Nanosys CEO Jason Hartlove: Quantum Dot Forum 2015 in San Francisco, CA: Video

Published on Mar 30, 2015

Bringing better pixels to UHD with Quantum Dots
The next wave of market push for TVs is Ultra-High Definition. The increase in resolution from HD to 4K is perhaps the most well known benefit of UHD but there is much more to this new broadcast specification. High dynamic range (HDR) and wide color gamut bring more perceptible benefits to users in terms of an improved viewing experience than improved resolution alone. The ultra-high color gamut standard Rec. 2020 was originally defined for laser-based projectors where the color primaries are on the color locus of the CIE diagram. Because of the deeply saturated color coordinates, Rec. 2020 is beyond the capabilities of OLEDs. Is the Rec. 2020 color standard reachable for consumer displays or is it only for high-end laser-based projection systems? This presentation explores the capability of using quantum dots in LCDs to reach the ultra-high color gamut of Rec. 2020.

For more information on Nanosys, visit: http://www.nanosysinc.com
For more information on the Quantum Dot Forum visit: http://www.quantumdotsforum.com

SEC: Startups Can Now Raise $50 Million in ‘Mini IPO’

March 25, 2015

The SEC on Wednesday approved game-changing final rules in the implementation of Title IV of the JOBS Act, known as “Regulation A+,” which will allow small businesses and startups to raise up to $50 million from “the crowd.”

As I reported more than a year ago, this little-known provision of the JOBS Act will allow a startup company or emerging business to hold a “mini IPO” from the general public, not just accredited investors, and should be a complete game-changer for the way businesses are funded.

When Congress passed the JOBS Act in April 2012, Regulation A+ was an attempt to fix Regulation A, a rarely-used provision of federal law that allowed companies to raise up to $5 million in a public offering. Regulation A was a bust because it required the company to register its offering in each state where it was to be sold. The cost of complying with each state’s “Blue Sky Law” was exorbitant, compared to more commonly used laws such as Regulation D that allowed a company to raise the same amount of money, or more, without having to pay for expensive state-by-state compliance.

Under the SEC’s new rules for Regulation A+, the amount that could be raised increases to $50 million and the need for state compliance has been eliminated. More importantly, Regulation A+ allows those funds to be raised from the general public, not just accredited investors like with Regulation D offerings.

The question that had everyone in the crowdfunding world holding their collective breath was simple: Would the SEC keep their proposed rules intact when its leadership voted, or would they succumb to the pressure of state securities regulators who were adamantly opposed to lessening of restrictions for their own selfish financial reasons? The answer is that the SEC stuck by their guns and allowed companies to raise Regulation A+ without having to go to each state and spend a fortune registering their offerings.

Related: People Invest in People — an Overlooked Aspect of Private Investing

Another important issue the SEC decided involved who can invest in these offerings. The JOBS Act limited Regulation A+ offerings to “qualified investors” which led some to argue that only “accredited investors” would be allowed to invest. Accredited investors are those individuals who earn more than $200,000 per year or have a net worth of greater than $1,000,000. However, the SEC broadly defined the term “qualified investors” under Regulation A+ to allow anyone to invest, albeit with some limitations as to the amount.

For those worried about protecting investors from fraud, Regulation A+ only allows investors to invest 10 percent of the greater of their annual income or net worth in these securities. The SEC has also implemented other strong investor protections such as “bad actor” background checks on the companies offering the securities, and disclosure of the company’s financial information as part of the offering.

The Regulation A+ rules can be read in full here. There are hundreds of pages, so get ready for a long read or a fast way to bore yourself to sleep. Having read the entire thing, I can tell you with confidence as a crowdfunding attorney that Regulation A+ has a chance to dramatically change the way small and emerging businesses raise capital in America.

The rules released by the SEC today now have to be published in the Federal Register before they become law, which takes about 60 days. As soon as that happens, entrepreneurs will have the ability to raise millions of dollars from “the crowd” in a simplified and comparatively affordable offering using Regulation A+.

Related: Real-Estate Crowdfunding Set to Top $2.5 Billion This Year

Kendall Almerico

Contributor

Crowdfunding Attorney and JOBS Act Expert

Report: Global Market for Nanotechnology Products Expected to Reach About $64.2 Billion by 2019

The global market for nanotechnology products was valued at $22.9 billion in 2013 and increased to about $26 billion in 2014. This market is expected to reach about $64.2 billion by 2019, a compound annual growth rate (CAGR) of 19.8% from 2014 to 2019.

This report provides:

• An in-depth analysis of the global market for nanotechnology.
• Analyses of global market trends, with data from 2013, estimates for 2014, and projections of CAGRs through 2019.
• Identification of the segments of the nanotechnology market with the greatest commercial potential in the near to mid-term (2014-2019).
• Information most useful and especially intended for entrepreneurs, investors, venture capitalists, nanotechnology marketing executives, and other readers with a need to know where the nanotechnology market is headed in the next five years.
• Comprehensive company profiles of key players in the market.

SCOPE OF REPORT

The global market for nanotechnology applications will be addressed. Nanotechnology applications are defined comprehensively as the creation and use of materials, devices and systems through the manipulation of matter at scales of less than 100 nanometers. The study covers nanomaterials (nanoparticles, nanotubes, nanostructured materials and nanocomposites), nanotools (nanolithography tools and scanning probe microscopes) and nanodevices (nanosensors and nanoelectronics).

A pragmatic decision was made to exclude certain types of materials and devices from the report that technically fit the definition of nanotechnology. These exceptions include carbon black nanoparticles used to reinforce tires and other rubber products; photographic silver and dye nanoparticles; and activated carbon used for water filtration. These materials were excluded because they have been used for decades, long before the concept of nanotechnology was born, and their huge volumes (especially carbon black and activated carbon) would tend to swamp the newer nanomaterials in the analysis.

In the case of pharmaceutical applications, this report measures the value of the particles that the particle manufacturer receives. Research dollars invested into designing better particles, or better delivery approaches, are not included. The value created through clinical trial success and eventual Food and Drug Administration (FDA) approval and entrance as a prescription drug are not included.

Nanoscale semiconductors are also excluded from the study, although the tools used to create them are included. Unlike carbon black and activated carbon, nanoscale semiconductors are a relatively new development. However, they have been analyzed comprehensively elsewhere and, like carbon black and activated carbon, would tend to overwhelm other nanotechnologies by their sheer volume in the out-years toward 2019.

The study format includes the following major elements:

• Executive summary
• Definitions
• Milestones in the development of nanotechnology
• Current and potential nanotechnology applications
• Applications and end users with the greatest commercial potential through 2019
• Global nanotechnology market trends, 2013 through 2019
• Factors that will influence the long-term development of nanotechnology
• Market shares and industry structure

Download the full report: https://www.reportbuyer.com/product/96617/

Wrapping carbon nanotubes in polymers enhances their performance

Scientists first reported carbon nanotubes in the early 1990s. Since then, these tiny cylinders have been part of the quest to reduce the size of technological devices and their components. Carbon nanotubes (CNTs) have very desirable properties. They are 100 times stronger than steel and one-sixth its weight. They have several times the electrical and thermal conductivity of copper. And they have almost none of the environmental or physical degradation issues common to most metals, such as thermal contraction and expansion or erosion.

CNTs have a tendency to aggregate, forming “clumps” of tubes. To utilize their outstanding properties in applications, they need to be dispersed. But they are insoluble in many liquids, making their even dispersion difficult.

Scientists at Japan’s Kyushu University developed a technique that “exfoliates” aggregated clumps of CNTs and disperses them in solvents. It involves wrapping the tubes in a polymer using a bond that does not involve the sharing of electrons. The technique is called non-covalent polymer wrapping. Whereas sharing electrons through covalent polymer wrapping leads to a more stable bond, it also changes the intrinsic desirable properties of the carbon nanotubes. Non-covalent wrapping is thus considered superior in most cases because it causes minimum damage to the tubes.

The scientists, Dr. Tsuyohiko Fujigaya and Dr. Naotoshi Nakashima, conducted a research review to analyze the various approaches of polymer wrapping and to summarize the applications in which polymer-wrapped carbon nanotubes can be used. Their review has been published in Science and Technology of Advanced Materials (16-2 p24802, 2015).

They found that a wide variety of polymers can be used for the non-covalent wrapping of carbon nanotubes. Recently, many polymer dispersants have indeed been developed that not only disperse the CNTs but also add new functions to them. These polymer dispersants are now widely recognized and utilized in many fields, including biotechnology and energy applications.

Carbon nanotubes wrapped in polymer dispersants are used in many fields, including biotechnology and energy

CNTs that are stably wrapped with biocompatible materials are very attractive in biomedicine, for example, due to their incredible ability to pass biological barriers without generating an immune response. There is thus high potential for polymer-wrapped CNTs in the area of drug delivery.

Also, wrapping carbon nanotubes in polymers improves their photovoltaic functions in solar cells, for example, when the polymers function like a light-receiving pigment.

Because the designs of polymers can be readily tailored, it is expected that the functionality of polymer-wrapped CNTs will be further expanded and that novel applications using them will be developed.

Explore further: Understanding the reinforcing ability of carbon nanotubes

 

Berkley Lab: Electric Car Range Anxiety? Electric Vehicles May Be More Useful Than Previously Thought

Berkeley Lab study finds EV batteries have a longer useful life than current standards suggest.

In the first study of its kind, scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) quantitatively show that electric vehicles (EVs) will meet the daily travel needs of drivers longer than commonly assumed. Many drivers and much prior literature on the retirement of EV batteries have assumed that EV batteries will be retired after the battery has lost 20 percent of its energy storage or power delivery capability. This study shows that the daily travel needs of drivers continue to be met well beyond these levels of battery degradation.

Samveg Saxena, who leads a vehicle powertrain research program at Berkeley Lab, analyzed real-world driving patterns and found that batteries that have lost 20 percent of their originally rated energy storage capacity can still meet the daily travel needs of more than 85 percent of U.S. drivers. He and his research team also analyzed battery power fade and found that even after substantial loss in battery power capabilities performance requirements are still met.

“There are two main reasons people are hesitant to buy an EV: first, they’re unsure it will satisfy their mobility needs, and second, they’re afraid the battery won’t last the whole life of the car and they’ll have to replace it for a lot of money,” said Saxena, who has a PhD in mechanical engineering. “We show that, even after substantial battery degradation, the daily travel needs of most people are still going to be met.”

The analysis of battery life was published online recently with open access in the Journal of Power Sources, “Quantifying EV battery end-of-life through analysis of travel needs with vehicle powertrain models,” which Saxena co-authored with Jason MacDonald of Berkeley Lab and Caroline Le Floch and Scott Moura of UC Berkeley.

With today’s EV batteries, “end of life” is commonly defined as when the storage capacity drops down to 70 to 80 percent of the original capacity. As capacity fades, the vehicle’s range decreases. The Berkeley Lab researchers decided to investigate the extent to which vehicles still meet the needs of drivers beyond this common battery retirement threshold.

To conduct the study, the researchers took nearly 160,000 actual driving itineraries from the National Household Travel Survey conducted by the Department of Transportation. These are 24-hour travel itineraries showing when a car was parked or driving, including both weekend and weekday usage by drivers across the United States.

The researchers then assumed all itineraries were driven using a vehicle with specifications similar to a Nissan Leaf, which has about 24 kilowatt-hours of energy storage capacity, similar to many other EVs on the market, and 400 kW of discharge power capability, which was based on battery cell-level measurement data for the chosen vehicle.

This data was fed into the team’s unique simulation tool, V2G-Sim, or Vehicle-to-Grid Simulator. Developed by Saxena and other Berkeley Lab researchers, V2G-Sim quantifies second-by-second energy use while driving or charging for any number of different vehicle or charger types under varying driving conditions.

Then for each of the itineraries, they changed different variables, including not only the battery’s energy storage capacity, but also when the car was charged (for example, level 1 charger [standard 120V outlet] at home only, level 1 charger at home and work, level 2 charger [240V outlet] at home and level 1 charger at work, and so on), whether it was city or highway driving, whether the air conditioner was on, and whether the car was being driven uphill. More than 13 million individual daily state-of-charge profiles were computed.

“People have commonly thought, ‘if I buy an EV, I’ll have to replace the battery in a few years because I’ll lose the ability to satisfy my driving needs, and it’s not worth it,’” Saxena said. “We have found that only a small fraction of drivers will no longer be able to meet their daily driving needs after having lost 20 percent of their battery’s energy storage capabilities. It is important to remember that the vast majority of people don’t drive more than 40 miles per day on most days, and so they have plenty of reserve available to accommodate their normal daily trips even if they lose substantial amounts of battery capacity due to degradation.”

As the battery continues to degrade down to 50 percent of its original energy storage capacity, the research found that the daily travel needs of more than 80 percent of U.S. drivers can still be met, and at 30 percent capacity, 55 percent of drivers still have their daily needs met. “Even if a driver has a long, unexpected trip beyond the normal daily travel, an EV battery with substantial capacity fade can often still make the trip,” Saxena said.

The Berkeley Lab scientists also analyzed power capacity fade, or the declining ability of the battery to deliver power, such as when accelerating on a freeway onramp, as it ages. They modeled the impact of power fade on a vehicle’s ability to accelerate as well as to climb steep hills and complete other drive cycles. They found that power fade for the chosen vehicle does not have a significant impact on an EV’s performance, and that a battery’s retirement will be driven by energy capacity fade rather than by power fade.

“In fact, our analysis showed that the battery pack we studied, the Nissan Leaf, has a large margin of extra power capability,” Saxena said. “Energy capacity fade is really the limiting factor for this vehicle, not power fade.”

The researchers thus conclude that “range anxiety may be an over-stated concern” since EVs can meet the daily travel needs of more than 85 percent of U.S. drivers even after losing 20 percent of their originally rated battery capacity. They also conclude that batteries can “satisfy daily mobility requirements for the full lifetime of an electric vehicle.”

Given these results, the authors propose that an EV battery’s actual retirement may be delayed to when it can no longer meet the daily travel needs of a driver, leading many EV batteries to have a longer lifetime than is commonly assumed. Future work will involve providing personalized EV information for drivers, which takes into account an individual’s driving behavior.

“In sum, we can lose a lot of storage and power capability in a vehicle like a Leaf and still meet the needs of drivers,” Saxena said.

This research was funded through the Laboratory Directed Research and Development (LDRD) program at Berkeley Lab. V2G-Sim is available for licensing through Berkeley Lab’s Innovation and Partnerships Office.

# # #

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.

DOE’s Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

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Updated: March 30, 2015

Roll-Up Your TV Screen and Store It Away! How is that Possible?!

From smartphones and tablets to computer monitors and interactive TV screens, electronic displays are everywhere. As the demand for instant, constant communication grows, so too does the urgency for more convenient portable devices — especially devices, like computer displays, that can be easily rolled up and put away, rather than requiring a flat surface for storage and transportation.

A new Tel Aviv University study, published in Nature Nanotechnology, suggests that a novel DNA-peptide structure can be used to produce thin, transparent, and flexible screens. The research, conducted by Prof. Ehud Gazit and doctoral student Or Berger of the Department of Molecular Microbiology and Biotechnology at TAU’s George S. Wise Faculty of Life Sciences, in collaboration with Dr. Yuval Ebenstein and Prof. Fernando Patolsky of the School of Chemistry at TAU’s Faculty of Exact Sciences, harnesses bionanotechnology to emit a full range of colors in one pliable pixel layer — as opposed to the several rigid layers that constitute today’s screens.

“Our material is light, organic, and environmentally friendly,” says Prof. Gazit. “It is flexible, and a single layer emits the same range of light that requires several layers today. By using only one layer, you can minimize production costs dramatically, which will lead to lower prices for consumers as well.”

For the purpose of the study, a part of Berger’s Ph.D. thesis, the researchers tested different combinations of peptides: short protein fragments, embedded with DNA elements which facilitate the self-assembly of a unique molecular architecture.

Peptides and DNA are two of the most basic building blocks of life. Each cell of every life form is composed of such building blocks. In the field of bionanotechnology, scientists utilize these building blocks to develop novel technologies with properties not available for inorganic materials such as plastic and metal.

“Our lab has been working on peptide nanotechnology for over a decade, but DNA nanotechnology is a distinct and fascinating field as well. When I started my doctoral studies, I wanted to try and converge the two approaches,” says Berger. “In this study, we focused on PNA — peptide nucleic acid, a synthetic hybrid molecule of peptides and DNA. We designed and synthesized different PNA sequences, and tried to build nano-metric architectures with them.”

Using methods such as electron microscopy and X-ray crystallography, the researchers discovered that three of the molecules they synthesized could self-assemble, in a few minutes, into ordered structures. The structures resembled the natural double-helix form of DNA, but also exhibited peptide characteristics. This resulted in a very unique molecular arrangement that reflects the duality of the new material.

“Once we discovered the DNA-like organization, we tested the ability of the structures to bind to DNA-specific fluorescent dyes,” says Berger. “To our surprise, the control sample, with no added dye, emitted the same fluorescence as the variable. This proved that the organic structure is itself naturally fluorescent.”

The structures were found to emit light in every color, as opposed to other fluorescent materials that shine only in one specific color. Moreover, light emission was observed also in response to electric voltage — which make it a perfect candidate for opto-electronic devices like display screens.

The study was funded by the Momentum Fund of Ramot, TAU’s technology transfer company, which also patented the new technology. The researchers are currently building a prototype of the screen and are in talks with major consumer electronics companies regarding the technology.

Release Date: March 31, 2015
Source: Tel Aviv University

Water & Wastewater Treatment: Organics & Micro-Pollutants: Graphene Materials Company Ariva Secures £4m Funding

Innovative water and wastewater treatment company Arvia^TM Technology has secured £4 million in its latest round of investment funding. The company is now embarking on a series of demonstration installations in industrial treatment facilities.

Arvia has developed its own graphene-based proprietary material – Nyex^TM – which removes organics, emerging contaminants and micro-pollutants from wastewater and is regenerated in-situ in the novel organics destruction cell (ODC) process. The technology was spun-out of Manchester University’s School of Chemical Engineering.

Arvia’s modular treatment units can remove and oxidise low, trace toxic and problematic pollutants. These include metaldehyde, which is used by farmers in slug pest control and endocrine-disrupting and problem chemicals used in thepharmaceutical industry andpersonal care products, including triclosan.

Arvia Chief Executive Mike Lodge said:

“This is a very exciting time for Arvia Technology. We now have in place the secure financial backing required to strengthen our team and launch Arvia’s game-changing products into the water sector.”

“We have numerous test units to deploy into the market and we are looking for early adopters to collaborate with Arvia in applying this technology, which is changing the boundaries of how water is treated.”

The advanced treatment units can treat emerging contaminants and priority substances can be configured with the appropriate number of ODCs based on organics concentrations in a given waste stream. Units can be placed in series to manage a range of flow volumes from a few cubic metres per day to over 2,000 cubic metres per hour.

Organics can be treated at source and Arvia is now identifying companies in the industrial, pharmaceutical, herbicide and chemical sectors with problematic wastes.

Nanotechnology: It Isn’t Science Fantasy: NASA Nanotechnology Project

ORLANDO, FLA. — Nanotechnology is fast moving from the world of science fiction to science fact, with developments and applications that will ultimately create new, lighter and stronger materials that it is hoped will benefit business and public alike. So said Michael Meador, manager of NASA’s Game Changing Development Program’s Nanotechnology Project, at an Antec session at NPE 2015 in Orlando March 23.Meador, who also is chief of NASA’s Glenn Polymers Branch and is currently on loan to the White House Office of Science and Technology as director of the National Nanotechnology Coordination Office, said he and his colleagues at the National Nanotechnology Institute were pursuing a vision set out by President Clinton in a speech 15 years  ago to produce lighter,  stronger and more durable materials.

The NNI has been funded to the tune of $22 billion since its creation, but nanotechnology research is not just an expensive pipe dream for white-coated scientists. It has already found its way into a number of products: silica aerogels were in use on insulation materials for batteries on the Mars Rover, while a carbon nanotube-based sensor was used on the International Space Station.

An element of Clinton’s vision was the ability of nanotechnology to increase the capacity to store huge amounts of data in smaller and smaller devices, and detect cancer tumors within a small number of cells.

But it appears that aerospace will be where much of the potential lies. Ultra-lightweight structural nanomaterials can reduce the density of state-of-the-art structural composites by 50 percent and yet have  the same or better properties.

Using such technology, the weight of a space vehicle could potentially be reduced by up to 30 percent, which Meador described as a “game changer.” Meanwhile, the use of carbon nanotubes for cables can reduce the amount of material used in commercial aircraft, as well as spacecraft, leading to yet more weight reduction.

Crucially, Meador said the future direction of nanotechnology lies in its intersection with other industries — advanced manufacturing, precision medicine, brain research and anti-microbial resistant bacteria — and opportunities for collaboration and new applications.

There are enormous possibilities surrounding developments in changing the properties of a range of structures, some of which currently remained undiscovered, he added.

Binding Pollutants in Water with Polymeric Adsorber Materials

New types of membrane adsorbers remove unwanted particles from water and also, at the same time, dissolved substances such as the hormonally active bis-phenol A or toxic lead. To do this, researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB imbed selective adsorber particles in filtration membranes.

It was not until January 2015 that the European Food Safety Authority (EFSA) lowered the threshold value for bisphenol A in packaging. The hormonally active bulk chemical is among other things a basic material for polycarbonate from which, for example, CDs, plastic tableware or spectacles glasses are manufactured. Due to its chemical structure, bisphenol A is not completely degraded in the biological stages of treatment plants and is discharged into rivers and lakes by the purification facility.

Activated carbon or adsorber materials are already used to remove chemicals, anti-biotics or heavy metals from waste or process water. However, a disadvantage of these highly porous materials is the long contact time that the pollutants require to diffuse into the pores. So that as many of the harmful substances as possible are captured even in a shorter time, the treatment plants use larger quantities of adsorbers in correspondingly large treatment basins. However, activated carbon can only be regenerated with a high energy input, resulting for the most part in the need to dispose of large quantities of material contaminated with pollutants.

Also, membrane filtration with nanofiltration or reverse osmosis membranes, which can remove the contaminating substances, is not yet cost-effective for the removal of dissolved molecules from high-volume flows such as process or wastewater. Membranes filter the water through their pores when a pressure is built up on one side of the membrane, thus holding back larger molecules and solid particles. But the smaller the membrane pores are, the higher the pressure – and therefore the more energy – that is required to separate the substances from water.

Membrane adsorbers – filtering and binding in one step

Researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart have opted for a new approach that combines the advantages of both methods. When manufacturing the membranes they add small, polymeric adsorber particles. The resulting membrane adsorbers can – in addition to their filtration function – adsorptively bind substances dissolved in water.

“We make use of the porous structure of the membrane located underneath the separation layer. The pores have a highly specific surface so that as many particles as possible can be imbedded, and they also provide optimum accessibility,” says Dr. Thomas Schiestel, Head of the “Inorganic Interfaces and Membranes” working group at the Fraunhofer IGB.

“Unlike conventional adsorbers, our membrane adsorbers transport the pollutants convectively. This means that, with the water flowing rapidly through the membrane pores, a contact time lasting only a few seconds is sufficient to adsorb pollutants on the particle surface,” says the scientist. Up to 40 percent of the weight of the membrane adsorbers is accounted for by the particles, so their binding capacity is correspondingly high. At the same time the membrane adsorbers can be operated at low pressures. As the membranes can be packed very tightly, very large volumes of water can be treated even with small devices.

Functional adsorber particles

The researchers manufacture the adsorber particles in a one-step, cost-efficient process. In this patented process monomeric components are polymerized with the help of a crosslinking agent to generate 50 to 500 nanometer polymer globules. “Depending on which substances are to be removed from the water, we select the most suitable one from a variety of monomers with differing functional groups,” Schiestel explains. The spectrum here ranges from pyridine, which tends to be hydrophobic, by way of cationic ammonium compounds and includes anionic phosphonates.

Selective removal of pollutants and metals

The researchers were able to show in various tests that the membrane adsorbers remove pollutants very selectively by means of the particles, which are customized for the particular contaminant in question. For example, membrane adsorbers with pyridine groups bind the hydrophobic bisphenol A especially well, whereas those with amino groups adsorb the negatively charged salt of the antibiotic penicillin G.

“The various adsorber particles can even be combined in one membrane. In this way we can remove several micropollutants simultaneously with just one membrane adsorber,” says Schiestel, pointing out a further advantage. Equipped with different functional groups, the membrane adsorbers can also remove toxic heavy metals such as lead or arsenic from the water. Phosphonate membrane adsorbers, for example, adsorb more than 5 grams of lead per square meter of membrane surface area – 40 percent more than a commercially available membrane adsorber.

Cost-effective and regenerable

So that the membrane adsorbers can be used several times, the adsorbed pollutants have to be detached once again from the particles in the membrane. “Membrane adsorbers for bisphenol A can be fully regenerated by a shift of the pH value,” Schiestel explains. The concentrated pollutants can then be disposed off cost-effectively or broken down using suitable oxidative processes.

The regenerability of the membrane adsorbers also makes possible a further application: reutilization of the separated molecules. This additionally makes the technology attractive for recovering valuable precious metals or rare earth metals.

Explore further: Study demonstrates desalination with nanoporous graphene membrane

MIT: Cheap – Flexible – Solar – Really?

Tuning energy levels through surface chemistry shows promise for higher efficiency quantum dot solar cells, MIT graduate student Patrick R. Brown’s work shows.

Solar cells made out of lead sulfide quantum dots could eventually offer a cheaper, more flexible alternative to ones made using silicon, but they are currently much less efficient. However, altering the chemical composition of quantum-dot solar cells offers a way of tuning them to reach higher efficiencies, MIT physics graduate student Patrick R. Brown says.

“Instead of starting with a high-efficiency technology and then trying to make it cheaper, which is what we’re doing now with silicon, our plan is to start with something that we know we could make cheaply and see if we could make it more efficient,” Brown explains.

Lead sulfide is plentiful, occurring naturally in the mineral galena, and the world currently produces enough lead and sulfur in the span of a few weeks to build lead sulfide solar cells to supply all the world’s electricity, Brown notes. Other alternatives to silicon such as cadmium telluride or copper indium gallium diselenide (CIGS) have the disadvantage of using costlier and less-abundant starting materials. Lead sulfide quantum dots have another advantage over other emerging thin-film solar-cell technologies like organic polymers and perovskites in that they are stable in air.

“I’m focusing on trying to figure out what are the knobs that we have to turn on this material that will then enable us to get to higher efficiency,” Brown says.

Ligands alter energy levels

Quantum dots are nanoscale crystalline semiconductors whose bandgap changes with their size. The bandgap determines which regions of the solar spectrum — which contains ultraviolet, visible, and infrared light — that the quantum dot solar cells can absorb and convert to electricity.

Brown’s recent collaborative research with MIT Professor Vladimir Bulović and five others demonstrated how attaching different organic molecules, or ligands, to the surface of quantum dots can modify their energy level. Brown fabricated and studied his lead sulfide quantum-dot solar cells in Bulović’s Organic and Nanostructured Electronics Lab.

When sunlight strikes a semiconductor in a solar cell, it can excite an electron from its tightly-bound ground state in the “valence band” into less-tightly-bound states in the “conduction band,” where the electrons can move freely and generate an electric current. Brown studied the influence that different chemical ligands have on the ground-state energies of electrons in the quantum-dot valence band.

Using a technique known as ultraviolet photoelectron spectroscopy in the lab of MIT Professor Marc A. Baldo, Brown measured the differing electronic properties of lead sulfide quantum dot films treated with 12 different chemical ligands. The results show that these surface ligands act as tiny electric dipoles — the electrical equivalent of the familiar bar magnet — and thus can influence the energy of the electrons within a quantum dot.

Guiding efficient design

“In our work, we show that as you change the surface ligands, you can leave the bandgap the same, but change the absolute energy levels,” Brown says. The ability to tune both the size of the quantum dot and its surface chemistry can guide the design of efficient solar cells and, eventually, multi-junction devices that absorb more of the sun’s spectrum. “With this ability to tune the energy levels of the quantum dots by changing the ligands, we can make sure that there are no energetic barriers in our device and that the electrons have a downhill energetic path out of the device,” Brown explains. “The ability to tune these properties using such simple chemical processes is what sets these materials apart, making them a unique and promising choice for use in solar cells,” Brown says.

Brown and MIT materials science graduate student Donghun Kim were co-lead authors of the paper, “Energy Level Modification in Lead Sulfide Quantum Dot Thin Films through Ligand Exchange,” published in ACS Nano in June 2014. Other co-authors were MIT Professors Vladimir Bulović, Jeffrey C. Grossman, and Moungi G. Bawendi, as well as Richard R. Lunt, assistant professor of chemical engineering and materials science at Michigan State University, and Ni Zhao, assistant professor of electronic engineering at the Chinese University of Hong Kong. Brown, 27, is in his sixth year as a physics graduate student and expects to get his PhD during 2015. He received his BS in physics and chemistry at the University of Notre Dame. Brown is a National Science Foundation Fellow as well as a Fannie and John Hertz Foundation Fellow.

Kim used atomic-scale computer simulations to model the interactions of the chemical ligands with the quantum-dot surface. These simulations explained a key result of the study, showing that the differing electric dipole moments of the ligands are responsible for the changes in quantum dot energy levels. “Regardless of the way that a specific ligand binds to the quantum dot surface, Donghun’s simulations showed a shift in energy levels that matched the shifts that we were measuring experimentally,” Brown says.

Meeting world demand

To supply a major portion of the world’s energy demand with photovoltaics, tens of thousands of square kilometers of solar cells would need to be installed, Brown says. Silicon-based solar cells are efficient and getting cheaper as more are made, but their brittle nature means that they must be encapsulated by rigid, relatively heavy aluminum-and-glass frames.

“The key idea with quantum dots is that instead of starting from big crystals of silicon that must be sliced into single wafers, we start with very tiny crystals, roughly 10 nanometers in diameter, which we can dissolve in solution and print out like an ink. So instead of being tied to these rigid glass substrates, we could eventually be able to print or spray our solar cells onto flexible substrates like you would print a newspaper,” Brown says. “Those are the kinds of things that you wouldn’t be able to do with a silicon wafer.”

Quantum dots do have their disadvantages, of course, which is why this technology hasn’t yet hit the market. “Electrons have a harder time hopping between quantum dots than they do traveling through a pure, uniform crystal of silicon. While the materials we are using are very cheap, the difficulty in moving charge through them leads to low solar cell efficiencies,” Brown says. For example, electrons can get trapped on the surfaces of quantum dots. “One thing we want to do is figure out what kind of chemical tricks we can play at the surface of the quantum dot to get rid of those trap states,” he says.

The long-term goal of the research is to use the tunable electronic properties to make higher-efficiency lead sulfide quantum-dot solar cells that are flexible and able to be manufactured at low cost, Brown says.