Tunable Plasmonic Response of Silver Nanoparticles Entangled in Detonation Nanodiamond Network via Colloidal Self‐Assembly

Abstract This study explores the self‐assembly of nanocomplexes formed by well‐defined 20‐nm colloidal silver nanoparticles (AgNPs) with 4‐nm detonation nanodiamonds (DNDs), focusing on plasmonic resonance. Water‐diluted DNDs spontaneously aggregate into chain‐like structures entangling AgNPs, forming stable nanocomplexes that sediment within minutes but maintain their plasmonic properties even after redispersion, indicating robust interparticle bonding and interactions. While driven by electrostatics, the binding is stabilized by surface chemistry. AgNPs become spatially entangled yet not aggregated within the DND network, resulting in 8‐nm red shift of the plasmonic peak. This nanocomplex morphology is supported by transmission electron microscopy images and electromagnetic numerical simulations. Modeling shows that a 3‐nm gap between AgNP and DND particles consistently reproduces experimental data, confirming that DNDs modulate the plasmonic electromagnetic field. Moreover, the plasmonic peaks undergo pronounced intensity changes depending on AgNP concentration: low concentrations enhance (up to +78%), whereas high concentrations lead to suppression (down to −49%) of AgNP plasmonic absorption, independent of DND content. The model shows that, this arises from AgNP field redistribution and interference. The AgNP‐DND entangled nanocomplexes thus offer a simple route to a stable hybrid nanoparticle system with tunable optical properties for diverse applications, from biosensing to catalysis, energy conversion or quantum technologies.