Graphene takes a Step Toward Renewable Fuel – Converting water and carbon dioxide to the renewable energy of the future

Jianwu Sun at Linköping University inspecting the growth reactor for growth of cubic silicon carbide. Credit: Thor Balkhed/LiU

Using the energy from the sun and graphene applied to the surface of cubic silicon carbide, researchers at Linköping University, Sweden, are working to develop a method to convert water and carbon dioxide to the renewable energy of the future.

They have now taken an important step toward this goal, reporting a method that makes it possible to produce graphene with several layers in a tightly controlled process. The researchers have also shown that graphene acts as a superconductor in certain conditions. Their results have been published in the scientific journals Carbon and Nano Letters.

Carbon, oxygen and hydrogen are the three elements obtained by taking apart molecules of carbon dioxide and water. The same elements are the building blocks of chemical substances used for fuel, such as ethanol and methane. The conversion of carbon dioxide and water to renewable fuel could provide an alternative to fossil fuels and contribute to reducing carbon dioxide emissions into the atmosphere. Jianwu Sun, senior lecturer at Linköping University, is trying to find a way to do just that.

Researchers at Linköping University have previously developed a world-leading method to produce cubic silicon carbide, which consists of silicon and carbon. The cubic form has the ability to capture energy from the sun and create charge carriers. This is, however, not sufficient. Graphene, one of the thinnest materials ever produced, plays a key role in the project. The material comprises a single layer of carbon atoms bound to each other in a hexagonal lattice. Graphene has a high ability to conduct an electric current, a property that would be useful for solar energy conversion. It also has several unique properties, and possible uses of graphene are being extensively studied all over the world.

Read Original Post from Linkoping University

In recent years, the researchers have attempted to improve the process by which graphene grows on a surface in order to control the properties of the graphene. Their recent progress is described in an article in the scientific journal Carbon.

“It is relatively easy to grow one layer of graphene on silicon carbide. But it’s a greater challenge to grow large-area uniform graphene that consists of several layers on top of each other. We have now shown that it is possible to grow uniform graphene that consists of up to four layers in a controlled manner,” says Jianwu Sun of the Department of Physics, Chemistry and Biology at Linköping University.

One of the difficulties posed by multilayer graphene is that the surface becomes uneven when different numbers of layers grow at different locations. The edge when one layer ends has the form of a tiny, nanoscale staircase. Flat layers are desirable, so these steps are a problem, particularly when the steps accumulate in one location, like a wrongly built staircase in which several steps have been united to form one large step. The researchers have now found a way to remove these large, united steps by growing the graphene at a carefully controlled temperature. Furthermore, the researchers have shown that their method makes it possible to control how many layers the graphene will contain. This is the first key step in an ongoing research project whose goal is to make fuel from water and carbon dioxide.

In a closely related article in the journal Nano Letters, the researchers describe investigations into the electronic properties of multilayer graphene grown on cubic silicon carbide.

“We discovered that multilayer graphene has extremely promising electrical properties that enable the material to be used as a superconductor, a material that conducts electrical current with zero electrical resistance. This special property arises solely when the graphene layers are arranged in a special way relative to each other,” says Jianwu Sun.

Theoretical calculations had predicted that multilayer graphene would have superconductive properties, provided that the layers are arranged in a particular way. In the new study, the researchers demonstrate experimentally for the first time that this is the case. Superconducting magnets are extremely powerful magnets used in medical magnetic resonance cameras and in particle accelerators. There are many potential areas of application for superconductors, such as electrical supply lines with zero energy loss, and high-speed trains that float on a magnetic field. Their use is currently limited by the inability to produce superconductors that function at room temperature. Currently available superconductors function only at extremely low temperatures.

 Explore further: Atoms use tunnels to escape graphene cover

More information: Yuchen Shi et al, Elimination of step bunching in the growth of large-area monolayer and multilayer graphene on off-axis 3C SiC (111), Carbon (2018). DOI: 10.1016/j.carbon.2018.08.042

Weimin Wang et al. Flat-Band Electronic Structure and Interlayer Spacing Influence in Rhombohedral Four-Layer Graphene, Nano Letters (2018). DOI: 10.1021/acs.nanolett.8b02530

Journal reference: Carbon   Nano Letters  

Provided by: Linköping University

 

Smart Cancer Nanotheranostics

(Nanowerk Spotlight) Cancer is one of the leading  causes of death in the world and remains a difficult disease to treat. Current  problems associated with conventional cancer chemotherapies include insolubility  of drugs in aqueous medium; delivery of sub-therapeutic doses to target cells;  lack of bioavailability; and most importantly, non-specific toxicity to normal  tissues. Recent contributions of nanotechnology research address possible  solutions to these conundrums. Nevertheless, challenges remain with respect to  delivery to specific sites, real time tracking of the delivery system, and  control over the release system after the drug has been transported to the  target site.

Nanomedical research on nanoparticles is exploring these issues  and has already been showing potential solutions for cancer diagnosis and  treatment. But a heterogeneous disease like cancer requires smart approaches  where therapeutic and diagnostic platforms are integrated into a theranostic  approach.

Theranostics – a combination of the words therapeutics and diagnostics – describes a treatment platform that combines a  diagnostic test with targeted therapy based on the test results, i.e. a step  towards personalized medicine. Making use of nanotechnology materials and  applications, theranostic nanomedicine can be understood as an integrated  nanotherapeutic system, which can diagnose, deliver targeted therapy and monitor  the response to therapy.

Theranostic nanomedicine has the potential for simultaneous and  real time monitoring of drug delivery, trafficking of drug and therapeutic  responses.

Our Smart Materials and Biodevice group at the Biosensors and Bioelectronics Centre, Linkoping University,  Sweden, has demonstrated for the first time a MRI-visual order-disorder micellar nanostructures for smart  cancer theranostics.

        The  drug release mechanism via functional outcome of the pH response illustrated in  the schematic diagram. (Image: Smart Materials and Biodevice group, Linköping  University)   In the report, we fabricated a novel pH-triggered tumour  microenvironment sensitive order-disorder nanomicelle platform for smart  theranostic nanomedicine.             

The real-time monitoring of drug distribution will help  physicians to assess the type and dosage of drug for each patient and thus will  prevent overdose that could result in detrimental side-effects, or suboptimal  dose that could lead to tumour progression.

Additionally, the monitoring of normal healthy tissues by  differentiating with the MRI contrast will help balance the estimation of lethal  dose (for normal tissue) and pharmacologically active doses (for tumour). As a  result, this will help to minimize off-target effects and enhance effective  treatment.

In the present report, the concurrent therapy by doxorubicin and  imaging strategies by superparamagnetic iron oxide nanoparticles with our smart  architecture will provide every detail and thus can enable stratification of  patients into categorized responder (high/medium/low), and has the potential to  enhance the clinical outcome of therapy.

It shows, for the first time, concentration dependent  T2-weighted MRI contrast for a monolayer of clustered cancer cells. The pH  tunable order-disorder transition of the core-shell structure induces the  relative changes in MRI that will be sensitive to tumour microenvironment and  stages.

     A  novel MRI visual order-disorder nanostructure for cancer nanomedicine explores  pH-trigger mechanism for theranostics of tumour hallmark functions. The pH  tunable order-disorder transition induces the relative changes in MRI contrast.  The outcome elucidates the potential of this material for smart cancer  theranostics by delivering non-invasive real-time diagnosis, targeted therapy  and monitoring the course and response of the action. (Image: Smart Materials  and Biodevice group, Linköping University)

Our findings illustrate the potential of these biocompatible  smart theranostic micellar nanostructures as a nontoxic, tumour-target specific,  tumour-microenvironment sensitive, pH-responsive drug delivery system with  provision for early stage tumour sensing, tracking and therapy for cells  over-expressed with folate receptors. The outcomes elucidate the potential of  smart cancer theranostic nanomedicine in non-invasive real-time diagnosis,  targeted therapy and monitoring of the course and response of the action before,  during and after treatment regimen.

By Hirak K Patra, Nisar Ul Khali, Thobias Romu, Emilia  Wiechec, Magnus Borga, Anthony PF Turner and Ashutosh Tiwari, Biosensors and Bioelectronics Centre,  Linköping University, Sweden

Read more: http://www.nanowerk.com/spotlight/spotid=33186.php#ixzz2kTi8huZB