The Promise of Solar -Quantum Dots Improve the Performance of Cost Effective Processed Solar Cells


 
The triplet state lifetime varies with the distance and the strength of binding between the porphyrin and the surface of the quantum dot.

Nanotechnology could improve the efficiency of organic photovoltaic technology, researchers at King Abdullah University of Science and Technology (KAUST) have demonstrated1.
In general, solar cells made from organic materials offer a cheap, simple and sustainable approach to harvesting light from the sun. But there is an urgent need to improve the efficiency of these organic cells.
The performance of these devices is limited by the re-emission of light that has been absorbed, thus detracting energy that should be converted to electricity. When an organic material absorbs light, it can create an exciton — an electron paired to a positively charged equivalent called a hole. This exciton exists for a very short period before recombining radiatively or non-radiatively. So, for a useful current to be produced, the electron and hole must separate before they recombine.
Research by Omar Mohammed and his colleagues from the KAUST Solar and Photovoltaics Engineering Research Center show how the lifetime of excitons in an organic material can be extended by using quantum dots.
Quantum dots are nanometer scale particles. Their advantage in solar-cell technologies is their tunability: the optical properties, such as absorption wavelength, can be changed by varying the size of the dot. Additional molecules attached to the surface of the nanostructure can tailor the functionality of the dots even further.
Mohammed’s team investigated a family of organic compounds (commonly used in solar applications) known as porphyrins. The electron-hole pair generated in porphyrin by light absorption forms a high-energy exciton, which then relaxes to one of two different lower-energy excitons know as a singlet and a triplet.
“The photo-generated singlet excitons exhibit very short lifetimes and consequently they have short diffusion lengths, which is one of the greatest challenges for achieving high power-conversion efficiencies in solar-cell devices,” explains Mohammed. “Triplet excitons with their long lifetimes are an alternative way to overcome this problem.”

abu-dhabi-solar
The researchers showed that cadmium telluride quantum dots can improve not only the path from excited exciton to triplet exciton — so-called intersystem crossing, but also the elongation of the triplet exciton lifetime. They were able to tune the intersystem crossing and the triplet state lifetime by changing the size of the quantum dots in the solution.
“We are currently testing other absorber materials and other semiconductor quantum dots,” says Mohammed. “In addition, we are planning to fabricate solar cell devices from these nano-assemblies.”

© 2015 KAUST

Reference
Ahmed, G. H., Aly, S. M., Usman, A., Eita, M. S., Melnikov, V. A. & Mohammed, O. F. Quantum confinement-tunable intersystem crossing and the triplet state lifetime of cationic porphyrin–CdTe quantum dot nano-assemblies. Chemical Communications 51, 8010—8013 (2015). | article

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“Great Things from Small Things”

Lawrence Berkley & DOE: Surprising Discoveries about 2D Molybdenum Disulfide


Moly Berkley Jim-Schuck-MoS2_v5_2_Web-300x300Scientists with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) have used a unique nano-optical probe to study the effects of illumination on two-dimensional semiconductors at the molecular level. Working at the Molecular Foundry, a DOE Office of Science User Facility, the scientific team used the “Campanile” probe they developed to make some surprising discoveries about molybdenum disulfide, a member of a family of semiconductors, called “transition metal dichalcogenides (TMDCs), whose optoelectronic properties hold great promise for future nanoelectronic and photonic devices.

“The Campanile probe’s remarkable resolution enabled us to identify significant nanoscale optoelectronic heterogeneity in the interior regions of monolayer crystals of molybdenum disulfide, and an unexpected, approximately 300 nanometer wide, energetically disordered edge region,” says James Schuck, a staff scientist with Berkeley Lab’s Materials Sciences Division. Schuck led this study as well as the team that created the Campanile probe, which won a prestigious R&D 100 Award in 2013 for combining the advantages of scan/probe microscopy and optical spectroscopy.

“This disordered edge region, which has never been seen before, could be extremely important for any devices in which one wants to make electrical contacts,” Schuck says. “It might also prove critical to photocatalytic and nonlinear optical conversion applications.”

(From left)Jim Schuck, Wei Bao and Nicholas Borys at the Molecular Foundry where they made surprising discoveries about 2D MoS2, a promising TMDC semiconductor for future photonic and nanoelectronic devices. (Photo by Roy Kaltschmidt)

Schuck, who directs the Imaging and Manipulation of Nanostructures Facility at the Molecular Foundry, is the corresponding author of a paper describing this research in Nature Communications. The paper is titled “Visualizing nanoscale excitonic relaxation properties of disordered edges and grain boundaries in monolayer molybdenum disulfide.” The co-lead authors are Wei Bao and Nicholas Borys. (See below for a complete list of authors.)

2D-TMDCs rival graphene as potential successors to silicon for the next generation of high-speed electronics. Only a single molecule in thickness, 2D-TMDC materials boast superior energy efficiencies and a capacity to carry much higher current densities than silicon. However, since their experimental “discovery” in 2010, the performance of 2D-TMDC materials has lagged far behind theoretical expectations primarily because of a lack of understanding of 2D-TMDC properties at the nanoscale, particularly their excitonic properties. Excitons are bound pairs of excited electrons and holes that enable semiconductors to function in devices.

“The poor understanding of 2D-TMDC excitonic and other properties at the nanoscale is rooted in large part to the existing constraints on nanospectroscopic imaging,” Schuck says. “With our Campanile probe, we overcome nearly all previous limitations of near-field microscopy and are able to map critical chemical and optical properties and processes at their native length scales.”

Campanile-bellsThe Campanile probe, which draws its name from the landmark “Campanile” clock tower on the campus of the University of California at Berkeley, features a tapered, four-sided microscopic tip that is mounted on the end of an optical fiber. Two of the Campanile probe’s sides are coated with gold and the two gold layers are separated by just a few nanometers at the tip. The tapered design enables the Campanile probe to channel light of all wavelengths down into an enhanced field at the apex of the tip. The size of the gap between the gold layers determines the resolution, which can be below the diffraction optical limit.

In their new study, Schuck, Bao, Borys and their co-authors used the Campanile probe to spectroscopically map nanoscale excited-state/relaxation processes in monolayer crystals of molybdenum disulfide that were grown by chemical vapor deposition (CVD). Molybdenum disulfide is a 2D semiconductor that features high electrical conductance comparable to that of graphene, but, unlike graphene, has natural energy band-gaps, which means its conductance can be switched off.

“Our study revealed significant nanoscale optoelectronic heterogeneity and allowed us to quantify exciton-quenching phenomena at crystal grain boundaries,” Schuck said. “The discovery of the disordered edge region constitutes a paradigm shift from the idea that only a 1D metallic edge state is responsible for all the edge-related physics and photochemistry being observed in 2D-TMDCs. What’s happening at the edges of 2D-TMDC crystals is clearly more complicated than that. There’s a   mesoscopic disordered region that likely dominates most transport, nonlinear optical, and photocatalytic behavior near the edges of CVD-grown 2D-TMDCs.”

Comparison between image of MoS2 flake captured with Campanile probe and image of same flake captured with scanning confocal microscopy shows the Campanile probe’s enhanced resolution.

In this study, Schuck and his colleagues also discovered that the disordered edge region in molybdenum disulfide crystals harbors a sulfur deficiency that holds implications for future optoelectronic applications of this 2D-TMDC.

“Less sulfur means more free electrons are present in that edge region, which could lead to enhanced non-radiative recombination,” Schuck says. “Enhanced non-radiative recombination means that excitons created near a sulfur vacancy would live for a much shorter period of time.”

Schuck and his colleagues plan to next study the excitonic and electronic properties that may arise, as well as the creation of p-n junctions and quantum wells, when two disparate types of TMDCs are connected.

“We are also combining 2D-TMDC materials with so-called meta surfaces for controlling and manipulating the valley states and circular emitters that exist within these systems, as well as exploring localized quantum states that could act as near-ideal single-photon emitters and quantum-entangled Qubit states,” Schuck says.

In addition to Schuck, Bao, Borys and Weber-Bargioni, other co-authors of the Nature Communications paper are Changhyun Ko, Joonki Suh, Wen Fan, Andrew Thron, Yingjie Zhang, Alexander Buyanin, Jie Zhang, Stefano Cabrini, Paul Ashby, Alexander Weber-Bargioni, Sefaattin Tongay, Shaul Aloni, Frank Ogletree, Junqiao Wu and Miquel Salmeron.
This research was supported by the DOE Office of Science.

Additional Information

For more about the research of James Schuck and his group go here

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Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

Smart Grid and Nanotechnologies: How can Nanotechnology Reduce CO2 emissions? A Solution For Clean and Sustainable Energy


Renewable Energy Pix

Environmental sustainability remains a big trend; topics such as climate change and global warming are generating a lot of discussion. Growing world energy demand from fossil fuels plays a key role in the upward trend in CO2 emissions and is the main source of human-induced climate changes. While energy systems around the world remain at vastly different stages of development, all countries share a common problem: they are far away from achieving sustainable energy systems. As levels of CO2 and other greenhouse gases continue to rise in the atmosphere, with historical maximums reached lately, sustainability in energy generation and energy efficiency principles is becoming ever more important.

Introduction

For the first time in recorded history, more people worldwide are living in urban areas than in rural. The urbanization trend picked up pace in the 20th century and has accelerated since. Urbanization manifests itself in two ways: expansion of existing cities and creation of new ones.1 Cities are already the source of close to 80% of global CO2 (carbon-dioxide) emissions and will account for an ever-higher percentage in the coming years.

Too much CO2 in the atmosphere has been linked to climate change. If humanity continued with the same solutions that have been used to address urban development needs in the past, the resulting urban ecological footprint will not be sustainable: we would need the equivalent of two planets to maintain our lifestyles by the 2030s. The challenge is to meet the demands of urbanization in an economically viable, socially inclusive, and environmentally sustainable fashion.1,2

According to a World Energy Council study,3 global demand for primary energy is expected to increase by between 27% and 61% by 2050. Climate change is expected to lead to changes in a range of climatic variables, most notably temperature levels. Since electricity demand is closely influenced by temperature, there is likely to be an impact on power demand patterns. The magnitude of the potential impact of future climate changes on electricity demand will depend on patterns in the power use, as well as long-term socio-economic trends.

The latest assessment by Working Group I of the Intergovernmental Panel on Climate Change, released in September 2013, concluded that climate change remains one of the greatest challenges facing society. Warming of the climate system is unequivocal, human-influenced, and many unprecedented changes have been observed throughout the climate system since 1950. Limiting climate change will require substantial and sustained reductions of greenhouse gas emissions.4

Consumption patterns, together with aging and urbanization in some countries seem to have bigger implications for health and the reduction of carbon emissions than the total number of people in the world.5 As developing and newly industrialized countries improve their standards of living, their use of air conditioning and other weather-dependent consumption will likely increase their sensitivity to climate change.6 On the other hand, reducing consumption and achieving more sustainable lifestyles in rich countries will likely represent the most effective way to reduce carbon emissions.

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How can nanotechnology reduce CO2 emission?

“The Grid” and Improving Efficiencies

Nanotechnology is a platform whereby matter is manipulated at the atomic level. There are various ways that nanotechnology can be applied along the Smart Grid to help reduce CO2 emissions.

The major impact of nanotechnology on the energy sector is likely to improve the efficiency of current technologies to minimize use of fossil fuels. Any effort to reduce emissions in vehicles by reducing their weight and, in turn, decreasing fuel consumption can have an immediate and significant global impact.

It is estimated that a 10% reduction in weight of the vehicle corresponds to a 10% reduction in fuel consumption, leading to a proportionate fall in emissions. In recognition of the above, there is growing interest worldwide in exploring means of achieving weight reduction in automobiles through use of novel materials. For example, use of lighter, stronger, and stiffer nano-composite materials is considered to have the potential to significantly reduce vehicle weight.9,49

Nanotechnology is applied in aircraft coatings, which protect the materials from the special conditions of the environment where they are used (instead of the conventional bulk metals such as steel). Since the amount of CO2 emitted by an aircraft engine is directly related to the amount of fuel burned, CO2 can be reduced by making the airplane lighter.

Nanocoatings are one of the options for aerospace developers, but also for automotive, defense, marine, and plastics industries.49 Lufthansa Cargo uses the most advanced technologies and innovative processes including efficient jet engines, nanotechnology in aircraft coatings, new composites or regular jet engine cleaning – and of course monitoring overall aircraft weight. It is often a matter of only a few grams. However, given 15,000 to 16,000 flights a year and an average flight time of about 6 hours, the cumulative effect of a number of grams can quickly add up to tons. The removal of a 350 gram phone handset resulted in jet fuel savings of 3.5 tons in a year.50

Nanotechnology is already applied to improve fuel efficiency by incorporation of nanocatalysts. Enercat, a third generation nanocatalyst developed by Energenics, uses the oxygen storing cerium oxide nanoparticles to promote complete fuel combustion, which helps in reducing fuel consumption. Recently, the company has demonstrated fuel savings of 8%–10% on a mixed fleet of diesel vehicles in Italy.51

Reducing friction and improving wear resistance in engine and drive train components is of vital importance in the automotive sector. Based on the estimates made by a Swedish company Applied Nano Surfaces, reducing friction can lower the fuel consumption by about 2% and result in cutting down CO2 emissions by 500 million tons per year from trucks and other heavy vehicles in Sweden alone.9 Thanks to nanomaterials like silica, many tires will in the future be capable of attaining the best rating, the green category A. Cars equipped with category A tires consume approximately 7.5% less fuel than those with tires of the minimum standard (category G).52

Residential and commercial buildings contribute to 11% of total greenhouse gas emissions. Space heating and cooling of residential buildings account for 40% of the total residential energy use. Nanostructured materials, such as aerogels, have the potential to greatly reduce heat transfer through building elements and assist in reducing heating loads placed on air-conditioning/heating systems. Aerogel is a nanoporous super-insulating material with extremely low density; silica aerogel is the lightest solid material known with excellent thermal insulating properties, high temperature stability, very low dielectric constant and high surface area.51

Nanotechnology is positioned to create significant change across several domains, especially in energy where it may bring large and possibly sudden performance gains to renewable sources and Smart Grids. Nanotech enhancements may also increase battery power by orders of magnitude, allowing intermittent sources such as solar and wind to provide a larger share of overall electricity supply without sacrificing stability. Nanotech sensors will also enable Smart Grids and foster more flexible and decentralized electricity management.53

Nanotechnology may accelerate the technology behind renewables in various ways:

  • experts are discovering means to apply nanotechnology to photovoltaics, which would produce solar panels with double or triple the output by 2020;
  • wind turbines stand to be improved from high-performance nano-materials like graphene, a nano-engineered one-atom thick layer of mineral graphite that is 100 times stronger than steel. Nanotechnology will enable light and stiff wind blades that spin at lower wind speeds than regular blades;
  • nanotechnology could play a major role in the next generation of batteries. For example, coating the surface of an electrode with nanoparticles increases the surface area, thereby allowing more current to flow between the electrode and the chemicals inside the battery. Such techniques could increase the efficiency of electric and hybrid vehicles by significantly reducing the weight of the batteries. Moreover, superior batteries would complement renewables by storing energy economically, thus offsetting the whole issue of intermittent generation.

In a somewhat more distant future, we may see electricity systems apply nanotechnology in transmission lines. Research indicates that it is possible to develop electrical wires using carbon nanotubes that can carry higher loads and transmit without power losses even over hundreds of kilometers. The implications are significant, as it would increase the efficiency of generating power where the source is easiest to harness.53

Semiconductor devices, transistors, and sensors will benefit from nanotechnology especially in size and speed. Nanotech sensors could be used for the Smart Grid to detect issues ahead of time, ie, to measure degrading of underground cables or to bring down the price of chemical sensors already available for transformers. Nanotechnology will likely become indispensable for the Smart Grid to fully evolve in the near future.54

Energy efficiency is a way of managing and restraining the growth of energy consumption. It is one of the easiest and most cost effective ways to combat climate change, improve the competitiveness of businesses, and reduce energy costs for consumers.7

More on Using Nanotechnology to Reduce Carbon-Based Emissions

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Berkley Lab: A Better Way of Scrubbing CO2

Berkeley Lab Researchers Find Way to Improve the Cost-Effectiveness Through the Use of MOFs

A means by which the removal of carbon dioxide (CO2) from coal-fired power plants might one day be done far more efficiently and at far lower costs than today has been discovered by a team of researchers with the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab). By appending a diamine molecule to the sponge-like solid materials known as metal-organic-frameworks (MOFs), the researchers were able to more than triple the CO2-scrubbing capacity of the MOFs, while significantly reducing parasitic energy.

Read the Full Article Here: https://genesisnanotech.wordpress.com/2015/03/17/berkley-lab-a-better-way-of-scrubbing-co2/

Nanotechnology material could help reduce CO2 emissions from coal-fired power plants

1-KAUST Materials gilles-coinsliderUniversity of Adelaide researchers have  developed a new nanomaterial that could help reduce carbon dioxide emissions  from coal-fired power stations.

The new nanomaterial, described in the Journal of the  American Chemical Society (“Post-synthetic Structural Processing in a  Metal–Organic Framework Material as a Mechanism for Exceptional CO2/N2 Selectivity”), efficiently separates the  greenhouse gas carbon dioxide from nitrogen, the other significant component of  the waste gas released by coal-fired power stations. This would allow the carbon  dioxide to be separated before being stored, rather than released to the  atmosphere.
“A considerable amount of Australia‘s – and the world’s – carbon  dioxide emissions come from coal-fired power stations,” says Associate Professor  Christopher Sumby, project leader and ARC Future Fellow in the  University’s School of Chemistry and Physics.

Read the Full Article Here: https://genesisnanotech.wordpress.com/2013/07/10/nanotechnology-material-could-help-reduce-co2-emissions-from-coal-fired-power-plants/

One Nano-Crystal – Many Facets – Reducing Fuel Toxins

cubic CeO2 nanoparticlesWhen it comes to reducing the toxins released by burning gasoline, coal, or other such fuels, the catalyst needs to be reliable. Yet, a promising catalyst, cerium dioxide (CeO2), seemed erratic. The catalyst’s three different surfaces behaved differently. For the first time, researchers got an atomically resolved view of the three structures, including the placement of previously difficult-to-visualize oxygen atoms. This information may provide insights into why the surfaces have distinct catalytic properties (“Probing the Surface Sites of CeO2 Nanocrystals with Well-Defined Surface Planes via Methanol Adsorption and Desorption”).

Read the Full Article Here: https://genesisnanotech.wordpress.com/2015/06/12/one-nano-crystal-many-facets-reducing-fuel-toxins/

Conclusion

This review demonstrates the potential for reduction of CO2 emissions that Smart Grids can potentially achieve. Power grid modernization is an evolution that will continue for years or decades, and providing a robust foundation for new applications and technologies is imperative.

The electric power industry is facing tremendous opportunities and becoming increasingly important in the emerging low-carbon economy. Governments are still dominant players in high-cost smart-grid investments. This suggests the need for a policy framework that attracts private capital investment, especially from renewable project developers, and communication and ICT companies.

The challenge we face is neither a technical nor policy one – it is political: the current pace of action is simply insufficient. The technologies to reduce emission levels to a level consistent with the 2°C target are available and we know which policies we can use to deploy them. However, the political will to do so remains weak. This lack of political will comes with a price: we will have to undertake steeper and more costly actions to potentially bridge the emissions gap by 2020.4 However, technical possibilities aside, the key to reducing emission levels will be the tough but unavoidable decision that reducing carbon pollution must be of the highest priority.

To Read the Full Article Go Here: http://www.dovepress.com/smart-grid-and-nanotechnologies-a-solution-for-clean-and-sustainable-e-peer-reviewed-fulltext-article-EECT

Nanotechnology Enabled Water Treatment or NEWT: Transforming the Economics of Water Treatment


0629_NEWT-log-lg-310x310NEWT Center will use nanotechnology to transform economics of water treatment A Rice University-led consortium of industry, university and government partners has been chosen to establish one of the National Science Foundation’s (NSF) prestigious Engineering Research Centers in Houston to develop compact, mobile, off-grid water-treatment systems that can provide clean water to millions of people who lack it and make U.S. energy production more sustainable and cost-effective.

Nanotechnology Enabled Water Treatment Systems, or NEWT, is Houston’s first NSF Engineering Research Center (ERC) and only the third in Texas in nearly 30 years. It is funded by a five-year, $18.5 million NSF grant that can be renewed for a potential term of 10 years. NEWT brings together experts from Rice, Arizona State University, Yale University and the University of Texas at El Paso (UTEP) to work with more than 30 partners: including Shell, Baker Hughes, UNESCO, U.S. Army Corps of Engineers and NASA.

ERCs are interdisciplinary, multi-institutional centers that join academia, industry and government in partnership to produce both transformational technology and innovative-minded engineering graduates who are primed to lead the global economy. ERCs often become self-sustaining and typically leverage more than $40 million in federal and industry research funding during their first decade.

“The importance of clean water to global health and economic development simply cannot be overstated,” said NEWT Director Pedro Alvarez, the grant’s principal investigator. “We envision using technology and advanced materials to provide clean water to millions of people who lack it and to enable energy production in the United States to be more cost-effective and more sustainable in regard to its water footprint.”

NEWT Center will use nanotechnology to transform water treatment: Video

Houston-area Congressman John Culberson, R-Texas, chair of the House Subcommittee on Commerce, Justice and Science, said, “Technology is a key enabler for the energy industry, and NEWT is ideally located at Rice, in the heart of the world’s energy capital, where it can partner with industry to ensure that the United States remains a leading energy producer.”

Alvarez, Rice’s George R. Brown Professor of Civil and Environmental Engineering and professor of chemistry, materials science and nanoengineering, said treated water is often unavailable in rural areas and low-resource communities that cannot afford large treatment plants or the miles of underground pipes to deliver water. Moreover, large-scale treatment and distribution uses a great deal of energy. “About 25 percent of the energy bill for a typical city is associated with the cost of moving water,” he said.

NEWT Deputy Director Paul Westerhoff said the new modular water-treatment systems, which will be small enough to fit in the back of a tractor-trailer, will use nanoengineered catalysts, membranes and light-activated materials to change the economics of water treatment.0629_NEWT-truck-lg-310x239

“NEWT’s vision goes well beyond today’s technology,” said Westerhoff, vice provost of academic research at ASU and co-principal investigator on the NSF grant. “We’ve set a path for transformative new technology that will move water treatment from a predominantly chemical treatment process to more efficient catalytic and physical processes that exploit solar energy and generate less waste.”

Co-principal investigator and NEWT Associate Director for Research Qilin Li, the leader of NEWT’s advanced treatment test beds at Rice, said the system’s technology will be useful in places where water and power infrastructure does not exist.

“The NEWT drinking water system will be able to produce drinking water from any source, including pond water, seawater and floodwater, using solar energy and even under cloudy conditions,” said Li, associate professor of civil and environmental engineering, chemical and biomolecular engineering, and of materials science and nanoengineering at Rice. “The modular treatment units will be easy to configure and reconfigure to meet desired water-quality levels. The system will include components that target suspended solids, microbes, dissolved contaminants and salts, and it will have the ability to treat a variety of industrial wastewater according to the industry’s need for discharge or reuse.”0629_NEWT-mod-lg-310x239

NEWT will focus on applications for humanitarian emergency response, rural water systems and wastewater treatment and reuse at remote sites, including both onshore and offshore drilling platforms for oil and gas exploration.

0629_NEWT-log-lg-310x310Yale’s Menachem “Meny” Elimelech, co-principal investigator and lead researcher for membrane processes, said NEWT’s innovative enabling technologies are founded on rigorous basic research into nanomaterials, membrane dynamics, photonics, scaling, paramagnetism and more.

“Our modular water-treatment systems will use a combination of component technologies,” said Elimelech, Yale’s Roberto C. Goizueta Professor of Environmental and Chemical Engineering. “For example, we expect to use high-permeability membranes that resist fouling; engineered nanomaterials that can be used for membrane surface self-cleaning and biofilm control; capacitive deionization to eliminate scaly mineral deposits; and reusable magnetic nanoparticles that can soak up pollutants like a sponge.”

UTEP’s Jorge Gardea-Torresdey, co-principal investigator and co-leader of NEWT’s safety and sustainability effort, said the rapid development of engineered nanomaterials has brought NEWT’s transformative vision within reach.

“Treating water using fewer chemicals and less energy is crucial in this day and age,” said Gardea-Torresdey, UTEP’s Dudley Professor of Chemistry and Environmental Science and Engineering. “The exceptional properties of engineered nanomaterials will enable us to do this safely and effectively.”

Alvarez said another significant research thrust in nanophotonics will be headed by Rice co-principal investigator Naomi Halas, the inventor of “solar steam” technology, and co-led by ASU’s Mary Laura Lind.

“More than half of the cost associated with desalination of water comes from energy,” said Halas, Rice’s Stanley C. Moore Professor of Electrical and Computer Engineering and professor of chemistry, bioengineering, physics and astronomy, and materials science and nanoengineering. “We are working to develop several supporting technologies for NEWT, including nanophotonics-enabled direct solar membrane distillation for low-energy desalination.”

Mike Wong Lake%20ZurichRice’s Michael Wong, Yale’s Jaehong Kim and UTEP’s Dino Villagran will collaborate in efforts to develop novel multifunctional materials such as superior sorbents and catalysts, and Yale’s Julie Zimmerman will co-lead cross-cutting efforts in safety and sustainability. Rice’s Roland Smith will lead a comprehensive diversity program that aims to attract more women and underrepresented minority students and faculty, and Rice’s Brad Burke will head up innovation and commercialization efforts with private partners. Rice’s Rebecca Richards-Kortum will lead an innovative educational program that incorporates some of the “experiential learning” techniques she developed for the award-winning undergraduate research programs at Rice 360º: Institute for Global Health Technologies, and Rice’s Carolyn Nichol will lead the K-12 education efforts.

Alvarez said NEWT’s goal is to attract industry funding and become self-sufficient within 10 years. Toward that end, he said NEWT was careful to select industrial partners from every part of the water market, including equipment makers and vendors, system operators, industrial service firms and others.

NEWT is one of three new ERCs announced by the NSF today in Washington. They join 16 existing centers that are still receiving federal support, including Texas’ only other active ERC, the University of Texas at Austin’s NASCENT, as well as the other active center in which Rice is a partner, Princeton University’s MIRTHE.

0629_NEWT-Alvarez29-lg-310x465Alvarez credited Culberson and the Texas Railroad Commission for helping facilitate partnerships that were crucial for NEWT. He said the consortium’s bid to land the NSF grant was also made possible by seed funding from Rice’s Energy and Environment Initiative, a sweeping institutional initiative to engage Rice faculty from all disciplines in creating sustainable, transformative energy technologies.

“Rice’s Energy and Environment Initiative was instrumental in developing a competitive proposal, in facilitating a team-building effort and in facilitating contacts with industry to get the necessary buy-in for our vision,” Alvarez said.

Nanotechnology Enabled Water Treatment Program

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NIST Method for Spotting Quantum Dots Could Help Make High-Performance Nanophotonic Devices


NIST 081115 15CNST009_quantum_dot_finder_LRLife may be as unpredictable as a box of chocolates, but ideally, you always know what you’re going to get from a quantum dot. A quantum dot should produce one, and only one, photon—the smallest constituent of light—each time it is energized. This characteristic makes it attractive for use in various quantum technologies such as secure communications. Oftentimes, however, the trick is in finding the dots.

NIST 081115 15CNST009_quantum_dot_finder_LR[Clockwise from top left] Circular grating for extracting single photons from a quantum dot. For optimal performance, the quantum dot must be located at the center of the grating. Image taken with the camera-based optical location technique. A single quantum dot appears as a bright spot within an area defined by four alignment marks. Electron-beam lithography is used to define a circular grating at the quantum dot’s location. Image of the emission of the quantum dot within the grating. The bright spot appears in the center of the device, as desired.

Credit: NIST
View hi-resolution image

“Self-assembled, epitaxially grown” quantum dots have the highest optical quality. They randomly emerge (self-assemble) at the interface between two layers of a semiconductor crystal as it is built up layer-by-layer (epitaxially grown).

They grow randomly, but in order for the dots to be useful, they need to be located in a precise relation to some other photonic structure, be it a grating, resonator or waveguide, that can control the photons that the quantum dot generates. However, finding the dots—they’re just about 10 nanometers across—is no small feat.

Always up for a challenge, researchers working at the National Institute of Standards and Technology (NIST) have developed a simple new technique for locating them, and used it to create high-performance single photon sources.

This new development, which appeared in Nature Communications,* may make the manufacture of high-performance photonic devices using quantum dots much more efficient. Such devices are usually made in regular arrays using standard nanofabrication techniques for the control structures. However because of the random distribution of the dots, only a small percentage of them will line up correctly with the control structures. This process produces very few working devices.

“This is a first step towards providing accurate location information for the manufacture of high performance quantum dot devices,” says NIST physicist Kartik Srinivasan. “So far, the general approach has been statistical—make a lot of devices and end up with a small fraction that work. Our camera-based imaging technique maps the location of the quantum dots first, and then uses that knowledge to build optimized light-control devices in the right place.”

According to co-lead researcher Luca Sapienza of the University of Southampton in the United Kingdom, the new technique is sort of a twist on a red-eye reducing camera flash, where the first flash causes the subject’s pupils to close and the second illuminates the scene. Instead of a xenon-powered flash, the NIST team uses two LEDs.

In their setup, one LED activates the quantum dots when it flashes (so the LED gives the quantum dots red-eye). At the same time, a second, different color LED flash illuminates metallic orientation marks placed on the surface of the semiconductor wafer the dots are embedded in. Then a sensitive camera snaps a 100-micrometer by 100-micrometer picture.

By cross-referencing the glowing dots with the orientation marks, the researchers can determine the dots’ locations with an uncertainty of less than 30 nanometers. The coordinates in hand, scientists can then tell the computer-controlled electron beam lithography tool to place the control structures in the correct places, with the result being many more usable devices.

Using this technique, the researchers demonstrated grating-based single photon sources in which they were able to collect 50 percent of the quantum dot’s emitted photons, the theoretical limit for this type of structure.

They also demonstrated that more than 99 percent of the light produced from their source came out as single photons. Such high purity is partly due to the fact that the location technique helps the researchers to quickly survey the wafer (10,000 square micrometers at a time) to find regions where the quantum dot density is especially low, only about one per 1,000 square micrometers. This makes it far more likely that each grating device contains one—and only one—quantum dot.

This work was performed in part at NIST’s Center for Nanoscale Science and Technology (CNST), a national user facility available to researchers from industry, academia and government. In addition to NIST and the University of Southampton, researchers from the University of Rochester contributed to this work.

* L. Sapienza, M. Davanço, A. Badolato and K. Srinivasan. Nanoscale optical positioning of single quantum dots for bright and pure
single-photon emission.
Nature Communications, 6, 7833 doi:10.1038/ncomms8833. Published 27 July 2015.

DOW Chemical CO. – New Research may Enhance Display and LED Lighting Technology: More Efficient – Lower Cost Quantum Dots


U of Illinois QD 150807131233_1_540x360Large-area integration of quantum dots, photonic crystals produce brighter and more efficient light.

Recently, quantum dots (QDs)–nano-sized semiconductor particles that produce bright, sharp, color light–have moved from the research lab into commercial products like high-end TVs, e-readers, laptops, and even some LED lighting. However, QDs are expensive to make so there’s a push to improve their performance and efficiency, while lowering their fabrication costs.

Researchers from the University of Illinois at Urbana-Champaign have produced some promising results toward that goal, developing a new method to extract more efficient and polarized light from quantum dots (QDs) over a large-scale area. Their method, which combines QD and photonic crystal technology, could lead to brighter and more efficient mobile phone, tablet, and computer displays, as well as enhanced LED lighting.

With funding from the Dow Chemical Company, the research team, led by Electrical & Computer Engineering (ECE) Professor Brian Cunningham, Chemistry Professor Ralph Nuzzo, and Mechanical Science & Engineering Professor Andrew Alleyne, embedded QDs in novel polymer materials that retain strong quantum efficiency. They then used electrohydrodynamic jet (e-jet) printing technology to precisely print the QD-embedded polymers onto photonic crystal structures. This precision eliminates wasted QDs, which are expensive to make.

These photonic crystals limit the direction that the QD-generated light is emitted, meaning they produce polarized light, which is more intense than normal QD light output.

According to Gloria See, an ECE graduate student and lead author of the research reported in Applied Physics Letters, their replica molded photonic crystals could someday lead to brighter, less expensive, and more efficient displays. “Since screens consume large amounts of energy in devices like laptops, phones, and tablets, our approach could have a huge impact on energy consumption and battery life,” she noted.

“If you start with polarized light, then you double your optical efficiency,” See explained. “If you put the photonic-crystal-enhanced quantum dot into a device like a phone or computer, then the battery will last much longer because the display would only draw half as much power as conventional displays.”

To demonstrate the technology, See fabricated a novel 1mm device (aka Robot Man) made of yellow photonic-crystal-enhanced QDs. The device is made of thousands of quantum dots, each measuring about six nanometers.

“We made a tiny device, but the process can easily be scaled up to large flexible plastic sheets,” See said. “We make one expensive ‘master’ molding template that must be designed very precisely, but we can use the template to produce thousands of replicas very quickly and cheaply.”


Story Source:

The above post is reprinted from materials provided by University of Illinois College of Engineering. The original item was written by Laura Schmitt. Note: Materials may be edited for content and length.


Journal Reference:

  1. Gloria G. See, Lu Xu, Erick Sutanto, Andrew G. Alleyne, Ralph G. Nuzzo, Brian T. Cunningham. Polarized quantum dot emission in electrohydrodynamic jet printed photonic crystals. Applied Physics Letters, 2015; 107 (5): 051101 DOI: 10.1063/1.4927648

DARPA: New Nano-Material Could Change How We Work and Play


newmaterialworkplayx250Serendipity has as much a place in sci­ence as in love.

That’s what North­eastern Univ. physi­cists Swastik Kar and Srinivas Sridhar found during their four-year project to modify graphene, a stronger-than-steel infin­i­tes­i­mally thin lat­tice of tightly packed carbon atoms. Pri­marily funded by the Army Research Lab­o­ra­tory and Defense Advanced Research Projects Agency, or DARPA, the researchers were charged with imbuing the decade-old mate­rial with thermal sen­si­tivity for use in infrared imaging devices such as night-vision gog­gles for the military.

What they unearthed, pub­lished in Science Advances, was so much more: an entirely new mate­rial spun out of boron, nitrogen, carbon and oxygen that shows evi­dence of mag­netic, optical and elec­trical properties, as well as DARPA’s sought-after thermal ones. Its poten­tial appli­ca­tions run the gamut: from 20-megapixel arrays for cell­phone cam­eras to photo detec­tors to atom­i­cally thin tran­sis­tors that when mul­ti­plied by the bil­lions could fuel computers.

“We had to start from scratch and build every­thing,” says Kar, an assis­tant pro­fessor of physics in the Col­lege of Sci­ence. “We were on a journey, cre­ating a new path, a new direc­tion of research.”

newmaterialworkplayx250

An artistic ren¬dering of novel mag¬netism in 2D-BNCO sheets, the new mate¬rial Swastik Kar and Srinivas Sridhar cre¬ated. Image: Northeastern Univ.

The pair was familiar with “alloys,” con­trolled com­bi­na­tions of ele­ments that resulted in mate­rials with prop­er­ties that sur­passed graphene’s—for example, the addi­tion of boron and nitrogen to graphene’s carbon to con­note the con­duc­tivity nec­es­sary to pro­duce an elec­trical insu­lator. But no one had ever thought of choosing oxygen to add to the mix.

What led the North­eastern researchers to do so?

“Well, we didn’t choose oxygen,” says Kar, smiling broadly. “Oxygen chose us.”

Oxygen, of course, is every­where. Indeed, Kar and Sridhar spent a lot of time trying to get rid of the oxygen seeping into their brew, wor­ried that it would con­t­a­m­i­nate the “pure” mate­rial they were seeking to develop.

“That’s where the Aha! moment hap­pened for us,” says Kar. “We real­ized we could not ignore the role that oxygen plays in the way these ele­ments mix together.”

“So instead of trying to remove oxygen, we thought: Let’s con­trol its intro­duc­tion,” adds Sridhar, the Arts and Sci­ences Dis­tin­guished Pro­fessor of Physics and director of Northeastern’s Elec­tronic Mate­rials Research Institute.

Oxygen, it turned out, was behaving in the reac­tion chamber in a way the sci­en­tists had never antic­i­pated: It was deter­mining how the other elements—the boron, carbon and nitrogen—combined in a solid, crystal form, while also inserting itself into the lat­tice. The trace amounts of oxygen were, metaphor­i­cally, “etching away” some of the patches of carbon, explains Kar, making room for the boron and nitrogen to fill the gaps.

“It was as if the oxygen was con­trol­ling the geo­metric struc­ture,” says Sridhar.

They named the new mate­rial, sen­sibly, 2D-BNCO, rep­re­senting the four ele­ments in the mix and the two-dimensionality of the super-thin light­weight mate­rial, and set about char­ac­ter­izing and man­u­fac­turing it, to ensure it was both repro­ducible and scal­able. That meant inves­ti­gating the myriad per­mu­ta­tions of the four ingre­di­ents, holding three con­stant while varying the mea­sure­ment of the remaining one, and vice versa, mul­tiple times over.

After each trial, they ana­lyzed the struc­ture and the func­tional prop­er­ties of the product—elec­trical, optical—using elec­tron micro­scopes and spec­tro­scopic tools, and col­lab­o­rated with com­pu­ta­tional physi­cists, who cre­ated models of the struc­tures to see if the con­fig­u­ra­tions would be fea­sible in the real world.

Next they will examine the new material’s mechan­ical prop­er­ties and begin to exper­i­men­tally val­i­date the mag­netic ones con­ferred, sur­pris­ingly, by the inter­min­gling of these four non­mag­netic ele­ments. “You begin to see very quickly how com­pli­cated that process is,” says Kar.

Helping with that com­plexity were col­lab­o­ra­tors from around the globe. In addi­tion to North­eastern asso­ciate research sci­en­tists, post­doc­toral fel­lows, and grad­uate stu­dents, con­trib­u­tors included researchers in gov­ern­ment, industry, and acad­emia from the U.S., Mexico and India.

“There is still a long way to go but there are clear indi­ca­tions that we can tune the elec­trical prop­er­ties of these mate­rials,” says Sridhar. “And if we find the right com­bi­na­tion, we will very likely get to that point where we reach the thermal sen­si­tivity that DARPA was ini­tially looking for as well as many as-yet unfore­seen applications.”

Source: Northeastern Univ.

Will the Next Generation of Fuel Efficient Cars be ‘Driven’ by Graphene Technologies?


Harvesting heat produced by a car’s engine which would otherwise be wasted and using it to recharge the car’s batteries or powering the air-conditioning system could be a significant feature in the next generation of hybrid cars.
Prof Ian Kinloch, Professor of Materials Science
Prof Ian Kinloch, Professor of Materials Science
The average car currently loses around 70% of energy generated through fuel consumption to heat. Utilising that lost energy requires a thermoelectric material which can generate an electrical current from the application of heat.

Thermoelectric materials convert heat to electricity or vice-versa, such as with refrigerators. The challenge with these devices is to use a material that is a good conductor of electricity but also dissipates heat well.

Currently, materials which exhibit these properties are often toxic and operate at very high temperatures – higher than that produced by car engines. By adding graphene, a new generation of composite materials could reduce carbon emissions globally from car use.

Scientists from The University of Manchester working with European Thermodynamics Ltd have increased the potential for low cost thermoelectric materials to be used more widely in the automotive industry.
The team, led by Prof Ian Kinloch, Prof Robert Freer and Yue Lin, added a small amount of graphene to strontium titanium oxide.
The resulting composite was able to convert heat which would otherwise be lost as waste into an electric current over a broad temperature range, going down to room temperature.
Prof Freer said: “Current oxide thermoelectric materials are limited by their operating temperatures which can be around 700 degrees Celsius. This has been a problem which has hampered efforts to improve efficiency by utilising heat energy waste for some time.
“Our findings show that by introducing a small amount of graphene to the base material can reduce the thermal operating window to room temperature which offers a huge range of potential for applications.
“The new material will convert 3-5% of the heat into electricity. That is not much but, given that the average vehicle loses roughly 70% of the energy supplied to it by its fuel to waste heat and friction, recovering even a small percentage of this with thermoelectric technology would be worthwhile.”
The findings were published in the journal ACS Applied Materials and Interfaces (“hermoelectric power generation from lanthanum strontium titanium oxide at room temperature through the addition of graphene”). Graphene’s range of superlative properties and small size causes the transfer of heat through the material to slow leading to the desired lower operating temperatures.
Improving fuel efficiency, whilst retaining performance, has long been a driving force for car manufacturers. Graphene could also aid fuel economy and safety when used as a composite material in the chassis or bodywork to reduce weight compared to traditional materials used.
Source: University of Manchester

NIST: Reducing the High Costs of Hydrogen (Fuel) Pipelines


NIST 580303_10152072709285365_1905986131_nThe National Institute of Standards and Technology (NIST) has put firm numbers on the high costs of installing pipelines to transport hydrogen fuel–and also found a way to reduce those costs.

Samples of pipeline steel instrumented for fatigue testing in a pressurized hydrogen chamber (the vertical tube). NIST researchers used data from such tests to develop a model for hydrogen effects on pipeline lifetime, to support a federal effort to reduce overall costs of hydrogen fuel. (Image: NIST)
Pipelines to carry hydrogen cost more than other gas pipelines because of the measures required to combat the damage hydrogen does to steel’s mechanical properties over time. NIST researchers calculated that hydrogen-specific steel pipelines can cost as much as 68 percent more than natural gas pipelines, depending on pipe diameter and operating pressure.* By contrast, a widely used cost model** suggests a cost penalty of only about 10 percent.>Samples of pipeline steel instrumented for fatigue testingBut the good news, according to the new NIST study, is that hydrogen transport costs could be reduced for most pipeline sizes and pressures by modifying industry codes*** to allow the use of a higher-strength grade of steel alloy without requiring thicker pipe walls. The stronger steel is more expensive, but dropping the requirement for thicker walls would reduce materials use and related welding and labor costs, resulting in a net cost reduction. The code modifications, which NIST has proposed to the American Society of Mechanical Engineers (ASME), would not lower pipeline performance or safety, the NIST authors say.”The cost savings comes from using less–because of thinner walls–of the more expensive material,” says NIST materials scientist James Fekete, a co-author of the study. “The current code does not allow you to reduce thickness when using higher-strength material, so costs would increase. With the proposed code, in most cases, you can get a net savings with a thinner pipe wall, because the net reduction in material exceeds the higher cost per unit weight.”

The NIST study is part of a federal effort to reduce the overall costs of hydrogen fuel, which is renewable, nontoxic and produces no harmful emissions. Much of the cost is for distribution, which likely would be most economical by pipeline. The U.S. contains more than 300,000 miles of pipelines for natural gas but very little customized for hydrogen. Existing codes for hydrogen pipelines are based on decades-old data. NIST researchers are studying hydrogen’s effects on steel to find ways to reduce pipeline costs without compromising safety or performance.

As an example, the new code would allow a 24-inch pipe made of high-strength X70 steel to be manufactured with a thickness of 0.375 inches for transporting hydrogen gas at 1500 pounds per square inch (psi). (In line with industry practice, ASME pipeline standards are expressed in customary units.) According to the new NIST study, this would reduce costs by 31 percent compared to the baseline X52 steel with a thickness of 0.562 inches, as required by the current code. In addition, thanks to its higher strength, X70 would make it possible to safely transport hydrogen through bigger pipelines at higher pressure (36-inch diameter pipe to transport hydrogen at 1500 psi) than is allowed with X52, enabling transport and storage of greater fuel volumes. This diameter-pressure combination is not possible under the current code.

The proposed code modifications were developed through research into the fatigue properties of high-strength steel at NIST’s Hydrogen Pipeline Material Testing Facility. In actual use, pipelines are subjected to cycles of pressurization at stresses far below the failure point, but high enough to result in fatigue damage. Unfortunately, it is difficult and expensive to determine steel fatigue properties in pressurized hydrogen. As a result, industry has historically used tension testing data as the basis for pipeline design, and higher-strength steels lose ductility in such tests in pressurized hydrogen. But this type of testing, which involves steadily increasing stress to the failure point, does not predict fatigue performance in hydrogen pipeline materials, Fekete says.
NIST research has shown that under realistic conditions, steel alloys with higher strengths (such as X70) do not have higher fatigue crack growth rates than lower grades (X52). The data have been used to develop a model**** for hydrogen effects on pipeline steel fatigue crack growth, which can predict pipeline lifetime based on operating conditions.
Notes
* J.W. Sowards, J.R. Fekete and R.L. Amaro. Economic impact of applying high strength steels in hydrogen gas pipelines. International Journal of Hydrogen Energy. 2015. In press, corrected proof available online. DOI:10.1016/j.ijhydene.2015.06.090
** DOE H2A Delivery Analysis. U.S. Department of Energy. Available online at http://www.hydrogen.energy.gov/h2a_delivery.html.
*** ASME B31.12 Hydrogen Piping and Pipeline Code (ASME B31.12). Industry groups such as ASME commonly rely on NIST data in developing codes.
**** R.L. Amaro, N. Rustagi, K.O. Findley, E.S. Drexler and A.J. Slifka. Modeling the fatigue crack growth of X100 pipeline steel in gaseous hydrogen. Int. J. Fatigue, 59 (2014). pp 262-271.
Source: NIST

Graphene-perovskite hybrids make new super-detectors: Turning Light into Energy


Graphene Perovskite 081115 324x182EPFL scientists have created the first perovskite nanowire-graphene hybrid phototransistors. Even at room temperature, the devices are highly sensitive to light, making them outstanding photodetectors.

The lead-containing perovskite materials can turn light into electricity with high efficiency, which is why they have revolutionized solar cell technologies. On the other hand, graphene is known for its super-strength as well as its excellent electrical conductivity. Combining the two materials, EPFL scientists have created the first ever class of hybrid transistors that turn light into electricity with high sensitivity and at room temperature. The work is published in Small.

The lab of László Forró at EPFL, where the chemical activity is led by Endre Horváth, used its expertise in microengineering to create nanowires of the perovskite methylammonium lead iodide. This highly non-trivial route for the synthesis of nanowires was developed by him in 2014 and called slip-coating method. The advantage of nanowires is their consistency, while their manufacturing can be controlled to modify their architecture and explore different designs.

Making a device by depositing the perovskite nanowires onto graphene has increased the efficiency in converting light to electrical current at room temperature. “Such a device shows almost 750,000 times higher photoresponse compared to detectors made only with perovskite nanowires,” added Massimo Spina who fabricated the miniature photodetectors. Because of this exceptionally high sensitivity, the graphene/perovskite nanowire hybrid device is considered to be a superb candidate for even a single-photon detection.

This work was founded by the Swiss National Science Foundation. The hybrid devices were fabricated in part at EPFL’s Center for Micro/Nanotechnology.

Reference