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Discriminating nanoparticle dimers from higher order aggregates through wavelength-dependent SERS orientational
Sarah M Stranahan1, Eric J Titus, Katherine A Willets
1Department of Chemistry and Biochemistry, The University of Texas at Austin, 1 University Station A5300, Austin, Texas 78712, United States.
ACS Nano
|January 26, 2012
Summary
Surface-enhanced Raman scattering (SERS) orientational imaging now distinguishes nanoparticle dimers from larger aggregates by analyzing wavelength-dependent emission patterns. This advanced technique reveals nanoparticle stacking and dye concentration effects on SERS signals.
Area of Science:
- Nanophotonics and Plasmonics
- Spectroscopy
- Materials Science
Background:
- Surface-enhanced Raman scattering (SERS) orientational imaging determines nanoparticle dimer orientations via SERS emission patterns.
- This technique relies on directional polarization along the dimer's longitudinal axis.
Purpose of the Study:
- To extend SERS orientational imaging for discriminating nanoparticle dimers from higher-order aggregates.
- To investigate the influence of aggregate complexity and dye concentration on SERS emission patterns.
Main Methods:
- Observing wavelength dependence of SERS emission patterns to differentiate dimers from aggregates.
- Analyzing lobe positions and definition in SERS emission patterns.
- Investigating SERS emission from trimers at varying dye concentrations.
Main Results:
- Wavelength dependence of SERS emission patterns remains consistent for dimers but varies for higher-order aggregates.
- SERS orientational imaging successfully identified stacked nanoparticles in aggregates.
- Increased dye concentration led to less defined emission pattern lobes in trimers.
- Dynamic fluctuations in emission lobes were observed in low-dye-concentration aggregates.
Conclusions:
- SERS orientational imaging, by analyzing wavelength-dependent patterns, can effectively distinguish nanoparticle dimers from complex aggregates.
- The technique provides insights into nanoparticle arrangement and the impact of molecular labeling on plasmonic signals.
