Atomic deuterium (D) adsorption on free-standing nanoporous graphene obtained by ultra-high vacuum D${}_2$ molecular cracking reveals a homogeneous distribution all over the nanoporous graphene sample, as deduced by ultra-high vacuum Raman spectroscopy combined with core-level photoemission spectroscopy. Raman microscopy unveils the presence of bonding distortion, from the signal associated to the planar sp${}^2$ configuration of graphene toward the sp${}^3$ tetrahedral structure of graphane. The establishment of D–C sp${}^3$ hybrid bonds is also clearly determined by high-resolution X-ray photoelectron spectroscopy and spatially correlated to the Auger spectroscopy signal. This work shows that the low-energy molecular cracking of D${}_2$ in an ultra-high vacuum is an efficient strategy for obtaining high-quality semiconducting graphane with homogeneous uptake of deuterium atoms, as confirmed by this combined optical and electronic spectro-microscopy study wholly carried out in ultra-high vacuum conditions.

Free-standing nanoporous graphene was hydrogenated at about 60 at.% H uptake, as determined by the emerging of the sp³ bonding component in the C 1s core level investigated by high-resolution X-ray photoelectron spectroscopy (XPS). Fully unsupported graphane was investigated by XPS under optical excitation at 2.4 eV. At a laser fluence of 1.6 mJ/cm², a partial irreversible dehydrogenation of the graphane was observed, which could be attributed either to the local temperature increase or to a photo-induced softening of the H-to-C stretching mode. The sub-ns dynamics of the energy shift and peak broadening of the C 1s core level revealed two different decay constants: 210 ps and 130 ps, respectively, the former associated with photovoltage dynamics and the latter with thermal heating on a time scale comparable with the synchrotron temporal resolution.

Alkali metal doping of multi-walled carbon nanotubes is of great interest, both fundamentally to explore the effect of dopants on quasi-one-dimensional electrical systems and for energy applications such as alkali metal storage. We present an investigation with complementary photoemission and Raman spectroscopies, fully carried out in an ultra-high vacuum, to unveil the electronic and vibrational response of a forest of highly aligned multi-walled carbon nanotubes by in situ potassium doping. The charge donation by the alkali adatoms induces a plasmon mode, and the density of states undergoes an energy shift consistent with electron donation and band filling of the multi-walled carbon nanotube band structure. The π-states in the valence band and the Raman peaks unveil an evolution that can be ascribed to charge donation and partially to a tensile strain exerted by the K adatoms on the carbon lattice. All these effects are thermally reversible, fostering these materials as a potential system for electronic charge harvesting.