Calculation of nanoparticle size distribution of some nanosystems based on electron paramagnetic resonance line shape analysis

In this study, boron carbide (B₄C) nanoparticles of two different particle sizes (25 µm and 150 µm) were irradiated using gamma rays. Following the irradiation process, Electron Paramagnetic Resonance (EPR) spectra of the powdered samples were obtained and analyzed. The spectra were simulated to identify the radical species formed as a result of the irradiation. The spectroscopic g-values of the radicals detected in the boron carbide structures were calculated as g = 2.0021 for the 25 µm particles and g = 2.0023 for the 150 µm particles. The hyperfine interaction constants were determined as a₁α = 1.82 mT, a₂α = 2.08 mT, and a₃α = 0.82 mT for the 25 µm sample; and a₁α = 1.84 mT, a₂α = 2.13 mT, and a₃α = 0.80 mT for the 150 µm sample. These results indicate that, in the evaluation of particle size distribution based on EPR spectroscopy, the EPR line shape or resonance signal intensity can serve as a critical parameter.