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Huang J, Hu S, Kos D, Xiong Y, Jakob LA, Sánchez-Iglesias A, Guo C, Liz-Marzán LM, Baumberg JJ. Enhanced Photocurrent and Electrically Pumped Quantum Dot Emission from Single Plasmonic Nanoantennas. ACS Nano 2024; 18:3323-3330. [PMID: 38215048 PMCID: PMC10832344 DOI: 10.1021/acsnano.3c10092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/22/2023] [Accepted: 01/08/2024] [Indexed: 01/14/2024]
Abstract
Integrating cavity-enhanced colloidal quantum dots (QDs) into photonic chip devices would be transformative for advancing room-temperature optoelectronic and quantum photonic technologies. However, issues with efficiency, stability, and cost remain formidable challenges to reach the single antenna limit. Here, we present a bottom-up approach that delivers single QD-plasmonic nanoantennas with electrical addressability. These QD nanojunctions exhibit robust photoresponse characteristics, with plasmonically enhanced photocurrent spectra matching the QD solution absorption. We demonstrate electroluminescence from individual plasmonic nanoantennas, extending the device lifetime beyond 40 min by utilizing a 3 nm electron-blocking polymer layer. In addition, we reveal a giant voltage-dependent redshift of up to 62 meV due to the quantum-confined Stark effect and determine the exciton polarizability of the CdSe QD monolayer to be 4 × 10-5 meV/(kV/cm)2. These developments provide a foundation for accessing scalable quantum light sources and high-speed, tunable optoelectronic systems operating under ambient conditions.
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Affiliation(s)
- Junyang Huang
- NanoPhotonics
Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, U.K.
| | - Shu Hu
- NanoPhotonics
Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, U.K.
| | - Dean Kos
- NanoPhotonics
Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, U.K.
| | - Yuling Xiong
- NanoPhotonics
Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, U.K.
| | - Lukas A. Jakob
- NanoPhotonics
Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, U.K.
| | - Ana Sánchez-Iglesias
- CIC
biomaGUNE, Basque Research and Technology Alliance (BRTA), Paseo de Miramón 194, Donostia-San Sebastián 20014, Spain
| | - Chenyang Guo
- NanoPhotonics
Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, U.K.
| | - Luis M. Liz-Marzán
- CIC
biomaGUNE, Basque Research and Technology Alliance (BRTA), Paseo de Miramón 194, Donostia-San Sebastián 20014, Spain
- Ikerbasque,
Basque Foundation for Science, Bilbao 43009, Spain
| | - Jeremy J. Baumberg
- NanoPhotonics
Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, U.K.
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Mueller NS, Arul R, Kang G, Saunders AP, Johnson AC, Sánchez-Iglesias A, Hu S, Jakob LA, Bar-David J, de Nijs B, Liz-Marzán LM, Liu F, Baumberg JJ. Photoluminescence upconversion in monolayer WSe 2 activated by plasmonic cavities through resonant excitation of dark excitons. Nat Commun 2023; 14:5726. [PMID: 37714855 PMCID: PMC10504321 DOI: 10.1038/s41467-023-41401-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 09/04/2023] [Indexed: 09/17/2023] Open
Abstract
Anti-Stokes photoluminescence (PL) is light emission at a higher photon energy than the excitation, with applications in optical cooling, bioimaging, lasing, and quantum optics. Here, we show how plasmonic nano-cavities activate anti-Stokes PL in WSe2 monolayers through resonant excitation of a dark exciton at room temperature. The optical near-fields of the plasmonic cavities excite the out-of-plane transition dipole of the dark exciton, leading to light emission from the bright exciton at higher energy. Through statistical measurements on hundreds of plasmonic cavities, we show that coupling to the dark exciton leads to a near hundred-fold enhancement of the upconverted PL intensity. This is further corroborated by experiments in which the laser excitation wavelength is tuned across the dark exciton. We show that a precise nanoparticle geometry is key for a consistent enhancement, with decahedral nanoparticle shapes providing an efficient PL upconversion. Finally, we demonstrate a selective and reversible switching of the upconverted PL via electrochemical gating. Our work introduces the dark exciton as an excitation channel for anti-Stokes PL in WSe2 and paves the way for large-area substrates providing nanoscale optical cooling, anti-Stokes lasing, and radiative engineering of excitons.
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Affiliation(s)
- Niclas S Mueller
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK.
- Fritz Haber Institute of the Max Planck Society, 14195, Berlin, Germany.
| | - Rakesh Arul
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Gyeongwon Kang
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
- Department of Chemistry, Kangwon National University, Chuncheon, 24341, South Korea
| | - Ashley P Saunders
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
| | - Amalya C Johnson
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, 94305, USA
| | - Ana Sánchez-Iglesias
- CIC biomaGUNE, Basque Research and Technology Alliance (BRTA), Paseo de Miramón 194, Donostia-San Sebastián, 20014, Spain
- Centro de Física de Materiales, CSIC-UPV/EHU, Manuel Lardizabal Ibilbidea 5, Donostia-San Sebastián, 20018, Spain
| | - Shu Hu
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Lukas A Jakob
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Jonathan Bar-David
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Bart de Nijs
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Luis M Liz-Marzán
- CIC biomaGUNE, Basque Research and Technology Alliance (BRTA), Paseo de Miramón 194, Donostia-San Sebastián, 20014, Spain
- Ikerbasque, Basque Foundation for Science, Bilbao, 48009, Spain
- Centro de Investigación Biomédica en Red, Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Donostia-San Sebastián, 20014, Spain
| | - Fang Liu
- Department of Chemistry, Stanford University, Stanford, CA, 94305, USA
| | - Jeremy J Baumberg
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge, CB3 0HE, UK.
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Jakob LA, Deacon WM, Zhang Y, de Nijs B, Pavlenko E, Hu S, Carnegie C, Neuman T, Esteban R, Aizpurua J, Baumberg JJ. Giant optomechanical spring effect in plasmonic nano- and picocavities probed by surface-enhanced Raman scattering. Nat Commun 2023; 14:3291. [PMID: 37280203 DOI: 10.1038/s41467-023-38124-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 04/17/2023] [Indexed: 06/08/2023] Open
Abstract
Molecular vibrations couple to visible light only weakly, have small mutual interactions, and hence are often ignored for non-linear optics. Here we show the extreme confinement provided by plasmonic nano- and pico-cavities can sufficiently enhance optomechanical coupling so that intense laser illumination drastically softens the molecular bonds. This optomechanical pumping regime produces strong distortions of the Raman vibrational spectrum related to giant vibrational frequency shifts from an optical spring effect which is hundred-fold larger than in traditional cavities. The theoretical simulations accounting for the multimodal nanocavity response and near-field-induced collective phonon interactions are consistent with the experimentally-observed non-linear behavior exhibited in the Raman spectra of nanoparticle-on-mirror constructs illuminated by ultrafast laser pulses. Further, we show indications that plasmonic picocavities allow us to access the optical spring effect in single molecules with continuous illumination. Driving the collective phonon in the nanocavity paves the way to control reversible bond softening, as well as irreversible chemistry.
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Affiliation(s)
- Lukas A Jakob
- Nanophotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - William M Deacon
- Nanophotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Yuan Zhang
- Henan Key Laboratory of Diamond Optoelectronic Materials and Devices, Key Laboratory of Material Physics, Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou, 450052, China.
| | - Bart de Nijs
- Nanophotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Elena Pavlenko
- Nanophotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Shu Hu
- Nanophotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Cloudy Carnegie
- Nanophotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Tomas Neuman
- Center for Material Physics (CSIC-UPV/EHU and DIPC), Paseo Manuel de Lardizabal 5, Donostia-San Sebastian Gipuzkoa, 20018, Spain
| | - Ruben Esteban
- Center for Material Physics (CSIC-UPV/EHU and DIPC), Paseo Manuel de Lardizabal 5, Donostia-San Sebastian Gipuzkoa, 20018, Spain
| | - Javier Aizpurua
- Center for Material Physics (CSIC-UPV/EHU and DIPC), Paseo Manuel de Lardizabal 5, Donostia-San Sebastian Gipuzkoa, 20018, Spain.
| | - Jeremy J Baumberg
- Nanophotonics Centre, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE, UK.
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Mueller N, Arul R, Jakob LA, Blunt MO, Földes T, Rosta E, Baumberg JJ. Collective Mid-Infrared Vibrations in Surface-Enhanced Raman Scattering. Nano Lett 2022; 22:7254-7260. [PMID: 36037474 PMCID: PMC9479150 DOI: 10.1021/acs.nanolett.2c02806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 08/22/2022] [Indexed: 06/15/2023]
Abstract
Surface-enhanced Raman scattering (SERS) is typically assumed to occur at individual molecules neglecting intermolecular vibrational coupling. Here, we show instead how collective vibrations from infrared (IR) coupled dipoles are seen in SERS from molecular monolayers. Mixing IR-active molecules with IR-inactive spacer molecules controls the intermolecular separation. Intermolecular coupling leads to vibrational frequency upshifts up to 8 cm-1, tuning with the mixing fraction and IR dipole strength, in excellent agreement with microscopic models and density functional theory. These cooperative frequency shifts can be used as a ruler to measure intermolecular distance and disorder with angstrom resolution. We demonstrate this for photochemical reactions of 4-nitrothiophenol, which depletes the number of neighboring IR-active molecules and breaks the collective vibration, enabling direct tracking of the reaction. Collective molecular vibrations reshape SERS spectra and need to be considered in the analysis of vibrational spectra throughout analytical chemistry and sensing.
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Affiliation(s)
- Niclas
S. Mueller
- NanoPhotonics
Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Rakesh Arul
- NanoPhotonics
Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Lukas A. Jakob
- NanoPhotonics
Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
| | - Matthew Oliver Blunt
- Department
of Physics and Astronomy, University College
London, London WC1E 6BT, United Kingdom
| | - Tamás Földes
- Department
of Physics and Astronomy, University College
London, London WC1E 6BT, United Kingdom
| | - Edina Rosta
- Department
of Physics and Astronomy, University College
London, London WC1E 6BT, United Kingdom
| | - Jeremy J. Baumberg
- NanoPhotonics
Centre, Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
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Chikkaraddy R, Xomalis A, Jakob LA, Baumberg JJ. Publisher Correction: Mid-infrared-perturbed molecular vibrational signatures in plasmonic nanocavities. Light Sci Appl 2022; 11:41. [PMID: 35210397 PMCID: PMC8873403 DOI: 10.1038/s41377-022-00732-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Affiliation(s)
- Rohit Chikkaraddy
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, UK.
| | - Angelos Xomalis
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, UK
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Thun, Switzerland
| | - Lukas A Jakob
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Jeremy J Baumberg
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, UK.
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Chikkaraddy R, Xomalis A, Jakob LA, Baumberg JJ. Mid-infrared-perturbed molecular vibrational signatures in plasmonic nanocavities. Light Sci Appl 2022; 11:19. [PMID: 35042844 PMCID: PMC8766566 DOI: 10.1038/s41377-022-00709-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 11/15/2021] [Accepted: 01/05/2022] [Indexed: 05/04/2023]
Abstract
Recent developments in surface-enhanced Raman scattering (SERS) enable observation of single-bond vibrations in real time at room temperature. By contrast, mid-infrared (MIR) vibrational spectroscopy is limited to inefficient slow detection. Here we develop a new method for MIR sensing using SERS. This method utilizes nanoparticle-on-foil (NPoF) nanocavities supporting both visible and MIR plasmonic hotspots in the same nanogap formed by a monolayer of molecules. Molecular SERS signals from individual NPoF nanocavities are modulated in the presence of MIR photons. The strength of this modulation depends on the MIR wavelength, and is maximized at the 6-12 μm absorption bands of SiO2 or polystyrene placed under the foil. Using a single-photon lock-in detection scheme we time-resolve the rise and decay of the signal in a few 100 ns. Our observations reveal that the phonon resonances of SiO2 can trap intense MIR surface plasmons within the Reststrahlen band, tuning the visible-wavelength localized plasmons by reversibly perturbing the localized few-nm-thick water shell trapped in the nanostructure crevices. This suggests new ways to couple nanoscale bond vibrations for optomechanics, with potential to push detection limits down to single-photon and single-molecule regimes.
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Affiliation(s)
- Rohit Chikkaraddy
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, UK.
| | - Angelos Xomalis
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, UK
- Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Thun, Switzerland
| | - Lukas A Jakob
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, UK
| | - Jeremy J Baumberg
- NanoPhotonics Centre, Cavendish Laboratory, Department of Physics, JJ Thompson Avenue, University of Cambridge, Cambridge, CB3 0HE, UK.
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Hauler O, Wackenhut F, Jakob LA, Stuhl A, Laible F, Fleischer M, Meixner AJ, Braun K. Direct phase mapping of the light scattered by single plasmonic nanoparticles. Nanoscale 2020; 12:1083-1090. [PMID: 31845942 DOI: 10.1039/c9nr10358a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
In this work, we present a novel technique to directly measure the phase shift of the optical signal scattered by single plasmonic nanoparticles in a diffraction-limited laser focus. We accomplish this by equipping an inverted confocal microscope with a Michelson interferometer and scanning single nanoparticles through the focal volume while recording for each pixel interferograms of the scattered and a reference wave. For the experiments, lithographically prepared gold nanorods were used, since their plasmon resonances can be controlled via their aspect ratio. We have developed a theoretical model for image formation in confocal scattering microscopy for nanoparticles considerably smaller than the diffraction limited focus. We show that the phase shift observed for particles with different longitudinal particle plasmon resonances can be well explained by the harmonic oscillator model. The direct measurement of the phase shift can further improve the understanding of the elastic scattering of individual gold nanoparticles with respect to their plasmonic properties.
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Affiliation(s)
- Otto Hauler
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Tuebingen, 72076, Germany.
| | - Frank Wackenhut
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Tuebingen, 72076, Germany.
| | - Lukas A Jakob
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Tuebingen, 72076, Germany.
| | - Alexander Stuhl
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Tuebingen, 72076, Germany.
| | - Florian Laible
- Institute for Applied Physics, Eberhard Karls University, Tuebingen, 72076, Germany and Center for Light-Matter-Interaction, Sensors and Analytics LISA+, Eberhard Karls University, Tuebingen, 72076, Germany
| | - Monika Fleischer
- Institute for Applied Physics, Eberhard Karls University, Tuebingen, 72076, Germany and Center for Light-Matter-Interaction, Sensors and Analytics LISA+, Eberhard Karls University, Tuebingen, 72076, Germany
| | - Alfred J Meixner
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Tuebingen, 72076, Germany. and Center for Light-Matter-Interaction, Sensors and Analytics LISA+, Eberhard Karls University, Tuebingen, 72076, Germany
| | - Kai Braun
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Tuebingen, 72076, Germany. and Center for Light-Matter-Interaction, Sensors and Analytics LISA+, Eberhard Karls University, Tuebingen, 72076, Germany
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Wackenhut F, Jakob LA, Hauler O, Stuhl A, Laible F, Fleischer M, Braun K, Meixner AJ. Nanoscale plasmonic phase sensor. Anal Bioanal Chem 2020; 412:3405-3411. [PMID: 31919613 DOI: 10.1007/s00216-019-02340-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 12/03/2019] [Accepted: 12/09/2019] [Indexed: 12/30/2022]
Abstract
Using the localized surface plasmon resonance (LSPR) of gold nanoparticles for sensing applications has attracted considerable interest, since it can be very sensitive, even down to a single molecule, and selective for a specific analyte molecule with a suitable surface modification. LSPR sensing is usually based on the wavelength shift of the LSPR or a Fano resonance. Here, we present a new experimental approach based on the phase of the light scattered by a single gold nanoparticle by equipping a confocal microscope with an additional interferometer arm similar to a Michelson interferometer. The detected phase depends on the shape of the nanoparticle and the refractive index of the surrounding medium and can even be detected for off-resonant excitation. This can be used as a new and sensitive detection method in LSPR sensing, allowing the detection of changes to the local refractive index or the binding of molecules to the nanoparticle surface.
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Affiliation(s)
- Frank Wackenhut
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Auf der Morgenstelle 18, 72076, Tuebingen, Germany.
| | - Lukas A Jakob
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Auf der Morgenstelle 18, 72076, Tuebingen, Germany
| | - Otto Hauler
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Auf der Morgenstelle 18, 72076, Tuebingen, Germany
| | - Alexander Stuhl
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Auf der Morgenstelle 18, 72076, Tuebingen, Germany
| | - Florian Laible
- Institute for Applied Physics, Eberhard Karls University, Auf der Morgenstelle 10, 72076, Tuebingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics LISA+, Eberhard Karls University, Auf der Morgenstelle 15, 72076, Tuebingen, Germany
| | - Monika Fleischer
- Institute for Applied Physics, Eberhard Karls University, Auf der Morgenstelle 10, 72076, Tuebingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics LISA+, Eberhard Karls University, Auf der Morgenstelle 15, 72076, Tuebingen, Germany
| | - Kai Braun
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Auf der Morgenstelle 18, 72076, Tuebingen, Germany
- Center for Light-Matter-Interaction, Sensors and Analytics LISA+, Eberhard Karls University, Auf der Morgenstelle 15, 72076, Tuebingen, Germany
| | - Alfred J Meixner
- Institute of Physical and Theoretical Chemistry, Eberhard Karls University, Auf der Morgenstelle 18, 72076, Tuebingen, Germany.
- Center for Light-Matter-Interaction, Sensors and Analytics LISA+, Eberhard Karls University, Auf der Morgenstelle 15, 72076, Tuebingen, Germany.
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