Nano-dynamic imaging: NanoSpacer as a low-cost optical method for real-time visualisation of nanoparticle disassembly and functionalisation

Understanding the dynamic behavior of nanomaterials in solution remains challenging due to reliance on specialized instrumentation, costly infrastructure, and highly trained personnel. Here we introduce the NanoSpacer, a low-cost, label-free fluidic confinement platform that enables real-time monitoring of supramolecular assemblies, termed nano-dynamic imaging , using simple darkfield microscopy. We apply this approach to investigate the assembly, disassembly and surface chemistry of indocyanine green (ICG) J-aggregate systems. Using the NanoSpacer, we characterize conventional ICG J-aggregates and show that solvent- and surfactant-induced disassembly correlates with a decrease in chemical potential. We further report the first synthesis of hybrid ICG/ ICG-azide J-aggregate nanorods and reveal pronounced structural changes within supramolecular assembly. Real-time NanoSpacer imaging directly captures the in-situ disassembly of these hybrid nanorods, exposing dynamic pathways that are obscured in ensemble-averaged measurements. Moreover, surface click reactions on individual nanorods can be monitored in real time, uncovering substantial heterogeneity in single-particle reactivity. Collectively, these results establish the NanoSpacer as a versatile platform for probing nanoscale dynamics and surface functionalization. By lowering technical and financial barriers, this approach broadens access to dynamic studies of nanoscale systems, bringing us closer to the rational design of nanostructures.