Antimicrobial finishing of textiles intended for food processing industry by plasma enhanced chemical vapor deposition - physical vapor deposition of Ag-SiOCH composites coated with AlxOy or SiOCH encapsulation layers

In previous work, textiles for the food processing industry were coated with an original deposition technique based on a combination of plasma-enhanced chemical vapor deposition and physical vapor deposition to obtain ~ 10 nm size silver clusters incorporated into a SiOCH matrix (Ag-SiOCH coating). However, the stability of the coating in end-use conditions (abrasion during washing cycles and/or oxidation) is questionable and this work is specifically devoted to study the effect on antimicrobial activity of Ag-SiOCH coatings after deposition of high porosity and low density protective layers. The Ag-SiOCH coating was thus covered with encapsulation layers (either hydrophobic SiOCH or hydrophilic AlxOy). The surface and bulk characterisation results of the multilayer coatings using X-ray Photoelectron Spectroscopy (XPS), Dynamic Secondary Ion Mass Spectrometry (DSIMS) and Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) were used to study the composition of the coating and quantify the presence of the antimicrobial agent (Ag) at the surface and inside of the coating. Antibacterial tests indicated that antimicrobial activity of coated textiles was maintained. However, the antimicrobial activity was not directly correlated with the Ag content detected at the top surface or with the distance from the top surface to the part of the coating containing a significant amount of silver (as detected by XPS) and diffusion mechanisms during antibacterial tests could play a significant role. In particular, the hydrophilic character of AlxOy deposit likely allowed a better availability of the antimicrobial agent (Ag) but it was also observed for SiOCH hydrophobic deposits.