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. 2009 Sep 2;131(34):12032-3.
doi: 10.1021/ja903321z.

Demonstration of surface-enhanced Raman scattering by tunable, plasmonic gallium nanoparticles

Pae C Wu  1 , Christopher G Khoury, Tong-Ho Kim, Yang Yang, Maria Losurdo, Giuseppe V Bianco, Tuan Vo-Dinh, April S Brown, Henry O Everitt
Affiliations

Demonstration of surface-enhanced Raman scattering by tunable, plasmonic gallium nanoparticles

Pae C Wu et al. J Am Chem Soc. .

Abstract

Size-controlled gallium nanoparticles deposited on sapphire were explored as alternative substrates to enhance Raman spectral signatures. Gallium's resilience following oxidation is inherently advantageous in comparison with silver for practical ex vacuo nonsolution applications. Ga nanoparticles were grown using a simple molecular beam epitaxy-based fabrication protocol, and monitoring their corresponding surface plasmon resonance energy through in situ spectroscopic ellipsometry allowed the nanoparticles to be easily controlled for size. The Raman spectra obtained from cresyl fast violet (CFV) deposited on substrates with differing mean nanoparticle sizes represent the first demonstration of enhanced Raman signals from reproducibly tunable self-assembled Ga nanoparticles. Nonoptimized aggregate enhancement factors of approximately 80 were observed from the substrate with the smallest Ga nanoparticles for CFV dye solutions down to a dilution of 10 ppm.

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Figures

Figure 1
Figure 1
(a) Pseudoextinction spectra obtained by in situ spectroscopic ellipsometry corresponding to three Ga NP on sapphire samples. The SEM image (inset) and accompanying NP diameter distribution histogram (b) correspond to the 2.9eV SPR sample (curve (i) in (a)).
Figure 2
Figure 2
High resolution Raman spectra for the strongest CFV mode at 590cm−1 for Ga NPs with SPR at 2.9eV (solid) compared to the same CFV mode on bare sapphire (dotted). Decreasing CFV concentration in ethanol exhibits a linear correlation between CFV concentration and the Raman intensity. Calibration error bars, determined by the standard deviation of five measurement locations, range from 4–20%, quite small even at the largest concentrations, indicating reproducibility (inset).
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