Nanometer-Scale Surface Structure and Sterilization Characteristics of Na/Ag Ion-Exchanged Glass for Anti-Biofouling Application.

Abstract

Most objects and structures exposed to a marine environment for more than a month undergo biofouling of the surface. Biofouling is a phenomenon in which micro-organisms attach to marine structures and may result in deterioration of the structure or breakage of the structure due to weight gain. In this study, glass, which can inhibit biofouling of marine structures, was prepared and its germicidal properties were analyzed. For this purpose, Ag ions were implanted into soda-lime-silicate glass by the ion-exchange method. For the glass immersed in seawater, the bactericidal effect of the glass specimen was than evaluated by inoculating the strain and counting the number of viable cells after 12 or 24 h. Experimental variables were ion exchange conditions, time immersed in seawater, and time spent inoculating the strain. In particular, the surface state of the ion exchange glass before and after immersion in seawater was observed at the nanometer level, and the elution amount of Ag ions with time was measured by the ICP mass analysis method. As the ion exchange time increased, the amount of ion exchange increased. The amount of ions was consistent with Fick's first law, which is proportional to the square root of time. When ion-exchanged specimens were immersed in seawater, the amount of Ag ions eluted was on the order of ppm. Si and Na ions were also eluted from the glass. As the ion exchange time increased, crystals of 60~80 nm, which are presumed to be Na₂CO₃ phase, formed densely on the surface of the specimen. However, when the glass specimens were immersed in seawater, crystals formed on the surface dissolved and disappeared. Cracks subsequently formed on the surface and finally the surface collapsed. After 30 days, a fresh glass surface appeared again. This is a very interesting result because it shows that the reaction between glass and seawater is very similar to that between aqueous solutions. When the glass implanted with Ag ions is immersed in seawater, the surface dissolves and the glass-network-structure collapses, resulting in considerable Ag ion elution, which enhances bactericidal action in seawater. For example, when a specimen immersed in seawater for 30 days was inoculated with the strain for 24 hours, the number of strains decreased from 2.1 × 106 cells/ml to 0 cell/ml, indicating 100% disinfection ability. In this study, soda-lime-silicate glass with Ag ion implantation by the Na/Ag ion exchange method showed an excellent germicidal effect when in contact with sea water. From this result, it can be expected that long-term marine biological pollution can be suppressed by applying the glass developed in this research to marine structures.