Graphene-based nanocomposite to adsorb water pollutants

(Nanowerk News) Researchers succeeded in the production of particles with smaller size but higher surface area, and consequently more number of active sites, to adsorb pollutants by synthesizing cerium oxide–titanium dioxide nanoparticles and obtaining cerium oxide–titanium dioxide nanocomposite (see paper in Journal of Hazardous Materials: “Assembly of CeO2–TiO2 nanoparticles prepared in room temperature ionic liquid on graphene nanosheets for photocatalytic degradation of pollutants”).
Among semi-conductive photocatalysts, titanium dioxide (TiO2) is an important candidate to be used in many industries due to its high optical stability and non-toxicity. However, it is impossible to use this component in visible light because its energy gap is placed in the range of ultraviolet.
In this research, researchers from Sharif University of Technology in association with researchers from University of Mohaghegh Ardebili and Nanoscience and Nanotechnology Research Center tried to move the energy gap of TiO2 towards longer wavelengths through the synthesis of carbon-based TiO2 / CeO2 nanocomposite. They also aimed to increase the photocatalytic activity of TiO2.
Results of the research showed that the synthesis of TiO2 in an ionic solution and the addition of cerium oxide to the structure of TiO2 decreased the particle size, increased the surface area, and slowed down the phase exchange from anatase to rutile at higher temperatures. As a result, it caused the creation of nanoparticles with higher thermal stability. High activity of the nanocomposite in the degradation of pollutants is explained by the unique structure of graphene, which increases adsorption on the catalyst surface and decreases the re-composition of ion carriers.
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Basics of TiO2 sunscreen

Ultraviolet (UV) Radiation

Ultraviolet radiation can be divided into three regions: UVA (320–400 nm), UVB(290–320 nm) and UVC (200–290 nm). Although UVC is the most damaging UV radiation, it is filtered out by the ozone layer in the stratosphere before reaching the earth’s surface. The radiation in the UVB region (partially filtered by ozone) can penetrate both the stratum corneum and the epidermis of human skin. It has
sufficient energy to cause damage, such as sunburn, to human skin. This is particularly true for fair-skinned individuals. The UVA radiation, which is unfiltered by ozone, has deeper penetration of human skin to the dermis; it, thereby, stimulates the formation of melanin and produces a tan, which acts as the first line of defense for the protection from sunburn. UVA radiation, therefore, is also called the “tanning region.” Although having considerably lower energy than UVB, UVA photons can cause delayed damages to the skin.

The fundamental function of a sunscreen is to serve as a filter that can prevent the penetration of ultraviolet radiation. The substances most commonly used in commercial sunscreen preparations include p-aminobenzoic acids (PABA), cinnamates, oxybenzone, salicylates, and metal oxides, such as TiO2 and ZnO. In addition to their ability to scatter sunlight, inorganic particles, such as TiO2, do
absorb strongly in the UVA and UVB regions.

Rutile and Anatase TiO2

In addition to its amorphous state, two of the most common crystalline forms of TiO2 are rutile and anatase. The two crystalline forms share many similarities, such as their physical appearance, refractive index, density, low toxicity, and high stability in the presence of strong acids and bases. As a physical blocker for sunlight, bot
crystalline forms would serve the purpose well. Their photochemical properties, however, are very different. TiO2 is a semiconductor. When a semiconductor particle absorbs light, it promotes an electron from its valence band to its conduction band, leading to a charge separation. In rutile TiO2, the charge separation is quickly diminished through a charge recombination within the particle and the energy is released as heat. This translates to a low photoactivity and an effective conversion of UV light into heat. As a result, any photoinduced reactions that can pose damage to the skin are avoided. The low photoactivity and its desirable UV absorption spectrum, which cover the entire erythemal curve make rutile TiO2 an ideal choice as UV blocker for sunscreen preparations.

For amorphous and anatase TiO2, the lifetime of the charge separation is much longer than that on a rutile particle. The electron and electron hole, therefore, have greater opportunity to undergo redox reactions on the surface; therefore, anatase has been extensively used for applications involving such electron transfer processes as
photocatalysis for environmental waste treatment and photovoltaic design for solar energy storage. Extensive reviews on these interesting topics are available. Due to their photoactivity, amorphous and anatase TiO2 are not suitable for sunscreen applications.

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Nanoparticles Used in Common Household Items Cause DNA Damage- Study.

Titanium dioxide (TiO2) nanoparticles, found in everything from cosmetics to sunscreen to paint to vitamins, caused systemic genetic damage in mice, according to a comprehensive study conducted by researchers at UCLA’s Jonsson Comprehensive Cancer Center.

The TiO2 nanoparticles induced single- and double-strand DNA breaks and also caused chromosomal damage as well as inflammation, all of which increase the risk for cancer. The UCLA study is the first to show that the nanoparticles had such an effect, said Robert Schiestl, a professor of pathology, radiation oncology and environmental health sciences, a Jonsson Cancer Center scientist and the study’s senior author.

Once in the system, the TiO2 nanoparticles accumulate in different organs because the body has no way to eliminate them. And because they are so small, they can go everywhere in the body, even through cells, and may interfere with sub-cellular mechanisms.

The study appeared the week of November 16 2009 in the journal Cancer Research.

In the past, these TiO2 nanoparticles have been considered non-toxic in that they do not incite a chemical reaction. Instead, it is surface interactions that the nanoparticles have within their environment- in this case inside a mouse — that is causing the genetic damage, Schiestl said. They wander throughout the body causing oxidative stress, which can lead to cell death.

It is a novel mechanism of toxicity, a physicochemical reaction, these particles cause in comparison to regular chemical toxins, which are the usual subjects of toxicological research, Schiestl said.

“The novel principle is that titanium by itself is chemically inert. However, when the particles become progressively smaller, their surface, in turn, becomes progressively bigger and in the interaction of this surface with the environment oxidative stress is induced,” he said. “This is the first comprehensive study of titanium dioxide nanoparticle-induced genotoxicity, possibly caused by a secondary mechanism associated with inflammation and/or oxidative stress. Given the growing use of these nanoparticles, these findings raise concern about potential health hazards associated with exposure.”

The manufacture of TiO2 nanoparticles is a huge industry, Schiestl said, with production at about two million tons per year. In addition to paint, cosmetics, sunscreen and vitamins, the nanoparticles can be found in toothpaste, food colorants, nutritional supplements and hundreds of other personal care products.

“It could be that a certain portion of spontaneous cancers are due to this exposure,” Schiestl said. “And some people could be more sensitive to nanoparticles exposure than others. “I believe the toxicity of these nanoparticles has not been studied enough.”

Schiestl said the nanoparticles cannot go through skin, so he recommends using a lotion sunscreen. Spray-on sunscreens could potentially be inhaled and the nanoparticles can become lodged in the lungs.

The mice were exposed to the TiO2 nanoparticles in their drinking water and began showing genetic damage on the fifth day. The human equivalent is about 1.6 years of exposure to the nanoparticles in a manufacturing environment. However, Schiestl said, it’s not clear if regular, everyday exposure in humans increases exponentially as continued contact with the nanoparticles occurs over time.

“These data suggest that we should be concerned about a potential risk of cancer or genetic disorders especially for people occupationally exposed to high concentrations of titanium dioxide nanoparticles, and that it might be prudent to limit their ingestion through non-essential drug additives, food colors, etc.,” the study states.

Next, Schiestl and his team will study exposure to the nanoparticles in mice that are deficient in DNA repair, to perhaps help find a way to predict which people might be particularly sensitive to them.

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Titanium Dioxide for Energy Storage Systems

Batteries could get a boost from an Oak Ridge National Laboratory discovery that increases power, energy density and safety while dramatically reducing charge time.

A team led by Hansan Liu, Gilbert Brown and Parans Paranthaman of the Department of Energy lab’s Chemical Sciences Division found that titanium dioxide creates a highly desirable material that increases surface area and features a fast charge-discharge capability for lithium ion batteries. Compared to conventional technologies, the differences in charge time and capacity are striking.

“We can charge our battery to 50 percent of full capacity in six minutes while the traditional graphite-based lithium ion battery would be just 10 percent charged at the same current,” Liu said.

Compared to commercial lithium titanate material, the ORNL compound also boasts a higher capacity – 256 vs. 165 milliampere hour per gram – and a sloping discharge voltage that is good for controlling state of charge. This characteristic combined with the fact oxide materials are extremely safe and long-lasting alternatives to commercial graphite make it well-suited for hybrid electric vehicles and other high-power applications.

The results, recently published in Advanced Materials, could also have special significance for applications in stationary energy storage systems for solar and wind power, and for smart grids. The titanium dioxide with a bronze polymorph also has the advantage of being potentially inexpensive, according to Liu.

At the heart of the breakthrough is the novel architecture of titanium dioxide, named mesoporous TiO2-B microspheres, which features channels and pores that allow for unimpeded flow of ions with a capacitor-like mechanism. Consequently, a lithium ion battery that substitutes TiO2-B for the graphite electrode charges and discharges quickly.

“Theoretical studies have uncovered that this pseudocapacitive behavior originates from the unique sites and energetics of lithium absorption and diffusion in TiO2-B structure,” the authors write in their paper, titled “Mesoporous TiO2-B Microspheres with Superior Rate Performance for Lithium Ion Batteries.”

Paranthaman noted that the microsphere shape of the material allows for traditional electrode fabrication and creates compact electrode layers. He also observed, however, that the production process of this material is complex and involves many steps, so more research remains to determine whether it is scalable.

Other authors of the paper are Zhonghe Bi, Xiao-Guang Sun, Raymond Unocic and Sheng Dai. The research was supported by DOE’s Office of Science, ORNL’s Laboratory Directed Research and Development program, and ORNL’s SHaRE User Facility, which is sponsored by Basic Energy Sciences.

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Catalytic Clothing that eats dirty air

HI-TECH denim jeans that use nanotechnology to stop air pollution are to go on show at the London Design Festival, which starts later this week.

Given recent reports that show London’s air to be among the filthiest in Europe, a clothing solution could be just up London’s street. Especially if that street is Oxford Street or any other area with a high number of pedestrians.

“A significant reduction in the level of air borne pollutants in a large city such as London could be achieved if, for every metre of pavement width, 30 people wearing Catalytic Clothes walked past each minute,” say developers Catalytic Clothing.

The jeans, or any other clothing fitted with the new technology, “harness the power of a photocatalyst to break down air borne pollutants,” by using light as an energy source.

“When the light shines on the photocatalyst, the electrons in the material are rearranged and they become more reactive,” adds the Catalytic Clothing website.

Further reactions then “cause pollutants to break down into non-harmful chemicals”.

Any material can become a pollution eater with the addition of a sort-of conditioner containing the photocatalysts, but different materials need different catalyst set-ups.

For the purposes of demonstration, jeans fit the bill since, “there are more pairs of jeans in existence than there are people on the earth,” as the Catalytic Clothing people put it.

The nanotech denim – developed by a team at Sheffield University and another at the London College of Fashion – has been formed into a display called The Field of Jeans for the London Design Festival, which runs from 17-25 September.

catalytic clothing faq

Hoover Air Purifier with TiO2 Technology

Hoover Air Purifier with TiO2 Technology – WH10600 (Hoover WH10600 air purifier) removes 99.9% of germs, bacteria and other microorganisms that pass through the UV light. It has the Titanium Dioxide (Ti02) coated screen that increases UV effectiveness. UV as well as Ti02 controls can be used during an entire year, especially during the flu period. There is a washable pre-filter integrated; it collects lint, pet hair, pollutants and other small particles. Depending on air quality the IntelliSense control system helps setting the fan speed to an appropriate level, so you don’t need to adjust it manually.

Features and Specifications

Hoover WH10600 is the air purifier that can be used in spaces of up to 79 sq ft. It helps remove allergens from the air making the air of your room or office fresh and the environment more desirable. This device has a Titanium Dioxide (Ti02) technology that helps removing 99.9% of airborne particles. They are collected to an elegant package and make this device to be a great part of your room design.

The Hepa filter collects 99.9% of dust and pollens, and thanks to the LED indicator, you will be informed when it is time to change the filter. The ionizer helps removing odors and airborne dust, pollen and germs; it is an environmentally friendly ionizer that uses no ozone for air cleaning.

The IntelliSense Control system sets the fan speed automatically depending on air quality. If needed, the unit can be adjusted choosing one of the three different fan speeds.

There is a remote control included that helps you making one-touch adjustments. You may want to set Hoover WH10600 for up to 24 hours – the device will shut off automatically which increases your comfort and allows you working on your tasks without returning to the unit. Moreover, the remote control can be used when the unit is 25 feet away from you.

Hoover WH10600 is 12.8 x 9.5 x 28 inches of size and weighs 13.3 pounds. Small in size and light this air purifier can be transported from one room to another easily.

Customer Reviews

To provide a better review of Hoover WH10600 air purifier, we provide a number of comments we’ve received from users or owners of this air purifier. Below you will find their positive and negative feedbacks that we hope will assist you making your choice.

Performance

Hoover WH10600 is recognized to be the best air purifier thanks to its great performance. As many users noticed, the air becomes fresh and the entire space is more desirable: “I have it in my office at work, and every time a co-worker comes in, they make mention of how fresh the air in my office smells. It’s a dramatic and noticeable difference from the air in the rest of the building.” We also received the following comment: “Its now been nearly 3 hours on the highest setting and everything “On” and I am definitely breathing cleaner air. I even let my roommate smoke in the condo to test it out, within 3 minutes and some Febreeze I couldn’t smell any smoke.”

We also received a couple of comments regarding how silent the air purifier works. As the reviewer noticed: “On level 1 the unit is virtually silent, 2 and especially 3, produce a bit of noise but the noise is comparable to other units I have used in the past.”

This air purifier can be also used in the kitchen. One lady said she tried using this air purifier while cooking bacon: “I have a small kitchen and even with turning on the stove hood vent, it can get kinda smokey especially when frying bacon. That’s why I thought this would be a great test. I won’t say it eliminated all of the smoke and odor, but it clearly did decrease the odor and amount of time it lasted throughout my kitchen and living room. I was impressed.”

The Pros:

The Titanium Dioxide coated screen for an increased UV effectiveness
99.9% or germs, bacteria and other pollutants removed
UV light removing particles passing through the screen under the UV light
IntelliSense Control system to follow air quality and adjust the unit accordingly

The Cons:

A couple of Hoover WH10600 users were not happy about the LED light. They commented it is too bright and may bother. We ensure that the light is not going to keep you awake in the night, and can be easily covered.

Overall Rating

After a deep analysis of Hoover Air Purifier with TiO2 Technology – WH10600 we affirm it to be the best air purifier. It’s compact and can be transformed easily. You may use it at home or in the office. The UV light and Ti02 technologies are other great features of this unit. With all these features we find it to be the best purifier within this price range.

If you are looking for in-depth reviews of all the best air purifiers such as the Rabbit Air BioGS SPA-421A, visit the Best air purifier website. We also reveal where to purchase the most popular air purifiers for up to 40% off.

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Artificial leaves could provide cheap energy

Scientists produced a design concept they hope will make it possible to manufacture fuel by photosynthesis.

If successful, it could help pave the way to a green and cost-efficient ”hydrogen economy”.

Photosynthesis enables plants to use energy from sunlight to convert carbon dioxide and water into organic compounds.

The chemistry involved is complex and has never been reproduced artificially,

Today, a team of Chinese scientists revealed the blueprint of an ”Artificial Inorganic Leaf” (AIL) based on Mother Nature’s own design.

A working version could be used to capture solar energy and use it efficiently to split water into oxygen and hydrogen, its component elements.

”Our results may represent an important first step towards the design of novel artificial solar energy transduction systems based on natural paradigms,” said lead researcher Dr Tongziang Fan, from Shanghai Jiaotong University in Shanghai.

Hydrogen is the ultimate clean fuel, producing nothing but water vapour when burned.

Some motor companies, such as Toyota, have already developed hydrogen-fuelled cars. Fuel cells, which generate electricity from a chemical reaction, also rely on hydrogen.

But the problem with hydrogen is that it is energy-consuming and costly to produce using traditional methods.

The new research was presented today at the annual meeting of the American Chemical Society in San Francisco.

Dr Fan’s team used the leaves of the Chinese plant Anemone vitifolia as a ”template” for the artificial leaf.

The concept employs tiny particles of titanium dioxide, a well known photocatalyst that allows sunlight to drive chemical reactions