1. NIRT/GOALI: SELF ASSEMBLY AT ELECTRONIC AND PHOTONIC SCALES S.M. Lindsay (PI) Hao Yan (Co-PI) Rudy Diaz (Co-PI) Devens Gust (Co-PI) Shreya Battacharyya, Ashley Kibel, Raul Chhabbra, Jas Sharma Arizona State University, Tempe, AZ 85287 NIRT/GOALI: SELF ASSEMBLY AT ELECTRONIC AND PHOTONIC SCALES S.M. Lindsay (PI) Hao Yan (Co-PI) Rudy Diaz (Co-PI) Devens Gust (Co-PI) Shreya Battacharyya, Ashley Kibel, Raul Chhabbra, Jas Sharma Arizona State University, Tempe, AZ 85287 Abstract The optical absorption cross section of molecules is so small that a layer many thousands thick is required to absorb incident sunlight, a severe obstacle to charge extraction over such distances. We propose to construct a ‘black monolayer’ using DNA nanotechnology as a scaffold on which to build photonic antennas that will enhance optical absorption. Abstract The optical absorption cross section of molecules is so small that a layer many thousands thick is required to absorb incident sunlight, a severe obstacle to charge extraction over such distances. We propose to construct a ‘black monolayer’ using DNA nanotechnology as a scaffold on which to build photonic antennas that will enhance optical absorption. Indium Tin Oxide STM Tip MOLECULAR DYAD I. Characterization of electron transport through charge separation unit (a) (d) (b) Figure (a): Schematic of attachment of charge separation unit between the surface of the transparent conducting oxide (Indium Tin Oxide) and the Gold STM tip. (b) The charge separation unit, a “Molecular Dyad” with a donor/ chromophore (porphyrin) and nearby acceptor (fullerene). (c) Current histogram obtained from STM break-junction measurements showing conductance of a single molecular dyad trapped between surface and tip to be 2.3 nS. (d) Raw data for current vs. time. “Constant current” steps occurs when a single molecule trapped between surface and STM tip. Tip bias: +0.4 V Solvent : mesitylene Conductance= 2.37 nS = 3.06 X 10 -6 G O Computational evidence of a true photonic antenna mode arising from the structural resonance of a two-nanosphere plasmon antenna. Molecules placed in the vicinity of such an antenna have greatly enhanced Radiative Transfer Rate and Absorption Cross Section. d Antenna Mode Surface Plasmon Resonances Ag III. Theoretical calculations Conducting atomic force microscopy images of Fluorine Tin Oxide (FTO) and Indium Tin Oxide (ITO). Topography images are on the left sides and current images are on the right sides. Transparent, conducting substrates, like FTO and ITO, are necessary for the design of the solar cell in that they will allow light to pass through to the monolayer. Conducting AFM gives insight into the morphological and electrical properties of these materials. II. Conducting atomic force microscopic images of (a) FTO and (b) ITO Acknowledgement Supported by the National Science Foundation 0609362 Acknowledgement Supported by the National Science Foundation 0609362 IV. DNA directed self-assembly of metallic nanoparticles (a) (b)(c) Figures showing the use of information guided DNA self-assembly to organize the particles in proximal distances thus rendering them capable of acting as antenna molecules. (a) A cartoon showing the organization of discrete number of Gold nanoparticles (10 nm) on a fixed size DNA template. The DNA template is generated by the nucleated self-assembly process that utilizes a single stranded viral genome as a nucleation site for self-assembly. A set of ‘helper strands’, complementary to viral genome, help folding the viral DNA into arbitrary shapes, for example, a DNA tube in this context. DNA tube is fully programmable due to the fact that each ‘helper strand’ is addressed with a unique sequence. (b) TEM images of the DNA tube patterning discrete number of gold nanoparticles. (c) TEM images of the nearly monodisperse (~25-27 nm) silver nanoparticles, to be used in the future experiments. Silver nanoparticles interact with light more than gold nanoparticles; thus will be an attractive candidate for investigation of photonic properties. (a) (c) (b)