【作者】 赵红；

【导师】 付宏刚；

【作者基本信息】 哈尔滨工业大学 ， 化学工程与技术， 2011， 博士

【摘要】 表面增强拉曼(SERS)技术能够极大地提高表面物种的检测灵敏度,在实时研究分子表面吸、脱附及取向等方面都有独到优势。为深入研究SERS效应的机理、拓宽SERS基底的范畴和SERS技术的应用领域,构筑金属/半导体、金属/金属等复合物作为SERS基底成为SERS研究的热点。单壁碳纳米管(SWNTs)依据其导电性不同,可以分为金属性碳管(met-SWNTs)和半导体性碳管(sem-SWNTs)。本文借鉴传统的制备银胶的方法,将SWNTs的胆酸钠水溶液与硝酸银水溶液混合,以柠檬酸钠为还原剂,采用液相原位还原的方法将银纳米粒子沉积在SWNTs外壁,制备了不同C、Ag原子比的Ag/SWNTs复合体。分析了金属与碳材料间的界面作用对Ag/SWNTs复合体基底的SERS效应的影响。SWNTs与Ag之间的电子转移对Ag/SWNTs的SERS活性有重要的加强作用。为深入研究SWNTs与Ag之间的电子转移对Ag/SWNTs的SERS活性的影响,在成功分离met-SWNTs和sem-SWNTs的基础上,分别制备了Ag/met-SWNTs和Ag/sem-SWNTs。对比研究了Ag/met-SWNTs和Ag/sem-SWNTs的SERS活性。结果表明met-SWNTs较之于sem-SWNTs更易于Ag发生电子转移,因而Ag/met-SWNTs具有更强的SERS活性。采用原位还原的方法在铜箔上制备了不同形貌的银、钯纳米结构,研究表明,通过调控前驱体浓度、表面活性剂种类和浓度可有效控制银、钯纳米结构的形貌。SERS研究表明,这种有序的银、钯纳米结构具有较高的SERS活性,且钯纳米立方体的SERS增强因子可达到3.4×107。立足于铜箔上原位制备不同形貌银钯纳米结构的前期实验,基于原位自生模板法制备的graphene在水中具有较好分散性的特点,将Ag(Pd)负载于graphene上,制备了Ag(Pd)/graphene。即首先将铜纳米粒子负载于graphene片层上,尽管沉积的铜纳米粒子无序、尺寸无规律且团聚程度比较大,但在第二步反应过程中,利用铜与Ag(Pd)离子之间温和的置换反应,graphene片层上沉积的大的铜纳米粒子分别被置换为分散十分均匀、粒径为2nm左右Ag纳米粒子和粒径为3nm的Pd纳米粒子。SERS研究表明,这种Ag(Pd)/graphene具有不同于纯Ag(Pd)纳米结构的SERS效应,推测这可能是由于Ag(Pd)的超小尺寸对介电常数的影响,导致Ag(Pd)本身电磁场的变化引起的,同时与graphene与Ag(Pd)之间的电子转移有关。此外,实验还表明牺牲铜模板制备的Pd/graphene不但具有较强的SERS活性,而且对甲酸有比采用直接还原法制备的Pd/graphene和Pd/Vulcan更强的电催化活性,这使得牺牲铜模板制备的Pd/graphene有望应用于原位电化学拉曼研究。更多还原

【Abstract】 Surface-enhanced Raman scattering (SERS) has greatly improved the detection limits of surface species, which has a unique advantages to study molecular absorption, desorption and orientations in real time. In order to discuss the SERS mechanism furtherly, extend variety of SERS substrates and widen application area of SERS technique, the design and fabrication of a variety of nanoparticles and nanostructures as new SERS substrates are hot topics. Recently, high-quality SERS signals have been observed in composite systems such as metal core/shell nanoparticles and metal-semiconductor composite.Single-walled carbon nanotubes (SWNTs) can be classified into metallic ones (met-SWNTs) and semiconducting ones (sem-SWNTs). The Ag/SWNTs with different ratio of C: Ag was synthesized by a facile one-step approach using the sodium citrate as reducing agent, developing the classical preparing method of silver-sol system. The effect of interfacial action between Ag and SWNTs on SERS activity of Ag/SWNTs was analyzed. It was concluded that the charge-transfer between Ag and SWNTs enhanced SERS activity of Ag/SWNTs. To deepen the study of the effect of charge-transfer between Ag and SWNTs on SERS activity, Ag/sem-SWNTs and Ag/met-SWNTs were fabricated, respectively. The effect of charge-transfer between Ag and SWNTs on SERS activity of composite was verified via the contrastive studies of them.Ag dendrites, size-controlled Pd nanocubes, hexagonal prism and Pd dendrites nanostructures were synthesized by a simple galvanic displacement process between Ag (Pd) ion and Cu. The sizes and morphology of Pd nanostructures could be controlled by simply regulating the reaction parameters, such as concentration of palladium dichloride, reaction time and types of surfactant. A possible formation mechanism of Pd nanocubes was also briefly discussed. Furtherly, SERS investigation demonstrated the nanostructures on copper foils were SERS-active. The SERS enhancement factor (EF) values for PATP on Pd nanocubes was about 3.4×107. Based on the excellent dispersion of the graphene obtained by“in situ self-generating template”route and the previous studies of fabrication of Ag dendrites, Pd nanocubes and Pd dendrites were obtained on Cu plate. Ag (Pd) was supported on graphene via Sacrifice Cu templet. Firstly, Cu was supported on graphene sheets, and it was negligible, whether the CuNPs shall be aggregated or not. Then, Ag (Pd) NPs supported on graphene sheet were fabricated via galvanic displacement process between Ag (Pd) ion and the Cu. In his way, though Cu nanoparticles (Cu NPs) on graphene sheets were aggregated in the first step, the obtained Ag (Pd) NPs on graphene sheets should be in good dispersions via a moderate replacement reaction. Successfully, something expected and unexpected has turned up, that the big-sized Cu NPs have magically been transformed into small-sized and high-dispersed Ag(Pd)NPs supported on graphene nanosheets in the absence of stabilizers. The study showed the small-sized Ag (Pd) NPs possess SERS activity which is different from Ag nanostucture. The electromagnetic field of small-sized Ag NPs is different from big-sized Ag (Pd) NPs, for the small-sized Ag NPs would lead to the change of dielectric constant of Ag (Pd) NPs. Moreover, the SERS activity of Ag (Pd)/graphene hybrid is relevant to the charge-transfer between Ag (Pd) and graphene. The obtained Pd/graphene hybrid exhibited more significant catalytic activity for formic acids oxidation than Pd/graphene and Pd/Vulcan obtained by one-step procedure that Pd ions were reduced with NaBH4 directly. Thus, the Pd/graphene hybrid should be applied to in-situ electrochemical SERS promisingly.更多还原