Ultrafast Dense Immobilization of Noble Metal Nanoparticles on Customizable Multifunctional Polymer Microspheres for Heterogeneous Catalysis and Multiplexed Biodetection

ABSTRACT Constructing colloidal particles into designated hierarchies with integrated functionalities offers insights into bottom‐up material fabrication. However, the arbitrary and controllable assembly of individual nanoscale and microscale particles remains highly challenging due to their diverse structural properties. Here, a general paradigm for the robust co‐assembly of plasmonic noble metal nanoparticles and multifunctional polymer microspheres through thermodynamically driven heterocoagulation and coordination interactions is developed. Monodisperse poly(styrene‐co‐maleic anhydride) microspheres (PSMA MSs) are facilely synthesized using a one‐step emulsification method with optional simultaneous encapsulation of magnetic and fluorescent nanoparticles. Upon surfactant removal, the purified PSMA MSs become metastable and trigger ultrafast co‐assembly of silver nanocubes (AgNCs) onto MSs within 5 min with the maximum coverage rate reaching nearly 50%. The densely immobilized AgNCs outside magnetic MSs exhibit excellent catalytic efficiency (>89% conversion across 15 cycles) and enable enzyme integration for cascade reactions. Moreover, the largest reported plasmonic‐fluorescent encoded array (124 codes) is realized, achieving a significantly improved detection limit of 10 copies/reaction for respiratory viruses. This work addresses the long‐standing challenge of achieving uniform distribution and dense immobilization of plasmonic noble metal nanoparticles and offers a general approach to fabricating designated hierarchies based on noble metal nanoparticles, with integrated functionalities for high‐performance practical applications.