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Issue 33, 2015
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Surface- and tip-enhanced resonant Raman scattering from CdSe nanocrystals

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Abstract

Surface- and tip-enhanced resonant Raman scattering (resonant SERS and TERS) by optical phonons in a monolayer of CdSe quantum dots (QDs) is demonstrated. The SERS enhancement was achieved by employing plasmonically active substrates consisting of gold arrays with varying nanocluster diameters prepared by electron-beam lithography. The magnitude of the SERS enhancement depends on the localized surface plasmon resonance (LSPR) energy, which is determined by the structural parameters. The LSPR positions as a function of nanocluster diameter were experimentally determined from spectroscopic micro-ellipsometry, and compared to numerical simulations showing good qualitative agreement. The monolayer of CdSe QDs was deposited by the Langmuir–Blodgett-based technique on the SERS substrates. By tuning the excitation energy close to the band gap of the CdSe QDs and to the LSPR energy, resonant SERS by longitudinal optical (LO) phonons of CdSe QDs was realized. A SERS enhancement factor of 2 × 103 was achieved. This allowed the detection of higher order LO modes of CdSe QDs, evidencing the high crystalline quality of QDs. The dependence of LO phonon mode intensity on the size of Au nanoclusters reveals a resonant character, suggesting that the electromagnetic mechanism of the SERS enhancement is dominant. Finally, the resonant TERS spectrum from CdSe QDs was obtained using electrochemically etched gold tips providing an enhancement on the order of 104. This is an important step towards the detection of the phonon spectrum from a single QD.

Graphical abstract: Surface- and tip-enhanced resonant Raman scattering from CdSe nanocrystals

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Publication details

The article was received on 03 Nov 2014, accepted on 22 Dec 2014 and first published on 22 Dec 2014


Article type: Paper
DOI: 10.1039/C4CP05087H
Citation: Phys. Chem. Chem. Phys., 2015,17, 21198-21203
  • Open access: Creative Commons BY license
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    Surface- and tip-enhanced resonant Raman scattering from CdSe nanocrystals

    E. Sheremet, A. G. Milekhin, R. D. Rodriguez, T. Weiss, M. Nesterov, E. E. Rodyakina, O. D. Gordan, L. L. Sveshnikova, T. A. Duda, V. A. Gridchin, V. M. Dzhagan, M. Hietschold and D. R. T. Zahn, Phys. Chem. Chem. Phys., 2015, 17, 21198
    DOI: 10.1039/C4CP05087H

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