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  1. Article ; Online: Plasmonic couplings in Ag-Au heterodimers.

    Gomrok, Saghar / Eldridge, Brinton King / Chaffin, Elise A / Barr, James W / Huang, Xiaohua / Hoang, Thang B / Wang, Yongmei

    The Journal of chemical physics

    2024  Volume 160, Issue 14

    Abstract: The plasmonic coupling between silver (Ag) and gold (Au) nanoparticles (NPs) under four polarization modes was examined: a longitudinal mode (L-mode), where the electric field of a linearly polarized incident light parallels the dimer axis, and three ... ...

    Abstract The plasmonic coupling between silver (Ag) and gold (Au) nanoparticles (NPs) under four polarization modes was examined: a longitudinal mode (L-mode), where the electric field of a linearly polarized incident light parallels the dimer axis, and three transverse modes (T-modes), where the electric field of the light is perpendicular to the dimer axis. The coupling was studied using the discrete dipole approximation followed by an in-house postprocessing code that determines the extinction (Qext), absorption (Qabs), and near-field (Qnf) spectra from the individual NPs as well as the whole system. In agreement with the literature results, the extinction/absorption spectra of the whole dimer have two peaks, one near the Ag localized surface plasmon resonance (LSPR) region and the other at the Au LSPR region, with the peak at Ag LSPR being reduced in all modes and the peak at Au LSPR being red-shifted and increased in the L-mode but not in the T-modes. It is further shown that the scattering at the Ag LSPR region is reduced and becomes less than the isolated Ag NPs, but the absorption at the Ag LSPR is increased and becomes greater than the isolated Ag NPs for the 50 nm Ag-Au heterodimer. This suggests that the scattering from Ag NPs is being reabsorbed by the neighboring Au NPs due to the interband electronic transition in Au at that wavelength range. The Qext from the individual NP in the heterodimer shows the presence of the Fano profile on the Au NP but not on the Ag NP. This phenomenon was further investigated by using a dielectric particle (DP) placed near the Ag or Au NPs. The Fano profile appears in the absorbing DP spectra placed near either Ag or Au NPs. However, the Fano profile is masked upon further increases in the refractive index value of the DP particle. This explains the absence of a Fano profile on the Ag NPs in the Ag-Au heterodimer. The large near-field enhancement on both Ag and Au NPs at the Au plasmonic wavelength in the L-mode for large NPs was investigated through a DP-Au system. The large enhancement was shown to arise from a large imaginary component of the DP refractive index and a small real component. Through examination of both the near- and far-field properties of the individual NPs as well as the whole system and examinations of DP-Ag and DP-Au systems, our study provides a new understanding of the couplings between Ag and Au NPs.
    Language English
    Publishing date 2024-04-09
    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 10.1063/5.0196256
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article: An Investigation on the Use of Au@SiO

    Eldridge, Brinton King / Gomrok, Saghar / Barr, James W / Chaffin, Elise Anne / Fielding, Lauren / Sachs, Christian / Stickels, Katie / Williams, Paiton / Wang, Yongmei

    Nanomaterials (Basel, Switzerland)

    2023  Volume 13, Issue 21

    Abstract: Gap-enhanced Raman tags are a new type of optical probe that have wide applications in sensing and detection. A gap-enhanced Raman tag is prepared by embedding Raman molecules inside a gap between two plasmonic metals such as an Au core and Au shell. ... ...

    Abstract Gap-enhanced Raman tags are a new type of optical probe that have wide applications in sensing and detection. A gap-enhanced Raman tag is prepared by embedding Raman molecules inside a gap between two plasmonic metals such as an Au core and Au shell. Even though placing Raman molecules beneath an Au shell seems counter-intuitive, it has been shown that such systems produce a stronger surface-enhanced Raman scattering response due to the strong electric field inside the gap. While the theoretical support of the stronger electric field inside the gap was provided in the literature, a comprehensive understanding of how the electric field inside the gap compares with that of the outer surface of the particle was not readily available. We investigated Au@SiO2@Au nanoparticles with diameters ranging from 35 nm to 70 nm with varying shell (2.5-10 nm) and gap (2.5-15 nm) thicknesses and obtained both far-field and near-field spectra. The extinction spectra from these particles always have two peaks. The low-energy peak redshifts with the decreasing shell thickness. However, when the gap thickness decreases, the low-energy peaks first blueshift and then redshift, producing a C-shape in the peak position. For every system we investigated, the near-field enhancement spectra were stronger inside the gap than on the outer surface of the nanoparticle. We find that a thin shell combined with a thin gap will produce the greatest near-field enhancement inside the gap. Our work fills the knowledge gap between the exciting potential applications of gap-enhanced Raman tags and the fundamental knowledge of enhancement provided by the gap.
    Language English
    Publishing date 2023-11-01
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2662255-5
    ISSN 2079-4991
    ISSN 2079-4991
    DOI 10.3390/nano13212893
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Multiplexed Surface Protein Detection and Cancer Classification Using Gap-Enhanced Magnetic-Plasmonic Core-Shell Raman Nanotags and Machine Learning Algorithm.

    Rodriguez-Nieves, Alberto Luis / Taylor, Mitchell Lee / Wilson, Raymond / Eldridge, Brinton King / Nawalage, Samadhi / Annamer, Assam / Miller, Hailey Grace / Alle, Madhusudhan Reddy / Gomrok, Saghar / Zhang, Dongmao / Wang, Yongmei / Huang, Xiaohua

    ACS applied materials & interfaces

    2024  Volume 16, Issue 2, Page(s) 2041–2057

    Abstract: Cancer is the second leading cause of death attributed to disease worldwide. Current standard detection methods often rely on a single cancer marker, which can lead to inaccurate results, including false negatives, and an inability to detect multiple ... ...

    Abstract Cancer is the second leading cause of death attributed to disease worldwide. Current standard detection methods often rely on a single cancer marker, which can lead to inaccurate results, including false negatives, and an inability to detect multiple cancers simultaneously. Here, we developed a multiplex method that can effectively detect and classify surface proteins associated with three distinct types of breast cancer by utilizing gap-enhanced Raman scattering nanotags and machine learning algorithm. We synthesized anisotropic magnetic core-gold shell gap-enhanced Raman nanotags incorporating three different Raman reporters. These multicolor Raman nanotags were employed to distinguish specific surface protein markers in breast cancer cells. The acquired signals were deconvoluted and analyzed using classical least-squares regression to generate a surface protein profile and characterize the breast cancer cells. Furthermore, computational data obtained via finite-difference time-domain and discrete dipole approximation showed the amplification of the electric fields within the gap region due to plasmonic coupling between the two gold layers. Finally, a random forest classifier achieved an impressive classification and profiling accuracy of 93.9%, enabling effective distinguishing between the three different types of breast cancer cell lines in a mixed solution. With the combination of immunomagnetic multiplex target specificity and separation, gap-enhancement Raman nanotags, and machine learning, our method provides an accurate and integrated platform to profile and classify different cancer cells, giving implications for identification of the origin of circulating tumor cells in the blood system.
    MeSH term(s) Humans ; Female ; Spectrum Analysis, Raman/methods ; Breast Neoplasms/diagnosis ; Gold ; Algorithms ; Membrane Proteins ; Magnetic Phenomena ; Metal Nanoparticles
    Chemical Substances Gold (7440-57-5) ; Membrane Proteins
    Language English
    Publishing date 2024-01-04
    Publishing country United States
    Document type Journal Article
    ISSN 1944-8252
    ISSN (online) 1944-8252
    DOI 10.1021/acsami.3c13921
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article: Insights on the Coupling of Plasmonic Nanoparticles from Near-Field Spectra Determined via Discrete Dipole Approximations

    Barr, James W / Gomrok, Saghar / Chaffin, Elise / Huang, Xiaohua / Wang, Yongmei

    Journal of physical chemistry. 2021 Mar. 02, v. 125, no. 9

    2021  

    Abstract: Coupling between plasmonic nanoparticles (NPs) in NP assemblies has been investigated extensively via far-field properties, such as absorption and scattering, but very rarely via near-field properties, and a quantitative investigation of near-field ... ...

    Abstract Coupling between plasmonic nanoparticles (NPs) in NP assemblies has been investigated extensively via far-field properties, such as absorption and scattering, but very rarely via near-field properties, and a quantitative investigation of near-field properties should provide great insights into the nature of the coupling. We report a numerical procedure to obtain reliable near-field spectra (QNF) around spherical gold NPs (Au NPs) using discrete dipole approximation (DDA). The reliability of the method was tested by comparing QNF from DDA calculations with exact results from the Mie theory. We then applied the method to examine Au NPs assembled in dimers, trimers, and up to pentamers in a linear arrangement. For the well-studied dimer system, we show that the QNF enhancement, due to coupling in longitudinal mode, is much greater than the enhancement in Qₑₓₜ. There is a linear correlation between the QNF and Qₑₓₜ peak positions, with the QNF peak red-shifted from the Qₑₓₜ peak by an average of approximately 12 nm. In the case of the multimers, QNF spectra from individual spheres were not always identical and become dependent on the sphere location. In the longitudinal model, the center sphere has the strongest QNF spectra. For the transverse mode, we differentiate two different scenarios: transverse-Y, where both electric field (E) and light propagation vector (k) are perpendicular to the chain axis, and transverse-X, where k is parallel to the chain axis. In the transverse-Y mode, coupling leads to reduced QNF spectra and the center sphere has the lowest QNF intensity. In the transverse-X mode, there is a retardation effect from the front sphere to the back sphere. The QNF from the front sphere is stronger than from the back sphere. In addition, due to the phase lag in the k-direction, the QNF in transverse-X can differ quite significantly from that in transverse-Y for large particles. These results provide new insights into the coupling properties of Au NPs. Collectively, these results can be understood when one considers how the electric field from induced dipoles on neighboring NPs adds with, or subtracts from, the incident E-field. These results provide new insights into the coupling properties of Au NPs.
    Keywords absorption ; electric field ; models ; nanogold
    Language English
    Dates of publication 2021-0302
    Size p. 5260-5268.
    Publishing place American Chemical Society
    Document type Article
    Note NAL-AP-2-clean
    ISSN 1932-7455
    DOI 10.1021/acs.jpcc.1c01071
    Database NAL-Catalogue (AGRICOLA)

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    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  5. Article: Insight on the Coupling of Plasmonic Nanoparticles from Near-Field Spectra Determined via Discrete Dipole Approximations.

    Barr, James W / Gomrok, Saghar / Chaffin, Elise / Huang, Xiaohua / Wang, Yongmei

    The journal of physical chemistry. C, Nanomaterials and interfaces

    2021  Volume 125, Issue 9, Page(s) 5260–5268

    Abstract: Coupling between plasmonic nanoparticles (NPs) in nanoparticle assemblies has been investigated extensively via far-field properties, such as absorption and scattering, but very rarely via near-field properties, and a quantitative investigation of near- ... ...

    Abstract Coupling between plasmonic nanoparticles (NPs) in nanoparticle assemblies has been investigated extensively via far-field properties, such as absorption and scattering, but very rarely via near-field properties, and a quantitative investigation of near-field properties should provide great insight into the nature of the coupling. We report a numerical procedure to obtain reliable near-field spectra (
    Language English
    Publishing date 2021-03-02
    Publishing country United States
    Document type Journal Article
    ISSN 1932-7447
    ISSN 1932-7447
    DOI 10.1021/acs.jpcc.1c01071
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    Kategorien

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

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