Determination of silica coating efficiency on metal particles using multiple digestion methods

Area of Science:

• Nanotechnology
• Materials Science
• Environmental Science

Background:

• Nano-sized metal particles pose biotoxicity risks and are prevalent in industrial settings.
• Encapsulating metal particles with amorphous silica shells is a novel approach to mitigate their toxicity.

Purpose of the Study:

• To develop and validate a method for determining silica coating efficiency on metal particles.
• To assess the silica coating efficiency of metal particles produced via gas metal arc welding (GMAW) with tetramethylsilane (TMS).

Main Methods:

• Metal particles with silica coating were synthesized using GMAW with TMS in shielding gas.
• Microwave digestion and Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) were used for metal analysis.
• Three acid mixtures were evaluated for optimal digestion of silica-coated metal particles, with HNO(3)/HF and aqua regia proving most effective.

Main Results:

• The HNO(3)/HF mixture effectively digested silica-coated metal particles, while aqua regia dissolved unencapsulated metals.
• Silica coating efficiencies were calculated based on metal concentrations after sequential digestion.
• Results indicated that 14-39% of welding fume particles were encapsulated with silica coating under tested conditions.

Conclusions:

• A reliable method for quantifying silica coating on metal particles was established.
• The developed method is applicable to assessing silica coverage in other silica shell/metal core nanostructures.
• This research provides a foundation for understanding and controlling silica encapsulation of metal nanoparticles to reduce biotoxicity.