Supraparticles with Enhanced Mechanical and Signal Stability for Identification of Objects.

Area of Science:

• Materials Science
• Nanotechnology
• Magnetism

Background:

• Micron-scaled magnetic supraparticles (SPs) from oleic acid-functionalized iron oxide nanoparticles (NPs) are suitable for object tagging via magnetic particle spectroscopy (MPS).
• Mechanical stress during processing can compromise SP integrity and magnetic signal reliability, hindering their application.

Purpose of the Study:

• To investigate the effect of thermal cross-linking of surface-anchored oleic acid ligands on the structural and magnetic properties of iron oxide-based SPs.
• To enhance the mechanical robustness and signal stability of SPs for reliable tagging and tracing applications.

Main Methods:

• Thermal cross-linking of oleic acid ligands on iron oxide NPs within SPs.
• Nanoindentation for mechanical robustness assessment.
• Small-angle X-ray scattering (SAXS) for structural analysis.
• SQUID magnetometry, MPS, and Mössbauer spectroscopy for magnetic characterization.

Main Results:

• Significantly enhanced mechanical robustness and resistance to solvent-driven disintegration of SPs were observed after thermal cross-linking.
• Correlations between nanoscale structural changes (NP distances) and magnetic properties were revealed.
• A chemical spacing strategy was proposed to mitigate NP-NP interactions and maintain magnetic signal stability.

Conclusions:

• Thermal cross-linking of oleic acid ligands provides a chemical strategy to improve the mechanical stability and processability of magnetic SPs.
• This approach ensures stable magnetic signatures crucial for applications like object-embedded tagging and tracing.
• The findings offer fundamental insights for developing robust micrometer-scaled particles with improved performance.