An Investigation on the Use of Au@SiO@Au Nanomatryoshkas as Gap-Enhanced Raman Tags

Authors

Brinton King Eldridge, Department of Chemistry, University of Memphis, Memphis, TN 38152, USA.
Saghar Gomrok, Department of Chemistry, University of Memphis, Memphis, TN 38152, USA.
James W. Barr, Department of Biological, Physical, and Human Sciences, Freed-Hardeman University, Henderson, TN 38340, USA.
Elise Anne Chaffin, Department of Biological, Physical, and Human Sciences, Freed-Hardeman University, Henderson, TN 38340, USA.
Lauren Fielding, Department of Biological, Physical, and Human Sciences, Freed-Hardeman University, Henderson, TN 38340, USA.
Christian Sachs, Department of Biological, Physical, and Human Sciences, Freed-Hardeman University, Henderson, TN 38340, USA.
Katie Stickels, Department of Biological, Physical, and Human Sciences, Freed-Hardeman University, Henderson, TN 38340, USA.
Paiton Williams, Department of Biological, Physical, and Human Sciences, Freed-Hardeman University, Henderson, TN 38340, USA.
Yongmei Wang, Department of Chemistry, University of Memphis, Memphis, TN 38152, USA.

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.

Publication Title

Nanomaterials (Basel, Switzerland)

Recommended Citation

Eldridge, B. K., Gomrok, S., Barr, J. W., Chaffin, E. A., Fielding, L., Sachs, C., Stickels, K., Williams, P., & Wang, Y. (2023). An Investigation on the Use of Au@SiO@Au Nanomatryoshkas as Gap-Enhanced Raman Tags. Nanomaterials (Basel, Switzerland), 13 (21) https://doi.org/10.3390/nano13212893