Posts belonging to Category Nanocrystallometry

Lab-grown Diamonds

This shiny, sparkly diamond was made inside a laboratory – but it has the same chemical makeup as its counterpart found deep inside the earth.


All the composition is exactly the same. It is a real diamond. What we’ve done is we’ve just taken what’s happened in nature and just put it in a lab,” said  Kelly Good, Director of Marketing of Pure Grown Diamonds.

Essentially, all diamonds are carbon. And inside a laboratory, scientists are using a method called microwave plasma chemical vapour deposition to grow the stones from a diamond seed. They do it by creating a plasma ball made of hydrogen inside a growth chamber. Methane, which is a carbon source, is added. The carbon mix rains down on the diamond seeds, layer by layer, creating a large, rough diamond that is cut and polished. The process takes about 10 to 12 weeks. Marketers tout the lab-grown diamonds as an eco-friendly, conflict-free alternative to mined diamonds. “Our consumer is millennials, anybody who is getting engaged are really buying the lab-grown diamonds. They also like the fact of the environmental aspect of it. That it’s grown in a greenhouse. There is less soil being moved. We have a less carbon footprint,” explains Kelly Good.

While similar in appearance, there are differences. David Weinstein, Executive Director of the International  Gemological Institute (New York), comments: “I have a crystal, a diamond and I’m looking at it and I see a peridot crystal, a green peridot crystal, I know right away, this wasn’t created in a machine. So the inclusions can really be very telling as to what the origins of the material is. And that’s what our gemologists look for.”
While lab-grown gems have been around for decades, but it’s only recently that the science and technology have made it possible to grow large, gem quality stones. And according to a report by Morgan Stanley, the lab-grown diamond market could grow by about 15 percent by the year 2020.


How To Forge Graphene In 3D Shape

The wonder material graphene gets many of its handy quirks from the fact that it exists in two dimensions, as a sheet of carbon only one atom thick. But to actually make use of it in practical applications, it usually needs to be converted into a 3D form. Now, researchers have developed a new and relatively simple way to do just that, using lasers to “forge” a three-dimensional pyramid out of graphene.

This isn’t the first time graphene has been given an extra dimension. In 2015, researchers from the University of Illinois molded graphene into 3D structures by layering it onto shaped substrates, and early this year MIT scientists found that tubes of the stuff could be shaped into 3D coral-like structures 10 times stronger than steel but just five percent as dense. Rice University researchers have also recently made graphene foam and reinforced it with carbon nanotubes.

But this new technique, developed by researchers in Finland and Taiwan, might be an easier and faster method to make 3D graphene. By focusing a laser onto a fine point on a 2D graphene lattice, the graphene at that spot is irradiated and bulges outwards. A variety of three-dimensional shapes can be made by writing patterns with the laser spot, with the height of the shape controlled by adjusting the irradiation dose at each particular point.

The team illustrated that technique by deforming a sheet of graphene into a 3D pyramid, standing 60 nm high. That sounds pretty tiny, but it’s 200 times taller than the graphene sheet itself.

We call this technique optical forging, since the process resembles forging metals into 3D shapes with a hammer,” says Mika Pettersson, co-author of the study. “In our case, a laser beam is the hammer that forges graphene into 3D shapes. The beauty of the technique is that it’s fast and easy to use; it doesn’t require any additional chemicals or processing. Despite the simplicity of the technique, we were very surprised initially when we observed that the laser beam induced such substantial changes on graphene. It took a while to understand what was happening.”

The researchers initially assumed that the laser had “doped” the graphene, introducing impurities into the material, but after further examination they found that wasn’t the case.

When we first examined the irradiated graphene, we were expecting to find traces of chemical species incorporated into the graphene, but we couldn’t find any,” comments Wei Yen Woon, co-author of the study. “After some more careful inspections, we concluded that it must be purely structural defects, rather than chemical doping, that are responsible for such dramatic changes on graphene.

The scientists explain that the optically forged graphene is structurally sound, highlighting its potential for building 3D architectures out of the material for a wide range of applications. In this form, the graphene has different electronic and optical properties from its 2D counterpart.

The research was published in the journal Nano Letters.

Source: Academy of Finland

Graphene, Not Glass, Is The Key To Better Optics

A lens just a billionth of a metre thick could transform phone cameras. Researchers at Swinburne University in Melbourne, Australia, have created ultra-thin lenses that cap an optical fibre, and can produce images with the quality and sharpness of much larger glass lenses.

Compared with current lenses, our graphene lens only needs one film to achieve the same resolution,” says Professor Baohua Jia, a research leader at Swinburne’s Centre for Micro-Photonics. “In the future, mobile phones could be much thinner, without having to sacrifice the quality of their cameras. Our lens also allows infrared light to pass through, which glass lenses don’t.”

Producing graphene can be costly and challenging, so Baohua and her colleagues used a laser to pattern layers of graphene oxide (graphene combined with oxygen). By then removing the oxygen, they produced low-cost, patterned films of graphene, a thousand times thinner than a human hair. “By patterning the graphene oxide film in this way, its optical and electrical properties can be altered, which allowed us to place them in different devices,” she says.

Warm objects give off infrared light, so mobile phones with graphene lenses could be used to scan for hotspots in the human body and help in the early identification of diseases like breast cancer. By attaching the lens to a fibre optic tip, endoscopes — instruments that are currently several millimetres wide—could be made a million times smaller. The team is also investigating graphene’s amazing properties for their potential use as supercapacitors, capable of storing very large amounts of energy, which could replace conventional batteries.

Baohua’s work on graphene lenses was published in Nature Communications.


Big Data And Skyrmions

Today’s world, rapidly changing because of “big data”, is encapsulated in trillions of tiny magnetic objects magnetic bits – each of which stores one bit of data in magnetic disk drives.   A group of scientists from the Max Planck Institutes in Halle and Dresden have discovered a new kind of magnetic nano-object in a novel material that could serve as a magnetic bit with cloaking properties to make a magnetic disk drive with no moving parts – a Racetrack Memory – a reality in the near future.

Most digital data is stored in the cloud as magnetic bits within massive numbers of magnetic disk drives.  Over the past several decades these magnetic bits have shrunk by many orders of magnitude, reaching limits where the boundaries of these magnetic regions can have special properties.  In some special materials these boundaries – “magnetic domain walls” – can be described as being topological. What this means is that these walls can be thought of as having a special magical cloak – what is referred to by scientists as “topological protection”.   An important consequence is that such magnetic walls are more stable to perturbations than similar magnetic bits without topological protection that are formed in conventional magnetic materials.  Thus, these “topological magnetic objects could be especially useful for storing1”s and “0”s, the basic elements of digital data.   One such object is a “magnetic skyrmion” which is a tiny magnetic region, perhaps tens to hundreds of atoms wide, separated from a surrounding magnetic region by a chiral domain wall.  Until recently only one type of skyrmion has been found in which it is surrounded by a chiral domain wall that takes the same form in all directions.   But there have been predictions of several other types of skyrmions that were not yet observed.

Now in a paper published in Nature, scientists from Prof. Stuart Parkin’s NISE department at the Max Planck Institute for Microstructure Physics in Halle, Germany, have found a second class of skyrmions, what are called “anti-skyrmions”, in materials synthesized in Prof. Claudia Felser.   The scientists from Halle and Dresden have found these tiny magnetic objects in a special class of versatile magnetic compounds called Heusler compounds.   Of these Heusler compounds, a tiny subset have just the right crystal symmetry to allow for the possibility of forming anti-skyrmions but not skyrmions.

The special cloaking properties of skyrmions makes them of great interest for a radically new form of solid-state memorythe Racetrack Memory. In Racetrack Memory digital data is encoded within magnetic domain walls that are packed closely within nanoscopic magnetic wires.  One of the unique features of Racetrack Memory, which is distinct from all other memories, is that the walls are moved around the nanowires themselves using recent discoveries in spin-orbitronics domain walls.  Very short pulses of current move all the backwards and forwards along the nano-wires. The walls – the magnetic bits – can be read and written by devices incorporated directly into the nanowires themselves, thereby eliminating any mechanical parts.


SuperPowerful Tiny Device Converts Light Into Electricity

In today’s increasingly powerful electronics, tiny materials are a must as manufacturers seek to increase performance without adding bulk. Smaller also is better for optoelectronic devices — like camera sensors or solar cells —which collect light and convert it to electrical energy. Think, for example, about reducing the size and weight of a series of solar panels, producing a higher-quality photo in low lighting conditions, or even transmitting data more quickly.

However, two major challenges have stood in the way: First, shrinking the size of conventionally used “amorphousthin-film materials also reduces their quality. And second, when ultrathin materials become too thin, they are almost transparent — and actually lose some ability to gather or absorb light.

Now, in a nanoscale photodetector that combines both a unique fabrication method and light-trapping structures, a team of engineers from the University at Buffalo (UB) and the University of Wisconsin-Madison (UW-Madison) has overcome both of those obstacles. The researchers — electrical engineers Qiaoqiang Gan at UB, and Zhenqiang (Jack) Ma and Zongfu Yu at UW-Madison — described their device, a single-crystalline germanium nanomembrane photodetector on a nanocavity substrate, in the July 7, 2017, issue of the journal Science Advances.

This image shows the different layers of the nanoscale photodetector, including germanium (red) in between layers of gold or aluminum (yellow) and aluminum oxide (purple). The bottom layer is a silver substrate

We’ve created an exceptionally small and extraordinarily powerful device that converts light into energy,” says Gan, associate professor of electrical engineering in UB’s School of Engineering and Applied Sciences, and one of the paper’s lead authors. “The potential applications are exciting because it could be used to produce everything from more efficient solar panels to more powerful optical fibers.”

The idea, basically, is you want to use a very thin material to realize the same function of devices in which you need to use a very thick material,” says Ma, the Lynn H. Matthias Professor and Vilas Distinguished Achievement Professor in electrical and computer engineering at UW-Madison, also a lead author. Nanocavities are made up of an orderly series of tiny, interconnected molecules that essentially reflect, or circulate, light.

The new device is an advancement of Gan’s work developing nanocavities that increase the amount of light that thin semiconducting materials like germanium can absorb. It consists of nanocavities sandwiched between a top layer of ultrathin single-crystal germanium and a bottom, reflecting layer of silver.


Sion, The Solar-Powered Car

What has room for 6 passengers, an all-electric range of up to 155 miles (250 kilometers), and a body covered in solar panels that can add as many as 18 miles (30 kilometers) of driving a day from sunlight? That would be the Sono Motors Sion, an innovative solar-powered car from a team of German entrepreneurs that is scheduled to have its world debut on July 27 (2017).

The Sion project was able to move forward thanks to an Indiegogo crowdfunding campaign last year that raised over a half million dollars. More than 1,000 people have participated so far.

The car will have two versions. The Urban comes with a 14.4 kilowatt-hour battery pack. It has a range of about 75 miles (121 kilometers) and will cost $13,200. The Extender version has a 30 kilowatt-hour battery and a range of 155 miles (250 kilometers). Its target price is $17,600. Neither price includes the battery. Like the Renault Zoe, customers will either buy the battery separately or lease it. The leasing option gives owners the flexibility to upgrade the battery later as improvements in battery technology become available.

The hood, roof, and rear hatch of the Sion are covered with monocrystalline silicon cells that are 21% efficient. On a sunny day, they can generate enough electricity to add 18 miles of range. The solar cells are 8 millimeters thick and embedded in a polycarbonate layer that is shatterproof, weather resistant, and light in weight. The Sion can also be 80% charged using an AC outlet in about 30 minutes, according to company claims. No DC charging option is available. The car also comes with an outlet that can power electronic devices.

Inside, all the seats of the 5 door hatchback fold flat, offering multiple configurations for carrying passengers and cargo. There is a 10 inch center display and smartphone connectivity via WiFi or Bluetooth. The ventilation system is called breSono and incorporates a dollop of moss, which is said to act as a natural filter when an electrical charge is applied.

The company will offer an online maintenance and repair system it calls reSono. It allows owners to order parts online and comes with a video that shows them how to install the parts when they arrive.  Or they can take the car and the parts to any local auto repair shop facility to get them installed.


Perovskite Solar Cells Conversion Efficiency Rises Up To 20%

A new low-temperature solution printing technique allows fabrication of high-efficiency perovskite solar cells with large crystals intended to minimize current-robbing grain boundaries. The meniscus-assisted solution printing (MASP) technique boosts power conversion efficiencies to nearly 20 percent by controlling crystal size and orientation.

The process, which uses parallel plates to create a meniscus of ink containing the metal halide perovskite precursors, could be scaled up to rapidly generate large areas of dense crystalline film on a variety of substrates, including flexible polymers. Operating parameters for the fabrication process were chosen by using a detailed kinetics study of perovskite crystals observed throughout their formation and growth cycle.

We used a meniscus-assisted solution printing technique at low temperature to craft high quality perovskite films with much improved optoelectronic performance,” said Zhiqun Lin, a professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. “We began by developing a detailed understanding of crystal growth kinetics that allowed us to know how the preparative parameters should be tuned to optimize fabrication of the films.”

The new technique is reported in the journal Nature Communications.


Cellulose-based Ink For 3D Printing

Empa (Switzerland) researchers have succeeded in developing an environmentally friendly ink for 3D printing based on cellulose nanocrystals. This technology can be used to fabricate microstructures with outstanding mechanical properties, which have promising potential uses in implants and other biomedical applications.

Cellulose, along with lignin and hemicellulose, is one of the main constituents of wood. The biopolymer consists of glucose chains organized in long fibrous structures. In some places the cellulose fibrils exhibit a more ordered structure.

In order to produce 3D microstructured materials for composite applications, for instance, Empa researchers have been using a 3D printing method called “Direct Ink Writing” for the past year. During this process, a viscous substance – the printing ink – is squeezed out of the printing nozzles and deposited onto a surface, pretty much like a pasta machine. Empa researchers Gilberto Siqueira and Tanja Zimmermann from the Laboratory for Applied Wood Materials have now succeeded, together with Jennifer Lewis from Harvard University and André Studart from the ETH Zürich, in developing a new, environmentally friendly 3D printing ink made from cellulose nanocrystals (CNC).
The places with a higher degree of order appear in a more crystalline form. And it is these sections, which we can purify with acid, that we require for our research“, explains Siqueira. The final product is cellulose nanocrystals, tiny rod-like structures that are 120 nanometers long and have a diameter of 6.5 nanometers. And it is these nanocrystals that researchers wanted to use to create a new type of environmentally friendly 3D printing ink.They have now succeeded that  their new inks contain a full 20 percent CNC.

The biggest challenge was in attaining a viscous elastic consistency that could also be squeezed through the 3D printer nozzles“, says Siqueira. The ink must be “thick” enough so that the printed material stays “in shape” before drying or hardening, and doesn’t immediately melt out of shape again.


How Yo Make Sea Water Drinkable

Graphene-oxide membranes have attracted considerable attention as promising candidates for new filtration technologies. Now the much sought-after development of making membranes capable of sieving common salts has been achieved. New research demonstrates the real-world potential of providing clean drinking water for millions of people who struggle to access adequate clean water sources. Graphene-oxide membranes developed at the National Graphene Institute have already demonstrated the potential of filtering out small nanoparticles, organic molecules, and even large salts. Until now, however, they couldn’t be used for sieving common salts used in desalination technologies, which require even smaller sieves. Previous research at The University of Manchester found that if immersed in water, graphene-oxide membranes become slightly swollen and smaller salts flow through the membrane along with water, but larger ions or molecules are blocked.

The Manchester-based group have now further developed these graphene membranes and found a strategy to avoid the swelling of the membrane when exposed to water. The pore size in the membrane can be precisely controlled which can sieve common salts out of salty water and make it safe to drink.


Realisation of scalable membranes with uniform pore size down to atomic scale is a significant step forward and will open new possibilities for improving the efficiency of desalination technology,” says Professor Rahul Raveendran Nair.

The new findings from a group of scientists at The University of Manchester have been published in the journal Nature Nanotechnology.


Printable solar cells

A University of Toronto (U of T) Engineering innovation could make building printing cells as easy and inexpensive as printing a newspaper. Dr. Hairen Tan and his team have cleared a critical manufacturing hurdle in the development of a relatively new class of solar devices called perovskite solar cells. This alternative solar technology could lead to low-cost, printable solar panels capable of turning nearly any surface into a power generator.

Printable Perovskite SolarCell

Economies of scale have greatly reduced the cost of silicon manufacturing,” says University Professor Ted Sargent (ECE), an expert in emerging solar technologies and the Canada Research Chair in Nanotechnology and senior author on the paper. “Perovskite solar cells can enable us to use techniques already established in the printing industry to produce solar cells at very low cost. Potentially, perovskites and silicon cells can be married to improve efficiency further, but only with advances in low-temperature processes.”

Today, virtually all commercial solar cells are made from thin slices of crystalline silicon which must be processed to a very high purity. It’s an energy-intensive process, requiring temperatures higher than 1,000 degrees Celsius and large amounts of hazardous solvents.

In contrast, perovskite solar cells depend on a layer of tiny crystals — each about 1,000 times smaller than the width of a human hair — made of low-cost, light-sensitive materials. Because the perovskite raw materials can be mixed into a liquid to form a kind of ‘solar ink’, they could be printed onto glass, plastic or other materials using a simple inkjet process.


How To Color Textiles Without Polluting Environment

Fast fashion” might be cheap, but its high environmental cost from dyes polluting the water near factories has been well documented. To help stem the tide of dyes from entering streams and rivers, scientists report in the journal ACS Applied Materials & Interfaces a nonpolluting method to color textiles using 3-D colloidal crystals.

peacock feathers

Peacock feathers, opals and butterfly wings have inspired a new way to color voile fabrics without the pollutants of traditional dyes.

Dyes and pigments are chemical colors that produce their visual effect by selectively absorbing and reflecting specific wavelengths of visible light. Structural or physical colors — such as those of opals, peacock feathers and butterfly wings — result from light-modifying micro- and nanostructures. Bingtao Tang and colleagues from Universty of Maryland wanted to find a way to color voile textiles with structural colors without creating a stream of waste.

The researchers developed a simple, two-step process for transferring 3-D colloidal crystals, a structural color material, to voile fabrics. Their “dye” included polystyrene nanoparticles for color, polyacrylate for mechanical stability, carbon black to enhance color saturation and water. Testing showed the method could produce the full spectrum of colors, which remained bright even after washing. In addition, the team said that the technique did not produce contaminants that could pollute nearby water.


Reconfigurable Materials

Metamaterialsmaterials whose function is determined by structure, not composition — have been designed to bend light and sound, transform from soft to stiff, and even dampen seismic waves from earthquakes. But each of these functions requires a unique mechanical structure, making these materials great for specific tasks, but difficult to implement broadly. But what if a material could contain within its structure, multiple functions and easily and autonomously switch between them?

Researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Wyss Institute of Biologically Inspired Engineering at Harvard University have developed a general framework to design reconfigurable metamaterials. The design strategy is scale independent, meaning it can be applied to everything from meter-scale architectures to reconfigurable nano-scale systems such as photonic crystals, waveguides and metamaterials to guide heat.

In terms of reconfigurable metamaterials, the design space is incredibly large and so the challenge is to come up with smart strategies to explore it,” said Katia Bertoldi, John L. Loeb Associate Professor of the Natural Sciences at SEAS and senior author of the paper. “Through a collaboration with designers and mathematicians, we found a way to generalize these rules and quickly generate a lot of interesting designs.”

The research is published in Nature.