Researchers from Germany's Max Planck Institute for Polymer Research and China's Southeast University have reported a graphene-based aqueous memristive device with long-term and tunable memory, regulated by reversible voltage-induced interfacial acid-base equilibria enabled by selective proton permeation through the graphene. 

Memristive devices, electrical elements whose resistance depends on the history of applied electrical signals, are leading candidates for future data storage and neuromorphic computing. Memristive devices typically rely on solid-state technology, while aqueous memristive devices are crucial for biology-related applications such as next-generation brain-machine interfaces. Recently, nanofluidic devices have been reported in which solvated ion transport exhibits memristive behavior. The challenge associated with these approaches is the complexity of the device fabrication. Realizing memristive behavior in a simple system is highly desirable.

Scientists at the University of California San Diego have developed an ultra-sensitive graphene-based sensor that can detect extraordinarily low concentrations of lead ions in water. The device achieved a record limit of detection of lead down to the femtomolar range, which is said to be a million times more sensitive than previous sensing technologies.

The device in this study consisted of a single layer of graphene mounted on a silicon wafer. The researchers enhanced the sensing capabilities of the graphene layer by attaching a linker molecule to its surface. This linker serves as the anchor for an ion receptor and, ultimately, the lead ions.

Rice University researchers have mapped out how bits of 2D materials move in liquid ⎯ which that could help scientists assemble macroscopic-scale materials with the same useful properties as their 2D counterparts.

In order to maintain these special properties in bulk form, sheets of 2D materials have to be properly aligned ⎯ a process that often occurs in solution phase. The Rice team focused on graphene and hexagonal boron nitride, a material with a similar structure to graphene but composed of boron and nitrogen atoms.

Researchers from North Carolina State University and Pacific Northwest National Laboratory (PNNL) recently used shear assisted processing and extrusion (ShAPE) to synthesize macro-scale copper-graphene composites with a simultaneously lower temperature coefficient of resistance (TCR) and improved electrical conductivity over copper-only samples. 

The team's new graphene-copper composite with an improved ability to conduct electricity could lead to more efficient electricity distribution to homes and businesses, as well as more efficient motors to power electric vehicles and industrial equipment. The team has applied for a patent for the work, which was supported by the Department of Energy (DOE) Advanced Materials and Manufacturing Technologies Office.

Rice University researchers have found that graphene derived from metallurgical coke, a coal-based product, could serve not only as a reinforcing additive in cement but also as a replacement for sand in concrete.

"This could have a major impact on one of the biggest industries in the world," said James Tour, Rice's T. T. and W. F. Chao Professor and a professor of chemistry, materials science and nanoengineering. "We compared concrete made using the graphene aggregate substitute with concrete made using suitable sand aggregates, and we found our concrete is 25% lighter but just as tough."

Universidad Politécnica de Madrid researchers have reported the development of an electrically tunable graphene-based biosensor that leverages sound waves to provide unprecedented infrared sensitivity and specificity at the single layer limit. By precisely matching the tunable graphene plasmon frequency to target molecular vibrations, even faint spectral fingerprints emerge clearly.

This acoustically activated approach enables precise in situ study of angstrom-scale films, unlocking new infrared applications across chemistry, biology and medicine.

Researchers at the UK's University of Leicester, Russia's Skolkovo Institute of Science and Technology and Kemerovo State University, TerraVox Global in Cyprus, National University of Singapore and the University of Twente in the Netherlands have gained better understanding of superlubricity, where surfaces experience extremely low levels of friction.

The team addressed a longtime mystery in the principles of superlubricity – a state in which two surfaces experience little to almost no friction when sliding across one another. Superlubricity is associated with molecular smooth surfaces such as graphene and has only been observed in a laboratory environment where these surfaces can be synthesized. In various technological applications, this phenomenon could potentially reduce friction up to 1000 – 10000 times, as compared to conventional friction in machines and mechanisms.

Researchers at the University of Sussex and the University of Brighton have presented their recent work on thermoelectric capture, using highly conductive graphene sheets, which aims to improve technologies that capture and convert heat into electricity and tackle the barriers standing before these methods. The aims to advance the possibility of cheap, sustainable technologies for heat capture and conversion – as well as reach a new understanding of how conductivity in graphene-based nanomaterials can be best exploited.

The team assembled nanomaterial networks of varying density and size, from few to many layers of graphene sheets, then measured electrical conductivity as the different arrays were exposed to heat. Their expectation was that the assemblies of larger, thicker sheets would exhibit the highest levels of conductivity but in fact, the opposite outcome was observed, where the smaller, thinner sheets spontaneously formed dense-packed arrays, and performed better than the many-layered samples. 

Researchers at China's Hunan University, Chinese Academy of Sciences and the University of Washington in the U.S have developed a metal-free nanozyme based on graphene quantum dots (GQDs) for highly efficient tumor chemodynamic therapy (CDT).

GQDs have potential as a cost-effective means of addressing the toxicity concerns associated with metal-based nanozymes in tumor CDT. However, the limited catalytic activity of GQDs has posed significant challenges for their clinical application, particularly under challenging catalytic conditions. "The obtained GQDs, which are made from red blood cell membranes, are highly effective in treating tumors with few side effects," said Liu Hongji, a member of the research team. "One of the advantages is that they are metal-free. In addition, they function as excellent peroxidase-like biocatalysts."

Researchers at the University of Hong Kong, National Center for Nanoscience and Technology in Beijing, Harvard University and the University of Stuttgart have advanced the field of molecular sensing by developing a novel method to improve the sensitivity of surface-enhanced infrared absorption (SEIRA). SEIRA uses plasmonic nanostructures to amplify the infrared signals of molecules adsorbed on their surface. Graphene is a particularly promising material for SEIRA because of its high sensitivity and tunability. However, the interaction between graphene and molecules is weakened by intrinsic molecular damping.

The new approach employs synthesized complex-frequency waves (CFW) to amplify the molecular signals detected by graphene-based sensors by at least an order of magnitude. It also applies to molecular sensing in different phases.