Toward Nanoscale Chemical Clarity: THz-Pulsed Atom Probe Tomography for Hydrated Biological Materials

Abstract Chemically resolved analysis of fragile biomolecular systems remains challenging because nanoscale spatial information must be obtained without compromising the mass-spectral clarity. Ferritin serves as an effective nanoscale model system featuring an organic protein shell surrounding an Fe-rich mineral core. Here, ferritin-containing hydrated specimens were prepared using graphene encapsulation and analyzed by THz-pulsed atom probe tomography. Compared with conventional laser-pulsing conditions, THz excitation improved peak definition and reduced spectral background, enabling detection of Fe-containing ions and isolation of an Fe-rich cluster consistent with the ferritin core. Although molecular overlaps and low ion counts still limit unambiguous peak assignment, isotopic, spatial, and signal-quality analyses support the identification of an Fe-rich region within an organic environment with further improvements expected at increased electric field strength. These results demonstrate that terahertz-pulsed atom probe tomography substantially improves the chemical readability of hydrated biological materials, opening new perspectives for their nanoscale studies.