What are nanoparticles?
Nanoparticles are units of a uniform material that are between 1 and 100 nanometers. (To put this size in perspective, nanometer : meter :: marble : Earth.) Before the term "nanoparticle" was coined, these materials were referred to as "ultrafine," the smallest units of a material possible (atoms and molecules don't count). Metals in this form have been used since ancient times, most often to create a sparkling luster in artwork. Nanoparticles are created under intense heat and in combination with a suspension material - pottery glaze in the past, and today, polymer, ceramics, and other composites.
What makes nanoparticles special?
Size matters when it comes to materials. Nanoparticles behave differently - interact with their environment differently - due to their small size and high surface area. Bulk units of material have a low ratio of surface atoms to internal atoms - there are just so many more internal atoms that those on the surface are a tiny percentage of the overall mass. This means that the unit behaves (interacts) overwhelmingly based on the characteristics of the internal atoms. In tiny particles of material, however, the surface atoms are significant, since they are in a more substantial proportion to the internal atoms, and in some cases, in greater proportion. (Think about this: a spoonful of sugar has more surface area that an Olympic-sized swimming pool!). For this reason, nanoparticles react differently to their environment than larger units of the same material.
An analogy of this concept is ice. A large chunk of ice in a drink will melt slowly as the outside crystals interact with the surrounding liquid. In contrast, the same volume of crushed ice, or even more so, shaved ice, will melt much faster. There is simply more ice surface area for your drink to interact with.
While the chemical processes are different, the same idea applies to metals and other elements. Bulk elements such as carbon, silver, and silicon have certain set characteristics, but those characteristics change when those elements exist in nano-sized particles. Gold, for example, is inert as a bulk material, but at the nanoscale, acts as a catalyst. This change in characteristics leads to many interesting, and potentially life-altering nanoparticle applications.
What is nanotechnology?
Because nanoparticles interact differently with their environment, they present novel and ever-growing opportunities for use in technology. Depending on the material, nanoparticles can make typically hard materials stretchy, can be manipulated into tiny structures that can be used in medical research and treatments, can conduct electricity more efficiently, and interact fatally with microorganisms. Nanotechnology has been used to create longer-lasting tennis balls, more effective car wax, faster and smaller computers, drug delivery patches, more sensitive medical monitors, and even man-made skin.
As an interesting side-note, nanotechnology in its most complicated and effective forms are found in nature. The flagellum of a bacteria cell, the cleaning crystals on the surface of a lotus leaf, and the adhesive structures on the feet of geckos are just some examples of how nanotechnology already surrounds us.
Recently, many antimicrobial products using nanotechnology have emerged in the marketplace. Most of these products use metal nanoparticles to slow the growth of odor-causing bacteria and fungi. But not all uses of antimicrobial nanotechnology are equal, and some of them are downright false advertising. We will explore how to be an educated consumer of antimicrobial nanotechnology in our next post!