MIT - Page 8

Researchers at the Massachusetts Institute of Technology and Harvard Medical School studied the extent to which graphene oxide is biocompatible, and discovered that it is not toxic to cells (up to a certain concentration). Graphene oxide may thus be suitable for use in medical devices and implants for next-generation biosensors, implantable electronics or even tissue engineering scaffolds.

In their tests, the scientists found that reducing the degree of graphene oxidation resulted in the material infiltrating and clearing cells faster. They also observed that after injection, the graphene oxide particles coalesced to form an implant-like material in the tested mice. The scientists' study showed that over the short term, the body responds to graphene oxide in much the same way it does to other biomaterial implants that are known to be safe.

Researchers from the ICFO, ICREA, MIT and UC Riverside, have now showed that a graphene-based photodetector converts absorbed light into an electrical voltage at an extremely high speed. The efficient conversion of light into electricity is crucial to various technologies, from cameras to solar cells. It can also play a part in data communication applications, since it allows information to be carried by light and converted into electrical information that can be processed in electrical circuits.

Graphene is known to be an excellent material for conversion of light to electrical signals, but it was unknown exactly how fast graphene responds to ultrashort flashes of light. The researchers developed a device capable of converting light into electricity in less than 50 femtoseconds (a twentieth of a millionth of a millionth of a second). Facilitated by graphene's nonlinear photo-thermoelectric response, the observation of femtosecond photodetection response times was enabled.

A simple way of cleaning water of various contaminants (from lead and mercury to dye and antibiotics) was shown in a proof-of-concept study at Monash University (that also involved MIT and Bristol University), using graphene oxide and magnets.

The method relies on strong magnets that draw charged particles out of water as it flows through a pipe. The particles are attached to tiny sheets of graphene oxide, which attract a huge range of toxins. Graphene oxide's ability to sponge metal ions made the new system a promising way of treating mine tailing dams.

Scientists from ICFO, MIT, CNRS, CNISM and Graphenea collaborated to demonstrate how graphene can enable the electrical control of light at the nanometer level. Electrically controlled modulation of light emission is crucial in applications like sensors, displays and various optical communication system. It also opens the door to nanophotonics and plasmonics-based devices. 

The researchers managed to show that the energy flow from erbium into photons or plasmons can be controlled by applying a small electrical voltage. The plasmons in graphene are unique, as they are very strongly confined, with a plasmon wavelength that is much smaller than the wavelength of the emitted photons. As the Fermi energy of the graphene sheet was gradually increased, the erbium emitters went from exciting electrons in the graphene sheet, to emitting photons or plasmons. The experiments showed the graphene plasmons at near-infrared frequencies, which may be beneficial for communications applications. In addition, the strong concentration of optical energy offers new possibilities for data storage and manipulation through active plasmonic networks.

Researchers at MIT and Harvard University found a way to use folded DNA to control the nanostructure of inorganic materials. DNA structures are built in a certain shape, then used as templates to create nanoscale patterns on sheets of graphene. This technique can further large-scale production of graphene electronic chips.

This technique forms DNA nanostructures with precisely planned shapes using short synthetic DNA strands called single-stranded tiles. Each of these tiles acts as an interlocking brick and binds with four designated neighbors. The researchers transferred the structural information encoded in DNA to graphene, using a relatively simple process that includes anchoring the DNA onto a graphene surface using a molecule called aminopyrine, which is similar in structure to graphene. The DNA is then coated with small clusters of silver along the surface, which allows a subsequent layer of gold to be deposited on top of the silver.

Graphenea has opened a branch in the USA to assist more immediate service of the company's North American customers. The US branch, Graphenea Inc, is based in Cambridge (Boston), MA, due to the close relation that the company has with research giants Massachusetts Institute of Technology (MIT) and Harvard. Apart from developing collaborative projects with those two partners, and acting as a sales outpost for its renown high-quality graphene, Graphenea Inc will set up an Applications Laboratory to help develop custom graphene materials.

The US outpost of Graphenea will continue and enhance the research excellence of the company, with planned hirings of full time R&D and Business Development personnel, says Jesus de la Fuente, CEO of Graphenea. The most pronounced application directions that we will pursue will be advanced polymers, thermal interface materials, energy storage, and (bio)sensors.

MIT researchers discovered that crumpling graphene paper (made from graphene sheets bonded together) results in a low-cost material that is very useful for extremely stretchable supercapacitors for flexible devices.

Crumpling the graphene paper results in a "chaotic mass of folds. The researchers developed a simple supercapacitor using this material, that can easily be bent, folded, or stretched to as much as 800% of its original size. The material can be crumpled and flattened up to a 1,000 times, without a significant loss of performance.

Researchers from the UK's University of Southampton developed a new process to synthesize large-area molybdenum di-sulphide (MoS₂), a 2D material similar to graphene in many of its properties. Up until now most MoS₂ production results in tiny flakes.

The researchers used atmospheric pressure chemical vapor deposition (APCVD) to fabricate large area (>1000 mm²) ultra- thin films only a few atoms thick. The researchers are collaborating in this research together with several UK companies and universities, MIT and Singapore's Nanyang Technological University.

Manchester University's graphene Nobel laureate Sir Andre Geim, together with Leonid Levitov from MIT discovered that electrons in a graphene superlattice move at a controllable angle to applied fields - this is like sailboats that sail diagonally to the wind.

A graphene superlattice is made from a sheet of graphene aligned on top of a sheet of boron nitride. This material behave as a semiconductor (unlike graphene itself which is a superconductor). The researchers found that the electrons in the new material behave as neutrinos that acquired a notable mass. This effect has no known analog in particle physics.

Researchers from MIT developed a flexible transparent graphene-based electrode for graphene polymer solar cells (PSC). They report that this is the most efficient such electrode ever developed, with power conversion efficiencies of 6.1% (anode) and 7.1% (cathode).

To achieve the record efficiencies, the researchers thermally treated the MoO3 electron blocking layer and directly deposited a ZnO electron transporting layer on the graphene. The researchers say that the process is simple and reproducible.