9:45 - 10:10InvitedID: 242
CONTROLLING ENERGY TRANSPORT WITH DNA-CHROMOPHORE ASSEMBLIES
Massachusetts Institute of Technology (MIT), Cambridge, Massachusetts, United States of America
Control over nanoscale spatiotemporal dynamics has the potential to enable materials with light harvesting, computing, and sensing capabilities. Here, we describe the creation and optimization of DNA-chromophore assembles to produce excitonic circuits, which are devices that prescribe specific spatiotemporal dynamics of an excited state. We leverage the power of DNA self-assembly to introduce nanometer-scale geometric control over structure and site-specifically embed chromophores with control over distance and orientation. We design two unique classes of DNA-templated chromophore aggregates, one enabling superradiant excitations and the other enabling subradiant excitations. In the first class of aggregates, we demonstrate controlled formation of superradiant (J-) aggregates on DNA nanostructure scaffolds. By controlling the length and sequence of DNA duplexes, we examined the progression of delocalization of excitations, and experimentally demonstrated that delocalization can enhance the efficiency of energy transfer. In the second class, we engineer dimers in subradiant (H-) aggregate geometry. We exploit site-specific control provided by DNA to understand the dependence of energy transport on intermolecular interactions. These two distinct classes of aggregates offer the eventual use of DNA as a scaffold to engineer excitonic circuitry for solar energy and computing applications.
10:10 - 10:25ID: 257
STRUCTURAL AND PHOTOPHYSICAL TEMPLATING OF A CONJUGATED POLYELECTROLYTE WITH SINGLE-STRANDED DNA
1Department of Chemistry, University of Cyprus, Nicosia, Cyprus; 2Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland; 3Laboratory of Computational Chemistry and Biochemistry, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
A highly promising approach to influence and control the photophysical properties of conjugated polymers is directing their molecular conformation by templating. We report here the templating effect of single-stranded DNA oligomers (ssDNAs) on a cationic polythiophene (CPT). By means of electrostatic and other non-covalent interactions, the ssDNAs assemble with CPT, directing its backbone to different conformations depending on the sequence of nucleic bases. We have comprehensively characterized the optical behaviour of CPT in three conformationally distinct CPT/ssDNA complexes through steady state absorption, cyclic dichroism (CD), and resonance Raman (RR) spectroscopy and addressed the ultrafast excited-state species and dynamics. This, in combination with molecular dynamics simulations, allowed us an unprecedented atomistic-level understanding of the structure-property correlations. We find that an extensive sequence of cytosine bases is necessary for the strongest templating effect, due to numerous π-stacking interactions between thiophene and cytosine rings, which can force CPT into a rigid assembly with highly ordered chains and unique optical signatures. Our insights are an important step forward in a pioneering approach to structural templating and optoelectronic control of conjugated polymers and organic materials in general.
10:25 - 10:40ID: 140
HYBRID PLASMONIC/PHOTONIC CRYSTALS FOR OPTICAL DETECTION OF BACTERIAL CONTAMINANTS
1Center for Nanoscience and Technology, Istituto Italiano di Tecnologia, Milan, Italy; 2Dipartimento di Fisica, Politecnico di Milano, Milan, Italy; 3Dipartimento di Chimica, Materiali e Ingegneria Chimica "Giulio Natta", Politecnico di Milano, Milan, Italy; 4Department of Nanochemistry, Istituto Italiano di Tecnologia, Genova, Italy
Photonic crystals (PhCs) have been largely employed as detection/sensing devices in recent years, since the photonic stop-band can be tuned by applying a number of external stimuli, such as chemical1, thermal2 and mechanical triggers3. In this context, we have recently proposed porous 1D photonic structures exhibiting electro-optical tunability, due to the incorporation of optoelectronically-active plasmonic nanoparticles in the photonic structures.4–6
Here, we show that a hybrid plasmonic/photonic crystal consisting of a thin layer of bioactive plasmonic material (i.e. silver) deposited on top a 1D PhC can detect one of the most common bacterial contaminant, namely Escherichia coli. We speculate that the change in the plasmon charge density brought about by metal/bacterium interaction results in a variation of the plasmon resonance which, in turns, translates in a shift of the photonic structural color.
1 W. Hong, X. Hu, B. Zhao, F. Zhang, and D. Zhang, Adv. Mater. 22, 5043 (2010).
2 T. Kanai, D. Lee, H.C. Shum, R.K. Shah, and D.A. Weitz, Adv. Mater. 22, 4998 (2010).
3 H. Fudouzi and T. Sawada, Langmuir 22, 1365 (2006).
4 E. Aluicio-Sarduy, S. Callegari, D.G.F. del Valle, A. Desii, I. Kriegel, and F. Scotognella, Beilstein J. Nanotechnol. 7, 1404 (2016).
5 G.M. Paternò, C. Iseppon, A. D’Altri, C. Fasanotti, G. Merati, M. Randi, A. Desii, E.A.A. Pogna, D. Viola, G. Cerullo, F. Scotognella, and I. Kriegel, Sci. Rep. 8, 3517 (2018).
6 G.M. Paternò, L. Moscardi, I. Kriegel, F. Scotognella, and G. Lanzani, J. Photonics Energy 8, 1 (2018).