Reports: UNI1050461-UNI10: Plasmonics of Metals and Conducting Polymers in the Nano-Scale for High Efficiency Photovoltaics

Yohannes Abate, phD , California State University

Narrative Report MAIN RESEARCH ACCOMPLISHMENTS AND THEIR SIGNIFICANCE Summary We have been focused on imaging plasmonics on metal nanoparticles and nanostructures in real-space according to the proposed outline funded by ACS PRF. We focused on spherical Au nanoparticles and bowtie nano-antennas. In the visible spectrum we use mostly a HeNe laser at 633 nm. And in the mid infrared frequencies we employ 9-11 micron step tunable CO2 laser. We have been extremely successful on both of these frequency ranges. We have learnt a great deal on plasmonics and its interaction with capping layers. Plasmonicas on bowties. We have imaged the polarization states of symmetric and antisymmetric bowties. We have done theoretical simulations using the Finite Domain Model and the dipole model to understand the enhancement and modification of near-field plasmonics on these nanostructures. Most of the work was done by graduate student Bryan Heiberg who has already written his thesis on plasmonics of metallic nanostructures as reflected on the title of his thesis, ““LOCALIZED SURFACE PLASMON RESONANCE IN GOLD NANOSPHERES AND PLASMONIC NANOANTENNAS””. Bryan will be graduating this summer with MS in physics and greatly acknowledges ACS PRF. Plasmonics on bare Au Nanoparticles and silica coated Nanoparticles in the visible and Mid IR frequencies. As we proposed to do, we have had great success in imaging plasmonic Au nanoparticles and their interactions with a coating layer both in the visible and infrared frequencies. We employed high resolution near-field microcopy and investigated the near-field optical contrast mechanism in coated nanoparticles by imaging three types of individual particles (silica, Au and silica-capped AuNPs) and mixed particles adsorbed on Si substrate. An increased optical contrast between silica and silica-capped AuNPs is observed at 633 nm than at 10.7 ?m. The difference is mainly from the on-and off- plasmon resonances in visible and mid-infrared frequencies: AuNPs and silica-capped AuNPs have dipolar plasmon resonance near 633 nm whereas they are off-resonant in 10.7 um. The plasmon-enhanced near-field coupling between the tip’s near-field and the Au core through the silica cover layer enhances the weak near-field interaction of the silica capping layer. These results were acquired by graduate student Zach Nuno and three undergraduate students, Brandon Hessler, Codi Bonney and Jerry Ochoa. The work they did on plasmonic coated and uncoated Au nanoparticles is the main part of Zach’s MS thesis and has been accepted for publication in Optic Express. Publications 1. Results are accepted in Optics Express for publications. Zachary Nuño, Brandon Hessler, Jerry Ochoa, Young-Seok Shon, Codi Bonney, and Yohannes Abate "Nanoscale subsurface- and material-specific identification of single nanoparticles" Opt. Express (accepted) 2. Results accepted for publication in proceedings of TechConnect World 2011 Conferences and Expo: Nanotech2011 3. Our work on ““Nanoscale near-field infrared spectroscopic imaging of silica-shell/gold-core and pure silica nanoparticles”,is submitted to Journal of Nanoparticle Research 4. The PI has published a collaborative paper Johannes M. Stiegler, Yohannes Abate, Antonija Cvitkovic, Yaroslav Romanyuk, Andreas J. Huber, Stephen R. Leone, and Rainer Hillenbrand "Nanoscale Infrared Absorption Spectroscopy of Individual Nanoparticles Enabled by Scattering-Type Near-Field Microscopy" (Equal Contribution) ACS Nano 5, 6494(2011) STUDENT PARTICIPATION Zach Nuno: Zach joined our group in the Spring of 2009 and has been a key member of the group since then. He is just acceprted to a PhD program at UC Merced. Zach, together with undergraduate studrents in the group, did most of the work on the visible and IR plasmonics studies on coated and uncoated nanostructures which resulted in two manuscripts. Bryan Heiberg. Bryan also joined our group in the Spring of 2009 have been a member of my research group for the last two academic years. In his second semester in my group, he setup an infrared and visible laser based near-field microscopy on a floating optical table, performed the first set of experiments on bowtie plasmonic nanostructures. He has already written his thesis and have now graduated with MS degree. He is now working as a college teacher. Brando Hessler. Brandon is one of the most active undergraduate student in the group. He has done most of the preparation of the samples for both the visible and mid IR frequency experiments. Brandon Hessler presented our research results at The California-Nevada Section of the American Physical Society (CA-APS) held at Caltech, Oct 2010. Jerry Ocua. Jerry has been one of the important students in the group since the start of the lab. The installation of the near-field microscopy required extensive preparation long before we received it. He has helped design our lab’s lay out on a computer screen using 3D design programs (CAD, Google 3D sketch). Codi Bonney. Codi is a very talented programmer. He has done theoretical calculations to support and improve our experiments. He write a fantastic program that can simulate the experiments we conduct using MATLAB. The program he wrote will remain a very important part of our research lab that could be used for many other experiments to come. Ralph Demato. Ralph joined the group recently and is already making significant progress in their research. Ralph is continuing the work on plasmonics on bowties near-field studies. Terry Dunlap. Terry is an undergraduate student who has just joined our group and is learning to operate the microscope. He would like to apply to graduate school to get his PhD once he has completed his degree at CSULB. Student awards related to this research award: * Zachary Nuño selected for the competitive 11th Annual Berkeley Edge Conference at UC Berkeley * Zachary S. Nuño submitted abstract for the Nanotech 2011 Conference and Expo, June 2011 (accepted abstracts will be published as proceedings) * Zachary S. Nuño accepted for the Phd program at UC Merced with full financial aid and tuition scholarship * Brandon won a two year PSMS Scholarship * Brandon Hessler presented our research results at The California-Nevada Section of the American Physical Society (CA-APS) held at Caltech, Oct 2010 * Group poster presented at the Gordon Conference for Plasmonics, June 2010, ME * Ralph Damato Simon George Physics Scholarship , 2011
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