Graphene Oxide: Introduction and Market News - Page 29

A team of researchers at the Indian Institute of Science Education and Research presents a promising anode material for lithium-ion batteries, by incorporating unique 3D cobalt oxide microstructures into a reduced graphene oxide composite.

Metal oxides present a potential alternative to conventional graphite anodes and Li alloys. Cobalt oxide (CoO) has particularly promising properties, namely a high specific capacity and excellent cycling stability against lithium. However, particle aggregation and volume expansion have thus far restricted its candidacy as an appropriate anode material. Merging CoO into a graphene hydrogel, which acts as a mechanically stable 3D support, the researchers eliminate the problem of volume expansion. Furthermore, the completely interconnected hybrid material presents improved conductivity.

Researchers at Binghamton University have demonstrated an eco-friendly process that enables unprecedented spatial control over the electrical properties of graphene oxide, which is said to have the potential to revolutionize flexible electronics, solar cells and biomedical instruments.

By using the probe of an atomic force microscope to trigger a local chemical reaction, the scientists showed that electrically conductive features as small as 4 nanometers can be patterned into individual graphene oxide sheets. This approach makes it possible to draw nanoscale electrically-conductive features in atomically-thin insulating sheets with the highest spatial control reported so far, and unlike standard methods for manipulating the properties of graphene oxide, the process can be implemented under ambient conditions and is environmentally-benign, making it a promising step towards the practical integration of graphene oxide into future technologies.

Researchers at Swinburne University of Technology, collaborating with Monash University, have developed an ultrathin, flat, lightweight graphene oxide optical lens with extraordinary flexibility, that enables potential applications in on-chip nanophotonics and improves the conversion process of solar cells. It might also open up new possibilities in areas like non-invasive 3D biomedical imaging, aerospace photonics, micromachines and more.

Recent developments in nano-optics and on-chip photonic systems have increased the demand for ultrathin flat lenses with 3D subwavelength focusing capability (the ability to see details of an object smaller than 200 nanometres). A number of ultrathin flat lens concepts have been developed, but their real-life application is limited due to their complex design, narrow operational bandwidth and time consuming manufacturing processes. This lens, however, has a 3D subwavelength capability that is 30 times more efficient, able to tightly focus broadband light from the visible to the near infrared, and offers a simple and low-cost manufacturing method.

Researchers from the Laboratory of Nanooptics and Plasmonics, Moscow Institute of Physics and Technology (MIPT) in Russia have devised a graphene oxide-based biosensor with the potential of significantly speeding up the process of drug development. Graphene helps to improve the sensor's sensitivity, which in the future may enable the development of new drugs and vaccines against many dangerous diseases like HIV, hepatitis and cancer.

The GO-based biosensors exploit the phenomenon of surface plasmon resonance (SPR). Surface plasmons are electromagnetic waves propagating along a metal-dielectric interface (like gold/air) and having the amplitudes exponentially decaying in the neighbor media. Adsorption of molecules from solution onto a sensing surface alters the refractive index of the medium near this surface and, therefore, changes the conditions of SPR. These sensors can detect biomolecule adsorption even at a few trillionth of a gram per millimeter square. Thanks to these merits, SPR biosensing is an outstanding platform to boost technological progress in the areas of medicine and biotechnology. Nevertheless, the most distinctive feature of such sensors is an ability to "visualize" molecular interactions in real time. Researchers believe that the introduction of this method into preclinical trials, for example, can completely change the pharmaceutical industry.

Scientists at Northwestern University have found how graphene oxide's inherent defects may present an interesting mechanical property. It seems that graphene oxide exhibits remarkable plastic deformation before breaking; While graphene is very strong, it can still break suddenly. It was found that graphene oxide, however, will deform first before eventually breaking.

The researchers used an experimentation and modeling approach to examine the mechanics of GO at the atomic level. Their discovery could potentially unlock the secret to successfully scaling up graphene oxide, an area that has been limited because its building blocks have not been well understood.

A collaborative research performed by scientists from UC Riverside, Moldova State University, and Graphenea demonstrates that a method of reducing graphene oxide to graphene via a high-temperature treatment that increases thermal conductivity along the film direction, while decreasing it across the film. The scientists stress the potential of using this method for thermal management applications, such as fillers in thermal interface materials or flexible heat spreaders for cooling electronics. 

The research shows that thermal conductivity of GO can be majorly increased (nearly 30 times) by bringing GO to a high temperature during a reduction process. It appears that GO, when heated to 1000°C, turns to reduced GO (rGO) that has a high thermal conductivity along the sheet plane. In contrast, thermal conductivity perpendicular to the sheet shows an opposite trend, decreasing with thermal treatment.

Manchester University has teamed up with Amsterdam-based paints and coatings company Akzo Nobel, to investigate graphene oxide-based paints that provide protection against rust and corrosion for large metal structures, such as oil rigs, tankers and bridges.

This collaboration between Akzo Nobel and Manchester University is part of a €1m partnership in corrosion research. Akzo Nobel says graphene oxide could provide an ultra-strong, non-corrosive coating for a wide range of industrial applications. Corrosion in its various forms is estimated to cost the global economy $3 trillion a year. Products to protect against corrosion represent an $18 billion world market.

Researchers from Tsinghua University in Beijing demonstrated a graphene-based LED that not only can be tuned to emit different colors of light, but can do so across nearly the entire visible spectrum: from blue (450-nm wavelength) to red (750-nm wavelength)—basically all colors but the darkest blues and violets. Such a color tunable LED has never before been realized.

The scientists made the light-emitting material from the interface of two different forms of graphene. These forms are graphene oxide (GO) and reduced graphene oxide (rGO). Placed at the interface of the GO and rGO is a special type of partially reduced GO that has optical, physical, and chemical properties that lie somewhere in between those of GO and rGO. The most important "blended" property of the interfacial layer is that it has a series of discrete energy levels, which ultimately allows for the emission of light at many different energies, or colors.

Researchers at VIT University, India demonstrated the application of conjugated polymer/Graphene oxide nanocomposite for thermistor applications. The study resulted in a thermistor that boasted excellent performance, suitable for electronics and sensors. A thermistor is a type of resistor whose resistance is dependent on temperature, more so than in standard resistors.

Interestingly, the study showed that lower amounts of graphene oxide (0.5, 1%) loading exhibited positive temperature coefficient, and higher loading (1.5, 2%) yielded negative temperature coefficient.

Researchers at the University of Aveiro in Portugal designed unique "tea bags" using a porous graphene oxide foam, which they say can help purify water by removing dissolved mercury. These foams demonstrate several significant advantages over existing water purification systems: they are reusable, simple to synthesize and should be easy to produce in bulk at a relatively low cost. The scientists add that they are also not affected by pH, which is beneficial since other sorbents often need the pH to be optimized, which drives up costs.

The scientists heated graphene oxide with ammonia to create a porous 3D material with a high surface area. After screening their materials for their ability to adsorb various toxic pollutants, the team chose to focus on mercury, one of the top three on the EU’s priority list of hazardous substances in water. The "tea bag" form was chosen due to the fact that the foam sometimes broke apart, and also to optimize contact with water.