Atom Probe Tomography of Encapsulated Hydroxyapatite Nanoparticles.

Area of Science:

• Materials Science
• Nanotechnology
• Biomaterials

Background:

• Hydroxyapatite nanoparticles (HAP NPs) possess diverse applications in medicine, bioengineering, catalysis, and water treatment.
• Understanding the atomic distribution within HAP NPs is crucial for elucidating their properties, but current characterization methods are limited.
• Atom probe tomography (APT) offers high spatial resolution and chemical sensitivity but faces challenges in sample preparation for HAP NPs.

Purpose of the Study:

• To develop and evaluate techniques for preparing hydroxyapatite nanoparticles (HAP NPs) for atom probe tomography (APT) analysis.
• To overcome the challenges associated with creating needle-shaped samples required for APT characterization of HAP NPs.
• To enable detailed nanoscale spatiochemical analysis of HAP NPs.

Main Methods:

• Development of two distinct encapsulation techniques for HAP NPs prior to APT analysis.
• Sputter-coating HAP NPs with gold for encapsulation and subsequent voltage-pulsing APT.
• Atomic layer deposition of alumina for encapsulating HAP NPs followed by laser-pulsing APT.

Main Results:

• Successful characterization of partially fluoridated HAP NPs using both developed encapsulation techniques with APT.
• Identification of significant tradeoffs between different encapsulant methods and materials for HAP NP characterization.
• Demonstration that both voltage- and laser-pulsing APT can be employed with appropriate sample preparation.

Conclusions:

• The developed encapsulation techniques provide a pathway for advanced nanoscale characterization of HAP NPs.
• Selection of the optimal encapsulation strategy depends on specific experimental needs and requires further technique development.
• This work lays the foundation for deeper insights into the nanoscale spatiochemistry and properties of HAP NPs.