Laser intensity limits in surface‐enhanced linear and nonlinear Raman micro‐spectroscopy of organic molecule/Au‐nanoparticle conjugates

Abstract

Laser light, illuminating surface‐enhanced Raman scattering‐active nanostructured CeO2/Al/Al2O3 thin‐film samples with reporter molecules/Au nanoparticle conjugates on the CeO2 surface, may cause irreversible modifications of the conjugates and of the surface structure field‐enhancing properties. As a result, the observed Raman signal decreases or vanishes. The limits of the laser light intensity suitable for nondestructive spectroscopic studies have been assessed using continuous and quasi‐continuous wave (mode‐locked ps‐pulse) laser radiation at different wavelengths. This radiation was used as a pump for linear and nonlinear Raman microspectroscopy of reporter molecules adsorbed on the surface of such a plasmonic metamaterial. Reducing laser power below certain levels allowed reproducible mapping of surface‐enhanced Raman scattering and surface‐enhanced coherent anti‐Stokes Raman scattering signal strengths at the reporter molecule Raman shifts.

Plasmon resonance, thermal, and optical contributions to anti‐Stokes‐to‐Stokes line strength ratios in continuous wave‐excited surface‐enhanced Raman scattering spectra of molecules at random Ag surface

“…Figure 5 presents a few spectra, recorded at these different but low excitation intensities, at which the spectral profiles are still well reproducible. [ 29 ] The 650‐cm −1 gap observed in the center of the spectra is due to the notch‐filter installed. To verify the reproducibility while increasing the laser intensity, the spectra were repeatedly recorded at reduced intensities to ensure that the obtained spectrum resembles the one recorded earlier at the same intensity in both the spectral profile and TNB peak amplitudes.…”

“…Moreover, the photostability of the samples plays an important role during the recording of SERS spectra, because at higher power densities, their irreversible modifications occur. [ 28,29 ]…”

Micro Raman spectroscopy for NETosis detection

“…[38] For CARS measurements, we exploit a picosecond tunable laser described in details elsewhere. [39] For spontaneous Raman measurements, the excitation wavelengths of 633 and 532 nm were provided by a He─Ne laser (Melles Griot 05-LHP-991) and a diode laser with an adjustable output power (model SLM-417-20), respectively. The laser power at the sample was controlled by a variable neutral filter with the 0-3 optical density.…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XIV

“…They found that this enhancement exhibits a strong dependence on gap width and is the basis of SERS or tip‐enhanced Raman scattering. Fabelinsky et al [ 30 ] studied the laser intensity limits in surface‐enhanced linear and nonlinear Raman microspectroscopy of organic molecule/Au‐nanoparticle conjugates. The limits of laser light intensity suitable for nondestructive spectroscopic studies were assessed using continuous and quasi‐continuous wave (mode‐locked ps‐pulse) laser radiation at different wavelengths.…”