Non-resonant and non-enhanced Raman Correlation Spectroscopy

Abstract

We present the first non-resonant and non-enhanced Raman correlation spectroscopy experiments. They are conducted on a confocal microscope combined with a Raman spectrometer. The thermal fluctuations of the Raman intensities scattered by dispersions of polystyrene particles of sub-micrometric diameters are measured and analysed by deriving the autocorrelation functions (ACFs) of the intensities. We show that for particles of diameter down to 200 nm, RCS measurements are successfully obtained in spite of the absence of any source of amplification of the Raman signal. For particles of diameter ranging from 200 to 750 nm, the ACFs present a time-decay behaviour in accordance with the model of free Brownian particles. For particles of 1000 nm in diameter, the AFCs present a different behaviour with a much smaller characteristic time. This results from the dynamics of a single-Brownian particle trapped in the confocal volume by the optical forces of the focus spot.

SERS Correlation Spectroscopy of Silver Aggregates in Colloidal Suspension: Quantitative Sizing Down to a Single Nanoparticle

“…where k B is the Boltzmann constant, T the temperature, and η the viscosity of the solvent. The temperature T = 24 • C was estimated by calibration measurements 30 while η(T =…”

“…The optical set-up used to record Raman spectra and to perform SERS correlation spectroscopy measurements is detailed in ref. 30 and is sketched in…”

“…However, no convincing 4 in situ sizing and identification of cluster type was achieved. Recently, we have shown 30 that our experimental set-up, specifically optimized for Raman and SERS correlation spectroscopy, possesses a very high sensitivity to realize Raman correlation spectroscopy for signal strengths that are several orders of magnitude weaker than those usually published. Here, we take advantage of this high sensitivity in pushing the precise detection and identification of SERS clusters down to the non-aggregated NPs level, known to produce low SERS activities.…”

Fluorescence-Encoded Infrared Vibrational Spectroscopy with Single-Molecule Sensitivity

“…As an intermediate step toward SM spectroscopy, FEIR-CS has potential as a powerful vibrational probe of chemical processes in solution, just as FCS often plays an auxiliary role to SM fluorescence experiments. While vibrational analogues of FCS using Raman scattering have been implemented previously, to our knowledge FEIR-CS is the first to be sensitive enough for use with single molecules. − Changes in vibrational frequencies due to chemical interconversion or specific molecular interactions in an equilibrium state could be sensed as FEIR signal fluctuations and monitored via the correlation function. Fourier transform excitation with the IR pulse pair suggests the possibility of more sophisticated frequency-resolved FEIR-CS experiments, similar in concept to photon correlation Fourier spectroscopy, , which could track microsecond spectral diffusion processes.…”

In Situ Identification of Spherical Ag Monomers and Dimers at Zeptomole Adsorbate Concentrations by Surface-Enhanced Raman Scattering Correlation Spectroscopy

“…⟨ N ⟩, A R , and β are also adjusted, whereas the values of the modulus of the scattering vector q and that of w = 40 are fixed and given by the experimental setup. 19 Importantly, using our experimental setup, DLS, and latter SERS-CS, measurements are always analyzed from the measured intensities. The values obtained for the hydrodynamic radii must therefore be compared to those obtained from the intensity size distribution of the commercial DLS apparatus.…”