GNRs - Page 8

Researchers from Seoul National University developed a simple method to produce graphene nanonet (GNN) patterns on large areas. The patterns, which contain continuous networks of chemically functionalized graphene nanoribbons, could be used to make biosensor devices. These patterns behave better than GO or GNRs which are commonly used for biological sensing applications and are easy to make.

The GNN structures are made from continuous networks of GNRs with chemical functional groups on their edges. The chemical functional groups in the GNN can be functionalized with biological molecules such as DNA for biochip applications. The researchers successfully performed fluorescence imaging of DNA molecules on the GNN channels and has electrically detected the DNA at 1 nM concentrations using the GNN-based biochip devices.

Researchers from Stanford developed a new way to produce graphene ribbons using DNA strands. GNRs have a bandgap and so can be used as building blocks for transistors, and indeed the researchers produced transistors based on GNRs produced using this new process.

The process goes like this: it starts with a silicon substrate, dipped in a DNA solution (derived from bacteria). They then combed the DNA strands into relatively straight lines (using a common technique). They exposed the DNA to a copper salt solution which allowed the copper ions to be absorbed into the DNA.

Researchers from Rice University managed to create long graphene nanoribbons (GNRs) that are very thin - less than 10 nanometers wide. This lithography process, discovered by chance, uses water to act as a mask.

The researchers found out that water gathers at the wedge between the raised lithography pattern and the graphene surface - and that's the place where the ribbons are formed. This water formation is called a meniscus and it is created when the surface tension of a liquid causes it to curve. The meniscus mask protects a tiny ribbon of graphene from being etched away when the pattern is removed.

IBM researchers have developed a graphene-based infrared detector, driven by intrinsic plasmons. This new design proved to be much more photo-responsive compared to non-plasmonic graphene detectors.

The researchers used CVD to grow graphene on copper foil. The copper was etched away and the graphene sheet was transferred to a silicon/silicon-oxide chip. The researchers patterned graphene ribbons (widths of 80 to 200 nm).

Researchers from Rice University managed to synthesize graphene nanoribbons (GNRs) on metal from the bottom up (atom by atom). They call these Graphene onion rings and you can see why from the image below:

The researchers explain that usually, when growing graphene using CVD, the deposition starts as one atom attach it self to a speck of dust or a bump on the metal substrate. The other atoms join in (this is called nucleation) to join the familiar graphene pattern. This time the researchers used a high pressure hyrdogen-rich environment, and this produced the first rings. In this case, the entire edge of the first ring becomes a nucleation site and a new sheet starts under the first graphene sheet.

Researchers from Singapore's A*STAR Institute developed a new graphene ribbons (GNRs) based magnetic field-effect transistor (it responds to changes in a magnetic field).

The basic idea is to use two armchair-edged GNRs joined end to end. One of the ribbons acts as a metallic conductor while the other one (which is wider) acts as a semiconductor. The existence of a magnetic field makes this device conductive.

Graphene Nanoribbons have two kinds of edges: zigzag or "armchair". Edge magnetism in zigzag graphene nanoribbons (zGNRs) has been predicted in theory but not in experiments, probably due to the instability of the edges and the usual choice of hydrogen as a terminal to the edges (which can only be stabilized at extremely low hydrogen concentrations). A better terminal is required if we want to preserve the magnetism (which is required for Spintronics application, for example).

Now researchers from Puerto Rico and China have designed new terminals based on ethylene (C₂H₄). They say it's the ideal material to preserve the edge magnetism. This will hopefully indeed enable Spintronics applications based on zGNRs.

Researchers from Rice University developed new Li-Ion anode material from graphene nanoribbons (GNR) and SnO2 (Tin Oxide). They are combining the Tin-Oxide with the GNRs and they say that batteries made with the new material has double the storage capacity compared to traditional graphite anodes.

Basically to create the new material, the researchers mixed the GNRs with tin oxide particles (about 10 nanometer wide). Using cellulose gum binder and water, they apply the new material to a current collector and place it in Li-ion batteries. In the lab tests, the prototype battery had an initial charge capacity of more than 1520 milliamp hours per gram (mAh/g). After repeated charge-discharge cycles that number began to plateau at about 825 mAh/g.

Researchers from Aalto University in Finland and Utrecht University in the Netherlands managed to create single-atom contacts to connect gold and graphene nanoribbons. In their experiments, they showed how a single chemical bond can be used to make an electrical contact to a graphene nanoribbon.

Using atomic force microscopy (AFM) and scanning tunneling microscopy (STM), the researchers mapped the structure of the graphene nanoribbons and then used voltage pulses from the tip of the scanning tunnelling microscope to form single bonds to the graphene nanoribbons, at a precise, specific location. The electric pulse removed a single hydrogen atom from the end of a graphene nanoribbon and this initiates the bond formation. 

Researchers from Kansas State University developed improved electron-tunneling based humidity, pressure or temperature sensing devices using graphene quantum dots. Those devices are more responsive in vacuum compared to most sensors. They will be able to detect trace amounts of water on Mars, for example.

To create the Quantum Dots, the researchers used nanoscale graphite cuttings to produce graphene nanoribbons. Chemically cleaving those ribbons into 100 nanometer sized pieces created the quantum dots.