Submicronic Raman and transverse dynamic force microscopy spectroscopies to investigate the physical chemistry of surface nanoheterogeneities
Résumé
On the basis of an experimental example, this paper demonstrates the intrinsic complementary nature between the subwavelength Raman spectroscopy and the tip−sample interaction measurements, in a scanning near field optical microscope device. This paper displays a good illustration of possibilities given by this kind of device to study the interfaces in physical chemistry. The Raman spectra of the optical near field obtained on a lead sulfate sample shows that the surface of this sample is polluted by nanophases of copper sulfate. These impurities, which are not displayed by the usual backscattered far field Raman spectrum recorded in confocal Raman microspectroscopy, are localized at a subwavelength scale and are revealed by a particular behavior in transverse dynamic force (usually noted as shear force) measurements too, in comparison with those obtained over the surface of the lead sulfate sample free from impurities. These differences in probe−sample adhesion throughout a sample are caused by an inhomogeneous distribution of surface water, which is clearly explained by the chemical identification of the nanophases by Raman spectroscopy of the optical near field. The heterogeneous water adsorption at the sample/air interface under a reduced relative humidity is displayed by both the near field optical spectroscopy and the shear force microscopy measurements.
Origine : Fichiers produits par l'(les) auteur(s)
