The Hidden Cost of Two-Dimensional TEM Reconstruction of Magnetic Nanoparticle Morphology

Iago López-Vázquez; Amira Páez; Yilian Fernández-Afonso; Roy W. Chantrell; Thomas S. van Zanten; Sergiu Ruta; Lucía Gutiérrez; Òscar Iglesias; David Serantes

arXiv · 2610.04713

The Hidden Cost of Two-Dimensional TEM Reconstruction of Magnetic Nanoparticle Morphology

Iago López-Vázquez·Amira Páez·Yilian Fernández-Afonso·Roy W. Chantrell·Thomas S. van Zanten·Sergiu Ruta·Lucía Gutiérrez·Òscar Iglesias·David Serantes

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Abstract

Conventional transmission electron microscopy (TEM) records two-dimensional (2D) projections of three-dimensional (3D) objects, complicating the inference of nanoparticle morphology. This limitation is investigated for quasi-spherical iron oxide nanoparticles (IONPs) imaged after deposition on a TEM grid and after cellular internalization and immobilization in resin. A statistical inverse-reconstruction method is developed in which synthetic 3D particle populations are randomly oriented, projected onto a TEM-like plane, and compared with the experimental equivalent-diameter and axial-ratio distributions. Models of increasing geometrical complexity are considered, from monodisperse prolate spheroids to size- and shape-polydisperse prolate populations and triaxial ellipsoids. Size polydispersity is required to reproduce the projected equivalent-diameter distribution, whereas relaxing axial symmetry through a triaxial description enables simultaneous reproduction of the size and axial-ratio distributions. The inferred population represents a statistically compatible 3D morphology rather than a unique particle-by-particle reconstruction. Its physical relevance is assessed through a macrospin model incorporating the corresponding shape-anisotropy contributions. Application to magnetic fluid hyperthermia reveals a pronounced sensitivity of the predicted heating response to particle geometry and polydispersity. The approach provides a general framework for connecting conventional TEM measurements with morphology-dependent properties of nanoparticle ensembles.

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Iago López-Vázquez, Amira Páez, Yilian Fernández-Afonso, Roy W. Chantrell, Thomas S. van Zanten, Sergiu Ruta, Lucía Gutiérrez, Òscar Iglesias, David Serantes. 2026-10-03. The Hidden Cost of Two-Dimensional TEM Reconstruction of Magnetic Nanoparticle Morphology. https://arxiv.org/abs/2610.04713

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