Bulletin of the American Physical Society
APS March Meeting 2013
Volume 58, Number 1
Monday–Friday, March 18–22, 2013; Baltimore, Maryland
Session J20: Focus Session: Metamaterials - Nanowires and Plasmonic Enhancement |
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Sponsoring Units: DMP Chair: Peter Nordlander, Rice University Room: 322 |
Tuesday, March 19, 2013 2:30PM - 2:42PM |
J20.00001: Excited state dynamics of single metal and semiconductor nanowires studied by transient absorption microscopy Shun S. Lo, Hong Y. Shi, Todd A. Major, Nattasamon Petchsang, Libai Huang, Masaru K. Kuno, Gregory V. Hartland Transient absorption microscopy (TAM) is a relatively new technique that allows the study of single nanostructures with sub-picosecond time resolution. Here, we present results for CdTe and Au Nanowires (NW). For the first material, we find an interesting power dependence of the excited dynamics, suggesting that a trap-filling mechanism is responsible for the observed behaviour. Additionally, acoustic phonons were observed, which were well described using continuum elastic models.\footnote{S. S. Lo et al. ACS Nano, \textbf{6}, 5274 (2012)} Carrier diffusion along these NWs are also reported. In the case of Au NWs, the propagation of surface plasmon polaritons was investigated. The results are in agreement with previous studies performed with fluorescence based techniques.\footnote{B. Wild et al. ACS Nano, \textbf{6}, 472 (2012)}$^,$\footnote{A. Paul et al. ACS Nano, \textbf{6}, 8105 (2012)} Unlike fluorescence techniques, multiple measurements on the same nanostructures are possible with TAM allowing one-to-one comparisons under different excitation polarizations and environments. [Preview Abstract] |
Tuesday, March 19, 2013 2:42PM - 2:54PM |
J20.00002: Damping of Acoustic Vibrations of Single Suspended Gold Nanowires and Nanoplates in Air and Water Environments Todd Major, Aur\'elien Crut, Bo Gao, Mary Devadas, Shun Lo, Natalia Del Fatti, Fabrice Vall\'ee, Gregory Hartland The dynamics of metal nanoparticles are affected by intrinsic properties, such as crystal structure, and the viscosity and acoustic impedance of the environment. In order to separate the contribution of the environment from the dynamics of individual nanostructures, ultrafast transient absorption measurements are taken on gold nanowires suspended over trenches on the substrate in air and in water. Measurements taken in an air environment represent damping from intrinsic sources, whereas experiments in water represent a liquid environment with a well known viscosity. Quality factors of the acoustic modes from the gold nanowires were measured and match well with previous studies. The results are compared to Continuum Mechanics Calculations. The calculations show that the viscosity of water plays a minor impact on the damping of the acoustic modes. This study has been recently extended to nanoplates suspended over trenches, but the effect of viscosity has not been investigated for these materials yet. [Preview Abstract] |
Tuesday, March 19, 2013 2:54PM - 3:06PM |
J20.00003: ABSTRACT WITHDRAWN |
Tuesday, March 19, 2013 3:06PM - 3:18PM |
J20.00004: Advanced scanning transmission electron microscopy characterization of UV LED nanowires Patrick Phillips, Rajan Kumar, Santino Carnevale, Roberto Myers, Robert Klie The role of aberration-corrected scanning transmission electron microscopy (STEM) in materials characterization is examined in regards to Al(x)Ga(1-x)N nanowires. Wires were graded from x$=$0 to x$=$1 and then from x$=$1 to x$=$0 with a small active quantum disk region located between the two gradations. This configuration is the basis for previously reported UV light emitting diodes. However, to assist subsequent growth processes while striving for optimum efficiency, both structural and chemical characterization methods are necessary, which can be provided at sufficiently high resolutions by advanced STEM instruments. Specifically, structural characterization will focus on determining layer thicknesses and wire polarity, as well as visualizing any short-range ordering and/or stacking faults that may be present. STEM multislice image simulations will also be discussed. Chemically, both energy dispersive X-ray (EDX) and electron energy loss (EEL) spectroscopies will be discussed in various capacities, ranging from quantum well composition (EDX) to N K-edge fine structure of both GaN and AlN (EELS). [Preview Abstract] |
Tuesday, March 19, 2013 3:18PM - 3:30PM |
J20.00005: Electrochemically Grown, Composite Au/CdS/Au Nanowires: Structural and Optical Properties Todd Brintlinger, Rhonda Stroud, James Long, Stefanie Sherrill, Sang Bok Lee, Blake Simpkins We present growth, characterization, and optical response of solution-synthesized nanoplasmonic structures coupled with nonlinear dielectrics. Transmission electron microscopy indicates the templated electrochemical growth of 60-300 nm diameter, 200-5000 nm long composite Au-CdS-Au cylindrical nanostructures yield wurtzite CdS spanning small gaps between Au nanowires. The electrodeposited CdS exhibits an absorption band at $\sim$ 500 nm consistent with band edge absorption of crystalline CdS and broad defect band luminescence centered $\sim$ 625 nm. CdS exhibits sufficient quality to produce second harmonic generation stimulated with a pulsed, linearly polarized pump-light from a femtosecond Ti-sapphire laser. The effect of structure geometry and environment on optical response is investigated through variations in substrates, growth parameters and focused-ion-beam (FIB) shaping of nanostructures. [Preview Abstract] |
Tuesday, March 19, 2013 3:30PM - 3:42PM |
J20.00006: Synthesis and Characterization of Gold-Titanium Dioxide Nanoparticles Hailey Cramer, Ismat Shah Nanoparticles are of recent scientific interest due to their unique size-dependent optical, electrical, and catalytic properties. Gold nanoparticles specifically, have many potential applications, especially in optoelectronic devices due to their optical properties and plasmon resonance. The specific goals of this research are to synthesize Au/TiO$_{2}$ core-shell nanoparticles for their use in improving the overall efficiency of P3HT/PCBM polymer solar cells previously prepared in our lab. The standard sodium citrate reduction method was used to synthesize gold nanoparticles with an average diameter of 15 nm. Through changing the concentration of sodium citrate in solution we were able to tune the size of the nanoparticles, and therefore change their light-absorbing properties. The goals of this research are to cap the gold nanoparticles with TiO$_{2}$ through a sol-gel method. Characterization of the Au/TiO$_{2}$ particles will be performed using high resolution tunneling electron microscopy to determine the size of the nanoparticles and the thickness of the TiO$_{2}$ shell. In addition, ultraviolet-visual spectroscopy was used to determine the absorption of the particles, and dynamic light scattering was used to confirm the size distribution of the particles. The incorporation of Au/TiO$_{2}$ nanoparticles in P3HT/PCBM devices will be discussed. [Preview Abstract] |
Tuesday, March 19, 2013 3:42PM - 3:54PM |
J20.00007: New experimental evidences of Au-Cu$_{2}$S core-shell nanoparticles and atomic resolution imaging by aberration-corrected STEM Subarna Khanal, Gilberto Casillas, Nabraj Bhattarai, J. Jesus Velazquez-Salazar, Miguel Jose Yacaman Au-Cu$_{2}$S core-shell nanoparticles present different properties than their monometallic counterparts, opening a wide range of possibilities for different applications. Au-Cu$_{2}$S core-shell nanostructures have raised interest for their many applications in photoelectronic, sensing, catalysis and so on. Au and Au-Cu$_{2}$S core-shell nanoparticles were prepared by using a modified polyol method. First Au seeds were prepared by reducing HAuCl$_{4}$.xH$_{2}$O in ethylene glycol (EG) in the presence of poly(vinylpyrrolidone) (PVP) as a polymer surfactant. Then Cu$_{2}$S shells were overgrown on Au core seeds by reducing CuSO$_{4}$ in EG with PVP. The morphology and structural characteristics of Au and Au-Cu$_{2}$S nanostructures were studied in detail using scanning electron microcopy HITACHI S-5500 and high resolution transmission electron microscope (HRTEM), a resolution 0.19 nm. Moreover, the Cs-corrected scanning transmission electron microscopy (Cs-corrected STEM) technique allowed us to probe the structure at the atomic level of these nanoparticles revealing new structural information. We determined the structure of the four main polyhedral morphologies obtained in the synthesis: decahedral, icosahedral, triangular plates, and rods. [Preview Abstract] |
Tuesday, March 19, 2013 3:54PM - 4:06PM |
J20.00008: Mechanism for resonant energy transfer in plasmonic light-harvesting materials Scott Cushing, Jiangtian Li, Nianqiang Wu, Alan Bristow Localized surface plasmon resonance (LSPR) is a promising route to extending the light-harvesting of semiconductors into the visible and near infrared. Core-shell nanostructures are studied using transient absorption spectroscopy to explore the carrier dynamics and energy harvesting mechanism [1]. The metal core@Cu$_{\mathrm{2}}$O shell nanoparticles have a broad plasmon resonance centered at 650 nm. The amplitude of the spectral dependence of the transient absorption can be fit using three contributions: the semiconductor density of states, the LSPR, or the overlap integral between the two. The fitting procedure reveals the energy transfer mechanism in Au@Cu$_{\mathrm{2}}$O is dominated by a plasmon induced resonant energy transfer, while the energy transfer in Ag@Cu$_{\mathrm{2}}$O is a combination of resonant energy transfer and hot electron injection from the metal to semiconductor. The effects of core composition and shell thickness are studied with the aim of finding the best combination for a viable full solar spectrum, plasmon-enhanced photocatalyst. [1] S. K. Cushing, J. T. Li, F. K. Meng, T. R. Senty, S. Suri, M. J. Zhu, M. Li, A. D. Bristow, N. Q. Wu, J. Am. Chem. Soc. 134, 15033 (2012). [Preview Abstract] |
Tuesday, March 19, 2013 4:06PM - 4:18PM |
J20.00009: Effects of plasmonic environment on electric and magnetic dipole spontaneous emission Rabia Hussain, Yuri Barnakov, Natalia Noginova Luminescence of Eu ions was used to study effects of plasmonic environment on spontaneous emission of magnetic and electric dipoles in several nanostructured systems, including gold nanostrips, gold and silver nanomesh and thin films.~ Significant changes in polarization and radiation patterns were observed in the spectral range of plasmonic resonance. The effects were different for electric and magnetic dipole related transitions. The results are discussed in terms of coupling of emitters with radiative and plasmonic modes with account for losses. We also demonstrate the possibility to map the enhancement factors for magnetic and electric dipoles separately in near field optical studies. [Preview Abstract] |
Tuesday, March 19, 2013 4:18PM - 4:30PM |
J20.00010: Single particle optical investigation of gold-enhanced upconverted fluorescence emission Kory Green, Shuang Fang Lim Near IR excited upconverting nanoparticles (UCNPs) are ideal fluorescent contrast agents, leading to background free bioimaging. However, their fluorescent brightness is hampered by low quantum efficiency due to material limitations. We investigate the plasmonic coupling of 20 nm diameter core NaYF4: Yb, Er upconverting nanoparticles (UCNPs) coupled to both gold nanoparticles and coated in a gold nanoshell. The structures of the UCNPs composites have been verified by transmission electron microscopy (TEM), UV-Vis absorption and fluorescent emission. Spectroscopic studies such as single particle spectra and time resolved decay has been performed to investigate and fine tune the luminescent enhancement. In particular, we have performed time-resolved~spectroscopy between 400 nm and 1700 nm. The monitoring of all relevant energy level transitions, including intermediate levels, contribute to a complete understanding of~the mechanisms at work in plasmonicly enhanced, high-efficiency, small UNCPs. [Preview Abstract] |
Tuesday, March 19, 2013 4:30PM - 4:42PM |
J20.00011: Enhancement of single particle rare earth doped NaYF$_{4}$: Yb, Er emission with gold shell Shuang Lim, Ling Li, Hans Hallen We report on the enhancement in emission of NaYF$_{4}$: Yb, Er upconverting nanoparticles (UCNPs) coated with a gold nanoshell. We have synthesized a doped NaYF$_{4}$ core of 350 nm, with a sufficiently thick undoped NaYF$_{4}$ shell of 65 nm thickness to minimize contact with the gold surface plasmons, and effectively minimizing luminescence quenching. Absorption and fluorescence emission measurements of single NaYF$_{4}$ particles show enhanced absorption in the near infrared and a 1.5 times overall enhanced emission intensity. A relative increase in green/red emission was observed for both gold seed attachment and shell growth, of approximately 1.9 and 2.3 times respectively. Both Au seed attachment and shell growth has been shown to double the green/red emission ratio. The surface plasmon resonance of the UCNP core/Au shell composite is shown to be dependent on the gold shell thickness. Our experimental results are corroborated by finite element calculations. [Preview Abstract] |
Tuesday, March 19, 2013 4:42PM - 4:54PM |
J20.00012: Two-color Surface Plasmon Polariton Assisted Upconversion Luminescence in NaYF$_{4}$:Yb:Tm on Au Nanopillar Arrays Steve Smith, Robert Anderson, Amy Hor, Jon Fisher, Khadijeh Bayat, Mahdi Baroughi, QuocAhn Lu, P. Stanely May Spectroscopic imaging was used to study the surface plasmon polariton (SPP) enhanced upconversion luminescence of NaYF$_{4}$:Tm:Yb nanoparticles embedded in PMMA supported on Au nanopillar arrays. Spatially-resolved upconversion spectra show enhancement in both the visible and near-infrared region of the spectrum, clearly associated with the plasmonic resonances of an engineered periodic array of nanopillars. The array has a lattice resonance associated with the SPP near 980nm, at the peak absorption of the Yb$^{3+}$ ion, while the local surface plasmon resonance (LSPR) of the individual pillars is seen to enhance the near-infrared emission of Tm$^{3+}$ near 800nm. The combined effect results in a significantly higher enhancement of the near-infrared emission when compared to the visible upconversion lines of Tm$^{3+}$, consistent with the interpretation of sequential surface plasmon assisted absorption and emission at two separate and disparate energies. The presence of SPP and LSPR were confirmed by spectrally resolved reflectivity, and the mechanism for luminescence enhancement was investigated by time resolved measurements of the luminescence decay. Reflectivity measurements are compared to finite difference time domain simulations (FDTD). [Preview Abstract] |
Tuesday, March 19, 2013 4:54PM - 5:30PM |
J20.00013: Beller Lectureship: Surface Plasmon Laser Action Near the Surface Plasmon Frequency Invited Speaker: Rupert F. Oulton Lasers have recently been scaled in size beyond the diffraction limit of light by using electromagnetic surface excitations of metals. In this talk, I will discuss our approach to constructing surface plasmon (SP) lasers using semiconductor materials and outline potential applications that exploit the strong interaction of nanoscale light with matter. I will also present recent results on room temperature SPs lasers operating near the SP frequency by utilizing Zinc Oxide as a gain material combined with a Silver substrate. Surface plasmon lasers could be the most efficient and compact method of delivering optical energy to the nanoscale. There are two benefits: firstly, the efficiently generated (focused) coherent laser field can be extremely intense; and secondly, vacuum fluctuations within the laser cavity are considerably stronger than in free space. Consequently, SP lasers have the unique ability to drastically enhance both coherent and incoherent light-matter interactions bringing fundamentally new capabilities to bio-sensing, data storage, photolithography and optical communications. While there is a great deal of research to do on SP laser systems, this talk highlights the feasibility of nano-scale light sources and the potential of laser science at the nanoscale. [Preview Abstract] |
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