【作者】 焦正波；

【导师】 陶绪堂； 夏海兵；

【作者基本信息】 山东大学 ， 材料学， 2011， 博士

【摘要】 纳米材料所特有的表面效应、量子尺寸效应、量子隧道效应等诸多特殊的效应,使其具有不同寻常的光学、电学、磁学、热学、力学、化学活性、催化以及超导等性能,从而使其在电子、国防、化工、航空、轻工、冶金、核技术、陶瓷、催化剂和医药等领域都具有十分重要的应用前景,它已然成为现在材料研究领域中最前沿、最热门的新领域。对于以金、银、钯等为代表的贵金属而言,以其所具有的特殊的物理、化学性质与纳米技术的相互结合,使其拥有了非比寻常的特性,从而展现出极具吸引力的应用前景。金纳米晶是一种研究时间较长,应用范围较广的纳米粒子,因其在光学材料、生物、医药、光催化、贵金属浆料、微电极反应、催化工业和微电子工业等方面的广泛应用而引人瞩目。纳米金以其独特的物理、化学性质和广泛的应用前景而成为纳米技术中一颗璀璨的明珠,有“绿色纳米技术中的关键元素”之称。纳米粒子的控制生长一直是纳米材料研究中的难点、热点和前沿,通常人们希望纳米粒子的形状和尺寸是可以控制并且稳定的。目前用于制备金纳米晶的方法有很多种,方法相对比较成熟,并且人们仍在进行不断地研究金纳米晶的生长动力学以期改进制备方法。在实际应用中可以根据介质环境、颗粒要求的尺寸以及金纳米晶的用途来选择合适的制备方法。已报道的可以控制生长的金纳米晶体有球形、三角形、六边形、立方形及棒状等,目前报道较多的是棒状金纳米晶的研究。与制备均匀、单分散的球形金纳米晶相比,棒状金纳米晶的合成要困难得多,曾经在很长一段时间对棒状金纳米晶的尺寸和形貌难以实现有效的控制。本论文采用种子诱导的化学还原法制备金纳米棒,并系统的研究了多种因素对金纳米棒尺寸及形貌的影响。研究表明：十六烷基三甲基溴化铵(CTAB)的浓度对金纳米棒的影响较大,其浓度太低难以制得棒状的金纳米晶,而浓度太高又会形成金纳米球影响金纳米棒的产率；硝酸银的含量对金纳米棒的形成也起着至关重要的作用,硝酸银含量太低则无法保证金棒沿[100]方向长大,得到的金纳米棒纵横比太小,而含量太高则会大量的吸附在其他晶面上阻碍金纳米棒的长大,从而导致形成球形金纳米晶；抗坏血酸(AA)的主要作用是还原氯金酸,在AA的量足以还原全部氯金酸的条件下,AA浓度的变化对金纳米棒形貌的影响不大；通过调节氯金酸的含量,可以实现金纳米棒的纵向表面等离子共振吸收峰在640nm到833nm之间连续调谐,同时可以得到纵横比在2.27到3.52之间的金纳米棒；通过调节碘离子的含量,可以在金纳米棒与金纳米球之间进行光谱及形貌的连续调控,并且得到的球形金纳米晶大小比较均匀；此外,种子的量和搅拌时间对金纳米棒的影响都不大。尺寸、形貌、结构及组成是影响了金纳米晶光学、电学、磁学及催化等性能的关键因素,因此设计、控制金纳米晶的形貌一直是金属纳米材料领域的研究重点。本论文研究了在以金纳米棒作为种子进行过度生长的过程中,碘离子和银离子对其形貌及光谱的影响。通过研究发现当生长溶液中存在微量碘离子的时候可以制得哑铃状的金纳米晶,而通过调节银离子的含量,则可以分别制备长方体、狗骨状和“Ⅰ”状的金纳米晶。我们通过分析碘离子在金纳米棒晶面的吸附及银离子的欠电位沉积理论对上述金纳米晶的形成机理进行了阐述。此外,我们利用碘离子和银离子对金纳米棒的影响作用,通过让二者在生长溶液中共存并调节两者之间的比例实现了金纳米晶从哑铃状到狗骨状之间形貌及光谱的连续调控,并且发现微量碘离子的存在可以促进了狗骨状金纳米晶两端凸起部分的生长,从而获得了制备狗骨状金纳米晶的最佳条件。我们通过改变作为种子的金纳米棒的长径比,实现了对第三个表面等离子共振吸收峰的调控,当第三个表面等离子共振吸收峰的强度超过纵向表面等离子共振吸收峰的时候,相对应的金纳米晶的形貌为四角星状。通过制备金铂核壳结构的纳米晶并调节氯亚铂酸钾的含量,实现了在纳米晶尺寸变化不大的条件下对纵向表面等离子共振吸收峰的大幅度调控,在长度变化小于5nm直径变化1nm左右的情况下,其纵向表面等离子共振吸收峰从800nm到955nm之间连续可调。从而最终实现了金纳米晶的纵向表面等离子共振吸收峰从520nm到955nm的连续调控,为拓展金纳米晶体的应用范围奠定了基础。此外,我们还制备了一系列具有电催化性能的狗骨状的Au@Au-Pt、Au@Au-Pd及Au@Pt-Pd等核壳结构的合金纳米晶体,并测试了它们对甲醇的电催化性能。更多还原

【Abstract】 Nanomaterials have broad application prospects on national defense, electronics, chemical industry, metallurgy, light manufacturing, aviation, ceramics, nuclear technology, catalyst, medicine because they have excellent mechanical, electrical, magnetic, optical, chemical activity, catalytic and superconductivity properties due to their unique surface effect, quantum size effect and macroscopic quantum tunneling effect, and so on. Nanotechenology has been one of the most front and hot topics. Nobel metals such as gold, silver, and copper, which combined their chemical and physical properties with nanotechnology, have shown attracting potential applications because of their outstanding properties.Gold nanocrystals (Au NCs) have attracted much attention because of their potential applications in many fields such as optical materials, photocatalysis, microelectrode reactions, sizing agent, biological, medicine, catalyst and microelectronics. Au NCs which was called key factor of green nanotechnology has been the bright phearl of nanotechnology. The difficult, hot and front point of nanomaterials is the preparation of nanocrystals under control. It is expected to control the shape and size of nanocrystals. There are many methods to synthesis the Au NCs and great improvement have been achieved due to the investigation of dynamics. Proper means can be chosen depending on the environment, requirement and purpose. The morphology which has been reported of Au NCs includes spherical, triangle, hexagon, cubic and rod. Compared with uniform and monodisperse spherical nanocrystals, gold nanorods (Au NRs) is difficult to be synthesized with controlled morphology and size.We prepare Au NRs with seed-mediated methods, which reduce the gold ions. A series of factors on the morphology and size of Au NRs have been studied. It has been demonstrated that the concentration of CTAB has great effect on the Au NRs. It is difficult to prepare Au NRs under low concentration of CTAB and the yield could be reduced if the concentration of CTAB is excess. The concentration of silver ions is also quite important on the formation of Au NRs. The aspect ratio is small if the concentration of silver ions is too low and many spheres will be formed if the concentration of it is too high. The major function of AA to reduce gold ions and it has little effect on gold nanorods if only the amount is enough. The plasmon resonance could be tuned between 640nm and 833nm, and the aspect ratio could be tuned between 2.27 and 3.52 by controlling the concentration of gold ions. The morphology and plasmon resonance could be tuned between sphere and rod by controlling the iodide. Moreover, the amount of seeds and stirring time has little effect on Au NRs.Size, morphology, structure and component are key factors, which could affect the optics, electrics, magnetics and catalysis properties of Au NRs. We investigate the effect of iodide and silver ions on Au NRs during the overgrowth of it. It has been discovered that dumbbell-like Au NCs could be produced if there exists iodide in the growth solution and dogbone-like Au NCs will be gotten if silver ions exist. The mechanism has been explored by adsorbing of iodide and Under Potential Deposition (UPD) theory of silver.The morphology and plasmon resonance could be tuned between dumbbell-like and dogbone-like Au NCs by. controlling the concentration of iodide and silver ions when they exist simultaneously in the growth solution. It was discovered that small amount of iodide is benefit for the forming of dogbone-like nanocrystals. We have succeeded in tuning the third plasmon resonance by controlling the aspect ratio of dogbone-like Au NCs. When star-like Au NCs with four horns was formed, the intensity of the third peak could exceed the longitudinal plasmon resonance. The plasmon resonance of Au@Pt NCs could be tuned between 800nm and 955nm by controlling the amount of platinum.A series of NCs such as Au@Au-Pt、Au@Au-Pd and Au@Pt-Pd which have excellent catalysis properties have been prepared and the performance of them on oxidizing methanol have been explored by cyclic voltammograms (CVs).更多还原