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Absorption Spectroscopy of Single Optically Trapped Gold Nanorods
Zhongming Li1, Weizhi Mao1, Mary Sajini Devadas1
1Department of Chemistry and Biochemistry, University of Notre Dame , 251 Nieuwland Science Hall, Notre Dame, Indiana 46556-5670, United States.
Nano Letters
|October 27, 2015
Summary
Surfactant coatings on gold nanorods significantly broaden their light absorption spectra due to electron scattering. Removing surfactant is crucial for enhancing their performance in sensing applications.
Area of Science:
- Nanophotonics
- Plasmonics
- Materials Science
Background:
- Single gold nanorods exhibit localized surface plasmon resonance (LSPR), a phenomenon sensitive to their dimensions and environment.
- Understanding factors influencing LSPR line width is critical for optimizing nanorod applications.
Purpose of the Study:
- To quantify the electron-surface scattering contribution to the LSPR line width of single gold nanorods.
- To investigate the impact of surfactant coatings on LSPR line width and particle-to-particle variations.
- To assess the implications of these findings for sensing applications.
Main Methods:
- Optical trapping of single gold nanorods in water.
- Spatial modulation spectroscopy for measuring extinction spectra.
- Finite element calculations for determining nanorod dimensions and radiation damping.
- Analysis of LSPR line width to isolate electron-surface scattering effects.
Main Results:
- Surfactant coatings cause significant electron-surface scattering, broadening the LSPR line width.
- Particle-to-particle variations in scattering effects were observed and found to be substantial.
- Electron-surface scattering contributions were more pronounced than in previous studies of substrate-supported particles.
- Measured line widths for coated nanorods were only slightly narrower than ensemble spectra.
Conclusions:
- Surfactant coatings introduce significant scattering losses, negatively impacting nanorod optical properties.
- The presence of surfactant is a major factor contributing to line width broadening in single gold nanorods.
- Removing surfactant is essential for maximizing the sensitivity and performance of gold nanorods in sensing applications.
