Long-Range Energy Transport via Plasmonic Propagation in a

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Long-range Energy Transport via Plasmonic Propagation in a Supramolecular Organic Waveguide Joseph J. Armao, Pierre Rabu, Emilie Moulin, and Nicolas Giuseppone Nano Lett., Just Accepted Manuscript • DOI: 10.1021/acs.nanolett.6b00581 • Publication Date (Web): 17 Mar 2016 Downloaded from http://pubs.acs.org on March 18, 2016

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Long-range Energy Transport via Plasmonic Propagation in a Supramolecular Organic Waveguide Joseph J. Armao IV,‡ Pierre Rabu,§ Emilie Moulin,‡ and Nicolas Giuseppone‡,* ‡

SAMS research group, University of Strasbourg, Institut Charles Sadron, CNRS, 23 rue du

Loess, BP 84047, 67034 Strasbourg Cedex 2 (France) §

Institut de Physique et Chimie des Matériaux de Strasbourg, University of Strasbourg, CNRS,

23 rue du Loess, BP 43, 67034 Strasbourg Cedex 2 (France)

ABSTRACT. Energy transport in organic materials is dependent on the coherent migration of optically-induced excited states. For instance, in active organic waveguides, the tight packing of dye molecules allows delocalization of excitons over a distance generally limited to at most several hundred nanometers. Here we demonstrate an alternative mechanism of energy transport in a supramolecular organic waveguide which is plasmonic in nature and results in coherent energy propagation superior to 10 micrometers. The optical, electric, and magnetic properties of the doped material support the presence of metallic electrons which couple with and transport incident light. These results show that organic metals constitute a novel class of materials with

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efficient energy transport and of potential interest for optoelectronics, plasmonics, and artificial light-energy harvesting systems. KEYWORDS. Supramolecular Chemistry, Triarylamines, Energy Transport, Organic Metals, Nanophotonics, Plasmonic Waveguides

Novel materials that can be used to manipulate light at the wavelength scale are currently explored for various potential implementations in nanophotonics, including light-harvesting and energy transport devices as well as integrated optical nanocircuits.1–4 In particular, metallic nanostructures such as noble metal nanowires have been shown to produce optical waveguiding effects due to a mechanism which involves plasmonic couplings between an incident light and metallic electrons at their surface.5 Meanwhile, another class of materials under investigation as optical waveguides is based on organic crystals of dyes.6,7 Currently, the exclusive active waveguiding mechanism reported for these materials is based on their photoluminescence whereby an incident laser induces an excited state in small organic molecules. Due to the close packing of the chromophores, it leads to a transfer of energy in the form of exciton-polaritons along coherently stacked structures and usually over short distances, typically on the order of 10 nm to several 100 nm with recent finding suggesting micron length diffusion.8,9,10 Here we show that organic metals (i.e. organic materials with delocalized electrons in their band-like electronic structure) can act as plasmonic waveguides for light and energy transport. In particular, we have synthesized a triarylamine-based supramolecular organic framework that, upon photodoping, displays such metallic characteristics. We demonstrate that, conversely to the previously described organic waveguides, the photoluminescence mechanism is not responsible for their


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observed waveguiding properties. Instead, the waveguiding is plasmonic in nature, due to the coupling of the incident light with the metallic electrons of the single crystal. We show that this new type of plasmonic response in organic materials allows for enhanced energy transport over very long distances (> 10 micrometers). The molecular design and functionality of our waveguide is based on recent findings showing that triarylamine molecules, when properly substituted with amide groups, are able to strongly stack together in the form of various soft self-assemblies (e.g. rods,11–13 fibers,14–16 spheres,17,18 in suspension or in confined space19). Interestingly, we have demonstrated that in such stacked configurations, and when doped by triarylammonium radicals (by using for instance a simple photo-oxidation process in chlorinated solvents),10,12 some of these structures present delocalized metallic electrons in the form of supramolecular polarons that provide them with exceptional conduction properties.14,20,21 Very recently, we have also demonstrated the controlled attachment of soft triarylamine-based nanowires between plasmonic nanoclusters of gold, and we have proved their functioning as organic plasmonic interconnects on the 100 nm scale.22 In such system, the propagation distance is limited by the soft nature of the nanowires which present defects for higher lengths. In addition, the small diameter of the fibers requires larger gold nanoparticles as antennas to launch the plasmon propagation in the nanowires. We now use a more precise supramolecular engineering23,24 to grow single crystals of triarylamine trisamides. In this defect free crystalline organization over tens of micrometers, we highlight their peculiar electronic and optical properties. The controlled crystallization of triarylamine trisacetamide 1 (Figure 1a) was achieved by the slow and differential evaporation of a solvent mixture composed of methanol (b.p. = 64.6 °C, 75 vol%) and toluene (b.p. = 110.6 °C, 25 vol%). The resulting triarylamine crystal grows in the


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form of transparent needles. The corresponding X-ray structure (Figure 1b and Figure S1) reveals the columnar stacking of a repeating motif of two triarylamine units with a “snow-flake” arrangement.13 In this configuration, all central nitrogen atoms of the triarylamine units are collinear in the main axis of the column, while two consecutive triarylamines (which are chiral propellers (Figure 1c(i))13 alternate their handedness (L and D) together with a 60° rotation of their intermolecular dihedral angle. Interestingly, all the three amide functions of each triarylamine are engaged in an infinite string of intercolumnar hydrogen bonds, thus maintaining all the columns at equidistance in the crystalline network (Figure S2a). Between these columns, cavities of 7.9 Å in diameter demonstrate facile inclusion of one molecule of methanol (Figure S2b). Relevant intermolecular stacking distances include a nitrogen-nitrogen distance (d1) of 4.173 Å as well as a stacking distance (d2) of 3.608 Å between two carbons in ortho position to the central nitrogen atom (Figure 1c(ii)). Due to the tilt of the aromatic rings, each aromatic hydrogen on the ortho carbon of one stack points towards the adjacent ortho carbon of the neighboring stack, with a short distance of 2.708 Å (Figure S2c). We also performed a Hirshfeld analysis to quantify the close contacts of 1 in the packing (Figures 1d, S3 and S4).25 First, hydrogen bonding interactions account for 18% of the surface area and display the closest packing to adjacent atoms (red color around the oxygen and hydrogen of the amide, Figure 1d). This indicates their primary influence in dictating the structural geometry. Second, interactions due to close contacts between the ortho carbons contribute to 21% of the surface area (white color over this aromatic region, Figure 1d). These crystals were then photo-oxidized from their suspension in chloroform. Indeed, as demonstrated by UV-Vis-NIR spectroscopy which shows the appearance of characteristic absorption bands around 800 nm, 650 nm, and 400 nm (Figure 1e), irradiation with a 20W


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halogen lamp is sufficient to induce the formation of stable radical cations 1•+ inside the crystal structure.11,13,14 Interestingly, with increasing irradiation times, a large band also appears around 470 nm (Figure 1f), which was neither observed before in the oxidized individual molecule, nor in the oxidized softer self-assemblies of the triarylamine tris-amide family.14 We attribute this peculiar signature to a Davydov splitting in the crystals.26 Indeed, because of a coherent alignment of the molecular dipoles, J-aggregates are formed and result in a splitting of the excited state energy levels with a red-shifted absorption transition. The crystals remained oxidized in solution for at least one month, demonstrating the stability of the radicals inside the supramolecular framework. Thin films made of the oxidized crystals display absorption bands at 0.8 eV, 2.1 eV, and 2.7 eV, that is an optical signature of delocalized polarons within the supramolecular structure (Figure 1g).27 Similar polaron formation was observed within softer fibers made of triarylamines,14 though the transition energies between the bands are here shifted down in energy due to the crystalline nature of the columns that allows for better structural ordering. DFT calculations performed on a stack of 10 triarylamines using the coordinates taken from the crystal structure show delocalization of the molecular orbitals due to the tight packing of the aromatic cores (Figure 2a and Figures S5,6). The electronic coupling between molecules along the stacking direction was determined to be 48.76 meV (393.3 cm-1) for a stacked dimer using the energy splitting approach.28 Further investigations of the charge transport properties revealed an electronic interaction of 618.95 meV (4992.17 cm-1) between the HOMO and SOMO of neutral and charged species inside the crystal. This leads to an effective transfer integral of 63.36 meV (511.03 cm-1), in line with typical values for high mobility TCNQ charge-transfer


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crystals.29 Overall, these results depict large electronic couplings in the crystal, comparable with the most efficient synthetic and natural systems displaying long-range energy transport.10,30 Further insights into the electronic behavior of the oxidized crystals were obtained by magnetic measurements, using electronic paramagnetic resonance (EPR) and a superconducting quantum interference device (SQUID) magnetometer (Quantum design S-VSM). Magnetic measurements were performed on a first sample which was oxidized by light irradiation, and then on a second sample which was further oxidized by exposure to iodine vapors. The oxidation levels were determined by quantitative EPR giving values of 5.8% and 39% respectively. The magnetic susceptibilities of the two samples versus temperature are plotted in Figure 2b. The values were corrected against a non-oxidized sample in order to remove diamagnetic contributions of the sample and the sample holder. Both samples display paramagnetic behavior and the data can be fitted according to the Curie-Weiss law superimposed with a temperature-independent paramagnetic (TIP) contribution that accounts for both Curie and Pauli paramagnetism within the crystals: 𝜒(𝑇) = 𝜒0 +

𝐶 𝑇−𝜃

where 𝜒0 is the temperature-independent paramagnetic contribution, C is the Curie constant

and 𝜃 is the Weiss temperature. Importantly, the presence of a temperature-independent

paramagnetic contribution (3.33 x 10-4 emu mol-1 and 4.1 x 10-4 emu mol-1 for light and iodine

oxidation respectively) implies Pauli paramagnetic behavior, due to delocalized metallic electrons. A similar magnetic behavior was previously observed with another type of triarylamine trisamide self-assembled in soft nanowires.14 A plot of the inverse magnetic susceptibility versus temperature displays a clear deviation from linear Curie behavior (Figure 2c) due to the presence of Pauli spins.31 This behavior was observed up to room temperature,


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implying the presence of metallic electrons within the oxidized crystals in all of the experiments performed in this study. A weak contribution due to antiferromagnetic interactions between radicals was evidenced by Weiss temperatures of -0.8 K and -1.0 K. The Curie constants were found to be 2.63 x 10-3 K emu mol-1 and 3.41 x 10-3 K emu mol-1 for the two samples (light and iodine oxidation, respectively). Additionally, magnetization versus magnetic field measurements were performed at 1.8 K (Figure 2d), and fitted using the Brillouin function (g = 2 and S = 1/2). The fit of the experimental data with a sole Curie behavior reveals that an oxidation level of only 1% would be needed for such behavior. Regarding the much higher level of oxidation measured, we conclude again that the majority of the radicals are found in a delocalized band structure, thus resulting in Pauli paramagnetism. Then, the effect of photo-doping on the conductivity was demonstrated by dropcasting the crystals over interdigitated gold electrodes with a 5 μm gap. Upon the application of a 10 mV potential across the electrodes, the oxidized crystals displayed high conductance, with a stable resistance around 500 Ω. In contrast, the unoxidized crystals displayed very low conductance, with a measured resistance above 100 MΩ. Between 10 mV and 5 V of applied voltage, the oxidized crystals displayed a linear I/V behavior (Figure 2e). Conversely, unoxidized crystals displayed three distinct regimes indicating charge-trap limited behavior. Finally, oxidized crystals displayed a perfectly linear response near 0 V when sweeping the voltage potential between -1 V and +1 V, indicating that the sum of contact resistance with the electrodes and intrinsic resistance within the crystal has an Ohmic resistive nature (Figure 2f). We finally turned to the study of the crystals as a potential optical waveguide. Birefringence of the needles was first observed under crossed polarizers, demonstrating a non-zero difference in the two refractive index planes and, as expected, a stacking direction parallel to the long axis of


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the crystal (Figure 3a-c). The crystals were thus tested for their ability to act as photonic waveguides along their main axis using a confocal microscope with incident lasers (532 nm or 785 nm) focused through a 100x objective. Upon beaming the laser at one tip of the crystals, one can clearly observe output at the distal end with both 532 nm and 785 nm lasers (Figure 3d,e). Optical waveguiding was observed in over 90% of the crystals having typical dimensions of 4-40 µm in length and 1-3 µm in width (Figure S7a), and regardless of whether they were oxidized or not. However, no waveguiding was observed when the laser was focused on top of the crystal, away from the tips (Figure 3f). Multiple waveguiding outputs were also routinely observed with crystals displaying defects (Figure 3g). In addition, we noticed that no fluorescence signal was observed from both the oxidized and unoxidized crystals (Figure 3h). From this combination of experiments, one can rule out a mechanism based on photoluminescence (which is responsible for all reported active organic waveguides to date) for at least three reasons: (1) The incident laser source is in a region where the unoxidized crystal does not absorb (532 nm and 785 nm); (2) We do not observe any fluorescence from either the oxidized or unoxidized crystals, and (3) We do not observe waveguiding behavior unless the crystal is illuminated at the tip (while a photoluminescent mechanism should result in waveguiding regardless of the laser position). To further elucidate the waveguiding mechanism, fluorescence bleaching experiments were performed by spin coating a layer of indocyanine dye (λabs = 775 nm; λem = 830 nm) on top of the crystals. These experiments were performed in a similar manner as the Bleach-Imaged Plasmon Propagation technique used to identify plasmon propagation in metallic waveguides and with an irradiation at 785 nm.32 Interestingly, with the dye on the top, the waveguiding effect was no longer observed with the unoxidized crystals (Figure 3i(i)), while the oxidized crystals continued to display the effect (Figure 3i(ii)). Oxidized and unoxidized crystals topped with the


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dye were also both irradiated at the tip with a laser for 10 minutes, and the fluorescence of the dye was then recorded at various coordinates on the crystal surface. At the point of laser irradiation, the fluorescence of the dye molecules is completely lost due to photobleaching during the 10 minutes laser irradiation. However, when moving along the crystal and away from the irradiation spot, we measured a gradual recovery of the fluorescence signal (Figure 3j). Importantly, we noticed a clear increase in the dye photobleaching distance along the oxidized crystal in comparison with the unoxidized one (Figure 3k). We attribute the photobleaching in the presence of the unoxidized crystals to scattering along the surface because we measured a similar propagation distance with the dye alone on a glass substrate (see control experiment in Figure S7e). On the other hand, for the oxidized crystals, the marked increase in the photobleaching effect is attributed to the evanescent near-field of the propagating energy inside the crystals. Comparison of the average distance at which 80% of the fluorescence signal is recovered in the two samples shows a 100% increase of the propagation length with the oxidized crystal (more than 2 μm). Overall, these experiments highlight the ability of the triarylamine single crystals to couple directly with the incident light and transfer the energy over micrometric distances. For the unoxidized crystals, the observations match a passive waveguiding mechanism.5 Indeed, upon addition of the dye, quenching of the passive waveguiding mechanism occurs for two reasons: (1) increase in the refractive index of the environment, resulting in a value similar to the one of the organic crystal (n = 1.5-2),33 and (2) coverage of the surface with a molecule which highly absorbs at the wavelength of the energy propagated, leading to large losses and retarded waveguiding propagation lengths. On the other hand, the oxidized crystals display an active waveguiding mechanism5 as first highlighted by the remaining waveguiding output with the dye


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on top of the crystal. In addition, the photobleaching effect ends before the end of the crystal even though we still observe light output at the distal end, indicating the existence of multimodal waveguiding where higher modes decay rapidly away from the excitation point, leaving the lower modes to propagate through the supramolecular columns. We have observed this effect on crystals as narrow as 750 nm (Figure S7d) thereby ruling out the possibility of multimodal passive waveguiding in the oxidized crystals. Taken as a whole, these experiments support an efficient energy transport due to the coherent polaronic band structure introduced in the crystal upon doping. The resultant metallic electrons within the crystals are able to couple to incident laser light and propagate the energy through a plasmonic mechanism. In conclusion, our experimental results demonstrate the formation of supramolecular organic materials displaying dual waveguiding mechanisms. The first mechanism is due to a passive waveguiding at the interface between the crystal and air. Upon oxidation, a second mechanism is activated over long distances (> 10 µm) and is plasmonic in nature, due to a coupling between the incident light and the delocalized metallic electrons within the structures, akin to what is commonly observed in metallic nanowires. This novel class of supramolecular nanomaterials34 may encompass other types of organic metals than those based on triarylamines, and such “organic plasmonic” waveguides represent an interesting opportunity to be implemented in optics, optoelectronics, and information technologies.


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a

c

b

(i) Φ=60°

1

d (ii) d1

e

f

d2

g

Figure 1. (a) Chemical structure of triarylamine tris-acetamide 1. (b) Crystal structure of 1 visualized along the direction of the columnar stacking for two layers of molecules and showing the intercolumnar cavities of 7.9 Å in diameter (methanol molecules were removed from the cavities for clarity (see SI)). (c) Stacking motif of two molecules 1, (i) along the column axis in the “snowflake” arrangement and (ii) from the side showing the characteristic N-N distance (d1) and ortho-carbon distance (d2). (d) Hirshfeld surface of 1 stacked in the crystal. (e) UV-Vis-NIR absorption spectra for various times of photo-oxidation. (f) Close-up of the band at 470nm compared with a reference consisting in an oxidized sample of another triarylamine tris-amide that pack in soft (non-crystalline) nanowires.14 (g) Experimental absorption bands of oxidized


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crystals in thin films and corresponding Gaussian fit for each peak revealing energy transitions at 0.80 eV, 2.17 eV, and 2.74 eV. a

b

c

5.8% of 1•+

39% of 1•+ 39% of 1•+ 5.8% of 1•+ HOMO-1

d

HOMO

LUMO 39% of 1•+

e

f

5.8% of 1•+

Figure 2. (a) DFT calculations on a column of 10 molecules (using the crystal structure coordinates) show extensive intermolecular delocalization of the HOMO-1, HOMO, and LUMO molecular orbitals. (b) Magnetic susceptibility versus temperature for a sample oxidized by light in a chloroform solution (5.8% of radicals 1•+) and for a sample oxidized by iodine vapors (39% of radicals 1•+). The data (black squares) are overlayed with a Curie-Weiss fit of the data with a temperature independent paramagnetic contribution (red line). (c) Inverse magnetic susceptibility versus temperature demonstrating deviation from linear Curie behavior (red line). (d) Magnetization versus magnetic field at 1.8K. The red lines correspond to the best fits of the data with a Brillouin function (g = 2 and S = ½). (e) Log-log I-V curve of oxidized and unoxidized crystals in the [10 mV / 10 V] range over interdigitated electrodes with a 5 μm gap. (f) I-V curve in the [-1 V / +1 V] range of oxidized and unoxidized crystals.


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A

aa

h

d

i

(ii)

1

(i) 0

e D f j

b

c

g

Ex

mo

k

1

0

Figure 3. (a) Birefringence of a population of single crystals under crossed polarizers (scale bar = 20 µm). (b-c) Single crystal observed under crossed polarizers before and after 45° rotation of the sample (scale bars = 10 μm). (d-e) Optical waveguiding for an incident 785 nm laser (d) and a 532 nm laser (e) focused at one end of a crystal (left orange arrow) and displaying an output at the distal end (right orange arrow) (scale bars = 4 μm). (f) Absence of waveguiding effect for a laser focused in the middle of the crystal (scale bar = 4 μm). (g) Reconstructed 3D image of light propagation along a single crystal and multiple outputs at defects (Ex = excitation, mo = multiple outputs). (h) Fluorescence spectrum from an oxidized crystal excited with a 785nm laser focused through a 100x objective with a confocal microscope. (i) Reconstructed 3D images of light propagation in (i) a non-oxidized crystal covered with indocyanine dye and (ii) in an oxidized crystal covered with the same dye (crystal lengths of approximately 6 μm). (j) Fluorescence spectra taken on the dye-covered oxidized crystal after the waveguiding experiment. Photobleaching is observed close to the laser spot, with a slow recovery of the fluorescence as the measurements are taken further down the crystal (and indicated by the direction of the arrow). (k) Comparative photobleaching of dye-covered unoxidized and oxidized crystals showing an increased photobleaching distance with the oxidized crystals due to coherent energy


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transfer mechanism along the oxidized crystals (data taken from 8 crystals for each situation oxidized / non-oxidized). ASSOCIATED CONTENT CCDC 1442800 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Supporting Information. Synthetic procedures for 1, general procedures for UV-Vis-NIR, EPR, SQUID and waveguiding experiments, general procedure for conductivity measurements, crystal structure determination, DFT calculations and supplementary waveguiding characterization. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *[email protected] Notes The authors declare no competing financial interests. ACKNOWLEDGMENT The research leading to these results has received funding from the European Research Council under the European Community's Seventh Framework Program (FP7/2007-2013) / ERC Starting Grant agreement n°257099 (N.G.). We thank the Centre National de la Recherche Scientifique (CNRS), the COST action (CM 1304), the international center for Frontier Research


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in Chemistry (icFRC), the Laboratory of Excellence for Complex System Chemistry (LabEx CSC), the Laboratory of Excellence for Nanostructures in Interactions with Environments (LabEx NIE), the University of Strasbourg (UNISTRA), and the Institut Universitaire de France (IUF). REFERENCES (1) Barnes, W. L.; Dereux, A.; Ebbesen, T. W. Nature 2003, 424, 824. (2) Focus issue on plasmonic applications: Nat. Nanotechnol. 2015, 10, 1. (3) Atwater, H. A.; Polman, A. Nat. Mater. 2010, 9, 205. (4) Engheta, N. Science 2007, 317, 1698. (5) Lal, S.; Hafner, J. H.; Halas, N. J.; Link, S.; Nordlander, P. Acc. Chem. Res. 2012, 45, 1887. (6) Yan, Y.; Zhao, Y. S. Chem. Soc. Rev. 2014, 43, 4325. (7) Chandrasekar, R. Phys. Chem. Chem. Phys. 2014, 16, 7173. (8) Yao, W.; Zhao, Y. S. Nanoscale 2014, 6, 3467. (9) Clark, K. A.; Krueger, E. L.; Vanden Bout, D. A. J. Phys. Chem. Lett. 2014, 5, 2274. (10) Haedler, A. T.; Kreger, K.; Issac, A.; Wittmann, B.; Kivala, M.; Hammer, N.; Köhler, J.; Schmidt, H.-W.; Hildner, R. Nature 2015, 523, 196. (11) Moulin, E.; Niess, F.; Maaloum, M.; Buhler, E.; Nyrkova, I.; Giuseppone, N. Angew. Chem. Int. Ed. 2010, 49, 6974.


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(12) Jouault, N.; Moulin, E.; Giuseppone, N.; Buhler, E. Phys. Rev. Lett. 2015, 115, 085501. (13) Nyrkova, I.; Moulin, E.; Armao, J. J.; Maaloum, M.; Heinrich, B.; Rawiso, M.; Niess, F.; Cid, J.-J.; Jouault, N.; Buhler, E.; Semenov, A. N.; Giuseppone, N. ACS Nano 2014, 8, 10111. (14) Armao, J. J.; Maaloum, M.; Ellis, T.; Fuks, G.; Rawiso, M.; Moulin, E.; Giuseppone, N. J. Am. Chem. Soc. 2014, 136, 11382. (15) Wolf, A.; Moulin, E.; Cid Martín, J. J.; Goujon, A.; Du, G.; Busseron, E.; Fuks, G.; Giuseppone, N. Chem. Commun. 2015, 51, 4212. (16) Domoto, Y.; Busseron, E.; Maaloum, M.; Moulin, E.; Giuseppone, N. Chem. Eur. J. 2015, 21, 1938. (17) Moulin, E.; Niess, F.; Fuks, G.; Jouault, N.; Buhler, E.; Giuseppone, N. Nanoscale 2012, 4, 6748. (18) Busseron, E.; Cid, J.-J.; Wolf, A.; Du, G.; Moulin, E.; Fuks, G.; Maaloum, M.; Polavarapu, P.; Ruff, A.; Saur, A.-K.; Ludwigs, S.; Giuseppone, N. ACS Nano 2015, 9, 2760. (19) Licsandru, E.-D.; Schneider, S.; Tingry, S.; Ellis, T.; Moulin, E.; Maaloum, M.; Lehn, J.M.; Barboiu, M.; Giuseppone, N. Nanoscale 2016, 8, DOI: 10.1039/C5NR06977G. (20) Faramarzi, V.; Niess, F.; Moulin, E.; Maaloum, M.; Dayen, J.-F.; Beaufrand, J.-B.; Zanettini, S.; Doudin, B.; Giuseppone, N. Nat. Chem. 2012, 4, 485. (21) Moulin, E.; Cid, J. J.; Giuseppone, N. Adv. Mat. 2013, 25, 477. (22) Armao, J. J.; Domoto, Y.; Umehara, T.; Maaloum, M.; Contal, C.; Fuks, G.; Moulin, E.; Decher, G.; Javahiraly, N.; Giuseppone, N. ACS Nano 2016, 10, 2082.


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(23) Desiraju, G. R. J. Am. Chem. Soc. 2013, 135, 9952. (24) Mukherjee, A. Cryst. Growth Des. 2015, 15, 3076. (25) Spackman, M. A.; Jayatilaka, D. CrystEngComm 2009, 11, 19. (26) Würthner, F.; Kaiser, T. E.; Saha-Möller, C. R. Angew. Chem. Int. Ed. 2011, 50, 3376. (27) Beljonne, D.; Cornil, J.; Sirringhaus, H.; Brown, P. J.; Shkunov, M.; Friend, R. H.; Brédas, J.-L. Adv. Funct. Mater. 2001, 11, 229. (28) Zhu, L.; Yi, Y.; Li, Y.; Kim, E.-G.; Coropceanu, V.; Brédas, J.-L. J. Am. Chem. Soc. 2012, 134, 2340. (29) Zhu, L.; Yi, Y.; Fonari, A.; Corbin, N. S.; Coropceanu, V.; Brédas, J.-L. J. Phys. Chem. C 2014, 118, 14150. (30) Cogdell, R. J.; Gall, A.; Köhler, J. Q. Rev. Biophys. 2006, 39, 227. (31) Krinichnyi, V. I.; Konkin, A. L.; Monkman, A. P. Synth. Met. 2012, 162, 1147. (32) Solis, D.; Chang, W.-S.; Khanal, B. P.; Bao, K.; Nordlander, P.; Zubarev, E. R.; Link, S. Nano Lett. 2010, 10, 3482. (33) Passive waveguiding is dependent upon the refractive index of the material being larger than the refractive index of the surroundings to take advantage of total internal reflection at the interface, see: Zhang, C.; Zhao, Y. S.; Yao, J. Phys. Chem. Chem. Phys. 2011, 13, 9060. (34) Busseron E., Ruff, Y., Moulin, E., Giuseppone, N. Nanoscale 2013, 5, 7098.


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Long-Range Energy Transport via Plasmonic Propagation in a

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