Comment on “Engineering Shape Anisotropy of Fe₃O₄-γ-Fe₂O₃ Hollow Nanoparticles for Magnetic Hyperthermia”

In a recent paper, the authors presented their investigation involving engineering shape anisotropy of Fe3O4-γ-Fe2O3 hollow nanoparticles for magnetic hyperthermia; however, a significant part of the study involving Mössbauer spectroscopy is erroneous. During analysis of the room temperature Mössbauer spectra for these samples, the investigators included two additional sextets for γ-Fe2O3 (maghemite). This is not acceptable considering that the sextets arising from ferric ions of both the octahedral and tetrahedral sites of maghemite largely overlap at room temperature and are inseparable because of poor resolution. We suggest a methodology for analyzing these spectra, and accordingly corrections are warranted in Figure 4 and Tables S3 and S4 and within the main text.