Microbecide® Photo Catalytic Oxidation (PCO) coatings are a sol (aqueous) form with a super high surface area. Our PCO TiO2 Sol products are manufactured in a different, proprietary process as compared to powder (anhydrous) forms of production. Our proprietary processes assemble the particles in water directly by charging the protective layers of sol to keep the sealant complex stable. We use proprietary technology to physically charge the potential of all particles.
This charged layer prevents the particles from linking together in the water system, providing perfect dispersion. Upon installation, when the sol begins to dry the charged potential disappears as the carrier (water) evaporates. This drying process is more similar to an organic polymer linking process, the particles in the sol reunite together. Upon applicaton with an electrostatic sprayer, the carrier evaporates within seconds.
The particles do not simply agglomerate, they build up a three dimensional lattice film structure of high porosity. More than 70% of the film will be air with the particles forming a crystal-like framework (skeleton). Due to the porous structure, the surface area of the particles are quite large, up to 160-240 sqm /g.
Our aqua system is a non-toxic, non-corrosive TiO2 Sol, we do not form any solid (anhydrous) particle and our sol-gel process can be completed at room temperature. At the edge, each single crystal still has a “quantum effect” of an electron-hole pair, while the recombination rate is delayed by the Ag-doped particles enhancing photocatalytic activity.
Enhanced Reactivity of Microbecide® PCO Coatings
TiO2 (titanium dioxide), a photocatalytic agent, well known for its high photoreactivity, broad-spectrum antimicrobial and chemical stability, has been used extensively against different groups of microorganisms including bacteria, fungi and viruses. The photocatalytic activity of TiO2 particles depends not only on the properties of the TiO2 material itself, but also on the modification of TiO2 with metal or metal oxide. The addition of noble metal (such as silver) to titanium dioxide enhances its photocatalytic efficiency. The doping process deposits Ag on the surface of TiO2 particles. This increases the value of the e--h+ charge separation by decreasing the band-gap energy, and leads to a delay in the recombination rate enhancing photocatalytic activity.
The term “band gap” refers to the energy difference between the top of the valence band to the bottom of the conduction band of a semiconductor material. Band gap energy is the specific minimum amount of energy required for an electron to jump from a valence band to a conduction band. The band gap energy of insulators is large (> 4eV), but lower (< 3eV) for semiconductors and materials such as titanium dioxide (TiO2).
Optical band-gap energies decrease with the doping of silver, which allow the delay in recombination rate and enhance photocatalytic activity. The photocatalytic activity of silver-doped TiO2 particles is significantly higher in comparison to TiO2 particles. The absorption edge of TiO2 particles at 385 nm is in the ultra violet light range. After doping with silver the response of TiO2 particles to visible light is increased and shows red shift (towards increased wavelength) showing the absorption edge at 435 nm to 450 nm (visible region).
Ag-doped TiO2 also shows more antimicrobial activity on Gram-negative bacteria because Gram-positive bacteria have more peptidoglycan than Gram-negative in the cell wall, which is negatively charged, and more silver ions may get trapped to peptidoglycan in Gram-positive bacteria. It has been demonstrated that the percentage of survivable bacteria is exponentially reduced with respect to an increasing concentration of Ag doped into the TiO2 matrix.
Microbecide® PCO Coating Safety
The PCO Sol form provides the highest safety to the end user and installers. There is no super-fine powder in the entire process, from manufacture through installation in a customer´s facility. Microbecide® PCO coatings creates a protective "Active Surface" barrier that provides an active antimicrobial function for up to six months or more on PCO TiO2 Sol coated surfaces.