The ability to synthesize materials by design is one of the greatest outstanding scientific challenges.
Advances towards meeting this challenge will lead to discoveries in fields such as plasmonics, photonics, catalysis, and energy sciences. In the Programmable Nanomaterials subgroup, we employ a novel approach to the realization of materials by design, where nanoparticle “atoms” functionalized with a dense shell of oligonucleotides are assembled via oligonucleotide-oligonucleotide “bonds” into crystalline superlattices with tunable compositions, symmetries, and lattice parameters.
The high degree of control over the assembly characteristics of these DNA-NP conjugates, termed programmable atom equivalents (PAEs), is enabled by the exceptional molecular recognition, tunability, and predictability of the DNA-DNA bonds. Unlike atomic systems in which the bonding character of an atom is dictated by its atomic composition and configuration of valence electrons, PAEs allow one to independently control the nanoparticle core (tunability in the nanoparticle size, shape, or composition) separately from the oligonucleotide bonds (controllable DNA sequence, length, flexibility, and strength). Ongoing research in the Programmable Nanomaterials subgroup focuses on exploiting the functionalities of the nanoparticle atoms in the crystalline state or tuning the nature of the DNA bonds.
Integrating nanoparticle functionalities into superlattices
Nanoparticles have interesting catalytic and optical properties that are distinct form their atomic or molecular precursors and are often dependent on their assembly state. We are exploiting the programmability of the DNA bond to tune the structures of PAE superlattices assembled in solution or layer-by-layer on substrates and investigating how superlattice architecture influences light-matter interactions. Nanoparticle superlattices composed of Au-core PAEs showed strong light-plasmon interactions that were tunable by independently controlling lattice constants and nanoparticle diameters. By employing a layer-by-layer assembly approach, the thickness of the crystal and can be modulated to control the relative contributions of plasmonic and photonic properties to the overall light-matter interactions of the crystal. We are currently combining these experimental studied with a theoretical framework that will allow us to predict how crystal lattice structure, habit, and composition control light-matter interactions, and ultimately, to develop highly tunable plasmonic metamaterials.
We are also employing proteins, which are Nature’s form of molecularly pure nanoparticles, as functionally and structurally unique PAE cores. This work takes advantage of the diverse structures, orthogonal surface chemistries, and the ability to site-specifically modify the surface of proteins to assemble single- and multicomponent superlattices with symmetries that are difficult to obtain using spherical PAEs. These superlattices integrate the catalytic functionalities of the protein building blocks, and ultimately will be used to enable cascade reactions or to assemble hybrid materials composed of proteins and inorganic nanoparticles with complementary functionalities.
Employing the programmability of the DNA bond to create tunable and responsive nanoparticle superlattices
Biological systems are inherently responsive to external stimuli, enabling a high degree of control over complex processes such as signaling cascades. We are developing several unique approaches for designing oligonucleotide bonds that enable a similar degree of responsiveness and tunability to be incorporated into PAE superlattices. One example of this is the concept of “transmutable nanoparticles”, which include a number of closed ‘hairpin’ DNA strands along the surface of nanoparticles that cannot link with strands on neighboring particles. The addition of “effector” strands, which are short oligonucleotide sequences that act as switches and can open these hairpins, allows the particles to bond into a particular lattice arrangement. By using different switches and combinations of nanoparticles, we can effectively and dynamically change the bonding character of “transmutable nanoparticles” and drive their crystallization pathway along multiple thermodynamic trajectories.
We are also tuning the stability and responsiveness of PAE superlattices by replacing DNA-DNA bonds with RNA-RNA or RNA-DNA bonds. These different types of oligonucleotide bonds result in superlattices with unique properties, such as thermal stability or susceptibility to enzymatic degradation. We are currently combining these different types of oligonucleotide bonds with oligonucleotide modifying enzymes to create superlattices that can be selectively modified.
Programmable Materials Subgroup Members
Standing (L-R): Kurinji Krishnamoorthy, Zack Urbach, Hang Xing, Youngeun Kim, Kacper Skakuj (leader), Ashlee Robison, Stacey Barnaby, Jarad Mason, Andy Wang, Alex Scott, Jessie Ku, Jeff Brodin (leader), Mike Ross, Taegon Oh, Lianne Moreau
Sitting: Janet McMillan, Eileen Seo, Lam-Kiu Fong, Mary Wang