Changes within the stabilizing layer of ZnO nanoparticles upon washing

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Zinc oxide nanoparticles (ZnO NPs) are crucial for industrial applications.
• Residual chemicals from synthesis must be removed to ensure optimal performance.
• Washing is a key purification step, but its effect on the stabilizing shell is not fully understood.

Purpose of the Study:

• To investigate the impact of antisolvent flocculation and redispersion washing cycles on the acetate ligand shell of ZnO NPs.
• To elucidate the reasons behind the observed optimal zeta potential after one washing cycle.
• To correlate the structural and compositional changes in the NP shell with dispersion stability.

Main Methods:

• Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) were employed.
• Analysis focused on the structure and acetate content of the stabilizing ligand shell.
• Zeta potential measurements were used to assess dispersion stability.

Main Results:

• The first washing cycle increased acetate concentration in the NP shell, forming a denser monolayer.
• A second washing cycle reduced acetate concentration, leading to decreased dispersion stability.
• A third washing cycle resulted in significant agglomeration of the ZnO NPs.

Conclusions:

• The optimal zeta potential after one wash is attributed to a denser, more concentrated acetate monolayer.
• Excessive washing removes essential acetate ligands, compromising NP stability and leading to agglomeration.
• Understanding these effects is critical for controlling ZnO NP properties in industrial applications.