Direct quantification of hydrophobicity: a case study of environmentally relevant silver nanoparticles

Among the physical and chemical properties of nanomaterials, hydrophobicity is recognized to play a key role in their environmental impact. This parameter is involved in abiotic and biotic processes and could be used in the prediction of nanoparticles’ (NPs’) behaviour in the environment, in terms of aggregation, toxicity and, bioaccumulation. Through a dark field microscopy (DFM)-based method, this paper characterized the change in hydrophobicity of silver (Ag) NPs induced by sulfidation and by the formation of a corona of natural organic matter (NOM). DFM results measured as a Hydrophobicity index (Hy) were compared with the dye adsorption method results (log HR). The sulfidation of the AgNPs and/or the adsorbed NOM/ “Lipid-free” (LF-)NOM increased their own hydrophobicity, increasing the Hy values. The tendency of sulfidized AgNPs to become more hydrophobic is demonstrated by both methods. Log HR results were not able to differentiate the hydrophobicity of AgNPs with varying natural organic matter (NOM) coronas. This study shows that the DFM-based method, thanks to its ability to differentiate NPs with different degrees of hydrophobicity, can effectively measure the hydrophobicity of environmentally relevant NPs and is robust with a potential to be widely used in the future.

RONCARI Francesco;  CORDERO Salimar;  DESMET Cloe;  COLPO Pascal;  LAU Boris;  VALSESIA Andrea; 

2023-10-09

Frontiers Media S.A.

JRC132172

2673-3013 (online),   

https://www.frontiersin.org/articles/10.3389/fnano.2023.1271009,    https://publications.jrc.ec.europa.eu/repository/handle/JRC132172,   

10.3389/fnano.2023.1271009 (online),