18-04-2012, 02:56 PM
Virus Killer Gets Supercharged: Discovery Greatly Improves Common Disinfectant
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Rather than trying to turn the process into profit, the researchers have put it into the public domain. They hope wide adoption will save time, money and perhaps even lives.
The Rice professors and their team reported in Environmental Science and Technology, an American Chemical Society journal, that adding silicone to titanium dioxide, a common disinfectant, dramatically increases its ability to degrade aerosol- and water-borne viruses.
"We're taking a nanoparticle that everyone's been using for years and, with a very simple treatment, we've improved its performance by more than three times without any real cost," said Barron, Rice's Charles W. Duncan Jr.-Welch Professor of Chemistry and a professor of materials science. Barron described himself as a "serial entrepreneur," but saw the discovery's potential benefits to society as being far more important than any thoughts of commercialization.
Barron said titanium dioxide is used to kill viruses and bacteria and to decompose organics via photocatalysis (exposure to light, usually ultraviolet). The naturally occurring material is also used as a pigment in paints, in sunscreen and even as food coloring.
Disinfectants May Promote Growth of Superbugs
Researchers from the National University of Ireland in Galway found that by adding increasing amounts of disinfectant to laboratory cultures of Pseudomonas aeruginosa, the bacteria could adapt to survive not only the disinfectant but also ciprofloxacin -- a commonly-prescribed antibiotic -- even without being exposed to it. The researchers showed that the bacteria had adapted to more efficiently pump out antimicrobial agents (disinfectant and antibiotic) from the bacterial cell. The adapted bacteria also had a mutation in their DNA that allowed them to resist ciprofloxacin-type antibiotics specifically.
P. aeruginosa is an opportunistic bacterium that can cause a wide range of infections in people with weak immune systems and those with diseases such as cystic fibrosis (CF) and diabetes. P. aeruginosa is an important cause of hospital-acquired infections. Disinfectants are used to kill bacteria on surfaces to prevent their spread. If the bacteria manage to survive and go on to infect patients, antibiotics are used to treat them. Bacteria that can resist both these control points may be a serious threat to hospital patients.
Nanotubes
Anatase can be converted by hydrothermal synthesis to delaminated anatase inorganic nanotubes [15] and titanate nanoribbons which are of potential interest as catalytic supports and photocatalysts. In the synthesis, anatase is mixed with 10 M sodium hydroxide and heated at 130 °C for 72 hours. The reaction product is washed with dilute hydrochloric acid and heated at 400 °C for another 15 hours. The yield of nanotubes is quantitative and the tubes have an outer diameter of 10 to 20 nm and an inner diameter of 5 to 8 nm and have a length of 1 μm. A higher reaction temperature (170 °C) and less reaction volume gives the corresponding nanowires
Applications
Pigment
Titanium dioxide is the most widely used white pigment because of its brightness and very high refractive index (n = 2.7), in which it is surpassed only by a few other materials. Approximately 4 million tons of pigmentary TiO2 are consumed annually worldwide. When deposited as a thin film, its refractive index and colour make it an excellent reflective optical coating for dielectric mirrors and some gemstones like "mystic fire topaz". TiO2 is also an effective opacifier in powder form, where it is employed as a pigment to provide whiteness and opacity to products such as paints, coatings, plastics, papers, inks, foods, medicines (i.e. pills and tablets) as well as most toothpastes. In paint, it is often referred to offhandedly as "the perfect white", "the whitest white", or other similar terms. Opacity is improved by optimal sizing of the titanium dioxide particles.
Health and safety
Titanium dioxide is incompatible with strong oxidizers and strong acids.[30] Violent or incandescent reactions may occur with metals (e.g. aluminium, calcium, magnesium, potassium, sodium, zinc and lithium).
Titanium dioxide accounts for 70% of the total production volume of pigments worldwide. It is widely used to provide whiteness and opacity to products such as paints, plastics, papers, inks, foods, and toothpastes. It is also used in cosmetic and skin care products, and it is present in almost every sunblock, where it helps protect the skin from ultraviolet light.
What is Titanium Dioxide?
Titanium dioxide is a naturally occurring oxide of the element titanium. Also referred to as titanium (IV) oxide or titania, this substance also occurs naturally as three mineral compounds known as anatase, brookite, and rutile. However, it is most commonly extracted from titanium tetrachloride by carbon reduction and re-oxidization. Alternatively, it may be processed from another oxide called ilmenite, which is subjected to reduction with sulfuric acid to achieve pure titanium dioxide.