Detection and Characterization of OH Vibrational Modes using High Energy Resolution EELS

The recent detection of vibrational excitations in monochromated electron energy-loss spectroscopy recorded from scanning transmission electron microscopes has opened up new opportunities for nanoscale materials characterization [1]. The enhanced energy resolution has the greatest impact on the low-loss EELS and it is now possible to probe vibrational and electronic excitations at the nanometer level. For example, localized bandgap mapping and detection of interband states is now possible providing a new tool to correlate optical properties with atomic structure [2,3]. Vibrational spectroscopy allows hydrogen containing species to be identified and correlated with materials structure. Detection of water and OH species on nanoparticle surfaces is important for developing a fundamental understanding of solar water splitting catalysts. The delocalized nature of the low-loss spectrum also makes it possible to use the aloof beam spectral acquisition mode (i.e. with the electron probe positioned outside the sample) dramatically reducing electron beam damage. To investigate the feasibility of OH detection, a series of hydroxide and hydrates have been investigated.