Using DNA to Design Plasmonic Metamaterials with Tunable Optical Properties

Abstract

Due to their potential for creating 'designer materials,' the 3D assembly of nanoparticle building blocks into macroscopic structures with well-defi ned order and symmetry remains one of the most important challenges in materials science. [1][2][3][4][5] Furthermore, superlattices consisting of noble-metal nanoparticles have emerged as a new platform for the bottom-up design of plasmonic metamaterials. [6][7][8] The allure of optical metamaterials is that they provide a means for altering the temporal and spatial propagation of electromagnetic fi elds, resulting in materials that exhibit many properties that do not exist in nature. [9][10][11][12][13] With the vast array of nanostructures now synthetically realizable, computational methods play a crucial role in identifying the assemblies that exhibit the most exciting properties. [ 14 ] Once target assemblies are identifi ed, the synthesis of nanometer-scale structures for use at optical and IR wavelengths must be taken into account. Many of the current methods to fabricate metamaterials in the optical range use serial lithographic-based approaches. [ 6 ] The challenge of controlled assembly into well-defi ned architectures has kept bottom-up methods that rely on the self-organization of colloidal metal nanoparticles from being fully explored for metamaterial applications. [ 8 ] DNA-mediated assembly of nanoparticles has the potential to help overcome this challenge. The predictability and programmability of DNA makes it a powerful tool for the rational assembly of plasmonic nanoparticles with tunable nearest-neighbor distances and symmetries. [ 1,[15][16][17][18] Herein, we combine theory and experiment to study a new class of plasmonic superlattices-fi rst using electrodynamics simulations to identify that superlattices of spherical silver nanoparticles (Ag NPs) have the potential to exhibit emergent metamaterial properties, including epsilon-near-zero (ENZ) behavior, [ 13 ] and a region with an 'optically metallic' response.Optically metallic materials are DC insulators that refl ect in the visible spectrum. This behavior can be described as the opposite of the common touch-screen material, indium tin oxide (ITO), which is transparent in the visible spectrum, but conducts electricity. We then synthesize the fi rst examples of silver nanoparticle superlattices using DNA-mediated assembly and characterize their optical properties with both ensemble measurements and measurements of individual superlattices using spectroscopy. Furthermore, we expand beyond monometallic nanoparticle superlattices to create novel binary superlattices of gold and silver nanoparticle building blocks and observe a Fano-like interference between the two components, leading to a signifi cant dampening of the plasmonic response.ENZ materials [ 19 ] are a new class of metamaterials that allow for the tunneling of light through a barrier and present the opportunity for arbitrary phase manipulation of light. [ 13,[20][21][22] With the global progression of optical fi bers and the potential ...

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

“…The use of imperfect building blocks in bottom-up nanoparticle assemblies often results in defects, grain boundaries, and lattice strain (30)(31)(32)(33)(34)(35). In the systems studied in this work, molecular dynamics simulations suggest that DNA-assembled particles can exhibit 5-10% variation in their position due to the dynamic reorganization that occurs as interparticle linkages break and reform (36).…”

“…This suggests that the interparticle plasmonic interactions here are primarily coherent and in-phase; small displacements (relative to their radii) in nanoparticle position do not meaningfully change the weak plasmonic coupling between particles. In turn, many of the emergent plasmonic and photonic effects that we have identified in similar systems (29,34,39) are likely robust to the presence of defects and forgiving to minor variations to the crystalline environment.…”

“…We have previously implemented volume-fraction-based methods with predictable and consistent agreement between experiment and simulation in the far field (28,29,32,34,39). Many of the unique and exciting plasmonic materials that we have explored using programmable DNA assembly depend solely on dipolar interparticle interactions (at low volume fraction) and are fairly insensitive and defect-tolerant.…”

Optical properties of anisotropic 3D nanoparticles arrays

“…DNA self-assembled superlattices have become a way to design novel metamaterials with a very specific response to electromagnetic fields [6,9,10]. In this paper, we focus on the use of DNA, which has the advantage that the resulting structures are robust to small variations or perturbations [15] and the inter-particle separation can be finely tuned [16].…”

“…By changing the number of DNA-base pairs, superlattice engineering of different crystalline structures [4] is possible as well as directional crystallization [5,6]. The many applications derived from DNA superlattice engineering include the assembly of superstructures for biological delivery [7], biosensors [8], tuning of the plasmonic response of superlattices [9,10], ordering of Au nanoparticles in one-dimensional arrays [11,12], among others.…”