表面增强拉曼散射光谱(surface-enhanced Raman spectroscopy， SERS)技术由于具有高的检测灵敏度，样品前处理简单，检测无损伤性，分析速度快，检测成本低，能实现实时原位检测等优势，被广泛应用于化工、环境、食品卫生、生物医学、公共安全等领域。随着纳米技术的发展，磁性纳米材料因其独特的性能被应用于肿瘤治疗、药物靶向输送和细胞分离等方面的科学研究中。若将经典的具有优异SERS活性的贵金属纳米颗粒与磁性纳米颗粒相结合，形成多功能的成磁性/贵金属复合纳米材料，则既具有磁性纳米材料的富集、靶向示踪和分离性能，又具有贵金属优异的SERS和催化性能，从而更好地满足了各领域的应用需求。可控制备出高灵敏度、稳定性和重现性的多功能磁性/贵金属复合SERS基底，具有重大意义。在本论文中，我们通过不同的方法与技术合成多功能的磁性/贵金属复合纳米颗粒，并对其SERS性能及其应用进行探讨。本论文的主要内容如下： 一、利用简单的水热法，一步合成出分散性好、粒径均匀的Ag-Fe₃O₄复合纳米颗粒，并对其性能进行研究。我们选用AgNO₃和Fe(NO₃)₃·9H₂O作为反应前驱体，通过调控加入这两种前驱体的摩尔比，会得到一系列核/壳组成比例不同的Ag-Fe₃O₄复合纳米颗粒。这种多功能的复合纳米颗粒是由银纳米颗粒作为内核，Fe₃O₄磁性纳米颗粒疏松地沉积在外层而形成的核-壳结构。系统地研究了加入的两种前驱体摩尔比的调控，对所得产物的结构、形貌、尺寸、磁性和光学性能的影响。分别从热力学和动力学两个方面，重点探讨了 Ag-Fe₃O₄磁性复合纳米颗粒的形成机制，并给出了相应合理解释。通过所得一系列核/壳组成不同产物的紫外-可见吸收光谱，总结出随着Ag/Fe比例的增加其表面等离子体共振(SPR)吸收带逐渐蓝移。选择罗丹明6G(R6G)和结晶紫(CV)作为拉曼活性探针，对所得产物的SERS性能研究中，发现该多功能的复合纳米颗粒表现出非常高的SERS灵敏度，并且随着Ag/Fe比例的增加，其SERS活性逐渐增强。这种“热点”可控的SERS基底在农残检测、生化分析等方面具有广泛应用前景。 二、以前期制备的Fe₃O₄为基底，利用磁控溅射技术，在其表面沉积一层纳米银颗粒，从而形成Fe₃O₄-Ag复合SERS基底。通过调控磁控溅射的时间(0、 40、70、100、130、160和190s)，可以得到一系列不同银覆盖量的复合物。采用对-氨基苯硫分(p-ATP)和R6G作为拉曼活性探针，对这一系列复合物的SERS性能进行了研究，并总结出随着溅射时间的延长，其SERS活性逐渐增强，溅射时间为130s时得到的SERS基底达到最大的增强效果。通过对该SERS增强基底选定面积内随机光谱的采集及其特征峰的分布图，证明了该SERS基底具有良好的稳定性和重现性。这种具有最强SERS效应的基底用于p-ATP的痕量检测，最低浓度可达1.0×10⁻¹⁰M。最后将该高灵敏度的SERS基底用于农药福美双的检测，检测限达到5×10⁻⁷M。这种SERS基底是固定在硅片上的，便于携带，可应用于复杂环境中农残等的现场快速检测。 三、采用间接合成法，层层组装技术，制备出Fe₃O₄@mTiO₂@Ag和Fe₃O₄@mTiO₂@Au NR两种三组分的磁性SERS增强基底。Fe₃O₄纳米颗粒作为内核和磁源；中间的介孔二氧化钛层比表面积非常大，一方面用于吸附大量的待测分子，另外保证整个复合物的物理和化学稳定性；外层的Ag纳米颗粒和金纳米棒则赋予该复合物优异的光学性能。通过丁胺对硝酸银的原位还原反应在Fe₃O₄@mTiO₂表面沉积大量的银纳米颗粒从而制备出Fe₃O₄@mTiO₂@Ag复合纳米颗粒，Fe₃O₄@mTiO₂表面聚电解质化后与金纳米棒的静电作用制备出Fe₃O₄@mTiO₂@Au NR复合纳米颗粒。分别利用CV、p-ATP和对-巯基苯甲酸(MBA)作为拉曼活性分子，分别对这两种磁性复合基底的SERS性能进行了研究，Fe₃O₄@mTiO₂@Ag复合纳米颗粒对结晶紫和对-氨基苯硫酚的检测限分别为1.0×10⁻⁹M和1×10⁻¹²M，Fe₃O₄@mTiO₂@AuNR复合纳米颗粒对对-氨基苯硫酚和对-巯基苯甲酸的检测限分别为1×10⁻¹⁰M和1×10⁻⁹M，证明了这两种基底具有非常高的SERS灵敏度。通过分别对这两种基底选定区域内任意采集20个点的SERS光谱，对其特征峰强度的相对标准偏差计算，证明了这两种SERS基底具有非常好的稳定性和重现性。最后将Fe₃O₄@mTiO₂@Ag复合SERS增强基底用于农药福美双的检测，检测最低浓度达到5×10⁻⁸M(0.05ppm)，远远低于美国环保部要求水果中的允许含量(7ppm)。这种具有高灵敏度、良好稳定性和重现性的多功能SERS基底在催化、肿瘤治疗、药物靶向输送和细胞分离等方面具有潜在的应用。 四、利用简单、高效的一步水热法制备出Au-Fe₃O₄杂化复合空心球，并对其SERS性能和催化性能进行研究。采用氯金酸和氯化铁作为反应前驱体，通过改变Au/Fe这两种前驱体的摩尔比，即Au/Fe摩尔比分别为0、0.05、0.1、0.2和0.5，可以调节位于杂化复合空心球中Au纳米颗粒的量，从而得到一系列不同银含量的杂化复合空心球。所制备的产物不仅具有非常优异的SERS灵敏度，而且具有很高的催化活性。这种杂化的复合空心球具有非常大的比表面积和SERS活性位点，对表面吸附的R6G表现出非常高的SERS活性，其中Ag/Fe为0.2时所得基底的SERS活性最强，并且对R6G的最低检测浓度可达到1×10⁻¹⁰M。最后这种Au-Fe₃O₄杂化复合空心球在硼氢化钠还原4-氨基苯酚体系中，表现出非常好的催化活性并且可回收反复使用。因此这种多功能的SERS基底在痕量检测和工业废水处理等方面显示出巨大的应用价值。 关键词：多功能 表面增强拉曼光谱 磁性/贵金属复合纳米颗粒痕量检测 福美双

 Surface-enhanced Raman spectroscopy (SERS) technology has the advantage of high sensitivity, simple pretreatment, non-invasive injury detection, fast analysis, low cost and in-situ detection. So it was widely used in chemical, environmental, biomedical, food health, biomedical, public safety and other fields. With the development of nanotechnology, magnetic nanomaterials have been applied to scientific research in tumor therapy, drug targeted delivery and cell separation due to their unique properties. When the classical noble metal nanomaterials with excellent SERS activity are combined with the magnetic nanomaterials to form multi-functional magnetic/noble metal composite nanomaterials, they have both the enrichment, targeting and separation properties of magnetic nanomaterials and excellent SERS, catalytic properties of noble metal nanomaterials, which better meets the application needs of various fields. Therefore, it is of great significance to control the preparation of a multifunctional magnetic/noble metal composite SERS substrate with high sensitivity, stability and reproducibility. In this paper, we use different methods to prepare multi-functional magnetic/noble metal composite nanomaterials, then study their SERS properties and their applications. The main contents of this paper are as follows: 1.Uniform Ag-Fe₃O₄ composite nanoparticles have been obtained via a simple one step hydrothermal route and their properties were studied. AgNO₃ and Fe(NO₃)₃·9H₂O were chosen as the reaction precursors. By adjusting the molar ration of these two precursors, we can obtain a series of Ag-Fe₃O₄ composite nanoparticles with different core/shell composition ratios. The multi-functional composite nanoparticle is a core-shell structure formed by silver nanoparticles as a core and Fe₃O₄ magnetic nanoparticles loosely deposited on the outer layer. The effects of the molar ratio of the two precursors on the structure, morphology, size, magnetic and optical properties of the resulting products were systematically investigated. The formation mechanism of Ag-Fe₃O₄ composite nanoparticles was also discussed from thermodynamics and kinetics respectively, and corresponding rational explanations were given. As shown in the UV-visible absorption spectra of the products, the surface plasmon resonance (SPR) absorption band gradually blue shifts as the Ag/Fe ration increases. Rhodamine 6G (R6G) and crystal violet (CV) were selected as Raman-active probes. In the SERS performance study, the products exhibited very high SERS sensitivity, and their SERS signal gradually enhanced as the Ag/Fe molar ratio increases. This "hot spot" controllable SERS substrate has broad application prospects in pesticide residue detection and biochemical analysis. 2.The Fe₃O₄-Ag composite SERS substrate was prepared by magnetron sputtering silver nanoparticles on the surface of Fe₃O₄ nanoparticles. A series of composites with different silver coverage can be obtained by adjusting the magnetron sputtering time (0, 40, 70, 100, 130, 160 and 190 s). The SERS properties of these composites were studied by using p-aminobenzene sulfide (p-ATP) and R6G as Raman active probes. The SERS signal gradually increased with the sputtering time prolonged, and reached the maximum at the sputtering time of 130 s. The SERS substrates have good stability and reproducibility by collecting the random spectra and the intensity distribution of the characteristic peaks in the selected area. The substrate with the strongest SERS effect is used for trace detection of p-ATP with a minimum concentration of 1.0×10⁻¹⁰ M. Finally, the SERS substrate was used for the trace detection of the pesticide thiram, and the detection limit reached 5×10⁻⁷ M. The SERS substrate is fixed on a silicon wafer and is easy to carry, so it can be applied to on-site rapid detection of pesticide residues in complex environments. 3.Two multi-functional Fe₃O₄@mTiO₂@Ag and Fe₃O₄@mTiO₂@Au NR SERS substrates were prepared by indirect synthesis and layer-by-layer assembly. Fe₃O₄ nanoparticles act as the inner core and magnetic source; the mesoporous TiO₂ in the interlayer has a very large specific surface area, which can adsorb a large amount of molecules and ensure the physical and chemical stability of the entire composite; the outer Ag nanoparticles and gold nanorods impart excellent optical properties to the composites. Fe₃O₄@mTiO₂@Ag was prepared by the in-situ reduction process and Fe₃O₄@mTiO₂@Au NR by electrostatic interaction with polyelectrolyte. The SERS properties of the two composite substrates were studied by using CV, p-ATP and p-mercaptobenzoic acid (MBA) as Raman active molecules respectively. The detection limits of Fe₃O₄@mTiO₂@Ag composite nanoparticles for CV and p-ATP are 1.0×10⁻⁹ M and 1×10⁻¹² M, and Fe₃O₄@mTiO₂@Au NR for p-ATP and MBA are 1.0×10⁻¹⁰ M and 1×10⁻⁹ M, which proved that these two substrates have very high SERS sensitivity. The SERS spectra of 20 points randomly collected in the selected regions of the two substrates were used to calculate the relative standard deviations of the characteristic peak intensities, which proved that the two substrates have high reproducibility and stability. Finally, the Fe₃O₄@mTiO₂@Ag composite substrate was used for the thiram trace detection and the detection limit can reach to 5×10⁻⁸ M (about 0.05 ppm), which is lower than the maximal residue limit of 7 ppm in fruit prescribed by the U.S. Environmental Protection Agency. These versatile SERS substrates with high sensitivity, stability and reproducibility have potential applications in the fields of catalysis, tumor therapy, drug targeted delivery and cell separation. 4.The Au-Fe₃O₄ hybrid composite hollow spheres were prepared by a simple and efficient one-step hydrothermal method, then their SERS properties and catalytic properties were studied. The amount of Au nanoparticles located in the hybrid hollow spheres can be tuned by changing the molar ratio of Au/Fe precursors. A possible synthetic mechanism of the Au-Fe₃O₄ hybrid hollow spheres has been proposed. The obtained hybrids exhibit not only a superior surface-enhanced Raman scattering (SERS) sensitivity, but also an excellent catalytic activity. The obtained hybrid composite hollow sphere has a very large specific surface area and many SERS active sites, so they exhibit very high SERS activity of R6G adsorbed on the surface. The product with Ag/Fe of 0.2 has the strongest SERS activity, and the detection limit for R6G can reach up to 1.0×10⁻¹⁰ M. Furthermore, the catalytic experiments of the Au-Fe₃O₄-0.2 hybrid hollow spheres demonstrate that the model of 4-nitrophenol (4-NP) molecules can be degraded within 3 min and the catalytic activity can be recovered without sharp activity loss in six runs, which indicates their superior catalytic degradation activity. The reason may be due to the highly efficient partial charge transfer between Au and Fe₃O₄ at the nanoscale interface. The results indicate that the bifunctional Au-Fe₃O₄ hybrid hollow spheres can serve as promising materials in trace detection and industrial waste water treatment. Keywords: multi-function, Surface-enhanced Raman spectroscopy, magnetic/noble metal composite nanoparticles, trace detection, thiram