Plasmonic-coupling-based sensing by the assembly and disassembly of dipycolylamine-tagged gold nanoparticles induced by complexing with cations and anions

A surface-plasmon-coupling-mediated sensor system is developed based on Au nanoparticles tagged with a coordinative dipycolylamine and lipoyl-anchored naphthalimide derivative (AuNP@DPA). The AuNPs with tailored ligands exhibit distinct sensing activity via sequential assembly into nanoparticle aggregates induced by metal ion complexing, and disassembly in the presence of pyrophosphate (PPi) anions, which is accompanied by a swift, reversible color change due to a surface plasmon resonance coupling effect. It is found that divalent metal ions are more effective than mono- or tri-valent ions in the aggregate formation process, Mn²⁺-induced aggregates are more sensitive to the capture of PPi anions than other AuNP aggregates, and the disassembly upon anion complexation exhibits a highly selective response. The AuNP@DPA-based molecular recognition system also demonstrates a viable performance for the detection of total selective metal ions present in different types of water analytes.