Why Not Use Copper

Problem

• It has long been well-established that copper has antimicrobial properties when it is applied in the form of nanoparticles (NP).
• The challenge has been that they have a negative surface charge, which means they can not settle naturally into a new compound.
• Because they have this barrier to agglomeration, their antimicrobial properties are decreased.

Chemical Solution

• Research shows that this problem has been solved by the creation of silica nanospheres, which contain immobilized copper NPs.
• The resulting products can be applied as an active antibacterial additive for architectural paints.

Results of recent research

• A 2019 article in Nature states that latex paints containing copper-glass ceramic powder have been tested according to US EPA standards. The results showed ≥99.9% antibacterial counts, which resulted in acceptable efficacy of copper-alloy surfaces as a sanitizer, approaching that of benchmark metallic copper.
• Recent research by scientists at the Royal Society of Chemistry in Britain stated that copper oxide is commercially applicable in paints, fabrics, agriculture and hospitals either as constituent powders or as coated films. The purpose of the research was to show the mode of antibacterial action of CuO and Cu2O. The conclusion stated that "intracellular proteins have high affinity towards Cu2O rather than CuO" which suggests the use of Cu20 in antimicrobial paints.
• A patent with the title "Metallic copper dispersion, process for producing the metallic copper dispersion, electrode, wiring pattern, and coating film formed using the metallic copper dispersion, decorative article and antimicrobial article with the coating film formed thereon, and processes for producing the decorative article and the antimicrobial article" is currently active in the US patent office. 

Silver vs Copper

• Copper is indeed an effective antimicrobial. However, questions surround the use of copper additives as antimicrobial technology.
• Copper is not an approved biocidal in Europe. In the European Union, companies cannot use a copper-based additive and say it is antimicrobial, or they are in breach of the regulations.
• Using silver allows for a customized color for the buyer. Copper, on the other hand, can only result in different shades of copper, which limits its use. Copper oxidizes, is relatively soft and corrodes quickly. It also does not keep its color, so what was once a bright hygienic white becomes a darker, duller wall.
• Copper must be cleaned regularly to maintain its antimicrobial characteristics. Unlike silver, paint with copper additives requires a two-step process. After it is washed with regularly used cleaning products, it must again be washed down with water.

Stability and Shelf-life

• A recent research study stated that nanofluids with a large total surface area, consisting of CuO NPs in water or ethylene have increased stability.
• A product sheet for copper paint from Eckhart gives their paint a shelf life of 10 years. 

Decorative Paint vs Marine Coatings

• Marine coatings have been shown to slowly leach 100% of their copper into the water, causing significant environmental concerns. They are considered to be a significant source of toxic emissions into the water.
• Antimicrobial paint used on walls does not show the same pattern of emissions as marine coatings.
• Painted surfaces with proposed medical or other antimicrobial applications have a burst release profile, which means that a significant amount of the copper is released into the air in the first hours or days.
• There is not the same environmental concerns for decorative paint as there is in marine coatings due to the leaching concerns of the latter.

Research Strategy