STED nanoscopy – A novel way to image the pore space of geological materials
Résumé
STED nanoscopy (Stimulated Emission Depletion). which can resolve details
far below the diffraction barrier has been applied hitherto preferentially to life
sciences. The method is however also ideal for the investigation of geological
matrices containing transparent minerals, an application tested here, to our
knowledge, for the first time. The measurements on altered granitic rock
and sedimentary clay rock, both containing very fine-grained phases, were
conducted successfully. The STED fluorophore was dissolved in C-14-labelled
methylmethacrylate (C-14-MMA) monomer which was polymerised within
the rock matrix, thereby labelling the pore space in the geomaterials. Double
labelling provided by the C-14-labelled MMA enables autoradiography and
scanning electron microscopy (SEM), providing necessary complementary
information for characterisation and quantification of porosity distributions
and mineral and structure identification. Promising perspectives for further
investigations of geological matrices by using different fluorophores and the
optimisation of measuring procedures or even higher resolution are discussed.
The combination of these different methods enlarges the observation scale of
porosity from nanometre to centimetre scale.