Dendritic structures are widely present in nature, from river networks to snowflakes. There is a long-term interest in discovering their common formation mechanism, especially the driving force leading to the branching and the reason to keep symmetry. The inhibition of lithium dendrites in secondary batteries also calls for the deep understanding on the formation of dendritic structures. Here in this article, we report an investigation on the driving force of the formation of dendritic structures. Silver particles are synthesized by Galvanic replacement reaction (GRR) in which metal rods are immersed into the silver nitrate solution to reduce silver ions followed by silver particles formation on the surface of rods. The silver ions concentration profile near the rods is measured by Mach-Zehnder interferometer during the reaction. It is found that the formation of silver dendritic particles is accompanied by the interface concentration gradient. A regulation on the gradient leads to the change of silver morphology, experimentally confirming the dominant role of the interface concentration gradient in the formation of diverse structures.

从河网到雪花，树状结构广泛存在于自然界中。长期以来，人们一直在寻找它们的共同形成机理，尤其是导致分支的驱动力以及保持对称性的原因。对二次电池中锂树枝状晶体的抑制也要求对树状结构的形成有深入的了解。在本文中，我们报告了对树状结构形成的驱动力的研究。银颗粒是通过电流置换反应（GRR）合成的，其中金属棒浸入硝酸银溶液中以还原银离子，随后在棒表面上形成银颗粒。在反应过程中，通过马赫-曾德尔干涉仪测量棒附近的银离子浓度分布。发现银树突状颗粒的形成伴随有界面浓度梯度。梯度的调节导致银形态的变化，通过实验证实了界面浓度梯度在不同结构形成中的主导作用。