Visible light activated photocatalysts can be deployed for self-cleaning, air and water purification and many other interesting applications usually without any post-deployment non-renewable energy costs. This is because the photocatalysts are able to decompose pollutants (like dyes, volatile organic compounds and NOx) using light available in the ambient like solar radiation or indoor and outdoor lighting. With the anticipated rapid adoption of UV-free indoor lighting (like LEDs and OLEDs), it is imperative to find ways to deploy visible-light activated photocatalysts in indoor applications for instance in cleaning room air in domestic, public and commercial spaces especially in confined areas like aircraft, public buildings, etc. Moreover, additional applications for antibacterial surfaces and self-cleaning materials can have wide applicability in the food service, transportation, health care and hospitality sectors.
Elemental copper, copper composites, alone or in combination with metal oxides, have been described as useful photocatalytic/antibacterial/antiviral materials. See United States Patent Publication Nos. 2007/0154561, 2009/0269269, 2011/0082026, 2012/0201714; and Qiu, Xiaoqing, et al, Hybrid CuXO/TiO2 Nanocomposites as risk-reduction materials in indoor environments. ACS Nano, 6(2):1609-1618 (2012). Elemental copper however, shows a [adjective] degradation of antibacterial activity over time (durability) and unappealing cosmetic appearance change (from Cu metal to black CuO) both believed due to oxidation of elemental copper under normal application conditions. Thus there is a need for improved longevity of anti-bacterial activity over time. Thus there is a need for photocatalytic materials that provide antibacterial/antiviral activity without unappealing cosmetic appearance changes.