【作者】 何鑫；

【导师】 赵修建；

【作者基本信息】 武汉理工大学 ， 建筑材料与工程， 2008， 博士

【摘要】 纳米材料所取得的进步证明了其在合成化学和材料科学领域有着巨大的发展前景,尤其是金属纳米材料所具有的特殊物理和化学性质使其在光学、光电、传感技术及生物检验等诸多领域都具有广泛的应用前景。这些性能与纳米粒子的尺寸和形貌密切相关,因此,可通过调节纳米粒子的尺寸、维度、组成及形貌实现对材料性能的控制,最终实现功能性纳米器件的设计与合成。虽然纳米材料的制备方法日益多样化,但在纳米材料的可控制备方面所取得的成就仍非常有限,因而得到科研工作者越来越多的关注。基于目前金属Ag纳米粒子的国内外研究现状,本论文利用化学液相法可控制备了多形貌金属Ag纳米粒子,并得到了一些新颖的Ag纳米结构,以图探索出一种简易的、金属纳米粒子形貌可控的合成路线,同时尝试性地将所制备的Ag纳米粒子应用于金属增强荧光（MEF）。本论文的主要研究成果包括以下几个方面:1、利用晶种法在溶液中和玻璃表面制备三角形Ag纳米粒子。溶液中粒子的边长为50±5nm,厚度为27±4nm,在透射电镜（TEM）和原子力显微镜（AFM）测试中粒子存在不同的优先投影面;提出晶种溶液的最佳制备温度为35℃;在玻璃表面可得到产量较高的类三角形纳米粒子;利用表面晶面淘汰机理解释了三角形纳米粒子的形成,认为是十六烷基三甲基溴化铵（CTAB）对晶面生长速率进行修饰的结果。2、以钛酸丁酯（TBT）和乙酰丙酮（AcAc）螯合而成的网络结构为软模板制备锯齿状Ag纳米线和皂荚形貌Ag纳米粒子。锯齿状纳米线的直径为20±5nm,长度达600 nm,角度变化范围为74～151°;锯齿状纳米线是由首尾相连的纳米棒发育而成,纳米棒连接处的晶界优先吸附Ag原子而逐渐发育完整;将反应温度提高为150℃,反应时间减少为6h,产物为规则皂荚形貌的Ag纳米粒子,其尺寸为60～70 nm。3、利用溶剂热法,在聚乙烯吡咯烷酮（PVP）存在下,以N,N二甲基甲酰胺（DMF）为溶剂和还原剂,通过工艺参数的调控,可实现单分散三角形/六边形纳米片、链状纳米片聚集体和纳米带多形貌Ag纳米粒子的可控制备。PVP与Ag⁺之间的键合作用,可降低DMF还原AgNO₃的反应速率,有利于形成具有高比表面能的纳米片,AgNO₃与PVP的比例是决定纳米片外形的关键;新颖链状Ag纳米片聚集体的生长可利用晶体二次生长来解释;在链状纳米片聚集体形成后继续处理7h,产物形貌将转变为长径比均匀的一维Ag纳米带,其直径为40～100nm,长度可达几微米,甚至十几微米。4、以溶剂热法制备的多形貌Ag纳米粒子为研究对象,研究Ag纳米粒子和Ag纳米薄膜对染料罗丹明B荧光性能的影响。在Ag纳米粒子存在下,罗丹明B的荧光强度得到显著增强,可部分消除荧光自猝灭效应;随着Ag纳米粒子浓度的增加,染料的荧光强度先增加,当达到最大值后,逐渐降低;相对于三角形Ag纳米片、六边形Ag纳米片和链状Ag纳米片聚集体,Ag纳米带可实现对罗丹明B荧光的相对最大增强;Ag纳米薄膜的存在也可实现对罗丹明B荧光信号的放大,且发射强度较Ag纳米粒子存在时要大。更多还原

【Abstract】 The progress of nanomaterials suggests its great potential foreground in the fields of synthetic chemistry and materials science,especially for metal nanoparticles with unique chemical and physical properties,which have extensive applications in optics,optoelectronics,sensor and bioassays.Their properties are strongly depended on the size and shape of metal nanoparticles.Therefore,it is believed that property-controllable metal nanoparticles will be conveniently produced by tuning their sizes,dimensionalities,compositions and morphologies,and expected to be fabricated into functional nanodevices.Although there have been a lot of reports on the synthesis of nanomaterials,the shape-controllable synthesis is still a challenge for materials and chemistry researchers.Based on the development of metallic silver nanoparticles in the world,this dissertation presents a facile chemical solution-method to prepare silver nanoparticles with various morphologies and obtain novel silver nanostructures.This dissertation also investigates application of silver nanoparticles in metal-enhanced fluorescence（MEF）.The main results and conclusions of this dissertation are outlined as follows:Chapter 2 presents a seed-mediated method to synthesize triangular silver nanoparticles in solution and on the glass.The nanoparticles synthesized in solution showed size of 50±5 nm and thickness of 27±4 nm.They exhibited different morphologies in transmission electron microscopy（TEM）and atomic force microscopy（AFM）,respectively.The most suitable temperature for preparation of seed solution was 35℃.Triangle-like silver nanoparticles could also be obtained on the glass by the seed-mediated method.The formation of the triangular nanoparticles was due to the modification in growth rates of crystalline planes by CTAB.Chapter 3 demonstrates a soft template method to prepare zigzag silver nanowires and gleditschia horrida-like silver nanoparticles.Zigzag nanowires showed uniform diameter of 20±5 nm,length of 600 nm and angles range of 74～151°.These nanowires with interesting shape were developed from end-to-end nanorods,and the interface could be observed between two nanorods.With the reaction time extended, the interface gradually disappeared,and zigzag nanowires finally formed.If the reaction temperature was elevated to 150℃and time was reduced to 6 h,the gleditschia horrida-like nanoparticles with size of 60～70 nm could be obtained.In Chapter 4,we demonstrate a solvothermal route to the shape-controllable synthesis of mono-dispersed triangular/hexagonal silver nanoplates,chain-like silver nanoplate assemblies and silver nanobelts in the presence of PVP,using DMF as solvent and reducing reagent.The strong interaction between PVP and Ag⁺ ions could be favorable for slowing down the reaction of DMF and AgNO₃.A slow and moderate reduction rate was advantageous for the formation of the nanoplates at higher yields,and the outline of silver nanoplates was determined by the ratio between AgNO₃ and PVP.The formation of novel chain-like nanoplate assemblies could be explained according to the secondary growth of the nanocrystals.If the reaction was continuously lasted for 7 h after the chain-like assemblies shaped, belt-like nanostructures with uniform aspect ratio could be obtained,showing diameter of 40～100 nm and length of several,even tens of micrometers.In Chapter 5,we investigate the effects of silver nanoparticles and silver nanoparticles coated-films on the fluorescent properties of dye Rhodamine B.Silver nanoparticles could largely enhance the fluorescence intensity of Rhodamine B and partially release its self-quenching effect.With the increase in the concentration of silver nanoparticles,the fluorescence intensity of Rhodamine B firstly enhanced up to a maximum,and then decreased.Among triangular nanoplates,hexagonal nanoplates, chain-like nanoplate assemblies and nanobelts,the maximal fluorescence enhancement of Rhodamine B solution could be obtained in the presence of silver nanobelts.The fluorescence intensity of Rhodamine B could also be enhanced in the presence of silver nanoparticles coated-films,and dye could exhibit higher emission intensity than that in the presence of silver nanoparticles.更多还原