Technical / Research

NTT Corporation and the National Institute for Materials Science (NIMS) have jointly reported the realization of what they define as "the world's fastest zero-bias operation (220 GHz) of a graphene photodetector (PD)". The research conducted by NTT and NIMS has also, according to the statement, clarified the optical-to-electrical (O-E) conversion process in graphene for the first time.

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Graphene is a promising photodetection material for enabling high-speed O-E conversion at wavelength ranges where existing semiconductor devices cannot operate, thanks to its high sensitivity and high-speed electrical response to a wide range of electromagnetic waves, from terahertz (THz) to ultraviolet (UV). However, until now, the demonstrated zero-bias operating speed has been limited to 70 GHz due to conventional device structure and measurement equipment. For this reason, the challenge for graphene PDs is to demonstrate 200-GHz operation speeds and clarify graphene's inherent properties, such the process of optical-to-electrical conversion.

Researchers from the UK's Imperial College London have developed graphene-based flexible clothing sensors that can detect body movement, with potential applications in injury rehabilitation, human-computer interaction systems, and athletic training. 

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The researchers produced a new type of graphene-based TPU/textile composite sensor using small-scale manufacturing techniques such as laser cutting, film coating, and thermal transfer.    

Ni-Co layered double hydroxides (LDH) are seen as promising materials for pseudocapacitor electrodes. Researchers from Chonnam National University and Korea Institute of Science and Technology (KIST) recently conducted a study that focused on the use of graphene oxide (GO) and single-walled carbon nanohorns (SWCNHs) hybrid as an efficient platform for LDH coating materials for supercapacitor electrodes.

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The team explained that the novel Ni-Co LDH and GO/SWCNHs composite-based supercapacitor electrode material could be a potential choice for pseudocapacitor applications thanks to its superior electrochemical properties and ease of production, which is ideal for various commercial and industrial applications.

Researchers from the National Institute for Cryogenics and Isotopic Technologies ICSI-Rm in Romania have applied microwave processes to iodine doping and reduction of graphene oxide, to produce functionalized fuel cell organic reduction reaction electrocatalysts. The team chose to utilize microwave-assisted processes because of their many benefits, like reduced energy, time, and cost demands.

The process developed by the team relies on a faster, simpler, more economical, and efficient protocol under atmospheric pressure conditions. Under mild conditions, the microwave-assisted process highlighted in the research synthesizes a canvas-like iodine/reduced graphene oxide structure from graphene oxide. Thus, a low-cost, efficient alternative to platinum-based catalysts has been developed.

Researchers at University of California, Berkeley (UC Berkeley), the Kavli Energy Nanosciences Institute, Beijing Institute of Technology, Shenzhen University and Tsinghua University recently developed a tunable and reversible approach, based on laser-assisted chlorination, to chemically dope graphene. 

Many different chemical doping techniques were devised in order to control the sign and concentration of charge carriers in different material samples. Chemical doping methods essentially entail introducing impurities into materials or substances to change their electrical properties. These methods have been successfully applied on several materials including van der Waals (vdW) materials. VdW materials are structures characterized by strongly bonded 2D layers, which are bound in the third dimension through weaker dispersion forces.

Scientists from Vanderbilt University recently developed a lightweight and ultra-compact graphene-based filter that can block aerosolized nanoparticles of size in the sub-20 nm range. 

Nanoparticulate aerosols contain toxins, pollutants, and harmful viruses, whose size varies between 20 and 300 nm in diameter. Although conventional air filters, such as 95% efficiency filter (N95) and the high-efficiency particulate air filter (HEPA), exhibit superior air flow rates, they are unable to inhibit nanoparticulate aerosols whose size is less than 300 nm. Facemasks that can block nanoparticulate aerosols of size below 300 nm are bulky and develop thermal stress due to low breathability. To improve the applicability of PPEs, several strategies are implemented that focus on making porous polymers, with greater thickness, which can filter out nanoparticulate aerosol toxins, pathogens, and pollutants.

Researchers from India's Haldia Institute of Technology have created a gravity filter using graphene oxide (GO), meant for purifying river water. Using alternative water resources like river water can help address the rising shortage of freshwater resources worldwide. Therefore, the deployment of cost-effective water filtration technologies is imperative for the desalination of river water and purification of polluted water.

Filtration using a gravity filter is a highly popular method for water purification. A gravity filter is a type of pressure filter wherein water passes through the filtering component on the influent side at atmospheric pressure and the whole system is driven by the force of gravity instead of electricity. A major benefit of gravity filters is that they are free from moving components, therefore require less filter maintenance. Another significant advantage of using a gravity-based water filtration system is that the system does not need a power supply. The main drawback, on the other hand, is the low output of purified water. The limitations of filtering technology imply that no one filtration material can remove all pollutants present in water.

Researchers from Brown University, the University of New South Wales, Columbia University, University of Innsbruck, and the National Institute for Materials Science in Japan have carried out new experiments involving trilayer graphene, in which an external magnetic field is not required in order to achieve the 'superconducting diode effect' - a material that behaves like a superconductor in one direction of current flow and like a resistor in the other.

In contrast to a conventional diode, such a superconducting diode exhibits a completely vanishing resistance and thus no losses in the forward direction. This could form the basis for future lossless quantum electronics. Physicists have already succeeded in creating the diode effect, but with some fundamental limitations. "At that time, the effect was very weak and it was generated by an external magnetic field, which is very disadvantageous in potential technological applications," explains Mathias Scheurer from the Institute of Theoretical Physics at the University of Innsbruck. The new experiments confirmed a thesis previously theorized by Scheurer: Namely, that superconductivity and magnetism coexist in a system consisting of three graphene layers twisted against each other. The system thus virtually generates its own internal magnetic field, creating a diode effect.

Scientists from The University of Manchester, Tsinghua University in China and the Chinese Academy of Sciences (CAS) recently reported that graphene can facilitate gold extraction from waste containing only trace amounts of gold (down to billionth of a percent).

This surprising application of graphene was described to work quite straightforwardly: add graphene into a solution containing traces of gold and, after a few minutes, pure gold appears on graphene sheets, with no other chemicals or energy input involved. After this you can extract your pure gold by simply burning the graphene off. The research shows that 1 gram of graphene can be sufficient for extracting nearly 2 grams of gold.

Graphene Manufacturing Group (GMG) has announced that it has signed a binding agreement with OzKem for GMG to acquire the manufacturing intellectual property and brand rights of OzKem's THERMAL-XR® coating products.

OzKem is a coatings technology company which developed the THERMAL-XR® coating system products using GMG graphene together with OzKem's base HVAC (Heating Venting and Air Conditioning) coating. GMG is an international distributor of THERMAL-XR® products with a number of global commercial demonstrations underway or initial sales completed. Following the completion of the agreement GMG will own the THERMAL-XR® brand, will buy the base coatings product from OzKem, and GMG will manufacture the THERMAL-XR® products containing GMG graphene.