Silver nanoparticles (Ag-NPs) adhered/inserted on textile fibers have an effective antimicrobial role. However, their release due to low adherence and their fate in the natural settings have been questioned in terms of toxicity level. In order to overcome this recurrent problem of adherence, the in situ formation of Ag-NPs in five textile fibers (cotton (untreated and chemically bleached), sheep's wool, polyamide, and polyester) was assessed. Herein, the fibers were first immersed in a silver ion solution (1 g/L of AgNO₃) for ion saturation at room T for 24 h followed by draining fibers and their reimmersion this time in a strong chemical reducing solution (0.25 g/L of NaBH₄) at room T for 24 h. This latter step leads to the in situ formation of Ag-NPs where size (5 nm < size < 50 nm), surface covering concentration, and aggregation degree depend on the textile fiber kind as deduced from FESEM images. This simple lab chemical method allows instantaneous in situ formation of Ag-NPs onto fibers without the requirement of additional thermal treatment. Moreover, for natural fibers, the formation of Ag-NPs inside of them is also expected as confirmed from FESEM images in cotton cross sections. In complement, all textile fibers containing Ag-NPs (sheep's wool 10 mg/g > untreated cotton 2.3 mg/g > bleached cotton 1 mg/g > polyamide 0.62 mg/g > polyester 0.28 mg/g) were submitted to interact with strong oxidants in an aqueous media (7.5% v/v of H₂O₂, 0.5 and 0.05 M of HNO₃ and ultrapure water as the control) using flow-through reactor experiments. Here, breakthrough curves reveal that the oxidative dissolution rate (given in mol/g min) of adhered Ag-NPs (ionic release) depends strongly on fiber nature, and nature and concentration of oxidant solution. In summary, this fundamental study suggests that Ag-NPs may be successfully adhered/inserted in natural fibers (wool and cotton) in a safety-design perspective with performant biocide properties as confirmed by using Bacillus subtilis.

Mahaut Di Girolamo

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