New “Quasiparticles ” Research Allows Data to be Recorded … with LIGHT!



Russian physicists with their colleagues from Europe through changing the light parameters, learned to generate quasiparticles – excitons, which were fully controllable and also helped to record information at room temperature. 

These particles act as a transitional form between photons and electrons so the researchers believe that with excitons, they will be able to create compact optoelectronic devices for rapid recording and processing an optical signal. The proposed method is based on use of a special class of materials called metal-organic frameworks. The study appeared in Advanced Materials. 

To simplify the description of complex effects in quantum mechanics, scientists have introduced a concept of quasiparticles. One of them which is called exciton is an “electron – hole” pair, which provides energy transfer between photons and electrons. 

According to the scientific community, this mediation of quasiparticles will help to combine optics with electronics to create a fundamentally new class of equipment – more compact and energy efficient. However, all exciton demo devices either operate only at low temperature, or are difficult to manufacture which inhibits their mass adoption.

 

In the new study, the scientists from ITMO University in Saint Petersburg, Leipzig University in Germany and Eindhoven University of Technology in the Netherlands could generate excitons at room temperature by changing the light parameters. 
The authors also managed to control the quasiparticles with ultra-high sensitivity of about hundreds of femtoseconds (10-13 s). Finally, they developed an easy method for data recording with excitons. This all became possible through the use of an individual class of materials called metal-organic frameworks.

 

Metal-organic frameworks (MOF) synthesized at ITMO University, have a layered structure. Between the layers, there is a physical attraction called van der Waals force. To prevent the plates from uncontrollably coming together, the interlayer space is filled with an organic liquid, which fixes the framework to be three-dimensional.

 

In such crystals, the researchers learned to bring two types of excitons individually: intralayer and interlayer. The first arise when a photon absorbed by the crystal turns into an electron-hole pair inside a layer, but the second appear when an electron and a hole belong to neighboring layers. In some time, both kinds of quasiparticles disintegrate, re-radiating the energy as a photon. But excitons can move around the crystal while they exist.

 

The life time of intralayer excitons is relatively short, but their high density and agility allow one to use these quasiparticles to generate light in LEDs and lasers, for instance. Interlayer excitons are more stable, but slow-moving, so the researchers propose them to be used for the data recording. Both types of excitons fit processing of an optical signal, according to the physicists.

 

The innovative approach for information recording concerns the changing a distance between crystal layers to switch “on” and “off” the interlayer excitons. 
Valentin Milichko, the first author of the paper, associate professor of Department of Nanophotonics and Metamaterials at ITMO University, comments: “We locally heated the crystal with a laser. In the place of exposure, the layers stuck together and the luminescence of excitons disappeared while the rest of the crystal continued shining. This could mean that we recorded 1 bit of information, and the record, in the form of a dark spot, was kept for many days. 

To delete the data, it was enough to put the MOF into the same organic liquid that supports layers. In this case, the crystal itself is not affected, but the recorded information (the dark spot) disappears.”

 

The authors believe that in the future the new material will help to bring processing of an optical signal to the usual pattern of zeros and ones: “In fact, we can influence the exciton behavior in the crystal, changing the light intensity. At weak irradiation, excitons are accumulated (in ‘1’ state), but if the laser power increases, the concentration of quasiparticles grows so much that they can instantly disintegrate (in ‘0’ state),” says Valentin Milichko.

 

Typically, excitons occur in dielectric and semiconductor crystals, but the scientists could create these quasiparticles and get control over them in a completely different class of materials, which never was used for this. 
The MOF crystal combines organic components with inorganic that gives it additional properties not available for materials of a single nature. Thus, the organic term allows one to generate excitons at room temperature, but inorganic provides their efficient transfer around the crystal.

 

Valentin A. Milichko, Sergey V. Makarov, Alexey V. Yulin, Alexander V. Vinogradov, Andrei A. Krasilin, Elena Ushakova, Vladimir P. Dzyuba, Evamarie Hey-Hawkins, Evgeny A. Pidko, Pavel A. Belov (2017), Van der Waals metal-organic framework as an excitonic material for advanced photonics, Advanced Materials

*** From Nanotechnology World 

Florida State University Researchers take big step forward in nanotech-based drugs


Nanoparticle drug delivery F3.large

Florida State University Summary:New research takes a step forward in the understanding of nanoparticles and how they can best be used to deliver drugs.

Nanotechnology has become a growing part of medical research in recent years, with scientists feverishly working to see if tiny particles could revolutionize the world of drug delivery.

But many questions remain about how to effectively transport those particles and associated drugs to cells.

In an article published in Scientific Reports, FSU Associate Professor of Biological Science Steven Lenhert takes a step forward in the understanding of nanoparticles and how they can best be used to deliver drugs.

After conducting a series of experiments, Lenhert and his colleagues found that it may be possible to boost the efficacy of medicine entering target cells via a nanoparticle.

“We can enhance how cells take them up and make more drugs more potent,” Lenhert said.

Initially, Lenhert and his colleagues from the University of Toronto and the Karlsruhe Institute of Technology wanted to see what happened when they encapsulated silicon nanoparticles in liposomes — or small spherical sacs of molecules — and delivered them to HeLa cells, a standard cancer cell model.

The initial goal was to test the toxicity of silicon-based nanoparticles and get a better understanding of its biological activity.

Silicon is a non-toxic substance and has well-known optical properties that allow their nanostructures to appear fluorescent under an infrared camera, where tissue would be nearly transparent. Scientists believe it has enormous potential as a delivery agent for drugs as well as in medical imaging.

But there are still questions about how silicon behaves at such a small size.

“Nanoparticles change properties as they get smaller, so scientists want to understand the biological activity,” Lenhert said. “For example, how does shape and size affect toxicity?”

Scientists found that 10 out of 18 types of the particles, ranging from 1.5 nanometers to 6 nanometers, were significantly more toxic than crude mixtures of the material.

At first, scientists believed this could be a setback, but they then discovered the reason for the toxicity levels. The more toxic fragments also had enhanced cellular uptake. That information is more valuable long term, Lenhert said, because it means they could potentially alter nanoparticles to enhance the potency of a given therapeutic.

The work also paves the way for researchers to screen libraries of nanoparticles to see how cells react.

“This is an essential step toward the discovery of novel nanotechnology based therapeutics,” Lenhert said. “There’s big potential here for new therapeutics, but we need to be able to test everything first.”


Story Source:

Materials provided by Florida State University. Original written by Kathleen Haughney. Note: Content may be edited for style and length.


Journal Reference:

  1. Aubrey E. Kusi-Appiah, Melanie L. Mastronardi, Chenxi Qian, Kenneth K. Chen, Lida Ghazanfari, Plengchart Prommapan, Christian Kübel, Geoffrey A. Ozin, Steven Lenhert. Enhanced cellular uptake of size-separated lipophilic silicon nanoparticles. Scientific Reports, 2017; 7: 43731 DOI: 10.1038/srep43731

 

A ‘nano-golf course’ to assemble precisely nanoparticules


nano-golf-course-ananogolfcouTo show how well their method works, the researchers produced geometrically complex structures by writing out the alphabet with nanoparticles — the smallest segment display in the world. Credit: Nature Nanotechnology (2016). DOI: 10.1038/nnano.2016.179

Whether it has to do with making pens or building space shuttles, the manufacturing process consists of creating components and then carefully assembling them. But when it comes to infinitely small structures, manipulating and assembling high-performance nanoparticles on a substrate is no mean feat.

Researchers in EPFL’s Laboratory of Microsystems, which is headed by Jürgen Brugger, have come up with a way to position hundreds of thousands of very precisely on a one centimeter square surface. The nanoparticles were placed within one nanometer – versus 10 to 20 nanometers using conventional methods – and oriented within one degree.

Their work, which was published in Nature Nanotechnology, sets the stage for the development of nanometric devices such as optical detection equipment and biological sensors. “If we manage to place one nanometer apart, we could, for example, confine light to an extraordinary degree and detect or interact with individual molecules,” said Valentin Flauraud, the lead author.

“Playing golf” with nanoparticles

For their study, the researchers used gold nanoparticles that were grown chemically in a liquid. “These nanoparticles exhibit better properties than those produced through evaporation or etching, but it is more difficult to manipulate them, because they are suspended in a liquid,” said Flauraud.

A 'nano-golf course' to assemble precisely nanoparticules
     
A drop full of nanoparticles is dragged across a substrate with nanometric barriers and holes. When the nanoparticles encounter these obstacles, they detach from the liquid and are captured by the holes. Credit: Valentin Flauraud

Their technique consists of taking a drop of liquid full of nanoparticles and heating it so that the nanoparticles cluster in a given spot. This drop is then dragged across a substrate with nanometric barriers and holes.

When the nanoparticles encounter these obstacles, they detach from the liquid and are captured by the holes. “It’s a little like playing miniature golf,” said the researcher. Each trap is designed to orient a nanoparticle in a specific way. “The challenge was to figure out how the liquid, the particles and the substrate interact at the nanometric scale so we could trap the nanoparticles effectively,” said Massimo Mastrangeli, the second author and now a researcher at the Max Planck Institute for Intelligent Systems in Stuttgart.

Writing out the alphabet with nanoparticles

To show how well their method works, the researchers took on several challenges. First, they tested the optical properties of their system with a powerful in EPFL’s Interdisciplinary Center for Electron Microscopy (CIME).

They then showed that their technique could be used to produce geometrically complex structures by writing out the alphabet with nanoparticles – the smallest segment display in the world. “All of this work was conducted at EPFL and is the result of strong synergies between the various technical platforms and the labs,” said Professor Brugger. “It’s an excellent example of how top-down and bottom-up methods can be combined, opening the door to numerous unexplored fields of nanotechnology.”

Explore further: 3-D nanoprinting to turbocharge microscopes

More information: Valentin Flauraud et al, Nanoscale topographical control of capillary assembly of nanoparticles, Nature Nanotechnology (2016). DOI: 10.1038/nnano.2016.179

Sheets like graphene: Tailored chemistry links nanoparticles in stable monolayers


Just like carbon atoms in sheets of graphene, nanoparticles can form stable layers with minimal thicknesses of the diameter of a single nanoparticle. A novel method of linking nanoparticles into such extremally thin films has been developed at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw.

The chemical tailor cuts his coat according to… his nanoparticles. The tailoring successes to date of researchers synthesizing layers of nanoparticles would not be adequate to stage even the most modest of chemical fashion shows. Nanoparticles could be organized into single-particle layer thicknesses – that is, monolayers – but these were not stable structures. It was not possible to link nanoparticles together in a stable manner in monolayers. Until now.

“In recent years, our group at the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw has been working on developing a universal platform for the synthesis of stable monolayers of nanoparticles. Today we have proof that our ‘tailored’ method of chemically bonding nanoparticles in monolayers actually works,” says Dr. Marcin Fialkowski, professor at IPC PAS, and demonstrates a tiny, shiny layer, deposited on a plate, with the smallest possible thickness – equal to the diameter of a single nanoparticle of gold.

Monolayers of chemically stitched together nanoparticles of gold produced at the IPC PAS have surface areas of the order of square millimetres, and for obvious reasons they are very delicate. Mechanically they resemble acrylic plates: when subjected to forces they initially deform elastically, after which they suddenly crack.

“Our monolayers are not large, because we only wanted to demonstrate the correctness of the concept of their synthesis. Nothing stands in the way of producing monolayers in the way that we propose with areas having many square centimetres,” says Prof. Fialkowski.

Nanoparticle layers have been produced for years at the interface i.e. the thin area (interface) between two immiscible liquids. When introduced into a heavier liquid, upon mechanical agitation, appropriately prepared nanoparticles flow out of it and distribute themselves randomly on the border with the lighter liquid. Order can be brought into the chaos reigning here by compressing the nanoparticles with pistons from the side and thereby compacting them. Monolayers produced in this manner were hitherto not durable and when trying to remove them from the interface they simply fell apart. In turn, structures bound chemically, capable of surviving separation from the interface, upon closer investigation always turned out to be either multi-layers or amorphous composites of nanoparticles.

“Our monolayers are stable because we have linked the nanoparticles with special ‘staples’, or linker-molecules. Each linker joins together two adjacent nanoparticles by strong covalent bonds, that is, chemically”, explains Dr. Tomasz Andryszewski (IPC PAS), lead author of the publication in the journal Chemistry of Materials.

The gold nanoparticles used in experiments at the IPC PAS have diameters of about five nanometres (billionths of a metre); the length of the linkers used is only one and a half. For such a short linker to bind together adjacent nanoparticles, these have to be appropriately shifted towards each other.

“The main difficulty in our work lay in the fact that we had to reconcile two requirements that were in principle opposite. Due to the length of the linker we knew that the nanoparticles should be brought together to be a small distance apart, meaning that they would have to be subjected to relatively large forces. Therefore we didn’t want the nanoparticles to pop out of the interface. At the same time, we had to somehow prevent the nanoparticles from sticking together into random structures”, describes Dr. Andryszewski.

To meet these conditions, the nanoparticles were coated with small, specially designed molecules (ligands), which on one side contained amine groups (with nitrogen and hydrogen), and on the other – thiol groups (with sulphur and hydrogen). The thiol parts combined with the gold, whilst the amino parts located themselves on the outside of the nanoparticles and gave them a positive electric charge.

“The gold nanoparticles modified by us act as buoys with a large displacement: they locate themselves at the boundary between the liquids so durably that even strong agitation is not able to push them out. At the same time they repel each other electrostatically. As a result, each nanoparticle is guaranteed a ‘private space’ around itself, necessary for the preservation of order,” explains PhD student Michalina Iwan (IPC PAS).

When the appropriately prepared nanoparticles had already been squeezed into monolayers at the interface, a linking substance was injected into the system. The crosslinking reaction reminiscent of automatic stapling took place at room temperature and at normal pressure, without the need for any initiators or catalysts. After the chemical anastomosis the monolayer could be removed from the interface between the liquids, dried out, and even subjected to the action of strong solvents.

The physical properties of monolayers derived using tailored chemistry can be modified by selecting appropriate linkers. Longer, polymer linkers would allow the formation of monolayers with a higher elasticity. Using current-conducting linkers it would in turn be possible to produce e.g. monolayers with specifically determined optoelectronic properties. The use of still other linkers could result in monolayers exhibiting a piezoresistive effect, i.e. changing their electrical conductivity under the influence of mechanical deformations. The presented method of synthesis is also important for basic research: in the future, it will enable the direct investigation of, among others, the mechanical properties of single nanoparticles.

The synthetic platform for the production of nanoparticle monolayers was developed and tested at the IPC PAS, and came about under the Foundation for Polish Science TEAM grant.

###

The Institute of Physical Chemistry of the Polish Academy of Sciences was established in 1955 as one of the first chemical institutes of the PAS. The Institute’s scientific profile is strongly related to the newest global trends in the development of physical chemistry and chemical physics. Scientific research is conducted in nine scientific departments. CHEMIPAN R&D Laboratories, operating as part of the Institute, implement, produce and commercialise specialist chemicals to be used, in particular, in agriculture and pharmaceutical industry. The Institute publishes approximately 200 original research papers annually.

Nanoparticles called C dots show ability to induce cell death in tumors


13-nanoparticleCredit: Cornell University

Nanoparticles known as Cornell dots, or C dots, have shown great promise as a therapeutic tool in the detection and treatment of cancer.

Now, the ultrasmall particles – developed more than a dozen years ago by Ulrich Wiesner, the Spencer T. Olin Professor of Engineering – have shown they can do something even better: kill cancer cells without attaching a cytotoxic drug.

A study led by Michelle Bradbury, director of intraoperative imaging at Memorial Sloan Kettering Cancer Center and associate professor of radiology at Weill Cornell Medicine, and Michael Overholtzer, cell biologist at MSKCC, in collaboration with Wiesner has thrown a surprising twist into the decadelong quest to bring C dots out of the lab and into use as a clinical therapy.

Their paper, “Ultrasmall Nanoparticles Induce Ferroptosis of Nutrient-Deprived Cancer Cells and Suppress Tumor Growth,” was published Sept. 26 in Nature Nanotechnology. The work details how C dots, administered in large doses and with the tumors in a state of nutrient deprivation, trigger a type of cell death called ferroptosis.

“If you had to design a nanoparticle for killing cancer, this would be exactly the way you would do it,” Wiesner said. “The particle is well tolerated in normally healthy tissue, but as soon as you have a tumor, and under very specific conditions, these particles become killers.”

“In fact,” Bradbury said, “this is the first time we have shown that the particle has intrinsic therapeutic properties.”

Wiesner’s fluorescent silica particles, as small as 5 nanometers in diameter, were originally designed to be used as diagnostic tools, attaching to cancer cells and lighting up to show a surgeon where the tumor cells are. Potential uses also included drug delivery and environmental sensing. A first-in-human clinical trial by the Food and Drug Administration, led by Bradbury, deemed the particles safe for humans.

In further testing of the particles over the last five years – including the last 13 months as a member of the Centers of Cancer Nanotechnology Excellence, a National Cancer Institute initiative established in August 2015 – Bradbury, Overholtzer, Wiesner and their collaborators made this major, unexpected finding.

When incubated with cancer cells at high doses – and, importantly, with cancer cells in a state of nutrient deprivation – Wiesner’s peptide-coated C dots show the ability to adsorb iron from the environment and deliver this into cancer cells. The peptide, called alpha-MSH, was developed by Thomas Quinn, professor of biochemistry at the University of Missouri.

This process triggers ferroptosis, a necrotic form of cell death involving plasma membrane rupture – different from the typical cell fragmentation found during a more commonly observed form of called apoptosis.

“The original purpose for studying the dots in cells was to see how well larger concentrations would be tolerated without altering cellular function,” Overholtzer said. “While high concentrations were well-tolerated under normal conditions, we wanted to also know how cancer cells under stress might respond.”

To the group’s surprise, in 24 to 48 hours after the were exposed to the dots, there was a “wave of destruction” throughout the entire cell culture, Wiesner said. Tumors also shrank when mice were administered multiple high dose injections without any adverse reactions, said Bradbury, co-director with Wiesner of the MSKCC-Cornell Center for Translation of Cancer Nanomedicines.

In the ongoing fight against a disease that kills millions worldwide annually – cancer has taken several in Wiesner’s family, making this also a personal crusade for him. Having another weapon can only help, Wiesner said.

“We’ve found another tool that people have not thought about at all so far,” he said. “This has changed our way of thinking about nanoparticles and what they could potentially do.”

Future work will focus on utilizing these particles in combination with other standard therapies for a given tumor type, Bradbury said, with the hope of further enhancing efficacy before testing in humans.

Researchers will also look to tailor the particle to target specific cancers. “It’s a matter of designing the particles with different attachments on them, so they’ll bind to the particular cancer we’re after,” Overholtzer said.

Explore further: Camera system aids cancer clinical trial (w/ Video)

More information: Sung Eun Kim et al. Ultrasmall nanoparticles induce ferroptosis in nutrient-deprived cancer cells and suppress tumour growth,Nature Nanotechnology (2016). DOI: 10.1038/nnano.2016.164

 

 

Nanoparticles that Speed Blood Clotting ~ Great Things from Small Things ~ May One Day Save Lives


Blood Clot NPs 082216 10-nanoparticle.jpgNanoparticles (green) help form clots in an injured liver. The researchers added color to the scanning electron microscopy image after it was taken. Credit: Erin Lavik, Ph.D.

Whether severe trauma occurs on the battlefield or the highway, saving lives often comes down to stopping the bleeding as quickly as possible. Many methods for controlling external bleeding exist, but at this point, only surgery can halt blood loss inside the body from injury to internal organs.

Now, researchers have developed nanoparticles that congregate wherever injury occurs in the body to help it form blood clots, and they’ve validated these particles in test tubes and in vivo.

The researchers will present their work today at the 252nd National Meeting & Exposition of the American Chemical Society (ACS).

“When you have uncontrolled internal bleeding, that’s when these particles could really make a difference,” says Erin B. Lavik, Sc.D. “Compared to injuries that aren’t treated with the nanoparticles, we can cut bleeding time in half and reduce total .”

Trauma remains a top killer of children and younger adults, and doctors have few options for treating internal bleeding. To address this great need, Lavik’s team developed a nanoparticle that acts as a bridge, binding to activated platelets and helping them join together to form clots. To do this, the nanoparticle is decorated with a molecule that sticks to a glycoprotein found only on the activated platelets.

Nano Body II 43a262816377a448922f9811e069be13Initial studies suggested that the nanoparticles, delivered intravenously, helped keep rodents from bleeding out due to brain and spinal , Lavik says. But, she acknowledges, there was still one key question: “If you are a rodent, we can save your life, but will it be safe for humans?”

As a step toward assessing whether their approach would be safe in humans, they tested the immune response toward the particles in pig’s blood. If a treatment triggers an immune response, it would indicate that the body is mounting a defense against the nanoparticle and that side effects are likely. The team added their nanoparticles to pig’s blood and watched for an uptick in complement, a key indicator of immune activation. The particles triggered complement in this experiment, so the researchers set out to engineer around the problem.

“We made a battery of particles with different charges and tested to see which ones didn’t have this immune-response effect,” Lavik explains. “The best ones had a neutral charge.” But neutral nanoparticles had their own problems. Without repulsive charge-charge interactions, the nanoparticles have a propensity to aggregate even before being injected. To fix this issue, the researchers tweaked their nanoparticle storage solution, adding a slippery polymer to keep the nanoparticles from sticking to each other.

Lavik also developed nanoparticles that are stable at higher temperatures, up to 50 degrees Celsius (122 degrees Fahrenheit). This would allow the particles to be stored in a hot ambulance or on a sweltering .

In future studies, the will test whether the new particles activate complement in human blood. Lavik also plans to identify additional critical safety studies they can perform to move the research forward. For example, the team needs to be sure that the do not cause non-specific clotting, which could lead to a stroke. Lavik is hopeful though that they could develop a useful clinical product in the next five to 10 years.

Explore further: Researchers take the inside route to halt bleeding

More information: Engineering nanoparticles to stop internal bleeding, 252nd National Meeting & Exposition of the American Chemical Society (ACS), 2016.

Abstract
Young people between 5 and 44 are most likely to die from a trauma, and the primary cause of death will be bleeding out. We have a range of technologies to control external bleeding, but there is a dearth of technologies for internal bleeding.
Following injury, platelets become activated at the injury site.

We have designed nanoparticles that are administered intravenously that bind with activated platelets to help form platelet plugs more rapidly. We have investigated the behavior of these particles in an number of in vitro systems to understand their behavior. We have also tested these particles in a number of models of trauma. The particles lead to a reduction in bleeding in a number of models of trauma including models of brain and spinal cord injury, and these particles lead to increased survival.
This work is not without challenges. One of the goals is to be able to use these particles in places where there are extreme temperatures and storage is challenging. We have engineering a variant of the hemostatic nanoparticles that is stable up to 50 C. A second challenge is that the intravenous administration of nanoparticles triggers complement activation as has been seen in a wide range of nanoparticle technologies from DOXIL to imaging agents.

The solution is generally to administer the particles very slowly to modulate the physiological responses to complement activation, but that is not an option when one is bleeding out, so we have had to develop variants that reduce complement activation and the accompanying complications.
Ultimately, we hope that this work provides insight and, potentially, a new approach to dealing with internal bleeding.

 

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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Ohio State: Nano-Mesh Could Clean Oil Spills for Less than $1 per square Foot


Oil Spills Ohio State 150415090028-largeThe unassuming piece of stainless steel mesh in a lab at The Ohio State University doesn’t look like a very big deal, but it could make a big difference for future environmental cleanups.


In tests, researchers mixed water with oil and poured the mixture onto the mesh. The water filtered through the mesh to land in a beaker below. The oil collected on top of the mesh, and rolled off easily into a separate beaker when the mesh was tilted.

The mesh coating is among a suite of nature-inspired nanotechnologies under development at Ohio State and described in two papers in the journal Nature Scientific Reports. Potential applications range from cleaning oil spills to tracking oil deposits underground.

“If you scale this up, you could potentially catch an oil spill with a net,” said Bharat Bhushan, Ohio Eminent Scholar and Howard D. Winbigler Professor of mechanical engineering at Ohio State.

Oil Spills Ohio State 150415090028-large

This mesh captures oil (red) while water (blue) passes through.
Credit: Photo by Jo McCulty, courtesy of The Ohio State University

The work was partly inspired by lotus leaves, whose bumpy surfaces naturally repel water but not oil. To create a coating that did the opposite, Bhushan and postdoctoral researcher Philip Brown chose to cover a bumpy surface with a polymer embedded with molecules of surfactant — the stuff that gives cleaning power to soap and detergent.

They sprayed a fine dusting of silica nanoparticles onto the stainless steel mesh to create a randomly bumpy surface and layered the polymer and surfactant on top.

The silica, surfactant, polymer, and stainless steel are all non-toxic and relatively inexpensive, said Brown. He estimated that a larger mesh net could be created for less than a dollar per square foot.

Because the coating is only a few hundred nanometers (billionths of a meter) thick, it is mostly undetectable. To the touch, the coated mesh doesn’t feel any bumpier than uncoated mesh. The coated mesh is a little less shiny, though, because the coating is only 70 percent transparent.

The researchers chose silica in part because it is an ingredient in glass, and they wanted to explore this technology’s potential for creating smudge-free glass coatings. At 70 percent transparency, the coating could work for certain automotive glass applications, such as mirrors, but not most windows or smartphone surfaces.

“Our goal is to reach a transparency in the 90-percent range,” Bhushan said. “In all our coatings, different combinations of ingredients in the layers yield different properties. The trick is to select the right layers.”

He explained that certain combinations of layers yield nanoparticles that bind to oil instead of repelling it. Such particles could be used to detect oil underground or aid removal in the case of oil spills.

The shape of the nanostructures plays a role, as well. In another project, research assistant Dave Maharaj is investigating what happens when a surface is made of nanotubes. Rather than silica, he experiments with molybdenum disulfide nanotubes, which mix well with oil. The nanotubes are approximately a thousand times smaller than a human hair.

Maharaj measured the friction on the surface of the nanotubes, and compressed them to test how they would hold up under pressure.

“There are natural defects in the structure of the nanotubes,” he said. “And under high loads, the defects cause the layers of the tubes to peel apart and create a slippery surface, which greatly reduces friction.”

Bhushan envisions that the molybdenum compound’s compatibility with oil, coupled with its ability to reduce friction, would make it a good additive for liquid lubricants. In addition, for micro- and nanoscale devices, commercial oils may be too sticky to allow for their efficient operation. Here, he suspects that the molybdenum nanotubes alone could be used to reduce friction.

This work began more than 10 years ago, when Bhushan began building and patenting nano-structured coatings that mimic the texture of the lotus leaf. From there, he and his team have worked to amplify the effect and tailor it for different situations.

“We’ve studied so many natural surfaces, from leaves to butterfly wings and shark skin, to understand how nature solves certain problems,” Bhushan said. “Now we want to go beyond what nature does, in order to solve new problems.”

“Nature reaches a limit of what it can do,” agreed Brown. “To repel synthetic materials like oils, we need to bring in another level of chemistry that nature doesn’t have access to.”

This work was partly funded by the American Chemical Society Petroleum Research Fund, the National Science Foundation, and Dexerials Corporation (formerly a chemical division of Sony Corp.) in Japan.


Story Source:

The above story is based on materials provided by Ohio State University.

Light-Controlled Molecule Switching


Light Control Switching 0422 id39800Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and the University of Konstanz are working on storing and processing information on the level of single molecules to create the smallest possible components that will combine autonomously to form a circuit. As recently reported in the academic journal Advanced Science (“Light-Induced Switching of Tunable Single-Molecule Junctions”), the researchers can switch on the current flow through a single molecule for the first time with the help of light.
Dr. Artur Erbe, physicist at the HZDR, is convinced that in the future molecular electronics will open the door for novel and increasingly smaller – while also more energy efficient – components or sensors: “Single molecules are currently the smallest imaginable components capable of being integrated into a processor.” Scientists have yet to succeed in tailoring a molecule so that it can conduct an electrical current and that this current can be selectively turned on and off like an electrical switch.
molecule
Light on – molecule on. For the first time a light beam switches a single molecule to closed state (red atoms). At the ends of the diarylethene molecule gold electrodes are attached. This way, the molecule functions as an electrical switch. (Image: HZDR/Pfefferkorn )
This requires a molecule in which an otherwise strong bond between individual atoms dissolves in one location – and forms again precisely when energy is pumped into the structure. Dr. Jannic Wolf, chemist at the University of Konstanz, discovered through complex experiments that a particular diarylethene compound is an eligible candidate. The advantages of this molecule, approximately three nanometres in size, are that it rotates very little when a point in its structure opens and it possesses two nanowires that can be used as contacts. The diarylethene is an insulator when open and becomes a conductor when closed. It thus exhibits a different physical behaviour, a behaviour that the scientists from Konstanz and Dresden were able to demonstrate with certainty in numerous reproducible measurements for the first time in a single molecule.
A computer from a test-tube
A special feature of these molecular electronics is that they take place in a fluid within a test-tube, where the molecules are contacted within the solution. In order to ascertain what effects the solution conditions have on the switching process, it was therefore necessary to systematically test various solvents. The diarylethene needs to be attached at the end of the nanowires to electrodes so that the current can flow. “We developed a nanotechnology at the HZDR that relies on extremely thin tips made of very few gold atoms. We stretch the switchable diarylethene compound between them,” explains Dr. Erbe.
When a beam of light then hits the molecule, it switches from its open to its closed state, resulting in a flowing current. “For the first time ever we could switch on a single contacted molecule and prove that this precise molecule becomes a conductor on which we have used the light beam,” says Dr. Erbe, pleased with the results. “We have also characterized the molecular switching mechanism in extremely high detail, which is why I believe that we have succeeded in making an important step toward a genuine molecular electronic component.”
Switching off, however, does not yet work with the contacted diarylethene, but the physicist is confident: “Our colleagues from the HZDR theory group are computing how precisely the molecule must rotate so that the current is interrupted. Together with the chemists from Konstanz, we will be able to accordingly implement the design and synthesis for the molecule.” However, a great deal of patience is required because it’s a matter of basic research. The diarylethene molecule contact using electron-beam lithography and the subsequent measurements alone lasted three long years. Approximately ten years ago, a working group at the University of Groningen in the Netherlands had already managed to construct a switch that could interrupt the current. The off-switch also worked only in one direction, but what couldn’t be proven at the time with certainty was that the change in conductivity was bound to a single molecule.
Nano-electronics in Dresden
One area of research focus in Dresden is what is known as self-organization. “DNA molecules are, for instance, able to arrange themselves into structures without any outside assistance. If we succeed in constructing logical switches from self-organizing molecules, then computers of the future will come from test-tubes,” Dr. Erbe prophesizes. The enormous advantages of this new technology are obvious: billion-euro manufacturing plants that are necessary for manufacturing today’s microelectronics could be a thing of the past. The advantages lie not only in production but also in operating the new molecular components, as they both will require very little energy.
Source: Helmholtz-Zentrum Dresden-Rossendorf

Inkjet-printed nanoparticle liquid metal could bring wearable tech, soft robotics


 

Ink Jet Soft Robotics id39681New research shows how inkjet-printing technology can be used to mass-produce electronic circuits made of liquid-metal alloys for “soft robots” and flexible electronics.
Elastic technologies could make possible a new class of pliable robots and stretchable garments that people might wear to interact with computers or for therapeutic purposes. However, new manufacturing techniques must be developed before soft machines become commercially feasible, said Rebecca Kramer, an assistant professor of mechanical engineering at Purdue University.
“We want to create stretchable electronics that might be compatible with soft machines, such as robots that need to squeeze through small spaces, or wearable technologies that aren’t restrictive of motion,” she said. “Conductors made from liquid metal can stretch and deform without breaking.”
A new potential manufacturing approach focuses on harnessing inkjet printing to create devices made of liquid alloys.
“This process now allows us to print flexible and stretchable conductors onto anything, including elastic materials and fabrics,” Kramer said.
A research paper about the method will appear on April 18 in the journal Advanced Materials (“Mechanically Sintered Gallium–Indium Nanoparticles”). The paper generally introduces the method, called mechanically sintered gallium-indium nanoparticles, and describes research leading up to the project. It was authored by postdoctoral researcher John William Boley, graduate student Edward L. White and Kramer.
flexible electronics
This artistic rendering depicts electronic devices created using a new inkjet-printing technology to produce circuits made of liquid-metal alloys for “soft robots” and flexible electronics. Elastic technologies could make possible a new class of pliable robots and stretchable garments that people might wear to interact with computers or for therapeutic purposes. (Image: Alex Bottiglio/Purdue University)
A printable ink is made by dispersing the liquid metal in a non-metallic solvent using ultrasound, which breaks up the bulk liquid metal into nanoparticles. This nanoparticle-filled ink is compatible with inkjet printing.
“Liquid metal in its native form is not inkjet-able,” Kramer said. “So what we do is create liquid metal nanoparticles that are small enough to pass through an inkjet nozzle. Sonicating liquid metal in a carrier solvent, such as ethanol, both creates the nanoparticles and disperses them in the solvent. Then we can print the ink onto any substrate. The ethanol evaporates away so we are just left with liquid metal nanoparticles on a surface.”
After printing, the nanoparticles must be rejoined by applying light pressure, which renders the material conductive. This step is necessary because the liquid-metal nanoparticles are initially coated with oxidized gallium, which acts as a skin that prevents electrical conductivity.
“But it’s a fragile skin, so when you apply pressure it breaks the skin and everything coalesces into one uniform film,” Kramer said. “We can do this either by stamping or by dragging something across the surface, such as the sharp edge of a silicon tip.”
The approach makes it possible to select which portions to activate depending on particular designs, suggesting that a blank film might be manufactured for a multitude of potential applications.
“We selectively activate what electronics we want to turn on by applying pressure to just those areas,” said Kramer, who this year was awarded an Early Career Development award from the National Science Foundation, which supports research to determine how to best develop the liquid-metal ink.
The process could make it possible to rapidly mass-produce large quantities of the film.
Future research will explore how the interaction between the ink and the surface being printed on might be conducive to the production of specific types of devices.
“For example, how do the nanoparticles orient themselves on hydrophobic versus hydrophilic surfaces? How can we formulate the ink and exploit its interaction with a surface to enable self-assembly of the particles?” she said.
The researchers also will study and model how individual particles rupture when pressure is applied, providing information that could allow the manufacture of ultrathin traces and new types of sensors.
Source: By Emil Venere, Purdue University

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