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Saturday, 21 September 2019
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Raw materials & technologies, Technologies, Nanotechnology

Silver nanoparticle movement to the layer surface

Friday, 26 October 2012

Well known as antimicrobial support are silver nanoparticles. The challenge was how to get the most of them to the surface of the layer - where they just can work as antimicrobials. Researchers now found a way to organise the silvermolecules now on the surface.

Getting the silver amount in a composition to the surface keeps the antimicrobial properties

Source: Luftbildfotograf/Fotolia

Getting the silver amount in a composition to the surface keeps the antimicrobial properties

Source: Luftbildfotograf/Fotolia

Joshua A. Orlicki, United States Army Research Laboratory, US and his colleagues have used hyperbranched functionalized polymer additives that automatically migrate to the surface of a polyurethane matrix, bringing with them the silver nanoparticles, which are tied to the hyperbranched polymers by ligand exchange, and thus follow them to the surface.

This generates a seven-fold increase of the concentration of silver nanoparticles at the surface, and the composites retain their antimicrobial properties.

Limited spontanous surface migration

Self-segregating hyperbranched polymer (HBP) additives have been utilized to concentrate silver nanoparticles (AgNPs) at the air interface of polyurethane films. The limited spontaneous surface migration of the AgNPs was enhanced through the addition of appropriately functionalized HBPs.

The researchers employed both amine and thiol terminated additives to allow interaction of the HBP with the nanoparticles. Both types of additives increased surface concentration of silver modestly, though the thiol-terminated HBPs demonstrated nearly a seven-fold enhancement of surface migration.

Wholly-aliphatic HBPs demonstrated only slightly reduced ability to bias AgNP concentration as compared to HBPs functionalized with perfluorinated chains.

6-log reduction of bacteria

In addition, films containing 1 % total silver concentration were tested for antimicrobial activity using the ASTM-E 2180 protocol. Significant reduction of the microorganisms was observed for all samples, 6-log reduction was achieved for the gram-negative bacteria P. aeruginosa, the gram-positive bacteria S. aureus, and the fungi C. albicans.

These findings were published in Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012

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