Eco-friendly nanoparticles for artificial photosynthesis – Indium-based quantum dots produce clean hydrogen fuel from water and sunlight for a sustainable Energy Source

Synthetic Photo Synthesis id51165
Researchers at the University of Zurich have developed a nanoparticle type for novel use in artificial photosynthesis by adding zinc sulfide on the surface of indium-based quantum dots. These quantum dots produce clean hydrogen fuel from water and sunlight – a sustainable source of energy. They introduce new eco-friendly and powerful materials to solar photocatalysis.
Quantum dots are true all-rounders. These material structures, which are only a few nanometers in size, display a similar behavior to that of molecules or atoms, and their form, size and number of electrons can be modulated systematically. This means that their electrical and optical characteristics can be customized for a number of target areas, such as new display technologies, biomedical applications as well as photovoltaics and photocatalysis.

Fuel production using sunlight and water

Another current line of application-oriented research aims to generate hydrogen directly from water and solar light. Hydrogen, a clean and efficient energy source, can be converted into forms of fuel that are used widely, including methanol and gasoline. The most promising types of quantum dots previously used in energy research contain cadmium, which has been banned from many commodities due to its toxicity.
The team of Greta Patzke, Professor at the Department of Chemistry of the University of Zurich, and scientists from Southwest Petroleum University in Chengdu and the Chinese Academy of Sciences have now developed a new type of nanomaterials without toxic components for photocatalysis (Nature Communications“Efficient Photocatalytic Hydrogen Evolution with Ligand Engineered All-Inorganic InP and InP/ZnS Colloidal Quantum Dots”).

Indium-containing core with a thin layer of zinc sulfide

The three-nanometer particles consist of a core of indium phosphide with a very thin surrounding layer of zinc sulfide and sulfide ligands.
Schematic representation of photocatalytic hydrogen production with InP/ZnS quantum dots in a typical assay
Schematic representation of photocatalytic hydrogen production with InP/ZnS quantum dots in a typical assay. (Image: Shan Yu) (click on image to enlarge)
“Compared to the quantum dots that contain cadmium, the new composites are not only environmentally friendly, but also highly efficient when it comes to producing hydrogen from light and water,” explains Greta Patzke.
Sulfide ligands on the quantum dot surface were found to facilitate the crucial steps involved in light-driven chemical reactions, namely the efficient separation of charge carriers and their rapid transfer to the nanoparticle surface.

Great potential for eco-friendly applications

The newly developed cadmium-free nanomaterials have the potential to serve as a more eco-friendly alternative for a variety of commercial fields.
“The water-soluble and biocompatible indium-based quantum dots can in the future also be tested in terms of biomass conversion to hydrogen. Or they could be developed into low-toxic biosensors or non-linear optical materials, for example,” adds Greta Patzke.
She will continue to focus on the development of catalysts for artificial photosynthesis within the University Research Priority Program LightChEC. This interdisciplinary research program aims to develop new molecules, materials and processes for the direct storage of solar light energy in chemical bonds.
Source: University of Zurich

Big renewable energy source could be at our feet – literally: U of Wisconsin

energy-at-our-feet-161020131916_1_540x360Associate Professor Xudong Wang holds a prototype of the researchers’ energy harvesting technology, which uses wood pulp and harnesses nanofibers. The technology could be incorporated into flooring and convert footsteps on the flooring into usable electricity.
Credit: Stephanie Precourt/UW-Madison
Source: University of Wisconsin-Madison




Flooring can be made from any number of sustainable materials, making it, generally, an eco-friendly feature in homes and businesses alike. Now, flooring could be even more “green,” thanks to an inexpensive, simple method that allows them to convert footsteps into usable electricity.

Flooring can be made from any number of sustainable materials, making it, generally, an eco-friendly feature in homes and businesses alike.

Now, flooring could be even more “green,” thanks to an inexpensive, simple method developed by University of Wisconsin-Madison materials engineers that allows them to convert footsteps into usable electricity.

Xudong Wang, an associate professor of materials science and engineering at UW-Madison, his graduate student Chunhua Yao, and their collaborators published details of the advance Sept. 24 in the journal Nano Energy.

The method puts to good use a common waste material: wood pulp. The pulp, which is already a common component of flooring, is partly made of cellulose nanofibers. They’re tiny fibers that, when chemically treated, produce an electrical charge when they come into contact with untreated nanofibers.

nano-fiber-flooring-button-3When the nanofibers are embedded within flooring, they’re able to produce electricity that can be harnessed to power lights or charge batteries. And because wood pulp is a cheap, abundant and renewable waste product of several industries, flooring that incorporates the new technology could be as affordable as conventional materials.


While there are existing similar materials for harnessing footstep energy, they’re costly, nonrecyclable, and impractical at a large scale.

Wang’s research centers around using vibration to generate electricity. For years, he has been testing different materials in an effort to maximize the merits of a technology called a triboelectric nanogenerator (TENG). Triboelectricity is the same phenomenon that produces static electricity on clothing. Chemically treated cellulose nanofibers are a simple, low-cost and effective alternative for harnessing this broadly existing mechanical energy source, Wang says.

The UW-Madison team’s advance is the latest in a green energy research field called “roadside energy harvesting” that could, in some settings, rival solar power — and it doesn’t depend on fair weather. Researchers like Wang who study roadside energy harvesting methods see the ground as holding great renewable energy potential well beyond its limited fossil fuel reserves.

“Roadside energy harvesting requires thinking about the places where there is abundant energy we could be harvesting,” Wang says. “We’ve been working a lot on harvesting energy from human activities. One way is to build something to put on people, and another way is to build something that has constant access to people. The ground is the most-used place.”

Heavy traffic floors in hallways and places like stadiums and malls that incorporate the technology could produce significant amounts of energy, Wang says. Each functional portion inside such flooring has two differently charged materials — including the cellulose nanofibers, and would be a millimeter or less thick. The floor could include several layers of the functional unit for higher energy output.grand-central-station-footsteps

“So once we put these two materials together, electrons move from one to another based on their different electron affinity,” Wang says.

The electron transfer creates a charge imbalance that naturally wants to right itself but as the electrons return, they pass through an external circuit. The energy that process creates is the end result of TENGs.

Wang says the TENG technology could be easily incorporated into all kinds of flooring once it’s ready for the market. Wang is now optimizing the technology, and he hopes to build an educational prototype in a high-profile spot on the UW-Madison campus where he can demonstrate the concept. He already knows it would be cheap and durable.

“Our initial test in our lab shows that it works for millions of cycles without any problem,” Wang says. “We haven’t converted those numbers into year of life for a floor yet, but I think with appropriate design it can definitely outlast the floor itself.”

Story Source:

Materials provided by University of Wisconsin-Madison. Original written by Will Cushman. Note: Content may be edited for style and length.

Journal Reference:

  1. Chunhua Yao, Alberto Hernandez, Yanhao Yu, Zhiyong Cai, Xudong Wang. Triboelectric nanogenerators and power-boards from cellulose nanofibrils and recycled materials.Nano Energy, 2016; 30: 103 DOI:10.1016/j.nanoen.2016.09.036

University of Wisconsin: Simulating complex catalysts key to making cheap, powerful fuel cells

Cheap Fuel Cells 081016 id44194Using a unique combination of advanced computational methods, University of Wisconsin-Madison chemical engineers have demystified some of the complex catalytic chemistry in fuel cells — an advance that brings cost-effective fuel cells closer to reality.

“Understanding reaction mechanisms is the first step toward eventually replacing expensive platinum in fuel cells with a cheaper material,” says Manos Mavrikakis, a UW-Madison professor of chemical and biological engineering.
Mavrikakis and colleagues at Osaka University in Japan published details of the advance Monday, Aug. 8, in the journal Proceedings of the National Academy of Sciences (“Ab initio molecular dynamics of solvation effects on reactivity at electrified interfaces”).


Methanol Molecules
Modeling how methanol interacts with platinum catalysts inside fuel cells in realistic environments becomes even more complicated because distances between the atoms can change as molecules dance near the charged surface. (Image: Manos Mavrikakis)

Fuel cells generate electricity by combining electrons and protons — provided by a chemical fuel such as methanol — with oxygen from the air. To make the reaction that generates protons faster, fuel cells typically contain catalysts. With the right catalyst and enough fuel and air, fuel cells could provide power very efficiently.


Someday, fuel cells could make laptop batteries obsolete. Mere tablespoons of methanol could potentially provide up to 20 hours of continuous power. But alternatives to the expensive platinum catalyst in today’s fuel cells haven’t emerged because scientists still don’t fully understand the complicated chemistry required to produce protons and electrons from fuels.


And finding a good catalyst is no trivial task.


“People arrived at using platinum for a catalyst largely by trial and error, without understanding how the reaction takes place,” says Mavrikakis. “Our efforts developed a big picture of how the reaction is happening, and we hope to do the same analysis with other materials to help find a cheaper alternative.”


At first glance, the chemistry sounds straightforward: Methanol molecules awash in a watery milieu settle down on a platinum surface and give up one of their four hydrogen atoms. The movement of those electrons from that hydrogen atom make an electric current.


In reality, the situation is not so simple.


“All of these molecules, the water and the methanol, are actually dancing around the surface of the catalyst and fluctuating continuously,” says Mavrikakis. “Following the dynamics of these fluctuating motions all the time, and in the presence of an externally applied electric potential, is really very complicated.”


The water molecules are not wallflowers, sitting on the sidelines of the methanol molecules reacting with platinum; rather, they occasionally cut in to the chemical dance. And varying voltage on the electrified surface of the platinum catalyst tangles the reaction’s tempo even further.


Previously, chemists only simulated simplified scenarios — fuel cells without any water in the mix, or catalytic surfaces that didn’t crackle with electricity. Unsurprisingly, conclusions based on such oversimplifications failed to fully capture the enormous complexity of real-world reactions.


Mavrikakis and colleagues combined their expertise in two powerful computational techniques to create a more accurate description of a very complex real environment.
They first used density functional theory to solve for quantum mechanical forces and energies between individual atoms, then built a scheme upon those results using molecular dynamics methods to simulate large ensembles of water and methanol molecules interacting among themselves and with the platinum surface.
The detailed simulations revealed that the presence of water in a fuel cell plays a huge role in dictating which hydrogen atom breaks free from methanol first — a result that simpler methods could never have captured. Electric charge also determined the order in which methanol breaks down, surprisingly switching the preferred first step at the positive electrode.


This type of information enables scientists to predict which byproducts might accumulate in a reaction mixture, and select better ingredients for future fuel cells.
“Modeling enables you to come up with an informed materials design,” says Mavrikakis, whose work was supported by the Department of Energy and the National Science Foundation. “We plan to investigate alternative fuels, and a range of promising and cheaper catalytic materials.”


The results represent the culmination of six years of effort across two continents. Jeffrey Herron, the first author on the paper, started developing the methodologies during a summer visit to work under the paper’s second author, Professor Yoshitada Morikawa in the Division of Precision Science & Technology and Applied Physics at Osaka University.
Herron, who completed his doctorate in 2015 and is now a senior engineer for The Dow Chemical Company, further refined these approaches under Mavrikakis’ guidance over several subsequent years in Madison.
“A lot of work over many years went into this paper,” says Mavrikakis. “The world needs fuel cells, but without understanding how the reaction takes place, there is no rational way to improve.”
Source: University of Wisconsin-Madison

Read more: Simulating complex catalysts key to making cheap, powerful fuel cells

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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A new kind of biodegradable computer wood chip – Application: Environmentally Friendly-Flexible (Wearable?) Electronics

Bio Computer Chip 053015 uploaded_1076Portable electronics — typically made of non-renewable, non-biodegradable and potentially toxic materials — are discarded at an alarming rate in consumers’ pursuit of the next best electronic gadget.

In an effort to alleviate the environmental burden of electronic devices, a team of University of Wisconsin-Madison researchers has collaborated with researchers in the Madison-based U.S. Department of Agriculture Forest Products Laboratory (FPL) to develop a surprising solution: a semiconductor chip made almost entirely of wood.
The research team, led by UW-Madison electrical and computer engineering professor Zhenqiang “Jack” Ma, described the new device in a paper published today (May 26, 2015) by the journal Nature Communications. The paper demonstrates the feasibility of replacing the substrate, or support layer, of a computer chip, with cellulose nanofibril (CNF), a flexible, biodegradable material made from wood.
“The majority of material in a chip is support. We only use less than a couple of micrometers for everything else,” Ma says. “Now the chips are so safe you can put them in the forest and fungus will degrade it. They become as safe as fertilizer.”
Zhiyong Cai, project leader for an engineering composite science research group at FPL, has been developing sustainable nanomaterials since 2009.
“If you take a big tree and cut it down to the individual fiber, the most common product is paper. The dimension of the fiber is in the micron stage,” Cai says. “But what if we could break it down further to the nano scale? At that scale you can make this material, very strong and transparent CNF paper.”
“You don’t want it to expand or shrink too much. Wood is a natural hydroscopic material and could attract moisture from the air and expand,” Cai says. “With an epoxy coating on the surface of the CNF, we solved both the surface smoothness and the moisture barrier.”Working with Shaoqin “Sarah” Gong, a UW-Madison professor of biomedical engineering, Cai’s group addressed two key barriers to using wood-derived materials in an electronics setting: surface smoothness and thermal expansion. Gong and her students also have been studying bio-based polymers for more than a decade. CNF offers many benefits over current chip substrates, she says.
“The advantage of CNF over other polymers is that it’s a bio-based material and most other polymers are petroleum-based polymers. Bio-based materials are sustainable, bio-compatible and biodegradable,” Gong says. “And, compared to other polymers, CNF actually has a relatively low thermal expansion coefficient.”
The group’s work also demonstrates a more environmentally friendly process that showed performance similar to existing chips. The majority of today’s wireless devices use gallium arsenide-based microwave chips due to their superior high-frequency operation and power handling capabilities. However, gallium arsenide can be environmentally toxic, particularly in the massive quantities of discarded wireless electronics.
Yei Hwan Jung, a graduate student in electrical and computer engineering and a co-author of the paper, says the new process greatly reduces the use of such expensive and potentially toxic material.
“I’ve made 1,500 gallium arsenide transistors in a 5-by-6 millimeter chip. Typically for a microwave chip that size, there are only eight to 40 transistors. The rest of the area is just wasted,” he says. “We take our design and put it on CNF using deterministic assembly technique, then we can put it wherever we want and make a completely functional circuit with performance comparable to existing chips.”
While the biodegradability of these materials will have a positive impact on the environment, Ma says the flexibility of the technology can lead to widespread adoption of these electronic chips.
“Mass-producing current semiconductor chips is so cheap, and it may take time for the industry to adapt to our design,” he says. “But flexible electronics are the future, and we think we’re going to be well ahead of the curve.”

Transparent Optogenetic Brain Implants: Amazing Use for Graphene!

1-Brain Transparentgraphene1-640x353Transparency is the key to many technologies. Thin conductive films, like those made from ITO (indium tin oxide) for example, can carry currents or create electric fields critical for displays or solar panels without blocking all the light.

The most powerful brain implants being built today have exactly this same requirement. Namely, they need to record fast electric signals with conductive arrays while permitting light to pass out through them for high-resolution imaging — and just to take it up a notch — let light pass in to permit optogenetic control directly under the implant for the icing on the cake.

Unfortunately, ITO is generally too stiff and too brittle for brain implants. Even if it could be made flexible, the high temperatures required to process it are incompatible with many of the materials (like parylene) that are used in the implants. Furthermore the transparency bandwidth of ITO is insufficient to fully exploit the wide spectrum of new UV and IR capable optogenetic proteins that have researchers fairly excited. The solution, now emerging from multiple labs throughout the universe is to build flexible, transparent electrode arrays from graphene. Two studies in the latest issue of Nature Communications, one from the University of Wisconsin-Madison and the other from Penn, describe how to build these devices.

1-Brain Transparentgraphene1-640x353

The University of Wisconsin researchers are either a little bit smarter or just a little bit richer, because they published their work open access. It’s a no-brainer then that we will focus on their methods first, and also in more detail. To make the arrays, these guys first deposited the parylene (polymer) substrate on a silicon wafer, metalized it with gold, and then patterned it with an electron beam to create small contact pads. The magic was to then apply four stacked single-atom-thick graphene layers using a wet transfer technique. These layers were then protected with a silicon dioxide layer, another parylene layer, and finally molded into brain signal recording goodness with reactive ion etching.

PennTransparentelectrodeThe researchers went with four graphene layers because that provided optimal mechanical integrity and conductivity while maintaining sufficient transparency. They tested the device in opto-enhanced mice whose neurons expressed proteins that react to blue light. When they hit the neurons with a laser fired in through the implant, the protein channels opened and fired the cell beneath. The masterstroke that remained was then to successfully record the electrical signals from this firing, sit back, and wait for the Nobel prize office to call.

Read: MIT successfully implants false memories with optogenetics, may explain why we remember things that didn’t happen

The Penn State group used a similar 16-spot electrode array (pictured above right), and proceeded — we presume — in much the same fashion. Their angle was to perform high-resolution optical imaging, in particular calcium imaging, right out through the transparent electrode arrays which simultaneously recorded in high-temporal-resolution signals. They did this in slices of the hippocampus where they could bring to bear the complex and multifarious hardware needed to perform confocal and two-photon microscopy.

These latter techniques provide a boost in spatial resolution by zeroing in over narrow planes inside the specimen, and limiting the background by the requirement of two photons to generate an optical signal. We should mention that there are voltage sensitive dyes available, in addition to standard calcium dyes, which can almost record the fastest single spikes, but electrical recording still reigns supreme for speed.

What a mouse looks like with an optogenetics system plugged in

One concern of both groups in making these kinds of simultaneous electro-optic measurements was the generation of light-induced artifacts in the electrical recordings. This potential complication, called the Becqueral photovoltaic effect, has been known to exist since it was first demonstrated back in 1839.

When light hits a conventional metal electrode, a photoelectrochemical (or more simply, a photovoltaic) effect occurs. If present in these recordings, the different signals could be highly disambiguatable. The Penn researchers reported that they saw no significant artifact, while the Wisconsin researchers saw some small effects with their device. In particular, when compared with platinum electrodes put into the opposite side cortical hemisphere, the Wisconsin researchers found that the artifact from graphene was similar to that obtained from platinum electrodes.

At this point both groups are busy characterizing the performance of their new devices in exacting detail. If workable as more permanent brain implants they may offer a nice compliment to other new approaches we have recently seen — flexible materials like silk for example. Where silk may offer biodegradability and reversibility, graphene may offer biocompatible permanence and reliability. The significant hype regarding optogenetics, well-founded in our opinion, seems to have died down for the moment. New advances like those just described may help refocus general attention on the huge potential benefit optogenetics holds for humans.

Now read: The wonderful world of wonder materials (such as graphene)