Probing Nanoscale Surface Enhanced Raman Scattering Fluctuation Dynamics using Correlated AFM and Confocal Ultramicroscopy

Journal Article · Wed Oct 01 00:00:00 EDT 2003 · Ultramicroscopy

DOI:https://doi.org/10.1016/S0304-3991(03)00033-0· OSTI ID:15005573

Suh, Yung D; Schenter, Gregory K; Zhu, Leyun; Lu, H PETER

We have studied the laser-excitation-intensity-dependent and Ag-nanocluster interstitial-site-dependent SERS intensity fluctuations under low molecule surface coverage of rhodamine 6G and cytochrome c. a new two-channel photon time-stamping system coupled with atomic force microscopic (AFM), Raman spectroscopic, and imaging microscopy was developed and applied to record Raman intensity fluctuation trajectories at sub-microsecond resolution correlated with in-situ characterization of the nanoparticle clusters. Our experimental results suggest that the nanoconfinement of the local electromagnetic-field enhancement and the interaction of the local field with the molecules, presumably under rotational motions, result in nano-Raman fluctuations. The SERS spectral fluctuation was pertinent to the nanoscale local enhancement and local interaction of the molecules with the surface when the number of molecules to contribute the microscopic Raman signal collected from a diffraction-limited focus spot. The SERS fluctuation dynamics were both photo-induced and spontaneous for rhodamine 6G, but only the photo-induced interstitial sites with heterogeneous geometries. To interpret the observed nano-SERS fluctuation dynamics, we used computer simulation of optical multiple scattering, based on multi-sphere scattering Mie theory, and rotational diffusion of molecules at an interstitial site, based on a random walk in orientation space.

• Research Organization: Pacific Northwest National Lab., Richland, WA (US), Environmental Molecular Sciences Laboratory (US)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 15005573
• Report Number(s): PNNL-SA-36634; ULTRD6; 6506; KC0301020; TRN: US200415%%59
• Journal Information: Ultramicroscopy, Vol. 97, Issue 1-4; Other Information: PBD: 1 Oct 2003; ISSN 0304-3991
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
COMPUTERIZED SIMULATION
CYTOCHROMES
DIFFUSION
FLUCTUATIONS
INTERSTITIALS
MICROSCOPY
MULTIPLE SCATTERING
ORIENTATION
PHOTONS
RESOLUTION
RHODAMINES
SCATTERING
TRAJECTORIES
ENVIRONMENTAL MOLECULAR SCIENCES LABORATORY
AFM
RAMAN
NANOTECHNOLOGY
IMAGING