Development of Iron-Doped Silicon Nanoparticles As Bimodal Imaging Agents

Abstract

We demonstrate the synthesis of water-soluble allylamine-terminated Fe-doped Si (Si_<i>x</i>Fe) nanoparticles as bimodal agents for optical and magnetic imaging. The preparation involves the synthesis of a single-source iron-containing precursor, Na₄Si₄ with <i>x</i>% Fe (<i>x</i> = 1, 5, 10), and its subsequent reaction with NH₄Br to produce hydrogen-terminated Si_<i>x</i>Fe nanoparticles. The hydrogen-capped nanoparticles are further terminated with allylamine <i>via</i> thermal hydrosilylation. Transmission electron microscopy indicates that the average particle diameter is ∼3.0 ± 1.0 nm. The Si_5Fe nanoparticles show strong photoluminescence quantum yield in water (∼10%) with significant <i>T</i>₂ contrast (<i>r</i>₂<i>/r</i>₁ value of 4.31). Electron paramagnetic resonance and Mössbauer spectroscopies indicate that iron in the nanoparticles is in the +3 oxidation state. Analysis of cytotoxicity using the resazurin assay on HepG2 liver cells indicates that the particles have minimal toxicity