Atomic Structure Modulations in Ion-Exchanged Hydroxyapatite Investigated by HRTEM and Single Image Denoising.

Area of Science:

• Materials Science
• Nanotechnology
• Biomaterials

Background:

• Hydroxyapatite (HAP) properties are modulated by ionic substitution, but atomic-scale structural origins are unclear.
• High-resolution transmission electron microscopy (HRTEM) is limited by beam sensitivity in HAP, hindering analysis.
• Low-dose imaging reduces damage but often lacks sufficient contrast for detailed structural insights.

Purpose of the Study:

• To investigate the atomic-scale structural effects of sodium ion (Na+) substitution in HAP.
• To overcome the limitations of beam sensitivity and low contrast in HRTEM analysis of HAP.
• To establish a robust imaging framework for beam-sensitive materials.

Main Methods:

• Developed a novel HRTEM imaging approach combined with single-image deep-learning denoising.
• Utilized low-dose imaging to minimize beam-induced damage to HAP samples.
• Applied denoising algorithms to enhance contrast and enable qualitative and quantitative analysis of atomic arrangements.

Main Results:

• Successfully removed noise from low-dose TEM images of HAP.
• Facilitated detailed analysis of atomic arrangements within Na+-substituted HAP particles.
• Observed that Na+ incorporation induces disordered surface layers in HAP.

Conclusions:

• The developed low-dose HRTEM with deep learning denoising enables atomic-scale structural characterization of beam-sensitive HAP.
• Na+ substitution leads to significant surface layer disorder, offering insights into ion-induced property modulation.
• This approach provides a valuable framework for studying other beam-sensitive materials at the atomic level.