Abstract: The present disclosure describes a matrix-free nanostructured substrate for use in mass spectrometry. The substrate may preferably include one or more localized analyte spots for placement of an analyte, where each analyte spot may comprise a nanostructured metal oxide or semiconductor containing nanotubes or nanopores. The substrate may further include unstructured metal, metal oxide, or semiconductor that is not nanotubular or nanoporous in the part of the substrate that surrounds each of the analyte spots. In some embodiments, the nanostructured metal oxide or semiconductor may be chemically or structurally modified, and the analyte spots may additionally or alternatively include secondary nanostructures such as nanorods, nanoparticles, nanocoatings, or nanotubes. This may facilitate energy transfer to the analyte for matrix-free laser desorption/ionization.