Virus killer gets supercharged

Jan 12, 2011
From left, Professor Qilin Li, graduate student Michael Liga, alumna Huma Jafry and Professor Andrew Barron have published a paper outlining their method to dramatically improve the effectiveness of a common disinfectant. (Credit: Jeff Fitlow/Rice University)

A simple technique to make a common virus-killing material significantly more effective is a breakthrough from the Rice University labs of Andrew Barron and Qilin Li.

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 , an American Chemical Society journal, that adding silicone to , a common , 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.

"If you're using titanium dioxide, just take it, treat it for a few minutes with silicone grease or silica or silicic acid, and you will increase its efficiency as a catalyst," he said.

Barron's lab uses "a pinch" of to treat a commercial form of titanium dioxide called P25. "Basically, we're taking white paint pigment and functionalizing it with sand," he said.

Disinfecting a volume of water that once took an hour would now take minutes because of the material's enhanced catalytic punch, Barron said. "We chose the as our baseline for testing, because it's considered the most polluted river in the world, with the highest viral content," he said. "Even at that level of viral contamination, we're getting complete destruction of the viruses in water that matches the level of pollution in the Yangtze."

Using a smaller amount of treated P25 takes longer but works just as well, he said. "Either way, it's green and it's cheap."

The team started modifying titanium dioxide two years ago. Li, an assistant professor in civil and environmental engineering whose specialties include water and wastewater treatment, approached Barron to help search for new photocatalytic nanomaterials to disinfect drinking water.

The revelation came when students in Barron's lab heated titanium dioxide, but it wasn't quite the classic "aha!" moment. Graduate student and co-author Michael Liga saw the data showing greatly enhanced performance and asked fellow graduate student Huma Jafry what she had done. Jafry, the paper's first author, said, "I didn't do anything," Barron recalled.

When Barron questioned Jafry, who has since earned her doctorate, he discovered she used silicone grease to seal the vessel of P25 before heating it. Subsequent testing with nonsilicone grease revealed no change in P25's properties, whether the sample was heated or not. Remarkably, Barron said, further work with varying combinations of titanium dioxide and silicone dioxide found the balance between the two at the time of the discovery was nearly spot-on for maximum impact.

Barron said binding just the right amount of silica to P25 creates an effect at the molecular level called band bending. "Because the silicone-oxygen bond is very strong, you can think of it as a dielectric," he said. "If you put a dielectric next to a semiconductor, you bend the conduction and valence bands. And therefore, you shift the absorption of the ultraviolet (used to activate the catalyst)."

Bending the bands creates a path for electrons freed by the UV to go forth and react with water to create hydroxyl radicals, an oxidant responsible for contaminant degradation and the most significant reactive agent created by titanium dioxide. "If your conduction band bends to the degree that electrons find it easier to pop out and do something else, your process becomes more efficient," Barron said.

Li saw great potential for enhanced P25. In developed countries, photo reactors designed to take advantage of the new material in centralized treatment plants could more efficiently kill bacteria and inactivate viruses in water supplies while minimizing the formation of harmful disinfection byproducts, she said.

But the greatest impact may be in developing nations where water is typically disinfected through the SODIS method, in which water is exposed to sunlight for its heat and ultraviolet radiation.

"In places where they don't have treatment plants or even electricity, the SODIS method is great, but it takes a very long time to make water safe to drink," Li said. "Our goal is to incorporate this photocatalyst so that instead of taking six hours, it only takes 15 minutes."

Barron wants to spread the good news. "Here's a way of taking what is already a very good environmental catalyst and making it better," he said. "It works consistently, and we've done batch after batch after batch of it now. The methodology in the paper is the one we routinely use. As soon as we buy P25, we treat it."

Explore further: Video: How did life on Earth begin?

More information: Read the abstract at pubs.acs.org/doi/abs/10.1021/es102749e

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User comments : 7

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kenneth_thelandersson
3.7 / 5 (3) Jan 12, 2011
TiO2 is used as photocatalyst - already suggesting toxic activity through the production of
ROS. Wiesner et al. (WIESNER et al., 2006) report a potential neurotoxicity of TiO2. They
found noncytotoxic doses of Degussa P-25 TiO2 particles to cause rapid and sustained
release of ROS by the CNS (Central nervous system)-microglia. Also ATP-levels (Adenosine-
Tri-Phosphate) were affected, mitochondrial depolarization and the stimulation of oxidative
burst in microglia and neurons were observed. In vivo studies with nano titanium dioxide
showed that the particles could be taken up by the lung, pass through the air-blood barrier
and translocate into the blood stream (GEISER et al., 2005). nTiO2 were also found to move
around freely in the cytoplasm (GEISER et al., 2005) allowing the particles to interact with cell
organelles and the nucleus.

Nanoparticles in the Environment
Risk Assessment based on Exposure-Modelling
ETH Zurich, Department of Environmental Sciences
Author: Nicole Müller 2007
fmfbrestel
5 / 5 (1) Jan 12, 2011
"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." -- wikipedia (see the page for specific references)

Yes, the nanoparticles are dangerous, as are nearly all nanoparticles are. So the people making it should wear masks and take precautions, which they do. kids dont die or get any of the symptoms you mention from chewing on (non lead) paint, and no one has been sickened from the TiO2 in toothpaste either. Fearmongering like this is straight up unethical.
fmfbrestel
5 / 5 (1) Jan 12, 2011
if its so dangerous, take your paper, mail it to the FDA, and let them know. Because TiO2 is in your food, toothpaste, paint, paper, medicine, jewelry, and plastics. Otherwise all you're doing is trolling.
stealthc
not rated yet Jan 12, 2011
Actually, health nuts have known for a long time how bad dyes are for you. They are a useless food additive and I would rather be eating colloidal silver, it is healthier and more effective, silver has always been VERY effective against virii and bacteria, and has a long tradition of being effective. It puts TIO2 to shame! I don't care what this man's tinkering does to this dye, if it doesn't make my food better for me, I don't want it, period. I don't care if my food is purple if it tastes good I am still going to eat it.
fmfbrestel
not rated yet Jan 12, 2011
"Nanoparticles fixed in material are likely to be
released only during manufacture and disposal (TÜRK et al., 2005b)." From your own article.
fmfbrestel
not rated yet Jan 12, 2011
@Stealthc: hes not putting it in food, is is painting it on equipment to sterilize water.

But yes, lots of food have TiO2. I suggest buying whole, organic foods whenever possible. No seriously, as much as Kenneth is Fearmongering, processed foods are horrible for you.
trekgeek1
5 / 5 (2) Jan 12, 2011
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


Bravo, the mentality of a Star Trek future. How far along would we be if research was available and cheap to everyone? Every lab and scientist could use the results of others to speed development of future technologies. I am very proud of them.