Stepwise Evolution of DNA‐Programmable Nanoparticle Superlattices

Abstract

Colloidal crystals can be assembled using a variety of entropic, [1][2][3] depletion, [4,5] electrostatic, [6][7][8] or biorecognition forces [9][10][11][12] and provide a convenient model system for studying crystal growth. Although superlattices with diverse geometries can be assembled in solution and on surfaces, the incorporation of specific bonding interactions between particle building blocks and a substrate would significantly enhance control over the growth process. Herein, we use a stepwise growth process to systematically study and control the evolution of a body-centered cubic (bcc) crystalline thinfilm comprised of nanoparticle building blocks functionalized with DNA on a complementary DNA substrate. We examine crystal growth as a function of temperature, number of layers, and substrate-particle bonding interactions. Importantly, the judicious choice of DNA interconnects allows one to tune the interfacial energy between various crystal planes and the substrate, and thereby control crystal orientation and size in a stepwise fashion using chemically programmable attractive forces. This is a unique approach since prior studies involving superlattice assembly typically rely on repulsive interactions between particles to dictate structure, and those that rely on attractive forces (e.g. ionic systems) still maintain repulsive particle-substrate interactions.In addition to providing a model for crystallization, the field of particle assembly has garnered considerable interest because materials generated from ordered particle arrays can have novel optical, [1,3,[13][14][15][16][17] electronic, [13,18] and magnetic properties. [19,20] These properties can be sensitive to the composition, symmetry, and distance between nanoparticles, in addition to the number of layers and orientation. [9,15,16] DNA-mediated nanoparticle crystallization is particularly attractive for preparing these materials because the nanoparticle building blocks can be considered a type of "pro-

Defect tolerance and the effect of structural inhomogeneity in plasmonic DNA-nanoparticle superlattices

“…Here, 10-, 20-, and 40-nm diameter Au nanoparticles are used to form bcc-type superlattices using an A-type, B-type layer-by-layer assembly method described previously (Fig. 1A, Supporting Information, and Table S1) (22). Using grazing incidence smallangle X-ray scattering (GISAXS), the interparticle spacing and crystal quality can be determined quantitatively; Table 1 lists the nanoparticle size, lattice parameter, nearest-neighbor distance (surface-to-surface), volume fraction, and film thickness of the superlattices probed in this work (Fig.…”

“…These factors include the chemical environment of the structure, the inhomogeneity of the nanoparticle building blocks, and the displacement of nanoparticles within the lattice. We use the programmability of DNA (3,(17)(18)(19)(20)(21)(22) to construct body-centered cubic (bcc) thin-film plasmonic superlattices comprising nanospheres with diameters of 10, 20, and 40 nm. We compare the optical response of these superlattices with two types of simulations: (i) Fresnel thin-film simulations based solely on volume fraction that closely mimic the experimental geometry, and (ii) rigorous electrodynamics simulations that explicitly describe structural inhomogeneities of the crystalline superlattice.…”

Importance of the DNA “bond” in programmable nanoparticle crystallization

“…These results should aid in the design of future crystals, as understanding the pathway by which a disordered aggregate becomes crystalline (as well as knowing which design parameters and conditions facilitate this process) enables better control of the annealing procedure, allowing for the establishment of design processes that encourage reliable, high-quality crystal syntheses. Moreover, the ability to stabilize a crystal under different environmental conditions (e.g., variations in solution ionic strength or temperature) improves their ability to be used in different contexts, such as epitaxial growth of crystals on surfaces (24), thermally addressable topotactic intercalation of multiple nanoparticle components (25), or assembly of Wulff polyhedra via slow cooling at high temperatures (15). We also established that studies of systems where DNA bonds are formed via transient interactions between small sticky ends at the tip of primarily rigid DNA duplexes not only enable more complex superlattice design, but also facilitate fundamental investigations of their crystallization behavior.…”

Epitaxy: Programmable Atom Equivalents Versus Atoms

“…angles (rotation around the z-axis). In-depth information about GISAXS analysis is available from Senesi et al 12 and Li et al 25 GISAXS scattering patterns of 5-layer ( Figure S4a) and 10-layer ( Figure S4b) films were indexed to bcc crystals with (100) orientation corresponding to space group I4/mmm (#139).…”

“…In the context of PAE thin films, assembly on unpatterned surfaces has been demonstrated to produce rough, polycrystalline films with a lack of long-range order or alignment. 12 Assembly of PAEs on patterned substrates has also been attempted but was limited to monolayers of single crystalline thin films, as the combination of both NP−substrate and NP−NP binding events significantly increases the complexity of multilayer epitaxial crystal formation. 4,13,14 In order to fully control thin film morphology in PAE superlattices, these complexities must be better understood via investigations into the thermodynamics of lattice growth as a function of different variables.…”