Posted: Mar 07, 2016
Luminescent quantum dots (LQDs), which possess high photoluminescence quantum yields, flexible emission color controlling, and solution processibility, are promising for applications in lighting systems (warm white light without UV and infrared irradiation) and high quality displays.
However, the commercialization of LQDs has been held back by the prohibitively high cost of their production. Currently, LQDs are prepared by the HI method, requiring at high temperature and tedious surface treating in order to improve both optical properties and stability.
In a breakthrough approach, researchers have now succeeded in preparing highly emissive inorganic perovskite quantum dots (IPQDs) at room temperature.
“Our synthesis technique is designed according to supersaturated recrystallization, which is operated at room temperature, within few seconds, free from inert gas and injection operation,” Professor Haibo Zeng, Director of the Institute of Optoelectronics & Nanomaterials at Nanjing University of Science and Technology, tells Nanowerk. “Although formed at room temperature, our IPQDs’ photoluminescence have quantum yields of 80%, 95%, 70%, and very small line-widths of 35, 20, and 18 nm for red, green, and blue emissions.”
Schematic of RT formation of IPQDs (CsPbX3 (X = Cl, Br, I)). a) The SR can be finished within 10 s through transferring the Cs+, Pb2+, and X- ions from the soluble to insoluble solvents at RT without any protecting atmosphere and heating. C: ion concentration in different solvents. C0: saturated solubilities in DMF, toluene, or mixed solvents (DMF+toluene). b) Clear toluene under a UV light. Snapshots of four typical samples after the addition of precursor ion solutions for 3 s, blue (c, Cl:Br = 1), green (d, pure Br), yellow (e, I:Br = 1), and red (f, I:Br = 1.5), respectively. (Reprinted with permission by Wiley-VCH Verlag) (click on image to enlarge)
Zeng and his team have reported their findings in the February 29, 2016 online edition of Advanced Functional Materials (“CsPbX3 Quantum Dots for Lighting and Displays: Room-Temperature Synthesis, Photoluminescence Superiorities, Underlying Origins and White Light-Emitting Diodes”).
The room temperature procedures developed by the researchers make scaled production possible so that gram-scale of quantum dots can be synthesized easily with very low cost and in short time.
Already applied in the production of some organic nanoparticles, under the assist of surfactants, a supersaturated recrystallization (SR) process can be applied to fabricate QDs with well size and composition controls in solutions, especially when considering the ionic crystal features of halide perovskites.
Zeng explains the process: “In supersaturated recrystallization, that is, when the constrainedly sustentative nonequilibrium state of a soluble system is activated by an accident, for example, stirring or impurity, the supersaturated ions will precipitate in the form of crystal, which is frequently observed in natural minerals, alloys, and ion solutions. Such spontaneous precipitation and crystallization reactions will not stop until the system reaches an equilibrium state again.”
He points out that the operation of his team’s SR synthesis is very simple, and can be summarized as transferring various inorganic ions from their very good into very poor solvents.
“So, when considering supersaturation-induced recrystallization and no usage of heating, it seems to be similar to solarizing seawater to obtain edible salt, which has been used for a long time in human history,” Zeng notes. “But the key point of SR process, the obtaining of supersaturated state, is achieved by using transfer from good into poor solvents in our work, but not the evaporation of solvent, which could be the reason why our IPQDs can be formed completely at room temperature and only need trace amount of energy.”
Controllable photoluminescence. a) Optical images of solution and film samples with different bandgaps under a 365 nm UV lamp. b) Optical absorption and c) photoluminescence spectra of IPQDs with different composition. (Reprinted with permission by Wiley-VCH Verlag)
Although developed only recently, inorganic halide perovskite quantum dot systems have exhibited comparable and even better performances than traditional QDs in many fields. With this novel room-temperature preparation technique, IPQDs’ superior optical merits could lead to promising applications in lighting and displays.
“Though more investigations are needed to reveal the correlations between structural – especially the surface states – and physical properties, our findings will provide good references and enhance researchers’ understanding of this quantum dot system, pushing it to a new research paradigm in the field of optoelectronic devices, as well as sensors and memristors,” concludes Zeng.
Genesis Nanotechnology, Inc. ~ “Great Things from Small Things”
26 Feb 2016
Nanoparticles form in a 3-D-printed microfluidic channel. Each droplet shown here is about 250 micrometers in diameter, and contains billions of platinum nanoparticles. Credit: Richard Brutchey and Noah Malmstadt/USC
Nanoparticles – tiny particles 100,000 times smaller than the width of a strand of hair – can be found in everything from drug delivery formulations to pollution controls on cars to HD TV sets. With special properties derived from their tiny size and subsequently increased surface area, they’re critical to industry and scientific research.
They’re also expensive and tricky to make.
Now, researchers at USC have created a new way to manufacture nanoparticles that will transform the process from a painstaking, batch-by-batch drudgery into a large-scale, automated assembly line.
The method, developed by a team led by Noah Malmstadt of the USC Viterbi School of Engineering and Richard Brutchey of the USC Dornsife College of Letters, Arts and Sciences, was published in Nature Communications on Feb. 23.
Consider, for example, gold nanoparticles. They have been shown to be able to easily penetrate cell membranes without causing any damage – an unusual feat, given that most penetrations of cell membranes by foreign objects can damage or kill the cell. Their ability to slip through the cell’s membrane makes gold nanoparticles ideal delivery devices for medications to healthy cells, or fatal doses of radiation to cancer cells.
However, a single milligram of gold nanoparticles currently costs about $80 (depending on the size of the nanoparticles). That places the price of gold nanoparticles at $80,000 per gram – while a gram of pure, raw gold goes for about $50.
“It’s not the gold that’s making it expensive,” Malmstadt said. “We can make them, but it’s not like we can cheaply make a 50 gallon drum full of them.”
Right now, the process of manufacturing a nanoparticle typically involves a technician in a chemistry lab mixing up a batch of chemicals by hand in traditional lab flasks and beakers.
Brutchey and Malmstadt’s new technique instead relies on microfluidics – technology that manipulates tiny droplets of fluid in narrow channels.
“In order to go large scale, we have to go small,” Brutchey said. Really small.
The team 3D printed tubes about 250 micrometers in diameter – which they believe to be the smallest, fully enclosed 3D printed tubes anywhere. For reference, your average-sized speck of dust is 50 micrometers wide.
They then built a parallel network of four of these tubes, side-by-side, and ran a combination of two non-mixing fluids (like oil and water) through them. As the two fluids fought to get out through the openings, they squeezed off tiny droplets. Each of these droplets acted as a micro-scale chemical reactor in which materials were mixed and nanoparticles were generated. Each microfluidic tube can create millions of identical droplets that perform the same reaction.
This sort of system has been envisioned in the past, but its hasn’t been able to be scaled up because the parallel structure meant that if one tube got jammed, it would cause a ripple effect of changing pressures along its neighbors, knocking out the entire system. Think of it like losing a single Christmas light in one of the old-style strands – lose one, and you lose them all.
Brutchey and Malmstadt bypassed this problem by altering the geometry of the tubes themselves, shaping the junction between the tubes such that the particles come out a uniform size and the system is immune to pressure changes.
Malmstadt and Brutchy collaborated with Malancha Gupta of USC Viterbi and USC graduate students Carson Riche and Emily Roberts.
More information: Carson T. Riche et al. Flow invariant droplet formation for stable parallel microreactors, Nature Communications (2016). DOI: 10.1038/ncomms10780
26 Feb 2016
Just as the single-crystal silicon wafer forever changed the nature of communication 60 years ago, a group of Cornell researchers is hoping its work with quantum dot solids – crystals made out of crystals – can help usher in a new era in electronics.
The team, led by Tobias Hanrath, associate professor in the Robert Frederick Smith School of Chemical and Biomolecular Engineering, and graduate student Kevin Whitham, has fashioned two-dimensional superstructures out of single-crystal building blocks. Through a pair of chemical processes, the lead-selenium nanocrystals are synthesized into larger crystals, then fused together to form atomically coherent square superlattices.
The difference between these and previous crystalline structures is the atomic coherence of each 5-nanometer crystal (a nanometer is one-billionth of a meter). They’re not connected by a substance between each crystal – they’re connected to each other. The electrical properties of these superstructures potentially are superior to existing semiconductor nanocrystals, with anticipated applications in energy absorption and light emission.
“As far as level of perfection, in terms of making the building blocks and connecting them into these superstructures, that is probably as far as you can push it,” Hanrath said, referring to the atomic-scale precision of the process.
Associate professor Tobias Hanrath explains his group’s work on assembling quantum dots into ordered, two-dimensional superlattices, the subject of a paper published Feb. 22 in Nature Materials. The work has potential applications in optoelectronics. Credit: Cornell University
The Hanrath group’s paper, “Charge transport and localization in atomically coherent quantum dot solids,” is published in this month’s issue of Nature Materials.
This latest work has grown out of previous published research by the Hanrath group, including a 2013 paper published in Nano Letters that reported a new approach to connecting quantum dots through controlled displacement of a connector molecule, called a ligand. That paper referred to “connecting the dots” – i.e. electronically coupling each quantum dot – as being one of the most persistent hurdles to be overcome.
That barrier seems to have been cleared with this new research. The strong coupling of the nanocrystals leads to formation of energy bands that can be manipulated based on the crystals’ makeup, and could be the first step toward discovering and developing other artificial materials with controllable electronic structure.
Still, Whitham said, more work must be done to bring the group’s work from the lab to society. The structure of the Hanrath group’s superlattice, while superior to ligand-connected nanocrystal solids, still has multiple sources of disorder due to the fact that all nanocrystals are not identical. This creates defects, which limit electron wave function.
“I see this paper as sort of a challenge for other researchers to take this to another level,” Whitham said. “This is as far as we know how to push it now, but if someone were to come up with some technology, some chemistry, to provide another leap forward, this is sort of challenging other people to say, ‘How can we do this better?'”
Hanrath said the discovery can be viewed in one of two ways, depending on whether you see the glass as half empty or half full.
“It’s the equivalent of saying, ‘Now we’ve made a really large single-crystal wafer of silicon, and you can do good things with it,'” he said, referencing the game-changing communications discovery of the 1950s. “That’s the good part, but the potentially bad part of it is, we now have a better understanding that if you wanted to improve on our results, those challenges are going to be really, really difficult.”
Explore further: Nanocrystal infrared LEDs can be made cheaply
More information: Kevin Whitham et al. Charge transport and localization in atomically coherent quantum dot solids, Nature Materials (2016). DOI: 10.1038/nmat4576
19 Feb 2016
The gold sensor is the latest in a series of metal-detecting biosensors under development by Rebecca Lai, an associate professor of chemistry at the University of Nebraska-Lincoln. Other sensors at various stages of development detect mercury, silver or platinum. Similar technology could be used to find cadmium, lead, arsenic, or other metals and metalloids.
A primary purpose for the sensors would be to detect water contaminants, Lai said. She cited the August 2015 blowout of a gold mine near Silverton, Colorado, which spilled chemicals into nearby rivers, as well as the ongoing problems with lead-tainted water supplies in Flint, Michigan.
The photo shows the gold biosensor developed by Rebecca Lai, associate professor of chemistry at the University of Nebraska-Lincoln. The center diagram illustrates how gold ions connect two strands of adenine and hinder electron transmission. The right diagram shows the effect on current signaling the presence of gold. Source: Rebecca Lai/University of Nebraska-Lincoln
Fabricated on paper strips about the size of a litmus strip, Lai’s sensors are designed to be inexpensive, portable and reusable. Instead of sending water samples away for time-consuming tests, people might someday use the biosensors to routinely monitor household water supplies for lead, mercury, arsenic or other dangerous contaminants.
But Lai also is among scientists searching for new and better ways to find gold. Not only aesthetically appealing and financially valuable, the precious metal is in growing demand for pharmaceutical and scientific purposes, including anti-cancer agents and drugs fighting tuberculosis and rheumatoid arthritis.
“Geochemical exploration for gold is becoming increasingly important to the mining industry,” Lai said. “There is a need for developing sensitive, selective and cost-effective analytical methods capable of identifying and quantifying gold in complex biological and environmental samples.”
Scientists have employed several strategies to find gold, such as fluorescence-based sensors, nanomaterials and even a whole cell biosensor that uses transgenic E. coli. Lai was a co-author of a 2013 study that explored the use of E. coli as a gold biosensor.
DNA, the carrier of genetic information in nearly all living organisms, might seem an unlikely method to detect gold and other metals. Lai’s research, however, exploits long-observed interactions between metal ions and the four basic building blocks of DNA: adenine, cytosine, guanine and thymine.
Different metal ions have affinities with the different DNA bases. The gold sensor, for example, is based on gold ions’ interactions with adenine. A mercury sensor is based upon mercury ions’ interaction with thymine. A silver sensor would be based upon silver ions’ interaction with cytosine.
NUtech Ventures, UNL’s affiliate for technology commercialization, is pursuing patent protection and seeking licensing partners for Lai’s metal ion sensors. She applied for a patent for the sensors in 2014.
“Although these interactions have been well-studied, they have not been exploited for use in electrochemical metal ion sensing,” Lai and doctoral student Yao Wu said in a recent Analytical Chemistry article describing the gold sensor.
Lai and Wu say their article is the first report of how oligoadenines — short adenine chains — can be used in the design and fabrication of this class of electrochemical biosensors, which would be able to measure concentrations of a target metal in a water sample as well as its presence.
The DNA-based sensor detects Au(III), a gold ion that originates from the dissolution of metallic gold. The mercury and silver sensors also detect dissolved mercury and silver ions.
“The detected Au(III) has to come from metallic gold, so if gold is found in a water supply, a gold deposit is somewhere nearby,” Lai explained.
The DNA-based biosensors need more refinement before they can be made commercially available, she said.
Lai’s sensor works by measuring electric current passing from an electrode to a tracer molecule, methylene blue in this case. In the absence of Au(III), the observed current is high because the oligoadenine probes are highly flexible and the electron transfer between the electrode and the tracer molecule is efficient.
But upon binding to Au(III) in the sample, the flexibility of the oligoadenine DNA probes is hindered, resulting in a large reduction in the current from the tracer molecule. The extent of the change in current is used to determine the concentration of AU(III) in the sample.
To allow the sensor to be reused multiple times, the Au(III) is later removed from the sensor with an application of another ligand.
Lai’s research focus is on electrochemical ion sensors. Her research has been supported with grants from the National Institutes of Health and the National Science Foundation.
Source: Univ. of Nebraska – Lincoln
Graphene is a single-atomic carbon sheet with a hexagonal honeycomb network. Electrons in graphene take a special electronic state called Dirac-cone where they behave as if they have no mass. This allows them to flow at very high speed, giving graphene a very high level of electrical conductivity.
This is significant because electrons with no mass flowing with no resistance in graphene could lead to the realization of an ultimately high-speed nano electronic device.
The collaborative team of Tohoku University and the University of Tokyo has developed a method to grow high-quality graphene on a silicon carbide (SiC) crystal by controlling the number of graphene sheets. The team fabricated bilayer graphene with this method and then inserted calcium (Ca) atoms between the two graphene layers like a sandwich.
They measured the electrical conductivity with the micro four-point probe method and found that the electrical resistivity rapidly drops at around 4 K (-269 °C), indicative of an emergence of superconductivity.
The team also found that neither genuine bilayer graphene nor lithium-intercalated bilayer graphene shows superconductivity, indicating that the superconductivity is driven by the electron transfer from Ca atoms to graphene sheets.
The success in fabricating superconducting graphene is expected to greatly impact both the basic and applied researches of graphene.
It is currently not clear what phenomenon takes place when the Dirac electrons with no mass become superconductive with no resistance. But based on the latest study results, further experimental and theoretical investigations would help to unravel the properties of superconducting graphene.
The superconducting transition temperature (Tc) observed in this study on Ca-intercalated bilayer graphene is still low (4 K). This prompts further studies into ways to increase Tc, for example, by replacing Ca with other metals and alloys, or changing the number of graphene sheets.
From the application point of view, the latest results pave the way for the further development of ultrahigh-speed superconducting nano devices such as a quantum computing device, which utilizes superconducting graphene in its integrated circuit.
- Satoru Ichinokura, Katsuaki Sugawara, Akari Takayama, Takashi Takahashi, Shuji Hasegawa. Superconducting Calcium-Intercalated Bilayer Graphene. ACS Nano, 2016; DOI: 10.1021/acsnano.5b07848
16 Feb 2016
University of Utah engineers have discovered a new kind of 2D semiconducting material for electronics that opens the door for much speedier computers and smartphones that also consume a lot less power.
The semiconductor, made of the elements tin and oxygen, or tin monoxide (SnO), is a layer of 2D material only one atom thick, allowing electrical charges to move through it much faster than conventional 3D materials such as silicon. This material could be used in transistors, the lifeblood of all electronic devices such as computer processors and graphics processors in desktop computers and mobile devices. The material was discovered by a team led by University of Utah materials science and engineering associate professor Ashutosh Tiwari.
A paper describing the research was published online Monday, Feb. 15, 2016 in the journal, Advanced Electronic Materials. The paper, which also will be the cover story on the printed version of the journal, was co-authored by University of Utah materials science and engineering doctoral students K. J. Saji and Kun Tian, and Michael Snure of the Wright-Patterson Air Force Research Lab near Dayton, Ohio.
Transistors and other components used in electronic devices are currently made of 3D materials such as silicon and consist of multiple layers on a glass substrate. But the downside to 3D materials is that electrons bounce around inside the layers in all directions.
The benefit of 2D materials, which is an exciting new research field that has opened up only about five years ago, is that the material is made of one layer the thickness of just one or two atoms. Consequently, the electrons “can only move in one layer so it’s much faster,” says Tiwari.
While researchers in this field have recently discovered new types of 2D material such as graphene, molybdenun disulfide and borophene, they have been materials that only allow the movement of N-type, or negative, electrons. In order to create an electronic device, however, you need semiconductor material that allows the movement of both negative electrons and positive charges known as “holes.” The tin monoxide material discovered by Tiwari and his team is the first stable P-type 2D semiconductor material ever in existence.
Now that Tiwari and his team have discovered this new 2D material, it can lead to the manufacturing of transistors that are even smaller and faster than those in use today. A computer processor is comprised of billions of transistors, and the more transistors packed into a single chip, the more powerful the processor can become.
Transistors made with Tiwari’s semiconducting material could lead to computers and smartphones that are more than 100 times faster than regular devices. And because the electrons move through one layer instead of bouncing around in a 3D material, there will be less friction, meaning the processors will not get as hot as normal computer chips. They also will require much less power to run, a boon for mobile electronics that have to run on battery power. Tiwari says this could be especially important for medical devices such as electronic implants that will run longer on a single battery charge.
“The field is very hot right now, and people are very interested in it,” Tiwari says. “So in two or three years we should see at least some prototype device.”
Explore further: Semiconductor miniaturisation with 2D nanolattices
11 Feb 2016
Researchers have demonstrated that transparent ink containing gold, silver, and magnetic nanoparticles can be easily screen-printed onto various types of paper, with the nanoparticles being so small that they seep into the paper’s pores. Although invisible to the naked eye, the nanoparticles can be detected by the unique ways that they scatter light and by their magnetic properties. Since the combination of optical and magnetic signatures is extremely difficult to replicate, the nanoparticles have the potential to be an ideal anti-counterfeiting technology.
The researchers, Carlos Campos-Cuerva, Maciej Zieba, and coauthors at the University of Zaragoza in Zaragoza, Spain, and CIBER-BBN in Madrid, Spain, have published a paper on the anti-counterfeiting nanoparticle ink in a recent issue of Nanotechnology.
“We believe that it would be interesting to sell to different manufacturers their own personalized ink providing a specific combination of signals,” coauthor Manuel Arruebo at the University of Zaragoza and CIBER-BBN told Phys.org. “The nanoparticle-containing ink could then be used to mark a wide variety of supports including paper (documents, labels of wine, or drug packaging), plastic (bank or identity cards), textiles (luxury clothing or bags), and so on.”
Whereas previous methods of using nanoparticles as an anti-counterfeiting measure often require expensive, sophisticated equipment, the new technique is much simpler. The researchers attached the nanoparticles to the paper by standard screen-printing of transparent ink, and then authenticated the samples using commercially available optical and magnetic sensors.
“We demonstrated that the combination of nanomaterials providing different optical and magnetic properties on the same printed support is possible, and the resulting combined signals can be used to obtain a user-configurable label, providing a high degree of security in anti-counterfeiting applications using simple commercially available sensors at a low cost,” Arruebo said.
Although the nanoparticle ink is easy for the researchers to fabricate, attempting to replicate these authentication signals would be extremely difficult for a forger because the signals arise from the highly specific physical and chemical characteristics of the nanoparticles. Replicating the exact type, size, shape, and surface coating requires highly precise fabrication methods and an understanding of the correlation between the signals and these characteristics.
Making replication even more complicated is the fact that the combined optical and magnetic nanoparticles are printed on top of each other in the same spot, and this overlap creates an even more complex signal. Another advantage of the new technique is that the nanoparticles are able to withstand extreme temperatures and humidity under accelerated weathering conditions.
One of the greatest applications of the technology may be to prevent forgery of pharmaceutical drugs. Counterfeit medicine—which includes drugs that have incorrect or no active ingredients, as well as drugs that are intentionally mislabeled—is a growing problem throughout the world. The researchers plan to pursue such applications as well as further increase the security of the technology in future work.
“We plan to add more physical signals to the same tag by combining nanoparticles which could provide optical, magnetic, and electrical signals, etc., on the same printed spot,” Arruebo said.
More information: Carlos Campos-Cuerva, et al. “Screen-printed nanoparticles as anti-counterfeiting tags.” Nanotechnology. DOI: 10.1088/0957-4484/27/9/095702
Genesis Nanotechnology, Inc. ~ “Great Things from Small Things”
11 Feb 2016
Rechargeable lithium metal batteries have been known for four decades to offer energy storage capabilities far superior to today’s workhorse lithium-ion technology that powers our smartphones and laptops. But these batteries are not in common use today because, when recharged, they spontaneously grow treelike bumps called dendrites on the surface of the negative electrode.
Over many hours of operation, these dendrites grow to span the space between the negative and positive electrode, causing short-circuiting and a potential safety hazard.
Current technology focuses on managing these dendrites by putting up a mechanically strong barrier, normally a ceramic separator, between the negative and the positive electrodes to restrict the movement of the dendrite. The relative non-conductivity and brittleness of such barriers, however, means the battery must be operated at high temperature and are prone to failure when the barrier cracks.
But a Cornell team, led by chemical and biomolecular engineering professor Lynden Archer and graduate student Snehashis Choudhury, proposed in a recent study that by designing nanostructured membranes with pore dimensions below a critical value, it is possible to stop growth of dendrites in lithium batteries at room temperature.
“The problem with ceramics is that this brute-force solution compromises conductivity,” said Archer, the William C. Hooey Director and James A. Friend Family Distinguished Professor of Engineering and director of the Robert Frederick Smith School of Chemical and Biomolecular Engineering.
“This means that batteries that use ceramics must be operated at very high temperatures — 300 to 400 degrees Celsius [572 to 752 degrees Fahrenheit], in some cases,” Archer said. “And the obvious challenge that brings is, how do I put that in my iPhone?”
You don’t, of course, but with the technology that the Archer group has put forth, creating a highly efficient lithium metal battery for a cellphone or other device could be reality in the not-too-distant future.
Archer credits Choudhury with identifying the polymer polyethylene oxide as particularly promising. The idea was to take advantage of “hairy” nanoparticles, created by grafting polyethylene oxide onto silica to form nanoscale organic hybrid materials (NOHMs), materials Archer and his colleagues have been studying for several years, to create nanoporous membranes.
To screen out dendrites, the nanoparticle-tethered PEO is cross-linked with another polymer, polypropylene oxide, to yield mechanically robust membranes that are easily infiltrated with liquid electrolytes. This produces structures with good conductivity at room temperature while still preventing dendrite growth.
“Instead of a ‘wall’ to block the dendrites’ proliferation, the membranes provided a porous media through which the ions pass, with the pore-gaps being small enough to restrict dendrite penetration,” Choudhury said. “With this nanostructured electrolyte, we have created materials with good mechanical strength and good ionic conductivity at room temperature.”
Archer’s group plotted the performance of its crosslinked nanoparticles against other materials from previously published work and determined “with this membrane design, we are able to suppress dendrite growth more efficiently that anything else in the field. That’s a major accomplishment,” Archer said.
One of the best things about this discovery, Archer said, is that it’s a “drop-in solution,” meaning battery technology wouldn’t have to be radically altered to incorporate it.
“The membrane can be incorporated with batteries in a variety of form factors, since it’s like a paint — and we can paint the surface of electrodes of any shape,” Choudhury added.
This solution also opens the door for other applications, Archer said.
“The structures that Snehashis has created can be as effective with batteries based on other metals, such as sodium and aluminum, that are more earth-abundant and less expensive than lithium and also limited by dendrites,” Archer said.
The group’s paper, “A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles,” was published Dec. 4 in Nature Communications. All four group members, including doctoral students Rahul Mangal and Akanksha Agrawal, contributed to the paper.
The Archer group’s work was supported by the National Science Foundation’s Division of Materials Research and by a grant from the King Abdullah University of Science and Technology in Saudi Arabia. The research made use of the Cornell High Energy Synchrotron Source, which also is supported by the NSF.
- Snehashis Choudhury, Rahul Mangal, Akanksha Agrawal, Lynden A. Archer. A highly reversible room-temperature lithium metal battery based on crosslinked hairy nanoparticles. Nature Communications, 2015; 6: 10101 DOI: 10.1038/ncomms10101
Lithium Battery Catalyst Found to Harm Key Soil Microorganism
University of Wisconsin-Madison
The material at the heart of the lithium ion batteries that power electric vehicles, laptop computers and smartphones has been shown to impair a key soil bacterium, according to new research published online in the journal Chemistry of Materials.
The study by researchers at the University of Wisconsin-Madison and the University of Minnesota is an early signal that the growing use of the new nanoscale materials used in the rechargeable batteries that power portable electronics and electric and hybrid vehicles may have untold environmental consequences.
Researchers led by UW-Madison chemistry Professor Robert J. Hamers explored the effects of the compound nickel manganese cobalt oxide (NMC), an emerging material manufactured in the form of nanoparticles that is being rapidly incorporated into lithium ion battery technology, on the common soil and sediment bacterium Shewanella oneidensis.
“As far as we know, this is the first study that’s looked at the environmental impact of these materials,” says Hamers, who collaborated with the laboratories of University of Minnesota chemist Christy Haynes and UW-Madison soil scientist Joel Pedersen to perform the new work.
NMC and other mixed metal oxides manufactured at the nanoscale are poised to become the dominant materials used to store energy for portable electronics and electric vehicles. The materials, notes Hamers, are cheap and effective.
“Nickel is dirt cheap. It’s pretty good at energy storage. It is also toxic. So is cobalt,” Hamers says of the components of the metal compound that, when made in the form of nanoparticles, becomes an efficient cathode material in a battery, and one that recharges much more efficiently than a conventional battery due to its nanoscale properties.
Hamers, Haynes and Pedersen tested the effects of NMC on a hardy soil bacterium known for its ability to convert metal ions to nutrients. Ubiquitous in the environment and found worldwide, Shewanella oneidensis, says Haynes, is “particularly relevant for studies of potentially metal-releasing engineered nanomaterials. You can imagine Shewanella both as a toxicity indicator species and as a potential bioremediator.”
Subjected to the particles released by degrading NMC, the bacterium exhibited inhibited growth and respiration. “At the nanoscale, NMC dissolves incongruently,” says Haynes, releasing more nickel and cobalt than manganese. “We want to dig into this further and figure out how these ions impact bacterial gene expression, but that work is still underway.”
Haynes adds that “it is not reasonable to generalize the results from one bacterial strain to an entire ecosystem, but this may be the first ‘red flag’ that leads us to consider this more broadly.”
The group, which conducted the study under the auspices of the National Science Foundation-funded Center for Sustainable Nanotechnology at UW-Madison, also plans to study the effects of NMC on higher organisms.
According to Hamers, the big challenge will be keeping old lithium ion batteries out of landfills, where they will ultimately break down and may release their constituent materials into the environment.
“There is a really good national infrastructure for recycling lead batteries,” he says. “However, as we move toward these cheaper materials there is no longer a strong economic force for recycling. But even if the economic drivers are such that you can use these new engineered materials, the idea is to keep them out of the landfills. There is going to be 75 to 80 pounds of these mixed metal oxides in the cathodes of an electric vehicle.”
Hamers argues that there are ways for industry to minimize the potential environmental effects of useful materials such as coatings, “the M&M strategy,” but the ultimate goal is to design new environmentally benign materials that are just as technologically effective.
- Mimi N. Hang, Ian L. Gunsolus, Hunter Wayland, Eric S Melby, Arielle C. Mensch, Katie R Hurley, Joel A. Pedersen, Christy L. Haynes, Robert J Hamers. Impact of Nanoscale Lithium Nickel Manganese Cobalt Oxide (NMC) on the Bacterium Shewanella oneidensis MR-1. Chemistry of Materials, 2016; DOI: 10.1021/acs.chemmater.5b04505
Genesis Nanotechnology, Inc. ~ “Great Things from Small Things”
Note to Readers: A lot of you have Commented or E-mailed with a common question about this article, “Who is the new start-up company?” (developing the anti-counterfeiting technology based on Quantum Dots). For more information about the Company, its History, Founders and Technologies visit: Quantum Materials Corporation: Symbol: QTMM
BTW … In a recent press release they just released: “Quantum Materials Corp to launch Quantum Dot Production in China with Joint Venture Partner GTG, who has committed $20 Million US in investment.”
Cheers! Team GNT
Even with all the promise offered by additive manufacturing (AM), some people are still wary of the potential pitfalls exposed by the technology. Leaving the notion of 3D printed guns, hearts and electronics aside, there are very real concerns about how intellectual property (IP) will fare in a digital manufacturing world, or how any single company can protect sales of 3D printed objects. Piracy is often seen as only a 3D scanner and printer away.
A new start-up Nano-materials company may have the solution to some of these concerns. The company is in the business of manufacturing, among other things, quantum dots. These tiny structures are constructed from semiconductor Nano-materials, and can be embedded within 3D printed objects. A partnership with the Institute for Critical Technology and Applied Science and the Design, Research, and Education for Additive Manufacturing Systems (DREAMS) Laboratory at Virginia Tech has resulted in a method of using quantum dots to act as a sort of fingerprint for objects built using AM.
“The remarkable number of variations of semiconductor Nano-materials properties that can be manufactured, coupled with Virginia Tech’s anti-counterfeiting process design, combine to offer corporations extreme flexibility in designing physical cryptography systems to thwart counterfeiters. As 3D printing and additive manufacturing technology advances, its ubiquity allows for the easy pirating of protected designs.” (VP for research and development)
The quantum dots work to foil counterfeiters by creating a unique signature for each item that is only known to the company producing that item. This will allow for rapid recognition of counterfeit items without requiring destructive testing methods.
Additionally, the company offers a number of semiconductor Nano-materials that further increase security. If you are familiar with computing, the addition of unique materials improves security strength in a similar way as moving from 128-bit to 256-bit encryption, according to the company.
With the recent boom in medical AM, both for rapid prototyping and end-use, this type of security can offer companies some assurance that they’ll see a return on investment for all the hard work put in to designing new devices. The use of quantum dots should also reassure other manufacturers who are on the fence about the use of AM that their patents will be upheld by more than a piece of paper and a handshake.
05 Feb 2016
The specter of counterfeit products is always a concern for any company that relies on other facilities to actually manufacture and assemble their products. From fake Rolex watches to fake iPhones to fake Louis Vuitton purses, large companies often spend millions to protect their intellectual property from criminals who copy and sell fake products to often unsuspecting consumers.
While it can be easy to be anti-corporate and turn a blind eye to this kind of theft, especially when the companies are large and extremely profitable, their concern goes far beyond the potential loss of profits. The fact is, most counterfeit products are vastly inferior to the real thing, and if a consumer doesn’t know that they are purchasing a fake then the company not only has a lost sale, but their reputation will take a hit based on something that they didn’t even produce.
Even as 3D printing continues to grow into a valid and profitable alternative manufacturing method to injection molding or large-scale mass production, there are still companies that see the threat of counterfeiting as a reason to stall the adoption of 3D printing technology. Realistically there is not much that can be done about pirated 3D models and individuals using home 3D printers to make fake products. Combating individual piracy has been woefully ineffective for the entertainment industry, and probably only encouraged more users to download electronic files illegally. It stands to reason that going after individual pirates will work just as well if the 3D printing industry makes an attempt to over-regulate and control the flow of 3D printable files.
Many of the solutions that are being floated as counter-counterfeiting measures don’t really seem especially feasible or sustainable. Adding DRM (digital rights management) or unlock code requirements to 3D files may slow down some users, but just as with DRM efforts on movies and video games, if someone can put a lock on something, someone can take that same lock off and teach others how to do it as well. These efforts may work in the short term, as the pool of users who are capable of breaking DRM on 3D printable files is smaller, and there isn’t really an outlet to disperse those illegal files yet. But as the industry grows it is going to be harder and harder for companies to control their intellectual property using these methods. I’m not really sure that there is much to be done on this end of the industry. Besides, there is an even greater counterfeiting problem brewing on the manufacturing side of the industry and it is far more important than individual piracy ever could be.
As with fake mass-produced consumer goods, mass-produced industrial parts are also counterfeited quite frequently. It may be more interesting to talk about fake purses, but a greater threat is products like fake screws, bolts, fittings and individual components. Many of the parts that are used to build our homes, businesses, vehicles and personal electronics use mass-produced components that manufacturers simply purchase in extremely large quantities. And all of those parts are held to very strict manufacturing guidelines that dictate how they can be used, what their maximum stress tolerances are and how they can be expected to perform.
When these types of components are forged, they are rarely made with the same quality of materials and often don’t even come close to performing as required. If these fake parts find their way unknowingly into the hands of manufacturers, who design products with these components’ manufacturing guidelines in mind, then the results could be catastrophic. There have been instances of airplanes and automobiles that have crashed due to the failure of lower quality, counterfeit parts. Buildings and homes are also at risk due to poor quality and counterfeited construction materials being used. It may seem odd, but cheaply made products that do not pass strict regulations are a huge business and lives can be lost to it.
With 3D printed components becoming more common, and eventually expected to be extremely common, counterfeit parts will pose a real risk. Using DRM, even if it was effective on a small scale, to prevent machines from making unauthorized parts is not going to matter when these parts can simply be 3D scanned and reproduced without the need for the original 3D model. The methods that need to be developed to combat this type of industrial counterfeiting will need to work in ways that DRM never will and identify the specific physical object as authentic. There are a few different methods that are currently being proposed, with varying probabilities of success.
The most likely option will be including RFID tags on 3D printed components that will identify an object as the real thing. The idea is that any part that doesn’t have an embedded RFID device in it — and they can easily be made small enough to easily be inserted inside of a 3D printed part — will automatically be identified as fake. The downside of this method is price, as the RFID tags themselves would be costly, as would the labor involved in inserting them. Testing for tags will also require specialized equipment that adds more cost to the authentication process. It is possible that a 3D printable material that would act as a tag called InfraStructs could be developed, but that would mean developing multiple materials that will be RFID reactive, which will be quite costly on the development side.
Another authentication option would be chemically tagging materials that can be detected with a handheld spectrometer. There are multiple companies providing these types of materials, but the most promising is a technique developed by InfraTrac. The Maryland-based company has developed a chemical that can be discreetly added to virtually anything without altering the chemical makeup of the material. For instance, parts can be 3D printed with a small subsurface “fingerprint” hidden in a discrete location. That mark alone would be printed with the material that has been treated with the chemical, and would easily identify the part as genuine. The material could also be printed as a single layer of the print with no mark, and no risk of altering the integrity of the part. Of course again this comes with it the need for specialized equipment in the form of the spectrometer and an actual machine that can 3D print with the standard material and the second, tagged material.
3D Printed Model of a Human Heart
One thing is very clear, there is a desire for additive manufacturing to be developed as an alternative to other mass production methods. That means the companies looking to use 3D printing to manufacture parts, and the 3D printing industry itself, are going to need to address the problem sooner rather than later. Determining which of these options is the ideal solution will not be an easy choice, as they both bring with them additional costs and challenges, but doing nothing simply isn’t an option.
Genesis Nanotechnology, Inc. ~ “Great Things from Small Things”