#Toward a low-cost'artificial leaf'that produces clean hydrogen fuel For years scientists have been pursuing artificial leaf technology a green approach to making hydrogen fuel that copies plants'ability to convert sunlight into a form of energy they can use.
Now one team reports progress toward a stand-alone system that lends itself to large-scale low-cost production.
They describe their nanowire mesh design in the journal ACS Nano. Peidong Yang Bin Liu and colleagues note that harnessing sunlight to split water
and harvest hydrogen is one of the most intriguing ways to achieve clean energy. Automakers have started introducing hydrogen fuel cell vehicles
which only emit water when driven. But making hydrogen which mostly comes from natural gas requires electricity from conventional carbon dioxide-emitting power plants.
Producing hydrogen at low cost from water using the clean energy from the sun would make this form of energy
which could also power homes and businesses far more environmentally friendly. Building on a decade of work in this area Yang's team has taken one more step toward this goal.
The researchers took a page from the paper industry using one of its processes to make a flat mesh out of light-absorbing semiconductor nanowires that
Scientists create multifunctional nanotubes using nontoxic materials A doctoral student in materials science at Technische Universitat Darmstadt is making multifunctional nanotubes of goldith the help of Vitamin c and other harmless substances.
The doctoral student in the research group of Professor Wolfgang Ensinger in the Department of Material Analysis is working on making nanotubes of gold.
She precipitates the precious metal from an aqueous solution onto a pretreated film with many tiny channels.
The metal on the walls of the channels adopts the shape of nanotubes; the film is dissolved then.
"The chemicals that are used usually for this were just too toxic for me.""She preferred not to use cyanide, formaldehyde, arsenic and heavy metal salts.
She was inspired by a journal article by researchers who achieved silver precipitation using coffee. Felix also used coffee in her first experiments.
a postdoctoral researcher and supervisor of Felix'Phd thesis. The gold ions that are dissolved in the precipitation bath are transformed into metallic gold after absorbing electrons.
thus saving energy. Furthermore, as opposed to other methods no expensive devices are required. The film with the nanochannels is placed merely in the precipitation bath."
"It's really unbelievable that aqueous solutions and simple basic chemicals can produce such precise nanostructures"says Münch."
"Green meets Nano"is a motto of the researchers at the TU. The only thing that is not green in the procedure is the film that is used as the template, notes Ensinger.
Although tests with bio-based plastics are already on the agenda, the films still consist of polycarbonate also made or of polyethylene terephthalate (PET).
In order to create the miniature plastic channels that define the shape, a round film is bombarded vertically with an ion beam.
Each ion leaves a straight track in the film which then becomes a small hole,
or, when seen through the microscope: a channel that is then etched. Its diameter can be set precisely-down to far less than 100 nanometers.
The gold nanotubes are thus several hundred times finer than a human hair. Their wall thickness depends both on the duration of precipitation and on the gold concentration of the original solution.
After the film is dissolved, the result is-depending on the experimental conditions-a collection of individual nanotubes or an array of hundreds of thousands of interconnected tubes.
The crux of the technique: an ion accelerator is needed to generate an ion beam. The TU scientists found the ideal partner for their research in the GSI Helmholtz Center for Heavy ion Research at the outskirts of Darmstadt;
but the GSI's large-scale accelerator was not suitable for subsequent commercial use for financial reasons.
a film roughly the size of a sheet of paper costs only a few euros. Ensinger says that the price of gold is not a factor
because the amounts that are required are small:""With 1 gram of gold, we could make a nanotube for literally every person on earth."
"Although a single tube is not useful for anyone, not much material is needed for microsensors, miniature through-flow reactors,
or other potential applications. Ensinger's team has tested already successfully one use of the gold nanotubes:
they are suitable for building sensors to measure hydrogen peroxide. This chemical damages nerve cells and apparently plays a role in neurodegenerative diseases such as Alzheimer's and Parkinson's.
A microsensor that can measure hydrogen peroxide in the human body would thus be practical both in medical research as well as for diagnosis. The conversion of hydrogen peroxide to water,
catalyzed by the gold releases electrons generates an easily measurable electric current. The gold nanotubes conduct electricity especially well due to their one-dimensional structure.
In addition, they are relatively long and are thus more durable than normal nanoparticles.""Nano meets Life"is the second motto of the TU Materials science researchers.
For example, they are thinking about also using the nanotubes to measure blood sugar.""A subcutaneous sensor could save diabetes patients from having to constantly prick their fingers"thinks Ensinger.
The green method of production also has advantages here because the components of such implants should be produced with as few toxic chemicals as possible."
"This completes the circle, "says the TU professor, combining the two mottos:""Green meets Nano meets Life
#Uniform nanowire arrays for science and manufacturing Defect-free nanowires with diameters in the range of 100 nanometers (nm) hold significant promise for numerous in demand applications including printable
transistors for flexible electronics high-efficiency light-emitting diodes resonator-based mass sensors and integrated near-field optoelectronic tips for advanced scanning tip microscopy.
That promise cannot be realized however unless the wires can be fabricated in large uniform arrays using methods compatible with high-volume manufacture.
To date that has not been possible for arbitrary spacings in ultra-high vacuum growth. Now NIST's PML's Optoelectronic Manufacturing Group has achieved a breakthrough:
Reproducible synthesis of gallium nitride nanowires with controlled size and location on silicon substrates. The result was achieved by improving selective wire-growth processes to produce one nanowire of controlled diameter per mask-grid opening over a range of diameters from 100 nm to 200 nm.
Ordered arrays with a variety of spacings were fabricated. In the near term the research will be used to create a wafer-scale arrays of probes for devices that examine the surface
and near-surface properties of materials to optimize nanowire LEDS and to produce nanowires with controlled diameter for a collaborative project involving printable transistors for millimeter-wave reconfigurable antennae e
#Designing complex structures beyond the capabilities of conventional lithography Gold nanoparticles smaller than 10 nanometers spontaneously self-organize in entirely new ways
when trapped inside channel-like templates. A new study shows that this feature could facilitate easier nanoscale manufacturing of biosensors and plasmonic devices with intricate high-density surface structures.
Generating surface patterns at scales of 10 nanometers and below is difficult with current technology.
An international team led by Joel Yang from the A*STAR Institute of Materials Research and Engineering in Singapore is helping to circumvent this limitation using a technique known as'directed self-assembly of nanoparticles'(DSA-n). This approach takes spherical nanoparticles that spontaneously organize into ordered two-dimensional films
when inserted into lithographically defined templates. The templates impose geometric constraints that force the films to organize into specific nanoscale patterns.
Most patterns produced by DSA-n however are simple periodic arrangements. To broaden this technique's capabilities researchers are exploring'structure transitions'that occur
when template constraints become comparable to the size of the nanoparticles. At these dimensions the small spheres can dislocate from typical periodic positions
and reorient into unpredictable new geometries. Previous studies have used real-time video microscopy to capture structure transitions in microscale colloids
but direct imaging of sub-10-nanometer particles is nearly impossible. That's where we came up with the idea of using templates based on channels with gradually varying widths says co-author Mohamed Asbahi.
With this system we can track the self-assembly of the nanoparticles according to the space accessible to them.
Using electron-beam lithography techniques the team carved out an array of inward tapering trenches designed to fit 1 to 3 rows of gold nanoparticles.
After depositing a monolayer of 8-nanometer particles in the template they used scanning electron microscopy to identify any emergent width-dependent patterns.
Between periodically ordered rows the researchers saw clear evidence of transition state zones regions where the tiny spheres buckle out of alignment
and gradually take on new triangular packing patterns. After analyzing the transition states with computational Monte carlo simulations Yang and co-workers identified several dominant recurrent patterns with different geometries from typical DSA-n depositions.
Because the conditions needed to generate these patterns can be predicted mathematically the team is confident these findings can have practical surface engineering applications.
The success of DSA-n depends on the positioning accuracy of the particles says Yang. By exploiting the rich set of structural geometries that exist between ordered states we can design templates that guide particles into complex periodic and nonperiodic structures s
#Lengthening the life of high capacity silicon electrodes in rechargeable lithium batteries A new study will help researchers create longer-lasting higher-capacity lithium rechargeable batteries
which are used commonly in consumer electronics. In a study published in the journal ACS Nano researchers showed how a coating that makes high capacity silicon electrodes more durable could lead to a replacement for lower-capacity graphite electrodes.
Understanding how the coating works gives us an indication of the direction we need to move in to overcome the problems with silicon electrodes said materials scientist Chongmin Wang of the Department of energy's Pacific Northwest National Laboratory.
Thanks to its high electrical capacity potential silicon is one of the hottest things in lithium ion battery development these days Replacing the graphite electrode in rechargeable lithium batteries with silicon could increase the capacity tenfold making
them last many hours longer before they run out of juice. The problem? Silicon electrodes aren't very durable#after a few dozen recharges they can no longer hold electricity.
That's partly due to how silicon takes up lithium#like a sponge. When charging lithium infiltrates the silicon electrode.
The lithium causes the silicon electrode to swell up to three times its original size. Possibly as a result of the swelling or for other unknown reasons the silicon fractures and breaks down.
Researchers have been using electrodes made up of tiny silicon spheres about 150 nanometers wide#about a thousand times smaller than a human hair#to overcome some of the limitations of silicon as an electrode.
The small size lets silicon charge quickly and thoroughly#an improvement over earlier silicon electrodes#but only partly alleviates the fracturing problem.
Last year materials scientist Chunmei Ban and her colleagues at the National Renewable energy Laboratory in Golden Colorado and the University of Colorado Boulder found that they could cover silicon nanoparticles with a rubberlike coating made from aluminum glycerol.
The coated silicon particles lasted at least five times longer#uncoated particles died by 30 cycles but the coated ones still carried a charge after 150 cycles.
Researchers did not know how this coating improved the performance of the silicon nanoparticles. The nanoparticles naturally grow a hard shell of silicon oxide on their surface much like stainless steel forms a protective layer of chromium oxide on its surface.
No one understood if the oxide layer interfered with electrode performance and if so how the rubbery coating improved it.
To better understand how the coating worked PNNL's Wang and colleagues including Ban turned to expertise and a unique instrument at EMSL DOE's Environmental Molecular Sciences Laboratory a DOE Office of Science User Facility at PNNL.
Ban's group#which developed the coating for silicon electrodes called alucone and is currently the only group that can create alucone-coated silicon particles#took high magnification images of the particles in an electron microscope.
But Wang's team has a microscope that can view the particles in action while they are being charged and discharged.
So Yang He from the University of Pittsburgh explored the coated silicon nanoparticles in action at EMSL.
The team discovered that without the alucone coating the oxide shell prevents silicon from expanding
and limits how much lithium the particle can take in when a battery charges. At the same time they found that the alucone coating softens the particles making it easier for them to expand
and shrink with lithium. And the microscopic images revealed something else#the rubbery alucone replaces the hard oxide.
In the future the researchers would like to develop an easier method of coating the silicon nanoparticles. Explore further:
Silicon sponge improves lithium-ion battery performance More information: Yang He Daniela Molina Piper Menggu Jonathan J. Travis Steven M. George Se-Hee Lee Arda Genc Lee Pullan Jun Liu
In situ Transmission Electron microscopy Probing of Native Oxide and Artificial Layers on Silicon Nanoparticles for Lithium ion batteries ACS Nano October 27 2014 DOI:
This innovation in nanotechnology won't soak up enough carbon to solve global warming researchers say. However it will provide an environmentally friendly low-cost way to make nanoporous graphene for use in supercapacitors-devices that can store energy and release it rapidly.
Such devices are used in everything from heavy industry to consumer electronics. The findings were published just in Nano Energy by scientists from the OSU College of Science OSU College of Engineering Argonne National Laboratory the University of South Florida and the National Energy technology Laboratory in Albany Ore.
The work was supported by OSU. In the chemical reaction that was developed the end result is nanoporous graphene a form of carbon that's ordered in its atomic and crystalline structure.
It has an enormous specific surface area of about 1900 square meters per gram of material. Because of that it has an electrical conductivity at least 10 times higher than the activated carbon now used to make commercial supercapacitors.
There are other ways to fabricate nanoporous graphene but this approach is faster has little environmental impact
and costs less said Xiulei (David) Ji an OSU assistant professor of chemistry in the OSU College of Science
and lead author on the study. The product exhibits high surface area great conductivity and most importantly it has a fairly high density that is comparable to the commercial activated carbons.
And the carbon source is carbon dioxide which is a sustainable resource to say the least Ji said.
and zinc metals a combination discovered for the first time. These are heated to a high temperature in the presence of a flow of carbon dioxide to produce a controlled metallothermic reaction.
and nanoporous graphene a pure form of carbon that's remarkably strong and can efficiently conduct heat and electricity.
By comparison other methods to make nanoporous graphene often use corrosive and toxic chemicals in systems that would be challenging to use at large commercial levels.
Most commercial carbon supercapacitors now use activated carbon as electrodes but their electrical conductivity is very low Ji said.
We want fast energy storage and release that will deliver more power and for that purpose the more conductive nanoporous graphene will work much better.
This solves a major problem in creating more powerful supercapacitors. A supercapacitor is a type of energy storage device
but it can be recharged much faster than a battery and has a great deal more power. They are used mostly in any type of device where rapid power storage
and short but powerful energy release is needed. They are being used in consumer electronics and have applications in heavy industry with the ability to power anything from a crane to a forklift.
A supercapacitor can capture energy that might otherwise be wasted such as in braking operations. And their energy storage abilities may help smooth out the power flow from alternative energy systems such as wind energy.
They can power a defibrillator open the emergency slides on an aircraft and greatly improve the efficiency of hybrid electric automobiles.
Nanoporous carbon materials can also adsorb gas pollutants work as environmental filters or be used in water treatment.
The uses are expanding constantly and have been constrained mostly by their cost. Explore further: Trees go high-tech:
Process turns cellulose into energy storage device e
#Nanotubes may restore sight to blind retinas The aging process affects everything from cardiovascular function to memory to sexuality.
Most worrisome for many however is the potential loss of eyesight due to retinal degeneration. New progress towards a prosthetic retina could help alleviate conditions that result from problems with this vital part of the eye.
An encouraging new study published in Nano Letters describes a revolutionary novel device tested on animal-derived retinal models that has the potential to treat a number of eye diseases.
The proof-of-concept artificial retina was developed by an international team led by Prof. Yael Hanein of Tel aviv University's School of Electrical engineering and head of TAU's Center for Nanoscience and Nanotechnology and including researchers from TAU the Hebrew University of Jerusalem and Newcastle University.
Compared to the technologies tested in the past this new device is more efficient more flexible and can stimulate neurons more effectively said Prof.
Hanein. The new prosthetic is compact unlike previous designs that used wires or metals while attempting to sense light.
Additionally the new material is capable of higher spatial resolution whereas older designs struggled in this area.
The researchers combined semiconductor nanorods and carbon nanotubes to create a wireless light-sensitive flexible film that could potentially replace a damaged retina.
The researchers tested the new device with chick retinas which were not yet light sensitive to prove that the artificial retina is able to induce neuronal activity in response to light.
or older who have damage to a specific part of the retina will stand to benefit from the nanotube device
According to TAU doctoral student and research team member Dr. Lilach Bareket there are already medical devices that attempt to treat visual impairment by sending sensory signals to the brain.
While scientists are trying different approaches to develop an implant that can see light and send visual signals to a person's brain to counter the effects of AMD
We hope our carbon nanotube and semiconductor nanorod film will serve as a compact replacement for damaged retinas.
We are still far away from actually replacing the damaged retina said Dr. Bareket. But we have demonstrated now that this new material stimulates neurons efficiently and wirelessly with light.
which require wiring to outside energy or light sources this is a groundbreaking new direction. The research team received funding for their study from the Israel Ministry of Science and Technology the European Research Council and the Biotechnology and Biological sciences Research Council.
Explore further: Artificial retina could someday help restore vision More information: pubs. acs. org/doi/full/10.1021/nl503430 0
#Scanning tunnelling microscopy: Computer simulations sharpen insights into molecules The resolution of scanning tunnelling microscopes can be improved dramatically by attaching small molecules or atoms to their tip.
The resulting images were the first to show the geometric structure of molecules and have generated a lot of interest among scientists over the last few years.
Scientists from Forschungszentrum Jülich and the Academy of Sciences of the Czech republic in Prague have used now computer simulations to gain deeper insights into the physics of these new imaging techniques.
Flexibly bound molecules at the microscope tip can be utilized as tailor-made sensors and signal transducers that are able to make the atomic structure visible nevertheless.
In the last few years, such atomic sensors have also proven useful for work with atomic force microscopes.
Then, in May 2014, scientists from the University of California, Irvine, showed for the first time that these sensors can also be used to improve signals in a related imaging mode known as inelastic electron tunnelling spectroscopy.
it is the vibration of the sensor molecule against the microscope tip that reacts sensitively to the surface potential of the scanned sample."
"We believe that the results of this work are an important contribution to the use of inelastic electron tunnelling spectroscopy that will allow the technique to be used as an additional source of information in materials science
#Nanomaterials to preserve ancient works of art Little would we know about history if it weren't for books and works of art.
But as time goes by conserving this evidence of the past is becoming more and more of a struggle.
In an effort to overcome the limitations of traditional restoration techniques the team has developed promising nanomaterials
and history so fascinating and their trade weighs quite heavily in today's economies. In 2013 the global art market generated some EUR 47.42 billion according to the European Fine art Foundation.
The most ancient works of art are increasingly suffering the ravages of time while traditional restoration techniques pose serious problems in terms of physicochemical compatibility with substances contained in artefacts and toxicity.
The materials commonly used for restoration such as coatings of synthetic polymers or inorganic materials have a different composition than that of the original artefacts
which causes them to alter their main properties. This is where the NANOFORART (Nanomaterials for the conservation
and preservation of movable and immovable artworks) project comes in. The three-year project which ends this month has developed advanced nanomaterials for preventive conservation of works of art.
In this exclusive interview for the research*eu results magazine Prof. Piero Baglioni sheds light on the main benefits of these new products the advances made by his team
and the expected commercialisation date and expands on what's to come under Horizon 2020.
The lack of physicochemical compatibility between restoration materials and artefacts along with the former's toxicity were the two main aspects that prompted us to propose the NANOFORART project.
This involved nanomaterials that are physico-chemically compatible with the components of works of art
and are either not toxic or have reduced a significantly toxicity level compared to traditional restoration materials like solvents
What's so innovative about the solutions you propose? The advanced nanomaterials we have been working on allow for a more precise control of the restoration intervention for example controlled cleaning can be carried out using microemulsions and chemical hydrogels instead of traditional cleaning methods.
The approaches we propose are more reliable than traditional ones and in some cases allow for a gradual and slower (safer) restoration process.
or exhibit a complex composition they can be classified as composite materials which means that you need materials science
and colloid and surface science to understand and eventually rescue these materials from possible degradation processes.
but almost exclusively to develop advanced diagnostic techniques for the characterisation of works of art and their degradation processes.
We could compare preservation of cultural heritage to medicine where the works of art play the role of the patients:
diagnostic techniques are fundamental to understanding the disease (degradation processes) but must then be complemented by the development of medicines (advanced restoration materials) to cure the patient (restore the work of art).
These are the main reasons that so far have slowed down advances in conservation techniques. What were the main difficulties you faced in the development of these new materials?
The number of degradation processes affecting a large variety of works of art requires the development of new methodologies and materials
whose formulation poses significant challenges in terms of human resources. What do you expect in terms of performance compared to existing technologies?
and solutions provided by advanced materials and colloid sciences and more generally nanosciences. These materials are able to resolve degradation issues
which is key to the long-term stability of the treated works of art and their availability to future generations.
There are plenty of examples showing how traditional materials can be detrimental to works of art for instance wall paintings treated with acrylic
and vinyl polymers that seriously damage the painting and in many cases have led to the loss of painted surfaces.
What are the most promising materials you developed The project has been successful in producing and effectively testing several new materials for the conservation of works of art four
The first is the dispersion of calcium hydroxide nanoparticles in short chain alcohols for the consolidation of wall paintings plasters and stone.
The second is the dispersion of alkaline nanoparticles in either short chain alcohols or water for the ph control of movable works of art such as paper parchment and leather.
We also came up with nanostructured cleaning fluids such as oil-in-water microemulsions for the removal of dirt and unwanted coatings on works of art.
One of the main advantages in using these fluids is that they exhibit a depressed eco-toxicological impact with respect to traditional solvent blends
Dispersions of nanoparticles of calcium hydroxide for the consolidation of wall paintings plasters and stone are already available to conservators worldwide under the trademark Nanorestore.
Nanoparticles for the ph control of movable works of art (e g. paper wood canvas) have been branded under the trademark Nanorestore Paper;
gels and microemulsions for the cleaning of wall and easel paintings have been branded as Nanorestore Gel and Nanorestore Cleaning.
and materials for modern and contemporary works of art such as acrylic paintings plastic sculptures and composite works that include metal textiles polymers etc.
This is the reason why we are proposing a new project within the Horizon 2020 call named NANORESTART (Nanomaterials for the RESTORARTION of the works of modern ART to highlight the new start with respect to classic art conservation) that aims
to conserve modern/contemporary works of art. In order to address this challenge we have created a unique partnership that groups research institutions and materials science experts together with high-profile museums conservation centres and experienced professionals in the field of modern art preservation.
Leading industrial partners have also been involved to provide the scalability of the restoration materials we will develop and the transfer of technology to meet market needs e
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