Researchers split water into hydrogen, oxygen using light, nanoparticles

Researchers split water into hydrogen, oxygen using light, nanoparticles

Researchers from the University of Houston have found a catalyst that can quickly generate hydrogen from water using sunlight, potentially creating a clean and renewable source of energy.

Their research, published online Sunday in Nature Nanotechnology, involved the use of cobalt oxide nanoparticles to split water into hydrogen and oxygen.

Jiming Bao, lead author of the paper and an assistant professor in the Department of Electrical and Computer Engineering at UH, said the research discovered a new photocatalyst and demonstrated the potential of nanotechnology in engineering a material's property, although more work remains to be done.

Bao said photocatalytic water-splitting experiments have been tried since the 1970s, but this was the first to use cobalt oxide and the first to use neutral water under visible light at a high energy conversion efficiency without co-catalysts or sacrificial chemicals. The project involved researchers from UH, along with those from Sam Houston State University, the Chinese Academy of Sciences, Texas State University, Carl Zeiss Microscopy LLC, and Sichuan University.

Researchers prepared the nanoparticles in two ways, using femtosecond laser ablation and through mechanical ball milling. Despite some differences, Bao said both worked equally well.

Different sources of light were used, ranging from a laser to white light simulating the solar spectrum. He said he would expect the reaction to work equally well using natural sunlight.

Once the nanoparticles are added and light applied, the water separates into hydrogen and oxygen almost immediately, producing twice as much hydrogen as oxygen, as expected from the 2:1 hydrogen to oxygen ratio in H2O water molecules, Bao said.

The experiment has potential as a source of renewable fuel, but at a solar-to-hydrogen efficiency rate of around 5 percent, the conversion rate is still too low to be commercially viable. Bao suggested a more feasible efficiency rate would be about 10 percent, meaning that 10 percent of the incident solar energy will be converted to hydrogen chemical energy by the process.

Other issues remain to be resolved, as well, including reducing costs and extending the lifespan of cobalt oxide nanoparticles, which the researchers found became deactivated after about an hour of reaction.

"It degrades too quickly," said Bao, who also has appointments in materials engineering and the Department of Chemistry.

The work, supported by the Welch Foundation, will lead to future research, he said, including the question of why cobalt oxide nanoparticles have such a short lifespan, and questions involving chemical and electronic properties of the material.

University of Houston (2013, December 15). Researchers split water into hydrogen, oxygen using light, nanoparticles. ScienceDaily. Retrieved December 16, 2013, from http://www.sciencedaily.com­/releases/2013/12/131215160904.htm?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+sciencedaily%2Ftop_news%2Ftop_science+%28ScienceDaily%3A+Top+News+--+Top+Science%29

How Nanotechnology Can Change Life

Lowering the power consumption of CNT-based CMOS devices to subnanowatt

Researchers have demonstrated a new carbon nanotube (CNT)-based logic device that consumes just 0.1 nanowatts (nW) in its static ON and OFF states, representing the lowest reported value by 3 orders of magnitude for CNT-based CMOS logic devices. The device could serve as a building block for large-area, ultralow-power CNT logic circuits that can be used to realize a variety of nanoelectronics applications.

The researchers, Michael L. Geier, et al., at Northwestern University in Evanston, Illinois, and the University of Minnesota in Minneapolis, have published their paper on the subnanowatt CNT logic in a recent issue of Nano Letters.

'As the researchers explain, one of the biggest advantages of CMOS architecture is that it has intrinsically low power consumption. This benefit arises from the fact that, unlike other logic architectures, one of the two types of transistors (p-type or n-type) is turned off under steady state conditions in each logic gate in CMOS devices.

In order to fully take advantage of this potential for extremely low power consumption, the p-type and n-type transistors need to have precisely tuned and well-separated threshold voltages, which are the voltage levels that determine whether the device is ON or OFF. So far, this issue of the threshold voltages has not been addressed, and the researchers here identified it as the key challenge limiting the realization of highly integrated CNT-based CMOS electronics.

In their study, the researchers used a metal gate structure to achieve symmetric and clearly separated threshold voltages for p-type and n-type CNT transistors, resulting in the ultralow power consumption. In the static states, in which the device is either ON or OFF, power consumption is less than 0.1 nW. At the midpoint of the transfer state, when both p-type and n-type transistors are simultaneously in the ON state, the voltage reaches its peak at 10 nW.'

By connecting multiple CNT transistors in various configurations, the researchers demonstrated inverter, NAND and NOR logic gates. In the future, these gates can be integrated into complex circuits, where they can provide subnanowatt static power consumption along with the other advantages of CNTs, such as solution processability and flexibility.

More information: Michael L. Geier, et al. "Subnanowatt Carbon Nanotube Complementary Logic Enabled by Threshold Voltage Control." Nano Letters. DOI: 10.1021/nl402478p

Read more at: http://phys.org/news/2013-09-carbon-nanotube-logic-device-subnanowatt.html#jCp

Graphene could yield cheaper optical chips

Optoelectronic devices built from graphene could be much simpler in design than those made from other materials. If a method for efficiently depositing layers of graphene—a major area of research in materials science—can be found, it could ultimately lead to optoelectronic chips that are simpler and cheaper to manufacture.

"Another advantage, besides the possibility of making device fabrication simpler, is that the high mobility and ultrahigh carrier-saturation velocity of electrons in graphene makes for very fast detectors and modulators," says Dirk Englund, the Jamieson Career Development Assistant Professor of Electrical Engineering and Computer Science at MIT, who led the new research.

Graphene is also responsive to a wider range of light frequencies than the materials typically used in photodetectors, so graphene-based optoelectronic chips could conceivably use a broader-band optical signal, enabling them to move data more efficiently. "A two-micron photon just flies straight through a germanium photodetector," Englund says, "but it is absorbed and leads to measurable current—as we actually show in the paper—in graphene."

Read more at: http://phys.org/news/2013-09-graphene-yield-cheaper-optical-chips.html

More information: http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2013.253.html

Smartphone as a 'Microscope' to detect a single virus and nanoparticles

With the emerging of cutting edge technology of smartphone as Samsung Galaxy, Iphone etc, your smartphone now can see what the naked eye cannot: A single virus and bits of material less than one-thousandth of the width of a human hair.

Aydogan Ozcan, a professor of electrical engineering and bioengineering at the UCLA Henry Samueli School of Engineering and Applied Science, and his team have created a portable smartphone attachment that can be used to perform sophisticated field testing to detect viruses and bacteria without the need for bulky and expensive microscopes and lab equipment. The device weighs less than half a pound.

"This cellphone-based imaging platform could be used for specific and sensitive detection of sub-wavelength objects, including bacteria and viruses and therefore could enable the practice of nanotechnology and biomedical testing in field settings and even in remote and resource-limited environments," Ozcan said. "These results also constitute the first time that single nanoparticles and viruses have been detected using a cellphone-based, field-portable imaging system."

The new research, published on Sept. 9 in the American Chemical Society's journal ACS Nano, comes on the heels of Ozcan's other recent inventions, including a cellphone camera-enabled sensor for allergens in food products and a smart phone attachment that can conduct common kidney tests.

Capturing clear images of objects as tiny as a single virus or a nanoparticle is difficult because the optical signal strength and contrast are very low for objects that are smaller than the wavelength of light.

In the ACS Nano paper, Ozcan details a fluorescent microscope device fabricated by a 3-D printer that contains a color filter, an external lens and a laser diode. The diode illuminates fluid or solid samples at a steep angle of roughly 75 degrees. This oblique illumination avoids detection of scattered light that would otherwise interfere with the intended fluorescent image.

Using this device, which attaches directly to the camera module on a smartphone, Ozcan's team was able to detect single human cytomegalovirus (HCMV) particles. HCMV is a common virus that can cause birth defects such as deafness and brain damage and can hasten the death of adults who have received organ implants, who are infected with the HIV virus or whose immune systems otherwise have been weakened. A single HCMV particle measures about 150-300 nanometers; a human hair is roughly 100,000 nanometers thick.

In a separate experiment, Ozcan's team also detected nanoparticles -- specially marked fluorescent beads made of polystyrene -- as small as 90-100 nanometers.

To verify these results, researchers in Ozcan's lab used other imaging devices, including a scanning electron microscope and a photon-counting confocal microscope. These experiments confirmed the findings made using the new cellphone-based imaging device.

Ozcan is the principal investigator on the research. The first author of ACS Nano the paper is Qingshan Wei, a postdoctoral researcher in Ozcan's lab and at UCLA's California NanoSystems Institute (CNSI), where Ozcan is associate director. Other co-authors include Hangfei Qi and Ting-Ting Wu of the UCLA Department of Molecular and Medical Pharmacology; Wei Luo, Derek Tseng, Zhe Wan and Zoltan Gorocs of the UCLA Electrical Engineering Department; So Jung Ki of the UCLA Department of Chemistry and Biochemistry; Laurent Bentolila of CNSI and the UCLA Department of Chemistry and Biochemistry; and Ren Sun of the UCLA Department of Molecular and Medical Pharmacology and CNSI.

More information: pubs.acs.org/doi/pdfplus/10.1021/nn4037706

Journal reference: ACS Nano  

Provided by University of California, Los Angeles

Read more at: http://phys.org/news/2013-09-smartphone-microscope-virus-nanoparticles.html#jCp

Have you ever seen an atom ?

A 3D microscopic slicing show the atomic arrangement in a platinum nanoparticle.

Progress in Molecular Nanotechnology

Stanford scientists use DNA to assemble a transistor from graphene

Stanford scientists use DNA to assemble a transistor from graphene

DNA meets electronics

DNA is the blueprint for life. Could it also become the template for making a new generation of computer chips based not on silicon, but on an experimental material known as graphene?

That's the theory behind a process that Stanford chemical engineering professor Zhenan Bao reveals in Nature Communications.

Bao and her co-authors, former post-doctoral fellows Anatoliy Sokolov and Fung Ling Yap, hope to solve a problem clouding the future of electronics: consumers expect silicon chips to continue getting smaller, faster and cheaper, but engineers fear that this virtuous cycle could grind to a halt.

Why has to do with how silicon chips work.

Everything starts with the notion of the semiconductor, a type of material that can be induced to either conduct or stop the flow of electricity. Silicon has long been the most popular semiconductor material used to make chips.

The basic working unit on a chip is the transistor. Transistors are tiny gates that switch electricity on or off, creating the zeroes and ones that run software.

To build more powerful chips, designers have done two things at the same time: they've shrunk transistors in size and also swung those gates open and shut faster and faster.

The net result of these actions has been to concentrate more electricity in a diminishing space. So far that has produced small, faster, cheaper chips. But at a certain point, heat and other forms of interference could disrupt the inner workings of silicon chips.

"We need a material that will let us build smaller transistors that operate faster using less power," Bao said.

Graphene has the physical and electrical properties to become a next-generation semiconductor material – if researchers can figure out how to mass-produce it.

Graphene is a single layer of carbon atoms arranged in a honeycomb pattern. Visually it resembles chicken wire. Electrically this lattice of carbon atoms is an extremely efficient conductor.

Bao and other researchers believe that ribbons of graphene, laid side-by-side, could create semiconductor circuits. Given the material's tiny dimensions and favorable electrical properties, graphene nano ribbons could create very fast chips that run on very low power, she said.

"However, as one might imagine, making something that is only one atom thick and 20 to 50 atoms wide is a significant challenge," said co-author Sokolov.

To handle this challenge, the Stanford team came up with the idea of using DNA as an assembly mechanism.

Physically, DNA strands are long and thin, and exist in roughly the same dimensions as the graphene ribbons that researchers wanted to assemble.

Chemically, DNA molecules contain carbon atoms, the material that forms graphene.

The real trick is how Bao and her team put DNA's physical and chemical properties to work.

The researchers started with a tiny platter of silicon to provide a support (substrate) for their experimental transistor. They dipped the silicon platter into a solution of DNA derived from bacteria and used a known technique to comb the DNA strands into relatively straight lines.

Next, the DNA on the platter was exposed to a copper salt solution. The chemical properties of the solution allowed the copper ions to be absorbed into the DNA.

Next the platter was heated and bathed in methane gas, which contains carbon atoms. Once again chemical forces came into play to aid in the assembly process. The heat sparked a chemical reaction that freed some of the carbon atoms in the DNA and methane. These free carbon atoms quickly joined together to form stable honeycombs of graphene.

"The loose carbon atoms stayed close to where they broke free from the DNA strands, and so they formed ribbons that followed the structure of the DNA," Yap said.

So part one of the invention involved using DNA to assemble ribbons of carbon. But the researchers also wanted to show that these carbon ribbons could perform electronic tasks. So they made transistors on the ribbons.

"We demonstrated for the first time that you can use DNA to grow narrow ribbons and then make working transistors," Sokolov said.

The paper drew praise from UC Berkeley associate professor Ali Javey, an expert in the use of advanced materials and next-generation electronics.

"This technique is very unique and takes advantage of the use of DNA as an effective template for controlled growth of electronic materials," Javey said. "In this regard the project addresses an important research need for the field."

Bao said the assembly process needs a lot of refinement. For instance, not all of the carbon atoms formed honeycombed ribbons a single atom thick. In some places they bunched up in irregular patterns, leading the researchers to label the material graphitic instead of graphene.

Even so, the process, about two years in the making, points toward a strategy for turning this carbon-based material from a curiosity into a serious contender to succeed silicon.

"Our DNA-based fabrication method is highly scalable, offers high resolution and low manufacturing cost," said co-author Yap. "All these advantages make the method very attractive for industrial adoption."

Source : http://www.eurekalert.org/pub_releases/2013-09/ssoe-ssu090613.php

Dye-sensitized solar cells with carbon nanotube transparent electrodes offer significant cost savings

March 15, 2012

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Carbon nanotube electrodes. The use of carbon nanotubes has a significant cost advantage. However, in earlier designs (left), the carbon nanotubes degraded through chemical processes (e-: electrons, I3-: ions in the liquid). Using a thin protective layer of titanium oxide now stabilizes the nanotubes (right), increasing the performance of these cells. Credit: 2011 AIP

Solar energy is one of the most promising forms of renewable energy, but the high cost of conventional solar cells has so far limited its popularity. To increase the competitiveness of solar energy, scientists have turned to the development of dye-sensitized solar cells — solar cells that use low-cost organic dyes and titanium dioxide (TiO2) nanoparticles in place of expensive semiconductor and rare earth elements to absorb sunlight. Zhaohong Huang at the A*STAR Institute of Materials Research and Engineering and co-workers have now reduced the cost of dye-sensitized solar cells even further by replacing indium tin oxide (ITO) — the standard material for transparent electrodes — with carbon nanotubes.

A typical dye-sensitized solar cell comprises a porous layer of TiO2 nanoparticles immersed in an organic dye. The dye absorbs the sunlight and converts the energy into electricity, which flows into the TiO2 nanoparticles. The sun-facing side of the solar cell is usually covered with a transparent electrode that carries the charge carriers away from the TiO2 and out of the solar cell. “Unfortunately, ITO electrodes are brittle and crack easily,” says Huang. “They are also expensive and could incur up to 60% of the total cost of the dye-sensitized solar cell.”

Huang and his team therefore replaced the ITO electrode with a thin film of carbon nanotubes. Carbon nanotubes conduct electricity and are almost transparent, flexible and strong, which make them the ideal material for transparent electrodes. The only drawback is that photo-generated charge carriers in the nanotube may recombine with ions in the dye, which reduces the power conversion efficiency of the solar cell.

To overcome this problem, Huang and his team placed a TiO2 thin film in between the carbon nanotube thin film and the porous layer. They found that the performance of dye-sensitized solar cells with TiO2 thin film was significantly better than those without. However, they also found that the solar conversion efficiency of their new dye-sensitized solar cells was only 1.8%, which is lower than that of conventional solar cells using ITO electrodes. This is due to the higher electrical resistances and reduced optical transparency of the carbon nanotube films, which limits the amount of sunlight entering the cell.

“We are now studying different ways to enhance the conductivity and transparency of the films,” says Huang. “Furthermore, we are planning to replace the bottom platinum electrode with carbon nanotube thin film to reduce the cost of dye-sensitized solar cells further.”

If successful, the results could have a great impact on the cost and stability of dye-sensitized solar cells.

More information: Research article in Applied Physics Letters.

Provided by Agency for Science, Technology and Research (A*STAR)

Source : http://www.physorg.com/news/2012-03-dye-sensitized-solar-cells-carbon-nanotube.html

Solar cell turns windows into generators

March 20, 2012

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(PhysOrg.com) -- Imagine a world where the windows of high-rise office buildings are powerful energy producers, offering its inhabitants much more than some fresh air, light and a view.

For the past four years a team of researchers from Flinders University has been working to make this dream a reality – and now the notion of solar-powered windows could be coming to a not too distant future near you.

As part of his just-completed PhD, Dr. Mark Bissett from the School of Chemical and Physical Sciences has developed a revolutionary solar cell using carbon nanotubes.

A promising alternative to traditional silicon-based solar cells, carbon nanotubes are cheaper to make and more efficient to use than their energy-sapping, silicon counterparts.

“Solar power is actually the most expensive type of renewable energy – in fact the silicon solar cells we see on peoples’ roofs are very expensive to produce and they also use a lot of electricity to purify,” Dr. Bissett said.

“The overall efficiency of silicon solar cells are about 10 per cent and even when they’re operating at optimal efficiency it could take eight to 15 years to make back the energy that it took to produce them in the first place because they’re produced using fossil fuels,” he said.

Dr. Bissett said the new, low-cost carbon nanotubes are transparent, meaning they can be “sprayed” onto windows without blocking light, and they are also flexible so they can be weaved into a range of materials including fabric – a concept that is already being explored by advertising companies.

While the amount of power generated by solar windows would not be enough to completely offset the energy consumption of a standard office building, Dr. Bissett said they still had many financial and environmental advantages.

“In a new building, or one where the windows are being replaced anyway, adding transparent solar cells to the glass would be a relatively small cost since the cost of the glass, frames and installation would be the same with or without the solar component,” Dr. Bissett said.

“It’s basically like tinting the windows except they’re able to produce electricity, and considering office buildings don’t have a lot of roof space for solar panels it makes sense to utilise the many windows they do have instead.”

Dr. Bissett said the technology mimics photosynthesis, the process whereby plants obtain energy from the sun.

“A solar cell is created by taking two sheets of electrically conductive glass and sandwiching a layer of functionalized single-walled carbon nanotubes between the glass sheets,” he said.

“When light shines on the cell, electrons are generated within the carbon nanotubes and these can be used to power electrical devices.”

Although small prototypes have been developed in the lab, he said the next step would be to test the carbon cells on an “industrial stage”.

If all goes to plan, the material could be on the market within 10 years.

“When we first started the research we had no idea if it would work because we were the first in the world to try it so it’s pretty exciting that we’ve proved the concept, and hopefully it will be commercially available in a few year’s time,” Dr. Bissett said.

Dr. Bissett is a winner of Flinders inaugural Best Student Paper Award, a now annual program which aims to recognise excellence in student research across the University.

Provided by Flinders University

Source : http://www.physorg.com/news/2012-03-solar-cell-windows.html

Dr. Hildy -- Nanoethics: The Ethical and Social Implications of Nanotechnology

September 28, 2011 -- One Cell One Light Radio with Dr. Hildegarde Staninger, RIET-1 Guest: Dr. Daniel F. Moore http://danielfmoore.com

Source: http://www.nanopaprika.eu

Nanotechnology may speed up drug testing

Nanotechnology may speed up drug testing

ScienceDaily (Dec. 19, 2011) — Testing the effectiveness of new pharmaceuticals may get faster thanks to a new technique incorporating quantum dots developed at the University of Central Florida.

Some drug testing can take a decade or more, but UCF associate professor Swadeshmukul Santra and his team have created an electronic quantum dots (Qdots) probe that "lights up" when a drug it is delivering attaches to cancer cells.

The research appears online in this month's Biomaterials.

A researcher can use a microscope to see where and how much of the drug has been delivered because the probe emits a reddish color under special lighting or via MRI because of its optical and magnetic components.

As the drug testing continues, images can be taken over and over without any loss of optical or MRI signal. Researchers can then measure the size of the tumor and number of cancer cells that "light up" compared with the original untreated tumor.

Source: University of Central Florida (2011, December 19). Nanotechnology may speed up drug testing. ScienceDaily. Retrieved January 9, 2012, from http://www.sciencedaily.com­/releases/2011/12/111219152721.htm