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  1. Article ; Online: A Closer Look at Tip-Enhanced Raman Chemical Reaction Nanoimages.

    O'Callahan, Brian T / El-Khoury, Patrick Z

    The journal of physical chemistry letters

    2022  Volume 13, Issue 17, Page(s) 3886–3889

    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 ... ...

    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.
    MeSH term(s) Spectrum Analysis, Raman/methods
    Language English
    Publishing date 2022-04-26
    Publishing country United States
    Document type Journal Article
    ISSN 1948-7185
    ISSN (online) 1948-7185
    DOI 10.1021/acs.jpclett.2c00574
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Publisher Correction: Correlative chemical and elemental nano-imaging of morphology and disorder at the nacre-prismatic region interface in Pinctada margaritifera.

    O'Callahan, Brian T / Larsen, Amy / Leichty, Sarah / Cliff, John / Gagnon, Alex C / Raschke, Markus B

    Scientific reports

    2024  Volume 14, Issue 1, Page(s) 786

    Language English
    Publishing date 2024-01-08
    Publishing country England
    Document type Published Erratum
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-023-50290-2
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Publisher Correction

    Brian T. O’Callahan / Amy Larsen / Sarah Leichty / John Cliff / Alex C. Gagnon / Markus B. Raschke

    Scientific Reports, Vol 14, Iss 1, Pp 1-

    Correlative chemical and elemental nano-imaging of morphology and disorder at the nacre-prismatic region interface in Pinctada margaritifera

    2024  Volume 1

    Keywords Medicine ; R ; Science ; Q
    Language English
    Publishing date 2024-01-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Correlative chemical and elemental nano-imaging of morphology and disorder at the nacre-prismatic region interface in Pinctada margaritifera.

    O'Callahan, Brian T / Larsen, Amy / Leichty, Sarah / Cliff, John / Gagnon, Alex C / Raschke, Markus B

    Scientific reports

    2023  Volume 13, Issue 1, Page(s) 21258

    Abstract: Understanding biomineralization relies on imaging chemically heterogeneous organic-inorganic interfaces across a hierarchy of spatial scales. Further, organic minority phases are often responsible for emergent inorganic structures from the atomic ... ...

    Abstract Understanding biomineralization relies on imaging chemically heterogeneous organic-inorganic interfaces across a hierarchy of spatial scales. Further, organic minority phases are often responsible for emergent inorganic structures from the atomic arrangement of different polymorphs, to nano- and micrometer crystal dimensions, up to meter size mollusk shells. The desired simultaneous chemical and elemental imaging to identify sparse organic moieties across a large field-of-view with nanometer spatial resolution has not yet been achieved. Here, we combine nanoscale secondary ion mass spectroscopy (NanoSIMS) with spectroscopic IR s-SNOM imaging for simultaneous chemical, molecular, and elemental nanoimaging. At the example of Pinctada margaritifera mollusk shells we identify and resolve ~ 50 nm interlamellar protein sheets periodically arranged in regular ~ 600 nm intervals. The striations typically appear ~ 15 µm from the nacre-prism boundary at the interface between disordered neonacre to mature nacre. Using the polymorph distinctive IR-vibrational carbonate resonance, the nacre and prismatic regions are consistently identified as aragonite ([Formula: see text] cm
    Language English
    Publishing date 2023-12-01
    Publishing country England
    Document type Journal Article
    ZDB-ID 2615211-3
    ISSN 2045-2322 ; 2045-2322
    ISSN (online) 2045-2322
    ISSN 2045-2322
    DOI 10.1038/s41598-023-47446-5
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Nanoindentation-enhanced tip-enhanced Raman spectroscopy.

    Wang, Chih-Feng / O'Callahan, Brian T / Krayev, Andrey / El-Khoury, Patrick Z

    The Journal of chemical physics

    2021  Volume 154, Issue 24, Page(s) 241101

    Abstract: We combine nanoindentation, herein achieved using atomic force microscopy-based pulsed-force lithography, with tip-enhanced Raman spectroscopy (TERS) and imaging. Our approach entails indentation and multimodal characterization of otherwise flat Au ... ...

    Abstract We combine nanoindentation, herein achieved using atomic force microscopy-based pulsed-force lithography, with tip-enhanced Raman spectroscopy (TERS) and imaging. Our approach entails indentation and multimodal characterization of otherwise flat Au substrates, followed by chemical functionalization and TERS spectral imaging of the indented nanostructures. We find that the resulting structures, which vary in shape and size depending on the tip used to produce them, may sustain nano-confined and significantly enhanced local fields. We take advantage of the latter and illustrate TERS-based ultrasensitive detection/chemical fingerprinting as well as chemical reaction imaging-all using a single platform for nano-lithography, topographic imaging, hyperspectral dark field optical microscopy, and TERS.
    Language English
    Publishing date 2021-07-08
    Publishing country United States
    Document type Journal Article
    ZDB-ID 3113-6
    ISSN 1089-7690 ; 0021-9606
    ISSN (online) 1089-7690
    ISSN 0021-9606
    DOI 10.1063/5.0056541
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: The Prevalence of Anions at Plasmonic Nanojunctions: A Closer Look at

    Wang, Chih-Feng / O'Callahan, Brian T / Kurouski, Dmitry / Krayev, Andrey / El-Khoury, Patrick Z

    The journal of physical chemistry letters

    2020  Volume 11, Issue 10, Page(s) 3809–3814

    Abstract: We revisit the reductive coupling ... ...

    Abstract We revisit the reductive coupling of
    Language English
    Publishing date 2020-04-30
    Publishing country United States
    Document type Journal Article
    ISSN 1948-7185
    ISSN (online) 1948-7185
    DOI 10.1021/acs.jpclett.0c01006
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  7. Article: Power-Dependent Dual Analyte Tip-Enhanced Raman Spectral Imaging

    O’Callahan, Brian T / Bhattarai, Ashish / Schultz, Zachary D / El-Khoury, Patrick Z

    Journal of physical chemistry. 2020 June 18, v. 124, no. 28

    2020  

    Abstract: We explore the information content in tip-enhanced Raman (TER) spectral images of gold microplates coated with two distinct molecular reporters: 4-thiobenzonitrile (TBN) and 4-nitrothiophenol (NTP). Using our dual analyte approach, we rigorously ... ...

    Abstract We explore the information content in tip-enhanced Raman (TER) spectral images of gold microplates coated with two distinct molecular reporters: 4-thiobenzonitrile (TBN) and 4-nitrothiophenol (NTP). Using our dual analyte approach, we rigorously demonstrate pixel-limited spatial resolution in Raman nanoimages that are otherwise dominated by local optical fields that vary more gently in space. Reproducibility is ensured through power-dependent TERS mapping. Power-dependent imaging also (i) directly illustrates that TBN is more robust than NTP at higher laser powers and (ii) reveals an increase in population of the Stark-tuned nitrile resonances of TBN molecules with increasing incident laser power.
    Keywords Raman imaging ; coatings ; gold ; journals ; lasers ; physical chemistry ; population growth
    Language English
    Dates of publication 2020-0618
    Size p. 15454-15459.
    Publishing place American Chemical Society
    Document type Article
    Note NALT-AP-4-rerunAP2-fuzzy
    ISSN 1932-7455
    DOI 10.1021/acs.jpcc.0c05396
    Database NAL-Catalogue (AGRICOLA)

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  8. Article ; Online: Correlative chemical and elemental nano-imaging of morphology and disorder at the nacre-prismatic region interface in Pinctada margaritifera

    Brian T. O’Callahan / Amy Larsen / Sarah Leichty / John Cliff / Alex C. Gagnon / Markus B. Raschke

    Scientific Reports, Vol 13, Iss 1, Pp 1-

    2023  Volume 9

    Abstract: Abstract Understanding biomineralization relies on imaging chemically heterogeneous organic–inorganic interfaces across a hierarchy of spatial scales. Further, organic minority phases are often responsible for emergent inorganic structures from the ... ...

    Abstract Abstract Understanding biomineralization relies on imaging chemically heterogeneous organic–inorganic interfaces across a hierarchy of spatial scales. Further, organic minority phases are often responsible for emergent inorganic structures from the atomic arrangement of different polymorphs, to nano- and micrometer crystal dimensions, up to meter size mollusk shells. The desired simultaneous chemical and elemental imaging to identify sparse organic moieties across a large field-of-view with nanometer spatial resolution has not yet been achieved. Here, we combine nanoscale secondary ion mass spectroscopy (NanoSIMS) with spectroscopic IR s-SNOM imaging for simultaneous chemical, molecular, and elemental nanoimaging. At the example of Pinctada margaritifera mollusk shells we identify and resolve ~ 50 nm interlamellar protein sheets periodically arranged in regular ~ 600 nm intervals. The striations typically appear ~ 15 µm from the nacre-prism boundary at the interface between disordered neonacre to mature nacre. Using the polymorph distinctive IR-vibrational carbonate resonance, the nacre and prismatic regions are consistently identified as aragonite ( $${\overline{\nu }}_{a}=860$$ ν ¯ a = 860 cm−1) and calcite ( $${\overline{\nu }}_{c}=880$$ ν ¯ c = 880 cm−1), respectively. We observe previously unreported morphological features including aragonite subdomains encapsulated in extensions of the prism-covering organic membrane and regions of irregular nacre tablet formation coincident with dispersed organics. We also identify a ~ 200 nm region in the incipient nacre region with less well-defined crystal structure and integrated organics. These results show with the identification of the interlamellar protein layer how correlative nano-IR chemical and NanoSIMS elemental imaging can help distinguish different models proposed for shell growth in particular, and how organic function may relate to inorganic structure in other biomineralized systems in general.
    Keywords Medicine ; R ; Science ; Q
    Subject code 540
    Language English
    Publishing date 2023-12-01T00:00:00Z
    Publisher Nature Portfolio
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

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  9. Article ; Online: Spatio-Spectral Characterization of Multipolar Plasmonic Modes of Au Nanorods via Tip-Enhanced Raman Scattering.

    Bhattarai, Ashish / O'Callahan, Brian T / Wang, Chih-Feng / Wang, ShanYi / El-Khoury, Patrick Z

    The journal of physical chemistry letters

    2020  Volume 11, Issue 8, Page(s) 2870–2874

    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 ... ...

    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
    Language English
    Publishing date 2020-03-30
    Publishing country United States
    Document type Journal Article
    ISSN 1948-7185
    ISSN (online) 1948-7185
    DOI 10.1021/acs.jpclett.0c00485
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  10. Article ; Online: Influence of surface and intermolecular interactions on the properties of supported polyoxometalates.

    Primera-Pedrozo, Oliva M / Tan, Shuai / Zhang, Difan / O'Callahan, Brian T / Cao, Wenjin / Baxter, Eric T / Wang, Xue-Bin / El-Khoury, Patrick Z / Prabhakaran, Venkateshkumar / Glezakou, Vassiliki-Alexandra / Johnson, Grant E

    Nanoscale

    2023  Volume 15, Issue 12, Page(s) 5786–5797

    Abstract: Polyoxometalates (POMs) with localized radical or open-shell metal sites have the potential to be used as transformative electronic spin based molecular qubits (MQs) for quantum computing (QC). For practical applications, MQs have to be immobilized in ... ...

    Abstract Polyoxometalates (POMs) with localized radical or open-shell metal sites have the potential to be used as transformative electronic spin based molecular qubits (MQs) for quantum computing (QC). For practical applications, MQs have to be immobilized in electronically or optically addressable arrays which introduces interactions with supports as well as neighboring POMs. Herein, we synthesized Keggin POMs with both tungsten (W) and vanadium (V) addenda atoms. Ion soft landing, a highly-controlled surface modification technique, was used to deliver mass-selected V-doped POMs to different self-assembled monolayer surfaces on gold (SAMs) without the solvent, counterions, and contaminants that normally accompany deposition from solution. Alkylthiol, perfluorinated, and carboxylic-acid terminated monolayers were employed as representative model supports on which different POM-surface and POM-POM interactions were characterized. We obtained insights into the vibrational properties of supported V-doped POMs and how they are perturbed by interactions with specific surface functional groups using infrared reflection absorption and scattering-type scanning near-field optical microscopy, as well as tip enhanced Raman spectroscopy. Different functional groups on SAMs and nanoscale heterogeneity are both shown to modulate the observed spectroscopic signatures. Spectral shifts are also found to be dependent on POM-POM interactions. The electronic structure of the V-doped POMs was determined in the gas phase using negative ion photoelectron spectroscopy and on surfaces with scanning Kelvin probe microscopy. The chemical functionality and charge transfer properties of the SAMs are demonstrated to exert an influence on the charge state and electronic configuration of supported V-doped POMs. The geometric and electronic structure of the POMs were also calculated using density functional theory. Our joint experimental and theoretical findings provide insight into how V substitution as well as POM-surface and POM-POM interactions influence the vibrational properties of POMs.
    Language English
    Publishing date 2023-03-23
    Publishing country England
    Document type Journal Article
    ZDB-ID 2515664-0
    ISSN 2040-3372 ; 2040-3364
    ISSN (online) 2040-3372
    ISSN 2040-3364
    DOI 10.1039/d2nr06148a
    Database MEDical Literature Analysis and Retrieval System OnLINE

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