Graphene "cages" may open the door to silicon Li-ion battery anodes

A team of scientists at Stanford University and the Department of Energy's SLAC National Accelerator Laboratory has come up with a possible answer to the question of how to make lithium-ion battery anodes out of silicon, as these tend to swell and crack, as well as react with the battery electrolyte to form a coating that harms their performance.

The scientists wrapped each silicon anode particle in a custom-fit "cage" made of graphene, in a simple, three-step method for building microscopic graphene cages of just the right size: roomy enough to let the silicon particle expand as the battery charges, yet tight enough to hold all the pieces together when the particle falls apart, so it can continue to function at high capacity. The strong, flexible cages also block destructive chemical reactions with the electrolyte.

Read the full story Posted: Jan 29,2016

Graphene-enhanced film shuts down li-ion batteries before overheating and restarts upon cooling

Researchers at Stanford University have developed a revolutionary graphene-enhanced polyethylene film that prevents a lithium-ion battery from overheating, then restarts the battery when it cools. This new technology could prevent fires and melt-downs in a wide range of battery-powered devices.

The researchers in this study recently invented a wearable sensor to monitor human body temperature, made of a plastic material embedded with tiny particles of nickel with nanoscale spikes protruding from their surface. For the battery experiment, they coated the spiky nickel particles with graphene and embedded the particles in a thin film of elastic polyethylene. They then attached the film to one of the battery electrodes so that an electric current could flow through it. The researchers explain that in order to conduct electricity, the spiky particles have to physically touch one another, but during thermal expansion, polyethylene stretches. That causes the particles to spread apart, making the film non-conductive so that electricity can no longer flow through the battery.

Read the full story Posted: Jan 12,2016

Graphene may enable dense, energy-efficient memory chips

Researchers at Stanford University have recently performed three separate experiments that suggest graphene in computing and telecommunications could radically cut energy consumption. This work was done in search of post-silicon materials and technologies that enable storing more data per square inch and use a fraction of the energy of currently used memory chips.

All three experiments involve graphene, and test different ways to use it in new storage technologies. The scientists claim that graphene can have interesting mobile applications of these new technologies, but post-silicon memory chips may transform server farms that store and deliver quick access to enormous quantities of data stored in the cloud.

Read the full story Posted: Oct 28,2015

Nanomedical Diagnostics announces raise of $1.6 million in Series A funding

Nanomedical Diagnostics, which declared the commercialization of a graphene biosensor in September 2015, announced the completion of a Series A financing round of $1.6 million. The funding round will enable the company to commercially release AGILE Research, its new label-free, quantitative, affordable research tool for small molecule and protein analysis. The company is also using the funds to lay the foundation for AGILE Lyme investigational product evaluation and market clearance.

Nanomedical Diagnostics states that it has achieved excellent progress in only 20 months, and that its current focus is finalizing AGILE Research product design. The company will be evaluating its performance with the CDC and Stanford University this fall and expects to launch the product early next year for commercial use to study proteins of interest.

Read the full story Posted: Oct 14,2015

Nanomedical Diagnostics declares commercialization of graphene biosensor

Nanomedical Diagnostics logoNanomedical Diagnostics, a U.S-based biotech company developing and commercializing bioelectronics for use in research and diagnostics, launched its first product, AGILE Research, a label-free, quantitative, low-cost biosensor for small molecule and protein analysis. The product is entering beta testing this fall and planned for commercial release in early 2016.

AGILE Research is based on graphene biological field effect transistor (BioFET) technology. Its vision is enabling personalized healthcare by improving diagnostic ease, speed, and cost through cutting-edge capabilities. Nanomed’s current focus is finalizing AGILE Research product design and will be evaluating its performance with the Centers for Disease Control and Prevention (CDC) and Stanford University. The CDC and Nanomedical Diagnostics are entering into a Cooperative Research and Development Agreement to evaluate direct electronic detection of Borrelia burgdorferi antigens for a new Lyme disease diagnostic system. Lyme disease research is also a focal point in the Stanford beta test.

Read the full story Posted: Sep 20,2015

Graphene combined with phosphorene might give a boost to sodium ion batteries

Researchers at Stanford University in California have developed a new material comprising interspersed layers of graphene and phosphorene that has been shown to be a more stable, more conductive and higher capacity anode for sodium ion batteries than previous materials. The researchers believe it could be industrially compatible, and potentially allow sodium ion batteries to become useful for large-scale energy storage.

The graphene layers provide an elastic buffer and function as an electrical highway, allowing charge to get in and out faster. The phosphorene and graphene were both produced by scalable liquid exfoliation, and the sandwich structure self-assembled when suspensions of the two components were mixed and the solvent was evaporated.

Read the full story Posted: Sep 09,2015

Will Stanene become graphene's rival in terms of electrical conductivity?

A collaboration between researchers at Stanford University and four universities in China yielded a material made of a single layer of tin atoms, that could be the world's first material to conduct electricity with 100% efficiency at room temperature. The material, called Stanene, is believed to be a rival to graphene and other two-dimensional materials like phosphorene, silicene or germanene, because it is believed to be so conductive as to allow flow of electricity without any heat loss.

The scientists created the mesh by vaporising tin in a vacuum and allowing the atoms to collect on a supporting surface of bismuth telluride. As a result, a two-dimensional honeycomb structure of tin atoms was made. Alas, the substrate and stanene interacted to disrupt the conditions that would have created the perfect conductor - so the team plans to use larger amounts of tin and an inert substrate to rule out interaction. In fact, not all researchers are even sure that the structure created at Stanford is indeed stanene. Direct measurements of the crystal arrangements only can confirm this but that will call for larger amounts of the material.

Read the full story Posted: Aug 05,2015

Wrapping graphene around wires may boost chip speeds

A series of Stanford-led experiments demonstrate that graphene may be able to replace tantalum nitride as a sheathing material for chip wires, to help electrons move through the copper wires more quickly. The scientists say that using graphene to wrap wires could allow transistors to exchange data faster than is currently possible and the advantages of using graphene could become even greater in the future, as transistors continue to reduce in size.

The protective layer isolates the copper from the silicon on the chip and also serves to conduct electricity. Its significance is great since it keeps the copper from migrating into the silicon transistors and rendering them non-functional. Graphene has several advantages for this kind of application: the scientists could use a layer eight times thinner than the industry-standard and get the same effect, and the graphene also acts as a barrier to prevent copper atoms from infiltrating the silicon. The Stanford experiment showed that graphene could perform this isolating role while also serving as an auxiliary conductor of electrons. Its structure allows electrons to move from one carbon atom to another, down the wire, while effectively containing the copper atoms within the copper wire. 

Read the full story Posted: Jun 18,2015

Graphene as a substrate for assembling small organic molecules and heterostructures

Researchers at the University of Stanford in the US, the Ulsan National Institute of Science and Technology (UNIST) in South Korea and Queen’s University in the UK showed that graphene is an excellent substrate for assembling small organic molecules and that such heterostructures might be used in applications like high-performance detectors, solar cells and flexible transistors.

The researchers began by preparing suspended graphene films. They then evaporated C60 molecules onto the films to form thin-film crystals.They then made the resulting structures up into vertical transistors doped with n-type semiconducting materials and found that these devices have current on/off ratios of more than 3 x 103. Various transmission electron microscopy techniques, including selective area electron diffraction, atomic resolution TEM imaging, and van der Waals-based first principles computational methods allowed the researchers to study the structure and grain size of the crystals in detail and carefully look at the graphene-C60 interface in particular. They also noticed that the C60 films lay uniformly on the graphene substrate and that the individual molecules can assume several different molecular orientations.

Read the full story Posted: Jun 17,2015

Spiraling laser pulses find graphene's on/off switch

Scientists from the Department of Energy’s SLAC National Accelerator Laboratory and the Stanford Institute for Materials and Energy Sciences (SIMES) collaborated to study the effects of spiraling pulses of laser light on graphene. They discovered that such spiraling laser pulses can theoretically change the electronic properties of graphene, switching it back and forth from a metallic state (where electrons flow freely), to an insulating state.

Such ability could mean that it is possible to use light to encode information in a computer memory, for instance. The study, while theoretical, attempted to work in as close-to-real experimental conditions as possible, right down to the shape of the laser pulses. The team found that the laser's interaction with graphene yielded surprising results, producing a band gap and also inducing a quantum state in which the graphene has a so-called “Chern number” of either one or zero, which results from a phenomenon known as Berry curvature and offers another on/off state that scientists might be able to exploit.

Read the full story Posted: May 28,2015