Characterization and Behaviour of Silica Engineered Nanocontainers in Low and High Ionic Strength Media

abstract

Mesoporous silica engineered nanomaterials are of interest to the industry due to their drug-carrier ability. Advances in coating technology include using mesoporous silica nanocontainers (SiNC) loaded with organic molecules as additives in protective coatings. The SiNC loaded with the biocide 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT), i.e., SiNC-DCOIT, is proposed as an additive for antifouling marine paints. As the instability of nanomaterials in ionic-rich media has been reported and related to shifting key properties and its environmental fate, this study aims at understanding the behaviour of SiNC and SiNC-DCOIT in aqueous media with distinct ionic strengths. Both nanomaterials were dispersed in (i) low- (ultrapure water-UP) and (ii) high- ionic strength media-artificial seawater (ASW) and f/2 medium enriched in ASW (f/2 medium). The morphology, size and zeta potential (?P) of both engineering nanomaterials were evaluated at different timepoints and concentrations. Results showed that both nanomaterials were unstable in aqueous suspensions, with the initial ?P values in UP below -30 mV and the particle size varying from 148 to 235 nm and 153 to 173 nm for SiNC and SiNC-DCOIT, respectively. In UP, aggregation occurs over time, regardless of the concentration. Additionally, the formation of larger complexes was associated with modifications in the ?P values towards the threshold of stable nanoparticles. In ASW, SiNC and SiNC-DCOIT formed aggregates (<300 nm) independently of the time or concentration, while larger and heterogeneous nanostructures (>300 nm) were detected in the f/2 medium. The pattern of aggregation detected may increase engineering nanomaterial sedimentation rates and enhance the risks towards dwelling organisms.

keywords

TITANIUM-DIOXIDE NANOPARTICLES; SILVER NANOPARTICLES; TIO2 NANOPARTICLES; SUSPENSION STABILITY; ZINC-OXIDE; AGGREGATION; TOXICITY; NANOCAPSULES; SEAWATER; IMMOBILIZATION

subject category

Chemistry; Science & Technology - Other Topics; Materials Science; Physics

authors

Ferreira, V; Figueiredo, J; Martins, R; Sushkova, A; Maia, F; Calado, R; Tedim, J; Loureiro, S

Groups

G3 - Electrochemical Materials, Interfaces and Coatings

Projects

Towards a new generation of sustainable nano-based additives for maritime anti-corrosion smart coatings: a multidisciplinary framework within the Atlantic (NANOGREEN)

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

acknowledgements

V. Ferreira (PD/BD/52568/2014) and A. Sushkova (2021.07744.BD) benefitted from a Ph.D. grant awarded by the Portuguese Science Foundation (FCT), funded by POPH through QREN and ESF and by national funds (OE). R. Martins is funded by national funds (OE), through FCT (2021.00386.CEECIND). J. Figueiredo was awarded a grant from the research project NANOGREEN (CIRCNA/BRB/0291/2019). We acknowledge the financial support of CESAM (UIDP/50017/2020 + UIDB/50017/2020 + LA/P/0094/2020) and of the CICECO-Aveiro Institute of Materials (UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020), financed by national funds through the FCT/MEC (PIDDAC).