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commercial nanoparticles are used in a wide variety of products and applications such as antimicrobial/antifungal coatings on cell phones, computers and keyboards; UV light-emitting diodes for LCD screens on devices such as smart phones; solar thermal products made from copper (zno)nanowires; and inks for printed electronics in RFID/smart cards, e-book readers and flexible displays. Controlling the size and shape of these particles allows engineers to create novel materials that exhibit properties not seen in bulk materials. Examples include the ability of titanium dioxide to form a self-cleaning coating for plastic garden chairs that seals dirt in water, which is then removed by the next shower.
These NPs are manufactured using a variety of techniques including the Sol-Gel process. EPA is developing scientific methods to characterize their unique properties, including size and surface chemistry, in order to assess their environmental fate and transport in the environment (e.g., soil and sediments) as well as to identify biomarkers of ecological exposure and impact.
Several TWI Members are involved in the production of these NPs for a variety of applications. To support the characterization of their unique properties, TWI has developed a cryo-TEM instrument capable of rapidly changing the state of the material from fluid to glassy without adding other compounds, thereby maintaining the original composition and structure of the product under investigation. This capability is particularly useful in analyzing powdered or liquid TD-NPs and nanobubble waters (NBWs), which often are agglomerated/aggregated with the multi-components present in complex food systems. NPs were characterized for their constituent particle size and shape, hydrodynamic diameters, zeta potentials and surface chemistry by SEM at low acceleration voltage and cryogenic TEM. Several NPs were found to have deleterious effects on nontarget microbes as evidenced by the formation of pits in their outer membrane, collapse of plasma membrane potential and decreased ATP in short exposure experiments. Identifying conditions that promote NP aggregation could reduce these impacts.