The fascination with two-dimensional (2D) materials that has started with graphene has spurred researchers to look for other 2D structures like for instance metal carbides and nitrides. A new, very comprehensive review article takes a look at our current knowledge of 2D materials beyond graphene. The paper outlines the different chemical classes of 2D materials and discuss the various strategies to prepare single-layer, few-layer, and multilayer assembly materials in solution, on substrates, and on the wafer scale.
Researchers have exploited the extraordinary electrical and mechanical properties of graphene to create a very efficient electrical/sound transducer. This experimental graphene loudspeaker, without any optimized acoustic design, is simple to make and already performs comparably to or better than similar sized commercial counterparts, and with much lower power consumption. Most speakers available today reproduce sound via a mechanical diaphragm, which is displaced oscillatorily during operation. A wide-band audio speaker typically requires significant damping to broaden the response. Even without optimization, the graphene speaker is able to produce frequency response across the whole audible region, comparable or superior to performance of conventional-design commercial counterparts.
Carbon is the fourth-most-abundant element in the universe and, depending on the arrangements of carbon atoms, takes on a wide variety of forms, called allotropes. Carbon allotropes exhibit unique properties of strength and electrical conductivity. Solid carbon at room temperature has two classical structures: diamond and graphite. In 1985 the discovery of the existence of a third and new carbon allotrope containing sixty perfectly symmetrically arranged carbon atoms (C60) meant a major breakthrough and opened a novel field of carbon nanochemistry. Then, in 1991, carbon nanotubes were discovered and graphene in 2004. Now, a research group in China has designed a novel carbon allotrope they've named D-carbon.
Unlike silicon, graphene lacks an electronic band gap and therefore has no switching capability; which is essential for electronics applications. Opening an energy gap in graphene's electron energy spectrum is therefore a critical prerequisite for instance for creating graphene transistors. One method of obtaining a bandgap is to use reduced graphene oxide, an inexpensive material with an industrial-scalable production route. Researchers have now managed to grow and extend graphene oxide out of graphene oxide flake templates.
The low-frequency fluctuations in electrical current attract particular attention among researchers. The low-frequency electronic 1/f noise was first discovered in vacuum tubes, in 1925, and later observed in a wide variety of electronic materials and devices. The importance of this noise for electronic and communication devices motivated numerous studies of its physical mechanisms and methods for its control. Researchers were now able to shed light on 1/f noise origin and mechanisms using a set of multi-layered graphene samples with the thickness continuously varied from around 15 atomic planes to a single layer of graphene.
A bacterium which causes disease reacts to the antibiotics used as treatment by becoming resistant to them, sooner or later. This natural process of adaptation, antimicrobial resistance, means that the effective lifespan of antibiotics is limited. Unnecessary use and inappropriate use of antibiotics favors the emergence and spread of resistant bacteria. New research uses a graphene-based photothermal agent to trap and kill bacteria.
Graphene has the potential to revolutionize many fields, especially in electronics to replace the currently used silicon materials. However, graphene does have an Achilles heel: pristine graphene is semi-metallic and lacks the necessary band gap to sever as a transistor. At present, a big challenge for graphene science is how to open a considerable band gap for graphene without significantly degrading its carrier mobility. New theoretical results suggest a rather practical solution for gap opening of graphene and silicene while preserving the desired high carrier mobility, which would allow them to serve as field effect transistors and other nanodevices.
Fuel cells are able to convert chemical energy to electrical energy with little pollutant emission and high energy conversion efficiency. Despite these advantages, the performance of fuel cells depends largely on the oxygen reduction reaction (ORR), which is substantially affected by the activity of the cathode catalyst. Since the sluggish kinetics of ORR is the major factor impeding large-scale application of fuel cells, most research focuses on developing efficient catalysts for ORR.