Seeded growth is one of the most successful and well-studied methods of making nanorods of face-centered cubic (FCC) metals such as Ag, Au, Pt, etc. In this method separately prepared tiny metal seeds (typically smaller than 10 nm) are added to a growth solution containing metal precursor, a weak reducing agent such as ascorbic acid, and a capping agent. The mechanisms that lead to specific shape selection and growth of nanoparticles, in this method, are poorly understood. We propose a mechanism of nanorod growth based on the physical phenomenon of twinning and develop a population balance based model. Briefly, on mixing with growth solution, the seeds start growing isotropically, during which some of the seeds undergo twinning and transform their growth habit to form nanorod nuclei. The nanorod nuclei grow along one dimension to form nanorods, and a mixture of nanorods and nanospheres is obtained after a short aging time (typically < 3 h). The simulations capture the salient features of one-dimensional growth of nanorods, along with the kinetics. The trends in experimental data are reproduced well by this model, and we are able to predict the yield of nanorods. Simulations also reveal that the growth of nanospheres competes with the nucleation and growth of nanorods; their relative magnitudes decide the yield of specific shapes in the system. The model is quite general and will apply to the seeded growth of nanorods of any material that has an FCC crystal structure.

中文翻译：

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通过种子生长形成金纳米棒：机理和模型。

种子生长是制造面心立方（FCC）金属（例如Ag，Au，Pt等）的纳米棒的最成功且得到充分研究的方法之一。在这种方法中，单独制备了微小的金属种子（通常小于10 nm）。将其加入到含有金属前体，弱还原剂（例如抗坏血酸）和封端剂的生长溶液中。在这种方法中，导致特定形状选择和纳米粒子生长的机理了解甚少。我们提出了一种基于孪生的物理现象的纳米棒生长机制，并建立了基于种群平衡的模型。简而言之，在与生长溶液混合后，种子开始各向同性生长，在此过程中，一些种子会发生孪生并转变其生长习性以形成纳米棒核。纳米棒核沿一维生长以形成纳米棒，在较短的老化时间（通常<3小时）后获得纳米棒和纳米球的混合物。模拟捕获了纳米棒一维生长的显着特征以及动力学。该模型很好地再现了实验数据的趋势，并且我们能够预测纳米棒的产率。模拟还表明，纳米球的生长与纳米棒的成核和生长竞争。它们的相对大小决定了系统中特定形状的产量。该模型非常笼统，将适用于具有FCC晶体结构的任何材料的纳米棒的种子生长。该模型很好地再现了实验数据的趋势，并且我们能够预测纳米棒的产率。模拟还表明，纳米球的生长与纳米棒的成核和生长竞争。它们的相对大小决定了系统中特定形状的产量。该模型非常笼统，将适用于具有FCC晶体结构的任何材料的纳米棒的种子生长。该模型很好地再现了实验数据的趋势，并且我们能够预测纳米棒的产率。模拟还表明，纳米球的生长与纳米棒的成核和生长竞争。它们的相对大小决定了系统中特定形状的产量。该模型非常笼统，将适用于具有FCC晶体结构的任何材料的纳米棒的种子生长。