Formation Process of Gold-Silver Hollow Nanostructure via Silver Halide Photographic Techniques: An Electrochemical Model Cell Study (Supporting Information)

The photographic development of AgBr microcrystals yields the formation of silver nanofilaments (pAgNF). Subsequent treatment of pAgNF with a gold(I)-thiourea complex solution results in a hollow nanostructure composed of gold and silver (hAuAgNS). The formation mechanism of the hollow structure is believed to be a galvanic reaction. In this study, we investigated the formation process using a macroscopic electrochemical model cell, where the anodic and cathodic half-reactions are spatially separated, enabling independent control of the conditions in each half-cell. The model cell experiments consistently corroborate the two-step mechanism for hollow structure formation: 1) direct galvanic replacement of silver by gold on the pAgNF surface, giving the gold-covered exterior on pAgNF, and 2) galvanic deposition of gold on the pre-deposited gold surface, accompanied by the dissolution of silver from the gold-uncovered sites (galvanic pitting). The transition of pAgNF to hAuAgNS was further traced through chemical analysis and electron micrographic observation, with discussion and interpretation of the results of the model cell experiments.

AgBr 微晶体的摄影开发导致银纳米丝（pAgNF）的形成。随后，通过使用金（I）硫脲复合溶液对 pAgNF 进行处理，得到由金和银组成的空心纳米结构（hAuAgNS）。空心结构的形成机制被认为是一种电化学置换反应。在本研究中，我们利用宏观电化学模型电池研究了其形成过程，该电池中阳极和阴极半反应在空间上被分离，从而实现了对每个半电池内条件的独立控制。模型电池实验一致证实了空心结构形成的两步机制：1）在 pAgNF 表面直接通过电化学置换将银由金替代，形成覆盖金的 pAgNF 外表面，2）在预先沉积的金表面上进行电化学沉积金，同时伴随着银从金未覆盖区域的溶解（电化学腐蚀）。通过化学分析和电子显微观察进一步追踪了 pAgNF 向 hAuAgNS 的转变，并对模型电池实验的结果进行了讨论和解读。