Plasmon Near-Field Coupling in Metal Dimers as a Step toward Single-Molecule Sensing

Aćimović, Srdjan S.; Kreuzer, Mark P.; González, María Ujué; Quidant, Romain

doi:10.1021/nn900102j

Cited by 350 publications

(255 citation statements)

References 34 publications

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“…The dimer structures attracted particular interest 25,49,50 because of the extremely strong enhancement of the electromagnetic field at the nanogap position. Each dimer consists of two diagonally aligned gold nanoblocks with dimensions of approximately 100 nm3100 nm3 40 nm and a gap size of 30 nm (an SEM image of a typical dimer can be seen in the inset of Figure 4a).…”

Section: Resultsmentioning

confidence: 99%

Direct imaging of the near field and dynamics of surface plasmon resonance on gold nanostructures using photoemission electron microscopy

et al. 2013

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Localized surface plasmon resonance (LSPR) can be supported by metallic nanoparticles and engineered nanostructures. An understanding of the spatially resolved near-field properties and dynamics of LSPR is important, but remains experimentally challenging. We report experimental studies toward this aim using photoemission electron microscopy (PEEM) with high spatial resolution of sub-10 nm. Various engineered gold nanostructure arrays (such as rods, nanodisk-like particles and dimers) are investigated via PEEM using near-infrared (NIR) femtosecond laser pulses as the excitation source. When the LSPR wavelengths overlap the spectrum of the femtosecond pulses, the LSPR is efficiently excited and promotes multiphoton photoemission, which is correlated with the local intensity of the metallic nanoparticles in the near field. Thus, the local field distribution of the LSPR on different Au nanostructures can be directly explored and discussed using the PEEM images. In addition, the dynamics of the LSPR is studied by combining interferometric time-resolved pump-probe technique and PEEM. Detailed information on the oscillation and dephasing of the LSPR field can be obtained. The results identify PEEM as a powerful tool for accessing the near-field mapping and dynamic properties of plasmonic nanostructures. Keywords: femtosecond laser; local field enhancement; near-field imaging; photoemission electron microscopy; surface plasmon resonance INTRODUCTION Because of the rapid development of nanofabrication techniques, metallic nanostructures that can exhibit localized surface plasmon resonance (LSPR) can be fabricated using several methods. The resonance frequency and amplitude of LSPR on metallic nanostructures are known to depend on the metal materials, shapes, and surrounding media. [1][2][3][4] In addition, the LSPR can confine optical fields in nanoscale space, leading to the so-called local field enhancement effect. These unique properties promote the application of LSPR in many fields, such as surface-enhanced Raman scattering, 5-8 sensing, 1,9,10 plasmonassisted photochemical reactions 4,11,12 and photocurrent generation. [13][14][15] To further understand the LSPR mechanism and to optimize the design of the plasmonic nanostructures for most applications, the near-field properties of the LSPR fields (especially the near-field distribution of the plasmonic nanostructures) must be determined. To date, investigations of the optical properties of LSPR have largely relied on far-field spectroscopic techniques or numerical simulations. Several experimental approaches have been utilized to visualize the near field, including scanning photoionization microscopy, 16,17 scanning near-field optical microscopy, 18-21 nonlinear luminescence or fluorescent microscopy, 22,23 nonlinear photopolymerization 24,25 and near-field ablation of a substrate. [26][27][28][29] However, these approaches have

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Section: Resultsmentioning

confidence: 99%

Direct imaging of the near field and dynamics of surface plasmon resonance on gold nanostructures using photoemission electron microscopy

et al. 2013

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“…By doing so, we are able to relate the results of the optical response from different approximations and predict the influence of nonlocality in the limit of subnanometric distances where nonlocal effects are pronounced. In elucidating the major physics behind the nonlocal response in plasmonic nanoparticle dimer, we find a robust plasmon ruler [18][19][20][21][22] that unambiguously determines the spectral position of surface plasmon resonances in strongly coupled systems forming subnanometric plasmonic cavities.To implement the TDDFT calculations, a cylindrical jellium model is adopted to describe the electronic structure of the infinite metallic nanowire. This model captures the collective plasmonic modes of conduction electrons and is perfectly suited to address nonlocal effects derived from the interactions between these electrons, such as the dynamical screening of the external field [1,4,5] and tunneling [23][24][25][26][27] as discussed below.…”

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confidence: 95%

Robust Subnanometric Plasmon Ruler by Rescaling of the Nonlocal Optical Response

et al. 2013

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We present the optical response of two interacting metallic nanowires calculated for separation distances down to angstrom range. State-of-the-art local and nonlocal approaches are compared with full quantum time-dependent density functional theory calculations that give an exact account of nonlocal and tunneling effects. We find that the quantum results are equivalent to those from classical approaches when the nanoparticle separation is defined as the separation between centroids of the screening charges. This establishes a universal plasmon ruler for subnanometric distances. Such a ruler not only impacts the basis of many applications of plasmonics, but also provides a robust rule for subnanometric metrology. DOI: 10.1103/PhysRevLett.110.263901 PACS numbers: 42.25.Bs, 36.40.Gk, 73.20.Mf, 78.67.Bf The exact calculation of the optical response of a nanosystems is a challenging task. In metallic nanostructures the complex nonlocal interactions between conduction electrons modify the standard local classical response, typically characterized by the presence of surface plasmon resonances [1]. This effect is more pronounced in small particles and in strongly coupled systems where the nonlocal nature of electronic interactions is emphasized. To establish an exact and accurate model to describe the spectral features of plasmonic resonances in such systems is thus of paramount importance from both fundamental and practical points of view [2,3]. A variety of theoretical approaches that incorporate different levels of sophistication have been adopted to address the optical response, but certain lack of unification still persists. In particular, the community of surface physics has elaborated accurate nonlocal treatments to address the surface response of conduction electrons of metal surfaces and small metallic objects [1,[4][5][6][7][8][9], whereas the community of nano-optics has focused on developing practical local and nonlocal treatments where the emphasis is placed on the geometrical aspects of the metal boundaries rather than on the actual response of the electrons [2,3,[10][11][12][13][14][15][16]. This Letter bridges both fields, providing a unified and practical picture of the optical response in coupled metallic nanoparticles located at subnanometric proximity.We calculate the optical response of two interacting metallic nanowires in vacuum using a full quantum timedependent density functional theory (TDDFT) approach [17] as well as using macroscopic theory based on solution of classical Maxwell equations with local and nonlocal descriptions of the system. The comparison between quantum and classical results on coupled nanowires provides a perfect basis to unravel the limitations, tendencies, and physics of the optical response under different levels of approximation. By doing so, we are able to relate the results of the optical response from different approximations and predict the influence of nonlocality in the limit of subnanometric distances where nonlocal effects are pronounced. In elucidating the m...

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“…At the local scale, this results in the presence of strong evanescent fields localized near the particles. This strong localization of light can be used for surface-enhanced Raman scattering and surface enhanced fluorescence at the single molecule level, [5][6][7][8] but also for developing plasmon resonance sensors [9][10][11] and for performing near-field nanolithography. 12,13 For all these applications, the knowledge of the field distribution on the structures is important.…”

Section: Introductionmentioning

confidence: 99%

Strong near-field optical localization on an array of gold nanodisks

Aigouy

Prieto

Vitrey

et al. 2011

Journal of Applied Physics

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By scanning near-field optical microscopy, we measured the localization of the electromagnetic field on an array of gold nanodisks illuminated in a transmission mode. We experimentally observed that the field is localized between the disks, with a pattern oriented along the incident polarization direction. We also observed that the electromagnetic field rapidly decays above the nanodisks, showing a strong vertical localization. The experimental results are in good agreement with numerical simulations performed by a finite difference time domain method. This study provides quantitative information about the local optical properties of closely-packed nanodisks that can be used for applications in biochemical sensors and nanolithography.

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Plasmon Near-Field Coupling in Metal Dimers as a Step toward Single-Molecule Sensing

Cited by 350 publications

References 34 publications

Direct imaging of the near field and dynamics of surface plasmon resonance on gold nanostructures using photoemission electron microscopy

Direct imaging of the near field and dynamics of surface plasmon resonance on gold nanostructures using photoemission electron microscopy

Robust Subnanometric Plasmon Ruler by Rescaling of the Nonlocal Optical Response

Strong near-field optical localization on an array of gold nanodisks

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