David L. Chandler, MIT News Office
Quantum dots — tiny particles that emit light in a dazzling array of glowing colors — have the potential for many applications, but have faced a series of hurdles to improved performance. But an MIT team says that it has succeeded in overcoming all these obstacles at once, while earlier efforts have only been able to tackle them one or a few at a time.
Quantum dots — in this case, a specific type called colloidal quantum dots — are tiny particles of semiconductor material that are so small that their properties differ from those of the bulk material: They are governed in part by the laws of quantum mechanics that describe how atoms and subatomic particles behave. When illuminated with ultraviolet light, the dots fluoresce brightly in a range of colors, determined by the sizes of the particles.
First discovered in the 1980s, these materials have been the focus of intense research because of their potential to provide significant advantages in a wide variety of optical applications, but their actual usage has been limited by several factors. Now, research published this week in the journal Nature Materials by MIT chemistry postdoc Ou Chen, Moungi Bawendi, the Lester Wolfe Professor of Chemistry, and several others raises the prospect that these limiting factors can all be overcome.
The new process developed by the MIT team produces quantum dots with four important qualities: uniform sizes and shapes; bright emissions, producing close to 100 percent emission efficiency; a very narrow peak of emissions, meaning that the colors emitted by the particles can be precisely controlled; and an elimination of a tendency to blink on and off, which limited the usefulness of earlier quantum-dot applications.
Multicolored biological dyes
For example, one potential application of great interest to researchers is as a substitute for conventional fluorescent dyes used in medical tests and research. Quantum dots could have several advantages over dyes — including the ability to label many kinds of cells and tissues in different colors because of their ability to produce such narrow, precise color variations. But the blinking effect has hindered their use: In fast-moving biological processes, you can sometimes lose track of a single molecule when its attached quantum dot blinks off.
Previous attempts to address one quantum-dot problem tended to make others worse, Chen says. For example, in order to suppress the blinking effect, particles were made with thick shells, but this eliminated some of the advantages of their small size.
The small size of these new dots is important for potential biological applications, Bawendi explains. “[Our] dots are roughly the size of a protein molecule,” he says. If you want to tag something in a biological system, he says, the tag has got to be small enough so that it doesn’t overwhelm the sample or interfere significantly with its behavior.
Quantum dots are also seen as potentially useful in creating energy-efficient computer and television screens. While such displays have been produced with existing quantum-dot technology, their performance could be enhanced through the use of dots with precisely controlled colors and higher efficiency.
Combining the advantages
So recent research has focused on “the properties we really need to enhance [dots’] application as light emitters,” Bawendi says — which are the properties that the new results have successfully demonstrated. The new quantum dots, for the first time, he says, “combine all these attributes that people think are important, at the same time.”
The new particles were made with a core of semiconductor material (cadmium selenide) and thin shells of a different semiconductor (cadmium sulfide). They demonstrated very high emission efficiency (97 percent) as well as small, uniform size and narrow emission peaks. Blinking was strongly suppressed, meaning the dots stay “on” 94 percent of the time.
A key factor in getting these particles to achieve all the desired characteristics was growing them in solution slowly, so their properties could be more precisely controlled, Chen explains. “A very important thing is synthesis speed,” he says, “to give enough time to allow every atom to go to the right place.”
The slow growth should make it easy to scale up to large production volumes, he says, because it makes it easier to use large containers without losing control over the ultimate sizes of the particles. Chen expects that the first useful applications of this technology could begin to appear within two years.
Taeghwan Hyeon, director of the Center for Nanoparticle Research at Seoul National University in Korea, who was not involved in this research, says, “It is very impressive, because using a seemingly very simple approach — that is, maintaining a slow growth rate — they were able to precisely control shell thickness, enabling them to synthesize highly uniform and small-sized quantum dots.” This work, he says, solves one of the “key challenges” in this field, and “could find biomedical imaging applications, and can be also used for solid-state lighting and displays.”
In addition to Chen and Bawendi, the team included seven other MIT students and postdocs and two researchers from Massachusetts General Hospital and Harvard Medical School. The work was supported by the National Institutes of Health, the Army Research Office through MIT’s Institute for Soldier Nanotechnologies, and by the National Science Foundation through the Collaborative Research in Chemistry Program.
Hydrogen generated through the photochemical cleavage of water using renewable solar energy is considered to be an environmentally friendly chemical fuel of the future, which neither results in air pollution nor leads to the emission of greenhouse gases. The photocatalytic materials for water cleavage are required to perform at least two fundamental functions: light harvesting of the maximal possible part of the solar energy spectrum and a catalytic function for efficient water decomposition into oxygen and hydrogen. Photocatalytic systems based on colloidal semiconductor nanocrystals offer a number of advantages in comparison with photoelectrochemical cells based on bulk electrodes: (i) a broad range of material types are available; (ii) higher efficiencies are expected due to short distance charge transport; (iii) large surface areas are beneficial for the catalytic processes; (iv) flexibility in fabrication and design which also allows for tuning of the electronic and optical properties by employing quantum confinement effects. The presence of co-catalysts on colloidal semiconductors is an important part of the overall design of the photocatalytic colloidal systems necessary to maximize the water splitting efficiency. This review article discusses the rational choice of colloidal nanoheterostructured materials based on light-harvesting II–VI semiconductor nanocrystals combined with a variety of metal and/or non-metal co-catalysts, with optimized light harvesting, charge separation, and photocatalytic functions.
BALTIMORE, March 18, 2013 – Lockheed Martin [NYSE: LMT] has been awarded a patent for Perforene™ material, a molecular filtration solution designed to meet the growing global demand for potable water.
The Perforene material works by removing sodium, chlorine and other ions from sea water and other sources.
“Access to clean drinking water is going to become more critical as the global population continues to grow, and we believe that this simple and affordable solution will be a game-changer for the industry,” said Dr. Ray O. Johnson, senior vice president and chief technology officer of Lockheed Martin. “The Perforene filtration solution is just one example of Lockheed Martin’s efforts to apply some of the advanced materials that we have developed for our core markets, including aircraft and spacecraft, to global environmental and economic challenges.”
The Perforene membrane was developed by placing holes that are one nanometer or less in a graphene membrane. These holes are small enough to trap the ions while dramatically improving the flow-through of water molecules, reducing clogging and pressure on the membrane.
At only one atom thick, graphene is both strong and durable, making it more effective at sea water desalination at a fraction of the cost of industry-standard reverse osmosis systems.
In addition to desalination, the Perforene membrane can be tailored to other applications, including capturing minerals, through the selection of the size of hole placed in the material to filter or capture a specific size particle of interest. Lockheed Martin has also been developing processes that will allow the material to be produced at scale.
The company is currently seeking commercialization partners.
The patent was awarded by the United States Patent and Trademark Office.
Headquartered in Bethesda, Md., Lockheed Martin is a global security and aerospace company that employs about 120,000 people worldwide and is principally engaged in the research, design, development, manufacture, integration and sustainment of advanced technology systems, products and services. The Corporation’s net sales for 2012 were $47.2 billion.
Using an approach akin to assembling a club sandwich at the nanoscale, NIST researchers have succeeded in crafting a uniform, multi-walled carbon nanotube-based coating that greatly reduces the flammability of foam commonly used in upholstered furniture and other soft furnishings.
The flammability of the nanotube-coated polyurethane foam was reduced 35% compared with untreated foam. As important, the coating prevented melting and pooling of the foam, which generates additional flames that are a major contributor to the spread of fires.
Nationwide, fires in which upholstered furniture is the first item ignited account for about 6,700 home fires annually and result in 480 civilian deaths, or almost 20% of home fire deaths between 2006 and 2010, according to the National Fire Protection Association.
The innovative NIST technique squeezes nanotubes between two everyday polymers and stacks four of these trilayers on top of each other. The result is a plastic-like coating that is thinner than one-hundredth the diameter of human hair and has flame-inhibiting nanotubes distributed evenly throughout.
The brainchild of NIST materials scientists Yeon Seok Kim and Rick Davis, the fabrication method is described in Thin Solid Films. Kim and Davis write that the technique can be used with a variety of types of nanoparticles to improve the quality of surface coatings for diverse applications.
The pair experimented with a variety of layer-by-layer coating methods before arriving at their triple-decker approach. All had failed to meet their three key objectives: entire coverage of the foam’s porous surface, uniform distribution of the nanotubes and the practicality of the method. Inmost of these trials, the nanotubes—cylinders of carbon atoms resembling rolls of chicken wire—didn’t adhere strongly to the foam surface.
So, Kim and Davis opted to doctor the nanotubes themselves, borrowing a technique often used in cell culture to make DNA molecules stickier. The method attached nitrogen-containing molecules—called amine groups—to the nanotube exteriors.
This step proved critical: The doctored nanotubes were uniformly distributed and clung tenaciously to the polymer layers above and below. As a result, the coating fully exploits the nanotubes’ rapid heat-dissipating capability.
Gram for gram, the resulting coating confers much greater resistance to ignition and burning than achieved with the brominated flame retardants commonly used to treat soft furnishings today. As important, says Davis, a “protective char layer” forms when the nanotube-coated foam is exposed to extreme heat, creating a barrier that prevents the formation of melt pools.
“This kind of technology has the potential to reduce the fire threat associated with burning soft furniture in homes by about a third,” Davis says.
SINGAPORE, Jan. 14, 2014 /PRNewswire/ — Micro-Sphere SA (MS) and NanoMaterials Technology Private Limited (NMT) jointly announced today that both have formed technology partnership in combining MS’s spray drying technology and NMT’s High Gravity Controlled Precipitation (HGCP) Technology to provide development and manufacturing services to pharmaceutical, skincare and cosmetic companies.
Based on the partnership agreement, both parties shall collaborate together to work on new development or contract manufacturing projects using each party’s proprietary technology. MS shall leverage on its expertise in processing and formulation technologies such as emulsification and spray drying. NMT Singapore shall contribute on its experience in nanonization and formulation, and provide non-exclusive access to MS on its HGCP and related technologies for relevant projects.
“MS as high level contract production and development company is honored to have the possibility to deal with outstanding patented technology owned by NMT and to provide the necessary know-how to enable the positive outcome of the projects,” says Dr. Michele Muller, General Manager of MS.
“We have been working with MS on various projects and are delighted with their spray dying technology, the professionalism and the good quality of works by their team. With this partnership, we can combine the strengths of both companies and offer more solutions to our customers. This will also bring our business and technologies to the next level,” says David Sher, Managing Director of NMT.
About Micro-Sphere SA (http://www.micro-sphere.com)
Micro-Sphere (MS) is located in the south part of Switzerland and has grown up its know-how in spray drying over more than 10 years of practical experience on 90+ different active ingredients in the pharmaceutical field. All operations are performed according to cGMP, meeting the requirements of the Swiss / European and U.S. Authorities (FDA). MS has an important record of activity in the field of high potency actives substances in particular related to the inhalation of dry powders as well to the dispersion of water-insoluble molecules in nano-emulsions.
About NanoMaterials Technology Private Limited (http://www.nanomt.com)
Founded in April 2000, NanoMaterials Technology (NMT) is a Singapore company that specializes in the development and commercialization of nano-materials. NMT has a proprietary technology called High Gravity Controlled Precipitation (HGCP) Technology which is a simple and extremely cost effective mass production technology. The HGCP technology is versatile to be coupled with NMT’s patented dispersion technology and know how to improve the dispersibility of the nano-particles in pharmaceutical and specialty products.
WATERLOO, ON, Dec. 9, 2013 /CNW/ – A first-of-its-kind, world-class laboratory that could lead to the creation of quantum materials for use in a new generation of technologies will open at the University of Waterloo’s Institute for Quantum Computing (IQC) on December 12, 2103.
Quantum materials are needed as the building blocks of robust quantum devices that will be able to function outside of laboratory settings bringing the possibility of a quantum computer one step closer.
“New materials are not conventional, so we need to take an unconventional approach to this research,” said Professor David Cory, Canada Excellence Research Chair and deputy director, research at IQC. “The Institute for Quantum Computing has made a significant investment in quantum materials science and the most promising direction for building quantum devices is quantum materials.”
The lab houses a unique new $5 million tool to grow new materials that could form the building blocks of quantum technologies.
The Government of Canada, Canada Foundation for Innovation, the Ontario Research Fund, industry partners and others helped fund the new lab.
Media are invited to attend an event to open the laboratory. The event includes remarks from Professor Cory, and Professor Raymond Laflamme, executive director of Waterloo’s IQC.
Tours of the new laboratory are available.
Title: Quantum Dots Market by Product (QD Displays, Lasers, Medical Devices, Solar Cells, Chip, Sensor), Application (Healthcare, Optoelectronics, Sustainable Energy), Material (Cadmium Selenide, Sulfide, Telluride), and Geography – Forecast & Analysis (2013 – 2020).
Quantum Dots (QD) are the types of semiconductor nanoparticles, which find their usage in multiple applications like healthcare, electronics, and so on. The current market of QD is at the pre-commercialized stage; most of the researchers are working on the “application aspects” of the QD technology, and deriving the products based on QD.
Researchers have studied the quantum dots in transistors, solar cells, LEDs, and diode lasers. They have also investigated quantum dots as agents for medical imaging and, soon, the QDs will be used as ‘qubits’ in quantum computing.
This report deals with all the driving factors, restraints, and opportunities for the QD technology market, which are helpful in identifying the trends and key success factors for the industry. The report also profiles companies that are active in the field of QD technology. It also highlights the winning imperatives and burning issues pertaining to the QD technology industry.
The Quantum Dots market is expected to grow from the $108.41 million that it accounts for, currently, in 2013 to $3,414.54 million in 2020, at a CAGR of 71.13% from 2014 to 2020. Optoelectronics application is expected to be the major market share holder, with an expected revenue generation of $2,458.47 million in 2020.
PALO ALTO, Calif. — Not long after Gordon E. Moore proposed in 1965 that the number of transistors that could be etched on a silicon chip would continue to double approximately every 18 months, critics began predicting that the era of “Moore’s Law” would draw to a close.
More than ever recently, industry pundits have been warning that the progress of the semiconductor industry is grinding to a halt — and that the theory of Dr. Moore, an Intel co-founder, has run its course.
If so, that will have a dramatic impact on the computer world. The innovation that has led to personal computers, music players and smartphones is directly related to the plunging cost of transistors, which are now braided by the billions onto fingernail slivers of silicon — computer chips — that may sell for as little as a few dollars each.
But Moore’s Law is not dead; it is just evolving, according to more optimistic scientists and engineers. Their contention is that it will be possible to create circuits that are closer to the scale of individual molecules by using a new class of nanomaterials — metals, ceramics, polymeric or composite materials that can be organized from the “bottom up,” rather than the top down.
For instance, semiconductor designers are developing chemical processes that can make it possible to “self assemble” circuits by causing the materials to form patterns of ultrathin wires on a semiconductor wafer. Combining these patterns of nanowires with conventional chip-making techniques, the scientists believe, will lead to a new class of computer chips, keeping Moore’s Law alive while reducing the cost of making chips in the future.
“The key is self assembly,” said Chandrasekhar Narayan, director of science and technology at IBM’s Almaden Research Center in San Jose, Calif. “You use the forces of nature to do your work for you. Brute force doesn’t work any more; you have to work with nature and let things happen by themselves.”
To do this, semiconductor manufacturers will have to move from the silicon era to what might be called the era of computational materials. Researchers here in Silicon Valley, using powerful new supercomputers to simulate their predictions, are leading the way. While semiconductor chips are no longer made here, the new classes of materials being developed in this area are likely to reshape the computing world over the next decade.
“Materials are very important to our human societies,” said Shoucheng Zhang, a Stanford University physicist who recently led a group of researchers to design a tin alloy that has superconductinglike properties at room temperature. “Entire eras are named after materials — the stone age, the iron age and now we have the silicon age. In the past they have been discovered serendipitously. Once we have the power to predict materials, I think it’s transformative.”
Pushing this research forward is economics — specifically, the staggering cost semiconductor manufacturers are expecting to pay for their next-generation factories. In the chip-making industry this has been referred to as “Moore’s Second Law.”
Two years from now new factories for making microprocessor chips will cost from $8 to $10 billion, according to a recent Gartner report — more than twice as much as the current generation. That amount could rise to between $15 and $20 billion by the end of the decade, equivalent to the gross domestic product of a small nation.
The stunning expenditures that soon will be required mean that the risk of error for chip companies is immense. So rather than investing in expensive conventional technologies that might fail, researchers are looking to these new self-assembling materials.
What the scientists have proven is that they can create conductive thin films, which could be used in a range of applications, including photovoltaics, sensors and electronic materials.
The scientists said that they now see paths for moving beyond the conductive materials, toward creating semiconductors as well.
According to Mark D. Allendorf, a Sandia chemist, there are very few things that you can do with conventional semiconductorsto change the behavior of a material. With MOFs he envisions a future in which molecules can be precisely ordered to create materials with specific behaviors.
“One of the reasons that Sandia is well positioned is that we have huge supercomputers,” he said. They have been able to simulate matrixes of 600 atoms, large enough for the computer to serve as an effective test tube.
In November, scientists at the SLAC National Accelerator Laboratory, writing in the journal Physical Review Letters, described a new form of tin that, at only a single molecule thick, has been predicted to conduct electricity with 100 percent efficiency at room temperature. Until now these kinds of efficiencies have only been found in materials known as superconductors, and then only at temperatures near absolute zero.
The material would be an example of a new class of materials called “topological insulators” that are highly conductive along a surface or edge, but insulating on their interior. In this case the researchers have proposed a structure with fluorine atoms added to a single layer of tin atoms.
The scientists, led by Dr. Zhang, named the new material stanene, combining the Latin name for tin — stannum — with the suffix used for graphene, another material based on a sheet of carbon atoms a single molecule thick.
The promise of such a material is that it might be easily used in conjunction with today’s chip-making processes to both increase the speed and lower the power consumption of future generations of semiconductors.
The theoretical prediction of the material must still be verified, and Dr. Zhang said that research is now taking place in Germany and China, as well as a laboratory at U.C.L.A.
It is quite possible that the computational materials revolution may offer a path toward cheaper technologies for the next generation of computer chips.
That is IBM’s bet. The company is now experimenting with exotic polymers that automatically form into an ultrafine web and can be used to form circuit patterns onto silicon wafers.
Dr. Narayan is cautiously optimistic, saying there is a good chance that bottoms-up self-assembly techniques will eliminate the need to invest in new lithographic machines, costing $500 million, that use X-rays to etch smaller circuits. .
“The answer is possibly yes,” he said, in describing a lower cost path to denser computer chips.
Researchers have developed a technique for creating nanoparticles that carry two different cancer-killing drugs into the body and deliver those drugs to separate parts of the cancer cell where they will be most effective. The technique was developed by researchers at North Carolina State University and the University of North Carolina at Chapel Hill.
“In testing on laboratory mice, our technique resulted in significant improvement in breast cancer tumor reduction as compared to conventional treatment techniques,” says Dr. Zhen Gu, senior author of a paper on the research and an assistant professor in the joint biomedical engineering program at NC State and UNC-Chapel Hill.
“Cancer cells can develop resistance to chemotherapy drugs, but are less likely to develop resistance when multiple drugs are delivered simultaneously,” Gu says. “However, different drugs target different parts of the cancer cell. For example, the protein drug TRAIL is most effective against the cell membrane, while doxorubicin (Dox) is most effective when delivered to the nucleus. We’ve come up with a sequential and site-specific delivery technique that first delivers TRAIL to cancer cell membranes and then penetrates the membrane to deliver Dox to the nucleus.”
Gu’s research team developed nanoparticles with an outer shell made of hyaluronic acid (HA) woven together with TRAIL. The HA interacts with receptors on cancer cell membranes, which “grab” the nanoparticle. Enzymes in the cancer cell environment break down the HA, releasing TRAIL onto the cell membrane and ultimately triggering cell death.
When the HA shell breaks down, it also reveals the core of the nanoparticle, which is made of Dox that is embedded with peptides that allow the core to penetrate into the cancer cell. The cancer cell encases the core in a protective bubble called an endosome, but the peptides on the core cause the endosome to begin breaking apart. This spills the Dox into the cell where it can penetrate the nucleus and trigger cell death.
“We designed this drug delivery vehicle using a ‘programmed’ strategy,” says Tianyue Jiang, a lead author in Dr. Gu’s lab. “Different drugs can be released at the right time in their right places,” adds Dr. Ran Mo, a postdoctoral researcher in Gu’s lab and the other lead author.
“This research is our first proof of concept, and we will continue to optimize the technique to make it even more efficient,” Gu says. “The early results are very promising, and we think this could be scaled up for large-scale manufacturing.”
The paper, “Gel–Liposome-Mediated Co-Delivery of Anticancer Membrane-Associated Proteins and Small-Molecule Drugs for Enhanced Therapeutic Efficacy,” is published online in Advanced Functional Materials. Co-authors of the paper are Adriano Bellotti, an undergraduate at NC State, and Dr. Jianping Zhou, a professor at China Pharmaceutical University.
Note to Editors: The study abstract follows.
“Gel–Liposome-Mediated Co-Delivery of Anticancer Membrane-Associated Proteins and Small-Molecule Drugs for Enhanced Therapeutic Efficacy”
Authors: Tianyue Jiang, Ran Mo, and Zhen Gu, North Carolina State University and University of North Carolina at Chapel Hill; Adriano Bellotti, North Carolina State University; Jianping Zhou, China Pharmaceutical University.
Published: online Jan. 2, 2014, Advanced Functional Materials
Abstract: A programmed drug-delivery system that can transport different anticancer therapeutics to their distinct targets holds vast promise for cancer treatment. Herein, a core–shell-based “nanodepot” consisting of a liposomal core and a crosslinked-gel shell (designated Gelipo) is developed for the sequential and site-specific delivery (SSSD) of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and doxorubicin (Dox). As a small-molecule drug intercalating the nuclear DNA, Dox is loaded in the aqueous core of the liposome, while TRAIL, acting on the death receptor (DR) on the plasma membrane, is encapsulated in the outer shell made of crosslinked hyaluronic acid (HA). The degradation of the HA shell by HAase that is concentrated in the tumor environment results in the rapid extracellular release of TRAIL and subsequent internalization of the liposomes. The parallel activity of TRAIL and Dox show synergistic anticancer efficacy. The half-maximal inhibitory concentration (IC50) of TRAIL and Dox co-loaded Gelipo (TRAIL/Dox-Gelipo) toward human breast cancer (MDA-MB-231) cells is 83 ng mL–1 (Dox concentration), which presents a 5.9-fold increase in the cytotoxicity compared to 569 ng mL–1 of Dox-loaded Gelipo (Dox-Gelipo). Moreover, with the programmed choreography, Gelipo significantly improves the inhibition of the tumor growth in the MDA-MB-231 xenograft tumor animal model.