Tag Archives: plasmonics

E-ink discovery could be a gateway to cheaper solar cells and electronic touch pads

Non-toxic, inexpensive, and durable are words which, in combination, seem downright magical and all are mentioned in a July 31, 2013 news item on Azonano,

Researchers in the University of Minnesota’s College of Science and Engineering and the National Renewable Energy Laboratory in Golden, Colo., have overcome technical hurdles in the quest for inexpensive, durable electronics and solar cells made with non-toxic chemicals. …

“Imagine a world where every child in a developing country could learn reading and math from a touch pad that costs less than $10 or home solar cells that finally cost less than fossil fuels,” said Uwe Kortshagen, a University of Minnesota mechanical engineering professor and one of the co-authors of the paper.

The July 30, 2013 University of Minnesota news release, which originated the news item, explains the discovery and the issues the researchers are addressing and it mentions, as many do these days,  a patent,

The research team discovered a novel technology to produce a specialized type of ink from non-toxic nanometer-sized crystals of silicon, often called “electronic ink.” This “electronic ink” could produce inexpensive electronic devices with techniques that essentially print it onto inexpensive sheets of plastic.

“This process for producing electronics is almost like screen printing a number on a softball jersey,” said Lance Wheeler, a University of Minnesota mechanical engineering Ph.D. student and lead author of the research.

But it’s not quite that easy. Wheeler, Kortshagen and the rest of the research team developed a method to solve fundamental problems of silicon electronic inks.

First, there is the ubiquitous need of organic “soap-like” molecules, called ligands, that are needed to produce inks with a good shelf life, but these molecules cause detrimental residues in the films after printing. This leads to films with electrical properties too poor for electronic devices. Second, nanoparticles are often deliberately implanted with impurities, a process called “doping,” to enhance their electrical properties.

In this new paper, researchers explain a new method to use an ionized gas, called nonthermal plasma, to not only produce silicon nanocrystals, but also to cover their surfaces with a layer of chlorine atoms. This surface layer of chlorine induces an interaction with many widely used solvents that allows production of stable silicon inks with excellent shelf life without the need for organic ligand molecules. In addition, the researchers discovered that these solvents lead to doping of films printed from their silicon inks, which gave them an electrical conductivity 1,000 times larger than un-doped silicon nanoparticle films. The researchers have a provisional patent on their findings.

Here’s a link to and a citation for the published paper,

Hypervalent surface interactions for colloidal stability and doping of silicon nanocrystals by Lance M. Wheeler, Nathan R. Neale, Ting Chen, & Uwe R. Kortshagen. Nature Communications 4, Article number: 2197 doi:10.1038/ncomms3197 Published 29 July 2013

The paper is open access. The researchers also offer a brief video describing the process of making the nanocrystals,

Here’s the video description provided by the researchers (from http://www.youtube.com/watch?v=5Un_HnOl6lQ&feature=youtu.be),

This video shows how silicon nanocrystals are synthesized in a plasma reactor. Inert argon gas flows from the top of the reactor through a glass tube. Fifteen watts of radio frequency power is applied to the copper ring electrodes to ionize the argon gas and produce what is called a plasma. A gas containing silicon (silane) is injected into the reactive plasma environment to produce silicon nanocrystals. Though the plasma is energetic enough to produce these tiny crystals, the glass tube remains cool enough to touch. The plasma is a reactive environment used to produce silicon nanocrystals that can be applied to inexpensive, next-generation electronics.

Unique ‘printing’ process boosts supercapacitor performance

In addition to creating energy, we also need to store some of it for future use as a July 29, 2013 news release from the University of Central Florida notes,

Researchers at the University of Central Florida have developed a technique to increase the energy storage capabilities of supercapacitors, essential devices for powering high-speed trains, electric cars, and the emergency doors of the Airbus A380.

The finding, which offers a solution to a problem that has plagued the growing multi-billion dollar industry, utilizes a unique three-step process to “print” large – area nanostructured electrodes, structures necessary to improve electrical conductivity and boost performance of the supercapacitor.

Jayan Thomas, an assistant professor in UCF’s NanoScience Technology Center, led the project which is featured in the June edition of Advanced Materials, one of the leading peer-reviewed scientific journals covering materials science in the world. Thomas’ research appears on the journal’s highly-coveted frontispiece, the illustration page of the journal that precedes the title page.

The news release goes on to describe the supercapacitor issue the researchers were addressing,

Supercapacitors have been around since the 1960’s. Similar to batteries, they store energy. The difference is that supercapacitors can provide higher amounts of power for shorter periods of time, making them very useful for heavy machinery and other applications that require large amounts of energy to start.  However, due to their innate low energy density; supercapacitors are limited in the amount of energy that they can store.

“We had been looking at techniques to print nanostructures,” said Thomas. “Using a simple spin-on nanoprinting (SNAP) technique, we can print highly-ordered nanopillars without the need for complicated development processes. By eliminating these processes, it allows multiple imprints to be made on the same substrate in close proximity.“

This simplified fabrication method devised by Thomas and his team is very attractive for the next-generation of energy storage systems. “What we’ve found is by adding the printed ordered nanostructures to supercapacitor electrodes, we can increase their surface area many times,” added Thomas. “We discovered that supercapacitors made using the SNAP technique can store much more energy than ones made without.”

Here’s a link to and a citation for the research paper abut this new technique for supercapacitors,

Energy Storage: Highly Ordered MnO2 Nanopillars for Enhanced Supercapacitor Performance (Adv. Mater. 24/2013) by Zenan Yu, Binh Duong, Danielle Abbitt, and Jayan Thomas. Article first published online: 20 JUN 2013 DOI: 10.1002/adma.201370160 Advanced Materials Volume 25, Issue 24, page 3301, June 25, 2013.

Lead researcher Thomas was recently featured in a video for his work on creating plasmonic nanocrystals from gold nanoparticles (from the news release),

Thomas, who is also affiliated with the College of Optics and Photonics (CREOL), and the College of Engineering, was recently featured on American Institute of Physics’ Inside Science TV for his collaborative research to develop a new material using nanotechnology that could potentially help keep pilots safe by diffusing harmful laser light.

Here’s the video,

You can find videos, news, and blogs featuring other research at Inside Science and you can find out more about Dr. Jayan Thomas here.

Cow blood declumps (stabilizes) gold nanoparticles in a solution

Rice University (Texas, US) researchers have discovered a means of stabilizing gold nanoparticles in a variety of solutions including one of the harshest, salt solutions. From the May 14, 2013 news item on Nanowerk (Note: A link has been removed),

A protein from cow blood has the remarkable ability to keep gold nanoparticles from clumping in a solution. The discovery could lead to improved biomedical applications and contribute to projects that use nanoparticles in harsh environments.

Bovine serum albumin (BSA) forms a protein “corona” around gold nanoparticles that keeps them from aggregating, particularly in high-salt environments like seawater. The new research by the Rice University labs of chemists Stephan Link and Christy Landes was published by the American Chemical Society journal ACS Sustainable Chemistry and Engineering (“Adsorption of a Protein Monolayer via Hydrophobic Interactions Prevents Nanoparticle Aggregation under Harsh Environmental Conditions”).

The May 13, 2012 Rice University news release by Mike Williams, which originated the news item, describes the researchers and the nature of their work,

Link’s primary interest is in the plasmonic properties of nanoparticles. Landes’ work incorporates protein binding and molecular transport. The BSA research combines their unique talents with those of Sergio Dominguez-Medina, a graduate student in Link’s lab who studied to be a physicist at Monterrey Tech and was drawn to this interdisciplinary project during an undergraduate fellowship at Link’s Rice lab.

“Initially, we wanted to look at nanoparticles in solution with something they would encounter frequently in blood: serum albumin,” Landes said. “In our first experiments, Sergio reported the very efficient, reasonably fast and irreversible binding the moment he put nanoparticles into a solution that contained serum albumin.”

“It turned out the salt is actually driving this binding,” Dominguez-Medina said.

Without BSA, gold nanoparticles in a salty solution quickly aggregate and fall to the bottom. “That by itself is undesirable for biomedical or industrial applications, because it could lead to toxicity issues,” he said. “The nanoparticles get more hydrophobic because in the presence of salts, the excess charges on the surface (which discourage clumping) are actually removed.” But if BSA is present, the proteins are drawn to the nanoparticles faster than the particles are drawn to each other.

“Once the protein is bound, it gives a super protection against any type of salt-induced aggregation. We think this could be used for the stabilization of nanoparticles in environments where, right now, it hasn’t been achieved,” Dominguez-Medina said.

He said the discovery also offers the possibility that nanoparticles might be made more compatible for treating humans by using a patient’s own albumin. “Albumin is really easy to purify and the process is well-established,” he said.

Here’s a little more about the plasmonics of the situation and how this discovery about cow blood protein might apply in biomedical and other applications (from the news release),

The ability of gold nanoparticles to absorb and redirect light is at the heart of several breakthrough technologies being developed at Rice and elsewhere. Most notable are a nanoparticle-based cancer treatment now in human testing that was developed by Professor Naomi Halas and former Rice colleague Jennifer West, and Halas’ project to convert solar energy directly into steam for sanitation and water purification.

“The only way nanoparticles exhibit their really nice optical properties in very specific optical frequencies is if they’re separated,” Landes said.

The key words in Landes comment is ‘separated’ (from the news release),

Because pure gold nanoparticles are so hydrophobic, they naturally clump together in a solution unless chemically treated. “A lot of industrial effort goes into keeping stuff off of surfaces, like contact lenses and ship hulls,” she said. “That involves chemically altering the surfaces to prevent unwanted adsorption, or in the case of nanoparticles, unwanted aggregation.”

Protecting the surface is costly, Link said. “But we found we could take nanoparticles prepared in the cheapest way, with a sodium citrate coating that stabilizes the particles by electrostatic repulsion, and add BSA, which coats the particles and makes them really stable.”

Adding the BSA seems logical when one of the scientists explains the reasoning (from the news release),

Albumin is the most common protein in blood, and the bovine version shares 98 percent of its amino acid sequence with human serum albumin. “One of its main purposes, biologically, is to take things that aren’t water-soluble, bind to them and make them soluble,” Landes said. “When you combine it with gold nanoparticles, BSA trades places with the cheap citrate, which isn’t a good protective layer, to form the monolayer corona, which is very strong and protective.”

Aside from obvious biomedical applications (e.g. implants and joint replacements), there are desalination and fuel cell applications (from the news release),

Seawater is the very definition of a harsh environment, Landes said. “One of the problems with desalination applications and, similarly, with fuel cells, is that saline or acidic conditions are very corrosive,” she said. “That’s why you have to use platinum electrodes in fuel cells – not because they’re better than cheaper materials at catalysis, but because they don’t corrode in a harsh environment.” She sees promise for BSA-treated gold nanoparticles in both applications.

The researchers have other plans as well (from the news release),

The researchers are now looking at how well gold nanoparticles retain their albumin corona with repeated use. “Gold is expensive,” Landes said. “But the beauty of it is that if you can reuse it, it only costs you once.”

They also want to use spectroscopy to see how the binding mechanism works in real time, Link said. “We want to study what’s happening at the interface of nanoparticles and biologically relevant media” that may eventually include DNA, RNA and drugs for delivery to cells, he said.

Link plans to see how BSA can be used in combination with gold nanorods. Because nanorods’ plasmonic properties can be tuned, “we can get them into the biological window, which is near-infrared light,” he said. Near-IR from lasers is used to activate, by heating, Halas’ and West’s cancer-killing nanoshells. Nanorods may also offer ways to combine BSA and other useful proteins by coating the tips and sides separately.

For interested parties, here’s a link to and a citation for the published paper,

Adsorption of a Protein Monolayer via Hydrophobic Interactions Prevents Nanoparticle Aggregation under Harsh Environmental Conditions by Sergio Dominguez-Medina, Jan Blankenburg, Jana Olson, Christy F. Landes, and Stephan Link. ACS Sustainable Chem. Eng., Article ASAP DOI: 10.1021/sc400042h
Publication Date (Web): April 3, 2013
Copyright © 2013 American Chemical Society

Unusually for the American Chemical Society (ACS), this paper appears to be open access; I was able to access the full HTML version today, May 14, 2013 at 10:10 am PDT.

Namdiatream; a European multimodal diagnostics project

I’ve written about lab-on-a-chip projects, point-of-care diagnostics, and other such initiatives on several occasions, most recently in a Mar. 1, 2013 posting about a technique where powder is used to make the diagnostic device more portable. This time it was a Europe-wide project described in a Mar. 4, 2013 news item on Nanowerk,which caught my attention (Note: A link has been removed),

The plan of the EU-funded consortium Nanotechnological toolkits for multi-modal disease diagnostics and treatment monitoring (Namdiatream) is not to cure cancer, per se, but to boost the sensitivity of diagnostics and the ability to monitor progress during treatment. They focused on three types – breast, prostate and lung cancer.

… The prototype devices being developed during the four-year project will detect common cancer cells much earlier and, with timely treatment, improve the chances of recovery.

According to the project leader, Professor Yuri Volkov of Trinity College Dublin’s School of Medicine, the portable nanodevices are based on innovative lab-on-a-chip, -bead and -wire technologies applicable in different settings – clinical, research, or point of care (i.e. hospitals). These lab-on-x technologies exploit the photo-luminescent (‘glow-in-the-dark’ light emitting), plasmonic (‘light-on-a-wire’), magnetic and unique optical properties of nanomaterials.

Volkov offers some insight into how the project started and its current state of evolution (from the news item),

This is ground-breaking work made possible thanks to advanced technology but also to EU funding for cross-border investigations. Teams across Europe were doing related but fragmented research, suggests Prof. Volkov. This risked leaving a team dangling if their approach failed or lacked funding.

“So we integrated our research and identified joint strengths to help one another develop the best technological approaches in case something didn’t work in one, or synergies were identified, thereby increasing the chances of wider success.”

At its half-way stage, notes Prof. Volkov, Namdiatream underwent a natural evolution when it became clear that by merging and refocusing work in some areas – i.e. in fluorescent nanomaterial technology and magnetic nanowire barcodes – it would speed up industrial implementation efforts.

“Now, work on the preclinical prototype devices is well under way,” he confirms. But one of the many remaining challenges is to calibrate their sensitivity, so that they do not give false readings, for instance.

The Namdiatream (Nanotechnological Toolkits for Multi-Modal Disease Diagnostics and Treatment Monitoring) home page offers more detail about the project,

Namdiatream is a truly interdisciplinary and Pan-european consortium that builds around 7 High-Tech SMEs [small to medium enterprises], 2 Multinational industries and 13 academic institutions. NAMDIATREAM will develop nanotechnology-based toolkit to enable early detection and imaging of molecular biomarkers of the most common cancer types and of cancer metastases, as well as permitting the identification of cells indicative of early-stage disease onset. The project is built on the innovative technology concepts of super-sensitive “lab-on-a-bead”, “lab-on-a-chip” and “lab-on-a-wire” nano-devices.

Interestingly, this too was on the home page,

The ETP Nanomedicine documents point out that nanotechnology has yet to deliver practical solutions for the patients and clinicians in their struggle against common, socially and economically important diseases such as cancer. Therefore NAMDIATREAM results will firstly aim to deliver to the diagnostic and medical imaging device companies involved in the consortium, and the clinical and academic partners. This could further provide the basis for cancer therapeutics as it will be possible to accurately assess the kinetics of cancer cell destruction during the course of appropriate therapy.

Mechanics of quantum kissing

“It is as if you can kiss without quite touching lips,” says Professor Jeremy Baumberg from the University of Cambridge Cavendish Laboratory in the University of Cambridge’s Nov. 7, 2012 news release about quantum electron jumps,

Even empty gaps have a colour. Now scientists have shown that quantum jumps of electrons can change the colour of gaps between nano-sized balls of gold. The new results, published today in the journal Nature, set a fundamental quantum limit on how tightly light can be trapped.

The team from the Universities of Cambridge, the Basque Country and Paris have combined tour de force experiments with advanced theories to show how light interacts with matter at nanometre sizes. The work shows how they can literally see quantum mechanics in action in air at room temperature.

As for the kissing, it all starts with metal and jumping electrons,

Because electrons in a metal move easily, shining light onto a tiny crack pushes electric charges onto and off each crack face in turn, at optical frequencies. The oscillating charge across the gap produces a ‘plasmonic’ colour for the ghostly region in-between, but only when the gap is small enough.

Team leader Professor Jeremy Baumberg from the University of Cambridge Cavendish Laboratory suggests we think of this like the tension building between a flirtatious couple staring into each other’s eyes. As their faces get closer the tension mounts, and only a kiss discharges this energy.

H/T to the Nov. 7, 2012 news item on ScienceDaily where I first learned of quantum kissing,

In the new experiments, the gap is shrunk below 1nm (1 billionth of a metre) which strongly reddens the gap colour as the charge builds up. However because electrons can jump across the gap by quantum tunnelling, the charge can drain away when the gap is below 0.35nm, seen as a blue-shifting of the colour. …

Prof Javier Aizpurua, leader of the theoretical team from San Sebastian complains: “Trying to model so many electrons oscillating inside the gold just cannot be done with existing theories.” He has had to fuse classical and quantum views of the world to even predict the colour shifts seen in experiment.

The new insights from this work suggest ways to measure the world down to the scale of single atoms and molecules, and strategies to make useful tiny devices.

Something to think about the next time you kiss.

Rainbows, what are we going to do with them?

The title is attention-getting initially then quickly leads to confusion for anyone not familiar with plasmonics, “Trapping a rainbow: Researchers slow broadband light waves with plasmonic structures.” I have to confess to being more interested in the use of the metaphor than I am in the science. However in deference to any readers who are more taken by the science, here’s more from the March 14, 2011 news item on Nanowerk,

A team of electrical engineers and chemists at Lehigh University have experimentally verified the “rainbow” trapping effect, demonstrating that plasmonic structures can slow down light waves over a broad range of wavelengths.

The idea that a rainbow of broadband light could be slowed down or stopped using plasmonic structures has only recently been predicted in theoretical studies of metamaterials. The Lehigh experiment employed focused ion beams to mill a series of increasingly deeper, nanosized grooves into a thin sheet of silver. By focusing light along this plasmonic structure, this series of grooves or nano-gratings slowed each wavelength of optical light, essentially capturing each individual color of the visible spectrum at different points along the grating. The findings hold promise for improved data storage, optical data processing, solar cells, bio sensors and other technologies.

While the notion of slowing light or trapping a rainbow sounds like ad speak, finding practical ways to control photons—the particles that makes up light— could significantly improve the capacity of data storage systems and speed the processing of optical data.

The research required the ability to engineer a metallic surface to produce nanoscale periodic gratings with varying groove depths. This alters the optical properties of the nanopatterned metallic surface, called Surface Dispersion Engineering. The broadband surface light waves are then trapped along this plasmonic metallic surface with each wavelength trapped at a different groove depth, resulting in a trapped rainbow of light.

You can get still more scientific detail in the item but I found a later posting, April 12, 2011 news item, also on Nanowerk, where the researcher Qiaoquiang Gan (pronounced “Chow-Chung” and “Gone”) gave this description for his work,

An electrical engineer at the University at Buffalo, who previously demonstrated experimentally the “rainbow trapping effect” [emphasis mine] — a phenomenon that could boost optical data storage and communications — is now working to capture all the colors of the rainbow.

In a paper published March 29 in the Proceedings of the National Academy of Sciences, Qiaoquiang Gan (pronounced “Chow-Chung” and “Gone”), PhD, an assistant professor of electrical engineering at the University at Buffalo’s School of Engineering and Applied Sciences, and his colleagues at Lehigh University, where he was a graduate student, described how they slowed broadband light waves using a type of material called nanoplasmonic structures.

Gan explains that the ultimate goal is to achieve a breakthrough in optical communications called multiplexed, multiwavelength communications, where optical data can potentially be tamed at different wavelengths, thus greatly increasing processing and transmission capacity.

“Light is usually very fast, but the structures I created can slow broadband light significantly,” says Gan. “It’s as though I can hold [emphasis mine] the light in my hand.”

I like the notion of ‘holding’ a rainbow better than ‘trapping’ one. (ETA April 18, 2011: The original sentence, now placed at the end of this posting, has been replaced with this: There’s a big difference between the two verbs, trapping and holding and each implies a difference relationship to the object. Which would you prefer, to be trapped or to be held? What does it mean to the one who does the trapping or the holding? Two difference relationships to the object and to the role of a scientist are implied.

It’s believed that the metaphors we use when describing science have a powerful impact on how science is viewed and practiced. One example I have at hand is a study by Kevin Dunbar mentioned in my Jan. 4, 2010 posting (scroll down) where he illustrates how scientists use metaphors to achieve scientific breakthroughs. Logically, if metaphors help us achieve breakthroughs, then they are quite capable of constraining us as well.

Meanwhile, this gives me an excuse to include this video of a Hawaiian singer, Israel Kamakawiwo’ole and his extraordinary version of Somewhere over the Rainbow. Happy Weekend!

The original (April 15, 2011) sentence:
It’s more gentle and implies a more humble attitude and I suspect it would ultimately prove more fruitful.