nl9b03258_si_001.pdf (1.33 MB)
Optical Processing of DNA-Programmed Nanoparticle Superlattices
journal contribution
posted on 2019-10-16, 14:40 authored by Leonardo
Z. Zornberg, Paul A. Gabrys, Robert J. MacfarlaneHierarchical
structural control across multiple size regimes requires
careful consideration of the complex energy- and time-scales which
govern the system’s morphology at each of these different size
ranges. At the nanoscale, synthetic chemistry techniques have been
developed to create nanoparticles of well-controlled size and composition.
At the macroscale, it is feasible to directly impose material structure
via physical manipulation. However, in between these two size regimes
at the mesoscale, structural control is more challenging as the physical
forces that govern material assembly at larger and smaller scales
begin to interfere with one another. In this work, the interplay of
structure-directing forces at multiple length-scales is investigated
by utilizing optical processing to influence both nanoscale and microscale
features of self-assembled, DNA-grafted nanoparticle films. Optical
processing is used to generate heat, which causes the self-assembled
particles to rearrange from a kinetically trapped, amorphous state
into a thermodynamically preferred superlattice structure. The gradient
in the heat profile, however, also induces thermophoretic motion within
the nanoparticle film, resulting in microscale movement at a comparable
time-scale. By utilizing precise exposure times enabled by optical
processing, crystallization and thermophoresis occur concurrently
in the self-assembling nanoparticle system, enabling a dynamic growth
mechanism whereby nucleation and growth occur in separate regions
of the material. Furthermore, utilizing sufficiently short processing
times allows for the formation of a fluidlike state of the DNA-functionalized
nanoparticle materials that is inaccessible via typical thermal processing
setups. This unique phase of the material allows for both pathway-dependent
and pathway-independent growth phenomena, as appropriately tuning
the experimental conditions enables the formation of morphologically
equivalent nanoparticle lattices that are generated through different
intermediate states (pathway-independent structures), or kinetically
preprocessing a material to yield unique thermodynamic arrangements
of particles once fully annealed (pathway-dependent structures).