Self-assembly of magnetite nanocubes into helical superstructures.............

Dr. Rafal Klajn and postdoctoral fellow Dr. Gurvinder Singh of the Institute's Organic Chemistry Department used nanocubes of an iron oxide material called magnetite. As the name implies, this material is naturally magnetic: It is found all over the place, including inside bacteria that use it to sense the Earth's magnetic field.

Magnetism is just one of the forces acting on the nanoparticles. Together with the research group of Prof. Petr Král of the University of Illinois, Chicago, Klajn and Singh developed theoretical models to understand how the various forces could push and pull the tiny bits of magnetite into different formations. "Different types of forces compel the nanoparticles to align in different ways," says Klajn. "These can compete with one another; so the idea is to find the balance of competing forces that can induce the self-assembly of the particles into novel materials." The models suggested that the shape of the nanoparticles is important -- only cubes would provide a proper balance of forces required for pulling together into helical formations.

                                                                   

SEM image of a well-defined double helix.

Credit: Image courtesy of Weizmann Institute of Science

 

()

The researchers found that the two main competing forces are magnetism and the van der Waals force. Magnetism causes the magnetic particles to both attract and repel one another, prompting the cubic particles to align at their corners. Van der Waals forces, on the other hand, pull the sides of the cubes closer together, coaxing them to line up in a row. When these forces act together on the tiny cubes, the result is the step-like alignment that produces helical structures.

In their experiments, the scientists exposed relatively high concentrations of magnetite nanocubes placed in a solution to a magnetic field. The long, rope-like helical chains they obtained after the solution was evaporated were surprisingly uniform. They repeated the experiment with nanoparticles of other shapes but, as predicted, only cubes had just the right physical shape to align in a helix. Klajn and Singh also found that they could get chiral strands -- all wound in the same direction -- with very high particle concentrations in which a number of strands assembled closely together. Apparently the competing forces can "take into consideration" the most efficient way to pack the strands into the space.

Although the nanocube strands look nice enough to knit, Klajn says it is too soon to begin thinking of commercial applications. The immediate value of the work, he says, is that it has proven a fundamental principle of nanoscale self-assembly. "Although magnetite has been well-studied -- also its nanoparticle form -- for many decades, no one has observed these structures before," says Klajn. "Only once we understand how the various physical forces act on nanoparticles can we begin to apply the insights to such goals as the fabrication of previously unknown, self-assembled materials."

source:  Weizmann Institute of Science.

Carbon nanotubes based Technology to Produce Clean-Burning Hydrogen Fuel

Rutgers researchers have developed a technology that could overcome a major cost barrier to make clean-burning hydrogen fuel – a fuel that could replace expensive and environmentally harmful fossil fuels.The new technology is a novel catalyst that performs almost as well as cost-prohibitive platinum for so-called electrolysis reactions, which use electric currents to split water molecules into hydrogen and oxygen. The Rutgers technology is also far more efficient than less-expensive catalysts investigated to-date.

                                      

A new technology based on carbon nanotubes promises commercially viable hydrogen production from water

Hydrogen has long been expected to play a vital role in our future energy landscapes by mitigating, if not completely eliminating, our reliance on fossil fuels,” said Tewodros (Teddy) Asefa, associate professor of chemistry and chemical biology in the School of Arts and Sciences. “We have developed a sustainable chemical catalyst that, we hope with the right industry partner, can bring this vision to life.” Asefa is also an associate professor of chemical and biochemical engineering in the School of Engineering. He and his colleagues based their new catalyst on carbon nanotubes – one-atom-thick sheets of carbon rolled into tubes 10,000 times thinner than a human hair. Finding ways to make electrolysis reactions commercially viable is important because processes that make hydrogen today start with methane – itself a fossil fuel. The need to consume fossil fuel therefore negates current claims that hydrogen is a “green” fuel.
       
       Electrolysis, however, could produce hydrogen using electricity generated by renewable sources, such as solar, wind and hydro energy, or by carbon-neutral sources, such as nuclear energy. And even if fossil fuels were used for electrolysis, the higher efficiency and better emissions controls of large power plants could give hydrogen fuel cells an advantage over less efficient and more polluting gasoline and diesel engines in millions of vehicles and other applications. In a recent scientific paper published in Angewandte Chemie International Edition, Asefa and his colleagues reported that their technology, called “noble metal-free nitrogen-rich carbon nanotubes,” efficiently catalyze the hydrogen evolution reaction with activities close to that of platinum. They also function well in acidic, neutral or basic conditions, allowing them to be coupled with the best available oxygen-evolving catalysts that also play crucial roles in the water-splitting reaction.
   
             The researchers have filed for a patent on the catalyst, which is available for licensing or research collaborations through the Rutgers Office of Technology Commercialization. The National Science Foundation funded the research. Asefa, an expert in inorganic and materials chemistry, joined the Rutgers faculty in 2009 after four years as an assistant professor at Syracuse University. Originally from Ethiopia, he is a resident of Montgomery Township, N.J. In addition to catalysis and nanocatalysis, his research interests include novel inorganic nanomaterials and nanomaterials for biological, medical biosensing and solar cell applications.



source: RUTGERS TODAY

Mathematical equation that explains the behavior of nanofoams

A research study, participated in by Universidad Carlos III de Madrid (UC3M), has discovered that nanometric-size foam structures follow the same universal laws as does soap lather: small bubbles disappear in favor of the larger ones.


                                                   

                             For this purpose, the scientists carried out an experiment that consisted in "bombardment" of a small silicon plate with energetic particles from a plasma. The objective was to observe how the surface of this crystal reacted to these different "attacks" from this type of ion radiation (ions are used: atoms of a gas that have lost an electron). "At the outset, we were studying other methods of erosion and looking for a rippled structure at the edge of our sample after applying this technique, but when we looked at its center we observed a cellular structure that got our attention because of its similarity to many other natural and artificial systems," one of the authors of the study, Mario Castro, UPCO Professor, revealed.

Cellular structures that are more or less disordered can be found in many natural systems: from the hides of animals, such as a giraffe, to bath froth or beer foam, to microscopic fluid convection, basalt column landscapes or diverse crystalline materials. This particular order is also evident in artificial structures and even political ones, such as modern architecture or demarcation of provinces on maps.

"It is of interest to confirm that the same universal laws which regulate the cellular structures in other systems are also regulating at the nanoscale," Rodolfo Cuerno from the UC3M Mathematics Department noted. "Furthermore," he added "it is the first time that the evolution of a system of this kind is reproduced quite well by a single differential equation," which also is applied to other systems. The validity of the model in this study means that the formation of certain self-organized patterns and the dynamics of the foam would be different manifestations of a same principle.

"The results of this study help us to understand how certain material systems evolve in the presence of an external agent, as in this case of ion radiation. In addition, there exists interest of a practical nature because of the importance of the technological applications of silicon as well as for the nanometric dimensions in which the phenomenon unfolds," explained Luis Vázquez, from the Instituto de Ciencia de Materiales (Materials Science Institute) de Madrid at the CSIC.

The experimental observations have been carried out using an atomic force microscope, a machine with great precision. This type of microscope has enormous spatial resolution: it distinguishes variations in height up to a nanometer (the millionth part of a millimeter) and movements on a horizontal plane of up to 10 nanometers.

This research could have further future applications, since in general, methods are being sought to produce structures with nanometric dimensions for diverse uses, according to the scientists: for example, in order to obtain favorable conditions in certain catalytic chemical reactions, to optimize displacement of fluids in circuits on such small scale or in optoelectronics, to generate laser light if certain structures are sufficiently ordered.

 SOURCE:Universidad Carlos III de Madrid - Oficina de Información Científica.

Nanotube composites increase the efficiency of next generation of solar cells

                            

Carbon nanotubes, CNTs, are one dimensional nanoscale cylinders made of carbon atoms that possess very unique properties.  For example, they have very high tensile strength and exceptional electron mobility, which make them very attractive for the next generation of organic and carbon-based electronic devices.

There is an increasing trend of using carbon based nanostructured materials as components in solar cells. Due to their exceptional properties, carbon nanotubes are expected to enhance the performance of current solar cells through efficient charge transport inside the device. However, in order to obtain the highest performance for electronic applications, the carbon nanotubes must be assembled into a well-ordered network of interconnecting nanotubes. Unfortunately, conventional methods used today are far from optimal which results in low device performance.

In a new study, a team of physicists and chemists at Umeå University have joined forces to produce nano-engineered carbon nanotubes networks with novel properties.

For the first time, the researchers show that carbon nanotubes can be engineered into complex network architectures, and with controlled nano-scale dimensions inside a polymer matrix.

 “We have found that the resulting nano networks possess exceptional ability to transport charges, up to 100 million times higher than previously measured carbon nanotube random networks produced by conventional methods,” says Dr David Barbero, leader of the project and assistant professor at the Department of Physics at Umeå University.

                   The high degree of control of the method enables production of highly efficient nanotube networks with a very small amount of nanotubes compared to other conventional methods, thereby strongly reducing materials costs.                                     

                                                   

In a previous study (Applied Physics Letters, Volume 103, Issue 2, 021116 (2013))  the research team of David R. Barbero already demonstrated that nano-engineered networks can be produced onto thin and flexible transparent electrodes that can be used in flexible solar cells. These new results are expected to accelerate the development of next generation of flexible carbon based solar cells, which are both more efficient and less expensive to produce.

so urce:Umeå universitet.

nanoparticle that only attacks cervical cancer cells

One of the most promising technologies for the treatment of various cancers is nanotechnology, creating drugs that directly attack the cancer cells without damaging other tissues’ development. The Laboratory of Cellular Oncology at the Research Unit in Cell Differentiation and Cancer, of the Faculty of Higher Studies (FES) Zaragoza UNAM (National Autonomous University of Mexico) developed a therapy to attack cervical cancer tumors.

The treatment, which has been tested in animal models, consists of a nanostructured composition encapsulating a protein called interleukin-2 (IL -2), lethal to cancer cells.

According to the researcher Rosalva Rangel Corona, head of the project, the antitumor effect of interleukin in cervical cancer is because their cells express receptors for interleukin-2 that “fit together " like puzzle pieces with the protein to activate an antitumor response .

The scientist explains that the nanoparticle works as a bridge of antitumor activation between tumor cells and T lymphocytes. The nanoparticle has interleukin 2 on its surface, so when the protein is around it acts as a switch, a contact with the cancer cell to bind to the receptor and to carry out its biological action.

Furthermore, the nanoparticle concentrates interleukin 2 in the tumor site, which allows its accumulation near the tumor growth. It is not circulating in the blood stream, is “out there" in action.

The administration of IL-2 using the nanovector reduces the side effects caused by this protein if administered in large amounts to the body. These effects can be fever, low blood pressure, fluid retention and attack to the central nervous system, among others.

It is known that interleukin -2 is a protein (a cytokine, a product of the cell) generated by active T cells. The nanoparticle, the vector for IL-2, carries the substance to the receptors in cancer cells, then saturates them and kills them, besides generating an immune T cells bridge (in charge of activating the immune response of the organism). This is like a guided missile acting within tumor cells and activating the immune system cells that kill them.

A woman immunosuppressed by disease produces even less interleukin. For this reason, the use of the nanoparticle would be very beneficial for female patients.

The researcher emphasized that his group must meet the pharmaceutical regulations to carry their research beyond published studies and thus benefit the population.

source: AlphaGalileo