Category Archives: energy

Hector Barron Escobar and his virtual nanomaterial atomic models for the oil, mining, and energy industries

I think there’s some machine translation at work in the Aug. 27, 2015 news item about Hector Barron Escobar on Azonano,

By using supercomputers the team creates virtual atomic models that interact under different conditions before being taken to the real world, allowing savings in time and money.

With the goal of potentiate the oil, mining and energy industries, as well as counteract the emission of greenhouse gases, the nanotechnologist Hector Barron Escobar, designs more efficient and profitable nanomaterials.

The Mexican who lives in Australia studies the physical and chemical properties of platinum and palladium, metal with excellent catalytic properties that improve processes in petrochemistry, solar cells and fuel cells, which because of their scarcity have a high and unprofitable price, hence the need to analyze their properties and make them long lasting.

Structured materials that the specialist in nanotechnology designs can be implemented in the petrochemical and automotive industries. In the first, they accelerate reactions in the production of hydrocarbons, and in the second, nanomaterials are placed in catalytic converters of vehicles to transform the pollutants emitted by combustion into less harmful waste.

An August 26, 2015 Investigación y Desarrollo press release on Alpha Galileo, which originated the news item, continues Barron Escobar’s profile,

PhD Barron Escobar, who majored in physics at the National University of Mexico (UNAM), says that this are created by using virtual supercomputers to interact with atomic models under different conditions before being taken to the real world.

Barron recounts how he came to Australia with an invitation of his doctoral advisor, Amanda Partner with whom he analyzed the electronic properties of gold in the United States.

He explains that using computer models in the Virtual Nanoscience Laboratory (VNLab) in Australia, he creates nanoparticles that interact in different environmental conditions such as temperature and pressure. He also analyzes their mechanical and electronic properties, which provide specific information about behavior and gives the best working conditions. Together, these data serve to establish appropriate patterns or trends in a particular application.

The work of the research team serves as a guide for experts from the University of New South Wales in Australia, with which they cooperate, to build nanoparticles with specific functions. “This way we perform virtual experiments, saving time, money and offer the type of material conditions and ideal size for a specific catalytic reaction, which by the traditional way would cost a lot of money trying to find what is the right substance” Barron Escobar comments.

Currently he designs nanomaterials for the mining company Orica, because in this industry explosives need to be controlled in order to avoid damaging the minerals or the environment.

Research is also immersed in the creation of fuel cells, with the use of the catalysts designed by Barron is possible to produce more electricity without polluting.

Additionally, they enhance the effectiveness of catalytic converters in petrochemistry, where these materials help accelerate oxidation processes of hydrogen and carbon, which are present in all chemical reactions when fuel and gasoline are created. “We can identify the ideal particles for improving this type of reactions.”

The nanotechnology specialist also seeks to analyze the catalytic properties of bimetallic materials like titanium, ruthenium and gold, as their reaction according to size, shape and its components.

Escobar Barron chose to study nanomaterials because it is interesting to see how matter at the nano level completely changes its properties: at large scale it has a definite color, but keep another at a nanoscale, besides many applications can be obtained with these metals.

For anyone interested in Orica, there’s more here on their website; as for Dr. Hector Barron Escobar, there’s this webpage on  Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO) website.

Corrections: Hybrid Photonic-Nanomechanical Force Microscopy uses vibration for better chemical analysis

*ETA August 27, 2015: I’ve received an email from one of the paper’s authors (RH Farahi of the US Oak Ridge National Laboratory [ORNL]) who claims some inaccuracies in this piece.  The news release supplied by the University of Central Florida states that Dr. Tetard led the team and that is not so. According to Dr. Farahi, she had a postdoctoral position on the team which she left two years ago. You might also get the impression that some of the work was performed at the University of Central Florida. That is not so according to Dr. Farahi.  As a courtesy Dr. Tetard was retained as first author of the paper.

I suspect some of the misunderstanding was due to overeagerness and/or time pressures. Whoever wrote the news release may have made some assumptions. It’s very easy to make a mistake when talking to an ebullient scientist who can unintentionally lead you to believe something that’s not so. I worked in a high tech company and believed that there was some new software being developed which turned out to be a case of high hopes. Luckily, I said something that triggered a rapid rebuttal to the fantasies. Getting back to this situation, other contributing factors could include the writer not having time to get the news release reviewed the scientist or the scientist skimming the release and missing a few bits due to time pressure.

The August 10, 2015 ORNL news release with all the correct details has been added to the end of this post.*

A researcher at the University of Central Florida (UCF) has developed a microscope that uses vibrations for better analysis of chemical composition. From an Aug. 10, 2015 news item on Nanowerk,

It’s a discovery that could have promising implications for fields as varied as biofuel production, solar energy, opto-electronic devices, pharmaceuticals and medical research.

“What we’re interested in is the tools that allow us to understand the world at a very small scale,” said UCF professor Laurene Tetard, formerly of the Oak Ridge National Laboratory. “Not just the shape of the object, but its mechanical properties, its composition and how it evolves in time.”

An Aug. 10, 2015 UCF news release (also on EurekAlert), which originated the news item, describes the limitations of atomic force microscopy and gives a few details about the hybrid microscope (Note: A link has been removed),

For more than two decades, scientists have used atomic force microscopy – a probe that acts like an ultra-sensitive needle on a record player – to determine the surface characteristics of samples at the microscopic scale. A “needle” that comes to an atoms-thin point traces a path over a sample, mapping the surface features at a sub-cellular level [nanoscale].

But that technology has its limits. It can determine the topographical characteristics of [a] sample, but it can’t identify its composition. And with the standard tools currently used for chemical mapping, anything smaller than roughly half a micron is going to look like a blurry blob, so researchers are out of luck if they want to study what’s happening at the molecular level.

A team led by Tetard has come up with a hybrid form of that technology that produces a much clearer chemical image. As described Aug. 10 in the journal Nature Nanotechnology, Hybrid Photonic-Nanomechanical Force Microscopy (HPFM) can discern a sample’s topographic characteristics together with the chemical properties at a much finer scale.

The HPFM method is able to identify materials based on differences in the vibration produced when they’re subjected to different wavelengths of light – essentially a material’s unique “fingerprint.”

“What we are developing is a completely new way of making that detection possible,” said Tetard, who has joint appointments to UCF’s Physics Department, Material Science and Engineering Department and the NanoScience Technology Center.

The researchers proved the effectiveness of HPFM while examining samples from an eastern cottonwood tree, a potential source of biofuel. By examining the plant samples at the nanoscale, the researchers for the first time were able to determine the molecular traits of both untreated and chemically processed cottonwood inside the plant cell walls.

The research team included Tetard; Ali Passian, R.H. Farahi and Brian Davison, all of Oak Ridge National Laboratory; and Thomas Thundat of the University of Alberta.

Long term, the results will help reveal better methods for producing the most biofuel from the cottonwood, a potential boon for industry. Likewise, the new method could be used to examine samples of myriad plants to determine whether they’re good candidates for biofuel production.

Potential uses of the technology go beyond the world of biofuel. Continued research may allow HPFM to be used as a probe so, for instance, it would be possible to study the effect of new treatments being developed to save plants such as citrus trees from bacterial diseases rapidly decimating the citrus industry, or study fundamental photonically-induced processes in complex systems such as in solar cell materials or opto-electronic devices.

Here’s a link to and a citation for the paper,

Opto-nanomechanical spectroscopic material characterization by L. Tetard, A. Passian, R. H. Farahi, T. Thundat, & B. H. Davison. Nature Nanotechnology (2015) doi:10.1038/nnano.2015.168 Published online 10 August 2015

This paper is behind a paywall.

*ETA August 27, 2015:

August 10, 2015 ORNL news release (Note: Funding information and a link to the paper [previously given] have been removed):

A microscope being developed at the Department of Energy’s Oak Ridge National Laboratory will allow scientists studying biological and synthetic materials to simultaneously observe chemical and physical properties on and beneath the surface.

The Hybrid Photonic Mode-Synthesizing Atomic Force Microscope is unique, according to principal investigator Ali Passian of ORNL’s Quantum Information System group. As a hybrid, the instrument, described in a paper published in Nature Nanotechnology, combines the disciplines of nanospectroscopy and nanomechanical microscopy.

“Our microscope offers a noninvasive rapid method to explore materials simultaneously for their chemical and physical properties,” Passian said. “It allows researchers to study the surface and subsurface of synthetic and biological samples, which is a capability that until now didn’t exist.”

ORNL’s instrument retains all of the advantages of an atomic force microscope while simultaneously offering the potential for discoveries through its high resolution and subsurface spectroscopic capabilities.

“The originality of the instrument and technique lies in its ability to provide information about a material’s chemical composition in the broad infrared spectrum of the chemical composition while showing the morphology of a material’s interior and exterior with nanoscale – a billionth of a meter – resolution,” Passian said.

Researchers will be able to study samples ranging from engineered nanoparticles and nanostructures to naturally occurring biological polymers, tissues and plant cells.

The first application as part of DOE’s BioEnergy Science Center was in the examination of plant cell walls under several treatments to provide submicron characterization. The plant cell wall is a layered nanostructure of biopolymers such as cellulose. Scientists want to convert such biopolymers to free the useful sugars and release energy.

An earlier instrument, also invented at ORNL, provided imaging of poplar cell wall structures that yielded unprecedented topological information, advancing fundamental research in sustainable biofuels.

Because of this new instrument’s impressive capabilities, the researcher team envisions broad applications.
“An urgent need exists for new platforms that can tackle the challenges of subsurface and chemical characterization at the nanometer scale,” said co-author Rubye Farahi. “Hybrid approaches such as ours bring together multiple capabilities, in this case, spectroscopy and high-resolution microscopy.”

Looking inside, the hybrid microscope consists of a photonic module that is incorporated into a mode-synthesizing atomic force microscope. The modular aspect of the system makes it possible to accommodate various radiation sources such as tunable lasers and non-coherent monochromatic or polychromatic sources.

Graphene gains metallic powers after laser-burning

Rice University (Texas, US) researchers have developed a technique for embedding metallic nanoparticles in graphene with the hope of one day replacing platinum catalysts in fuel cells. From an August 20, 2015 news item on ScienceDaily,

Laser-induced graphene, created by the Rice lab of chemist James Tour last year, is a flexible film with a surface of porous graphene made by exposing a common plastic known as polyimide to a commercial laser-scribing beam. The researchers have now found a way to enhance the product with reactive metals.

An August 20, 2015 Rice University news release (also on EurekAlert), which originated the news item, provides further description,

With the discovery, the material that the researchers call “metal oxide-laser induced graphene” (MO-LIG) becomes a new candidate to replace expensive metals like platinum in catalytic fuel-cell applications in which oxygen and hydrogen are converted to water and electricity.

“The wonderful thing about this process is that we can use commercial polymers, with simple inexpensive metal salts added,” Tour said. “We then subject them to the commercial laser scriber, which generates metal nanoparticles embedded in graphene. So much of the chemistry is done by the laser, which generates graphene in the open air at room temperature.

“These composites, which have less than 1 percent metal, respond as ‘super catalysts’ for fuel-cell applications. Other methods to do this take far more steps and require expensive metals and expensive carbon precursors.”

Initially, the researchers made laser-induced graphene with commercially available polyimide sheets. Later, they infused liquid polyimide with boron to produce laser-induced graphene with a greatly increased capacity to store an electrical charge, which made it an effective supercapacitor.

For the latest iteration, they mixed the liquid and one of three concentrations containing cobalt, iron or molybdenum metal salts. After condensing each mixture into a film, they treated it with an infrared laser and then heated it in argon gas for half an hour at 750 degrees Celsius.

That process produced robust MO-LIGs with metallic, 10-nanometer particles spread evenly through the graphene. Tests showed their ability to catalyze oxygen reduction, an essential chemical reaction in fuel cells. Further doping of the material with sulfur allowed for hydrogen evolution, another catalytic process that converts water into hydrogen, Tour said.

“Remarkably, simple treatment of the graphene-molybdenum oxides with sulfur, which converted the metal oxides to metal sulfides, afforded a hydrogen evolution reaction catalyst, underscoring the broad utility of this approach,” he said.

Here’s a link to and a citation for the paper,

In situ Formation of Metal Oxide Nanocrystals Embedded in Laser-Induced Graphene by Ruquan Ye, Zhiwei Peng, Tuo Wang, Yunong Xu, Jibo Zhang, Yilun Li, Lizanne G. Nilewski, Jian Lin, and James M. Tour. ACS Nano, Just Accepted Manuscript DOI: 10.1021/acsnano.5b04138 Publication Date (Web): August 18, 2015
Copyright © 2015 American Chemical Society

This paper is open access provided you have an ACS ID, which is a free registration. ACS is the American Chemical Society.

Carbon capture with ‘diamonds from the sky’

Before launching into the latest on a new technique for carbon capture, it might be useful to provide some context. Arthur Neslen’s March 23, 2015 opinion piece outlines the issues and notes that one Norwegian Prime Minister resigned when coalition government partners attempted to build gas power plants without carbon capture and storage facilities (CCS), Note : A link has been removed,

At least 10 European power plants were supposed to begin piping their carbon emissions into underground tombs this year, rather than letting them twirl into the sky. None has done so.

Missed deadlines, squandered opportunities, spiralling costs and green protests have plagued the development of carbon capture and storage (CCS) technology since Statoil proposed the concept more than two decades ago.

But in the face of desperate global warming projections the CCS dream still unites Canadian tar sands rollers with the UN’s Intergovernmental Panel on Climate Change (IPCC), and Shell with some environmentalists.

With 2bn people in the developing world expected to hook up to the world’s dirty energy system by 2050, CCS holds out the tantalising prospect of fossil-led growth that does not fry the planet.

“With CCS in the mix, we can decarbonise in a cost-effective manner and still continue to produce, to some extent, our fossil fuels,” Tim Bertels, Shell’s Glocal CCS portfolio manager told the Guardian. “You don’t need to divest in fossil fuels, you need to decarbonise them.”

The technology has been gifted “a very significant fraction” of the billions of dollars earmarked by Shell for clean energy research, he added. But the firm is also a vocal supporter of public funding for CCS from carbon markets, as are almost all players in the industry.

Enthusiasm for this plan is not universal (from Neslen’s opinion piece),

Many environmentalists see the idea as a non-starter because it locks high emitting power plants into future energy systems, and obstructs funding for the cheaper renewables revolution already underway. “CCS is is completely irrelevant,” said Jeremy Rifkin, a noted author and climate adviser to several governments. “I don’t even think about it. It’s not going to happen. It’s not commercially available and it won’t be commercially viable.”

I recommend reading Neslen’s piece for anyone who’s not already well versed on the issues. He uses Norway as a case study and sums up the overall CCS political situation this way,

In many ways, the debate over carbon capture and storage is a struggle between two competing visions of the societal transformation needed to avert climate disaster. One vision represents the enlightened self-interest of a contributor to the problem. The other cannot succeed without eliminating its highly entrenched opponent. The battle is keenly fought by technological optimists on both sides. But if Norway’s fractious CCS experience is any indicator, it will be decided on the ground by the grimmest of realities.

On that note of urgency, here’s some research on carbon dioxide (CO2) or, more specifically, carbon capture and utilization technology, from an Aug. 19, 2015 news item on Nanowerk,,

Finding a technology to shift carbon dioxide (CO2), the most abundant anthropogenic greenhouse gas, from a climate change problem to a valuable commodity has long been a dream of many scientists and government officials. Now, a team of chemists says they have developed a technology to economically convert atmospheric CO2    directly into highly valued carbon nanofibers for industrial and consumer products.

An Aug. 19, 2015 American Chemical Society (ACS) news release (also on EurekAlert), which originated the news time, expands on the theme,

The team will present brand-new research on this new CO2 capture and utilization technology at the 250th National Meeting & Exposition of the American Chemical Society (ACS). ACS is the world’s largest scientific society. The national meeting, which takes place here through Thursday, features more than 9,000 presentations on a wide range of science topics.

“We have found a way to use atmospheric CO2 to produce high-yield carbon nanofibers,” says Stuart Licht, Ph.D., who leads a research team at George Washington University. “Such nanofibers are used to make strong carbon composites, such as those used in the Boeing Dreamliner, as well as in high-end sports equipment, wind turbine blades and a host of other products.”

Previously, the researchers had made fertilizer and cement without emitting CO2, which they reported. Now, the team, which includes postdoctoral fellow Jiawen Ren, Ph.D., and graduate student Jessica Stuart, says their research could shift CO2 from a global-warming problem to a feed stock for the manufacture of in-demand carbon nanofibers.

Licht calls his approach “diamonds from the sky.” That refers to carbon being the material that diamonds are made of, and also hints at the high value of the products, such as the carbon nanofibers that can be made from atmospheric carbon and oxygen.

Because of its efficiency, this low-energy process can be run using only a few volts of electricity, sunlight and a whole lot of carbon dioxide. At its root, the system uses electrolytic syntheses to make the nanofibers. CO2 is broken down in a high-temperature electrolytic bath of molten carbonates at 1,380 degrees F (750 degrees C). Atmospheric air is added to an electrolytic cell. Once there, the CO2 dissolves when subjected to the heat and direct current through electrodes of nickel and steel. The carbon nanofibers build up on the steel electrode, where they can be removed, Licht says.

To power the syntheses, heat and electricity are produced through a hybrid and extremely efficient concentrating solar-energy system. The system focuses the sun’s rays on a photovoltaic solar cell to generate electricity and on a second system to generate heat and thermal energy, which raises the temperature of the electrolytic cell.

Licht estimates electrical energy costs of this “solar thermal electrochemical process” to be around $1,000 per ton of carbon nanofiber product, which means the cost of running the system is hundreds of times less than the value of product output.

“We calculate that with a physical area less than 10 percent the size of the Sahara Desert, our process could remove enough CO2 to decrease atmospheric levels to those of the pre-industrial revolution within 10 years,” he says. [emphasis mine]

At this time, the system is experimental, and Licht’s biggest challenge will be to ramp up the process and gain experience to make consistently sized nanofibers. “We are scaling up quickly,” he adds, “and soon should be in range of making tens of grams of nanofibers an hour.”

Licht explains that one advance the group has recently achieved is the ability to synthesize carbon fibers using even less energy than when the process was initially developed. “Carbon nanofiber growth can occur at less than 1 volt at 750 degrees C, which for example is much less than the 3-5 volts used in the 1,000 degree C industrial formation of aluminum,” he says.

A low energy approach that cleans up the air by converting greenhouse gases into useful materials and does it quickly is incredibly exciting. Of course, there are a few questions to be asked. Are the research outcomes reproducible by other teams? Licht notes the team is scaling the technology up but how soon can we scale up to industrial strength?

Solar cells from the University of Alberta?

Trevor Robb’s Aug. 7, 2015 article for the Edmonton Sun (Alberta, Canada) features a research team dedicated to producing better solar cells and a facility (nanoFAB) at the University of Alberta,

But in an energy rich province like Alberta — known for its oil and gas sector — [JIllian] Buriak [chemistry professor at the University of Alberta, Canada Research chair of nanomaterials] is on a mission to shed some light on another form of energy Alberta is known for, solar energy.

So her team is dedicated to producing flexible, recyclable plastic solar cells that can be printed just like a newspaper.

In fact, they’ve already begun doing so.

In order to produce the sheet-like solar cells, Buriak and her team use nothing more than simple commercial laminators and a spray gun, not unlike something you would use to paint a car.

“We run them through this laminator that squeezes them down and turns them from something that’s not conducting to something that’s really conducting,” said Buriak.

“You could incorporate it into clothing, you could incorporate it into books, into window blinds, or unroll it on a tent when you’re camping,” said Buriak. “You could use it anywhere. Anything from simple funny things to cafe umbrellas that could allow you to charge electronic devices, to large scale things in developing countries; large scale solar cells that you could simply carry on your backpack, unroll at a medical clinic, and suddenly you have instant power.”

There are more details about Buriak’s work and information about nanoFAB in Robb’s article. As for technical information, the best I can find is in an Aug. 29, 2013 University of Alberta news release (also on EurekAlert),

University of Alberta researchers have found that abundant materials in the Earth’s crust can be used to make inexpensive and easily manufactured nanoparticle-based solar cells.

The discovery, several years in the making, is an important step forward in making solar power more accessible to parts of the world that are off the traditional electricity grid or face high power costs, such as the Canadian North, said researcher Jillian Buriak, a chemistry professor and senior research officer of the National Institute for Nanotechnology based on the U of A campus.
Buriak and her team have designed nanoparticles that absorb light and conduct electricity from two very common elements: phosphorus and zinc. Both materials are more plentiful than scarce materials such as cadmium and are free from manufacturing restrictions imposed on lead-based nanoparticles.

Buriak collaborated with U of A post-doctoral fellows Erik Luber of the U of A Faculty of Engineering and Hosnay Mobarok of the Faculty of Science to create the nanoparticles. The team was able to develop a synthetic method to make zinc phosphide nanoparticles, and demonstrated that the particles can be dissolved to form an ink and processed to make thin films that are responsive to light.

Buriak and her team are now experimenting with the nanoparticles, spray-coating them onto large solar cells to test their efficiency. The team has applied for a provisional patent and has secured funding to enable the next step to scale up manufacture.

I wonder if this news article by Robb is an attempt by Buriak to attract interest from potential investors?

Perovskite, nanorods, and solar energy

As the authors, Azhar Fakharuddin, Rajan Jose, and Thomas Brown, note in an Aug. 7, 2015 Nanowerk Spotlight article , securing energy sources is a global pursuit and pervoskite (a new wonder material for solar cells) has presented a challenge (Note: A link has been removed),

Energy security has been a top global concern motivating researchers to seek it from renewable and cost-effective resources. Solar cells, that convert sun light into electricity, hold the promise as a cheap energy alternative. The silicon and thin film photovoltaic industry have taken many strides to lower energy prices; however, continued research is required in order to extensively compete with fossil fuels.

The development of perovskite solar cells, first reported in 2009 (and with a record power conversion efficiency of 20.1 percent so far), is a possible route towards high efficiency photovoltaics that are also cost-effectiveness, owing to to their easy-processing from solution.

Question marks have however remained on their stability.

The authors (members of a research team) have recently published a paper about a method that could make perovskite solar cells more stable,

Now, a research team from University Malaysia Pahang, focussing on renewable energy, working in in collaboration with scientists from University of Rome ‘Tor Vergata’, Italy, has developed the world’s first nanorod-based perovskite solar module.

Among the three types of electron transport layers investigated, the nanorod-based devices retained the original efficiency values even after 2500 hours of shelf-life investigation, a protocol used to gauge initial stability and indoor lifetime performance.
The device employing a conventional TiO2 nanoparticle material showed nearly 60% of original performance, whereas planar devices employing a compact TiO2 layer showed below 5% of original performance, measured at similar experimental conditions.
A chemical analysis of the devices hinted that the peculiar conformation of nanorods facilitates a stable perovskite phase due to their inherent stability and macroporous nature.

If you want more detail, the research team’s Nanowerk Spotlight article is the place to look (it’s almost like a Reddit session except there’s no ‘ask me anything’ option). There’s also the team’s paper,

Vertical TiO2 Nanorods as a Medium for Stable and High-Efficiency Perovskite Solar Modules by Azhar Fakharuddin, Francesco Di Giacomo, Alessandro L. Palma, Fabio Matteocci, Irfan Ahmed, Stefano Razza, Alessandra D’Epifanio, Silvia Licoccia, Jamil Ismail, Aldo Di Carlo, Thomas M. Brown, and Rajan Jose. ACS Nano, Article ASAP DOI: 10.1021/acsnano.5b03265 Publication Date (Web): July 24, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.

One final note, I’ve been meaning to publish a post about perovskite-based solar cells for a while now as the material seems to be sweeping the solar energy community and, now, it’s done.

Saving silver; a new kind of electrode

An Aug. 1, 2015 news item on Nanotechnology Now highlights work from Germany’s Helmholtz-Zentrum Berlin für Materialien und Energie (Helmholtz Zentrum Berlin),

The electrodes for connections on the “sunny side” of a solar cell need to be not just electrically conductive, but transparent as well. As a result, electrodes are currently made either by using thin strips of silver in the form of a coarse-meshed grid squeegeed onto a surface, or by applying a transparent layer of electrically conductive indium tin oxide (ITO) compound. Neither of these are ideal solutions, however. This is because silver is a precious metal and relatively expensive, and silver particles with nanoscale dimensions oxidise particularly rapidly; meanwhile, indium is one of the rarest elements on earth crust and probably will only continue to be available for a few more years.

Manuela Göbelt on the team of Prof. Silke Christiansen has now developed an elegant new solution using only a fraction of the silver and entirely devoid of indium to produce a technologically intriguing electrode. The doctoral student initially made a suspension of silver nanowires in ethanol using wet-chemistry techniques. She then transferred this suspension with a pipette onto a substrate, in this case a silicon solar cell. As the solvent is evaporated, the silver nanowires organise themselves into a loose mesh that remains transparent, yet dense enough to form uninterrupted current paths.

A July 31, 2015 Helmholtz Zentrum Berlin press release (also on EurekAlert), which originated the news item, describes the work in more detail,

Subsequently, Göbelt used an atomic layer deposition technique to gradually apply a coating of a highly doped wide bandgap semiconductor known as AZO. AZO consists of zinc oxide that is doped with aluminium. It is much less expensive than ITO and just as transparent, but not quite as electrically conductive. This process caused tiny AZO crystals to form on the silver nanowires, enveloped them completely, and finally filled in the interstices. The silver nanowires, measuring about 120 nanometres in diameter, were covered with a layer of about 100 nanometres of AZO and encapsulated by this process.

Quality map calculated

Measurements of the electrical conductivity showed that the newly developed composite electrode is comparable to a conventional silver grid electrode. However, its performance depends on how well the nanowires are interconnected, which is a function of the wire lengths and the concentration of silver nanowires in the suspension. The scientists were able to specify the degree of networking in advance with computers. Using specially developed image analysis algorithms, they could evaluate images taken with a scanning electron microscope and predict the electrical conductivity of the electrodes from them.

“We are investigating where a given continuous conductive path of nanowires is interrupted to see where the network is not yet optimum”, explains Ralf Keding. Even with high-performance computers, it still initially took nearly five days to calculate a good “quality map” of the electrode. The software is now being optimised to reduce the computation time. “The image analysis has given us valuable clues about where we need to concentrate our efforts to increase the performance of the electrode, such as increased networking to improve areas of poor coverage by changing the wire lengths or the wire concentration in solution”, says Göbelt.

Practical aternative to conventional electrodes

“We have developed a practical, cost-effective alternative to conventional screen-printed grid electrodes and to the common ITO type that is threatened however by material bottlenecks”, says Christiansen, who heads the Institute of Nanoarchitectures for Energy Conversion at HZB and additionally directs a project team at the Max Planck Institute for the Science of Light (MPL).

Only a fraction of silver, nearly no shadow effects

The new electrodes can actually be made using only 0.3 grams of silver per square metre, while conventional silver grid electrodes require closer to between 15 and 20 grams of silver. In addition, the new electrode casts a considerably smaller shadow on the solar cell. “The network of silver nanowires is so fine that almost no light for solar energy conversion is lost in the cell due to the shadow”, explains Göbelt. On the contrary, she hopes “it might even be possible for the silver nanowires to scatter light into the solar cell absorbers in a controlled fashion through what are known as plasmonic effects.”

Here’s a link to and a citation for the paper,

Encapsulation of silver nanowire networks by atomic layer deposition for indium-free transparent electrodes by Manuela Göbelt, Ralf Keding, Sebastian W. Schmitt, Björn Hoffmann, Sara Jäckle, Michael Latzel, Vuk V. Radmilović, Velimir R. Radmilović,  Erdmann Spiecker, and Silke Christiansen. Nano Energy Volume 16, September 2015, Pages 196–206 doi:10.1016/j.nanoen.2015.06.027

This paper is behind a paywall.

Smart windows from Texas (US)

I’ve been waiting for ‘smart’ windows and/or self-cleaning windows since 2008. While this research on ‘smart’ windows at the University of Texas at Austin looks promising I suspect it will be years before these things are in the marketplace. A July 22, 2015 news item on Nanotechnology Now announces the latest research,

Researchers in the Cockrell School of Engineering at The University of Texas at Austin are one step closer to delivering smart windows with a new level of energy efficiency, engineering materials that allow windows to reveal light without transferring heat and, conversely, to block light while allowing heat transmission, as described in two new research papers.

By allowing indoor occupants to more precisely control the energy and sunlight passing through a window, the new materials could significantly reduce costs for heating and cooling buildings.

In 2013, chemical engineering professor Delia Milliron and her team became the first to develop dual-band electrochromic materials that blend two materials with distinct optical properties for selective control of visible and heat-producing near-infrared light (NIR). In a 2013 issue of Nature, Milliron’s research group demonstrated how, using a small jolt of electricity, a nanocrystal material could be switched back and forth, enabling independent control of light and energy.

A July 23, 2015 University of Texas at Austin news release, which originated the news item, provides more details about the research which has spawned two recently published papers,

The team now has engineered two new advancements in electrochromic materials — a highly selective cool mode and a warm mode — not thought possible several years ago.

The cool mode material is a major step toward a commercialized product because it enables control of 90 percent of NIR and 80 percent of the visible light from the sun and takes only minutes to switch between modes. The previously reported material could require hours.

To achieve this high performance, Milliron and a team, including Cockrell School postdoctoral researcher Jongwook Kim and collaborator Brett Helms of the Lawrence Berkeley National Lab, developed a new nanostructured architecture for electrochromic materials that allows for a cool mode to block near-infrared light while allowing the visible light to shine through. This could help reduce energy costs for cooling buildings and homes during the summer. The researchers reported the new architecture in Nano Letters on July 20.

“We believe our new architected nanocomposite could be seen as a model material, establishing the ideal design for a dual-band electrochromic material,” Milliron said. “This material could be ideal for application as a smart electrochromic window for buildings.”

In the paper, the team demonstrates how the new material can strongly and selectively modulate visible light and NIR by applying a small voltage.

To optimize the performance of electrochromics for practical use, the team organized the two components of the composite material to create a porous interpenetrating network. The framework architecture provides channels for transport of electronic and ionic change. This organization enables substantially faster switching between modes.
Smart Window

The researchers are now working to produce a similarly structured nanocomposite material by simple methods, suitable for low-cost manufacturing.

In a second research paper, Milliron and her team, including Cockrell School graduate student Clayton Dahlman, have reported a proof-of-concept demonstrating how they can achieve optical control properties in windows from a well-crafted, single-component film. The concept includes a simple coating that creates a new warm mode, in which visible light can be blocked, while near-infrared light can enter. This new setting could be most useful on a sunny winter day, when an occupant would want infrared radiation to pass into a building for warmth, but the glare from sunlight to be reduced.

In this paper, published in the Journal of the American Chemical Society, Milliron proved that a coating containing a single component ­— doped titania nanocrystals — could demonstrate dynamic control over the transmittance of solar radiation. Because of two distinct charging mechanisms found at different applied voltages, this material can selectively block visible or infrared radiation.

“These two advancements show that sophisticated dynamic control of sunlight is possible,” Milliron said. “We believe our deliberately crafted nanocrystal-based materials could meet the performance and cost targets needed to progress toward commercialization of smart windows.”

Interestingly, the news release includes this statement,

The University of Texas at Austin is committed to transparency and disclosure of all potential conflicts of interest. The lead UT investigator involved with this project, Delia Milliron, is the chief scientific officer and owns an equity position in Heliotrope Technologies, an early-stage company developing new materials and manufacturing processes for electrochromic devices with an emphasis on energy-saving smart windows. Milliron is associated with patents at Lawrence Berkeley National Laboratory licensed to Heliotrope Technologies. Collaborator Brett Helms serves on the scientific advisory board of Heliotrope and owns equity in the company.

Here are links to and citations for the two papers,

Nanocomposite Architecture for Rapid, Spectrally-Selective Electrochromic Modulation of Solar Transmittance by Jongwook Kim, Gary K. Ong, Yang Wang, Gabriel LeBlanc, Teresa E. Williams, Tracy M. Mattox, Brett A. Helms, and Delia J. Milliron. Nano Lett., Article ASAP DOI: 10.1021/acs.nanolett.5b02197 Publication Date (Web): July 20, 2015

Copyright © 2015 American Chemical Society

Spectroelectrochemical Signatures of Capacitive Charging and Ion Insertion in Doped Anatase Titania Nanocrystals by Clayton J. Dahlman, Yizheng Tan, Matthew A. Marcus, and Delia J. Milliron. J. Am. Chem. Soc., 2015, 137 (28), pp 9160–9166 DOI: 10.1021/jacs.5b04933 Publication Date (Web): July 8, 2015

Copyright © 2015 American Chemical Society

These papers are behind paywalls.

University of Toronto researchers combine 2 different materials for new hyper-efficient, light-emitting, hybrid crystal

The Sargent Group at the University of Toronto has been quite active with regard to LEDs (light-emitting diodes) and with quantum dots. Their latest work is announced in a July 16, 2015 news item on Nanotechnology Now (Note: I had to include the ‘oatmeal cookie and chocolate chips’ analogy in the first paragraph as it’s referred to subsequently),

It’s snack time: you have a plain oatmeal cookie, and a pile of chocolate chips. Both are delicious on their own, but if you can find a way to combine them smoothly, you get the best of both worlds.

Researchers in The Edward S. Rogers Sr. Department of Electrical & Computer Engineering [University of Toronto] used this insight to invent something totally new: they’ve combined two promising solar cell materials together for the first time, creating a new platform for LED technology.

The team designed a way to embed strongly luminescent nanoparticles called colloidal quantum dots (the chocolate chips) into perovskite (the oatmeal cookie). Perovskites are a family of materials that can be easily manufactured from solution, and that allow electrons to move swiftly through them with minimal loss or capture by defects.

A July 15, 2015 University of Toronto news release (also on EurekAlert), which originated the news item, reveals more about the research (Note: A link has been removed),

“It’s a pretty novel idea to blend together these two optoelectronic materials, both of which are gaining a lot of traction,” says Xiwen Gong, one of the study’s lead authors and a PhD candidate working with Professor Ted Sargent. “We wanted to take advantage of the benefits of both by combining them seamlessly in a solid-state matrix.”

The result is a black crystal that relies on the perovskite matrix to ‘funnel’ electrons into the quantum dots, which are extremely efficient at converting electricity to light. Hyper-efficient LED technologies could enable applications from the visible-light LED bulbs in every home, to new displays, to gesture recognition using near-infrared wavelengths.

“When you try to jam two different crystals together, they often form separate phases without blending smoothly into each other,” says Dr. Riccardo Comin, a post-doctoral fellow in the Sargent Group. “We had to design a new strategy to convince these two components to forget about their differences and to rather intermix into forming a unique crystalline entity.”

The main challenge was making the orientation of the two crystal structures line up, called heteroexpitaxy. To achieve heteroepitaxy, Gong, Comin and their team engineered a way to connect the atomic ‘ends’ of the two crystalline structures so that they aligned smoothly, without defects forming at the seams. “We started by building a nano-scale scaffolding ‘shell’ around the quantum dots in solution, then grew the perovskite crystal around that shell so the two faces aligned,” explained coauthor Dr. Zhijun Ning, who contributed to the work while a post-doctoral fellow at UofT and is now a faculty member at ShanghaiTech.

The resulting heterogeneous material is the basis for a new family of highly energy-efficient near-infrared LEDs. Infrared LEDs can be harnessed for improved night-vision technology, to better biomedical imaging, to high-speed telecommunications.

Combining the two materials in this way also solves the problem of self-absorption, which occurs when a substance partly re-absorbs the same spectrum of energy that it emits, with a net efficiency loss. “These dots in perovskite don’t suffer reabsorption, because the emission of the dots doesn’t overlap with the absorption spectrum of the perovskite,” explains Comin.

Gong, Comin and the team deliberately designed their material to be compatible with solution-processing, so it could be readily integrated with the most inexpensive and commercially practical ways of manufacturing solar film and devices. Their next step is to build and test the hardware to capitalize on the concept they have proven with this work.

“We’re going to build the LED device and try to beat the record power efficiency reported in the literature,” says Gong.

I see that Sargent’s work is still associated with and supported by Saudi Arabia, from the news release,

This work was supported by the Ontario Research Fund Research Excellence Program, the Natural Sciences and Engineering Research Council of Canada (NSERC), and the King Abdullah University of Science & Technology (KAUST).

Here’s a link to and a citation for the paper,

Quantum-dot-in-perovskite solids by Zhijun Ning, Xiwen Gong, Riccardo Comin, Grant Walters, Fengjia Fan, Oleksandr Voznyy, Emre Yassitepe, Andrei Buin, Sjoerd Hoogland, & Edward H. Sargent. Nature 523, 324–328 (16 July 2015) doi:10.1038/nature14563 Published online 15 July 2015

This paper is behind a paywall.

Finally, the researchers have made a .gif of their hybrid crystal available.

A glowing quantum dot seamlessly integrated into a perovskite crystal matrix (Image: Ella Marushchenko). Courtesy: University of Toronto

A glowing quantum dot seamlessly integrated into a perovskite crystal matrix (Image: Ella Marushchenko). Courtesy: University of Toronto

ETA July 17, 2015:

Dexter Johnson provides some additional insight into the work in his July 16, 2015 posting on the Nanoclast blog (on the Institute for Electrical and Electronics Engineers website), Note:  Links have been removed,

Ted Sargent at the University of Toronto has built a reputation over the years as being a prominent advocate for the use of quantum dots in photovoltaics. Sargent has even penned a piece for IEEE Spectrum covering the topic, and this blog has covered his record breaking efforts at boosting the conversion efficiency of quantum dot-based photovoltaics a few times.

Earlier this year, however, Sargent started to take an interest in the hot material that has the photovoltaics community buzzing: perovskite. …

Extending catalyst life for oil and gas

A July 6, 2015 news item on Nanowerk describes the progress on determining exactly how catalysis is achieved when using zeolite (Note: A link has been removed),

Despite decades of industrial use, the exact chemical transformations occurring within zeolites, a common material used in the conversion of oil to gasoline, remain poorly understood. Now scientists have found a way to locate—with atomic precision—spots within the material where chemical reactions take place, and how these spots shut down.

Called active sites, the spots help rip apart and rearrange molecules as they pass through nanometer-sized channels, like an assembly line in a factory. A process called steaming causes these active sites to cluster, effectively shutting down the factory, the scientists reported in Nature Communications (“Determining the location and nearest neighbours of aluminium in zeolites with atom probe tomography”). This knowledge could help devise how to keep the factory running longer, so to speak, and improve catalysts that help produce fuel, biofuel and other chemicals.

A July 6, 2015 Pacific Northwest National Laboratories (PNNL) news release (also on EurekAlert), which originated the news item, describes the collaboration and the research in more detail (Note: Links have been removed),

The team included scientists from the Department of Energy’s Pacific Northwest National Laboratory, petroleum refining technology company UOP LLC and Utrecht University. To make this discovery, they reconstructed the first 3-D atomic map of an industrially relevant zeolite material to track down its key element, aluminum.

When things get steamy, structure changes

Zeolites are minerals made up of aluminum, silicon and oxygen atoms arranged in a three-dimensional crystalline structure. Though they look like white powder to the naked eye, zeolites have a sponge-like network of molecule-size pores. Aluminum atoms along these pores act like workers on an assembly line-they create active sites that give zeolites their catalytic properties.

Industry uses about a dozen synthetic zeolites as catalysts to process petroleum and chemicals. One major conversion process, called fluid catalytic cracking, depends on zeolites to produce the majority of the world’s gasoline. [emphasis mine]

To awaken active sites within zeolites, industry pretreats the material with heat and water, a process called steaming. But too much steaming somehow switches the sites off. Changing the conditions of steaming could extend the catalyst’s life, thus producing fuel more efficiently.

Scientists have long suspected that steaming causes aluminum to move around within the material, thus changing its properties. But until now aluminum has evaded detailed analysis.

Strip away the atoms

Most studies of zeolite structure rely on electron microscopy, which can’t easily distinguish aluminum from silicon because of their similar masses. Worse, the instrument’s intense electron beam tends to damage the material, changing its inherent structure before it’s seen.

Instead, the team of scientists turned to a characterization technique that had never before been successfully applied to zeolites. Called atom probe tomography, it works by zapping a sample with a pulsing laser, providing just enough energy to knock off one atom at a time. Time-of-flight mass spectrometers analyze each atom-at a rate of about 1,000 atoms per second. Unlike an electron microscope, this technique can distinguish aluminum from silicon.

Though atom probe tomography has been around for 50 years, it was originally designed to look at conductive materials, such as metals. Less conductive zeolites presented a problem.

PNNL materials scientist Danny Perea and his colleagues overcame this hurdle by adapting a Local Electrode Atom Probe at EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science User Facility accessible to scientists around the world. Most attempts to image the material ended prematurely, when electromagnetic forces within the instrument vaporized the entire sample. The key to success was to find the right conditions to prepare a sample and then to coat it with a layer of metal to help provide conductivity and strength to withstand analysis.

After hours of blasting tens-of-millions of atoms, the scientists could reconstruct an atomic map of a sample about a thousand times smaller than the width of a human hair. These maps hold clues as to why the catalyst fails.

The news release reveals what the scientists were able to see for the first time,

The images confirmed what scientists have long suspected: Steaming causes aluminum atoms to cluster. Like workers crowded around one spot on the assembly line, this clustering effectively shuts down the catalytic factory.

The scientists even pinpointed the place where aluminum likes to cluster. Zeolite crystals often grow in overlapping sub-units, forming something like a 3-D Venn diagram. Scientists call the edge between two sub-units a grain boundary, and that’s where the aluminum clustered. The scientists suspect that open space along grain boundaries attracted the aluminum.

With the guidance of these atomic maps, industry could one day modify how it steams zeolites to produce a more efficient, longer lasting catalyst. The research team will next examine other industrially important zeolites at different stages of steaming to provide a more detailed map of this transformation.

Here’s a link to and a citation for the paper,

Determining the location and nearest neighbours of aluminium in zeolites with atom probe tomography by Daniel E. Perea, Ilke Arslan, Jia Liu, Zoran Ristanović, Libor Kovarik, Bruce W. Arey, Johannes A. Lercher, Simon R. Bare, & Bert M. Weckhuysen.  Nature Communications 6, Article number: 7589 doi:10.1038/ncomms8589 Published 02 July 2015

This is an open access paper.