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Valencia-Acuna P, Rijal K, Wang CF, Ziatdinov M, Chan WL, El-Khoury PZ. Visualizing nanoscale heterogeneity in perylene thin films via tip-enhanced photoluminescence with unsupervised machine learning. Chem Commun (Camb) 2024. [PMID: 38922599 DOI: 10.1039/d4cc01808g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/27/2024]
Abstract
We investigate the properties of ultrathin 3,4,9,10-perylenetetracarboxylic diimide (PTCDI) films using a combination of tip-enhanced photoluminescence and unsupervised machine learning. We expose nanoscale spectral heterogeneities that can be understood on the basis of the interplay between vibronic effects, intermolecular excitons, and intramolecular excitons in PTDCI films.
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Affiliation(s)
- Pavel Valencia-Acuna
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
| | - Kushal Rijal
- Department of Physics and Astronomy, The University of Kansas, Lawrence, KS 66045, USA.
| | - Chih-Feng Wang
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
| | - Maxim Ziatdinov
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
| | - Wai-Lun Chan
- Department of Physics and Astronomy, The University of Kansas, Lawrence, KS 66045, USA.
| | - Patrick Z El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA.
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2
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Mantilla ABC, Wang CF, Krayev A, Gu Y, Schultz ZD, El-Khoury PZ. Classical vs. quantum plasmon-induced molecular transformations at metallic nanojunctions. Proc Natl Acad Sci U S A 2024; 121:e2319233121. [PMID: 38547064 PMCID: PMC10998572 DOI: 10.1073/pnas.2319233121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 02/12/2024] [Indexed: 04/08/2024] Open
Abstract
Chemical transformations near plasmonic metals have attracted increasing attention in the past few years. Specifically, reactions occurring within plasmonic nanojunctions that can be detected via surface and tip-enhanced Raman (SER and TER) scattering were the focus of numerous reports. In this context, even though the transition between localized and nonlocal (quantum) plasmons at nanojunctions is documented, its implications on plasmonic chemistry remain poorly understood. We explore the latter through AFM-TER-current measurements. We use two molecules: i) 4-mercaptobenzonitrile (MBN) that reports on the (non)local fields and ii) 4-nitrothiophenol (NTP) that features defined signatures of its neutral/anionic forms and dimer product, 4,4'-dimercaptoazobenzene (DMAB). The transition from classical to quantum plasmons is established through our optical measurements: It is marked by molecular charging and optical rectification. Simultaneously recorded force and current measurements support our assignments. In the case of NTP, we observe the parent and DMAB product beneath the probe in the classical regime. Further reducing the gap leads to the collapse of DMAB to form NTP anions. The process is reversible: Anions subsequently recombine into DMAB. Our results have significant implications for AFM-based TER measurements and their analysis, beyond the scope of this work. In effect, when precise control over the junction is not possible (e.g., in SER and ambient TER), both classical and quantum plasmons need to be considered in the analysis of plasmonic reactions.
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Affiliation(s)
| | - Chih-Feng Wang
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA99352
| | | | - Yi Gu
- Department of Physics and Astronomy, Washington State University, Pullman, WA99164
| | - Zachary D. Schultz
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH43210
| | - Patrick Z. El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, WA99352
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Primera-Pedrozo OM, Mantilla ABC, Myers TL, Gu Y, El-Khoury PZ. Controlling the Fluctuating Tip-Enhanced Raman Spectra of Chloramben on Silver Nanocubes. Anal Chem 2024. [PMID: 38315807 DOI: 10.1021/acs.analchem.3c05542] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2024]
Abstract
Tip-enhanced Raman (TER) scattering from molecules residing at plasmonic junctions can be used to detect, identify, and image single molecules. This is most evident for flat molecules interrogated under conditions of extreme temperatures and pressure. It is also the case for (bio)molecular systems that feature preferred orientations/conformations under ambient laboratory conditions. More complex molecules that can adopt multiple conformations and/or feature different protonation or charge states give rise to complex TER spectra. We illustrate how the latter can be controlled in the case of chloramben molecules coated onto plasmonic silver nanocubes. We show that characteristic molecular Raman spectra cannot be obtained when tunneling plasmons are operative, i.e., when the tip is in direct contact with the chemically functionalized plasmonic nanoparticles. We rationalize these observations and propose an approach to less invasive and hence more analytical TER spectral imaging.
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Affiliation(s)
- Oliva M Primera-Pedrozo
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Alexander B C Mantilla
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, United States
| | - Tanya L Myers
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, 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, P.O. Box 999, Richland, Washington 99352, United States
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Wang CF, Krayev AV, El-Khoury PZ. Subnanometer Visualization of Spatially Varying Local Field Resonances that Drive Tip-Enhanced Optical Spectroscopy. NANO LETTERS 2023; 23:9114-9118. [PMID: 37751571 DOI: 10.1021/acs.nanolett.3c03028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/28/2023]
Abstract
Our knowledge of the electromagnetic fields that power modern nanoscale optical measurements, including (non)linear tip-enhanced Raman and photoluminescence, chiefly stems from numerical simulations. Aside from idealized in silico vs heterogeneous (nano)structures in the laboratory, challenges in quantitative descriptions of nanoscale light-matter interactions more generally stem from the very nature of the problem, which lies at the interface of classical and quantum theories. This is particularly the case in ultrahigh spatial resolution measurements that are sensitive to local optical field variations that take place on subnanometer length scales. This work approaches this challenge through extinction-based spectral nanoimaging experiments. We demonstrate <1 nm spatial resolution in hyperspectral extinction measurements that track spatially varying plasmon resonances. We describe the principles behind our experiments and highlight more general implications of our observations.
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Affiliation(s)
- Chih-Feng Wang
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Andrey V Krayev
- Horiba Instruments, Inc., 359 Bel Marin Keys Blvd., Suite 18, Novato, California 94949, United States
| | - Patrick Z El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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Wang CF, Mantilla ABC, Krayev A, Gu Y, El-Khoury PZ. Probing Local Optical Fields via Ultralow Frequency Raman Scattering from a Corrugated Probe. J Phys Chem Lett 2023; 14:8334-8338. [PMID: 37698921 DOI: 10.1021/acs.jpclett.3c02122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/14/2023]
Abstract
We revisit nanoscale local optical field imaging via tip-enhanced Raman scattering (TERS). Rather than taking advantage of molecular reporters to probe different aspects of the local fields, we show how ultralow frequency Raman (ULF) scattering from the (nanocorrugated) metallic probe itself can be used for the same purpose. The bright ULF-TERS response we record allows non-invasive (tapping mode feedback) local field imaging, enables visualization of the local fields of small (≥20 nm) isolated plasmonic particles, and can also be exploited to distinguish between Si and SiO2 domains with 5 nm spatial resolution. We describe our approach and its limitations, particularly when it comes to using all-metallic versus molecular reporters.
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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
| | - Andrey Krayev
- Horiba Instruments, Inc., 359 Bel Marin Keys Boulevard, Suite 18, Novato, California 94949, 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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El-Khoury PZ. High spatial resolution ambient tip-enhanced (multipolar) Raman scattering. Chem Commun (Camb) 2023; 59:3536-3541. [PMID: 36852462 DOI: 10.1039/d3cc00434a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
Abstract
This article summarizes lessons learnt from ambient tip-enhanced Raman (TER) mapping of molecules interacting with plasmonic nanostructures. It is shown that numerous physical and chemical phenomena contribute to high-resolution TER spectral images. As a result, selectively tracking interfacial chemical transformations via TERS is more challenging than currently appreciated.
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Affiliation(s)
- Patrick Z El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA, 99352, USA.
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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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Xie L, Gong K, Liu Y, Zhang L. Strategies and Challenges of Identifying Nanoplastics in Environment by Surface-Enhanced Raman Spectroscopy. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:25-43. [PMID: 36576086 DOI: 10.1021/acs.est.2c07416] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Nanoplastics (<1000 nm) have been evidenced to be universal in a variety of environmental media. They pose a potential cytotoxicity and health risk due to their tiny size, which allows them to easily penetrate biological barriers and enter cells. Here, we briefly review the various prevalent analytical techniques or tools for identifying nanoplastics, and further move to focus on their advantages and disadvantages. Surface-enhanced Raman spectroscopy (SERS) has been implemented for the identification of individual nanoparticles because of its high sensitivity to molecules and ease of rapid characterization. Therefore, we introduce the SERS technique in the following aspects, (1) principles of SERS; (2) strategies and advances in SERS detection of nanoplastics; and (3) applying SERS to real environmental samples. We put our effort into the summarization of efficient SERS substrates that essentially enable the better detection of nanoplastics, and extend to discuss how the reported nanoplastics pretreatment methodologies can bring SERS analysis to practical applications. A further step moving forward is to investigate the problems and challenges of currently applied SERS detection methods and to look at future research needs in nanoplastics detection employing SERS analysis.
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Affiliation(s)
- Lifang Xie
- Department of Environmental Science & Engineering, Fudan University, Shanghai200433, Peoples' Republic of China
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Fudan University, Shanghai200433, Peoples' Republic of China
- Shanghai Institute of Pollution Control and Ecological Security, Shanghai200092, Peoples' Republic of China
| | - Kedong Gong
- Department of Environmental Science & Engineering, Fudan University, Shanghai200433, Peoples' Republic of China
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Fudan University, Shanghai200433, Peoples' Republic of China
- Shanghai Institute of Pollution Control and Ecological Security, Shanghai200092, Peoples' Republic of China
| | - Yangyang Liu
- Department of Environmental Science & Engineering, Fudan University, Shanghai200433, Peoples' Republic of China
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Fudan University, Shanghai200433, Peoples' Republic of China
- Shanghai Institute of Pollution Control and Ecological Security, Shanghai200092, Peoples' Republic of China
| | - Liwu Zhang
- Department of Environmental Science & Engineering, Fudan University, Shanghai200433, Peoples' Republic of China
- Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention, Fudan University, Shanghai200433, Peoples' Republic of China
- Shanghai Institute of Pollution Control and Ecological Security, Shanghai200092, Peoples' Republic of China
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Wang CF, El-Khoury PZ. Multimodal (Non)Linear Optical Nanoimaging and Nanospectroscopy. J Phys Chem Lett 2022; 13:7350-7354. [PMID: 35921600 DOI: 10.1021/acs.jpclett.2c01993] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
This Perspective highlights recent advances in linear and nonlinear spectral nanoimaging. The described developments are motivated by the need to characterize molecular and material systems noninvasively with nanometer spatial and femtosecond temporal resolution. Indeed, the ability to image and chemically characterize heterogeneous interfaces with joint nano-femto resolution is a prerequisite to advancing our fundamental understanding of processes as diverse as heterogeneous catalysis, microbial communication, and energy flow in pristine/defect-containing low-dimensional quantum materials, to name a few. We describe pioneering work and recent demonstrations of (non)linear optical nanoimaging and nanospectroscopy, with an emphasis on high spatial resolution measurements conducted under ambient laboratory conditions.
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Affiliation(s)
- Chih-Feng Wang
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
| | - Patrick Z El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, United States
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O'Callahan BT, El-Khoury PZ. A Closer Look at Tip-Enhanced Raman Chemical Reaction Nanoimages. J Phys Chem Lett 2022; 13:3886-3889. [PMID: 35470671 DOI: 10.1021/acs.jpclett.2c00574] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Tip-enhanced Raman spectroscopy (TERS) is a powerful technique that enables ultrahigh spatial resolution and ultrasensitive chemical imaging. This technique's ability to track plasmon-induced/enhanced chemical reactions in real space has gained increasing popularity in recent years. In this study, we expose inherent difficulties associated with assigning TERS signatures that accompany chemical transformations. Namely, distinct selection rules as well as the possibility of multiple physical processes/chemical reaction pathways complicate spectral assignments and necessitate caution in assigning the experimental observables. We illustrate the latter using 4,4'-dimercaptostilbene-functionalized plasmonic silver nanocubes, wherein we identify the TERS signatures of product formation, molecular charging, multipolar Raman scattering, and preferred molecular orientations that all lead to distinct and assignable spectral patterns.
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Affiliation(s)
- Brian T O'Callahan
- Earth and Biological Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Patrick Z El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
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