Nanoparticle Ink could Combat Counterfeiting


anticounterf ink 021116Researchers 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 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 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.

anticounterfeiting nanoparticles
An SEM micrograph of paper printed with nanoparticle-based ink, with the nanoparticles circled in red. Credit: Campos-Cuerva, et al. ©2016 IOP Publishing

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 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 which could provide optical, magnetic, and electrical signals, etc., on the same printed spot,” Arruebo said.

Explore further: Upconverting nanoparticle inks: Invisible QR codes tackle counterfeit bank notes

More information: Carlos Campos-Cuerva, et al. “Screen-printed nanoparticles as anti-counterfeiting tags.” Nanotechnology. DOI: 10.1088/0957-4484/27/9/095702

 

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Nanoparticle reduces targeted cancer drug’s toxicity


Cancer Nanoparticle Targets 160210165715_1_540x360In one of the first efforts to date to apply nanotechnology to targeted cancer therapeutics, researchers have created a nanoparticle formulation of a cancer drug that is both effective and nontoxic — qualities harder to achieve with the free drug. Their nanoparticle creation releases the potent but toxic targeted cancer drug directly to tumors, while sparing healthy tissue.

The findings in rodents with human tumors have helped launch clinical trials of the nanoparticle-encapsulated version of the drug, which are currently underway. Aurora kinase inhibitors are molecularly targeted agents that disrupt cancer’s cell cycle.

While effective, the inhibitors have proven highly toxic to patients and have stalled in late-stage trials. Development of several other targeted cancer drugs has been abandoned because of unacceptable toxicity. To improve drug safety and efficacy, Susan Ashton and colleagues designed polymeric nanoparticles called Accurins to deliver an Aurora kinase B inhibitor currently in clinical trials.

The nanoparticle formulation used ion pairing to efficiently encapsulate and control the release of the drug. In colorectal tumor-bearing rats and mice with diffuse large B cell lymphoma, the nanoparticles accumulated specifically in tumors, where they slowly released the drug to cancer cells. Compared to the free drug, the nanoparticle-encapsulated inhibitor blocked tumor growth more effectively at one half the drug dose and caused fewer side effects in the rodents.

Cancer Nanoparticle Targets 160210165715_1_540x360

The polymeric nanoparticle Accurin encapsulates the clinical candidate AZD2811, an Aurora B kinase inhibitor. This material relates to a paper that appeared in the Feb. 10, 2016 issue of Science Translational Medicine, published by AAAS. The paper, by S. Ashton at institution in location, and colleagues was titled, “Aurora kinase inhibitor nanoparticles target tumors with favorable therapeutic index in vivo.”
Credit: Ashton et al., Science Translational Medicine (2016)

A related Focus by David Bearss offers more insights on how Accurin nanoparticles may help enhance the safety and antitumor activity of Aurora kinase inhibitors and other molecularly targeted drugs.


Story Source:

The above post is reprinted from materials provided by American Association for the Advancement of Science. Note: Materials may be edited for content and length.


Journal Reference:

  1. Susan Ashton, Young Ho Song, Jim Nolan, Elaine Cadogan, Jim Murray, Rajesh Odedra, John Foster, Peter A. Hall, Susan Low, Paula Taylor, Rebecca Ellston, Urszula M. Polanska, Joanne Wilson, Colin Howes, Aaron Smith, Richard J. A. Goodwin, John G. Swales, Nicole Strittmatter, Zoltán Takáts, Anna Nilsson, Per Andren, Dawn Trueman, Mike Walker, Corinne L. Reimer, Greg Troiano, Donald Parsons, David De Witt, Marianne Ashford, Jeff Hrkach, Stephen Zale, Philip J. Jewsbury, and Simon T. Barry. Aurora kinase inhibitor nanoparticles target tumors with favorable therapeutic index in vivo. Science Translational Medicine, 2016 DOI: 10.1126/scitranslmed.aad2355

Room – Temp Lithium Metal Battery may be close to Reality … and with it “A Cautionary Tale” for the Environment


Lithium Batt Metal 23d9926Rechargeable 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.


Story Source:

The above post is reprinted from materials provided by Cornell University. Note: Materials may be edited for content and length.


Journal Reference:

  1. 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 Batt Micro Org 160204151102_1_540x360Lithium 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.

Lithium Batt Micro Org 160204151102_1_540x360

Shewanella oneidensis is a ubiquitous, globally distributed soil bacterium. In nature, the microbe thrives on metal ions, converting them to metals like iron that serve as nutrients for other microbes. The bacterium was shown to be harmed by the compound nickel manganese cobalt oxide, which is produced in nanoparticle form and is the material poised to become the dominant material in the lithium ion batteries that will power portable electronics and electric vehicles.
Credit: Illustration by Marushchenko/University of Minnesota

“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.


Story Source:

The above post is reprinted from materials provided by University of Wisconsin-Madison. The original item was written by Terry Devitt. Note: Materials may be edited for content and length.


Journal Reference:

  1. 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

 

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Quantum Dots of Iron Arranged on Boron Nitride Nanotubes (BNNTs) for Better Wearable Tech Without Semiconductors: “Iron Stepping Stones” with Video


Nanotube Iron QDs image131438-horiz

Iron-dotted boron nitride nanotubes, made in Yoke Khin Yaps’ lab at Michigan Tech, could make for better wearable tech because of their flexibility and electronic behaviors.

February 5, 2016—

The road to more versatile wearable technology is dotted with iron. Specifically, quantum dots of iron arranged on boron nitride nanotubes (BNNTs). The new material is the subject of a studypublished in Scientific Reports in February, led by Yoke Khin Yap, a professor of physics at Michigan Technological University.

Yap says the iron-studded BNNTs are pushing the boundaries of electronics hardware. The transistors modulating electron flow need an upgrade.

“Look beyond semiconductors,” he says, explaining that materials like silicon semiconductors tend to overheat, can only get so small and leak electric current. The key to revamping the fundamental base of transistors is creating a series of stepping-stones.

Quantum Dots

The nanotubes are the mainframe of this new material. BNNTs are great insulators and terrible at conducting electricity. While at first that seems like an odd choice for electronics, the insulating effect of BNNTs is crucial to prevent current leakage and overheating. Additionally, electron flow will only occur across the metal dots on the BNNTs.

In past research, Yap and his team used gold for quantum dots, placed along a BNNT in a tidy line. With enough energy potential, the electrons are repelled by the insulating BNNT and hopscotch from gold dot to gold dot. This electron movement is called quantum tunneling.

“Imagine this as a river, and there’s no bridge; it’s too big to hop over,” Yap says. “Now, picture having stepping stones across the river—you can cross over, but only when you have enough energy to do so.”

Nanotech for Wearable Electronics

Unlike with semiconductors, there is no classical resistance with quantum tunneling. No resistance means no heat. Plus, these materials are very small; the nanomaterials enable the transistors to shrink as well. An added bonus is that BNNTs are also quite flexible, a boon for wearable electronics.

“Here’s where the challenge comes in,” Yap says, holding up a pen to demonstrate. He gestures along the length of the pen, which mimics a straight BNNT, tapping out a line of quantum dots. “We have an array here to do quantum tunneling, but what if we want to bend the array to be flexible like a piece of wearable electronics?”

Yap sets down the pen and curls up his index finger: “And if I bend the dots, the distance between them changes—in doing so, we change the electronic behavior.”

Changing the behavior means that the quantum tunneling may not work. The solution is to get out of line: Yap and his team arranged a grid of quantum dots around the outside of the BNNT.

“This time we used iron instead of gold,” Yap adds, explaining that gold’s melting temperature was low for the process his team used. “And when we tested the material, the electrons distributed uniformly across the whole surface of the nanotubes.”

That means that instead of having a line of stepping stones, there are many different paths across the river, and an electron will jump to the nearest one. For future use in wearable electronics, the multiplicity of paths ensures electricity is moving from one riverbank to the next, one way or another. Using scanning tunneling microscopy inside a transmission electron microscope (STM-TEM), the team successfully bent the iron dot-coated BNNT while monitoring the electron flows. The electronic behaviors remain the same even when the BNNT was bent all the way up to 75 degrees.

Next Steps

Yap says that this experiment is a proof of concept. While the iron BNNT material shows promise, it’s not a full transistor yet, capable of modulating electron movement. Right now, it’s called a flexible tunneling channel.

“Next, we’ll put the BNNT and iron onto a bendable plastic substrate,” Yap says. “Then we’ll bend this substrate and watch where the electrons go.”

This experimental work is complemented by computer simulations by John Jaszczak, professor of physics, and Paul Bergstrom, professor of electrical and computer engineering.

Which route the electricity takes is hard to track, which will be the main challenge for the next experiment. But one direction is certain, Yap’s research is headed down a path to change the basic level of electronics and make wearable tech more adaptable.

Michigan Technological University (www.mtu.edu) is a leading public research university developing new technologies and preparing students to create the future for a prosperous and sustainable world. Michigan Tech offers more than 120 undergraduate and graduate degree programs in engineering; forest resources; computing; technology; business; economics; natural, physical and environmental sciences; arts; humanities; and social sciences.

Quantum Dots Bring Anti-counterfeiting Tech to 3D Printing


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

3D Printed Auto 020516 XMODULE3-1-e1454538456427

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.

 

QD AM Mfg 020516 LEDA company 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.

 

 

 

 

As 3D Printing Comes of Age – How will 3D Printing (Additive Manufacturing or ‘AM’) Combat Counterfeiting Products?


3D Printing I 020516 3d_printing

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.

DRM on 3D printable files is probably not going to be an effective deterrent.

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.

Counterfeit bolts.

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.

3D printed Nike shoes with embedded InfraStructs.

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.

Subsurface fingerprinting with InfraTrac.

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 Printing II Heart 020516 maxresdefault

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.

 

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New Kind of Nanowires Designed For Efficient Water Splitting and Solar Energy Storage


Nanowires 020316 bf8802f7297fd2bfea985c26d0b9a636_w1440.jpg

California is committed to 33 percent energy from renewable resources by 2020. With that deadline fast approaching, researchers across the state are busy exploring options.

Solar energy is attractive but for widespread adoption, it requires transformation into a storable form. This week in ACS Central Science, researchers report that nanowires made from multiple metal oxides could put solar ahead in this race.

One way to harness solar power for broader use is through photoelectrochemical (PEC) water splitting that provides hydrogen for fuel cells. Many materials that can perform the reaction exist, but most of these candidates suffer from issues, ranging from efficiency to stability and cost.

Peidong Yang and colleagues designed a system where nanowires from one of the most commonly used materials (TiO2) acts as a “host” for “guest” nanoparticles from another oxide called BiVO4. BiVO4 is a newly introduced material that is among the best ones for absorbing light and performing the water splitting reaction, but does not carry charge well while TiO2 is stable, cheap and an efficient charge carrier but does not absorb light well.

Together with a unique studded nanowire architecture, the new system works better than either material alone.

The authors state their approach can be used to improve the efficiencies of other photoconversion materials.

Synopsis

We report the use of Ta:TiO2|BiVO4 as a photoanode for use in solar water splitting cells. This host−guest system makes use of the favorable band alignment between the two semiconductors. The nanowire architecture allows for simultaneously high light absorption and carrier collection for efficient solar water oxidation.

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Metal oxides that absorb visible light are attractive for use as photoanodes in photoelectrosynthetic cells. However, their performance is often limited by poor charge carrier transport. We show that this problem can be addressed by using separate materials for light absorption and carrier transport. Here, we report a Ta:TiO2|BiVO4 nanowire photoanode, in which BiVO4 acts as a visible light-absorber and Ta:TiO2 acts as a high surface area electron conductor. Electrochemical and spectroscopic measurements provide experimental evidence for the type II band alignment necessary for favorable electron transfer from BiVO4 to TiO2. The host–guest nanowire architecture presented here allows for simultaneously high light absorption and carrier collection efficiency, with an onset of anodic photocurrent near 0.2 V vs RHE, and a photocurrent density of 2.1 mA/cm2 at 1.23 V vs RHE.

Introduction


Harnessing energy from sunlight is a means of meeting the large global energy demand in a cost-effective and environmentally benign manner. However, to provide constant and stable power on demand, it is necessary to convert sunlight into an energy storage medium.(1) An example of such a method is the production of hydrogen by photoelectrochemical (PEC) water splitting. The direct splitting of water can be achieved using a single semiconductor; however, due to the voltage requirement of the water splitting reaction and the associated kinetic overpotentials, only wide-band-gap materials can perform overall water splitting, limiting the efficiency due to insufficient light absorption.(2) To address this issue, a dual-band-gap z-scheme system can be utilized, with a semiconductor photoanode and photocathode to perform the respective oxidation and reduction reactions.(3) This approach allows for the use of lower-band-gap materials that can absorb complementary portions of the solar spectrum and yield higher solar-to-fuel efficiencies.(4, 5) In this integrated system, the charge flux is matched in both light absorbers of the photoelectrochemical cell. Therefore, the overall performance is determined by the limiting component. In most photoelectrosynthetic cells, this limiting component is the semiconductor photoanode.(6)
Metal oxides have been heavily researched as photoanode materials since few conventional light absorber materials are stable at the highly oxidizing conditions required for water oxidation.(7) However, the most commonly studied binary oxide, TiO2, has a band gap that is too large to absorb sunlight efficiently (∼3.0 eV), consequently limiting its achievable photocurrent.(8) While promising work has recently been done on stabilizing conventional light absorbers such as Si,(9) GaAs,(10) and InP,(11) the photovoltage obtained by these materials thus far has been insufficient to match with smaller-band-gap photocathode materials such as Si and InP in a dual absorber photoelectrosynthetic cell.(12, 13) Additionally, these materials have high production and processing costs. Small-band-gap metal oxides that absorb visible light and can be inexpensively synthesized, such as WO3, Fe2O3, and BiVO4, are alternative materials that hold promise to overcome these limitations.(14-16) Among these metal oxides, BiVO4 has emerged as one of the most promising materials due to its relatively small optical band gap of ∼2.5 eV and its negative conduction band edge (∼0 V versus RHE).(17, 18) Under air mass 1.5 global (AM1.5G) solar illumination, the maximum achievable photocurrent for water oxidation using BiVO4 is ∼7 mA/cm2.(16) However, the water oxidation photocurrent obtained in practice for BiVO4 is substantially lower than this value, mainly due to poor carrier transport properties, with electron diffusion lengths shorter than the film thickness necessary to absorb a substantial fraction of light.(17)
One approach for addressing this problem is to use two separate materials for the tasks of light absorption and carrier transport. To maximize performance, a conductive and high surface area support material (“host”) is used, which is coated with a highly dispersed visible light absorber (“guest”). This architecture allows for efficient use of absorbed photons due to the proximity of the semiconductor liquid junction (SCLJ). This strategy has been employed in dye sensitized (DSSC) and quantum dot sensitized solar cells (QDSSC).(19, 20) Using a host–guest scheme can improve the performance of photoabsorbing materials with poor carrier transport but relies upon appropriate band alignment between the host and guest. Namely, the electron affinity of the host should be larger, to favor electron transfer from guest to host without causing a significant loss in open-circuit voltage.(21) Nanowire arrays provide several advantages for use as the host material as they allow high surface area loading of the guest material, enhanced light scattering for improved absorption, and one-dimensional electron transport to the back electrode.(22) Therefore, nanowire arrays have been used as host materials in DSSCs, QDSSCs, and hybrid perovskite solar cells.(23-25) In photoelectrosynthetic cells, host–guest architectures have been utilized for oxide photoanodes such as Fe2O3|TiSi2,(26) Fe2O3|WO3,(27) Fe2O3|SnO2,(28) and Fe2TiO5|TiO2.(29) For BiVO4, it has been studied primarily with WO3|BiVO4,(30-32) ZnO|BiVO4,(33) and anatase TiO2|BiVO4.(34) While attractive for its electronic transport properties, ZnO is unstable in aqueous environments, and WO3 has the disadvantage of having a relatively positive flatband potential (∼0.4 V vs RHE)(14) resulting in potential energy losses for electrons as they are transferred from BiVO4 to WO3, thereby limiting the photovoltage of the combined system. Performance in the low potential region is critical for obtaining high efficiency in photoelectrosynthetic cells when coupled to typical p-type photocathode materials such as Si or InP.(12, 13) TiO2 is stable in a wide range of pH and has a relatively negative flat band potential (∼0.2 V vs RHE)(7) which does not significantly limit the photovoltage obtainable from BiVO4, while still providing a driving force for electron transfer. While TiO2 has intrinsically low mobility, doping TiO2 with donor type defects could increase the carrier concentration and thus the conductivity. Indeed, niobium and tantalum doped TiO2 have recently been investigated as potential transparent conductive oxide (TCO) materials.(35, 36) A host material with high carrier concentration could also ensure low contact resistance with the guest material.(37)
Using a solid state diffusion approach based on atomic layer deposition (ALD), we have previously demonstrated the ability to controllably and uniformly dope TiO2.(38) In this study we demonstrate a host–guest approach using Ta-doped TiO2 (Ta:TiO2) nanowires as a host and BiVO4 as a guest material. This host–guest nanowire architecture allows for simultaneously high light absorption and carrier collection efficiency, with an onset of anodic photocurrent near 0.2 V vs RHE, and a photocurrent of 2.1 mA/cm2 at 1.23 V vs RHE. We show that the synergistic effect of the host–guest structure results in higher performance than either pure TiO2 or BiVO4. We also experimentally demonstrate thermodynamically favorable band alignment between TiO2 and BiVO4 using spectroscopic and electrochemical methods, and study the band edge electronic structure of the TiO2 and BiVO4 using X-ray absorption and emission spectroscopies.

 

Article adapted from a American Chemical Society news release. To Read the FULL release, please click on the link provided below.

Publication: TiO2/BiVO4 Nanowire Heterostructure Photoanodes Based on Type II Band Alignment. Resasco, J et al. ACS Central Science (3 February, 2016): Click here to view.

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