Size and shape control of metal nanoparticles using dendron ligands

金属纳米粒子的物理和化学性质与它们的大小和形状密切相关，因此对它们的控制在基础研究和应用中都非常重要。我们尝试用两种不同的系统来控制颗粒大小：微流反应器和反胶束。首先在微流反应器系统中合成了1 ~ 4代氨基焦点基聚苯醚树突配体。这些树突配体与有机金属化合物（醋酸钯，Pd(OAc)_2）在高沸点惰性溶剂（二苯醚，bp）中混合。259℃)，从注射器中推入内径150 ~ 300μm的二氧化硅微流反应器。采用Pd (OAc)_2热分解法制备了Pd纳米颗粒。在该体系中，考察了反应温度、反应器内径、流速、前驱体和配体浓度等流动参数的影响。结果表明：(1)随着反应温度的升高，颗粒粒径从2.7 nm增大到4.8 nm;(2)随着线性流量的增加，颗粒粒径减小，但与体积流量无关。此外，(3)在r=1-2时，颗粒尺寸最小，其中r由枝状大分子与金属前驱体的摩尔比决定。我们还发现，在较宽的金属前驱体浓度范围内（1-27mM），颗粒大小没有变化，并保持良好的单分散性，而在间歇反应器中，随着前驱体浓度的增加，平均粒径和多分散性都显著增加。这意味着微流反应器系统是可行的批量生产尺寸调节的金属纳米颗粒。其次，在有机溶剂中合成了聚苯醚树突，在聚苯醚树突上附着聚乙二醇（PEG）链，用于制备反胶束。由于嗜水/嗜冷平衡（HLB）随PEG链长度(n)的变化而变化，我们从n=6开始。然而，它的长度不足以使水在反胶团中溶解。因此我们合成了具有较长PEG链的树突，n=8和11.5。具有最长聚乙二醇链的树突已被发现在甲苯的反胶束中溶解水。然而，目前尚不清楚这些胶束是否可以作为金属纳米颗粒的储层。少

Physical and chemical properties of metal nanoparticles strongly depend on their size and shape, thus their control is very important in both basic researches and applications. We have attempted to control the particle size by two different systems : microflow reactor and reversed micelle.First in the microflow reactor system, poly (benzyl ether) dendron ligands of generations 1 to 4 with an amino focal group have been synthesized. These dendron ligands were mixed with an organometallic compound (palladium (II) acetate, Pd(OAc)_2) in an inert solvent with a high boiling point (diphenyl ether, bp.259℃) and pushed out from a syringe to a silica microflow reactor with 150-300μm in inner diameter. The Pd nanoparticles were yielded by thermal decomposition of Pd (OAc)_2. In this system, effects of flow parameters, i.e. reaction temperature, inner diameter of the reactor, flow rate, concentrations ofprecursor and ligand, have been investigated. The following results were obtained : (1) The p … More article size increases from 2.7 to 4.8 nm with increasing the reaction temperature, (2) the particle size decreases with increasing linear flow rate but does not depend on the volume flow rate. Moreover, (3) the particle size shows the minimum at r=1-2where r is defined by the dendrimer to metal precursor molar ratio. We found also that the particle size does not vary in a wide concentration range of the metal precursor (1-27mM) with keeping an excellent monodispersity, while in the batch reactor, a significant increase in both the mean particle size and the polydispersity was observed with increasing the precursor concentration. This implies that the microflow reactor system is feasible for mass production of size-regulated metal nanoparticles.Second, poly (benzyl ether) dendrons attached with a polyethyleneglycol (PEG) chain at the focal point were synthesized for making reverse micelles in organic solvents. Since the hydrophil/lyophil balance (HLB) varies with the length of PEG chain(n), we started with n=6. However, it was not long enough to solubilize water in the reverse micelle. Therefore we synthesized the dendron with a longer PEG chain, n=8 and 11.5. The dendon with the longest PEG chain has been found to solubilize water in the reverse micelles in toluene. However, it is not yet clear that these micelles can work as a reservoir for metal nanoparticles. Less