Search for "HOMO–LUMO energy levels" in Full Text gives 2 result(s) in Beilstein Journal of Nanotechnology.
Beilstein J. Nanotechnol. 2018, 9, 721–739, doi:10.3762/bjnano.9.67
Beilstein J. Nanotechnol. 2015, 6, 1107–1115, doi:10.3762/bjnano.6.112