Controlled evaluation of silver nanoparticle dissolution using atomic force microscopy.

Area of Science:

• Environmental Science
• Nanotechnology
• Materials Science

Background:

• Silver nanoparticles (AgNPs) are increasingly used in consumer products, raising concerns about their environmental release and impact.
• AgNP dissolution is a key transformation process in natural waters, but aggregation complicates kinetic studies.
• Understanding AgNP dissolution is crucial for assessing their ecological risks.

Purpose of the Study:

• To investigate the dissolution kinetics of immobilized silver nanoparticles (AgNPs) without aggregation.
• To evaluate the effect of varying sodium chloride (NaCl) concentrations on AgNP dissolution.
• To demonstrate a method for studying AgNP dissolution using nanosphere lithography (NSL) and atomic force microscopy (AFM).

Main Methods:

• Fabrication of uniform, immobilized AgNP arrays on glass substrates using nanosphere lithography (NSL).
• Controlled dissolution experiments in phosphate buffer (pH 7.0, 25 °C) with variable NaCl concentrations.
• Monitoring of AgNP morphology and dissolution using atomic force microscopy (AFM).

Main Results:

• Immobilized AgNPs showed shape changes (triangular to circular) and increased height in the first day of exposure to ≥10 mM NaCl.
• Particle height and radius decreased at a constant rate over two weeks.
• Dissolution rates increased linearly with NaCl concentration, ranging from 0.4 to 2.2 nm/d across the tested concentration range (10-550 mM).

Conclusions:

• NaCl concentration significantly influences AgNP dissolution rates, suggesting a catalytic role in saline environments.
• The study highlights the utility of NSL and AFM for direct, aggregation-free investigation of AgNP dissolution.
• Findings are important for predicting the environmental fate and behavior of silver nanoparticles in saline waters and biological systems.