【作者】 赵丽丽；

【导师】 杨文胜；

【作者基本信息】 吉林大学 ， 物理化学， 2010， 博士

【摘要】 近年来,金、银纳米粒子因其独特的结构、性质以及良好的生物相容性而受到人们广泛的关注,并应用于生物医学领域中。目前关于金、银纳米粒子的水相合成及形貌控制报道很多,对于其形成机制也有一定的认识,但正如纳米粒子水相合成中,人们对水分子作用的忽视一样,由反应物不可避免引入的元素对纳米粒子的形成,尤其是粒子形貌的影响,一直没有引起广大研究者的注意。本论文在金、银纳米粒子的合成过程中,深入研究了反应体系的动力学过程,探索Cl-对纳米粒子形貌的调控机制,从而有效控制产物的形貌。首先利用种子生长法制备金纳米花为模型体系,在较宽的pH值范围内(4.2~11.0),系统、定量的研究了金纳米花的生长动力学,发现由Cl-诱导的粒子内熟化作用是影响形貌和稳定性的重要因素,并且可以通过提高pH值抑制Cl-的熟化促进作用。反应过程中通过简单地调节pH值可以调控金纳米花的形貌,反应后提高pH或除去Cl-就可以使金纳米花长期稳定。其次以球形银为种子,以HAuCl4/NH2OH的混合溶液为生长溶液,制备空心的Ag/Au纳米结构,并在较宽的pH范围内(4.2~12.5)监测其反应过程,发现Cl-的存在是粒子形貌调控中不可忽略的因素。当生长溶液的pH值较低时(4.2~10.3),Cl-的存在会导致AgCl的生成,从而抑制了金属离子的进一步还原和沉积,形成了不规则的空心Ag/Au纳米结构。通过提高反应体系pH(10.6~12.5),可以抑制AgCl对金属离子还原和沉积过程的不利影响,得到具有空心结构的Ag/Au纳米花。最后研究了Cl-及与Cl-相关的其他离子(Br-、I-、OH-、Ag+)对种子法制备金纳米花和柠檬酸钠还原法制备金纳米粒子体系的影响。研究结果进一步证明了Cl-、Br-、I-等卤素离子对粒子内熟化的促进作用以及OH-、Ag+等对粒子内熟化的抑制作用,并且这种促进及抑制作用会随着添加剂浓度的增加而增大。制备过程中可以通过促进和抑制熟化实现对粒子形貌的调控。更多还原

【Abstract】 Recently, gold and silver nanoparticles, two of the important noble metals, have been extensively studied as active components in a wide variety of fundamental researches and technical applications due to their unique structures, optical, electric, catalytic properties and biocompatibility. Great efforts have been devoted to control the size and shape of the metal nanopaticles since it is well documented that their properties are both size- and shape-dependent. Many publications about the synthetic methods of the gold and silver nanoparticles have been reported. For example, many people utilized sodium borohydride or sodium citrate as the reducing agent to synthesis the gold or silver nanoparticles in one step. The nanoparticles with monodisperse dimension can be tuned from several nanometers to a few dozens. Other people fabricated the nanoparticles/composites with solid/hollow interior using seeding approach. Many perspectives about the growth mechanism have been proposed in the literature, such as nucleation-growth, aggregation and ripening. In addition, the organic molecules and some inorganic ions have been found to affect the morphology of the nanoparticles. For instance, some researchers utilized CTAB as the template to synthesize gold nanoparticles with anisotropic structures. And other researchers also reported that inorganic ions, such as silver ions and iodine ions, can manipulated the shape of the nanoparticles. However, just like water effect was neglected for synthesis of nanoparticles in the aqueous solution, the effect of some inevitable factors introduced by reactants for the synthesis as well as shape-control of the nanoparticles has not been taken into account.In this dissertation, the growth kinetics of the gold and silver nanoparticles was investigated systematically and quantitatively. The effect of Cl- on the synthesis of nanoparticles were revealed and used to effectively manipulate the shape of the nanoparticles.1、The seeding approach for preparation of gold nanoflowers in which 25 nm gold nanoparticles were used as the seeds and mixture of HAuCl4 and hydroxylamine as growth solution were investigated systematically. It is revealed that the formation and stability of the nanoflowers were affected greatly by the intraparticle ripening induced by the chlorine ions existed in the reaction system. In this seeding approach, hydroxylamine promoted the rapid reduction of HAuCl4 and thus rapid formation of small Au particles with diameter around 3 nm in the growth solution. The attachment of the small particles on the seed surface contributed to the growth of the nanoflowers. The branch length of the nanoflowers increased with the increased pH of the growth solution due to the suppressed ripening at higher pH. Stability of the nanoflowers can be improved by increasing the pH of the storing solution and/or removal of the chlorine ions.2、For the reactions to synthesize Ag/Au hollow nanostructures by using silver nanoparticles as the seeds and the mixtures of HAuCl4 and hydroxylamine as the growth solutions, the existence of Cl- is likely to affect the shape of the nanostructures. For the reactions of low pH (4.2?10.3), the hollow Ag/Au nanostructures were irregular in shape due to the suppressed reduction and deposition of metallic precursors induced by AgCl. However, for the reactions of high pH (10.6?12.5), the disappearance of AgCl due to the competition of hydroxyl groups with chlorine ions to Ag+ in the solution facilitated the reduction and deposition of metallic ions, resulting in the hollow Ag/Au nanoflowers.3、We have found the chlorine ions can accelerated the intraparticle ripening and AgCl can suppressed the reducing rate and deposition of the metallic ions in above works. So the Cl- and other related ions were used to control the branch of the gold nanoflowers. It is found that the halide ions accelerated the intraparticle ripening of the gold nanoflowers and the branch can be tuned by simply changing the concentration of the halide ions at high pH. However, the introduction of Ag+ into the reaction solution suppressed the intraparticle ripening and the gold nanoflowers with longer branch were obtained at low pH. These results further proved the understanding for the synthesis of metallic nanoparticles in my previous work.4、In this chapter, the shape control of the nanoparticles using the Cl- and other related ions was applied in the Frens method. It is conclude that the accelerated ripening induced by chlorine ions and suppressed ripening by hydroxyl groups and AgCl were also applicative in Frens method. When the chlorine ions were introduced into the reaction solution, the nanoparticles transformed from ellipsoidal to spherical shape. However, when the hydroxyl groups or Ag+ were introduced into the reaction solution, the nanoparticles became more anisotropic and exhibited as short line and tadpole. Besides, the different reaction time at which the ions were introduced into the reaction solution have greatly effect on the introparticle ripening, thus the formation of the nanoparticles.更多还原