Enhancing the activation of silicon carbide tracer particles for PEPT applications using gas-phase deposition of alumina at room temperature and atmospheric pressure

• We deposited Al2O3 films on SiC particles at ambient conditions in a fluidized bed.
• The affinity of 18F ions towards Al2O3–SiC particle was improved compared to SiC.
• We used the Al2O3–SiC activated particle as tracer in a PEPT experiment.
• Tracer particles have suitable activity for accurate tracking.
• The Al2O3 film is thin enough not to alter the particle size, shape and density.

We have enhanced the radio-activation efficiency of SiC (silicon carbide) particles, which by nature have a poor affinity towards 18F ions, to be employed as tracers in studies using PEPT (Positron Emission Particle Tracking). The resulting SiC–Al2O3 core–shell structure shows a good labelling efficiency, comparable to γ-Al2O3 tracer particles, which are commonly used in PEPT. The coating of the SiC particles was carried at 27±3 °C and 1 bar in a fluidized bed reactor, using trimethylaluminium and water as precursors, by a gas phase technique similar to atomic layer deposition. The thickness of the alumina films, which ranged from 5 to 500 nm, was measured by elemental analysis and confirmed with FIB-TEM (focused ion beam – transmission electron microscope), obtaining consistent results from both techniques. By depositing such a thin film of alumina, properties that influence the hydrodynamic behaviour of the SiC particles, such as size, shape and density, are hardly altered, ensuring that the tracer particle shows the same flow behaviour as the other particles. The paper describes a general method to improve the activation efficiency of materials, which can be applied for the production of tracer particles for many other applications too.