The research leading to these results has received funding from the European Research Council under the European Community&#8217;s Seventh Framework Program FP7/2007&#8211;2013 Grant Agreement no 306772 and Grant ERC-2007-StG No. 203872-COMOSYEL. This work is &#8232;also partially funded by the Agence Nationale de la Recherche (ANR) under Grant Plastips (ANR-09-BLAN-0049). A. S. thanks a postdoctoral scholarship from the R&#233;gion de Bourgogne under the PARI program. M.S. acknowledges a stipend from the Chinese Scholarship Council. D.Z. acknowledges support from the National Natural Science Foundation of China for Grants 11004182 and 61036005.

1. Synthesis of a Colloidal Solution of Silver&#160;Nanowires
Silver nanowires (Ag NWs) with smooth surface and homogeneous structure are synthesized using a modified polyols-assisted method6. In a typical synthesis of Ag NWs, the following procedures are carried out step by step:
<ol>
	<li>Pour 12 ml&#160;ethylene glycol (EG) in a 100 ml&#160;precleaned, round-bottomed capped flask.</li>
	<li>Heat the solution at 150 &#176;C for 1 hr&#160;in the oil bath (dimethylsilicone) with magnetic stirring at 260 rpm.</li>
	<li>Add 4 ml&#160;AgNO3 (0.2 M in EG solution) by dropping. During this process, the color of the reaction solution changes from colorless to transparent bright yellow, which indicates the growth of silver crystal seeds.</li>
	<li>Slowly inject 4 ml poly-(vinylpyrrolidone) (PVP) solution (the concentration is 22.2 mg/ml&#160;in EG solution) in the reaction solution with a pipette. In the reaction, EG serves as both the solvent and reducing agent, and the PVP enables the silver single crystal to grow along a certain direction.</li>
	<li>Cover the reaction flask with a cap. After 150 min, the color of the solution changes from light yellow to sage green. Finally the colloid appears turbid silver-grey.</li>
	<li>Stop the reaction by placing the flask in an ice-cold water bath to decrease the temperature of the solution.</li>
	<li>Transfer 1 ml&#160;of the colloidal solution to a centrifuge tube filled with 3 ml&#160;of acetone.</li>
	<li>Centrifuge the tube at 600 x&#160;g for 25 min.</li>
	<li>Remove the supernatant and add 4 ml&#160;of DI water.</li>
	<li>Repeat steps 1.8-1.9 at least 3x to remove the excess of EG and PVP.</li>
</ol>
2. Preparing Macroscopic Alignment Landmarks on a Glass Substrate by Electron-beam Lithography
<ol>
	<li>Clean a microscope cover glass N&#176;1 &#189; calibrated for oil immersion microscopy in a diluted concentrated soap solution [1:3] using an ultrasonic bath.</li>
	<li>Rinse first in a large volume of DI water, followed by a second wash with isopropanol. Blow-dry the cover slip with nitrogen.</li>
	<li>Pipette 160 ml&#160;of poly(methyl methacrylate) (PMMA) electron beam resist (see table of reagents) and spin coat it the NW covered substrate with the following successive coating parameters:
	<ol>
		<li>10 sec at a speed of 4 x&#160;g and an acceleration of 4 x&#160;g/sec.</li>
		<li>1 sec at a speed of 350 x&#160;g and an acceleration of 200 x&#160;g/sec.</li>
		<li>60 sec at a speed of 700 x&#160;g and an acceleration of 200 x&#160;g/sec.</li>
	</ol>
	</li>
	<li>Bake the sample at 170 &#176;C for 10 min on a hot plate.</li>
	<li>Repeat steps 2.2-2.4&#160;to produce a second layer of resist to facilitate liftoff at the end of the procedure. Use the same electron-beam resist for both layers.</li>
	<li>Sputter a thin conductive gold layer (20 nm) on the top of the sample before proceeding to electron beam lithography.</li>
	<li>Transfer the sample to an electron-beam microscope equipped for lithography. Using a Faraday cage, set the beam current to 150 pA.</li>
	<li>Expose the sample following the design layout of the grid landmarks with a step size set at 48 nm, a dwell-time per pixel at 0.0243 msec&#160;for a dose of 150 &#181;A/cm2.</li>
	<li>Develop the sample using MIBK (methyl isobutyl ketone): IPA (isopropanol) with a ratio [1:3] for 45 sec. Stop the process by dipping the sample in isopropanol for another 45 sec.</li>
	<li>Transfer the substrate in a metal evaporator operating at a base pressure of 8 x 10-8 mbar. Deposit at an evaporation rate of 0.1 nm/sec 2 nm of Cr (adhesion layer) followed by 70 nm of Au.</li>
	<li>Proceed to a chemical lift-off of the sample using acetone warmed at 70 &#176;C for about 1.5 hr.</li>
</ol>
3. Deposition of the Nanowires on the Substrate
<ol>
	<li>Dilute the nanowire solution in ethanol to obtain a nanowire density on the substrate of about one nanowire every 10 &#181;m2.</li>
	<li>Pipette 50 &#181;l&#160;of the solution and drop-cast it on the prepatterned substrate. Blow&#160;dry with nitrogen.</li>
</ol>
4. Locating the Nanowires by Optical Microscope
<ol>
	<li>Place the substrate decorated with nanowires on a standard calibrated optical microscope.</li>
	<li>Precisely locate the extremities of a series of isolated high-quality nanowires with respect to the closest alignment marks.</li>
</ol>
5. Fabrication of the Electrodes by Electron Beam Lithography, Thermal Evaporation, and Chemical Lift-off
<ol>
	<li>Use the measured positions of the nanowires to design an electrode layout. Incorporate large receiving pads (50 &#181;m x 50 &#181;m) to connect tungsten voltage probes to the electrode reaching the nanowires.</li>
	<li>Pipette 160 ml of poly(methyl methacrylate) (PMMA) electron beam resist (see table of reagents) and spin coat the nanowire-covered substrate with the following successive coating parameters:
	<ol>
		<li>10 sec at a speed of 4 x&#160;g and an acceleration of 4 x&#160;g/sec.</li>
		<li>1 sec at a speed of 350 x&#160;g and an acceleration of 200 x&#160;g/sec.</li>
		<li>60 sec at a speed of 700 x&#160;g and an acceleration of 200 x&#160;g/sec.</li>
	</ol>
	</li>
	<li>Bake the sample at 170 &#176;C for 10 min on a hot plate.</li>
	<li>Repeat steps 5.2-5.3&#160;to produce a second layer of resist to facilitate liftoff at the end of the procedure. Use the same electron-beam resist for both layers.</li>
	<li>Sputter a thin conductive gold layer (20 nm) on the top of the sample before proceeding to electron beam lithography.</li>
	<li>Transfer the sample to an electron-beam microscope equipped for lithography. Using a Faraday cage, set the beam current to 150 pA.</li>
	<li>Using the alignment marks, calibrate the coordinate system of the electron-beam microscope.</li>
	<li>Expose the sample following the design layout with a step size set at 48 nm, a dwell-time per pixel at 0.0243 msec for a dose of 150 &#181;A/cm2.</li>
	<li>Develop the sample using MIBK (methyl isobutyl ketone): IPA (isopropanol) with a ratio [1:3] for 45 sec. Stop the process by dipping the developed sample in isopropanol for another 45 sec.</li>
	<li>Transfer the substrate in a metal evaporator operating at a base pressure of 8 x 10-8 mbar. Deposit at an evaporation rate of 0.1 nm/sec, 2 nm of Cr (adhesion layer) followed by 70 nm of Au.</li>
	<li>Proceed to a chemical lift-off of the sample using acetone warmed at 70 &#176;C for about 1.5 hr.</li>
</ol>
6. Transfer to a Surface Plasmon Leakage Radiation Microscope
<ol>
	<li>Set up a surface plasmon leakage microscope equipped with a high numerical aperture objective (N.A.&#62;1) and a two-axis piezoelectric stage to adjust sample position.</li>
	<li>Prepare a collimated Gaussian beam from a near-infrared laser. Longer excitation wavelength provides longer plasmon propagation distance. Align the beam in the microscope. The diameter of the collimated beam should overfill the entrance pupil of the microscope. This insures the formation of a diffraction-limited focal spot at the glass/air interface.</li>
	<li>With the help of beam splitters and a series of relay lenses positioned at one exit port of the microscope, form two planes conjugate with the object plane and with the Fourier plane (objective back focal plane), respectively. Place two charge-coupled device (CCD) cameras at the location of these conjugate planes.</li>
	<li>Using the piezoelectric stage, align the extremity of a selected contacted nanowire to overlap the focal spot. Adjust the position to maximize light coupling into the plasmon mode.</li>
	<li>Connect a regulated power supply to the receiving pads of the electrical terminals with tungsten tips mounted on three-dimensional mechanical probers. Insert a low gain current-to-voltage converter (gain 10mA/V) or a current meter in the circuitry.</li>
	<li>Monitor the applied bias, the current flowing through the nanowire and the intensity distributions recorded by the two CCDs cameras.</li>
</ol>

<ol>
	<li>Ozbay, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmonics:+Merging+photonics+and+electronics+at+nanoscale+dimensions.">Plasmonics: Merging photonics and electronics at nanoscale dimensions.</a> Sci. 311 (5758), 189-193 (1126).</li><li>Zia, R., Schuller, J. A., Chandran, A., Brongersma, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmonics:+the+next+chip-scale+technology.">Plasmonics: the next chip-scale technology.</a> Mater. Today. 9 (7), (2006).</li><li>Genet, W., C, S. I., Bozhevolnyi, <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface-plasmon+circuitry.">Surface-plasmon circuitry.</a> Phys. Today. 61 (5), 44-50 (2008).</li><li>Pyayt, A. L., Wiley, B., Xia, Y., Chen, A., Dalton, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integration+of+photonic+and+silver+nanowire+plasmonic+waveguides.">Integration of photonic and silver nanowire plasmonic waveguides.</a> Nat. Nanotechnol. 3, 660-665 (2008).</li><li>Dickson, R. M., Lyon, L. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unidirectional+Plasmon+Propagation+in+Metallic+Nanowires.">Unidirectional Plasmon Propagation in Metallic Nanowires.</a> J. Phys. Chem. B. 104, 6095-6098 (2000).</li><li>Kan, C. X., Zhu, J. -. J., Zhu, X. -. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silver+nanostructures+with+well-controlled+shapes-synthesis,+characterization+and+growth+mechanism.">Silver nanostructures with well-controlled shapes-synthesis, characterization and growth mechanism.</a> J. Phys. D: Appl. Phys. 41 (15), 155304 (2008).</li><li>Song, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electron-induced+limitation+of+surface+plasmon+propagation+in+silver+nanowires.">Electron-induced limitation of surface plasmon propagation in silver nanowires.</a> Nanotechnol. 24 (9), (2013).</li><li>Drezet, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Leakage+radiation+microscopy+of+surface+plasmonpolaritons.">Leakage radiation microscopy of surface plasmonpolaritons.</a> Mater. Sci. Eng. B. 148, 220-229 (2007).</li><li>Song, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+Symmetry-Selected+Corner+Plasmon+Modes+in+Penta-Twinned+Crystalline+Ag+Nanowires.">Imaging Symmetry-Selected Corner Plasmon Modes in Penta-Twinned Crystalline Ag Nanowires.</a> ACS Nano. 5 (7), 5874-5880 (1021).</li><li>Miljkovi&#263;, V., Shegai, T., Johansson, P., K&#228;ll, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simulating+light+scattering+from+supported+plasmonic+nanowires.">Simulating light scattering from supported plasmonic nanowires.</a> Opt. Express. 20 (10), 10816-10826 (2012).</li><li>Massenot, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polymer-metal+waveguides+characterization+by+Fourier+plane+leakage+radiation+microscopy.">Polymer-metal waveguides characterization by Fourier plane leakage radiation microscopy.</a> Appl. Phys. Lett. 91, (2007).</li><li>Ditlbacher, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Silver+Nanowires+as+Surface+Plasmon+Resonators.">Silver Nanowires as Surface Plasmon Resonators.</a> Phys. Rev. Lett. 95 (25), 257403 (2005).</li><li>Margueritat, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Influence+of+the+number+of+nanoparticles+on+the+enhancement+properties+of+surface-enhanced+Raman+scattering+active+area:+sensitivity+versus+repeatability.">Influence of the number of nanoparticles on the enhancement properties of surface-enhanced Raman scattering active area: sensitivity versus repeatability.</a> ACS Nano. 5 (3), 1630-1638 (2011).</li><li>Rivera, T. P., Lecarme, O., Hartmann, J., Rossitto, E., Berton, K., Peyrade, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assisted+convective-capillary+force+assembly+of+gold+colloids+in+a+microfluidic+cell:+Plasmonic+properties+of+deterministic+nanostructures.">Assisted convective-capillary force assembly of gold colloids in a microfluidic cell: Plasmonic properties of deterministic nanostructures.</a> J. Vac. Sci. Technol. B. 26, 2513-2519 (2008).</li><li>Cronin, S. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thermoelectric+investigation+of+bismuth+nanowires.">Thermoelectric investigation of bismuth nanowires.</a> , 554-557 (1999).</li><li>Cronin, S. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Making+electrical+contacts+yo+nanowires+with+a+thick+oxide+coating.">Making electrical contacts yo nanowires with a thick oxide coating.</a> Nanotechnol. 13 (5), 653 (2002).</li><li>Colasdes Francs, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integrated+plasmonic+waveguides:+A+mode+solver+based+on+density+of+states+formulation.">Integrated plasmonic waveguides: A mode solver based on density of states formulation.</a> Phys. Rev. B. 80 (11), 115419 (2009).</li><li>Stahlmecke, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electromigration+in+self-organized+single-crystalline+silver+nanowires.">Electromigration in self-organized single-crystalline silver nanowires.</a> Appl. Phys. Lett. 88 (5), 053122 (2006).</li><li>Kim, F., Sohn, K., Wu, J., Huang, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+Synthesis+of+Gold+Nanowires+in+Acidic+Solutions.">Chemical Synthesis of Gold Nanowires in Acidic Solutions.</a> J. American Chem. Soc. 130 (5), 14442-14443 (2008).</li><li>Novotny, L., Hecht, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Princ. Nano-Opt. , (2006).</li><li>Wang, W. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dip-pen+nanolithography+of+electrical+contacts+to+single-walled+carbon+nanotubes.">Dip-pen nanolithography of electrical contacts to single-walled carbon nanotubes.</a> ACS Nano. 3 (11), 35443-33551 (2009).</li><li>Kuzyk, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dielectrophoresis+at+the+nanoscale.">Dielectrophoresis at the nanoscale.</a> Electrophoresis. 32 (17), 2307-2313 (2011).</li><li>Freer, E. M., Grachev, O., Duan, X., Martin, S., Stumbo, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-yield+self-limiting+single-nanowire+assembly+with+dielectrophoresis.">High-yield self-limiting single-nanowire assembly with dielectrophoresis.</a> Nat. Technol. 5, 525-530 (2010).</li><li>Huang, J. -. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Atomically-flat+single-crystalline+gold+nanostructures+for+plasmonic+nanocircuitry.">Atomically-flat single-crystalline gold nanostructures for plasmonic nanocircuitry.</a> Nat. Comm. 1, 150 (2010).</li></ol>

The authors declare that they have no competing financial interests.

The synthesis uses an excess of chemical surfactant remaining bound to the surface of the nanowire as illustrated in the transmission electron micrograph of Figure 9(a). This layer creates a dielectric barrier preventing the current to flow through the electrode-nanowire interface. Figures 10(a)&#160;and (b)&#160;show typical examples of the current-voltage characteristics. Sharp current steps at certain biases punctuate the curves. These steps occur when the current den...

Plasmonics aims at merging electronics and photonics in a shared physical support via the mediation of an electron density wave called a surface plasmon polariton1,2,3. Surface plasmon can travel in various waveguide geometries and interfaces. Among them, metal nanowires are especially desirable. As quasi-one dimensional structures they drastically confine the plasmon field to deep subwavelength scale while acting as electrical interconnects capable of sustaining an electron flow as depicted by the artistic drawing of Figure 1.
Both surface plasmon propagation and electron transport are sensitive to structural inhomogeneities of the nanowire (e.g. kinks, crystalline defects, etc.). Because they can grow as a single crystal with few defects, chemically-synthesized metal nanowires6 typically provide improved transport performances over amorphous metal nanowires fabricated by top-down approaches (e.g. electron beam lithography)12. The realization of a plasmonic network unit cell requires transferring the nanowires from a colloidal solution to a glass substrate. Without any specific complex prepatterning like surface functionalization13 or self-assembly techniques14, nanowires are generally randomly oriented on the substrate. This uncontrolled distribution of orientations drastically complicates the electrical connection of the nanowire to an outside power source.
In this article, randomly oriented chemically-synthesized silver nanowires are successfully contacted by source and drain electrical terminals. To this purpose optical microscopy is combined with electron-beam lithography to precisely locate the nanowire and create electrical contacts15,16. A characterization procedure evaluating the electro-plasmonic performances of the circuitry is described. After electrode fabrication, the contacted nanowires are transferred to a surface plasmon leakage radiation microscope for analyzing the effect of an electron flow on the propagation of surface plasmons. The microscope uses an inverted base equipped with a high numerical aperture oil-immersion objective and two charge-coupled device (CCD) cameras placed at the conjugate object plane and conjugate Fourier plane, respectively. These two conjugate planes provide complementary information on surface plasmon properties. Details of the propagation are directly inferred from image plane analysis, while the momentum distribution is visualized by Fourier plane imaging9.
Surface plasmons are excited in an individual nanowire by focusing a near-infrared laser beam in a diffraction-limited spot at the glass/air interface. When a nanowire extremity is aligned inside the focal region, the scattered incident laser light creates a broad distribution of wave-vectors, some of them resonant with the excitation of a surface plasmon. The propagation of this surface wave is visualized either by collecting the leakage of the mode emitted in the substrate or by observing the plasmon scattered at the nanowire distal end. The propagation length and effective index of the leaky surface plasmon mode are measured by analyzing the intensity distributions in a dual-plane leakage radiation microscopy.
Once a surface plasmon develops in the nanowire, the drain and source terminals at each extremity of the nanowire are connected to a regulated voltage supply. The CCD cameras monitor in real time the surface plasmon properties as a function of current flowing through the nanowire. For each value of the electrical transfer characteristic, the effective index and the propagation length of the surface plasmon mode are determined. This procedure enables to estimate the limitation of a nanowire-based circuitry to simultaneously sustain the transport of electrons and plasmons7.

<table><tbody><tr><td>DMEM</td><td>Invitrogen</td><td>ABCD1234</td><td></td></tr><tr><td>Ethylene glycol (EG)</td><td>Sinopharm Chemical Reagent Co., Ltd</td><td>T20111130</td><td></td></tr><tr><td>PMMA</td><td>Allresist</td><td>AR-P 679</td><td></td></tr><tr><td>Acetone Analar Normapur</td><td>VWR Prolabo</td><td>20066.296</td><td></td></tr><tr><td>Isopropanol (IPA) Analar Normapur</td><td>VWR Prolabo</td><td>20842.298</td><td></td></tr><tr><td>AgNO&lt;sub&gt;3&lt;/sub&gt;</td><td>Sinopharm Chemical Reagent Co., Ltd</td><td>20080826</td><td></td></tr><tr><td>Poly-(vinylpyrrolidone) (PVP)</td><td>Aladdin Chemistry Co., Ltd</td><td>1041671-31744</td><td></td></tr><tr><td>Dimethysilicone</td><td>Sinopharm Group Company Limited</td><td>H201-500</td><td></td></tr><tr><td>Propylene Glycol Methyl Ether Acetate</td><td>Microchemicals Gmbh</td><td>AZ EBR</td><td></td></tr><tr><td>Inverted optical microscope</td><td>Nikon</td><td>TE 2000</td><td></td></tr><tr><td>Microscope objective</td><td>Nikon</td><td>1.49/100X TIRF Plan-Apo</td><td></td></tr><tr><td>CCD Cameras (2x)</td><td>Andor</td><td>Luca-S</td><td></td></tr><tr><td>Regulated power supply</td><td>RHK</td><td>SPM 1000</td><td></td></tr><tr><td>Acquisition data</td><td>RHK</td><td>SPM 1000</td><td></td></tr><tr><td>Current to voltage converter</td><td>homemade</td><td>Gain 10 mA/V</td><td></td></tr><tr><td>Electron beam microscope</td><td>JEOL</td><td>FEG 6500</td><td></td></tr><tr><td>Lithography addon</td><td>RAITH</td><td>Elphy</td><td></td></tr><tr><td>Spincoater</td><td>PRIMUS</td><td>STT15</td><td></td></tr><tr><td>Thermal evaporator</td><td>PLASSYS</td><td>MEB 400</td><td></td></tr><tr><td>Micrometer probing stage (2x)</td><td>S&amp;Uuml;SS MicroTec</td><td>PH110</td><td></td></tr><tr><td>Piezoelectric stage</td><td>Mad City Labs</td><td>Nano LP100</td><td></td></tr></tbody></table>

evaluating plasmonic transport in current-carrying silver nanowires

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information support1,2,3. In this context, metal nanowires are especially desirable for realizing dense routing networks4. A prerequisite to operate such shared nanowire-based platform relies on our ability to electrically contact individual metal nanowires and efficiently excite surface plasmon polaritons5 in this information support. In this article, we describe a protocol to bring electrical terminals to chemically-synthesized silver nanowires6 randomly distributed on a glass substrate7. The positions of the nanowire ends with respect to predefined landmarks are precisely located using standard optical transmission microscopy before encapsulation in an electron-sensitive resist. Trenches representing the electrode layout are subsequently designed by electron-beam lithography. Metal electrodes are then fabricated by thermally evaporating a Cr/Au layer followed by a chemical lift-off. The contacted silver nanowires are finally transferred to a leakage radiation microscope for surface plasmon excitation and characterization8,9. Surface plasmons are launched in the nanowires by focusing a near infrared laser beam on a diffraction-limited spot overlapping one nanowire extremity5,9. For sufficiently large nanowires, the surface plasmon mode leaks into the glass substrate9,10. This leakage radiation is readily detected, imaged, and analyzed in the different conjugate planes in leakage radiation microscopy9,11. The electrical terminals do not affect the plasmon propagation. However, a current-induced morphological deterioration of the nanowire drastically degrades the flow of surface plasmons. The combination of surface plasmon leakage radiation microscopy with a simultaneous analysis of the nanowire electrical transport characteristics reveals the intrinsic limitations of such plasmonic circuitry.

Figure 2(a)&#160;shows a scanning electron micrograph of a typical 10 mm long Ag nanowire synthesized using the protocol outlined above. The width of the nanowire is here 200 nm as shown in the close up view of the left extremity in Figure&#160;2(b). The figure readily shows the five-fold symmetry of the crystal growth. There are no visible defects on the surface of the nanowire (e.g. kinks, particles, etc.). The synthesis leads to a large distribution of nanowire lengt...

Watch this Scientific Journal Video about Evaluating Plasmonic Transport in Current-carrying Silver Nanowires at JoVE.com

Evaluating Plasmonic Transport in Current-carrying Silver Nanowires

Silver nanowires can simultaneously transport electrons and optical information in the form of surface plasmons. A procedure is described here to realize such a shared circuitry and the limitations at propagating both information carriers are evaluated.

Plasmonics is an emerging technology capable of simultaneously transporting a plasmonic signal and an electronic signal on the same information ...

evaluating-plasmonic-transport-in-current-carrying-silver-nanowires

Research

JoVE Journal

Engineering

5.2K Views.  Université de Bourgogne. Silver nanowires can simultaneously transport electrons and optical information in the form of surface plasmons. A procedure is described here to realize such a shared circuitry and the limitations at propagating both information carriers are evaluated.

Video: Evaluating Plasmonic Transport in Current-carrying Silver Nanowires

Template Directed Synthesis of Plasmonic Gold Nanotubes with Tunable IR Absorbance

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) membranes have been under development since the 1990's and have become a common method to template the synthesis of high aspect ratio nanostructures, mostly by electrochemical growth or pore-wetting. Recently, these membranes have become commercially available in a wide range of pore sizes and densities, leading to an extensive library of functional nanostructures being synthesized from AAO membranes. These include composite nanorods, nanowires and nanotubes made of metals, inorganic materials or polymers 3-10. Nanoporous membranes have been used to synthesize nanoparticle and nanotube arrays that perform well as refractive index sensors, plasmonic biosensors, or surface enhanced Raman spectroscopy (SERS) substrates 11-16, as well as a wide range of other fields such as photo-thermal heating 17, permselective transport 18, 19, catalysis 20, microfluidics 21, and electrochemical sensing 22, 23. Here, we report a novel procedure to prepare gold nanotubes in AAO membranes. Hollow nanostructures have potential application in plasmonic and SERS sensing, and we anticipate these gold nanotubes will allow for high sensitivity and strong plasmon signals, arising from decreased material dampening 15.

Solution-suspendable gold nanotubes with controlled dimensions can be synthesized by electrochemical deposition in porous anodic aluminum oxide (AAO) membranes using a hydrophobic polymer core. Gold nanotubes and nanotube arrays hold promise for applications in plasmonic biosensing, surface-enhanced Raman spectroscopy, photo-thermal heating, ionic and molecular transport, microfluidics, catalysis and electrochemical sensing.

A nearly parallel array of pores can be produced by anodizing aluminum foils in acidic environments1, 2. Applications of anodic aluminum oxide (AAO) ...

Chemistry

Utilization of Plasmonic and Photonic Crystal Nanostructures for Enhanced Micro- and Nanoparticle Manipulation

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological research. Perhaps the most widely used physical force to achieve noninvasive manipulation of small particles has been dielectrophoresis(DEP).1 However, DEP on its own lacks the versatility and precision that are desired when manipulating cells since it is traditionally done with stationary electrodes. Optical tweezers, which utilize a three dimensional electromagnetic field gradient to exert forces on small particles, achieve this desired versatility and precision.2 However, a major drawback of this approach is the high radiation intensity required to achieve the necessary force to trap a particle which can damage biological samples.3 A solution that allows trapping and sorting with lower optical intensities are optoelectronic tweezers (OET) but OET's have limitations with fine manipulation of small particles; being DEP-based technology also puts constraint on the property of the solution.4,5
This video article will describe two methods that decrease the intensity of the radiation needed for optical manipulation of living cells and also describe a method for orientation control. The first method is plasmonic tweezers which use a random gold nanoparticle (AuNP) array as a substrate for the sample as shown in Figure 1. The AuNP array converts the incident photons into localized surface plasmons (LSP) which consist of resonant dipole moments that radiate and generate a patterned radiation field with a large gradient in the cell solution. Initial work on surface plasmon enhanced trapping by Righini et al and our own modeling have shown the fields generated by the plasmonic substrate reduce the initial intensity required by enhancing the gradient field that traps the particle.6,7,8 The plasmonic approach allows for fine orientation control of ellipsoidal particles and cells with low optical intensities because of more efficient optical energy conversion into mechanical energy and a dipole-dependent radiation field. These fields are shown in figure 2 and the low trapping intensities are detailed in figures 4 and 5. The main problems with plasmonic tweezers are that the LSP's generate a considerable amount of heat and the trapping is only two dimensional. This heat generates convective flows and thermophoresis which can be powerful enough to expel submicron particles from the trap.9,10 The second approach that we will describe is utilizing periodic dielectric nanostructures to scatter incident light very efficiently into diffraction modes, as shown in figure 6.11 Ideally, one would make this structure out of a dielectric material to avoid the same heating problems experienced with the plasmonic tweezers but in our approach an aluminum-coated diffraction grating is used as a one-dimensional periodic dielectric nanostructure. Although it is not a semiconductor, it did not experience significant heating and effectively trapped small particles with low trapping intensities, as shown in figure 7. Alignment of particles with the grating substrate conceptually validates the proposition that a 2-D photonic crystal could allow precise rotation of non-spherical micron sized particles.10 The efficiencies of these optical traps are increased due to the enhanced fields produced by the nanostructures described in this paper.

Plasmonic tweezers and photonic crystal nanostructures are shown to produce useful enhancements in the efficiency and orientation control of optically trapping micro- and nano-particles.

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological ...

Bioengineering

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

Integration of Light Trapping Silver Nanostructures in Hydrogenated Microcrystalline Silicon Solar Cells by Transfer Printing

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly known as plasmonic effects, play an important role. Research in this field has, however, been impeded owing to the difficulty of fabricating devices containing the desired functional metal nanostructures. In order to provide a viable strategy to this issue, we herein show a transfer printing-based approach that allows the quick and low-cost integration of designed metal nanostructures with a variety of device architectures, including solar cells. Nanopillar poly(dimethylsiloxane) (PDMS) stamps were fabricated from a commercially available nanohole plastic film as a master mold. On this nanopatterned PDMS stamps, Ag films were deposited, which were then transfer-printed onto block copolymer (binding layer)-coated hydrogenated microcrystalline Si (&#181;c-Si:H) surface to afford ordered Ag nanodisk structures. It was confirmed that the resulting Ag nanodisk-incorporated &#181;c-Si:H solar cells show higher performances compared to a cell without the transfer-printed Ag nanodisks, thanks to plasmonic light trapping effect derived from the Ag nanodisks. Because of the simplicity and versatility, further device application would also be feasible thorough this approach.

A viable transfer printing-based methodology to introduce plasmonic metal nanostructures in solar cells is described. Using nanopillar poly(dimethylsiloxane) stamps, an Ag-based ordered nanodisk array was integrated with standard hydrogenated microcrystalline Si solar cells, which led to improved device performances due to plasmonic light trapping.

One of the potential applications of metal nanostructures is light trapping in solar cells, where unique optical properties of nanosized metals, commonly ...

Measurement of Scattering Nonlinearities from a Single Plasmonic Nanoparticle

Plasmonics, which are based on the collective oscillation of electrons due to light excitation, involve strongly enhanced local electric fields and thus have potential applications in nonlinear optics, which requires extraordinary optical intensity. One of the most studied nonlinearities in plasmonics is nonlinear absorption, including saturation and reverse saturation behaviors. Although scattering and absorption in nanoparticles are closely correlated by the Mie theory, there has been no report of nonlinearities in plasmonic scattering until very recently. 
Last year, not only saturation, but also reverse saturation of scattering in an isolated plasmonic particle was demonstrated for the first time. The results showed that saturable scattering exhibits clear wavelength dependence, which seems to be directly linked to the localized surface plasmon resonance (LSPR). Combined with the intensity-dependent measurements, the results suggest the possibility of a common mechanism underlying the nonlinear behaviors of scattering and absorption. These nonlinearities of scattering from a single gold nanosphere (GNS) are widely applicable, including in super-resolution microscopy and optical switches. 
In this paper, it is described in detail how to measure nonlinearity of scattering in a single GNP and how to employ the super-resolution technique to enhance the optical imaging resolution based on saturable scattering. This discovery features the first super-resolution microscopy based on nonlinear scattering, which is a novel non-bleaching contrast method that can achieve a resolution as low as l/8 and will potentially be useful in biomedicine and material studies.

Saturable and reverse saturable scattering were discovered in isolated plasmonic particles and adopted as a novel non-bleaching contrast method in super-resolution microscopy. Here the experimental procedures of detecting and extracting nonlinear scattering are explained in detail, as well as how to enhance resolution with the aid of saturated excitation microscopy.

Plasmonics, which are based on the collective oscillation of electrons due to light excitation, involve strongly enhanced local electric fields and thus ...

A Fabrication Method for Highly Stretchable Conductors with Silver Nanowires

Stretchable electronics are identified as a key technology for electronic applications in the next generation. One of the challenges in fabrication of stretchable electronic devices is the preparation of stretchable conductors with great mechanical stability. In this study, we developed a simple fabrication method to chemically solder the contact points between silver nanowire (AgNW) networks. AgNW nanomesh was first deposited on a glass slide via spray coating method. A reactive ink composed of silver nanoparticle (AgNPs) precursors was applied over the spray coated AgNW thin films. After heating for 40 min, AgNPs were preferentially generated over the nanowire junctions to solder the AgNW nanomesh, and reinforced the conducting network. The chemically modified AgNW thin film was then transferred to polyurethane (PU) substrates by casting method. The soldered AgNW thin films on PU exhibited no obvious change in electrical conductivity under stretching or rolling process with elongation strains up to 120%.

A simple synthesis method is used to chemically solder silver nanowire thin film to fabricate highly stretchable and conductive metal conductors.

Stretchable electronics are identified as a key technology for electronic applications in the next generation. One of the challenges in fabrication of ...

Colloidal Synthesis of Nanopatch Antennas for Applications in Plasmonics and Nanophotonics

We present a method for colloidal synthesis of silver nanocubes and the use of these in combination with a smooth gold film, to fabricate plasmonic nanoscale patch antennas. This includes a detailed procedure for the fabrication of thin films with a well-controlled thickness over macroscopic areas using layer-by-layer deposition of polyelectrolyte polymers, namely poly(allylamine) hydrochloride (PAH) and polystyrene sulfonate (PSS). These polyelectrolyte spacer layers serve as a dielectric gap in between silver nanocubes and a gold film. By controlling the size of the nanocubes or the gap thickness, the plasmon resonance can be tuned from about 500 nm to 700 nm. Next, we demonstrate how to incorporate organic sulfo-cyanine5 carboxylic acid (Cy5) dye molecules into the dielectric polymer gap region of the nanopatch antennas. Finally, we show greatly enhanced fluorescence of the Cy5 dyes by spectrally matching the plasmon resonance with the excitation energy and the Cy5 absorption peak. The method presented here enables the fabrication of plasmonic nanopatch antennas with well-controlled dimensions utilizing colloidal synthesis and a layer-by-layer dip-coating process with the potential for low cost and large-scale production. These nanopatch antennas hold great promise for practical applications, for example in sensing, ultrafast optoelectronic devices and for high-efficiency photodetectors.

A protocol for the colloidal synthesis of silver nanocubes and fabrication of plasmonic nanoscale patch antennas with sub-10 nm gaps is presented.

We present a method for colloidal synthesis of silver nanocubes and the use of these in combination with a smooth gold film, to fabricate plasmonic ...

Plasmonic Trapping and Release of Nanoparticles in a Monitoring Environment

Plasmonic tweezers use surface plasmon polaritons to confine polarizable nanoscale objects. Among the various designs of plasmonic tweezers, only a few can observe immobilized particles. Moreover, a limited number of studies have experimentally measured the exertable forces on the particles. The designs can be classified as the protruding nanodisk type or the suppressed nanohole type. For the latter, microscopic observation is extremely challenging. In this paper, a new plasmonic tweezer system is introduced to monitor particles, both in directions parallel and orthogonal to the symmetric axis of a plasmonic nanohole structure. This feature enables us to observe the movement of each particle near the rim of the nanohole. Furthermore, we can quantitatively estimate the maximal trapping forces using a new fluidic channel.

A microchip fabrication process that incorporates plasmonic tweezers is presented here. The microchip enables the imaging of a trapped particle to measure maximal trapping forces.

Plasmonic tweezers use surface plasmon polaritons to confine polarizable nanoscale objects. Among the various designs of plasmonic tweezers, only a few ...

Fabrication of Periodic Gold Nanocup Arrays Using Colloidal Lithography

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing in combination with new nanofabrication techniques. A plasmon is a quantum of charge density oscillation that lends nanoscale metals such as gold and silver unique optical properties. In particular, gold and silver nanoparticles exhibit localized surface plasmon resonances-collective charge density oscillations on the surface of the nanoparticle-in the visible spectrum. Here, we focus on the fabrication of periodic arrays of anisotropic plasmonic nanostructures. These half-shell (or nanocup) structures can exhibit additional unique light-bending and polarization-dependent optical properties that simple isotropic nanostructures cannot. Researchers are interested in the fabrication of periodic arrays of nanocups for a wide variety of applications such as low-cost optical devices, surface-enhanced Raman scattering, and tamper indication. We present a scalable technique based on colloidal lithography in which it is possible to easily fabricate large periodic arrays of nanocups using spin-coating and self-assembled commercially available polymeric nanospheres. Electron microscopy and optical spectroscopy from the visible to near-infrared (near-IR) was performed to confirm successful nanocup fabrication. We conclude with a demonstration of the transfer of nanocups to a flexible, conformal adhesive film.

We demonstrate the fabrication of periodic gold nanocup arrays using colloidal lithographic techniques and discuss the importance of nanoplasmonic films.

Within recent years, the field of plasmonics has exploded as researchers have demonstrated exciting applications related to chemical and optical sensing ...

Performing Spectroscopy on Plasmonic Nanoparticles with Transmission-Based Nomarski-Type Differential Interference Contrast Microscopy

Differential interference contrast (DIC) microscopy is a powerful imaging tool that is most commonly employed for imaging microscale objects using visible-range light. The purpose of this protocol is to detail a proven method for preparing plasmonic nanoparticle samples and performing single particle spectroscopy on them with DIC microscopy. Several important steps must be followed carefully in order to perform repeatable spectroscopy experiments. First, landmarks can be etched into the sample substrate, which aids in locating the sample surface and in tracking the region of interest during experiments. Next, the substrate must be properly cleaned of debris and contaminants that can otherwise hinder or obscure examination of the sample. Once a sample is properly prepared, the optical path of the microscope must be aligned, using Kohler Illumination. With a standard Nomarski style DIC microscope, rotation of the sample may be necessary, particularly when the plasmonic nanoparticles exhibit orientation-dependent optical properties. Because DIC microscopy has two inherent orthogonal polarization fields, the wavelength-dependent DIC contrast pattern reveals the orientation of rod-shaped plasmonic nanoparticles. Finally, data acquisition and data analyses must be carefully performed. It is common to represent DIC-based spectroscopy data as a contrast value, but it is also possible to present it as intensity data. In this demonstration of DIC for single particle spectroscopy, the focus is on spherical and rod-shaped gold nanoparticles.

The goal of this protocol is to detail a proven approach for the preparation of plasmonic nanoparticle samples and for performing single particle spectroscopy on them with differential interference contrast (DIC) microscopy.

Evaluating Plasmonic Transport in Current-carrying Silver Nanowires

Samenvatting

Meer video's verkennen

Hoofdstukken in deze video