Nanoscale plasmonic phase sensor

Wackenhut, Frank; Jakob, Lukas A.; Hauler, Otto; Stuhl, Alexander; Laible, Florian; Fleischer, Monika; Braun, Kai; Meixner, Alfred J.

doi:10.1007/s00216-019-02340-w

Cited by 4 publications

(6 citation statements)

References 39 publications

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“…Interferometric scattering microscopy (iSCAT) − is a simple bright-field imaging technique that records the interference (Re[ E scat * E refl ] = | E scat || E refl | cos Δϕ) between a scattered field ( E scat ) from a NP and a field reflected from the interface between the substrate and medium (water or air) ( E refl ). The phase difference (Δϕ = ϕ scat + Φ Gouy + ϕ refl ) includes the scattering phase shift of the NP relative to the incident field (ϕ scat ), , as well as the phase shift induced by the substrate reflection (ϕ refl ), and the Gouy phase shift − (Φ Gouy ). The technique, which has far greater sensitivity than DFS, − , has been used successfully for NP tracking, ,,,, label-free single-biomolecule detection, − and molecular mass analysis. ,,,, However, iSCAT does not provide a separate amplitude (| E scat |) and intrinsic phase (ϕ scat ) of E scat , making it difficult to extract the quantitative spectroscopic information on the optical scattering of a single NP.…”

Section: Introductionmentioning

confidence: 99%

Amplitude and Phase Spectra of Light Scattered from a Single Nanoparticle

et al. 2022

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Interferometric scattering microscopy (iSCAT), the imaging of interference between scattered light from a nanoparticle and reflected light from a substrate, provides a sensitivity sufficient for single biomolecule detection. The imaged interference, however, does not provide a separate amplitude and phase of the scattered light, making quantitative or spectroscopic measurement difficult. We report a method to fully recover the scattering amplitude and phase from iSCAT: vertical (z) scanning of the objective lens across the focus adds a Gouy phase between scattered light and reflected light, modulating image contrasts. The zstack image analysis provides a highly accurate amplitude and phase of the scattered light. The method is validated by demonstrating that the recovered amplitude and phase spectra of a single gold nanoparticle reproduce well-known plasmon resonances. We also show that the phase spectra can be used to extract the damping parameter of the plasmon resonance and the coupling strength of the strongly coupled chromophore-nanoparticle assembly.

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Section: Introductionmentioning

confidence: 99%

Amplitude and Phase Spectra of Light Scattered from a Single Nanoparticle

et al. 2022

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“…Nevertheless, there are a few techniques to directly measure the phase, for example, by scanning near field microscopy, , quadriwave lateral shearing interferometry with a white light source, , or using a Mirau interferometer . In previous publications, , we presented another experimental approach to directly measure the phase of the light scattered by a single NP, which is based on the combination of a confocal microscope and a Michelson interferometer. We have already demonstrated that this approach is suitable for detecting the phase shift caused by a single NP and can even be applied to sense refractive index changes and binding of molecules to the surface. , …”

Section: Introductionmentioning

confidence: 99%

“…In previous publications, , we presented another experimental approach to directly measure the phase of the light scattered by a single NP, which is based on the combination of a confocal microscope and a Michelson interferometer. We have already demonstrated that this approach is suitable for detecting the phase shift caused by a single NP and can even be applied to sense refractive index changes and binding of molecules to the surface. , …”

Section: Introductionmentioning

confidence: 99%

“…We have already demonstrated that this approach is suitable for detecting the phase shift caused by a single NP and can even be applied to sense refractive index changes and binding of molecules to the surface. 77,78 ■ METHODS Experimental Setup. Optical measurements were performed with a home-built inverted confocal microscope with an additional interference beam path, as schematically shown in Figure 1a.…”

Section: ■ Introductionmentioning

confidence: 99%

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Sensitive Interferometric Plasmon Ruler Based on a Single Nanodimer

et al. 2021

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The plasmon ruler has drawn substantial attention for measuring small separations between two plasmonic nanoparticles (NPs), which can be as sensitive as to observe the bending of DNA. Usually, the plasmon ruler is based on the spectral shift of the localized surface plasmon resonance (LSPR) caused by the distance-dependent dipole−dipole coupling between two plasmonic NPs. Here, we present an approach to the plasmon ruler by detecting the phase of the scattered light. We have developed a combination of a confocal microscope and a Michelson interferometer, which allows us to measure the phase change caused by a single nanoparticle in a diffraction-limited focal volume. The plasmon ruler is realized by a gold nanoparticle dimer (GND) deposited on a flexible polydimethylsiloxane substrate, where the same GND can be investigated with variable gaps by applying strain by stretching of the substrate. In this experimental configuration, the GND is located at a low reflecting interface leading to a large phase difference of more than 100°relative to the substrate, which allows us to easily detect a single GND. Interestingly, an increase of the gap by 11 nm leads to a large phase shift of 94°, even though there is only a 11 nm spectral shift of the LSPR. We find that both the spectral and phase shifts have the same r −3 dependence on the particle gap, which is expected for pure dipole−dipole coupling.

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“…Recently, a nanopore sequencer using protein nanopores has been achieved to sequence a single-molecule base without DNA synthesis or amplification [6]. Furthermore, plasmonic properties of nanoparticles can be used either for information about the interaction of single molecules on these nanoparticles with ligands [7] or allow surface-enhanced Raman spectroscopy [8]. For the characterization of processes in cells, nanoelectrochemistry can also be used, e.g., nanoresolved SECM (scanning electrochemical microscopy).…”

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confidence: 99%

ABC Spotlight on single-molecule detection

Gauglitz

2020

Anal Bioanal Chem

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Nanoscale plasmonic phase sensor

Cited by 4 publications

References 39 publications

Amplitude and Phase Spectra of Light Scattered from a Single Nanoparticle

Amplitude and Phase Spectra of Light Scattered from a Single Nanoparticle

Sensitive Interferometric Plasmon Ruler Based on a Single Nanodimer

ABC Spotlight on single-molecule detection

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