胶制备的银粉为用以阿拉伯明胶单分散体系制备的球状银粉。化学还原法制备银粉过程中,溶液中Ag^(+)浓度、还原液滴加方式以及分散体系均对银粉形貌和粒径有不同程度的影响,用不同形貌的银粉制备导电胶时的体积电阻率有差别。

工艺矿物学参数自动分析系统在铜矿浮选尾矿银赋存特征研究中的应用

元素赋存状态及工艺矿物学特征是决定其选矿工艺及回收指标的关键因素,对指导矿产资源高效综合回收利用有重要意义。由于银矿物种类繁多且含量低、粒度细小不易识别,传统人为鉴别目标矿物并统计工艺矿物学参数的方法在银的赋存特征研究方面存在局限性,制约了资源高效综合利用。本文利用基于扫描电子显微镜(SEM)和X射线能谱仪(EDS)的工艺矿物学参数自动分析系统(BPMA)对某铜矿浮选尾矿样品(Ag 41.96μg/g,Cu 0.44%)进行矿物学分析,展示其在尾矿样品中铜和银的赋存状态及工艺矿物学特征研究中的具体应用。结果表明:样品中铜矿物主要为辉铜矿和斑铜矿;铜硫化物及其集合体的嵌布粒度细微且解离程度低,是影响铜回收的主要矿物学因素。样品中银主要以独立矿物的形式存在,(含)银矿物有自然银、辉银矿/螺状硫银矿、硒银矿、硒铜银矿、硫铜银矿和含银辉铜矿,银在各(含)银矿物中的分布率分别为95.62%、2.07%、1.33%、0.15%、0.80%和0.03%;银矿物嵌布粒度不均匀,粗粒(>74μm)、中粒(74~37μm)、细粒(37~10μm)、微粒(<10μm)银矿物的占有率分别为32.25%、30.35%、21.44%和15.95%;银矿物的解离程度较高,单体含量高达88.28%,可采用浮选法与铜硫化物一起回收。该研究为提高资源的选矿回收率提供了矿物学依据,同时采用的BPMA&SEM-EDS分析方法为矿物种类复杂、含量低、粒度细小的稀贵金属元素赋存状态及工艺矿物学研究提供了一种技术借鉴。