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Dispersion Stability of MWCNTs Decorated with Ag Nanoparticles through Pulse Reversed Current Electrodeposition Using a Deep Eutectic Solvent
1 , 2 , 1 , 1 , 2, 3 , * 1 , 2, 4
1  CIQUP - Faculty of Sciences University of Porto
2  Center for Surface Science and Nanotechnology, University Polytechnica of Bucharest
3  OLV Development SRL, Brasoveni 3, 023613 Bucharest, Romania
4  Academy of Romanian Scientists, Splaiul Independentei 54, 050094, Bucharest, Romania
Academic Editor: Antonio Di Bartolomeo


Carbon nanotubes (CNTs) represent a unique class of nanomaterials with remarkable applications in diverse domains. However, one of the many challenges still requiring improvements is undoubtedly their dispersion stability. The control of the dispersion stability of CNTs is still a challenge due to the strong of van der Waals forces that lead to their aggregation.
Metallic nanoparticles, such as silver (AgNPs), with the presence of a capping agent, e.g. PVP, are recognized as having an important role in the increase of the stability of nanoparticle dispersions, and if incorporated in the multi-walled carbon nanotubes (MWCNTs), may help surpass the MWCNTs aggregation problem.
The present work reports the enhancement of the stability of MWCNTs upon decoration by AgNPs, using an electrochemical method to generate the silver ions and promote the electro-deposition of silver.
To validate the increase in stability of the Ag decorated MWCNTs, two solvents were used in this study, water and glyceline, a eutectic mixture of choline chloride and glycerol.
The time stability of bare MWCNTs and AgMWCNTs nanofluids were characterized through DLS and UV-Vis.
Compared to commercial MWCNTs, MWCNTs decorated with AgNPs presented a significant stability enhancement, in both water and glyceline. Glyceline also presented a higher stability over time, with a retention of the UV-Vis absorbance up to 97%, compared to 50% for water media. The DLS analysis showed a standard deviation minimum value of ~7 nm, in glyceline, and ~50 nm, in water. In both cases, the use of AgMWCNTs materials improved the stability of the dispersions 25x in glyceline and 2.5x in water, when compared to the stability of bare MWCNTs dispersions.

Keywords: stability; multi-walled carbon nanotubes; silver nanoparticles; pulse-reverse electrodeposition; deep eutectic solvent; electrochemical synthesis.