# Controlled Synthesis of a New Class of Heterostructured Metal Oxides (Cerium, Thorium, Uranium)/Calcium Fluoride Core‐Shell Nanocrystals With Atomically Coherent Interfaces

## TL;DR

Scientists created new metal oxide and calcium fluoride nanocrystals with precise control over their structure, aiming to use them for targeted cancer therapy with alpha particles.

## Contribution

The synthesis of a new class of MO2/CaF2 core-shell nanocrystals with atomically coherent interfaces in cerium and actinide systems is reported for the first time.

## Key findings

- High-quality single-crystalline core-shell nanocrystals with metal oxide (Ce, Th, U) and calcium fluoride domains were successfully synthesized.
- The interface between oxide and fluoride domains is structurally coherent but chemically complex, an unprecedented observation in cerium and actinide nanochemistry.
- These nanocrystals are designed for future use in targeted alpha therapy with radionuclides like 227Th or 230U.

## Abstract

Heterostructured nanocrystals (NCs) integrating chemically and/or structurally distinct materials are of significant interest due to their potential to exhibit multiple functionalities or unconventional properties. However, the development of such materials remains limited, primarily due to crystallographic incompatibilities and synthesis challenges. Here, we report the synthesis and structural characterization of a new class of metal oxide‐based (Ce, Th, or U) heterostructures with calcium fluoride featuring core‐shell architectures with precise control over both morphology and shell thickness. Powder x‐ray diffraction (PXRD) and high‐resolution scanning/transmission electron microscopy techniques confirm the formation of high‐quality single‐crystalline particles coupling metal oxide (Ce, Th, or U) and calcium fluoride domains through a structurally coherent but chemically complex intermixed oxide‐fluoride interface—an unprecedented observation in cerium and actinide nanochemistry. These novel materials have been designed to anticipate their future doping with therapeutic alpha particle‐emitting radionuclides (α‐emitters) such as 227Th or 230U for locoregional targeted alpha therapy (TAT). It is anticipated that the reported heterostructured core‐shell NCs will offer a promising platform for preclinical investigations to determine the full potential and interest of inorganic core‐shell NCs, especially CeO2 / CaF2, for TAT application.

Precisely engineered heterostructured metal oxide‐based MO2 / CaF2 (M = Ce, Th, U) core‐shell nanocrystals are synthesized with atomic‐level control over size, shell thickness, and interface coherence, expanding heterostructure design principles to cerium oxide and actinide oxide systems for the first time.