0.05 g/L nanoparticle (NP) solutions and control (No NPs) containing 1 mM tetrazolium salt (XTT)
and subjected to 1000 W/m² illumination using a solar simulator. In the presence of superoxide
radicals, the salt molecules oxidise in formazans from the typical red colour.
The figure shows that the production of radicals is photo-catalyzed by the NPs.

Due to their unique physical properties, engineered nanoscale materials are used to impart enhanced functionality and improved performance to a wide range of materials and products, e.g. sunscreens and antibacterial coatings.

One of the nanoparticle properties under investigation at NPL is the photo-production of reactive oxygen species (ROS), such as superoxyde radicals and hydrogen peroxide, which is catalyzed by nanoparticles. Our interest is motivated by two reasons.

First, the growing use of nanomaterials in consumer products implies that living organisms, including humans, are increasingly exposed to these materials; in the framework of NPL's activity on toxicological assessment of nanomaterials, we aim to understand the mechanism of nanoparticle-catalyzed photo-production of ROS to elucidate the capacity of nanoparticles to cause photo-damage to humans and the environment.

Second, the nanoparticles' ability to catalyze the production of ROS is exploited in a wide range of technology, including energy, antibacterial coatings and cancer therapy. The reference materials and methodologies under development at NPL will support the development of novel applications for these materials.

Contact: Caterina Minelli