Self-assembly is the process by which individual components organize into hierarchical and functional structures, and is a primary focus of nanoscience and nanotechnology. Microfluidics has emerged as a powerful technology in various fields such as chemical synthesis, medical diagnostics and high throughput biological assays. Reaction parameters, such as the residence time, temperature and pressure, can be easily tuned within the confined environment of microfluidic devices. We employ here microfluidics to influence the assembly kinetics of multivalent host- and guest-equipped building blocks to thereby control the size of the resulting supramolecular structures.The present study describes the controlled self-assembly of size-tunable supramolecular silica nanoparticle clusters (SNPCs) based on the molecular recognition of methyl viologen silica nanoparticles (MV-SiO2), mono- and multivalent building blocks equipped with naphthol (Np), and cucurbit[8]uril (CB[8]) in a microfluidic device. The SNPC formation is based on the selective host-guest interaction of Np, MV and CB[8] which are known to form hetero-ternary complexes in aqueous solution. In contrast to experiments carried out in bulk, DLS and SEM confirm the formation of distinct SNPCs after mixing the MV-SiO2with a premixed solution of Np-containing components and CB[8] in a microreactor. Size tunability of the SNCPs was observed by tuning the ratio of the multivalent vs. monovalent Np derivatives, while keeping the overall concentrations of the molecular recognition moieties equimolar. Importantly, this study shows that the microfluidic flow conditions have a strong influence on the resulting SNPC size. A decrease in flowrate, leading to a concomitant increase in mixing time, of the two inlet streams, while keeping the concentrations and ratios of the building blocks constant, induced an increase of the SNCP size. This illustrates that the SNPC formation is, at least in part, kinetically controlled.

Self-assembly of size-tunable supramolecular nanoparticle clusters in a microfluidic channel

248th National Meeting (2014)

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