News — Graphene oxide

With the growth in the global population there is a greater requirement in the production of crops to meet this demand. In the development of crops, micronutrients (such as zinc and copper) in the form of fertilisers are required to optimise plant growth. Standard fertilisers are usually water-soluble salts containing sulfates which can be affected by leaching or run-off, particularly in high rainfall locations. As a result of the fast release, large volumes of these fertilisers are required to provide sufficient nutrients to the plants but results in higher costs due to the inefficiency as well as potential environmental issues.

Research carried out by the University of Adelaide has demonstrated the use of graphene oxide as high capacity carriers of micronutrients for use in slow-release fertilisers. Graphene oxide has a very high surface area and large quantities of oxygen functional groups on the surface of the sheet. Electrostatic interactions from the oxygen functionalities allows metal nutrients to bind to the graphene oxide sheets, with the high surface area resulting in large loading quantities. The results of the study showed highly desirable release rates, with initial fast release followed by a slow, sustained rate. This mechanism of release is favourable, particularly in environments where seedlings require larger initial quantities of micronutrients followed by a slower uptake as they grow.

This application is just one of many that utilise the unique properties of graphene and graphene oxide and further demonstrates the wide range of potential uses. If you have any enquiries about the applications of graphene oxide or how it can improve your existing applications, please get in touch and one of the GOgraphene team will be happy to help.

ACS Appl. Mater. Interfaces, 2017, 9, 43325−43335

The control of water permeation rates though membranes is an important factor in the water purification industry as well as in the medical field. Members of the National Graphene Institute have recently published an article in Nature outlining a membrane primarily consisting of graphene oxide with electronically controlled permeation. The researchers installed conductive filaments into the graphene oxide membranes which was prepared onto a porous silver substrate. Graphene oxide is an insulating material, so a gold thin film (10 nm) was deposited onto the surface to provide the conductivity. Layers of graphene oxide then create channels in which the water can pass. Between the layers of graphene oxide, the water molecules become ionised through the application of current in the gold thin film which then repels the flow of water through the membrane. The team identified a correlation between the applied current, rather than voltage, with permeation rate as the voltage required to maintain the current varied. By utilising this information, the level of permeation was able to be varied through control of the applied current, from ‘ultrafast’ to complete blockage.

This application is just one of many studied by academic groups to utilise the unique properties of graphene oxide and highlights the importance that graphene and graphene oxide materials will have on technology in the near future. If you have any enquiries about the applications of graphene oxide or how it can improve your existing applications, please get in touch and one of the GOgraphene team will be happy to help.

Nature, 2018, 559, 236-240

The Internet of Things, often referred to as IoT, refers to a network of physical devices which are able to communicate data. These devices can include cars, appliances, heating, lighting and security systems. In order to work, these devices need to be equipped with software, electronics and sensors, they also need to work with the internet infrastructure that already exists. Consumer IoT devices are already on the market in the shape of smart home appliances such as Hive Active Heating and The Amazon Echo, however the vision for the IoT stretches into the connectivity of trillions of devices - a vision that can only be realised through further innovation and research of all aspects required by the IoT.

A recent paper published in Scientific Reports demonstrates the potential for graphene oxide in wireless humidity sensing. The group investigated the relative dielectric permittivity of graphene oxide under various humidity conditions at GHz, showing that increased humidity leads to an increase in the permittivity. This is a result of higher humidity leading to a greater uptake of water. By printing a graphene antenna with the graphene oxide layer, the researchers were then able to create a battery free and wireless radio-frequency identification (RFID) humidity sensor. As the device is sensitive to its surrounding humidity, it could be used as a low-cost local humidity sensor in IoT applications.

This research serves as another great example of how graphene oxide has the potential to enable a diverse range of innovations and applications. The graphene oxide supplied through GOgraphene is being used in both academic and industrial research in many sectors. If you are interested in using graphene oxide in your research, please let us know and a member of the team will be happy to help you.

Scientific Reports, 2018, 8, 43

Defined as an airway inflammation, asthma affects around 300 million people around the world. Current non-invasive methods for monitoring asthma are not only expensive, but are also limited by low sensitivity. One avenue of research around asthma monitoring is the use of biomarkers in exhaled breath condensate (EBC). The droplets of fluid which are exhaled during normal breathing include non-volatile compounds such as nitrate, nitrite and hydrogen peroxide as well as larger molecules such as proteins. There have been several research studies examining the use of EBC nitrite as a biomarker for measuring both inflammation and oxidative distress in the respiratory tract with promising results achieved.

A recent paper published in Microsystems & Nanoengineering looked at using reduced graphene oxide for electrochemical sensing of nitrite content in exhaled breath condensate. The sensors were made by adding a 3 µL aliquot of graphene oxide dispersion to a gold electrode before drying the surface at room temperature. A glass slide was used to ensure a thin, even GO layer across the surface was achieved. The graphene oxide was then reduced electrochemically. Through multiple experiments, the researchers were able to demonstrate high precision in quantifying nitrite in the samples tested in the clinically relevant µM range. The team validated the performance of their sensors on clinical EBC samples by comparing to results previously achieved by chemiluminescence.

If you are interested in using graphene oxide in your research, please get in touch. A member of the GOgraphene team will be happy to help answer your questions about which graphene oxide product might perform best and how we can support your research programme moving forward.

Microsystems & Nanoengineering, 2017, 3, 17022

Air pollution is an increasing issue for people around the globe, especially those living in large cities. While the drive to swap to cleaner, greener technologies and alternatives grows, there is still a need to offer air purification in many technology areas. The issues of air purity affect not only the outdoor environment, but also indoors. The building, its decoration and the local levels of Radon gas can all impact the air quality inside buildings.

A 2015 paper by Xiong et al worked on combining absorption with photocatalysis. The concept was to increase the concentration of pollutants around a photocatalyst by absorbing them onto an adjacent surface. The photocatalytic oxidation process would then regenerate the absorbent, preventing the surface from becoming saturated and a “one use only” technology.

Their research focussed on the development of a graphene aerogel combined with titanium dioxide. Titanium dioxide is well known for its photocatalytic activity while graphene aerogels are of great interest due to their exceptionally high surface area. The group added the titanium oxide to a graphene oxide dispersion and then went on to functionalise the graphene oxide by reacting it with ethylenediamine before converting it into an aerogel. The group found that the shape of the aerogel was easily directed by the shape of the vessel it was formed in, offering great flexibility for creating air purification cartridges. At the time of publication, while the group had confirmed that the desired material could be made, further work was still needed to understand the purification capability of the TiO2/graphene aerogel.

If you would be interested in using graphene oxide in your research, please get in touch.

Procedia Engineering, 2015, 121, 957 – 960