It has been known for some time that graphene can be used for detection of individual gas molecules adsorbed on its surface - a graphene sensor can detect just a single molecule of a toxic gas. However, the extremely high sensitivity of graphene does not necessarily translate into its selectivity to various molecules. In other words, it can be detected that some molecules attached to the graphene surface change the resistivity of a graphene field-effect transistor but one cannot say what kind of a molecules have attached. Scientists have therefore thought that truly selective gas sensing with graphene devices requires the functionalization of graphene surface with some agents specific for different gas molecules. In new research, though, scientists have now found that chemical vapors change the noise spectra of graphene transistors. The noise signal for each gas is reproducible, opening the way for practical reliable and simple gas sensors made from graphene.
In the past couple of decades, thermoelectrics have been drawing more and more research interest due to the limited availability and the negative environmental impact of conventional energy strategies. In the past, as a measuring stick of the conversion efficiency, the term "dimensionless figure-of-merit," also referred to as ZT, has been widely used. A high ZT value usually promises high thermoelectric performance. Typically, good thermoelectric materials should simultaneously display low thermal conductivity and good electrical conductivity. Striving to enhance the performance of thermoelectric materials, researchers from Boston College and MIT have recently reported a novel materials design to achieve a 30 to 40% enhancement in the peak ZT value for n-type SiGe semiconducting alloys.
Graphene with its distinctive band structure and unique physiochemical properties - such as exceptionally low intrinsic electrical resistivity, high surface area, rapid electrode kinetics and good mechanical properties - is considered an attractive material for analytical electrochemistry. However, one of the key technical challenges for the use of graphene as functional material in device applications is the integration of nanoscale graphene onto micro- or millimeter sized sensing platforms. With a new methodology, a team from Florida International University was able to integrate graphene onto three-dimensional (3D) carbon microstructure arrays with good uniformity and controllable morphology.
Counterfeiting of bank notes has always been a problem and central banks are leading a high-tech fight against sophisticated counterfeiting operations. For instance, when the European Central Bank designed its new banknotes, they included a variety of security features - holograms, foil stripes, special threads, microprinting, special inks and watermarks. Another high-tech approach are imprinting radio frequency identification (RFID) tags onto banknotes. While the integration of RFID technology on a banknote is technically possible, no banknotes in the world today employ such a technology. In recent work, researchers in Saudi Arabia have now fabricated the first-ever all-polymer, non-volatile, ferroelectric memory on banknotes.
Graphene-based materials are emerging as highly attractive materials for real applications, especially in the area of energy conversion and storage. There are four major energy-related areas where graphene will have an impact: solar cells, supercapacitors, lithium-ion batteries, and catalysis for fuel cells. A recent review gives a brief overview of the recent research concerning chemical and thermal approaches toward the production of well-defined graphene-based nanomaterials and their applications in energy-related areas. But before graphene-based nanomaterials and devices find widespread commercial use, two important problems have to be solved: one is the preparation of graphene-based nanomaterials with well-defined structures, and the other is the controllable fabrication of these materials into functional devices.
In recent years billions of dollars have been invested in nanotechnology research. Nanotechnology is said to have such pervasive consequences that the 21st century is already proclaimed to become the 'nano-century'. Nanotechnology may also contribute to development in the global South. The new characteristics of nanotechnologies are also said to offer solutions for problems faced by people in the global South, especially in the fields of water, energy, and health. For instance water filters, energy storage systems, solar powered electricity and portable diagnostic tests may be developed and improved using nanotechnology. But the very same features that give rise to new opportunities may also generate new risks. There may be risks to the human body and environment. But for instance also investing in nanotechnology itself can be seen as a risk.
Ultra- or supercapacitors are emerging as a key enabling storage technology for use in fuel-efficient transport as well as in renewable energy. These devices combine the advantages of conventional capacitors - they can rapidly deliver high current densities on demand - and batteries - they can store a large amount of electrical energy. Today's commercial supercapacitors store energy in two closely spaced layers with opposing charges and offer fast charge/discharge rates and the ability to sustain millions of cycles. Researchers have come up with various electrode materials to improve the performance of supercapacitors, focussing mostly on porous carbon due to its high surface areas, tunable structures, good conductivities, and low cost. In recent years, this has increasingly included research on various carbon nanomaterials such as carbon nanotubes, carbon nano-onions, or graphene. In new work, researchers have demonstrated that a common daily waste - the eggshell membrane - can be converted into a high-performance carbon material for supercapacitors.
The global cement industry is currently one of the largest single emitter of carbon dioxide, generating on average about 830 kg of this greenhouse gas for each 1000 kg of cement produced. Considering that the worldwide annual production of cement is a whopping 3.8 trillion kg, the cement industry alone accounts for approximately 5-6% of man-made CO2 emissions. Researchers have now presented a solar-powered process to produce cement without any carbon dioxide. In their STEP (Solar Thermal Electrochemical Production) process, cement limestone undergoes low energy electrolysis to produce lime, O2 and reduced carbonate without carbon dioxide emission. In this new technique, the kiln limestone-to-lime process is replaced by an electrolysis process which changes the product of the reaction of the limestone as it is converted to lime.