【作者】 唐祥虎；

【导师】 刘锦淮； 杨良保；

【作者基本信息】 中国科学技术大学 ， 材料物理与化学， 2014， 博士

【摘要】 得益于纳米技术的快速发展,近些年来,基于纳米敏感材料的敏感元器件与传感技术相结合所构筑的纳米传感器,成为纳米材料科学技术和传统传感技术交叉渗透而开辟的新领域,为新型传感器的制作提供了许多新理念和新方法。其中,基于表面增强拉曼光谱(surface-enhanced Raman spectroscopy, SERS)技术的光纳米传感器是新型传感器领域比较活跃的一个分支。对于SERS技术的发展而言,针对不同的需求设计和制备各种各样的SERS基底一直是SERS领域最重要的研究内容。总的来说,SERS基底材料的稳定性、可控性、可重复性等普适性问题是SERS用于定性分析向定量分析发展的基础条件,研究方法学是必要条件,而应用需求是目标导向。基于此,随着各种纳米结构构筑方法的出现,以及对可靠、可控的SERS活性基底的迫切需要,借助于协同组合化学的研究思想,设计和制备具有极大电磁增强的复杂或组合结构基底成为SERS领域一个重要的研究方向。这里所说的复杂或组合结构SERS基底是指一种或多种纳米单元,通过物理或化学的方法,形成SERS效应及其他性能较独立纳米单元显著改善的复合体系,从而能够更好地满足各种不同的应用需求。另外,在应用领域,随着SERS技术的发展,人们期望SERS的实际应用能在多方面崭露头角,如用于环境检测、与表面科学交叉和结合的催化反应的原位实时监测等。因此,本论文围绕复杂结构SERS基底的设计与构筑及其用于环境检测和催化监测开展了以下几个部分的工作：1)设计并构筑了一种基于金纳米颗粒嫁接二维a-Fe2O3枝晶的复杂结构SERS基底,详细表征了该SERS基底的结构和性能特征,并研究了将其用于农药残留的原位检测。首先,通过水热法合成了二维a-Fe2O3枝晶,并用电感耦合等离子体(inductively coupled plasma, ICP)进行表面改性处理,然后通过3-氨丙基三甲氧基硅烷(3-Aminopropyltrimethoxysilane, APTMS)使大量的氨基修饰到a-Fe2O3枝晶的表面,最后通过氨基和金之间的静电吸引作用,实现金纳米颗粒(Au nanoparticles, Au NPs)的高密度修饰,从而得到金纳米颗粒嫁接二维a-Fe2O3枝晶(Au NPs grafted on dendritic alpha-ferric oxide, NPGDF)复合材料。单粒子的NPGDF具有微米尺度,其轮廓可通过拉曼光谱仪的光学显微镜(optical microscope, OM)平台进行观察,即其具有光学显微可见的特点。以单粒子的NPGDF为基底进行区域SERS成像(SERS mapping)研究,发现其SERS mapping与光学图像(OM image)、电镜(electron microscope, EM)成像以及元素的面扫描能谱图(elemental mapping of EDS area scanning)具有一致性,表明NPGDF在用作SERS基底时的高均一性,从而保证了在光学平台下进行SERS检测时激光束能作用在有效的位点。此外,NPGDF可以在水、乙醇等常规溶剂中进行分散且NPGDF微粒可以吸附到一些物质表面,因此,NPGDF可用作茶叶、水果等表面农药残留的原位检测,且具有较高的灵敏度和重复性。2)制备了金纳米棒包覆四氧化三铁(Fe3O4@NRs)磁性微纳颗粒SERS基底,详细表征了其结构和性能特征。首先,利用溶剂热法合成了Fe3O4磁性微纳颗粒,然后用聚丙烯酸钠和聚乙烯亚胺对其表面进行改性,使其表面氨基功能化；通过种子生长法得到了长径比为～4的金纳米棒,然后用PVP对其表面进行修饰。两者通过静电作用使金纳米棒密集地包覆在Fe3O4微纳颗粒表面。研究结果表明,以近红外为激发光源,Fe3O4@NRs表现出很好的SERS增强效应,同时这种基底具有顺磁性,可借助于外磁场对基底进行操纵组装等。将其进一步用于福美双农药的SERS检测,也表现出较好的检测效果。特别是,将该基底悬浮液喷洒在福美双农药污染过的果皮便面,使其与果皮表面的农残作用后,可在外磁场作用下实现从果皮表面到玻片表面的转移,避免了水果表皮强荧光信号的干扰,且可利用便携式拉曼光谱仪实现对果皮表面农残的快速检测。3)用单颗粒SERS技术来研究表面催化反应动力学仍是一项具有挑战性的难题。我们设计了一种简单的湿化学方法来合成具有微纳分级结构的单分散银颗粒,通过对相关实验条件的控制,我们可以调控颗粒的尺寸大小和表面形貌,并详细研究了微纳银单颗粒的SERS增强效应及其用于原位监测4-硝基苯硫酚(4-nitrothiophenol,4-NTP)在表面等离子体光催化条件下二聚为偶氮衍生物(4,4’-dimercaptoazobenzene, DMAB)的相关性能,同时,探讨了反应的动力学过程。另外,不同反应条件下得到的单颗粒用于催化反应的表观反应速率常数(k)也进行了比较研究。研究结果表明,纳米结构发育完全的牡丹花状微纳银(hierarchical peony-like silver microflowers)单颗粒具有最强的SERS效应和最大的表观反应速率常数。4)设计并构筑了毛细管内壁纳米金多次组装结构微环境催化反应器,揭示了不同组装次数对SERS效应和催化活性的影响,详细研究了在不同组装次数结构中用SERS技术原位监测4-NTP催化还原为4-ATP的反应过程,并探讨了反应的动力学。结果表明,从SERS增强效应来看,3次组装结构增强最显著,2次组装、4次组装次之,1次组装相对最弱。从均一性和稳定性来看,2次组装最佳,3次、4次组装次之,1次组装则相对较差。因此,以SERS的综合性能考虑,以2～3次组装为宜。从不同次数组装结构用于原位监测催化反应的结果来看,随着组装次数的增加,催化速率明显加快,显示出催化活性与SERS性能随组装结构变化的趋势不同,同时表明毛细管内壁纳米金多次组装结构反应器用于原位监测催化反应动力学具有一定的优势,为SERS技术监测催化反应作了进一步拓展。更多还原

【Abstract】 In recent years, it benefited from the rapid development of nanomaterials science and nanotechnology, the combination of sensitive element based on sensitive nanomaterials and sensor technology formed nano sensor, which opens up new areas for the production of the new sensor as well as provides a number of new ideas and new methods. Among numerous new type sensors, optical nanosensor, which based on surface enhanced Raman spectroscopy (SERS) technology, is a new active frontier for researchers. As to the SERS development, design and construction of all kinds of SERS substrates for the different requirements are the most important research title. In general, the universality problems such as the stability, controllability and repeatability of the SERS substrates are the basic conditions for the qualitative and quantitative analysis, the research methodology is necessary condition, and and application requirements is goal oriented. Based on this, with the emergence of various nanostructures building methods, as well as the urgent requirements of reliable, controllable SERS active substrates, design and construction of complex structure SERS substrate with reat electromagnetic enhancement by means of synergistic combination of chemical research have become an important research direction in the field of SERS. Here, complex structures SERS substrates refers to one or more units, through physical or chemical method, used to form composites with significantly improved performance, which can better satisfy various application requirements. In addition, in the field of application, with the development of SERS technology, people expect the practical application of SERS can be extended to other aspects, such as for environmental detection, and as catalysts combined with in situ real-time monitoring of the catalytic reaction.Herein, in this thesis, many complex structure SERS substrates have been designed and constructed, and their applications in environmental detection and catalysis research work were carried out by the following several parts:1) Au nanoparticles (NPs) grafted on dendritic α-Fe2O3(NPGDF) is designed as highly uniform SERS substrate with a feature of optical visualization by optical microscope (OM) system and used for in situ detection of pesticide residues that are annually used in agriculture. With this strategy, the dendritic a-Fe2O3has been synthesized by hydrothermal method and significantly functionalized by an inductively coupled plasma (ICP) apparatus and then Au NPs were grafted on it densely and uniformly. In addition, the profile of NPGDF can be observed by OM platform of Raman spectrometer clearly, and the profile of SERS mapping with NPGDF as substrate almost exactly coincides with OM image, electron microscope (EM) image and elemental mapping of NPGDF, which indicates the remarked uniformity of the NPGDF as SERS substrate, thus it can ensure the laser beam focus on the efficient sites of the substrate under OM platform. Moreover, NPGDF can be dispersed in the liquor and the NPGDF microparticles can be adsorbed on target surface. Therefore, it can be used for in situ detection of pesticide residues on tea leaves, fruits and so on with high sensitivity and reproducibility.2) Au nanorods coated Fe3O4(Fe3O4@NRs) microspheres were designed as functional SERS substrate with a feature of magnetic property and used for detection of pesticide residues that are annually used in agriculture by near-infrared (NIR) excitation. With this strategy, the Fe3O4microspheres were synthesized by hydrothermal method and surface functionalized with polyethylenimine (PEI), and then coated with Au nanorods densely. The Raman spectra were carried out by NIR excitation and4-ATP was chosen as the probe molecule. The results showed a good SERS activity of the Fe3O4@NRs microspheres. Moreover, this substrate could be used for pesticide analysis by portable Raman spectrometer with NIR excitation. Especially, the microspheres could be transferred from pesticides contaminated fruits peel to specially cleaned glass slide with the aid of the external magnetic field, by which the strong fluorescence of the apple components can be avoided while performing the pesticide analysis of fruits peel.3) Investigating the kinetics of catalytic reactions with SERS on a single particle remains a significant challenge. The aim of this part of the study was to develop an efficient platform for researching the process of plasmon-driven surface catalyzed reaction of4-nitrothiophenol (4-NTP) dimerizing into4,4’-dimercaptoazobenzene (DMAB). We firstly synthesized monodisperse and hierarchical peony-like silver microflowers assembled by nanostructures with tailored surface topographies in the absence of any other surfactants. The single particle of the constructed hierarchical silver microflowers with highly roughened surface led to the coupling of high catalytic activity with a strong SERS effect, which own to an excellent bifunctional platform for in situ monitoring of surface catalytic reactions. The kinetics of the reaction of4-NTP dimerizing into DMAB was investigated and comparative studied by using SERS technique on single particle of different morphologies. The results indicate that fully developed nanostructure of hierarchical silver micro flower has both larger SERS enhancement and apparent reaction rate constant k, which may be useful for monitoring and understanding the mechanism of plasmon-driven surface catalyzed reactions.4) Microenvironment catalytic reactors of Au NPs multi-assembled on the inner wall of capillary were designed and constructed. This part discussed the impacts of the number of assembly processes on the SERS effect and the catalytic activity. The assembled nanostructures on the inner wall of capillary were used for in situ monitoring of catalyzed reduction of4-NTP to4-ATP, and the reaction kinetics were also studied. The research results show that, from the perspective of the SERS enhancement effect, the triple-assembled nanostructure exhibits the most significant enhancement effect, twice-assembled comes second, followed by fourth-assembled and first-assembled nanostructures. From the point of view of homogeneity and stability, twice-assembled nanostructure perform best, triple-assembled is next, fourth-assembled comes third, and first-assembled nanostructure is relatively poor. Therefore, to consider in comprehensive performance for SERS, twice-and triple-assembled nanostructures are advisable. From the results of different assembled nanostructure for in situ monitoring of catalytic reaction, with the increase of number of assembly, catalytic rate become significantly faster, which reveals that the catalytic activity and SERS performance show different trends of variation.And it is also suggested that microenvironment catalytic reactors of Au NPs multi-assembled on the inner wall of capillary for in situ monitoring of catalytic reaction kinetics have certain advantages.更多还原