10:30 AM - *SF04.01.01
Designing Optical Metamaterials from Colloidal Noble Metal Nanocrystal Assemblies
University of Pennsylvania1
Colloidal noble metal nanocrystals (NCs) have metal cores and organic or inorganic ligand shells and are known for their size- and shape-dependent localized surface plasmon resonances. In this talk, I will describe the use of these NCs as building blocks of assemblies with designer optical properties for 2D and 3D metamaterials. Chemical exchange of the long ligands used in NC synthesis with more compact ligand chemistries reduces the interparticle distance (d) and increases interparticle coupling. This ligand-controlled coupling allows us to tune through a dielectric-to-metal phase transition, seen by a 1010 range in DC conductivity and a dielectric permittivity ranging from everywhere positive to everywhere negative across the whole range of optical frequencies , and design assemblies that are strong optical absorbers  or scatterers [1,3]. We harness the solution-processability and physical properties of colloidal NCs to pattern NC superstructures for large-area metamaterials, demonstrating 2D extreme bandwidth quarter-wave plates  and optical sensors . By exploiting the different chemical and physical properties of NC assemblies from bulk thin films, we construct NC/bulk bilayer heterostructures that, upon ligand exchange, fold into three-dimensional structures  providing a simple route to 3D metamaterials, demonstrating chiral structures that form broadband circular polarizers [6,7]. Combining superparamagnetic NCs and plasmonic NCs, we fabricate multifunctional, smart superparticles, that in suspensions, switch their polarization-dependent transmission in the infrared in response to an external magnetic field .
1. A. T. Fafarman, S.-H. Hong, H. Caglayan, X. Ye, B T. Diroll, T. Paik, N. Engheta, C. B. Murray, C. R. Kagan, “Chemically Tailored Dielectric-to-Metal Transition in the Design of Metamaterials from Nanoimprinted Colloidal Nanocrystals,” Nano Lett 13, 350-357 (2012).
2. W. Chen, J. Guo, Q. Zhao, P. Gopalan, A. T. Fafarman, Au. Keller, M. Zhang, Y. Wu, C. B. Murray, C. R. Kagan, “Designing Strong Optical Absorbers via Continuous Tuning of Interparticle Interaction in Colloidal Gold Nanocrystal Assemblies,” ACS Nano, 13, 7493-7501 (2019).
3. W. Chen, M. Tymchenko, P. Gopalan, X. Ye, Y. Wu, M. Zhang, C. B. Murray, A. Alu, C. R. Kagan, “Large-Area Nanoimprinted Colloidal Ay Nanocrystal-Based Nano-antennas for Ultrathin Polarizing Plasmonic Metasurfaces,” Nano Lett 15, 5254-5260 (2015).
4. W. Chen, G. Wu, M. Zhang, N. J. Greybush, J. P. Howard-Jennings, N. Song, F. S. Stinner S. Yang, C. R. Kagan, “Angle-Independent Optical Moisture Sensors Based on Hydrogel-Coated Plasmonic Lattice Arrays,” ACS Appl Nano Mater 1, 1430-1437 (2018).
5. M. Zhang, J. Guo, Y. Yu, Y. Wu, H. Yun, D. Jishkariani, W. Chen, N. J. Greybush, C. Kubel, A. Stein, C. B. Murray, C. R. Kagan, “3D Nanofabrication via Chemo-Mechanical Transformation of Nanocrystal/Bulk Heterostructures,” Adv. Mater. 30, 1800233 (2018).
6. J. Guo, J.-Y. Kim, M. Zhang, H. Wang, A. Stein, C. B. Murray, N. A. Kotov, C. R. Kagan, “Chemo- and Thermomechanically Configurable 3D Optical Metamaterials Constructed from Colloidal Nanocrystal Assemblies,” ACS Nano 13, 1427-1435 (2019).
7. J. Guo, J.-Y. Kim, S. Yang, J. Xu, Y. C. Choi, A. Stein, C. B. Murray, N. A. Kotov, C. R. Kagan, “Broadband Circular Polarizers via Coupling in 3D plasmonic Meta-Atom Arrays,” ACS Photonics, 8, 1286-1292 (2021).
8. M. Zhang, D. J. Magagnosc, I. Liberal, Y. Yu, H. Yun, H. Yang, Y. Wu, J. Guo, W. Chen, Y. J. Shin, A. Stein, J. M. Kikkawa, N. Engheta, D. S. Gianola, C. B. Murray, C. R. Kagan, Nature Nano, 12, 228-232 (2016).