| Summary: | Nanocomposite tectons (NCTs) offer a versatile method for systematically modulating material properties at the nanoscale. These building blocks are created by grafting nanoparticles with end-terminated polymers comprising supramolecular binding groups, akin to DNA base pair hydrogen bonding. This approach enables the precise organization and assembly of NCT units into macroscopic materials. By adjusting nanoparticle core sizes, polymer brush lengths, and molecular recognition groups, NCTs can be tailored to produce superlattices with controlled crystalline structures, lattice spacing, and geometries. These superlattices have potential applications in photonics, plasmonics, and microfluidicfluidics. While NCTs can be produced in bulk scale, processing these materials into useful devices remains challenging. One major hurdle is the random aggregation of crystals during assembly, which makes it difficult to identify the properties of single NCT crystals. This study investigates methods to process NCTs and their assemblies into monodisperse crystallites and oriented crystal films, using density gradient centrifugation and scratch-directed assembly, respectively.
Density gradient centrifugation allows for the separation of NCT assemblies, comprising various-sized crystallites, into discrete monodisperse distributions. This technique was applied to NCTs composed of gold nanoparticles (AuNPs) and iron oxide nanoparticles (IONPs), grafted with a polystyrene (PS) brush end-terminated with either diaminopyridine (DAP) or thymine (Thy) – which serve as a complementary hydrogen bonding pair. Scanning electron microscopy (SEM) analysis of drop-casted assemblies demonstrated the effectiveness of density gradient separation in processing NCT crystallites into size-specific distributions while revealing a crucial relationship between crystallite size and shape.
Heterogenous nucleation provides a means for directing assembly in more controlled ways, for example via nano scratch-directed assembly. SEM analysis of scratched substrates revealed that NCTs in contact with scratches exhibit strong alignment and have the potential to form larger single-crystalline superlattices through oriented attachment.
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