One of the greatest challenges in harnessing the power of nanotechnology is achieving dynamic control of mechanical, electronic, optical and chemical properties of nanoscale structures and devices. Dynamic control can be achieved through the use of piezoelectric materials. These are materials where applying a mechanical strain results in an electrical voltage or conversely, application of an electric field induces mechanical deformation. While piezoelectricity has mainly been shown for 3D bulk materials, the piezoelectric effect has also been demonstrated and exploited at the nanoscale. Researchers have now demonstrated through density functional theory calculations that piezoelectricity can be engineered into non-piezoelectric graphene by selective surface adsorption of atoms on only one side, which breaks inversion symmetry.
Graphene is an excellent conductor of heat and might be an ideal material for thermal management in nanoelectronics. In field-effect transistors or interconnects most of the heat propagates directly below the graphene channel in the direction of the heat sink, that is, the bottom of a silicon wafer. For this reason, the highly thermally resistive silicon layers act as a thermal bottleneck, preventing the full utilization of graphene's excellent intrinsic properties. The breakdown current density in typical graphene devices is a hundred times larger than the fundamental limit in metals, which is set by electromigration. Researchers wanted to see if we can push the breakdown current density in graphene even further by better removal of dissipated heat. They managed to do it with the help of high-quality synthetic diamond. The graphene transistors or interconnects on synthetic diamond can sustain current densities which are a thousand times larger than in metals.
Noble metal nanoparticles such as gold, silver or platinum are widely used by scientists to develop novel applications in sensing, energy, spectroscopy, and catalysis. For instance, the combination of metal nanoparticles and carbon nanomaterials - graphene and nanotubes - has met with great interest in the area of biosensor applications as well as composite fabrication for light-energy conversion. In these applications, researchers make use of the formation of organic/inorganic hybrid nanosystems by incorporating metal nanoparticles in or onto the graphitic structures of carbon nanotubes or graphene. Researchers have now discovered a novel phenomenon whereby graphene can be catalytically transformed into carbon nanotubes by gold nanoparticles at relatively low temperatures.
Apart from graphene, other two-dimensional structures are also known to have unique properties which researchers are eager to exploit for novel nanotechnology applications in nanoelectronics and sensor or energy storage technology. Particular interest has been on semiconducting materials, such as molybdenum disulfide (MoS2), an abundant material in nature, which exhibits the unique physical, optical and electrical properties correlated with its single-layer atomic layer structure. Researchers have now fabricated a mechanically exfoliated single-layer MoS2 based phototransistor and investigated its electric characteristics in detail. These new findings show that, when compared with a 2D graphene-based device, the single-layer MoS2 phototransistor exhibits a better photoresponsivity.
Thermal interface materials (TIMs) are essential ingredients of thermal management. TIMs are applied between the heat source, e.g. computer chips, and heat sinks and their function is to fill the voids and grooves created by imperfect surface finish of mating surfaces. Conventional TIMs filled with thermally conductive particles require high volume fractions of filler particles. But now, researchers have achieved a record enhancement of the thermal conductivity of TIMs by addition of an optimized mixture of graphene and multilayer graphene. The thermal conductivity of the epoxy matrix material was increased by an impressive factor of 23 at the 10 volume % of graphene loading. The epoxy-graphene composite preserved all the properties required for industrial TIM applications.
A University of Ulster laboratory has found a simple, low cost and environmentally friendly way to turn common graphite flakes into bulk amounts of either high quality graphene nanosheets or quantum dots. Such structures could lead to new nanoelectronics and energy conversion technologies. The scientists discovered a simple process, which is quicker and environmentally friendlier than currently established techniques for making high quality graphene nanosheets and quantum dots at an industrial scale. The most important attribute of the produced graphene nanosheets and quantum dots compared to those reported in the literature is that they are clean from any solvent contamination and possess a low concentration of oxygen, which is inherited from the starting graphite powder.
Graphene research papers are popping up left and right at what seems like an accelerating speed and growing volume. One of the areas that is seeing vast research interest is the biological interfacing of graphene for instance for sensor applications. Today, we are looking at another exciting graphene bio application where a graphene sensor is integrated with microfluidics to sense malaria-infected red blood cells at the single-cell level. Specific binding between ligands on positively charged knobs of infected red blood cells and receptors functionalized on graphene inside microfluidic channels induces a distinct conductance change. Conductance returns to baseline value when infected cell exits the graphene channel.
The integration of biological components with electronics, and more specifically, the interfacing of complex biological systems is one of the current challenges on the path towards bioelectronics (or bionics for short). Up to know, and due to its technology maturity, most of the work has been done based on Si-FET technology. However, there have been some issues related to this technology which prevented a more successful implementation into real applications. Researchers have now demonstrated, for the first time, that CVD grown graphene can be employed to fabricate arrays of transistors which are able to detect the electrical activity of electrogenic cells.