Technical / Research - Page 3

In 2015, scientists at James Cook University in Queensland, Australia, and collaborators from institutions in Australia, Singapore, Japan, and the US developed a technique for growing graphene from tea tree extract. Now, scientists from James Cook University developed a process to synthesize graphene from tangerine peel oil, which they then used to recover silver from waste PV material. To demonstrate the quality of the recovered silver and the synthesized graphene, they made a dopamine sensor that reportedly outperformed reference devices.

The team synthesized “freestanding” graphene using non-toxic and renewable tangerine peel oil that can reportedly be used for the recovery of silver from end-of-life organic PV devices. The researchers said that their process result in high-quality graphene and demonstrated a remarkable ability to selectively recover silver from photovoltaic waste. One of the most surprising findings, according to the team, was how selective the graphene was in targeting silver.

Researchers have used a specially crafted electric potential to manipulate the electronic band structure of graphene, laying the groundwork for on-demand electronic band design. 

Scientists have long been trying to tune the electronic band structures of materials so that those materials exhibit desired physical properties. In the past few years, researchers have shown they can manipulate the band structures of graphene and other 2D materials using electric-field configurations that produce simple periodic potentials. Now, Changgan Zeng at the University of Science and Technology of China and his colleagues have shown that they can achieve greater control over the band structure using an electric potential with a shape that resembles a basket-weaving pattern known as kagome.

Researchers from the Czech Republic's Palacký University’s CATRIN, the University of West Bohemia, and VSB-TUO have developed an innovative sensor capable of accurately measuring temperatures between 10 and 90 degrees Celsius. This novel sensor, based on a novel graphene derivative, stands out for its high precision, reliability, and resistance to humidity. Its applications range from industrial production and storage areas requiring remote temperature monitoring to integration into protective clothing.

“We developed the new material using fluorographene chemistry by removing fluorine atoms and attaching benzylamine to the available reactive sites. This proved to be a crucial step in creating the temperature sensor. This technology allowed us to significantly minimize the adverse effects of humidity, typically the most challenging issue for such devices,” explained Petr Jakubec from CATRIN, a co-author of the study published in the prestigious journal Advanced Electronic Materials.

NTT Corporation, along with The University of Tokyo and National Institute for Materials Science (NIMS), showed that graphene plasmon wave packets can be generated, manipulated and read out on-chip using terahertz electronics.  

The team managed to electrically generate and control graphene plasmon wave packets with a pulse width of 1.2 picoseconds. This result shows that the phase and amplitude of a terahertz signal can be controlled electrically by using graphene plasmons. It enables terahertz signal processing, a method different from conventional electrical circuit technology using transistors and is expected to contribute to realizing ultrahigh-speed signal processing in the future.

Researchers from the University of North Carolina at Chapel Hill, Carnegie Mellon University, North Carolina State University and Yale University have developed a novel method to enhance the efficiency and stability of solar-driven, carbon-dioxide reduction.

Image credit: Applied Materials and Interfaces

This new technique involves the use of “fuzzy” graphene to improve the performance of semiconductor-based photoelectrodes, which initialize electrochemical transformations following the absorption of light. The term fuzzy refers to a form of graphene that has a rough or irregular surface with a porous and three-dimensional (3D) structure, as opposed to smooth or flat layers, with enhanced properties like surface area, reactivity or adhesion to a silicon molecule, or substrate.

Limb neuroprostheses aim to restore motor and sensory functions in amputated or severely nerve-injured patients. These devices use neural interfaces to record and stimulate nerve action potentials, creating a bidirectional connection with the nervous system. Most neural interfaces are based on standard metal microelectrodes. 

Left: a histological section of the nerve implanted with an electrode longitudinally. Right, an image of the sciatic nerve with an EGNITE electrode implanted transversely to allow stimulation and recording of nerve impulses. Image credit: UAB

Researchers at the Autonomous University of Barcelona (UAB) and ICN2 have demonstrated in animal models how Engineered Graphene for Neural Interface (EGNITE), a derivative of graphene, allows the creation of smaller electrodes, which can interact more selectively with the nerves they stimulate, thus improving the efficacy of the prostheses. The study also demonstrated that EGNITE is biocompatible, showing that its implantation is safe.

Researchers at École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland and National Institute for Materials Science in Japan have combined the electrical properties of graphene with the semiconducting characteristics of indium selenide in a field-effect geometry, to create a device that can efficiently convert heat into electrical voltage at temperatures lower than that of outer space. The innovation could help overcome a significant obstacle to the advancement of quantum computing technologies, which require extremely low temperatures to function optimally.

Device schematic representing a fully encapsulated few-layer InSe channel, with graphene electrodes. Image credit: Nature Nanotechnology

To perform quantum computations, quantum bits (qubits) must be cooled down to temperatures in the millikelvin range (close to -273 Celsius), to slow down atomic motion and minimize noise. However, the electronics used to manage these quantum circuits generate heat, which is difficult to remove at such low temperatures. Most current technologies must therefore separate quantum circuits from their electronic components, causing noise and inefficiencies that hinder the realization of larger quantum systems beyond the lab. Now, researchers in EPFL’s Laboratory of Nanoscale Electronics and Structures (LANES), led by Andras Kis, have fabricated a device that not only operates at extremely low temperatures, but does so with efficiency comparable to current technologies at room temperature.

Professors Gil-Ho Lee and Gil Young Cho from Pohang University of Science and Technology (POSTECH) in South Korea have collaborated with Dr. Kenji Watanabe and Dr. Takashi Taniguchi from National Institute for Materials Science (NIMS) in Japan to successfully control the quantum mechanical properties of Andreev bound states in bilayer graphene-based Josephson junctions using gate voltage. 

Superconductors exhibit zero electrical resistance under specific conditions such as extremely low temperatures or high pressures. When a very thin normal conductor is placed between two superconductors, a supercurrent flows through it due to the proximity effect where superconductivity extends into the normal conductor. This device is known as a Josephson junction. Within the normal conductor, new quantum states called Andreev bound states are formed, which are crucial for mediating the supercurrent flow.

Researchers at the University of Antwerp and CIC biomaGUNE have reported a novel method based on graphene, for understanding the role of surface molecules in the formation of nanoparticles. The research provides an advanced characterization tool for the design of nanomaterials.

Gold nanoparticles have been the subject of intense research for several decades due to their interesting applications in fields such as catalysis and medicine. "Surface ligands" are organic molecules typically present on the surface of gold nanoparticles. During synthesis, these surface ligands play an important role in controlling the size and shape of the nanoparticles. For several decades, the CIC biomaGUNE team led by Ikerbasque Research Professor Luis Liz-Marzán has studied the growth mechanisms and properties of these nanoparticles. However, many questions remain about the exact behavior of surface ligands during and after growth. Direct observation of surface ligands and their interface with gold nanoparticles has therefore been a long-standing goal for many scientists in this field.

Researchers from the University of Michigan, SLAC National Accelerator Laboratory, Carnegie Mellon University and Harvard University have shown that three layers of graphene, in a twisted stack, benefit from a similar high conductivity to "magic angle" bilayer graphene but with easier manufacturing—and faster electron transfer. The findings could improve nano electrochemical devices or electrocatalysts to advance energy storage or conversion.

Twisting two sheets of graphene at a 1.1° angle, dubbed the "magic angle," creates a "flat band" structure, meaning the electrons across a range of momentum values all have roughly the same energy. Because of this, there is a huge peak in the density of states, or the available energy levels for electrons to occupy, at the energy level of the flat band which enhances electrical conductivity. Recent work experimentally confirmed these flat bands can be harnessed to increase the charge transfer reactivity of twisted bilayer graphene when paired with an appropriate redox couple—a paired set of chemicals often used in energy storage to shuttle electrons between battery electrodes. Adding an additional layer of graphene to make twisted trilayer graphene yielded a faster electron transfer compared to bilayer graphene, according to the team's recent study, that created an electrochemical activity model.