Probing a Century Old Prediction One Plasmonic Particle at a Time

Tcherniak, Alexei; Ha, Ji Won; Domínguez-Medina, Sergio; Slaughter, Liane Siu

doi:10.1021/nl100199h

Cited by 159 publications

(199 citation statements)

References 55 publications

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“…We give here a discussion of the different, tightly interrelated factors that all contribute to the trend observed in , where V is the NP volume. 68,70,72 These scattered fields result in further constructive and destructive interference for different plasmon modes. 49,52,68 Finally, in addition to the general increase in plasmon coupling for smaller interparticle distances, higher order plasmon modes of the individual NPs gain strength and couple with higher order and dipole modes of the neighboring NPs.…”

Section: Resultsmentioning

confidence: 99%

Plasmonic polymers unraveled through single particle spectroscopy

et al. 2014

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Plasmonic polymers are quasi one-dimensional assemblies of nanoparticles whose optical responses are governed by near-field coupling of localized surface plasmons. Through single particle extinction spectroscopy correlated with electron microscopy, we reveal the effect of the composition of the repeat unit, the chain length, and extent of disorder on the energies, intensities, and line shapes of the collective resonances of individual plasmonic polymers constructed from three different sizes of gold nanoparticles. Our combined experiment and theoretical analysis focuses on the superradiant plasmon mode, which results from the most attractive interactions along the nanoparticle chain and yields the lowest energy resonance in the spectrum. This superradiant mode redshifts with increasing chain length until an infinite chain limit, where additional increases in chain length cause negligible change in the energy of the superradiant mode. We find that, among plasmonic polymers of equal width comprising nanoparticles with different sizes, the onset of the infinite chain limit and its associated energy are dictated by the number of repeat units and not the overall length, of the polymer. The intensities and linewidths of the superradiant mode relative to higher energy resonances, however, differ as the size and number of nanoparticles are varied in the plasmonic polymers studied here. These findings provide general guidelines for engineering the energies, intensities, and line shapes of the collective optical response of plasmonic polymers constructed from nanoparticles with sizes ranging from a few tens to one hundred nanometers.

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Section: Resultsmentioning

confidence: 99%

Plasmonic polymers unraveled through single particle spectroscopy

et al. 2014

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“…3b and S1). 49 Fig . 3c shows the measured absorption and scattering spectra, which are in excellent agreement with Mie theory calculations.…”

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“…3d), indicative of local heterogeneities in the nanoparticle shape and its nanoenvironment as well as substrate effects. 49 The nanoparticle in Fig. 3d is an example of a nanoparticle for which Mie theory cannot match the absorption and scattering spectra.…”

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Single-Particle Absorption Spectroscopy by Photothermal Contrast

et al. 2015

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Removing effects of sample heterogeneity through single-molecule and single-particle techniques has advanced many fields. While background free luminescence and scattering spectroscopy is widely used, recording the absorption spectrum only is rather difficult. Here we present an approach capable of recording pure absorption spectra of individual nanostructures. We demonstrate the implementation of single-particle absorption spectroscopy on strongly scattering plasmonic nanoparticles by combining photothermal microscopy with a supercontinuum laser and an innovative calibration procedure that accounts for chromatic aberrations and wavelength-dependent excitation powers. Comparison of the absorption spectra to the scattering spectra of the same individual gold nanoparticles reveals the blueshift of the absorption spectra, as predicted by Mie theory but previously not detectable in extinction measurements that measure the sum of absorption and scattering. By covering a wavelength range of 300 nm, we are furthermore able to record absorption spectra of single gold nanorods with different aspect ratios. We find that the spectral shift between absorption and scattering for the longitudinal plasmon resonance decreases as a function of nanorod aspect ratio, which is in agreement with simulations.

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“…Therefore, measuring both absorption (σ ABS ) and scattering cross-sections (σ SCA ) for coupled SPs in closely spaced NP assemblies is necessary to understand the interplay between electromagentic field enhancement and ohmic loss. While SP absorption of a single NP has been measured by photothermal heterodyne imaging (34)(35)(36)(37), absorption of redshifted coupled SPs has not been explored in detail.…”

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Low absorption losses of strongly coupled surface plasmons in nanoparticle assemblies

Chang¹,

Willingham²,

Slaughter³

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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Coupled surface plasmons in one-dimensional assemblies of metal nanoparticles have attracted significant attention because strong interparticle interactions lead to large electromagnetic field enhancements that can be exploited for localizing and amplifying electromagnetic radiation in nanoscale structures. Ohmic loss (i.e., absorption by the metal), however, limits the performance of any application due to nonradiative surface plasmon relaxation. While absorption losses have been studied theoretically, they have not been quantified experimentally for strongly coupled surface plasmons. Here, we report on the ohmic loss in one-dimensional assemblies of gold nanoparticles with small interparticle separations of only a few nanometers and hence strong plasmon coupling. Both the absorption and scattering cross-sections of coupled surface plasmons were determined and compared to electrodynamic simulations. A lower absorption and higher scattering cross-section for coupled surface plasmons compared to surface plasmons of isolated nanoparticles suggest that coupled surface plasmons suffer smaller ohmic losses and therefore act as better antennas. These experimental results provide important insight for the design of plasmonic devices.nanoparticle self-assembly | photothermal heterodyne imaging | surface plasmon resonance | single particle spectroscopy | dark-field imaging P lasmonic antennas can convert optical radiation into intense local field distributions or enable coupling to guided modes that are confined to subwavelength dimensions (1-4). Strong surface plasmon (SP) coupling between neighboring nanoparticles (NPs) also leads to large enhancements of electromagnetic fields, which benefit various applications such as waveguides (5, 6), nano-antennas (7-9), field enhanced spectroscopies (10-12), and biological sensors (4,13,14). The interparticle coupling resulting from near-field interactions between closely spaced NPs is inversely proportional to d 3 where d is the distance between the NPs (6). The largest local field enhancements are indeed found for the smallest interparticle distances (11,15). Extremely small interparticle gaps of a few nanometers can be achieved in selfassembled nanostructures (16-19), opening up new paths for the design of plasmonic devices. With bottom-up assembly, precise periodic positioning of the NPs is more difficult and hence structures with a distribution of NP gaps are created. However, high throughput patterning for large area fabrication at reduced costs make NP assemblies attractive alternatives to structures made by conventional top-down approaches (20). For the system studied here, SI Appendix, Fig. S1 shows an example of a periodic array of rings assembled from a chloroform solution of 40 nm gold NPs. In addition, the recent use of correlated electron and optical microscopy on individual NP assemblies is making it possible to decipher the effects of local NP ordering and symmetry breaking on the collective optical response (21).Independent of the plasmonic nanostructure, absorp...

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Probing a Century Old Prediction One Plasmonic Particle at a Time

Cited by 159 publications

References 55 publications

Plasmonic polymers unraveled through single particle spectroscopy

Plasmonic polymers unraveled through single particle spectroscopy

Single-Particle Absorption Spectroscopy by Photothermal Contrast

Low absorption losses of strongly coupled surface plasmons in nanoparticle assemblies

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