What is Photocatalyst?

 What is Photocatalyst ?

Photo-Catalysis is defined as "acceleration by the presence of as catalyst". A catalyst does not change in itself or is consumed in the chemical reaction.

Chlorophyll of plants is a type of photocatalyst. Photocatalysis compared to photosynthesis: chlorophyll captures sunlight to turn water and carbon dioxide into oxygen and glucose, photocatalysis creates a strong oxidation agent to breakdown any organic matter to carbon dioxide and water in the presence of a photocatalyst, plus the UV rays from either the sun or an artificial light source (such as fluorescent lights).

Mechanism

When photocatalyst titanium dioxide (TiO2) absorbs Ultraviolet (UV) radiation from sunlight or an illuminated light source (fluorescent lamps), it will produce pairs of electrons and holes.
The electron of the valence band of titanium dioxide becomes excited when illuminated by light. The excess energy of this excited electron promotes the electron to the conduction band of  titanium dioxide thereby creating the negative-electron (e-) and positive-hole (h+) pair. This stage is referred to as the semiconductor's "photo-excitation " state. The energy difference between the valence band and the conduction band is known as the ' Band Gap '. Wavelength of the light necessary for photo-excitation is: 
1240 (Planck's constant, h) / 3.2 ev (band gap energy) = 388 nm

The positive-hole of titanium dioxide breaks apart the water molecule to form hydrogen gas and hydroxyl radical. The negative-electron reacts with oxygen molecule to form a super oxide anion. This cycle continues when light is available.

Photocatalytic Oxidation

The most powerful advanced oxidation systems are based on the generation of hydroxyl radicals. The hydroxyl radical is an extremely powerful oxidation agent, second only to Fluorine in power (2.23 in Relative Oxidizing Power). Following is a listing of common chemical oxidants, placed in the order of their oxidizing strength:

Utilizing the strong oxidation strength of hydroxyl radical, photocatalytic oxidation can effectively disinfect, deodorize, and purify air, water, and different surface areas.

Super-Hydrophilic

When the surface of photocatalytic film is exposed to light, the contact angle of the photocatalyst surface with water is reduced gradually. After enough exposure to light, the surface reaches super-hydrophilic. In other words, it does not repel water at all, so water cannot exist in the shape of a drop, but spreads flatly on the surface of the substrate: water takes the form of a highly uniform thin film, which behaves optically like a clear sheet of glass.

The hydrophilic nature of titanium dioxide, coupled with the gravity, will enable the dust particles to be swept away following the water stream, thus making the product self-cleaning.

 Why is Green Quest photocatalyst treatment  semi-permanent? 
  

Although it is originally water-soluble, it dries quickly after application and becomes water-insoluble. It also becomes as hard as a 4H pencil in ten to fourteen days after application. It does not come off unless the surface is polished. Even a bathroom can be used immediately after application. Because titanium oxide is merely a catalyst and is not changed, its effect is semi-permanent except when walls and ceilings are repainted, or if a strong cleaning agent is used. 
 
How long does Green Quest photocatalyst treatment last after application? 

 Since photocatalyst TiO2 is only acting as semi-conductor catalyst, it is not consumed during the oxidation process, therefore, completing a long lasting oxidation cycle. Green Quest is now offering a five years product and services warranty.  
   
Is Green Quest photocatalyst treatment safe?

   Yes , it will be no harm of direct touching the material or having direct contact with it after its drying time. The material is totally safe and the titanium dioxide used is FDA approved (refer to EPA certified toxicity lab report). 

 Where can Green Quest photocatalyst treatments be applied?

 Green Quest provides photocatalyst surface coating for long-lasting effects of deodorization, sterilization, and anti-soiling purposes. Using our specialized spray-coating equipments, a fine mist of photocatalyst can be applied on different types of surface materials achieving a guaranteed result.

In Automobiles,  Building Exteriors
Photocatalyst can deodorize the interior and gives the driver and passengers a more pleasant driving experience. Odors embedded in the carpet and seats will eventually be decomposed and rid the car these unpleasant odors.

•  Company Cars 
   Public transportation (buses, trains, airplanes, taxis) 
   Rental cars 
   Limousines    

Green Quest's Nano-TiO2 Photocatalyst can be applied on the exterior of a building to treat and prevent unsightly damages caused by acid rain, moisture, and smog. It cuts down on the overall maintenance cost and time. 

• Hotels and motels
  High-rise buildings
  Apartments
  Condos 
  Commercial business complexes  

Green Quest's Nano-TiO2 Photocatalyst decomposes odor molecules caused by tobacco smoke, pets, chemicals in detergents, urine and fecal matters. Photocatalyst will continuously deodorize your living space and eliminates the sources of your malodors. 

•  Restaurant 
   Public restrooms 
   Hotel and motel rooms 
   Senior Centers
   Shops and animal hospitals    

• With a constant amount of light provided, Green Quest's Nano-TiO2 photocatalyst can control and prevent the growth of bacteria, germ, and mold. Any harmful bacteria and germ would be killed and eventually be decomposed in this sterilized condition. 
   
• Hospital 
  Schools
  Public Restrooms
  Restaurant 
   Day-Care centers 
   
  How does Green Quest photocatalyst treatment compare to traditional air purification system?

HEPA (High Efficiency Particle Arresting) Filter
Most widely known method for purifying air. Depending on the filter size, it can clean up to 99.99% of particulate in the air with proper ventilation. They are not effective on treating mold, mildew, bacteria, and other fungi.

Electrostatic Filtration
Another filtration system with a negatively charged surface is used to attract particulates. In comparison to most HEPA systems it is more effective in trapping smaller micron particulates and is effective in clearing smoke from the air. Low levels of ozone may be produced which can neutralize most mold, mildew, bacteria, and other fungi that comes in contact with the filter.

Ionization
Also uses a negatively charged surface to produce and expel an abundance of negative ions and cause suspended particles to cling to walls, floors, and other surfaces . Most ionizes are effective in settling dust and particulates out of our breathing space.

Ozone
Ozone is a very powerful oxidizer that will neutralize odors, mold, mildew, bacteria, and other fungi. This technology is commonly used in flood and fire restoration. Ozone is found to be effective because it works on the problem at the source and air does not have to be pulled through the unit for treatment.

UV Germicidal Lamps
Commonly used for disinfectant purposes. This technology is effective in sterilizing air and surfaces that come in contact with the UV light. UV has been proven in both air and water applications to inactivate bacteria and viruses to prevent them from reproducing.

Photocatalysis
Using light to react with a catalyst resulting in oxidation. This is found to be effective in destroying mold, mildew, bacteria, other fungi, dust mites, and many odors. This technology is produced with an Ozone/UV lamp set in a variety of combinations. When this type of photocatalysis is combined with the natural humidity in indoor air, it creates hydroxyl radicals and super oxide ions that are effective in combating bacteria, fungi and VOCs(volatile organic compounds). This method is also a pro-active approach that goes to the source for treatment. 

 What factors may influence the efficiency of Green Quest photocatalyst treatment?

 Light and airflow will have a remarkable influence over the reaction of the photocatalyst. Both factors are needed to maintain the coating effectiveness all the time. From that, the better airflow you have (air circulation which can be obtained by using an ordinary fan or the normal air movement from central air) and the longer light times, the better the results will be.
 
What is Indoor Air Pollution?
 

Research indicates that people spend approximately 80 ~ 90 percent of their time indoors, where they are exposed to polluted indoor air that may cause irritation of the eyes, nose, and throat, headaches, dizziness, fatigue, and even lung cancer or other malignancies. Recent studies reveal that bacteria, molds and house dust mites are breeding inside carpets and air conditioners and can be airborne by dust particles. Paints, varnishes, harmful chemical fibers and pressed wood products, which are most commonly used in household decoration, may emit formaldehyde, benzene and other hazardous and carcinogenic organic chemicals -- all these as well as unwholesome matters produced in the metabolism of human bodies and the ammonia inside toilets have made the air within homes and buildings more seriously polluted than the outdoor air.

People may experience one or more of the following reactions when exposed to indoor air pollution:

Allergic Reactions
Some common signs and symptoms are: 
· Watery eyes
· Runny nose and sneezing
· Nasal congestion
· Itching
· Coughing
· Wheezing and difficulty breathing
· Headaches
· Fatigue  

Infectious Reactions

Caused by bacteria and viruses, such as influenza, measles, chicken pox, and tuberculosis. Most infectious diseases pass from person to person through physical contact. Crowded conditions with poor air circulation can promote the spread of infectious diseases. Some bacteria and viruses thrive in buildings and circulate through indoor ventilation systems that have poor filtration systems in place or are not serviced regularly. 

Toxic Reactions

Some fungi are known to produce toxic substances as a by-product of their metabolism, which can cause a variety of adverse health effects. Short-term symptoms can include dermatitis, respiratory irritation, headaches and fatigue. Long-term health effects can include cancer, damage to the central nervous system, and suppression of the immune system.
The U.S. Environmental Protection Agency ranks poor indoor air quality among the top five environmental risks to public health. Poor indoor air quality can cause or contribute to the development of chronic respiratory diseases such as asthma and pneumonitis. In addition, it can cause headaches, dry eyes, nasal congestion, nausea and fatigue. People who already have respiratory diseases are at greater risks.

What is Sick Building Syndrome? 

   The term " sick building syndrome " (SBS) is used to describe situations in which building occupants experience acute health and comfort effects that appear to be linked to time spent in a building, but no specific illness or cause can be identified.
The following have been cited causes of or contributing factors to sick building syndrome:

1. Inadequate ventilation
In an effort to achieve acceptable Indoor Air Quality or IAQ while minimizing energy consumption, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recently revised its ventilation standard to provide a minimum of 15 cfm of outdoor air per person (20 cfm/person in office spaces). Up to 60 cfm/person may be required in some spaces (such as smoking lounges) depending on the activities that normally occur in that space.

2. Chemical contaminants from indoors sources
Most indoor air pollution comes from sources inside the building. For example, adhesives, carpeting, upholstery, manufactured wood products, copy machines, pesticides, and cleaning agents may emit volatile organic compounds (VOCs), including formaldehyde. Environmental tobacco smoke contributes high levels of VOCs, other toxic compounds, and repairable particulate matter. Research shows that some VOCs can cause chronic and acute health effects at high concentrations, and some are known carcinogens. Low to moderate levels of multiple VOCs may also produce acute reactions. Combustion products such as carbon monoxide, nitrogen dioxide, as well as respirable particles, can come from unvented kerosene and gas space heaters, wood stoves, fireplaces and gas stoves.

3. Chemical contaminants from outdoor sources
The outdoor air that enters a building can be a source of indoor air pollution. For example, pollutants from motor vehicle exhausts, plumbing vents, and building exhausts (e.g., bathrooms and kitchens) can enter the building through poorly located air intake vents, windows, doors, and other openings. In addition, combustion products and pollution can enter a building from a nearby garage, traffic from a busy street or highway, or a car that is idling.

4. Biological contaminants
Bacteria, molds, pollen, and viruses are types of biological contaminants. These contaminants may breed in stagnant water that has accumulated in ducts, humidifiers and drain pans, or where water has collected on ceiling tiles, carpeting, or insulation. Physical symptoms related to biological contamination include coughing, chest tightness, fever, chills, muscle aches, and allergic responses such as mucous membrane irritation and upper respiratory congestion.

Other Significant Usages for Photocatalysis

1. Anti-Bacterial Effect

Photocatalyst does not only kill bacteria cells, but also decompose the cell itself. The titanium dioxide photocatalyst has been found to be more effective than any other antibacterial agent, because the photocatalytic reaction works even when there are cells covering the surface and while the bacteria are actively propagating. The end toxin produced at the death of cell is also expected to be decomposed by photocatalytic action. Titanium dioxide does not deteriorate and it shows a long-term anti-bacterial effect. Generally speaking, disinfections by titanium oxide is three times stronger than chlorine, and 1.5 times stronger than ozone.

2. Deodorizing Effect

On the deodorizing application, the hydroxyl radicals accelerate the breakdown of any Volatile Organic Compounds or VOCs by destroying the molecular bonds. This will help combine the organic gases to form a single molecule that is not harmful to humans thus enhance the air cleaning efficiency. Some of the examples of odor molecules are: Tobacco odor, formaldehyde, nitrogen dioxide, urine and fecal odor, gasoline, and many other hydro carbon molecules in the atmosphere. 

Air purifier with Ti02 can prevent smoke and soil, pollen, bacteria, virus and harmful gas as well as seize the free bacteria in the air by a filtering percentage of 99.9% with the help of the highly oxidizing effect of photocatalyst (Ti02). 

3. Air Purifying Effect

The photocatalytic reactivity of titanium oxides can be applied for the reduction or elimination of polluted compounds in air such as NOx, cigarette smoke, as well as volatile compounds arising from various construction materials. Also, high photocatalytic reactivity can be applied to protect lamp-houses and walls in tunneling, as well as to prevent white tents from becoming sooty and dark. Atmospheric constituents such as chlorofluorocarbons (CFCs) and CFC substitutes, greenhouse gases, and nitrogenous and sulfurous compounds undergo photochemical reactions either directly or indirectly in the presence of sunlight. In these polluted areas, the pollutants can eventually be removed. 

4. Anti fogging, Self-Cleaning

Most of the exterior walls of buildings become soiled from automotive exhaust fumes, which contain oily components. When the original building materials are coated with a photocatalyst, a protective film of titanium provides the self-cleaning building by becoming antistatic, super oxidative, and hydrophilic. The hydrocarbon from automotive exhaust is oxidized and the dirt on the walls washes away with rainfall, keeping the building exterior clean at all times.

5. Water Purification

Photocatalyst coupled with UV lights can oxidize organic pollutants into nontoxic materials. CO2 and water and can disinfect certain bacteria. This technology is very effective at removing further hazardous organic compounds (TOCs) and at killing a variety of bacteria and some viruses in the secondary wastewater treatment. Pilot projects demonstrated that photocatalytic detoxification systems could effectively kill fecal coli form bacteria in secondary wastewater treatment.

Lab Results: 

• Bacteria Decomposition Test - Kyoto Microorganism Research Center
• Bacteria Decomposition Test - Japanese Chinaware Examination Association
• Bacteria Decomposition Test - Food Inspection Center of Osaka Hygienic Food Association
• Bacteria Decomposition Test - Kyoto Biseibutsu Kenkyujo (A specified laboratory by Japanese Ministry of Health, Labor and Welfare)
• Oil Decomposition Test - Saga Ceramic Research Laboratory
• Gas Decomposition Test - Far Infrared Rays Application Research Center
• Toxicity Report - Enviro-Chem, Inc (A designated EPA certified laboratory)
• Stain Decomposition Test
• Particle Size

Researches from institutions:

·        NASA - SpaceResearch - Securing the Home Planet

·        Reducing MeBr Emissions with a Sheet Containing Titanium Dioxide

Industrial Reviews:

·         CNN - Shuttle experiment leads to longer-lasting produce ...

·         Special Reports > Residential Air Cleaning Devices > Appendix 3

·         Annihilating Anthrax

·         CUHK Research in Nanotechnology Serves the Community

·         New Pollutant Cleanup Technique Puzzles, Pleases Chemists

·         Nanotechnology: A new world of Matter

·         UW Clean-Air Technology Headed For The Produce Section

·         Smog-busting paint soaks up noxious gases

Technology Breakthrough -

Green Quest's Photocatalyst Products are truly the breakthrough in dispersing nano-sized Titanium Dioxide in aqueous form. Using their patented manufacturing process and chemical formula, Green Quest's Photocatalyst products are neutral in ph and contain no VOCs. Titanium Dioxide particles in Green Quest?s products would not form any deposits which would prolong left expectancy (residuals) of the product.

Photocatalyst is now available from Innovative Sealing Solutions, Inc.

which is a licensed member of Tekon Universal Sciences Corporation.

Green Quest is a subdivision of  Tekon Universal Sciences Corporation.