Silver has a wide range of industrial uses, including batteries, electronics, and as chemical-producing catalysts. Equally important are silver’s medical applications, whose antibacterial properties have been known for centuries. The Silver Institute website explains how it works:
Silver interrupts the bacteria cell’s ability to form the chemical bonds essential to its survival. These bonds produce the cell’s physical structure so when bacteria meets silver it literally falls apart. For this reason, silver-enforced bandages are especially in demand. Bandages with silver ions prevent bacterial growth and speed healing time, making them especially valuable for treating burn and wound victims…Silver has actually been proven to promote the growth of new cells, thereby increasing the rate at which wounds can heal. And, unlike other metals with antimicrobial properties, it is not toxic to humans.
Wound dressings containing silver are now widely used to minimize the occurrence of bacterial infection in certain types of wound. The usefulness of these dressings depends upon the chemical and physical nature of the silver, which includes the way in which the silver is distributed over the dressing. This analysis requires the ability to produce images over a large area and at high resolution over a small area. The quantity of silver present in these dressings is small, so high sensitivity is essential.
The spectroscopic imaging capability of an X-ray photoelectron spectroscopy (XPS) microprobe makes this an ideal instrument for assessing the surface distribution of the silver within the dressing on both a large and a small scale. Large scale spectroscopic imaging can be accomplished by stage mapping, and small-scale, high-resolution imaging makes use of the parallel imaging capability of the instrument.
Analysis of a Wound Dressing describes how an XPS microprobe was used to quantitatively map the low concentration of silver on a wound dressing. Using a set of large-area spectrum images, a position was defined for small-area, high-resolution, parallel imaging. This method ensures that the position for the high-resolution map can be selected quickly and accurately. For the high-resolution measurements, the parallel imaging was combined with spectroscopic imaging. This ensures that for each element, there was a spectrum acquired at each pixel of the image, enabling accurate quantification of the images. Quantified chemical state images from the wound dressing showed that the silver is associated with the areas of the dressing having a low concentration of oxygen.