Researchers from Iran have devised a process to produce graphene by using laser ablation in cold liquid media. They say this process enable a simple and effective control of the resulting graphene sheet.
The researchers say that this process is suited for mass production. They are using a pulsed nanosecond Nd:YAG laser (Nd:Y3Al5O12) in liquid nitrogen. The nitrogen has fast flow circulation.
Researchers from the Rensselaer Polytechnic Institute have developed a new graphene based anode that can be charged or discharged 10 times faster than conventional graphite anodes currently used in today’s lithium-ion batteries. To create the new anode material, the researchers took a sheet of graphene-oxide paper and then introduced defects (using a laser or a camera flash) on the material.
The graphene paper, after being damaged, has expanded five-fold in thickness, which means that there were large voids between the graphene sheets. The lithium ions can use the cracks in the paper to quickly traverse the entire sheet - which means faster charges or discharges of the battery.
Researchers from Columbia and Singapore discovered that graphene has a remarkable optical nonlinear behavior - which could lead to ultra low power photonic integrated circuits. The researchers managed to use a single sheet of graphene and silicon to generate microwave photonic signals and perform parametric wavelength conversion at telecommunication wavelengths.
The researchers say that by optically driving the electronic and thermal response in the hybrid silicon-graphene chip they could generate a RF carrier on top of the transmitted laser beam and control its modulation with the laser intensity and color. The resonant quality of this cheap is 50 times lower than the best pure-silicon chip.
Researchers from the University of California have used a beam of infrared light to send ripples of electrons along the surface of graphene. The length of heights of the plasmons oscillations can be controlled using a simple electrical circuit.
It was already suspected that plasmons will be present on graphene, but this is the first real demonstration. The actual device used is a sheet of graphene on a silicon dioxide chip.
Researchers from the Iowa State University discovered that Graphene behaves like a laser when excited with very short femtosecond light pulses. Graphene has been shown to have two technologically important properties population inversion of electrons and optical gain. This means that Graphene can be used to make a variety of optoelectronics devices, including broadband optical amplifiers, high-speed modulators, and absorbers for telecommunications and ultra fast lasers.
We already heard of some infra-red graphene related research: Infrared detection using graphene nanoribbons and a graphene-based technology for use in low-cost infrared imaging applications for the US military.
Update: Check out this short video explaining this new research and showing the people behind it, and the next-gen technique unveiled in February 2013
A team of researchers from the UCLA managed to developed laser-scribed graphene (LSG) based flexible capacitors using simple DVD burners. The idea is to deposit Graphite Oxide on blank DVDs and then use a DVD burner (a light scribe drive) which uses a 780nm infrared laser. The laser reduces the Graphite Oxide to pure graphene (LSG). This LSG is placed on flexible substrates which are used as the electrodes for a super capacitor.
This is not just a gimmick process - it will be possible to scale it for commercial production, and these capacitors are fast (20 times faster than standard carbon capacitors and 3 times faster than lithium-ion batteries) and offer good density (twice than that of carbon capacitors and comparable to a high-power lithium-ion battery).
It's been known for a long time that Graphene generates current from light. Up until now everybody assumed it was due to the photovoltaic effect, but a new research by MIT researchers shows that this is not true. They found that light on graphene causes it to develop two regions with different electrical properties which creates a temperature difference.
This "hot-carrier response" is what generates the current - and it's very unusual - it's been observed before but only under very low temperature or when using intense high power laser. The reason for this unusual thermal response is that graphene is the strongest material known. In most materials, superheated electrons would transfer energy to the lattice around them. In the case of graphene, however, that’s exceedingly hard to do, since the material’s strength means it takes very high energy to vibrate its lattice of carbon nuclei â so very little of the electrons’ heat is transferred to that lattice.
Foa Torres, a scientist from the National University of Córdoba in Argentina, says that Graphene's Achilles heel is the fact that it does not have a band gap. This means that Graphene cannot be 'turned-off', and so you can't use it for active electronic devices such as switches and transistors.
Foa Torres predicts that shining a mid-infrared laser on graphene can produce band gaps in its electronic structure, and this band gap could be tuned by controlling the laser polarization. The next crucial step is experimental verification.
Researchers from the Korea Advanced Institute of Science and Technology (KAIST) say that Graphene can be used to create bendable batteries. The researchers developed a graphene-based hybrid electrode and produced a flexible lithium rechargeable battery. The cathode material (V2O5) was grown on a graphene sheet using pulsed laser reposition and the anode was lithium-coated graphene.
This battery actually has promising performance compared to non-flexible batteries - higher energy density, power density and better cycle life. The team now works on extending the performance using solid-state or polymer electrolyte. They also believe that this technology can be used not just in batteries but also in solar cells, OLED displays and catalysis.
Researchers from Cambridge (UK) and CNRS (France) have developed an ultra-fast mode-locked laser using Graphene. Graphene based lasers can be easier and cheaper to make than semiconductor saturable absorber mirrors (SESAMs) based lasers, and will be less limited in their bandwidth.
Graphene ultra-fast laser
The team studied how light is absorbed in graphene and how photo-excited charge carriers behave in the material. In particular, they highlighted the key role of "Pauli blocking" in saturating the light absorption. Because of the Pauli exclusion principle, when pumping of electrons in the excited state is quicker than the rate at which they relax, the absorption saturates. This is because no more electrons can be excited until there is "space" available for them in the excited state.