Liquid-Metal-Driven Synthesis of Mesoporous Noble Metal Thin Films and Micropatterns for Biosensing

Nanoporous thin films (NPTFs) of noble metals are known for their exceptional durability, biocompatibility, and enlarged yet modifiable surface in broad biosensing applications. However, it remains challenging to devise a viable NPTF fabrication method that is generally applicable to different types of noble metals and for generating micro/nanopatterns. Here, we present a liquid-metal-based approach for transforming noble metal thin films and their lithographically formed patterns into NPTFs with mesoscale pores. For this purpose, a gallium (Ga)-based process in the liquid state of the metal is implemented. During fabrication, the noble metal thin films are first converted into compact layers of Ga-containing intermetallic crystals, followed by selective removal of the less noble Ga to create mesoporous networks. Compared to their nonporous counterparts, the noble metal NPTFs exhibit increased electroactive surface area, enhanced current density, and improved antifouling performance, all to a substantial degree, in different biosensing settings. Notably, gold NPTFs demonstrate excellent sensitivity and selectivity toward dopamine in a human serum environment. Given that the fabrication can be carried out at near room temperature and avoids harsh conditions, we expect our method to expedite the use of noble metal NPTFs and patterns in developing high-performance biosensors and other noble metal surface-enabled applications.