1
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Raciti D, Cockayne E, Vinson J, Schwarz K, Hight Walker AR, Moffat TP. SHINERS Study of Chloride Order-Disorder Phase Transition and Solvation of Cu(100). J Am Chem Soc 2024; 146:1588-1602. [PMID: 38170994 DOI: 10.1021/jacs.3c11812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS) and density functional theory (DFT) are used to probe Cl- adsorption and the order-disorder phase transition associated with the c(2 × 2) Cl- adlayer on Cu(100) in acid media. A two-component ν(Cu-Cl) vibrational band centered near 260 ± 1 cm-1 is used to track the potential dependence of Cl- adsorption. The potential dependence of the dominant 260 cm-1 component tracks the coverage of the fluctional c(2 × 2) Cl- phase on terraces in good agreement with the normalized intensity of the c(2 × 2) superstructure rods in prior surface X-ray diffraction (SXRD) studies. As the c(2 × 2) Cl- coverage approaches saturation, a second ν(Cu-Cl) component mode emerges between 290 and 300 cm-1 that coincides with the onset and stiffening of step faceting where Cl- occupies the threefold hollow sites to stabilize the metal kink saturated Cu <100> step edge. The formation of the c(2 × 2) Cl- adlayer is accompanied by the strengthening of ν(O-H) stretching modes in the adjacent non-hydrogen-bonded water at 3600 cm-1 and an increase in hydronium concentration evident in the flanking H2O modes at 3100 cm-1. The polarization of the water molecules and enrichment of hydronium arise from the combination of Cl- anionic character and lateral templating provided by the c(2 × 2) adlayer, consistent with SXRD studies. At negative potentials, Cl- desorption occurs followed by development of a sulfate νs(S═O) band. Below -1.1 V vs Hg/HgSO4, a new 200 cm-1 mode emerges congruent with hydride formation and surface reconstruction reported in electrochemical scanning tunneling microscopy studies.
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Affiliation(s)
- David Raciti
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Eric Cockayne
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - John Vinson
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Kathleen Schwarz
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Angela R Hight Walker
- Physical Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
| | - Thomas P Moffat
- Material Measurement Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States
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2
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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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3
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Itoh T, Procházka M, Dong ZC, Ji W, Yamamoto YS, Zhang Y, Ozaki Y. Toward a New Era of SERS and TERS at the Nanometer Scale: From Fundamentals to Innovative Applications. Chem Rev 2023; 123:1552-1634. [PMID: 36745738 PMCID: PMC9952515 DOI: 10.1021/acs.chemrev.2c00316] [Citation(s) in RCA: 46] [Impact Index Per Article: 46.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Indexed: 02/08/2023]
Abstract
Surface-enhanced Raman scattering (SERS) and tip-enhanced Raman scattering (TERS) have opened a variety of exciting research fields. However, although a vast number of applications have been proposed since the two techniques were first reported, none has been applied to real practical use. This calls for an update in the recent fundamental and application studies of SERS and TERS. Thus, the goals and scope of this review are to report new directions and perspectives of SERS and TERS, mainly from the viewpoint of combining their mechanism and application studies. Regarding the recent progress in SERS and TERS, this review discusses four main topics: (1) nanometer to subnanometer plasmonic hotspots for SERS; (2) Ångström resolved TERS; (3) chemical mechanisms, i.e., charge-transfer mechanism of SERS and semiconductor-enhanced Raman scattering; and (4) the creation of a strong bridge between the mechanism studies and applications.
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Affiliation(s)
- Tamitake Itoh
- Health
and Medical Research Institute, National
Institute of Advanced Industrial Science and Technology (AIST), 2217-14 Hayashi-cho, Takamatsu, 761-0395Kagawa, Japan
| | - Marek Procházka
- Faculty
of Mathematics and Physics, Institute of Physics, Charles University, Ke Karlovu 5, 121 16Prague 2, Czech Republic
| | - Zhen-Chao Dong
- Hefei
National Research Center for Physical Sciences at the Microscale, University of Science and Technique of China, Hefei230026, China
| | - Wei Ji
- College
of Chemistry, Chemical Engineering, and Resource Utilization, Northeast Forestry University, Harbin145040, China
| | - Yuko S. Yamamoto
- School
of Materials Science, Japan Advanced Institute
of Science and Technology (JAIST), Nomi, 923-1292Ishikawa, Japan
| | - Yao Zhang
- Hefei
National Research Center for Physical Sciences at the Microscale, University of Science and Technique of China, Hefei230026, China
| | - Yukihiro Ozaki
- School of
Biological and Environmental Sciences, Kwansei
Gakuin University, 2-1,
Gakuen, Sanda, 669-1330Hyogo, Japan
- Toyota
Physical and Chemical Research Institute, Nagakute, 480-1192Aichi, Japan
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4
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Zhang C, Min C, Li L, Zhang Y, Wei S, Wang X, Yuan X. Effect of the focused gap-plasmon mode on tip-enhanced Raman excitation and scattering. OPTICS EXPRESS 2023; 31:4216-4228. [PMID: 36785395 DOI: 10.1364/oe.481152] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 12/31/2022] [Indexed: 06/18/2023]
Abstract
As a powerful molecular detection approach, tip-enhanced Raman scattering (TERS) spectroscopy has the advantages of nanoscale spatial resolution, label-free detection and high enhancement factor, therefore has been widely used in fields of chemistry, materials and life sciences. A TERS system enhanced by the focused gap-plasmon mode composed of Surface Plasmon Polariton (SPP) focus and the metal probe has been reported, however, its underlying enhancement mechanism for Raman excitation and scattering remains to be deeply explored. Here, we focus on the different performances of optical focus and SPP focus in the TERS system, and verify that the cooperation of these two focuses can produce maximum enhancement in a local electromagnetic field. Further, the Purcell effect on sample scattering in such a system is studied for the enhancement of Raman scattering collection in the far field. Finally, the local field enhancement and the sample far-field scattering enhancement are combined to show a full view of the whole process of TERS enhancement. This research can be applied to optimize the excitation and collection of Raman signals in TERS systems, which is of great value for the research and development of TERS technology.
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5
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Mantilla ABC, Wang CF, Gu Y, Schultz ZD, El-Khoury PZ. Multipolar Raman Scattering vs Interfacial Nanochemistry: Case of 4-Mercaptopyridine on Gold. J Am Chem Soc 2022; 144:20561-20565. [PMID: 36343210 PMCID: PMC10193591 DOI: 10.1021/jacs.2c10132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Caution needs to be exercised in associating changes in plasmon-enhanced Raman spectra with chemical transformations. This is demonstrated through a detailed analysis of tip-enhanced Raman (TER) scattering from 4-mercaptopyridine (MPY) on gold. The substrate used consists of gold nanoplates atop a gold surface featuring heterogeneous grooves, all coated with a monolayer of MPY. The brightest spectra across the substrate exhibit features that can only be recovered by considering the generalized polarizability of oriented MPY molecules. The complex TER spectra we observe do not mark interfacial chemistry but rather multipolar TER scattering driven by local field gradients.
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Affiliation(s)
- Alexander B. C. Mantilla
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA
| | - Chih-Feng Wang
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA
| | - Yi Gu
- Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA
| | - Zachary D. Schultz
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, USA
| | - Patrick Z. El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA
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6
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Bryche JF, Vega M, Tempez A, Brulé T, Carlier T, Moreau J, Chaigneau M, Charette PG, Canva M. Spatially-Localized Functionalization on Nanostructured Surfaces for Enhanced Plasmonic Sensing Efficacy. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:3586. [PMID: 36296775 PMCID: PMC9609756 DOI: 10.3390/nano12203586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Revised: 10/07/2022] [Accepted: 10/10/2022] [Indexed: 06/16/2023]
Abstract
This work demonstrates the enhancement in plasmonic sensing efficacy resulting from spatially-localized functionalization on nanostructured surfaces, whereby probe molecules are concentrated in areas of high field concentration. Comparison between SERS measurements on nanostructured surfaces (arrays of nanodisks 110 and 220 nm in diameter) with homogeneous and spatially-localized functionalization with thiophenol demonstrates that the Raman signal originates mainly from areas with high field concentration. TERS measurements with 10 nm spatial resolution confirm the field distribution profiles predicted by the numerical modeling. Though this enhancement in plasmonic sensing efficacy is demonstrated with SERS, results apply equally well to any type of optical/plasmonic sensing on functionalized surfaces with nanostructuring.
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Affiliation(s)
- Jean-François Bryche
- Laboratoire Nanotechnologies Nanosystèmes (LN2-IRL 3463)-CNRS, Université de Sherbrooke, 3000 Boulevard de l’Université, Sherbrooke, QC J1K OA5, Canada
- Institut Interdisciplinaire d’Innovation Technologique (3IT), 3000 Boulevard de l’Université, Sherbrooke, QC J1K OA5, Canada
| | - Marlo Vega
- Laboratoire Nanotechnologies Nanosystèmes (LN2-IRL 3463)-CNRS, Université de Sherbrooke, 3000 Boulevard de l’Université, Sherbrooke, QC J1K OA5, Canada
- Institut Interdisciplinaire d’Innovation Technologique (3IT), 3000 Boulevard de l’Université, Sherbrooke, QC J1K OA5, Canada
- Laboratoire Charles Fabry—Institut d’Optique Graduate School, Université Paris-Saclay, CNRS, 91120 Palaiseau, France
| | | | | | | | - Julien Moreau
- Laboratoire Charles Fabry—Institut d’Optique Graduate School, Université Paris-Saclay, CNRS, 91120 Palaiseau, France
| | | | - Paul G. Charette
- Laboratoire Nanotechnologies Nanosystèmes (LN2-IRL 3463)-CNRS, Université de Sherbrooke, 3000 Boulevard de l’Université, Sherbrooke, QC J1K OA5, Canada
- Institut Interdisciplinaire d’Innovation Technologique (3IT), 3000 Boulevard de l’Université, Sherbrooke, QC J1K OA5, Canada
| | - Michael Canva
- Laboratoire Nanotechnologies Nanosystèmes (LN2-IRL 3463)-CNRS, Université de Sherbrooke, 3000 Boulevard de l’Université, Sherbrooke, QC J1K OA5, Canada
- Institut Interdisciplinaire d’Innovation Technologique (3IT), 3000 Boulevard de l’Université, Sherbrooke, QC J1K OA5, Canada
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7
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Conformational heterogeneity of molecules physisorbed on a gold surface at room temperature. Nat Commun 2022; 13:4133. [PMID: 35840568 PMCID: PMC9287342 DOI: 10.1038/s41467-022-31576-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Accepted: 06/22/2022] [Indexed: 11/16/2022] Open
Abstract
A quantitative single-molecule tip-enhanced Raman spectroscopy (TERS) study at room temperature remained a challenge due to the rapid structural dynamics of molecules exposed to air. Here, we demonstrate the hyperspectral TERS imaging of single or a few brilliant cresyl blue (BCB) molecules at room temperature, along with quantitative spectral analyses. Robust chemical imaging is enabled by the freeze-frame approach using a thin Al2O3 capping layer, which suppresses spectral diffusions and inhibits chemical reactions and contamination in air. For the molecules resolved spatially in the TERS image, a clear Raman peak variation up to 7.5 cm−1 is observed, which cannot be found in molecular ensembles. From density functional theory-based quantitative analyses of the varied TERS peaks, we reveal the conformational heterogeneity at the single-molecule level. This work provides a facile way to investigate the single-molecule properties in interacting media, expanding the scope of single-molecule vibrational spectroscopy studies. Tip-enhanced vibrational spectroscopy at room temperature is complicated by molecular conformational dynamics, photobleaching, contaminations, and chemical reactions in air. This study demonstrates that a sub-nm protective layer of Al2O3 provides robust conditions for probing single-molecule conformations.
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8
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Lu F, Zhang W, Sun L, Mei T, Yuan X. Enhancing electromagnetic field gradient in tip-enhanced Raman spectroscopy with a perfect radially polarized beam. OPTICS EXPRESS 2022; 30:21377-21385. [PMID: 36224858 DOI: 10.1364/oe.460394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 05/18/2022] [Indexed: 06/16/2023]
Abstract
Tip-enhanced Raman spectroscopy (TERS) is a promising label-free super-resolving imaging technique, and the electric field gradient of nanofocusing plays a role in TERS performance. In this paper, we theoretically investigated the enhancement and manipulation of the electric field gradient in a bottom-illumination TERS configuration through a tightly focused perfect radially polarized beam (PRPB). Improvement and manipulation in electric field enhancement and field gradient of the gap-plasmon mode between a plasmonic tip and a virtual surface plasmons (SPs) probe are achieved by adjusting the ring radius of the incident PRPB. Our results demonstrate that the method of optimizing the ring radius of PRPB is to make the illumination angle of incident light as close to the surface plasmon resonance (SPR) excitation angle as possible. Under the excitation of optimal parameters, more than 10 folds improvement of field enhancement and 3 times of field gradient of the gap-plasmon mode is realized compared with that of the conventional focused RPB. By this feat, our results indicate that such a method can further enhance the gradient Raman mode in TERS. We envision that the proposed method, to achieve the dynamic manipulation and enhancement of the nanofocusing field and field gradient, can be more broadly used to control light-matter interactions and extend the reach of tip-enhanced spectroscopy.
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9
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Abstract
Historically, molecular spectroscopists have focused their attention to the right-hand side of the Schrödinger equation. Our major goal had and still has to do with determining a (bio)molecular system's Hamiltonian operator. From a theoretical spectroscopist's perspective, this entails varying the parameters of a model Hamiltonian until the predicted observables agree with their experimental analogues. In this context, less emphasis has been put on the left-hand side of the equation, where the interplay between a system and its immediate local environment is described. The latter is particularly meaningful and informative in modern applications of optical microscopy and spectroscopy that take advantage of surface plasmons to enhance molecular scattering cross-sections and to increase the attainable spatial resolution that is classically limited by diffraction. Indeed, the manipulation of light near the apex of a metallic nanotip has enabled single molecule detection, identification, and imaging. The distinct advantages of the so-called tip-enhanced optical nanospectroscopy/nanoimaging approaches are self-evident: ultrahigh spatial resolution (nanometer or better) and ultimate sensitivity (down to yoctomolar) are both attainable, all while retaining the ability to chemically fingerprint one molecule at a time (e.g., through Raman scattering). An equally interesting aspect of the same approach stems from using the properties of a single molecule to characterize the local environment in which it resides. This concept of single molecule spectroscopy on the left-hand side of the Schrödinger equation is certainly not novel and has been discussed in pioneering single molecule studies that ultimately led to a Nobel prize in chemistry. That said, local environment mapping through ultrasensitive optical spectroscopy acquires a unique flavor when executed using tip-enhanced Raman scattering (TERS). This is the subject of this Account.In a series of recent reports, our group utilized TERS to characterize different properties of nanolocalized and enhanced optical fields. The platforms that were used to this end consist of chemically functionalized plasmonic nanostructures and nanoparticles imaged using visible-light-irradiated gold- or silver-coated probes of an atomic force microscope. Through a detailed analysis of the recorded spectral nanoimages, we found that molecular Raman spectra may be used to track the magnitudes, resonances, spatiotemporal gradients, and even vector components of optical fields with nanometer spatial resolution under ambient conditions. On the other side of the equation, understanding how spatially varying optical fields modulate molecular nano-Raman spectra is of utmost importance to emerging areas of nanophotonics. For instance, tracking plasmon-enhanced chemical transformations via TERS necessitates a deeper fundamental understanding of the optical signatures of molecular reorientation and multipolar Raman scattering, both of which may be driven by local optical field gradients that are operative in TERS. We illustrate these concepts and introduce the readers to the generally less appreciated and equally exciting world of TERS on the left-hand side of the Schrödinger equation.
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Affiliation(s)
- Patrick Z. El-Khoury
- Chemical Physics and Analysis Group, Physical Sciences Division, Pacific Northwest National Laboratory; Richland, Washington 99352, United States
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10
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Yuan L, Geng Z, Fan B, Guo F, Han C. State-of-the-art progress in tracking plasmon-mediated photoredox catalysis. PURE APPL CHEM 2021. [DOI: 10.1515/pac-2021-0205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Metal nanocrystals (NCs), particularly for plasmonic metal NCs with specific morphology and size, can strongly interact with ultraviolet-visible or even near-infrared photons to generate energetic charge carriers, localized heating, and electric field enhancement. These unique properties offer a promising opportunity for maneuvering solar-to-chemical energy conversion through different mechanisms. As distinct from previous works, in this review, recent advances of various characterization techniques in probing and monitoring the photophysical/photochemical processes, as well as the reaction mechanisms of plasmon-mediated photoredox catalysis are thoroughly summarized. Understanding how to distinguish and track these reaction mechanisms would furnish basic guidelines to design next-generation photocatalysts for plasmon-enhanced catalysis.
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Affiliation(s)
- Lan Yuan
- Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials , School of Chemistry and Chemical Engineering , Wuhan University of Science and Technology , Wuhan 430081 , China
| | - Zhaoyi Geng
- Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials , School of Chemistry and Chemical Engineering , Wuhan University of Science and Technology , Wuhan 430081 , China
| | - Baoan Fan
- Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials , School of Chemistry and Chemical Engineering , Wuhan University of Science and Technology , Wuhan 430081 , China
| | - Fen Guo
- Key Laboratory of Hubei Province for Coal Conversion and New Carbon Materials , School of Chemistry and Chemical Engineering , Wuhan University of Science and Technology , Wuhan 430081 , China
| | - Chuang Han
- Department of Chemistry , University of Cincinnati , Cincinnati , Ohio 45221 , USA
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11
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Zhao X, Campbell S, El-Khoury PZ, Jia Y, Wallace GQ, Claing A, Bazuin CG, Masson JF. Surface-Enhanced Raman Scattering Optophysiology Nanofibers for the Detection of Heavy Metals in Single Breast Cancer Cells. ACS Sens 2021; 6:1649-1662. [PMID: 33847111 DOI: 10.1021/acssensors.1c00332] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Mercury(II) ions (Hg2+) and silver ions (Ag+) are two of the most hazardous pollutants causing serious damage to human health. Here, we constructed surface-enhanced Raman scattering (SERS)-active nanofibers covered with 4-mercaptopyridine (4-Mpy)-modified gold nanoparticles to detect Hg2+ and Ag+. Experimental evidence suggests that the observed spectral changes originate from the combined effect of (i) the coordination between the nitrogen on 4-Mpy and the metal ions and (ii) the 4-Mpy molecular orientation (from flatter to more perpendicular with respect to the metal surface). The relative intensity of a pair of characteristic Raman peaks (at ∼428 and ∼708 cm-1) was used to quantify the metal ion concentration, greatly increasing the reproducibility of the measurement compared to signal-on or signal-off detection based on a single SERS peak. The detection limit of this method for Hg2+ is lower than that for the Ag+ (5 vs 100 nM), which can be explained by the stronger interaction energy between Hg2+ and N compared to Ag+ and N, as demonstrated by density functional theory calculations. The Hg2+ and Ag+ ions can be masked by adding ethylenediaminetetraacetate and Cl-, respectively, to the Hg2+ and Ag+ samples. The good sensitivity, high reproducibility, and excellent selectivity of these nanosensors were also demonstrated. Furthermore, detection of Hg2+ in living breast cancer cells at the subcellular level is possible, thanks to the nanometric size of the herein described SERS nanosensors, allowing high spatial resolution and minimal cell damage.
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Affiliation(s)
- Xingjuan Zhao
- Département de chimie, Centre québécois des matériaux fonctionnels (CQMF) and ⊥Regroupement québécois des matériaux de pointe (RQMP), Université de Montréal, C.P. 6128 Succ. Centre-Ville, Montréal, Quebec H3C 3J7, Canada
| | - Shirley Campbell
- Département de pharmacologie et physiologie, Université de Montréal, C.P. 6128 Succ. Centre-Ville, Montreal, Quebec H3C 3J7, Canada
| | - Patrick Z. El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Yuechen Jia
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
| | - Gregory Q. Wallace
- Département de chimie, Centre québécois des matériaux fonctionnels (CQMF) and ⊥Regroupement québécois des matériaux de pointe (RQMP), Université de Montréal, C.P. 6128 Succ. Centre-Ville, Montréal, Quebec H3C 3J7, Canada
| | - Audrey Claing
- Département de pharmacologie et physiologie, Université de Montréal, C.P. 6128 Succ. Centre-Ville, Montreal, Quebec H3C 3J7, Canada
| | - C. Geraldine Bazuin
- Département de chimie, Centre québécois des matériaux fonctionnels (CQMF) and ⊥Regroupement québécois des matériaux de pointe (RQMP), Université de Montréal, C.P. 6128 Succ. Centre-Ville, Montréal, Quebec H3C 3J7, Canada
| | - Jean-Francois Masson
- Département de chimie, Centre québécois des matériaux fonctionnels (CQMF) and ⊥Regroupement québécois des matériaux de pointe (RQMP), Université de Montréal, C.P. 6128 Succ. Centre-Ville, Montréal, Quebec H3C 3J7, Canada
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12
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Shi CF, Zheng B, Li J, Zhou Y, Liu HL, Ahmed SA, Wang K, Xia XH. Three-Dimensional Metamaterial for Plasmon-Enhanced Raman Scattering at any Excitation Wavelengths from the Visible to Near-Infrared Range. Anal Chem 2020; 93:1409-1415. [DOI: 10.1021/acs.analchem.0c03220] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Cai-Feng Shi
- State Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, 210023 Nanjing, China
| | - Bo Zheng
- State Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, 210023 Nanjing, China
| | - Jian Li
- State Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, 210023 Nanjing, China
| | - Yue Zhou
- State Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, 210023 Nanjing, China
| | - Hai-Ling Liu
- State Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, 210023 Nanjing, China
| | - Saud Asif Ahmed
- State Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, 210023 Nanjing, China
| | - Kang Wang
- State Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, 210023 Nanjing, China
| | - Xing-Hua Xia
- State Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, 210023 Nanjing, China
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13
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El-Khoury PZ, Schultz ZD. From SERS to TERS and Beyond: Molecules as Probes of Nanoscopic Optical Fields. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2020; 124:27267-27275. [PMID: 34306295 PMCID: PMC8297906 DOI: 10.1021/acs.jpcc.0c08337] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
A detailed understanding of the interaction between molecules and plasmonic nanostructures is important for several exciting developments in (bio)molecular sensing and imaging, catalysis, as well as energy conversion. While much of the focus has been on the nanostructures that generate enhanced and nano-confined optical fields, we herein highlight recent work from our groups that uses the molecular response in surface and tip enhanced Raman scattering (SERS and TERS, respectively) to investigate different aspects of the local fields. TERS provides access to ultra-confined volumes, and as a result can further explore and explain ensemble-averaged SERS measurements. Exciting and distinct molecular behaviors are observed in the quantum limit of plasmons, including molecular charging, chemical conversion, and optical rectification. Evidence of multipolar Raman scattering from molecules additionally provides insights into the inhomogeneous electric fields that drive SERS and TERS and their spatial and temporal gradients. The time scales of these processes show evidence of cooperative nanoscale phenomena that altogether contribute to SERS and TERS.
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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
| | - Zachary D Schultz
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA
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14
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Sartin MM, Su HS, Wang X, Ren B. Tip-enhanced Raman spectroscopy for nanoscale probing of dynamic chemical systems. J Chem Phys 2020; 153:170901. [PMID: 33167627 DOI: 10.1063/5.0027917] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Dynamics are fundamental to all aspects of chemistry and play a central role in the mechanism and product distribution of a chemical reaction. All dynamic processes are influenced by the local environment, so it is of fundamental and practical value to understand the structure of the environment and the dynamics with nanoscale resolution. Most techniques for measuring dynamic processes have microscopic spatial resolution and can only measure the average behavior of a large ensemble of sites within their sampling volumes. Tip-enhanced Raman spectroscopy (TERS) is a powerful tool for overcoming this limitation due to its combination of high chemical specificity and spatial resolution that is on the nanometer scale. Adapting it for the study of dynamic systems remains a work in progress, but the increasing sophistication of TERS is making such studies more routine, and there are now growing efforts to use TERS to examine more complex processes. This Perspective aims to promote development in this area of research by highlighting recent progress in using TERS to understand reacting and dynamic systems, ranging from simple model reactions to complex processes with practical applications. We discuss the unique challenges and opportunities that TERS presents for future studies.
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Affiliation(s)
- Matthew M Sartin
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Hai-Sheng Su
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Xiang Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
| | - Bin Ren
- State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China
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15
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Aprà E, Bhattarai A, Baxter E, Wang S, Johnson GE, Govind N, El-Khoury PZ. Simplified Ab Initio Molecular Dynamics-Based Raman Spectral Simulations. APPLIED SPECTROSCOPY 2020; 74:1350-1357. [PMID: 32285679 DOI: 10.1177/0003702820923392] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We describe a simplified approach to simulating Raman spectra from ab initio molecular dynamics (AIMD) calculations. The protocol relies on on-the-fly calculations of approximate molecular polarizabilities using the well-known sum over orbitals (as opposed to states) method. This approach bypasses the more accurate but computationally expensive approach to calculating molecular polarizabilities along AIMD trajectories, i.e., solving the coupled perturbed Hartree-Fock/Kohn-Sham equations. We demonstrate the advantages and limitations of our method through a few case studies targeting molecular systems of interest to surface- and/or tip-enhanced Raman spectroscopy practitioners.
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Affiliation(s)
- Edoardo Aprà
- Environmental and Molecular Sciences Laboratory, 6865Pacific Northwest National Laboratory, Richland, USA
| | - Ashish Bhattarai
- Physical Sciences Division, 6865Pacific Northwest National Laboratory, Richland, USA
| | - Eric Baxter
- Physical Sciences Division, 6865Pacific Northwest National Laboratory, Richland, USA
| | - ShanYi Wang
- Physical Sciences Division, 6865Pacific Northwest National Laboratory, Richland, USA
| | - Grant E Johnson
- Physical Sciences Division, 6865Pacific Northwest National Laboratory, Richland, USA
| | - Niranjan Govind
- Environmental and Molecular Sciences Laboratory, 6865Pacific Northwest National Laboratory, Richland, USA
| | - Patrick Z El-Khoury
- Physical Sciences Division, 6865Pacific Northwest National Laboratory, Richland, USA
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16
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Wang CF, O'Callahan BT, Kurouski D, Krayev A, Schultz ZD, El-Khoury PZ. Suppressing Molecular Charging, Nanochemistry, and Optical Rectification in the Tip-Enhanced Raman Geometry. J Phys Chem Lett 2020; 11:5890-5895. [PMID: 32619091 DOI: 10.1021/acs.jpclett.0c01413] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Classical versus quantum plasmons are responsible for the recorded signals in non-contact-mode versus contact-mode tip-enhanced Raman spectroscopy (TERS) and lead to distinct observables. Under otherwise identical experimental conditions, we illustrate the concept through tapping- and contact-mode TERS mapping of chemically functionalized silver nanocubes. Whereas molecular charging, chemical transformations, and optical rectification are prominent observables in contact-mode TERS, the same effects are suppressed using tapping-mode feedback. In effect, this work demonstrates that nanoscale physical and chemical processes can be accessed and/or suppressed on demand in the TERS geometry. The advantages of tapping-mode TERS are otherwise highlighted with the latter in mind.
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Affiliation(s)
| | | | - Dmitry Kurouski
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843, United States
| | - Andrey Krayev
- Horiba Instruments Inc., 359 Bel Marin Keys Boulevard, Suite 18, Novato, California 94949, United States
| | - Zachary D Schultz
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
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17
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Sloan-Dennison S, Zoltowski CM, El-Khoury PZ, Schultz ZD. Surface Enhanced Raman Scattering Selectivity in Proteins Arises from Electron Capture and Resonant Enhancement of Radical Species. THE JOURNAL OF PHYSICAL CHEMISTRY. C, NANOMATERIALS AND INTERFACES 2020; 124:9548-9558. [PMID: 32542105 PMCID: PMC7295139 DOI: 10.1021/acs.jpcc.0c01436] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Plasmon-enhanced Raman scattering is a powerful approach to detecting and characterizing proteins in live and dynamic biological systems. However, the selective detection/enhancement of specific residues as well as spectral diffusion and fluctuations have complicated the interpretation of enhanced Raman spectra and images of biological matter. In this work, we demonstrate that the amino acid tryptophan (Trp) can capture an electron from an excited plasmon, which generates a radical anion that is resonantly enhanced: a visible excited electronic state slides into resonance upon charging. This surface enhanced resonance Raman scattering (SERRS) mechanism explains the persistence of Trp signatures in the SERS and TERS spectra of proteins. Evidence for this picture includes the observation of visible resonances in the UV-Vis extinction spectrum, changes in the ground state vibrational spectrum, and plasmon-resonance dependent behavior. DFT calculations support the experimental observations. The behavior observed from the free Trp molecule is shown to explain the SERS spectrum of the Trp-cage protein. In effect, resonant Raman scattering from radicals formed through plasmonic excitation represents an under-investigated mechanism that may be exploited for chemical sensing applications.
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Affiliation(s)
- Sian Sloan-Dennison
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, 43210
| | - Chelsea M. Zoltowski
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, 43210
| | - Patrick Z. El-Khoury
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA
| | - Zachary D. Schultz
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, 43210
- corresponding author
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18
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Bhattarai A, O'Callahan BT, Wang CF, Wang S, El-Khoury PZ. Spatio-Spectral Characterization of Multipolar Plasmonic Modes of Au Nanorods via Tip-Enhanced Raman Scattering. J Phys Chem Lett 2020; 11:2870-2874. [PMID: 32208725 DOI: 10.1021/acs.jpclett.0c00485] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Tip-enhanced Raman (TER) spectral images of 4-thiobenzonitrile-coated Au nanorods map the spatial profiles and trace the resonances of dipolar and multipolar plasmonic modes that are characteristic of the imaged particles. For any particular rod, we observe sequential transitions between high-order modes at low frequency shifts and lower-order modes at higher frequencies. We also notice that higher-order modes (up to m = 4) are generally observed for long rods as compared to their shorter analogues, where longitudinal dipolar resonances (m = 1) are observable. In effect, this work adds a new dimension to local optical field mapping via TERS, which we have previously explored. Not only can the magnitudes, vector components, local/nonlocal characters of local optical fields be imaged through molecular TERS, but spatially varying local optical resonances are also direct observables.
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Affiliation(s)
- Ashish Bhattarai
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Brian T O'Callahan
- Earth and Biological Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Chih-Feng Wang
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - ShanYi Wang
- Physical 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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19
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Wang CF, Cheng Z, O'Callahan BT, Crampton KT, Jones MR, El-Khoury PZ. Tip-Enhanced Multipolar Raman Scattering. J Phys Chem Lett 2020; 11:2464-2469. [PMID: 32160470 DOI: 10.1021/acs.jpclett.0c00559] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We record nanoscale chemical images of thiobenzonitrile (TBN)-functionalized plasmonic gold nanocubes via tip-enhanced Raman spectroscopy (TERS). The spatially averaged optical response is dominated by conventional (dipolar) TERS scattering from TBN but also contains weaker spectral signatures in the 1225-1500 cm-1 region. The weak optical signatures dominate several of the recorded single-pixel TERS spectra. We can uniquely assign these Raman-forbidden transitions to multipolar Raman scattering, which implicates spatially varying enhanced electric field gradients at plasmonic tip-sample nanojunctions. Specifically, we can assign observations of tip-enhanced electric dipole-magnetic dipole as well as electric dipole-electric quadrupole driven transitions. Multipolar Raman scattering and local optical field gradients both need to be understood and accounted for in the interpretation of TERS spectral images, particularly in ongoing quests aimed at chemical reaction mapping via TERS.
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Affiliation(s)
- Chih-Feng Wang
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Zhihua Cheng
- Department of Chemistry, Department of Materials Science & Nanoengineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Brian T O'Callahan
- Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Kevin T Crampton
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Matthew R Jones
- Department of Chemistry, Department of Materials Science & Nanoengineering, Rice University, 6100 Main Street, Houston, Texas 77005, 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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20
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Bhattarai A, Cheng Z, Joly AG, Novikova IV, Evans JE, Schultz ZD, Jones MR, El-Khoury PZ. Tip-Enhanced Raman Nanospectroscopy of Smooth Spherical Gold Nanoparticles. J Phys Chem Lett 2020; 11:1795-1801. [PMID: 32069408 DOI: 10.1021/acs.jpclett.0c00217] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We record nanoscale-resolved chemical images of thiobenzonitrile (TBN)-functionalized smooth gold nanospheres on silicon via tip-enhanced Raman (TER) nanospectroscopy. The recorded images trace the nascence of the familiar doughnut-shaped scattering profile of nanoparticles on silicon at its origin (the particle surface), which appears as a horseshoe-shaped scattering pattern under our experimental conditions. The local optical field maps are in agreement with their simulated finite-difference time-domain analogues. Analysis of the recorded spectra with the aid of ab-initio-molecular-dynamics-based Raman spectral simulations further suggests that optical rectification and molecular charging take place throughout the course of atomic-force-microscopy-based TER nanoscale chemical imaging.
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Affiliation(s)
- Ashish Bhattarai
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Zhihua Cheng
- Department of Chemistry, Department of Materials Science & Nanoengineering, Rice University, 6100 Main Street, Houston, Texas 77005, United States
| | - Alan G Joly
- Physical Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Irina V Novikova
- Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - James E Evans
- Environmental and Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, United States
| | - Zachary D Schultz
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Matthew R Jones
- Department of Chemistry, Department of Materials Science & Nanoengineering, Rice University, 6100 Main Street, Houston, Texas 77005, 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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21
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Touzalin T, Joiret S, Lucas IT, Maisonhaute E. Electrochemical tip-enhanced Raman spectroscopy imaging with 8 nm lateral resolution. Electrochem commun 2019. [DOI: 10.1016/j.elecom.2019.106557] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
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22
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Aprà E, Bhattarai A, El-Khoury PZ. Gauging Molecular Orientation through Time Domain Simulations of Surface-Enhanced Raman Scattering. J Phys Chem A 2019; 123:7142-7147. [DOI: 10.1021/acs.jpca.9b06182] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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23
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High-resolution tip-enhanced Raman scattering probes sub-molecular density changes. Nat Commun 2019; 10:2567. [PMID: 31189893 PMCID: PMC6561954 DOI: 10.1038/s41467-019-10618-x] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 05/22/2019] [Indexed: 11/18/2022] Open
Abstract
Tip-enhanced Raman spectroscopy (TERS) exhibits new selection rule and sub-nanometer spatial resolution, which is attributed to the plasmonic near-field confinement. Despite recent advances in simulations of TERS spectra under highly confined fields, a simply physical mechanism has remained elusive. In this work we show that single-molecule TERS images can be explained by local sub-molecular density changes induced by the confined near-field during the Raman process. The local sub-molecular density changes determine the spatial resolution in TERS and the gradient-based selection rule. Using this approach we find that the four-fold symmetry of meso-tetrakis(3,5-di-tert-butylphenyl)porphyrin (H2TBPP) TERS images observed in experiments arises from the combination of degenerate normal modes localized in the functional side groups rather than the porphyrin ring as previously considered. As an illustration of the potential of the method, we demonstrate how this new theory can be applied to microscopic structure characterization. Despite recent advances in simulations of tip-enhanced Raman spectroscopy (TERS) under highly confined fields, a simply physical mechanism has remained elusive. Here, the authors show that single molecule TERS images can be explained by local sub-molecular density changes induced by the confined near-field during the Raman process.
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24
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Bhattarai A, El-Khoury PZ. Nanoscale Chemical Reaction Imaging at the Solid-Liquid Interface via TERS. J Phys Chem Lett 2019; 10:2817-2822. [PMID: 31074285 DOI: 10.1021/acs.jpclett.9b00935] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Not all regions of optical field nanolocalization and enhancement are suitable sites for chemical transformations on plasmonic metals. We illustrate the concept using chemically functionalized monocrystalline gold platelets in aqueous solution imaged using a Au-coated tip-enhanced Raman scattering (TERS) probe. For our proof-of-principle study, we select a model plasmon-driven chemical process, namely, the dimerization of p-nitrothiophenol (NTP) to dimercaptoazobenzene. Consistent with recent observations from our group, we find that TERS maps at vibrational resonances corresponding to NTP trace the optical fields that are maximally enhanced toward the edges of the platelets. Conversely, simultaneously recorded product maps reveal that the dimerization process occurs only at specific sites on our substrate. Given the uniformity of the structures and local optical fields at the edges of the gold platelets, our results suggest that molecular crowding and steric effects play a key role in our case of plasmon-driven NTP dimerization at the gold-water interface.
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Affiliation(s)
- Ashish Bhattarai
- Physical 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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25
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Kang G, Yang M, Mattei MS, Schatz GC, Van Duyne RP. In Situ Nanoscale Redox Mapping Using Tip-Enhanced Raman Spectroscopy. NANO LETTERS 2019; 19:2106-2113. [PMID: 30763517 DOI: 10.1021/acs.nanolett.9b00313] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Electrochemical atomic force microscopy tip-enhanced Raman spectroscopy (EC-AFM-TERS) was used for the first time to spatially resolve local heterogeneity in redox behavior on an electrode surface in situ and at the nanoscale. A structurally well-defined Au(111) nanoplate located on a polycrystalline ITO substrate was studied to examine nanoscale redox contrast across the two electrode materials. By monitoring the TERS intensity of adsorbed Nile Blue (NB) molecules on the electrode surface, TERS maps were acquired with different applied potentials. The EC-TERS maps showed a spatial contrast in TERS intensity between Au and ITO. TERS line scans near the edge of a 20 nm-thick Au nanoplate demonstrated a spatial resolution of 81 nm under an applied potential of -0.1 V vs Ag/AgCl. The intensities from the TERS maps at various applied potentials followed Nernstian behavior, and a formal potential ( E0') map was constructed by fitting the TERS intensity at each pixel to the Nernst equation. Clear nanoscale spatial contrast between the Au and ITO regions was observed in the E0' map. In addition, statistical analysis of the E0' map identified a statistically significant 4 mV difference in E0' on Au vs ITO. Electrochemical heterogeneity was also evident in the E0' distribution, as a bimodal distribution was observed in E0' on polycrystalline ITO, but not on gold. A direct comparison between an AFM friction image and the E0' map resolved the electrochemical behavior of individual ITO grains with a spatial resolution of ∼40 nm. The variation in E0' was attributed to different local surface charges on the ITO grains. Such site-specific electrochemical information with nanoscale spatial and few mV voltage resolutions is not available using ensemble spectroelectrochemical methods. We expect that in situ redox mapping at the nanoscale using EC-AFM-TERS will have a crucial impact on understanding the role of nanoscale surface features in applications such as electrocatalysis.
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Affiliation(s)
- Gyeongwon Kang
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States
| | - Muwen Yang
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States
| | - Michael S Mattei
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States
| | - George C Schatz
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States
| | - Richard P Van Duyne
- Department of Chemistry , Northwestern University , Evanston , Illinois 60208 , United States
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26
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Bhattarai A, Crampton KT, Joly AG, Kovarik L, Hess WP, El-Khoury PZ. Imaging the Optical Fields of Functionalized Silver Nanowires through Molecular TERS. J Phys Chem Lett 2018; 9:7105-7109. [PMID: 30517015 DOI: 10.1021/acs.jpclett.8b03324] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
We image 4-mercaptobenzonitrile-functionalized silver nanowires (∼20 nm diameter) through tip-enhanced Raman scattering (TERS). The enhanced local optical field-molecular interactions that govern the recorded hyperspectral TERS images are dissected through hybrid finite-difference time-domain density functional theory simulations. Our forward simulations illustrate that the recorded spatiospectral profiles of the chemically functionalized nanowires may be reproduced by accounting for the interaction between orientationally averaged molecular polarizability derivative tensors and enhanced incident/scattered local fields polarized along the tip axis. In effect, we directly map the enhanced optical fields of the nanowire in real space through TERS. The simultaneously recorded atomic force microscopy (AFM) images allow a direct comparison between our attainable spatial resolution in topographic (13 nm) and TERS (5 nm) imaging measurements performed under ambient conditions. Overall, our described protocol enables local electric field imaging with few nm precision through molecular TERS, and it is therefore generally applicable to a variety of plasmonic nanostructures.
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27
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Foti A, Barreca F, Fazio E, D’Andrea C, Matteini P, Maragò OM, Gucciardi PG. Low cost tips for tip-enhanced Raman spectroscopy fabricated by two-step electrochemical etching of 125 µm diameter gold wires. BEILSTEIN JOURNAL OF NANOTECHNOLOGY 2018; 9:2718-2729. [PMID: 30416923 PMCID: PMC6204785 DOI: 10.3762/bjnano.9.254] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2018] [Accepted: 10/08/2018] [Indexed: 05/26/2023]
Abstract
Tip-enhanced Raman spectroscopy (TERS) has become a well-applied technique for nanospectroscopy, allowing for single molecule sensitivity with sub-nanometer spatial resolution. The demand for efficient, reproducible and cost-effective probes for TERS is increasing. Here we report on a new electrochemical etching protocol to fabricate TERS tips starting from 125 µm diameter gold wires in a reproducible way. The process is reliable (50% of the tips have radius of curvature <35 nm, 66% <80 nm), fast (less than 2 min) and 2.5 times cheaper than the etching of standard 250 µm diameter wires. The TERS performance of the tips is tested on dyes, pigments and biomolecules and enhancement factors higher than 105 are observed. TERS mapping with a spatial resolution of 5 nm is demonstrated.
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Affiliation(s)
- Antonino Foti
- CNR-IPCF, Istituto per i Processi Chimico-Fisici, Viale F. Stagno D’Alcontres 37, 98168 Messina, Italy
| | - Francesco Barreca
- Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Università degli Studi di Messina, Viale F. Stagno d’Alcontres 31, 98166 Messina, Italy
| | - Enza Fazio
- Dipartimento di Scienze Matematiche e Informatiche, Scienze Fisiche e Scienze della Terra, Università degli Studi di Messina, Viale F. Stagno d’Alcontres 31, 98166 Messina, Italy
| | - Cristiano D’Andrea
- IFAC-CNR, Institute of Applied Physics “Nello Carrara”, National Research Council, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy
| | - Paolo Matteini
- IFAC-CNR, Institute of Applied Physics “Nello Carrara”, National Research Council, Via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy
| | - Onofrio Maria Maragò
- CNR-IPCF, Istituto per i Processi Chimico-Fisici, Viale F. Stagno D’Alcontres 37, 98168 Messina, Italy
| | - Pietro Giuseppe Gucciardi
- CNR-IPCF, Istituto per i Processi Chimico-Fisici, Viale F. Stagno D’Alcontres 37, 98168 Messina, Italy
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28
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Aprà E, Bhattarai A, Crampton KT, Bylaska EJ, Govind N, Hess WP, El-Khoury PZ. Time Domain Simulations of Single Molecule Raman Scattering. J Phys Chem A 2018; 122:7437-7442. [PMID: 30148635 DOI: 10.1021/acs.jpca.8b05912] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Nonequilibrium chemical phenomena are known to play an important role in single molecule microscopy and spectroscopy. Herein, we explore these effects through ab initio molecular dynamics (AIMD)-based Raman spectral simulations. We target an isolated aromatic thiol (thiobenzonitrile, TBN) as a prototypical molecular system. We first show that the essential features contained in the ensemble-averaged Raman spectrum of TBN can be reproduced by averaging over 18 short AIMD trajectories spanning a total simulation time of ∼60 ps. This involved more than 90 000 polarizability calculations at the B3LYP/def2-TZVP level of theory. We then illustrate that the short trajectories (∼3.3 ps total simulation time), where the accessible phase space is not fully sampled, provide a starting point for understanding key features that are often observed in measurements targeting single molecules. Our results suggest that a complete understanding of single molecule Raman scattering needs to account for molecular conformational flexibility and nonequilibrium chemical phenomena in addition to local optical fields and modified selection rules. The former effects are well-captured using the described AIMD-based single molecule Raman spectral simulations.
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29
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Bhattarai A, Krayev A, Temiryazev A, Evplov D, Crampton KT, Hess WP, El-Khoury PZ. Tip-Enhanced Raman Scattering from Nanopatterned Graphene and Graphene Oxide. NANO LETTERS 2018; 18:4029-4033. [PMID: 29791800 DOI: 10.1021/acs.nanolett.8b01690] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Tip-enhanced Raman spectroscopy (TERS) is particularly sensitive to analytes residing at plasmonic tip-sample nanojunctions, where the incident and scattered optical fields may be localized and optimally enhanced. However, the enhanced local electric fields in this so-called gap-mode TERS configuration are nominally orthogonal to the sample plane. As such, any given Raman active vibrational eigenstate needs to have projections (of its polarizability derivative tensor elements) along the sample normal to be detectable via TERS. The faint TERS signals observed from two prototypical systems, namely, pristine graphene and graphene oxide are a classical example of the aforementioned rather restrictive TERS selection rules in this context. In this study, we demonstrate that nanoindentation, herein achieved using pulsed-force lithography with a sharp single-crystal diamond atomic force microscope probe, may be used to locally enhance TERS signals from graphene and graphene oxide flakes on gold. Nanoindentation locally perturbs the otherwise flat graphene structure and introduces out-of-plane protrusions that generate enhanced TERS. Although our approach is nominally invasive, we illustrate that the introduced nanodefects are highly localized, as evidenced by TERS nanoscale chemical mapping. As such, the described protocol may be used to extend and generalize the applicability of TERS for the rapid identification of two-dimensional material systems on the nanoscale.
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Affiliation(s)
- Ashish Bhattarai
- Physical Sciences Division , Pacific Northwest National Laboratory , P.O. Box 999, Richland , Washington 99352 , United States
| | - Andrey Krayev
- Horiba Instruments Inc. , 359 Bel Marin Keys Boulevard, Suite 20 , Novato , California 94949 , United States
| | - Alexey Temiryazev
- Kotel'nikov Institute of Radioengineering and Electronics of RAS, Fryazino Branch , Vvedensky Square 1 , Fryazino 141190 , Russia
| | - Dmitry Evplov
- Horiba Instruments Inc. , 359 Bel Marin Keys Boulevard, Suite 20 , Novato , California 94949 , United States
| | - Kevin T Crampton
- Physical Sciences Division , Pacific Northwest National Laboratory , P.O. Box 999, Richland , Washington 99352 , United States
| | - Wayne P Hess
- Physical 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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