Quantitative Analysis of Calcium Phosphate Nanocluster Growth Using Time-of-Flight Medium-Energy-Ion-Scattering Spectroscopy

One of the remaining challenges in material chemistry is to unveil the quantitative compositional/structural information and thermodynamic nature of inorganic materials especially in the initial nucleation and growth step. In this report, we adopted newly developed time-of-flight medium-energy-ion-scattering (TOF-MEIS) spectroscopy to address this challenge and explored heterogeneously grown nanometer-sized calcium phosphate as a model system. With TOF-MEIS, we discovered the existence of calcium-rich nanoclusters (Ca/P ∼ 3) in the presence of the non-collagenous-protein-mimicking passivating ligands. Over the reaction, these clusters progressively changed their compositional ratio toward that of a bulk phase (Ca/P ∼ 1.67) with a concurrent increase in their size to ∼2 nm. First-principles studies suggested that the calcium-rich nanoclusters can be stabilized through specific interaction…