The method comprises contacting a silicon substrate with a silver salt and an acid for a time effective to produce spikes having a first end disposed on the silicon substrate and a second end extending away from the silicon substrate. The spikes have a second end diameter of about 10 nm to about 200 nm, a height of about 100 nm to 10 micrometers, and a density of about 10 to 100 per square microns. The nanostructures provide antimicrobial properties and can be transferred to the surface of various materials such as polymers.