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Takahashi S, Sakurai A, Mochizuki T, Sugimoto T. Broadband Tip-Enhanced Nonlinear Optical Response in a Plasmonic Nanocavity. J Phys Chem Lett 2023:6919-6926. [PMID: 37498197 DOI: 10.1021/acs.jpclett.3c01343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/28/2023]
Abstract
We report a significantly broad nonlinear optical response enhanced in a tip-substrate plasmonic nanocavity. Focusing on the near-field second harmonics of the wavelength-tunable femtosecond laser, we demonstrate that the tip-enhancement of nonlinear optical effects efficiently works over the broad wavelength range through the visible to infrared region. We also found that this broadband nonlinear optical property is directly affected not only by the nanometer-scale sharpness of the tip apexes but also by the micrometer-scale surface geometry of the tip shafts. While spatially nonlocal plasmonic modes excited throughout the micrometer-scale tip shafts enhance near-to-mid-infrared incoming light, the radiation of visible-to-near-infrared second harmonics is boosted by localized plasmons at the nanogap. These two plasmonic modes simultaneously affect the excitation and emission processes, realizing the strong and broad enhancement of second harmonic generation. Our results provide a new basis for the physical understanding and fine manipulation of nonlinear optical phenomena enhanced in plasmonic nanocavities.
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Affiliation(s)
- Shota Takahashi
- Department of Materials Molecular Science, Institute for Molecular Science (IMS), Okazaki, Aichi 444-8585, Japan
| | - Atsunori Sakurai
- Department of Materials Molecular Science, Institute for Molecular Science (IMS), Okazaki, Aichi 444-8585, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Okazaki, Aichi 444-8585, Japan
- Laser-Driven Electron-Acceleration Technology Group, RIKEN SPring-8 Center, Kouto, Sayocho, Hyogo 679-5148, Japan
| | - Tatsuto Mochizuki
- Department of Materials Molecular Science, Institute for Molecular Science (IMS), Okazaki, Aichi 444-8585, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Okazaki, Aichi 444-8585, Japan
| | - Toshiki Sugimoto
- Department of Materials Molecular Science, Institute for Molecular Science (IMS), Okazaki, Aichi 444-8585, Japan
- Graduate Institute for Advanced Studies, SOKENDAI, Okazaki, Aichi 444-8585, Japan
- Laser-Driven Electron-Acceleration Technology Group, RIKEN SPring-8 Center, Kouto, Sayocho, Hyogo 679-5148, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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El-Khoury PZ. Tip-Enhanced Raman Chemical and Chemical Reaction Imaging in H 2O with Sub-3-nm Spatial Resolution. J Am Chem Soc 2023; 145:6639-6642. [PMID: 36919918 DOI: 10.1021/jacs.3c01626] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
Abstract
Reproducible chemical and chemical reaction nanoimaging at solid-liquid interfaces remains challenging, particularly when resolutions on the order of a few nanometers are sought. In this work, we demonstrate the latter through liquid-tip-enhanced Raman (TER) measurements that target gold nanoplates functionalized with 4-mercaptobenzonitrile (MBN). In addition to chemical imaging and local optical field nanovisualization with high spatial resolution, we observe the signatures of 4-mercaptobenzoic acid, which forms as a result of plasmon-induced hydrolysis of MBN. Evidently, the solvent leads to distinct plasmon-induced/enhanced chemical reaction pathways that have not been documented. This work shows that such reactions that take place at solid-liquid interfaces can be tracked with a record sub-3-nm spatial resolution via TER spectral nanoimaging in liquids.
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Affiliation(s)
- Patrick Z El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
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Wang CF, Mantilla ABC, Gu Y, El-Khoury PZ. Ambient Tip-Enhanced Two Photon Photoluminescence from CdSe/ZnS Quantum Dots. J Phys Chem A 2023; 127:1081-1084. [PMID: 36689268 DOI: 10.1021/acs.jpca.2c07750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Nonlinear nano-optical measurements that combine ultrafast spectroscopy with tools of scanning probe microscopy are scarce. This is particularly the case when high spatial resolution on the order of a few nanometers is sought after in experiments performed under ambient laboratory conditions. In this work, we demonstrate the latter through measurements that track two-photon photoluminescence from aggregates of CdSe/ZnS quantum dots with sub-5 nm spatial resolution. Our proof-of-principle measurements that only take advantage of a plasmonic probe (as opposed to a gap mode) pave the way for nonlinear photoluminescence-based spectral nanoimaging of realistic/heterogeneous (bio) molecular and (bio) material systems.
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Affiliation(s)
- Chih-Feng Wang
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Alexander B C Mantilla
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, United States
| | - Yi Gu
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, United States
| | - Patrick Z El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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