AOT微乳体系中纳米银的可控合成及其紫外-可见光谱研究

在以琥珀酸二异辛酯磺酸钠(AOT)为表面活性剂、环己烷为连续相形成的W/O型微乳体系中,用增溶于微乳液水核中的AgNO₃为银源、水合肼为还原剂制备了纳米银溶胶,利用UV-Vis光谱分析了AgNO₃的浓度、AOT的浓度、还原剂的种类和水与表面活性剂的物质的量比(W)等参数对形成粒子数量及平均粒径的影响,为纳米银粒子的可控合成和纳米银的UV-Vis光谱解析提供了新的依据。研究表明,适当增大AgNO₃的浓度,有利于形成粒径较小的纳米银粒子;W值增大,形成粒子的平均粒径和粒子数量明显增加。和NaBH₄相比,水合肼在反胶束中的溶解性能较好,有利于微乳液反胶束中Ag+的还原。增大AOT的浓度,在一定范围内胶束对反应物的增溶能力增强,胶束的半径也相应减小,有利于形成数量较多、平均粒径较小的纳米银粒子。     

纳米银粒子的发光特性研究

研究了不同粒径和表面修饰的纳米银粒子的发光特性。研究结果表明,在不同波长光激发下,纳米银粒子在362 nm附近出现较强的发射峰,592和725 nm附近出现较弱的发射峰。随着激发光波长增加,发射峰强度下降,362 nm附近的发射峰红移。纳米银颗粒对210 nm的激发光最为敏感。发射峰波长与纳米银粒子表面修饰状态和颗粒尺寸关系不大,只是随着颗粒尺寸的减小,发射峰强度下降。随着狭缝宽度的减小,发射峰强度下降。随着纳米银胶浓度减少,发射峰逐渐聚拢合并为426 nm的单峰,且发射峰的强度先增强后逐渐下降。通过纳米银粒子表面光电子的吸收-再发射和表面能级杂化探讨了纳米银粒子的发光机理。     

甲基橙溶液的pH值对纳米银荧光增强效应的影响

研究了甲基橙溶液的pH对纳米银荧光增强效应的影响.当pH 1.5和2.1时,纳米银对溶液的吸收光谱影响甚小.当pH 3.1时,吸收峰蓝移26 nm,且强度明显降低.当pH值在3.8～8.2范围时,不仅吸收峰蓝移而且在426～456 nm出现宽吸收带.在任何pH值的甲基橙溶液中加入纳米银,S2→S0跃迁荧光发射带强度下降,但下降比率受pH值影响不大;S1→S0跃迁荧光发射带强度增强,其增强比率受pH值影响较大.当pH 2.1时,荧光增强比率最大;当pH 4.8时,荧光增强比率最小.分析认为,pH值对甲基橙溶液光谱性质的影响与不同pH值条件下甲基橙分子结构的改变以及分子在纳米银粒子表面不同的吸附方式、介质环境等因素相关,尤其与甲基橙分子与纳米银粒子间的距离密切相关.     

纳米银与表面吸附荧光素的荧光性能的影响

研究了纳米银粒子对表面吸附荧光素(fluorescein,Fl)的荧光性能的影响。Fl溶液中加入纳米银粒子,Fl分子包覆在纳米银粒子表面形成Fl_n-Ag复合物使纳米银相互桥连形成类似网络的结构,且Fl分子吸收峰随着纳米银浓度的增加发生红移。纳米银通过产生的强局域场将能量传输给Fl发光中心,实现了Fl的荧光增强,荧光增强效率随着纳米银浓度的增加具有最大值。较大粒径的纳米银使Fl获得最大荧光增强效率所需浓度较低且最大荧光增强效率值较高。研究结果表明,纳米银与Fl间的能量传输主要由Fl分子附近局域电磁场增强和分子到金属表面无辐射跃迁能量转移过程所决定并与纳米银的浓度、尺寸密切相关。     

微流控法二乙烯基苯乳液粒子成型机理研究

采用相界面跟踪(V()F)数值模拟方法,研究了轴流型微流控芯片中流速比、界面张力、粘度等对乳液粒子粒径的影响。模拟结果表明:乳液粒子粒径与流速比的对数存在线性关系,在一定范围内,当流速比增大时,粒径变小;当界面张力小于0.025 N/m时,乳液粒径随界面张力增大而增加,当界面张力超过0.03N/m时,乳液粒径变化趋于平缓;分散相粘度对乳液粒径的影响甚微。以聚乙烯醇(PVA)水溶液为连续相,二乙烯基苯(DVB)溶液为分散相,采用自制的聚二甲基硅氧烷(PDMS)轴流型微流控芯进行了DVB乳液粒子成型实验研究,获得了0.5~3.0 mm的DVB乳液粒子。     

GdF_3∶Eu~(3+)纳米晶的VUV荧光性质

利用微乳液水热法制备出GdF3∶Eu3+纳米晶及纳米棒。用X射线粉末衍射(XRD)和透射电子显微镜(TEM)等手段对材料的结构、形态及粒径大小等进行了表征。室温下真空紫外(VUV)光谱及荧光光谱表明GdF3∶Eu3+纳米晶中的Gd3+离子吸收一个光子,并将能量分两步传递给Eu3+,发生了双光子发射。从各跃迁的积分强度和量子效率表达式可以得到材料在160 nm紫外光激发下的量子效率约为170%。     

外场电压和Ag纳米尺寸对来自Ag的光电发射谱的影响

研究外场电压和纳米银粒子的尺寸对来自镶嵌在BaO薄膜中的纳米银粒子的光电发射的影响。在不同电压和不同尺寸条件下，计算了波长范围在 0.2到0.8μm的光电发射谱。给出了光电发射阈值对外场电压和纳米银粒子的尺寸依赖关系。同时认为在可见光范围中出现的光电发射是由于纳米银粒子的光学共振吸收所形成。这样的讨论有助于制备场助Ag-BaO光电薄膜的制备和工艺优化。     

GdF3:Eu3+纳米晶的VUV荧光性质

利用微乳液水热法制备出GdF3：Eu^3＋纳米晶及纳米棒。用X射线粉末衍射（XRD）和透射电子显微镜（TEM）等手段对材料的结构、形态及粒径大小等进行了表征。室温下真空紫外（vuv）光谱及荧光光谱表明GdF3：Eu^3＋纳米晶中的Gd^3＋离子吸收一个光子,并将能量分两步传递给Eu^3＋,发生了双光子发射。从各跃迁的积分强度和量子效率表达式可以得到材料在160nm紫外光激发下的量子效率约为170％。     

SiO2包覆铕（Ⅲ）配合物的荧光纳米粒子合成与性质

以前驱物pAB-DTPAA-APTEOS、正硅酸乙酯(TEOS)和三氯化铕(EuCl3)等为原料,采用油包水(W/O)的反相微乳液法,在正硅酸乙酯(TEOS)和3-氨丙基三乙氧基硅烷(APTEOS)的共同水解下,制备出新型的SiO2包覆铕配合物荧光纳米粒子Eu-pAB-DTPAA-AP-SiO2。运用TEM、IR、UV-Vis、荧光光谱等技术对荧光纳米粒子进行了表征。TEM结果表明:包覆体呈球形,分散均匀,平均粒径为40nm。纳米粒子与配体、前驱物的紫外吸收谱相比较,峰位发生了一定的红移,表明通过反相微乳液法得到的固体粉末与EuCl3反应后,已经生成配合物Eu-pAB-DTPAA-AP-SiO2。红外光谱研究表明,在801cm-1出现νSi—C的伸缩振动峰,471cm-1处出现νEu—O的伸缩振动峰。由此证实Eu-pAB-DTPAA-AP-SiO2配合物的存在。荧光光谱分析表明,纳米粒子Eu-pAB-DTPAA-AP-SiO2表现出较好的荧光性能,位于592,615,689nm的发射峰分别归属于Eu3 离子的5D0→7F1、5D0→7F2和5D0→7F4跃迁,其中最强峰615nm属于Eu3 的特征跃迁发射。作为一种新型的荧光试剂,该纳米粒子具有粒径小,亲水性强,荧光强度大,且表面的氨基能方便地与生物分子偶联,故可作为优良的时间分辨荧光标记物用于各种高灵敏生物检测技术中。     

微乳液法SiO2/罗丹明B荧光杂化纳米微球的制备与表征

在甲苯存在下的反相微乳液体系中,将γ-缩水甘油醚氧丙基三甲氧基硅烷(KH560)与罗丹明B进行预反应;再与正硅酸乙酯( TEOS)经原位溶胶-凝胶反应,制备SiO2/罗丹明B荧光杂化纳米微球.通过FTIR、UV-Vis、TEM、TG和光致发光谱对杂化纳米微球进行了表征.结果表明:罗丹明B与KH560间通过酯基形成化学键...     

Integral fluorescence enhancement by silver nanoparticles controlled via PMMA matrix

The metal-enhanced fluorescence is measured with different thickness of emission film. Silver nanoparticles are immobilized on glass slide by chemical self-assembly method. Rhodamine B molecules are dispersed in the polymer matrix of Poly(methyl methacrylate) (PMMA), then spin coated on prepared silver particles substrate with different thickness from 15 nm to 70 nm. The enhanced fluorescence is observed depending on the thickness of emission film since the average distance between rhodamine B molecules and silver nanoparticles is altered by the PMMA matrix. The 5-fold enhancement is attained. The experiment was explained qualitatively by an integral fluorescence enhancement.     

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.     

Spectral Investigations on N-(2-Methylthiophenyl)-2-Hydroxy-1-Naphthaldimine by Silver Nanoparticles: Quenching

The photo—physical properties of N-(2-methylthiophenyl)-2-hydroxy-1-naphthaldimine (NMTHN) on silver nano particles have been investigated using optical absorption and fluorescence emission techniques. Silver nanoparticles of different sizes have been prepared by two different methods. The increases in size of the silver nanoparticles cause a decrease in the quenching of fluorescence of NMTHN. Stern–Volmer quenching constants and the association constants have also been calculated.     

Solution-combustion: the versatile route to synthesize silver nanoparticles

The solution-combustion synthesis (SCS) method was used to prepare silver nanoparticles using glycine and citric acid as fuels. The different combination of fuel to oxidant ratio was used to prepare Ag nanoparticles and its effect on optical spectra, structure and the morphology explored. The purposed method is rapid, effective, cheap and convenient. Silver nanoparticles with different sizes and shapes were synthesized depending upon the different oxidant/fuel ratios. The nanoparticles were characterized using transmission electron microscopy, X-ray diffraction and ultraviolet–visible absorption spectroscopy. Histograms were drawn to compare the mean particle size of synthesized nanoparticles. It was found that citric acid was better fuel as compared to glycine as it results in the more spherical symmetrical nanoparticles, which are supported by various characteristic studies.     

Fluorescence Quenching of 1,4-Dihydroxy-2,3-Dimethyl-9,10-Anthraquinone by Silver Nanoparticles: Size Effect

Size effect of silver nano particles on the photophysical properties of 1,4-dihydroxy-2,3-dimethyl-9,10-anthraquinone (DHDMAQ) have been investigated using optical absorption and fluorescence emission techniques. Silver nanoparticles of different sizes have been prepared by Creighton method using magnetic stirrer and ultrasonic field. Quenching of fluorescence of DHDMAQ has been found to increase with decrease in the size of the silver nanoparticles. Stern–Volmer quenching constants have also been calculated.     

Preparation of starch stabilized silver nanoparticles with spatial self-phase modulation properties by laser ablation technique

Silver nanoparticles inside the starch solution have been successfully fabricated by laser ablation of a silver plate immersed in starch solution. The ablation has been done using a Q-switched Nd:YAG laser at 10 Hz repetition rate. The starch solution allows for the formation of silver nanoparticles with uniform particle diameters and well dispersed. The ablation was performed at different time durations to study the influence of the laser ablation time on efficiency of particle formation and sizes. The Spatial Self-phase modulation phenomena which can determine the nonlinear optical property of the samples were also investigated for starch solutions containing silver nanoparticles.     

金/银纳米颗粒对Eu掺杂薄膜发光特性影响的研究

本文将三种金属纳米颗粒(球形银纳米颗粒、三角形银纳米薄片和三角形金纳米薄片)分别置于Eu(TTFA)3掺杂的Su8薄膜上研究了它们对铕配合物薄膜发光的影响.结果显示,金属纳米颗粒的局域等离子体共振(LSPR)谱对薄膜发光有很好的调控作用.对于LSPR谱分别与铕配合物激发谱和辐射谱重叠较好的球形和三角形两种银颗粒,相比于未放置颗粒时薄膜的发光,放置有颗粒的发光有明显的增强,其中球形银颗粒的样品的发光增强效果更为明显.而对于LSPR谱与铕配合物激发谱和辐射谱都不重叠的三角形片状金颗粒,该颗粒对样品的发光则起到了猝灭作用.     

On 308 nm photofragmentation of the silver nanoparticles

Silver nanoparticles (Ag NPs) were prepared by different chemical methods possessing different sizes 3 ± 2, 8 ± 2, and 20 ± 5 nm. The influence the size of Ag NPs was demonstrated by the absorption and fluorescence spectra, the maximum absorption of Ag NPs increases as the particle size increases. When Ag NPs irradiated with 308 nm excimer laser; the maximum absorption and the full width at half maximum decreased as the number of pulses increased up to 100,000 pulse; due to the size reduction. The fluorescence spectra of Ag NPs and irradiated Ag NPs with 308 nm excimer laser were recorded after excitation at 441.5 nm He-Cd laser, showing a red shift increasing as the particle size is increased.     

Nonlinear optical properties of nanometer-size silver composite azobenzene containing polydiacetylene film

Diacetylene monomer containing p-nitrophenyl azobenzene moiety (NADA) was synthesized. Silver nanoparticles with different concentrations were adulterated in the above polymerized NADA (PNADA) films and the third-order nonlinear optical properties were investigated in detail. UV–vis spectra and transmission electron microscopy were used to confirm the formation of PNADA/Ag nanocomposite films. The silver nanoparticles (average size of 10 nm) were well dispersed in the polymer films. The value of the nonlinear refractive index n ₂ for PNADA films (8.48×10⁻¹⁵ cm²/W) was much higher than that of pure polydiacetylene films. Further, the introduction of silver nanoparticles into the PNADA polymer films led to the further enhancement of nonlinear optical properties. The maximum value of n ₂ for PNADA/Ag nanocomposite films could be 11.6×10⁻¹⁵ cm²/W. This enhancement should be ascribed to the surface plasmon resonance of silver nanoparticles.