Nanoscale C–H/C–D mapping of organic materials using electron spectroscopy

Abstract

Atomic-scale imaging and spectroscopy are essential for distinguishing hydrogen from deuterium, crucial in identifying structures and properties of organic materials with designed isotopic functionalities. However, conventional structural analysis techniques for materials containing both isotopes, likeneutron scattering, provide only averaged information across the beam area. In our study, we utilized vibrational spectroscopy with a monochromated transmission electron microscope, achievingdiscrete imaging of hydrogen and deuterium in organic polymers at single-nanometre resolution. This method's key advantage lies in its capability to distinguish between carbon-hydrogen (C–H) and carbon-deuterium (C–D) stretches by detecting slight differences in vibrational energy. The technique allowed for C–H/C–D mapping, which uncovered surface segregation of the deuterated polystyrene (dPS) component within a block copolymer film composed of dPS and poly(2-vinylpyridine). Moreover, it enabled the clear visualization of the spatial distribution of hydrogenated and deuterated polystyrene (hPS and dPS) on a molecular scale in a bulk block copolymer specimen containing both components.