光诱导转化法制备片状三角形银纳米粒子的表面增强喇曼散射

采用柠檬酸三钠化学还原法制备球形Ag纳米粒子溶胶,并用高压球形氙灯对球形Ag纳米粒子溶胶进行光诱导实验.利用透射电子显微镜、紫外-可见吸收光谱研究了不同光照时间下的银胶纳米粒子的光谱特性和表面形貌,并以结晶紫为探针分子测量了银胶纳米粒子的表面增强喇曼散射光谱.实验结果表明:随着光照时间的增多,Ag纳米粒子溶胶颜色变化显著;紫外-可见吸收光谱吸收峰从单一峰渐渐显示出多个峰;透射电子显微镜图显示Ag纳米粒子由球形逐渐转变成片状三角形银纳米粒子、截角的片状三角形银纳米粒子;表面增强喇曼散射的增强效应随着光照时间的变化先逐渐增大,然后逐渐减小.     

银纳米粒子阵列的自组装及其表面增强拉曼光谱应用

在以聚赖氨酸为表面耦联层分子的玻片基底制备了银纳米粒子阵列。ＳＥＭ表征结果表明,银粒子以亚单层的形式排列在基底表面。比较银溶胶和纳米粒子阵列的紫外可见光谱可见聚赖氨酸耦联层对银纳米粒子的粒径具有一定的选择性,甲基紫精在银纳米粒子阵列上的表面增强ＦＴ拉曼光谱表明在近红外区拉曼散射的表面增强主要来自于化学增强效应。     

银纳米粒子自组织二维有序阵列

采用液液二相转移方法合成出颗粒直径为(4.18±0.5)nm的银纳米粒子溶胶,并用紫外可见光谱对所制得的银纳米粒子溶胶的单分散性和稳定性进行了研究.结果表明,所得到的溶胶相为稳定的、粒径分布窄的单分散体系.红外光谱的分析结果表明,稳定剂1壬基硫醇包缚在银纳米粒子表面.并且,通过自组织方法获得了二维有序的银纳米粒子阵列 关键词： 银纳米粒子 液液二相转移方法 自组织 二维有序阵列     

金纳米粒子的电化学合成及光谱表征

采用电化学方法合成各种形状的金纳米粒子,生成的金纳米粒子形貌与施加电流有关,通过匀速递增电流电解的方法,可制备得到哑铃形,球形以及棒状金纳米粒子,采用恒电流电解方法主要获得球形及哑铃形纳米粒子。利用透射电镜、紫外-可见光谱及拉曼光谱对金纳米粒子进行相关表征。紫外-可见光谱研究发现金纳米棒出现位于近红外区间的吸收峰(985 nm),由此推测棒的长径比约为6。以结晶紫为探针分子,研究了金纳米粒子的表面增强拉曼光谱(SERS)效应,并分析得出其平躺的吸附模式。根据形貌表征的结果推断了纳米粒子的生长机理。     

一种制备金纳米粒子的新方法

报道了一种温和的、低成本、有效制备高纯度单分散金纳米粒子的新方法.采用种子生长法,在表面活性剂十八烷基苄基二甲基氯化铵(BDAC)体系下液相合成金纳米粒子.通过改变实验中反应温度和反应时间等条件,制备了粒径为25-50nm的金纳米粒子,运用透射电子显微镜(TEM)对纳米粒子的形貌进行分析,利用紫外可见光谱(UV-Vis)对产物进行光谱表征,并讨论了金纳米粒子的形成机制.结果表明,金纳米粒子的粒径随反应温度的升高及反应时间的加长有增大的趋势.     

新型C60衍生物／Ag复合纳米材料的制备及光谱性质

利用1,3-偶极环加成反应合成了联吡啶基C60单加成衍生物N-甲基-2-[4′-(4″-甲基-2′,2″-联吡啶基)]-3,4-C60吡咯烷(C60BPY),并用NaBH4还原法和银溶胶直接组装法制备了C60BPY/Ag复合纳米结构。透射电子显微镜(TEM)表明,两种复合纳米结构的粒子粒径分别在30~45nm和40~55nm之间,粒子形状较规则,且分散性较好。在复合纳米结构形成过程中,C60BPY分子有效地控制了银粒子的生长和团聚,起到了很好的稳定和分散作用。紫外-可见吸收光谱中,两种复合纳米结构分别在430和490nm处出现了银纳米粒子的表面等离子体共振吸收峰,说明随着粒径的增大,吸收峰发生了红移。荧光发射光谱显示,C60BPY/Ag复合纳米体系猝灭了C60BPY在720和805nm处的发射峰,并对其机理进行了探讨。这种复合纳米体系有望在光电器件、传感器及催化领域有潜在的应用前景。     

介孔SiO2纳米棒的制备及其表面锚接金纳米粒子

 以正硅酸乙酯为硅源,十六烷基三甲基溴化铵为模板剂,聚乙二醇为分散剂,采用溶胶-凝胶法制备出SiO₂纳米粒子,应用透射电镜、扫描电镜、X射线衍射仪、红外光谱仪和X射线能谱仪研究了粒子的性能。结果表明：所得产物是具有周期性规则介孔的棒状粒子,长径比随着硅源、模板剂和分散剂浓度的降低而减小;向反应体系中引入乙醇,随着乙醇与水的体积比例的增加,粒子由棒状向球状转变,进而形成不规则絮状凝聚体。用硅烷化技术对SiO₂纳米棒表面进行修饰后吸附平均粒径3.7 nm的金种子,再用多轮生长法使种子长大,经过30轮生长,种子平均粒径增大至59 nm,得到了SiO₂-Au复合纳米体系。透射电镜和紫外-可见分光光度计分析结果表明：金纳米粒子锚接在SiO₂纳米棒表面的某些点位,呈分散分布;复合体系表现出强烈的金的表面等离子体共振吸收峰,该峰随着金粒子的粒径增大,在500~700 nm波段内红移。     

不同形貌金纳米粒子的制备及其表面增强拉曼散射效应的研究

不同形状的金纳米粒子在表面增强拉曼散射(surface enhanced Raman scattering,SERS)中有不同的增强效果,多面体金纳米粒子具有多角结构,显示出比金纳米板更为明显的增强效果,近年来对其合成和性质的研究备受关注。该研究探究了十二面体,二十面体,三角板,球形四种形状的金纳米粒子在SERS中不同的增强效果。分别采用硼氢化钠还原法和以N,N-二甲基甲酰胺(DMF)为还原剂制备金三角纳米片和二十面体金纳米粒子,又以二十面体金纳米粒子为种子制备出十二面体金纳米粒子,并分别以以上三种不同形貌的金纳米粒子及球形金溶胶为基底,4-巯基吡啶,对巯基苯甲酸为探针分子检测了其在不同激发波长下的增强效果。透射电子显微镜结果表明金三角纳米板的平均边长为130nm,二十面体和十二面体金纳米粒子的粒径分别为100和120nm。三者的紫外可见吸收峰分别在589,598和544nm处。表面增强拉曼散射结果表明金多面体比金三角纳米板表现出更好的增强效果。     

紫外光引发还原制备金溶胶及其SERS活性的研究

文章报道了一种用紫外光引发还原制备金溶胶的新方法,其还原过程经历了自由基机理。用紫外可见光谱观察了不同反应时间溶胶状态的变化。结果表明,光照反应2h时明显出现金溶胶粒子,7h后氯金酸基本转化完毕。同时,研究了稳定剂聚乙烯吡咯烷酮(PVP)的加入对还原过程的影响,结果表明,PVP的加入不仅稳定了溶胶,而且降低了反应速率。用SEM观察了溶胶粒子聚集体的形貌。最后以1,4-bis(4-vinylpyridyl)phenylene为探针分子研究了这种溶胶的SERS活性。     

银纳米粒子对组装阵列中耦联分子拉曼散射的影响

分别用硼氢化钠和氢气还原法制备了两种不同的银溶胶(I和II),并采用自组装技术将银纳米粒子组装到对巯基苯胺(PATP)修饰的光滑银基底表面,形成银纳米粒子亚单层二维阵列。比较两种阵列中PATP的表面增强拉曼光谱发现,溶胶II所得阵列中的PATP的b2振动得到了较大的增强,即存在较大程度的电荷转移,说明银纳米粒子的性质直接影响了耦联分子的光谱特征。对溶胶Ⅰ进行离心处理,组装,得到的拉曼特征与阵列II类似。就溶胶II的银纳米粒子而言,组装结构中可能形成Ag-N化学键,从而导致更强的氨基与银粒子的相互作用。     

银溶胶的合成、表征及其表面增强拉曼散射特性研究

报道了一种简单的合成均匀、稳定的银溶胶的方法,通过透射电子显微镜(TEM)观察其形貌,并利用UV-Vis谱、XPS等手段对其进行表征,以罗丹明6G(R6G)作为探针分子研究在银溶胶纳米粒子上的表面增强拉曼效果,结果表明所合成的银溶胶具有较强的表面增强拉曼散射效果。     

利用紫外-可见光谱研究水溶液中银纳米盘的生长过程及稳定性

在水相体系中以柠檬酸钠和硝酸银为反应物,利用可见光诱导的还原过程在室温下制备盘状的银纳米粒子,通过紫外-可见光谱监控了不同反应条件下银纳米粒子的生长过程及体系的稳定性．吸收光谱随时间的变化表明,在一定的反应条件下早期的产物为球形粒子;随着反应时间延长盘状产物开始逐渐生成并长大,球形粒子数也进一步增加;而到了后期盘状粒子则通过粒子间的Ostwald熟化过程进一步长大．研究还发现,过量的柠檬酸根离子无助于稳定胶态体系,而适量的PVP(聚乙烯吡咯烷酮)的加入则能起到有效的稳定作用;严格控制的搅拌对于保证体系良好的分散稳定性不可缺少．进一步的研究还表明,在反应体系中引入大量的氢氧根离子能大大的加快反应速度．     

纳米银/丝素复合材料的制备及其光谱性质研究

开发可靠、生态友好的纳米材料合成方法是当今纳米技术发展的一个重要方面,基于天然生物材料如丝素蛋白原位合成来制备纳米贵金属溶胶是一种具有极大发展潜力的方法之一。文章在室温下以丝素原位还原硝酸银制得了纳米银/丝素复合溶胶,通过紫外-可见光谱、原子力显微镜、荧光光谱和共振光散射对其制备过程和光谱性质进行了表征。实验表明丝素链中的酪氨酸残基对AgNO₃还原生成纳米银颗粒起了主要作用,制得的纳米银粒子均匀地包埋在丝素胶体中,具有很好的分散性和稳定性,可长期保存。丝素蛋白与纳米银复合后,荧光强度明显增加,证明了丝素蛋白与纳米银表面之间形成了较强的化学吸附,在银表面形成了一个相对稳定的络合物致密层。同时利用共振散射光谱分析实验进一步证实了纳米银粒子的形成。     

质子酸功能化离子液体中银纳米颗粒的制备及其光学性能研究

以质子酸功能化离子液体1-丁基-3-甲基咪唑磷酸二氢盐([Bmim]H₂PO₄)为反应介质和表面活性剂,采用简单的化学还原法制备了具有形状各向异性的块状银纳米颗粒。通过X射线衍射(XRD)、扫描电镜(SEM)、紫外-可见(UV-Vis)吸收光谱等一系列手段对其结构、形貌及光吸收特性进行了表征。结果表明,所制备的银纳米块具有立方结构,其平均横向尺寸约为30 nm,在硅片上自组装形成密堆积结构的多层膜。以1,2-二(4-吡啶基)乙烯(BPE)作为探针分子,研究所制备银纳米颗粒的表面增强拉曼散射(SERS)活性。结果表明所制的银纳米颗粒是较好的SERS基底,具有良好的增强效果,痕检能力及稳定性。对BPE分子的最低检测浓度可低至10-9mol·L-1,而且保存了90天后,其检测灵敏度没有显著的降低。     

Influence of several factors on the growth of selenium nanowires induced by silver nanoparticles

This paper presents a study on the crystallization and growth mechanism of selenium nanowires induced by silver nanoparticles at ambient conditions with special reference to the effects of factors such as the shapes and size of silver nanoparticles, the induced reaction time, and the molar ratio of Ag⁰ to SeO₃²⁻ ions. The synthesis approach is conducted with no need of any stabilizers, and with no sonochemical process and/or templates. It is found that whether silver spherical particles or colloids can lead to the formation of nanowires with average diameter of 25 nm and lengths up to a few micrometers, and silver nanoplates lead to the formation of flat Se nanostructures. In particular, Au, Cu, Pt, and Pd particles cannot induce the growth of selenium nanowires in aqueous solution at room temperature. The results indicate that silver particles play a critical role in determining the growth of selenium nanowires. The lattice match between hexagonal-Se and orthorhombic- or trigonal-Ag₂Se particles is the major driving force in the growth of such nanostructures. The findings would be useful for design and construction of heterogeneous nanostructures with similar lattice parameter(s).     

A sunlight-induced method for rapid biosynthesis of silver nanoparticles using an <Emphasis Type="Italic">Andrachnea chordifolia</Emphasis> ethanol extract

In this study a sunlight-induced method for rapid synthesis of silver nanoparticles using an ethanol extract of Andrachnea chordifolia is described. The silver nitrate solutions (1 mM) containing the ethanol extract of Andrachnea chordifolia were irradiated by both sunlight radiation and by sunlight radiation passed through different colored filters (red, yellow or green). The smallest size of silver nanoparticles was obtained when a silver ion solution was irradiated for 5 minutes by direct sunlight radiation. Further examination of the shape and size and of the surface chemistry of these biogenic silver nanoparticles, which were prepared under sunlight radiation, was carried out using transmission electron microscopy and infrared spectroscopy, respectively. Transmission electron microscopy images show spherical particles with an average size of 3.4 nm. Hydroxyl residues were also detected on the surface of these biogenic silver nanoparticles fabricated using plant extract of Andrachnea chordifolia under sunlight radiation. Our study on the reduction of silver ions by this plant extract in darkness shows that the synthesis process can take place under dark conditions at much longer incubations (48 hours). Larger silver polydispersed nanoparticles ranging in size from 3 to 30 nm were obtained when the silver ions were treated with the ethanol extract of Andrachnea chordifolia under dark conditions for 48 hours.     

Synthesis and characterization of nanophased silver tungstate

Silver tungstate (Ag₂WO₄) nanoparticles in two different morphologies are prepared by controlling the reaction kinetics of aqueous precipitation. X-ray diffraction studies reveal that the silver tungstate nanoparticles are in the α-phase. SEM images show the rod-like and fiber-like morphologies of the nanoparticles with high aspect ratios. The TGA and DTA studies show the high thermal stability of the nanorods. The average crystallite sizes (20–30 nm) of the rod-like silver tungstate estimated from TEM is consistent with the XRD results     

Fluorescence Modulation of Acridine and Coumarin Dyes by Silver Nanoparticles

Silver nanoparticles were synthesized by chemical reduction of silver ions by sodium borohydride in the presence of poly-(N)-vinyl-2-pyrrolidone in solution of short chain alcohols. The nanoparticles are stable in 2-propanol, and the average diameter of the Ag colloid obtained in this solvent is about 6 nm. The photophysical properties of acridinium and coumarin dyes in 2-propanol are affected by the presence of silver nanoparticles. The interaction of silver nanoparticles with acridinium derivative leads to a spectral change of its intramolecular charge transfer (ICT) absorption band. The dye emission increases suddenly with the initial addition of the Ag metal nanoparticles, but at a high concentration of the colloid, static fluorescence quenching occurs with a progressive decrease of the fluorescence efficiency. Amino coumarin fluorescence is only quenched by the silver nanoparticles in solution.     

碱石灰玻璃表面长方形银纳米颗粒的制备与表征

采用离子交换结合热处理的方法在碱石灰玻璃表面制备了银纳米颗粒。通过紫外-可见分光光度计、X射线衍射仪、扫描电子显微镜对样品进行了表征。结果表明:热处理时,银离子在玻璃表面成核并生长成近似长方形的纳米颗粒。吸收光谱在416nm附近出现明显的银纳米颗粒表面等离子体共振吸收特征峰。     

Multiple activation of ion track etched polycarbonate for the electroless synthesis of metal nanotubes

In our study, we examined the formation of thin films of silver nanoparticles on polycarbonate and the influence of the silver loading on the electroless synthesis of metal nanotubes. Control of the silver film thickness occurred by consecutive dipping of the polymer template in tin(II) and silver(I) solutions. The deposition progress was studied using UV-Vis spectroscopy. The reaction mechanism relies on the adsorption of reactive ions on the polymer template as well as on the silver nanoparticles. The initial catalytic activity of silver-covered ion track etched polycarbonate is an important governing factor for the electroless synthesis of metal nanotubes with desired thickness and shape. Therefore, the presented method allows specific template preparation according to given synthetic demands. High aspect ratio copper, gold, and platinum nanotubes were produced by the combination of sufficiently activated templates with optimized electroless plating procedures.