Following on yesterday’s revelation about Ecotech Marine’s work with nano materials, we were fortunate to get some face time with NanoSystems director and EM co-founder Patrick Clausen. Are you a fan of Titanium Dioxide (TiO2)? If not you are about to have your mind blown with more photocatylitic knowledge than you could ever care to know. Read on for our technical interview with Ecotech Marine.
Morning pat, thanks for speaking with us. So how long has EM been working on nano materials?
The NanoSystems project was a result of graduate work done with Lehigh University and the Center for Advanced Materials and Nanotechnology. Our focus was to bring a photocatalytic coating the the world of reef aquariums and to other markets.
How does the nano material work?
Our self-cleaning technology is based on high photo-catalytic activity of novel coatings of titanium dioxide (TiO2) nano-particles on substrates. The TiO2 is produced in the form of a suspension or sol of the TiO2 particles in a water-based system. On drying, the sol is capable of producing continuous, nano-porous coatings from the non-stoichiometric TiO2 produced by this process. The TiO2 coating exhibits a high degree of photo-catalytic activity without the need for a sintering process or binder to adhear particles to a substrate. These characteristics separate our technology from any other on the market. The EcoShield robust TiO2 nano-particle coating catalyzes the reaction of organic matter, with the assistance of sunlight, oxygen and water vapor, making it difficult for organisms or other organic matter to adhere to the coated surfaces. In this process, the organic molecules are oxidized into harmless compounds.
When TiO2 is exposed to UV light, e.g. from sunlight, it absorbs the radiation and releases an electron-hole pair. The following reactions occur on the surface of TiO2 crystals in the presence of water and oxygen:
Photolysis of H2O: H2O â†’ H+ + OH. (hydroxyl radical) + e-
O2 + e- â†’ O2- (a superoxide ion)
The overall reaction is:
H2O + O2 â†’ H+ + O2- + OH.
The hydroxide radical is a powerful oxidizing agent, even stronger than chlorine which is commonly used as a sterilizing agent. The hydroxyl radical and the superoxide ion are capable of oxidizing a variety of hydrocarbons; even all the way back to carbon dioxide and water. The hydroxide radical can also inhibit the growth of bacteria, algae and mold as well as prevent the buildup of pollution and organic dirt of a wide variety of surfaces; the reactions are highly accelerated in the presence of TiO2 nano-particles.
Is ecotech still in development process to implement the self cleaning coating for aquarium use?
The reef aquarium market poses a particular challenge for the creation of a “self cleaning” glass box. Specifically, the penetration of UV radiation through the water mass coupled with the geometrical constraints of the aquarium walls makes it difficult to promote a strong catalytic effect. However, the effect itself can be heightened by introduction of transition metal ions into the coating material. EcoTech NanoSystems is still in development of this technology.
What are the hurdles in getting the coating to work and what are the difficulties in making it affordable?Is it possible that future developments in producing the nano coating will make it more affordable in the future?
TiO2 nano-particle films are coated on substrates by a variety of methods including chemical vapor deposition, RF magnetron sputtering, oxidation of Ti coatings, flame decomposition and from sols generated by sol-gel techniques. We have selected sol-gel as the preferred method because of low cost and ease of coating on a variety of substrates.
Typical TiO2 nano-particle sols are formulated with and without binders to facilitate the formation of a continuous coatings. In the case of sols without binders, a powdery coating is obtained which must be sintered at an elevated temperature (e.g. 400 to 600 C) to obtain a continuous film with mechanical integrity.
In the case of sols with binders, the TiO2 particles are embedded within the binder and the binder forms the continuous film. The typical binders may be organic or inorganic, polymers or matrices. The encapsulation of the TiO2 nano-particles within the binder limits the available TiO2 surface and reduces the catalyst photo-activity. In the worse case, with an organic matrix as the binder, the binder undergoes TiO2 promoted UV oxidation attack leading to film yellowing and spalling, thereby rendering the film a short life in service.
The EcoTech NanoSystems coating can be prepared by simply spraying or brushing the sol over a large area followed by drying at 20 to 50 C. The sol leaves behind an ultra-thin and smooth film and expresses the advantageous hydrophilic property and ability to decompose fouling. The EcoShield coating can be used on a wide range of products such as those from glass, metal, ceramics, cellulosics and a variety of polymers.
Any chance we’ll see the nano coating on the Vortech or future products?
It is possible, but not in the near future.
Will EM be releasing any new products this year and when can we look forward to it?
My lips are sealed!!! Thanks for the interview, see you at MAX.