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Examples of handheld devices that could benefit from a new oxide compound for power electronics.

New Material Offers a Revolutionary Approach to Power Electronics

Researchers at the University of Utah and the University of Minnesota have discovered that when two oxide compounds—strontium titanate (STO) and neodymium titanate (NTO)—are joined together, they make an extraordinary conductive material that could vastly improve power transistors.  The researchers have shown that these two materials—which on their own operate as insulators—are up to five times more conductive than silicon.

In research described in the journal APL Materials, scientists found that the bonds between the atoms from the oxide compounds arrange themselves in a way that generates 100 times more free electrons than conventional semiconductors, which means the new material can transport more electrical current.

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Organic nanowires bound for supramolecular electronics

Promise of Nanowires in Optoelectronics Realized By Getting Them Connected

Supramolecular electronics has been solidifying as the bridge between molecular electronics—in which molecules become the basic building blocks of electronics—and the use polymers for the fabrication of nanoscale circuitry. A supramolecule is actually a number of different molecules that are fused together to act as a single molecule and carry out a particular programmed function. These supramolecules are used, for instance, in block copolymer-based supramolecular solutions that direct the self-assembly of nanoparticles.

Now researchers at the University of Strasbourg and the Le Centre National de la Recherche Scientifique (CRNS) in France, along with collaborators from the University of Nova Gorica in Slovenia, have buoyed the prospects of supramolecular electronics by addressing one of the chief problems of supramolecular organic nanowires for optoelectronics: getting them connected.

In research described in the journal Nature Nanotechnology, the international team of researchers fabricated a photovoltaic device in which they managed to connect and integrate hundreds of organic nanowires.

This is a significant achievement, because supramolecular organic nanowires have long tantalized researchers in the field of optoelectronics. Their highly efficient generation of excitons—essentially energized electrons that are formed when light hits a semiconductor—make devices like solar cells very sensitive to light and boost their light absorption coefficient.

While this is indeed tempting, the rub has been that you couldn’t harvest that photocurrent from the supramolecular nanowires unless they were connected to nanoelectrodes (anodes and cathodes) that carry out different functions. And the best anyone had previously been able to do was connect just a few. Thus, these nanowires were limited to use in very rudimentary devices.

To the rescue is this new approach: a nanomesh scaffold that supports and connects the supramolecular nanowires between two nanoelectrodes with different work functions.

The researchers were able to fabricate this nanomesh scaffold using a technique known as nanosphere lithography, in which nanoscale spheres are used as a mask to fabricate nanoparticle arrays. The result is a nanomesh comprising millions of hole-shaped nanoelectrodes patterned into a hexagonal array with channel lengths less than 100 nanometers.

By using a commercially available n-type organic semiconductor that self-assembles into supramolecular nanowires in combination with the nanomesh scaffold so that the nanowires become connected to the nanoelectrodes, the researchers have been able to fabricate a photovoltaic device with very promising characteristics.

One of the attractive properties of the device is that the polymer/nanowire p-n junction provides a fast photoresponse because the anode and cathode are quite close together. Another feature of this device is that it is possible to chemically modify the anode and cathode separately. This enables tailoring of interfaces that, in turn, makes it possible to replace calcium and aluminum cathodes. It also makes the use of transparent electrodes such as indium tin oxide unnecessary.

In future research, the team intends to optimize the device in a number of different areas, such as using polymer thin films to impart flexibility . The researchers are also considering the use of thinner dielectric layers to increase the photocurrent.

Porous silicon nanoparticles offer harmless theraphy and diagnostic solution for many types of cancer

Silicon Nanoparticles Provide Biocompatible Solution to Cancer Detection and Treatment

When it comes to cancer treatment and nanoparticles, the preference has been to use gold nanoparticlesSilicon nanoparticles, on the other hand, have been limited mainly to the realm of electronics applications.

Now researchers at Lomonosov Moscow State University and the Leibniz Institute of Photonic Technology in Germany have demonstrated that silicon nanoparticles can be applied to the diagnosis and treatment of cancer. The researchers claim that this work represents the first time nanoparticles have penetrated into diseased cells and completely dissolved after delivering their cancer treatment drug payload.

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Professor Shubhra Gangopadhyay of the University of Missouri holding plasmonic gratings.

Plasmonics Enable Optical Microscopes to Perform Like Electron Microscopes

Optical microscopes are  a key tool in biological studies. But because they are limited by approximately half the wavelength of light used (200 to 400 nanometers), they can’t resolve molecules that are typically much smaller than these dimensions. While electron microscopes can reach resolutions far below an optical microscope, they are large, expensive pieces of equipment that require a vacuum to operate, limiting the ability to examine live samples.

Now researchers at the University of Missouri have developed a way to make an optical microscope resolve images down to 65 nanometers. In the process, they may have extended access to high resolution imaging to a much larger group of scientists who may not have access to electron microscopes.

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Smart Sutures Integrate Microfluidics and Nanosensors

The role of nanomaterials in textiles has evolved from comparatively simple hydrophobic materials to the creation of textile electrodes that leverage graphene and the weaving of nanowires into t-shirts to make them into supercapacitors.

Now researchers at Tufts University have taken nanomaterials for wearable systems to a new level with the development of a “smart” thread consisting of nanoscale sensors and microfluidics. The thread could be used in sutures, providing critical information in medical treatments.

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A molybdenum disulfide tube wired together with carbon nanotubes for use as an electrode in a lithium ion battery

Molybendum Disulfide and Carbon Nanotubes Join Forces for a Super Li-ion Battery

The initial high hopes surrounding molybdenum disulfide’s (MoS2) potential in electronic applications were tempered somewhat when it was revealed that MoS2 contained traps—impurities or dislocations that can capture an electron or hole—that limit its electronic properties. Since then the two-dimensional material has been investigated for other applications, one of the most promising of which has been for use on the electrodes of lithium-ion (Li-ion) batteries where some research has indicated that it has three times the theoretical capacity of graphite.

However, even here MoS2 does not come without some challenges. Most notable among the problems with MoS2 anodes is the speed at which they begin to degrade and the low rate at which they discharge.

Now researchers at Nanyang Technological University in collaboration with a team at Hanyang University in South Korea have developed a solution that addresses these issues by using tubular structures of MoS2 that have been wired together by carbon nanotubes to enhance conductivity.

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NASA Eyes First Carbon Nanotube Mirrors for CubeSat Telescope

Some have dubbed NASA’s CubeSats "nanosatellites" because of their relatively small dimensions that are based on the size of a Beanie Baby box one of their inventors found in a store. The CubeSats are small, weighing in at just 1 to 10 kilograms, but they’re not nanoscale small.

While the CubeSats are not going to be shrunk down to the nanoscale any time soon, they now at least contain some nanotechnology. For the first time, researchers at NASA’s Goddard Space Flight Center have used carbon nanotubes in an epoxy resin to fabricate a mirror for a lightweight telescope on a CubeSat.

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Pores in a lithium-ion battery electrode align in a magnetic field

Magnetic Field Makes a Better Lithium-Ion Battery for Electric Vehicles

Researchers at MIT have developed a manufacturing approach for the electrode material of lithium-ion (Li-ion) batteries that should lead to a threefold higher area capacity for conventional electrodes. In the devices that they have fabricated thus far they have measured 12 milliamp hours per square centimeter (mAh cm2) versus the 4 mAh cm2 seen in conventional electrodes at normal charge-discharge rates.

The technique the MIT team developed involves using an external magnetic field to align pores in the electrode material in a particular way to achieve these much higher capacity numbers. And because of some of the unique properties of the resulting material, these Li-ion batteries may be far better suited for the requirements of electric vehicles (EVs).

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Atomically Thin Circuits Made From Graphene and Molybdenite

Atomically thin transistors and circuits made of graphene and molybdenum disulfide (molybdenite) can now be chemically assembled on a large scale, researchers say. Previous attempts to build circutis from 2-D materials involved placing materials precisely instead of growing them where they’re needed.

Researchers hope such atomically-thin devices will allow Moore’s Law to continue once it becomes impossible to make further progress using silicon. "A big drive for nanotechnology has been the search for new materials to replace silicon to meet Moore's law," says study senior author Xiang Zhang, a materials scientist at the University of California Berkeley.

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Graphene-Silicon Photodetector Could Enable the Internet of Things

While graphene has faced challenges in the field of digital logic because of its lack of an inherent band gap, it has been that very weakness that has attracted many researchers to exploring its use in optoelectronics. This lack of a band gap makes graphene an extreme broadband absorber, enabling photodetection for visible, infrared, and terahertz frequencies.

Now, in research supported by the European Commission’s €1 billion ($1.3 billion) 10-year project, the Graphene Flagship, a group of universities—including the University of Cambridge in the UK, The Hebrew University in Israel, and John Hopkins University in the United States—has successfully combined graphene with silicon on a chip to make “high-responsivity” Schottky barrier photodetectors

Such photodetectors are formed by a junction between metal and a semiconductor. Since photodetectors are a key building block of optoelectronic links, the result of this research could lead to far less energy being consumed to process and move information, a key achievement in realizing the potential of the Internet of Things (IoT), say the researchers.

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IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

Dexter Johnson
Madrid, Spain
Rachel Courtland
Associate Editor, IEEE Spectrum
New York, NY
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