【作者】 徐敏敏；

【导师】 顾仁敖； 姚建林；

【作者基本信息】 苏州大学 ， 物理化学， 2011， 博士

【摘要】 贵金属纳米结构材料合成和性质的研究已受到普遍关注。迄今各种新型单组分、多组分纳米结构材料的设计调控、纳米结构构筑新技术的建立以及纳米材料在光学、电学、催化、生物等领域的应用均获得了很大突破。其中,材料的应用需建立在纳米结构的可控合成以及对其生长机理详细解析的基础上。因此设计制备具有特性功能的纳米结构材料可望为其应用的拓展提供实验基础。光学性质及催化性能是诸多贵金属纳米材料拥有的特殊属性。特别是表面增强拉曼散射（SERS）效应是纳米尺度上特异光学的现象。其与材料的种类、形状、尺寸和聚集度等密切相关。通过调控纳米材料的结构以及形状等不仅可以获得具有理想SERS效应的基底,用来研究分子的吸附以及反应,也可为SERS机理的研究提供合适的模型材料。同时,纳米结构材料往往具有较高的比表面,表现出优异的催化性能,因此这类材料可成为同时具有SERS活性和催化性能的功能材料。本论文通过各种方法调控合成具有特殊形貌的纳米结构,分析了纳米结构的成型机理,研究了这些纳米结构材料在催化、电催化、电化学传感等方面的应用。通过电化学结合SERS研究了分子在纳米级粗糙结构电极表面的吸附和反应行为,主要研究内容和结果如下:（1）发展了具有高密度层错结构的银纳米线的合成技术,研究了其催化以及SERS活性。在聚丙烯酸钠的诱导下,结合Fe₂O₃/Au种子法,快速、高产率制备银纳米线;通过调节反应物的添加量,考察了种子、硝酸银、聚丙烯酸钠对生成银纳米线的影响。所得的银纳米线具有大量高密度的层错以及纳米线弯曲、相互缠绕的特点。其对于对硝基苯酚的催化还原表现出很高的催化活性,其催化效率是多元醇法合成的五重孪晶银纳米线的170倍,这主要源于大量的层错结构。由于银纳米线相互缠绕而可能形成大量的“热点”区域,表现出极高的SERS活性,由此类银纳米线构成的基底可使对巯基苯的检测限达到10^-7 mol·dm^-3。（2）可控合成微米尺度银片,并以此构建过氧化氢的传感器。在聚丙烯酸钠以及混合溶剂（水和四氢呋喃）的体系中,方便、快捷地合成了银微米片,运用包括SERS在内的各种手段研究了其晶型及可能的生长机理,发现银微米片为介晶结构。利用此银微米片构建过氧化氢检测的传感器,从响应线性范围及时间、检测限、选择性及稳定性等方面考察了该传感器的性能,结果表明,银微米片传感器对过氧化氢的电还原具有很好的响应,其检测线性范围为50μmol·dm^-3 25 mmol·dm^-3,检测限为13.8μmol·dm^-3,响应时间为3 ⁵ s,且具有很高的选择性和稳定性.。此外,作为非酶安培型传感器,具有成本低廉、制备简单、检测灵敏、检测范围宽等特点。（3）调控合成条件,快速制备形貌可控的钯纳米材料,研究其SERS效应以及电催化活性与形貌的关系。调节不同的添加剂,合成了包括五角星、内凹立方体、荆棘、杨梅、大杨梅等形貌各异的钯纳米粒子。所得的钯纳米粒子可作为甲酸电催化氧化反应的催化剂。从催化活性、催化效率、催化剂的稳定性等角度分析,发现荆棘状和杨梅状的钯纳米结构具有良好的催化性能,有望成为甲酸燃料电池阳极催化剂。以1,4-BDT为探针分子,对比了各种形貌的钯纳米材料的SERS效应,发现具有内凹立方体结构的钯纳米粒子增强效应最好,这与其结构及在可见光谱区存在SPR峰有关。（4）采用电化学现场SERS技术,系统研究了各种纳米结构电极表面的分子吸附以及反应行为,为分子水平上解析纳米结构/溶液界面结构提供实验依据。选择对表面结构和电场十分敏感的三键分子,如2, 3, 4-氰基吡啶异构体、2-氨基-5-氰基吡啶、对氨基苯甲腈、苯乙炔等为探针,结合SERS光谱信息以及电化学CV研究,获得了这些三键分子在金、铂、钯等具有纳米结构贵金属及过渡金属表面的吸附行为。研究发现分子的吸附行为与纳米结构电极种类、电极电位、取代基的位置以及取代官能团的数目等因素有关。苯乙炔和对氨基苯甲腈在极端电位下还发生了表面反应。总之,含环以及三键基团的分子提供了丰富的光谱信息,有利于解析电化学界面行为。更多还原

【Abstract】 The synthesis and properties of noble metallic nanomaterials have aroused a lot of attention in the scientific field. Great success has been achieved in the designing the mono- and multi-component nanostructures, fabricating methods, as well as the applications in optics, electronics, catalysis, biology. These specific applications are based on the controlled synthesis and the exact growth mechanisms of nanostructures. Therefore, design and synthesis of new nanomaterials with novel properties offer experimental basis for expanding their various applications.Optical properties and catalytic activities are the two specific characteristics of the noble metallic nanostructures. Particularly, surface enhanced Raman scattering （SERS） is a novel optical phenomenon in the nanoscale. It results in the significant enhancement of Raman signal, which is related to the material nature, morphologies, sizes, and the nanostructure aggregation. Fine SERS substrates can be prepared by adjusting the morphologies and sizes. They act as the substrates for molecular absorption and/or reaction, as well as the model materials for the investigation on the SERS mechanisms. Moreover, majority of nanomaterials exhibit excellent catalytic performance due to their high specific surface area. As a result, the noble metallic nanostructures can serve as functional materials in both SERS and catalytic fields.This dissertation is focused on the four facets: synthesis of specific nanostructure morphologies, the growth mechanism of nanomaterials, applications in catalysis, electrocatalysis, sensor, and the molecular adsorption on the rough electrodes, respectively. The main results are listed as follows:（1） Stacking faults enriched Ag nanowires with high yield were prepared by the sodium polyacrylate（PAANa） combined with the seed-mediate（Fe₂O₃/Au） method. Control experiments were performed to identify the effects of the seeds, AgNO3 and PAANa by tuning the adding volumes. A model catalytic reduction of p-nitrophenol by NaBH4 was conducted due to the rich stacking faults in the twist Ag nanowires, The catalytic efficiency of our Ag nanowires is 170 times superior than that of five-fold twinned Ag nanowires prepared by polyol reduction approach. Besides, lots of“hot spot”can be formed originated from their twist characteristics. The excellent SERS performances were proved by the probing molecule, 1,4-BDT. The detection limit was as low as 10-7 mol·dm^-3.（2） It was reported that Ag microplates with controlled morphology were synthesized and applied in fabrication of H₂O₂ sensors. In the presence of PAANa and mixed solvent （water/THF）, a convenient and rapid synthetic method for Ag microplates were sequentially developed. Various approaches, such as the SERS experiments, were employed to determine the crystal pattern and the possible growth mechanisms. It was concluded that the Ag microplates are mesocrystal. Then H₂O₂ sensors were fabricated based on the Ag microplates and their performances were estimated by response linear region, response time, detection limit, as well as selectivity and stability. It was resulted that the Ag microplate sensors have terrific response performances. Their detection linear region is 50μmol·dm^-3 25 mmol·dm^-3, and detection limit is as low as 13.8μmol·dm^-3. High selectivity and stability were also proved by the experiments. There are several advantages of the non-enzymatic sensor, one of the vivid examples is its high sensitivity and wide detection region properties with low construction cost..（3） Rapid synthesis of Pd nanoparticles with controllable morphologies by tunable conditions was performed, as well as their SERS and electrocatalytic properties. Various additives were utilized to prepare the Pd nanomaterials with different morphologies, such as pentacle, concave cube, thorn, waxberry, and large waxberry. The as-prepared Pd nanomaterials were applied in the HCOOH electrochemical oxidation experiments. It was summarized that thorn and waxberry particles were outstanding among these Pd nanomaterials by comparison of the catalytic activities, efficiency, and stability. Therefore, the two materials are the potential anodic catalysts for direct formic acid fuel cells. At the same time, SERS experiments were also carried out to identify the best SERS substrate based on the Pd nanomaterials. It was demonstrated that the strongest SERS signal was from the substrate fabricated by the concave cube. This was relevant to the SERS favored structure and the observed SPR band in the UV-vis spectrum. （4） In situ SERS technology was employed to the systematic investigation of molecular adsorption and/or reaction on various electrodes. It offers the basis of exploring the nanostructures / solutions surfaces at molecular level. Molecules with triple bonds were intentionally selected due to their sensitivity towards the surface structures and electric fields. A series of these molecules, such as 2, 3, 4-CP isomers, 2-amino-5-cyanopyridine, 4-aminobenzonitrile, and phenylacetylene were investigated by SERS combining with electrochemical cyclic voltammetry method. Adsorption information was obtained from the surfaces of the noble metals and transition metals, for instance, Au, Pt, and Pd. It was found that the adsorption of these molecules was heavily depended on the electrodes, potentials, positions of substituted group, and the number of functional groups. Surface reactions of phenylacetylene and 4-aminobenzonitrile were also shown in the extreme negative potentials. In a word, molecules with rings and triple bonds render rich spectral information for resolving the surface behavior in the electrochemical field.更多还原