Sm3+掺杂含银硼酸钙玻璃的制备及光谱性质

采用熔融淬火技术制备了掺杂Sm3+的组分为30CaO-60B2O3-10AgNO3-xSm2O3(x=0.05,0.25,0.5,1,3,5(摩尔分数))硼酸钙玻璃。采用吸收光谱及荧光激发和发射光谱对样品的光谱性质进行了研究。样品吸收光谱测量表明样品中存在Ag聚集体和金属Ag纳米颗粒,Sm3+掺杂浓度的改变对金属Ag纳米颗粒的浓度产生影响,而对Ag聚集体的吸收影响较弱。样品的荧光光谱测量发现该系列样品均表现为宽带吸收和宽带发射特性,同时观察到了在405 nm激发下Sm3+的掺杂对Ag聚集体的发光产生了猝灭作用,但可改善样品发射光谱的成分,提高红色发射比例。色度学研究表明样品的色坐标随Sm3+掺杂浓度及激发波长变化。这些研究结果表明该系列样品是一种潜在的白光LED用荧光体材料。     

水溶性银纳米颗粒的制备及抗菌性能

采用液相还原法, 以单宁酸为还原剂, 聚乙烯吡咯烷酮(PVP)为修饰剂制备出了水溶性的表面修饰Ag纳米颗粒. 通过X 射线粉末衍射仪(XRD)、透射电子显微镜(TEM)、紫外-可见吸收分光光度计(UV-Vis)、傅里叶变换红外(FTIR)光谱仪等对所得样品的形貌和结构进行了表征. 采用肉汤稀释法测试了样品的抗菌性能, 考察了样品在水相中的分散稳定性, 提出了PVP修饰Ag纳米颗粒的形成机理. 结果表明所制备的样品具有Ag的面心立方晶体结构, 平均粒径为15-17 nm. 样品在水相中能长时间稳定分散; 对埃希氏大肠杆菌(E. coli)、金黄色葡萄球菌(S. aureus)具有明显的抗菌作用. 操作简便、条件温和的制备方法易于在工业规模上放大; 试剂无毒, 使得所制备的PVP修饰Ag纳米颗粒作为抗菌剂具有良好的应用前景.     

银纳米颗粒对CaSrSiO_4:Tb~(3+)光致发光性能的影响

采用高温固相反应法制备了系列的Ag, Tb~(3+)单掺和共掺CaSrSiO_4纳米荧光粉。XRD和SEM分析结果表明, Tb~(3+)和Ag颗粒的掺入对纳米粉末晶体结构的影响较弱,但CaSrSiO_4:0.7Tb~(3+),0.1Ag样品呈现了立方体结构,且颗粒尺寸明显增大。XPS结果显示Ag单质和Ag~+共存于荧光粉中。在243 nm激发下,同时观测到强的545, 415和381 nm的光致发光谱,以及较弱的437, 586和624 nm发光峰。掺入0.1%(摩尔分数)Ag纳米颗粒时,能够使CaSrSiO_4:0.7Tb~(3+)纳米荧光粉的光致发光强度增强25%。最后讨论了掺Ag颗粒浓度对Tb~(3+)的545和381 nm特征峰衰减曲线的影响。     

纳米Ag/ZnO光催化剂及其催化降解壬基酚聚氧乙烯醚性能

采用氨浸法制备了不同Ag负载量的纳米Ag/ZnO光催化剂,并用X射线衍射、比表面积测定、X射线光电子能谱和漫反射紫外-可见光谱测定了Ag/ZnO的晶型结构、比表面积、表面组成和光谱特征.以壬基酚聚氧乙烯醚(NPE-10)为模型污染物,分别在紫外光和可见光照射下考察了纳米Ag/ZnO的光催化活性.结果表明,Ag能成功地负载到ZnO表面,且随着Ag负载量的增加,ZnO的粒径逐渐增大,比表面积逐渐减小.与纳米ZnO样品相比,Ag/ZnO中Ag 3d5/2结合能减小,而Zn 2p和O 1s结合能增大,ZnO表面的羟基氧和吸附氧含量增加.当Ag负载量大于0.5%时,Ag/ZnO样品的吸收光谱发生红移,在可见光区出现吸收.光催化降解结果表明,0.5%Ag/ZnO样品的光催化活性最高,在紫外光和可见光照射3 h后NPE-10降解率分别约为77%和56%,而ZnO样品的光催化活性仅约为61%和40%.     

Ag@AgI等离子体负载TiO2酸蚀纳米带的制备及可见光光催化性能的研究

采用沉积-沉淀法将AgI分散到TiO2酸蚀纳米带上,然后通过光照进而分解出Ag颗粒,最终获得了Ag@AgI等离子体负载的TiO2酸蚀纳米带(AIST)。利用UV-Vis吸收光谱、XRD、SEM对产物进行表征,并研究了可见光下对甲基橙(MO)的光催化降解性能。结果表明,纳米带酸蚀后利于AgI的沉积,Ag的表面等离子体共振效应可以增强催化剂对于可见光的吸收,使可见光下AIST的光催化降解性能显著提高。     

银/铂双金属中空纳米颗粒的制备及光学性质研究

通过以Ag纳米颗粒为模板的置换和沉积反应,制备了Ag/Pt双金属复合纳米颗粒.用透射电子显微镜(TEM)对颗粒的形貌、尺寸和结构进行了表征,发现复合颗粒具有中空结构.紫外可见吸收光谱(UV-Vis)研究表明,Ag/Pt双金属中空复合纳米颗粒具有单峰的表面等离子共振吸收特征,随着反应溶液中氯铂酸和硝酸银摩尔比的增加,吸收峰先红移后蓝移.表面增强拉曼光谱实验结果表明,Ag/Pt双金属复合纳米颗粒对吡啶分子具有较好的增强效果.     

TiO2浓度对核-壳结构Ag/TiO2纳米复合粒子结构以及三阶非线性光学性质的影响

采用光还原方法制备了核-壳结构的Ag/TiO2纳米复合粒子, 通过TEM、UV-Vis光谱和XRD表征了不同TiO2浓度下Ag/TiO2纳米复合粒子的结构和光学性质. UV-Vis光谱证明了银颗粒的存在, 且复合粒子中的银粒径随着TiO2含量的增加而增加, 同时随着TiO2浓度的增加, 银的吸收峰出现明显的增强和展宽；从TEM照片 发现, Ag/TiO2纳米复合粒子是一种以Ag为核, 外面包覆一层TiO2的核-壳结构, TiO2浓度和Ag+浓度的增加, 使得复合粒子的银颗粒粒径增大. 用Z-扫描技术, 以锁模Ti:sapphire飞秒激光器发出的脉宽为130 fs激光做光源, 在790 nm波长的光作用下, 研究了0.5%(w)Ag+含量, 不同TiO2浓度的Ag/TiO2纳米复合粒子的非线性光学特性. 结果发现, 在790 nm激光作用下, 0.25%(w)TiO2样品膜有双光子吸收和自聚焦非线性折射现象; 而当TiO2浓度为0.70%(w)时, 样品膜的非线性吸收由反饱和吸收转变为饱和吸收.     

ZnO/Ag微米球的合成与光催化性能

用微波辅助多元醇法对预先制备的ZnO微米球进行修饰,合成了载银氧化锌微米球（ZnO/Ag）. 利用X射线衍射仪、场发射扫描电子显微镜、透射电子显微镜、X射线光电子能谱仪、紫外-可见双光束分光光度计和光致发光光谱仪等对样品的结构、形貌和光学性能进行了表征. 在紫外光照射下,通过亚甲基蓝的降解反应研究了样品的光催化活性. 结果表明,所制备的ZnO/Ag微米球是由面心立方的Ag纳米颗粒附着在纤锌矿结构的ZnO球表面形成;与ZnO相比,ZnO/Ag的紫外-可见光吸收光谱发生明显红移,在紫外和可见光范围均有较强的吸收;随着Ag含量的增加,ZnO/Ag荧光光谱强度先减弱后增强;与ZnO相比,ZnO/Ag的光催化活性明显提高,AgNO₃ 浓度为0.05 mol/L时制得的ZnO/Ag光催化活性最高.     

ZnO纳米柱状阵列表面AgX等离子基元修饰及其可见光光催化活性

采用浸渍法制备了表面AgX（X=I,Br）等离子基元修饰的ZnO纳米柱状阵列,研究了浸渍浓度和时间以及紫外光光照预处理对ZnO纳米柱状阵列可见光光催化活性的影响.采用场发射扫描电子显微镜、X射线衍射仪、紫外可见漫反射吸收光谱以及X射线光电子能谱仪等手段对ZnO纳米柱状阵列的形貌、相组成、禁带宽度及其表面特性进行了表征.结果显示,AgBr颗粒分布于ZnO纳米柱状阵列的顶端及顶端侧面,同时AgBr颗粒之间相互接触而形成网状结构.通过紫外光光照预处理,AgBr表面出现细小颗粒,形成Ag/AgBr/ZnO纳米复合结构.可见光光催化降解甲基橙结果表明,在相同工艺条件下所制AgBr/ZnO的可见光光催化活性明显优于AgI/ZnO,且与浸渍浓度及时间有关.由于ZnO纳米柱状阵列的比表面积大,AgBr的可见光响应特性以及Ag/AgBr纳米结构的表面等离子效应,经过紫外光光照预处理形成的Ag/AgBr/ZnO纳米复合结构表现出最好的可见光光催化活性.     

Ag负载TiO2纳米管微波辅助水热法制备及其光催化性能

以微波辅助水热法制备了二氧化钛纳米管,然后通过浸渍法在其表面负载了银纳米颗粒.所得样品用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、氮吸附、X射线光电子能谱(XPS)、紫外-可见漫反射等测试方法表征.微波加热处理可以大大缩短反应时间,产物为无定型纳米管,经高温焙烧后转变成锐钛矿型二氧化钛.所得纳米管的外径为7-8 nm,内径为5-6 nm,管长约200 nm,比表面积可达371 m2·g-1.负载的银分散在纳米管的表面,对纳米管的结构与晶型没有影响,但是拓宽了二氧化钛的光吸收范围,使吸收边红移至可见光区,并且有效抑制了光生电子空穴的复合.在可见光降解罗丹明B的实验过程中,与Ag负载的P25及纯二氧化钛纳米管相比,Ag负载二氧化钛纳米管具有更高的可见光催化活性,并且当Ag/Ti 物质的量的比为0.5%时,可见光催化性能最好.     

Preparation and characterization of silver nanoparticles by chemical reduction method

Silver nanoparticles were prepared by the reduction of AgNO(3) with aniline in dilute aqueous solutions containing cetyltrimethlyammonium bromide, CTAB. Nanoparticles growth was assessed by UV-vis spectroscopy and the average particle size and the size distribution were determined from transmission electron microscopy, TEM. As the reaction proceeds, a typical plasmon absorption band at 390-450nm appears for the silver nanoparticles and the intensities increase with the time. Effects of [aniline], [CTAB] and [Ag(+)] on the particle formation rate were analyzed. The apparent rate constants for the formation of silver nanoparticles first increased until it reached a maximum then decreased with [aniline]. TEM photographs indicate that the silver sol consist of well dispersed agglomerates of spherical shape nanoparticles with particle size range from 10 to 30nm. Aniline concentrations have no significant effect on the shape, size and the size distribution of Ag-nanoparticles. Aniline acts as a reducing as well as adsorbing agent in the preparation of roughly spherical, agglomerated and face-centered-cubic silver nanoparticles.     

Laser-assisted synthesis of Au-Ag alloy nanoparticles in solution

By using laser-induced heating, we prepared Au-Ag nanoalloys via three different procedures: (i) mixture of Au nanoparticles and Ag(+) ions irradiated by a 532 nm laser, (ii) mixture of Au and Ag nanoparticles irradiated by a 532 nm laser, and (iii) mixture of Au and Ag nanoparticles irradiated by a 355 nm laser. Procedure i is advantageous for the production of spherical alloy nanoparticles; in procedures ii and iii, nanoalloys with a sintered structure have been obtained. The morphology of the obtained nanoalloys depends not only on the laser wavelength but also on the concentration of nanoparticles in the initial mixture. When the total concentration of Ag and Au nanoparticles in the mixture is increased, large-scale interlinked networks have been observed upon laser irradiation. It is expected that this selective heating strategy can be extended to prepare other bi- or multi-metallic nanoalloys.     

Preparation of highly dispersed core/shell-type titania nanocapsules containing a single Ag nanoparticle

Core/shell-type titania nanocapsules containing a single Ag nanoparticle were prepared. Ag nanoparticles were prepared using the reduction of silver nitrate with hydrazine in the presence of cetyltrimethylammonium bromide (CTAB) as protective agent. The sol-gel reaction of titanium tetraisopropoxide (TTIP) was used to prepare core/shell-type titania nanocapsules with CTAB-coated Ag nanoparticles as the core. TEM observations revealed that the size of the core (Ag particle) and the thickness of the shell (titania) of the core/shell particles obtained are about 10 nm and 5-10 nm, respectively. In addition, the nanocapsules were found to be dispersed in the medium as individual particles without aggregation. Moreover, titania coating caused the surface plasmon absorption of Ag nanoparticles to shift toward the longer wavelength side.     

Enhanced electrochromic absorption in Ag nanoparticle embedded conjugated polymer composite films

Ag/MEH-PPV {poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]} composite films were prepared by the pulse current electrodeposition of Ag nanoparticles followed by spin coating of MEH-PPV and their enhanced electrochromic coloration was investigated. A relatively uniform Ag nanoparticle array was obtained by the electrodeposition and distinct plasmon absorption bands of Ag nanoparticles were observed. The absorption maximum of Ag/MEH-PPV was much higher than that of MEH-PPV, indicating that the Ag nanoparticles induced an enhanced absorption. In addition, the electrochromic absorption was 1.6 times higher at 500 nm wavelength, with a clearly different coloration compared to MEH-PPV.     

Single laser pulse induced aggregation of gold nanoparticles

Gold nanoparticles with an average diameter of 11 nm (Au(39000)) were prepared in an SDS aqueous solution. A 80-microm liquid droplet (microdroplet) of the solution was ejected into the atmosphere from a microdroplet nozzle. Structural changes of the gold nanoparticles in the microdroplet, after they were irradiated with a focused single-nanosecond laser pulse at the wavelength of 532 nm, were studied by transmission electron microscopy (TEM) and optical absorption spectroscopy. It was revealed that the gold nanoparticles are fragmented into small particles and then the small fragments aggregate with each other. The aggregation was found to be terminated 100 micros after the laser-pulse excitation.     

Synthesis of silver nanoparticles in an aqueous suspension of graphene oxide sheets and its antimicrobial activity

A solution-based approach to the synthesis of silver (Ag) nanoparticles by chemical reduction of AgNO(3) in a graphene oxide (GrO) suspension is demonstrated. X-ray diffraction and transmission electron microscopy indicate that the Ag nanoparticles, of size range 5-25nm, were decorated on the GrO sheets. The size and shape of the Ag nanoparticles are dependent on the concentration of the AgNO(3) solution. Antimicrobial activity of such hybrids materials is investigated against the Gram negative bacteria Escherichia coli and Pseudomonous aeruginosa. The bacterial growth kinetics was monitored in nutrient broth supplemented with the Ag nanoparticle-GrO suspension at different conditions. It was observed that P. aeruginosa is comparatively more sensitive to the Ag nanoparticle-GrO suspension.     

纳米银对表面吸附镝配合物的荧光增强效应研究

研究了不同粒径的纳米银对镝配合物(乙二胺四乙酸配合物)的光谱学性质影响。当配合物溶液的pH值范围为4.0～6.0时,加入纳米银,可观察到大量的纳米银聚集体形成,而在吸收光谱的长波处出现一个新的吸收峰,随着纳米银浓度的增加,该吸收峰逐渐红移,同时,镝配合物的荧光强度增强。实验结果表明,纳米银粒子对镝配合物的荧光增强效应及荧光增强因子与纳米银粒子的浓度和粒径密切相关。随着纳米银浓度的增加,配合物的荧光强度先增强而后又逐渐降低。小粒径的纳米银对镝配合物的荧光增强因子较小。本文从纳米银粒子的聚集效应、局部电磁场增强效应及光吸收效应等方面探讨了纳米银对表面吸附镝配合物的+荧光增强效应机理。     

Heat-Induced Precipitation and Light-Induced Dissolution of Metal (Ag & Au) Nanoparticles in Hybrid Film

Metal nanoparticle-doped materials have attracted much attention because of their enhanced third-order nonlinear optical susceptibility. In their application, (1) controllable precipitation and (2) stability against photo-irradiation are essential concerns. Silver or gold nanoparticle-doped films were made from hybrid sol containing metal ions with their stabilizer on silica glass substrates by the sol-gel dip-coating technique and their heat-induced precipitation and photo-stability were investigated. The heat-induced precipitation up to 1000°C was remarkably different in Ag and Au nanoparticles. After 120–500°C heating, Ag nanoparticles with a wide range of radii were formed in the hybrid films. Above 500°C, organic groups were completely evacuated and at 800°C, mono-dispersed Ag nanoparticles with radii of 2–4 nm were precipitated in the resultant film. On the other hand, Au nanoparticles of 10 nm average radius precipitated at 120°C and showed no drastic change in subsequent heating up to 1000°C. Since Ag nanoparticle-doped film showed the photosensitive change, their photostability was investigated by irradiating them under Xenon lamp light. The 800°C-heating sample showed no decrease in the plasma absorption band at around 420 nm wavelength after 20 h light irradiation, but the band intensities in the 120–500°C-heating films decreased noticeably.     

Facile synthesis, stabilization, and anti-bacterial performance of discrete Ag nanoparticles using Medicago sativa seed exudates

The biogenic synthesis of metal nanomaterials offers an environmentally benign alternative to the traditional chemical synthesis routes. Colloidal silver (Ag) nanoparticles were synthesized by reacting aqueous AgNO(3) with Medicago sativa seed exudates under non-photomediated conditions. Upon contact, rapid reduction of Ag(+) ions was observed in <1 min with Ag nanoparticle formation reaching 90% completion in <50 min. Effect of Ag concentration, quantity of exudate and pH on the particle size and shape were investigated. At [Ag(+)]=0.01 M and 30°C, largely spherical nanoparticles with diameters in the range of 5-51 nm were generated, while flower-like particle clusters (mean size=104 nm) were observed on treatment at higher Ag concentrations. Pre-dilution of the exudate induced the formation of single-crystalline Ag nanoplates, forming hexagonal particles and nanotriangles with edge lengths of 86-108 nm, while pH adjustment to 11 resulted in monodisperse Ag nanoparticles with an average size of 12 nm. Repeated centrifugation and redispersion enhanced the percentage of nanoplates from 10% to 75% in solution. The kinetics of nanoparticle formation were monitored using ultraviolet-visible spectroscopy and the Ag products were characterized using transmission electron microscopy, selected-area electron diffraction, scanning electron microscopy, X-ray powder diffraction, and atomic force microscopy. X-ray photoelectron spectroscopy was used to investigate the elements and chemical environment in the top layers of the as-synthesized Ag nanoparticles, while the metabolites in the exudate were analyzed using gas chromatography-mass spectroscopy. To our knowledge, this is the first account of M. sativa seed exudate assisted synthesis and stabilization of biogenic Ag nanoparticles; the nanoplates are notably smaller and better faceted compared with those synthesized by vascular plant extracts previously reported. Stabilized films of exudate synthesized Ag nanoparticles were effective anti-bacterial agents.     

A novel method to synthesize polystyrene nanospheres immobilized with silver nanoparticles by using compressed CO2

In this work, a novel route to synthesize polymer/metal composite nanospheres has been proposed. This method combines the advantages that the polymer chains collapse and entangle in the presence of compressed CO(2), which acts as antisolvent, and the metal nanoparticles and polymers can be precipitated simultaneously from micellar solutions by the easy control of CO(2) pressure. Ag/polystyrene (PS) nanocomposites have been successfully prepared using this method. The transmission electronic micrographs (TEM) of the obtained nanocomposites show that the smaller Ag nanoparticles are immobilized by PS nanospheres of about 50 nm; the phase structure was characterized by X-ray diffraction (XRD). The Ag/PS nanocomposites show absorption properties at a wavelength of approximately 417 nm. The results of X-ray photoelectron spectra (XPS) and FT-IR spectra indicate that there is no chemical linkage or strong interaction between PS and Ag nanoparticles in the resultant products. This method has many potential advantages for applications and may easily be applied to the preparation of a range of inorganic/ polymer composite nanoparticles.