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

Area of Science:

• Materials Chemistry
• Nanomaterials Science
• Biomineralization

Background:

• Understanding inorganic material nucleation and growth is crucial for materials chemistry.
• Quantitative compositional and structural information, along with thermodynamic properties, remain challenging to obtain, especially during initial formation stages.

Purpose of the Study:

• To investigate the initial nucleation and growth steps of heterogeneously grown nanometer-sized calcium phosphate.
• To apply time-of-flight medium-energy-ion-scattering (TOF-MEIS) spectroscopy to characterize these early-stage processes.

Main Methods:

• Utilized newly developed time-of-flight medium-energy-ion-scattering (TOF-MEIS) spectroscopy.
• Studied nanometer-sized calcium phosphate as a model system for heterogeneous growth.
• Employed first-principles studies to investigate stabilization mechanisms.

Main Results:

• Discovered calcium-rich nanoclusters (Ca/P ratio ~3) stabilized by non-collagenous-protein-mimicking passivating ligands.
• Observed a progressive change in cluster composition towards the bulk phase (Ca/P ratio ~1.67) with increasing size (~2 nm).
• First-principles studies confirmed ligand-cluster interactions stabilize the nanoclusters.

Conclusions:

• Passivating ligands play a critical role in stabilizing calcium-rich nanoclusters during calcium phosphate formation.
• Ligand-templated interactions are essential for guiding the chemical and thermodynamic properties of inorganic materials at the nanoscale.
• TOF-MEIS is a powerful tool for elucidating early-stage inorganic material formation processes.