Categories
ScienceDaily

Going small for big solutions: Sub-nanoparticle catalysts made from coinage elements as effective catalysts

Due to their small size, nanoparticles find varied applications in fields ranging from medicine to electronics. Their small size allows them a high reactivity and semiconducting property not found in the bulk states. Sub-nanoparticles (SNPs) have an extremely small diameter of around 1 nm, making them even smaller than nanoparticles. Almost all atoms of SNPs are available and exposed for reactions, and therefore, SNPs are expected to have extraordinary functions beyond the properties of nanoparticles, particularly as catalysts for industrial reactions. However, preparation of SNPs requires fine control of the size and composition of each particle on a sub-nanometer scale, making the application of conventional production methods near impossible.

To overcome this, researchers at the Tokyo Institute of Technology led by Dr. Takamasa Tsukamoto and Prof. Kimihisa Yamamoto previously developed the atom hybridization method (AHM) which surpasses the previous trials of SNP synthesis. Using this technique, it is possible to precisely control and diversely design the size and composition of the SNPs using a “macromolecular template” called phenylazomethine dendrimer. This improves their catalytic activity than the NP catalysts.

Now, in their latest study published in Angewandte Chemie International Edition, the team has taken their research one step further and has investigated the chemical reactivity of alloy SNPs obtained through the AHM. “We created monometallic, bimetallic, and trimetallic SNPs (containing one, combination of two, and combination of three metals respectively), all composed of coinage metal elements (copper, silver, and gold), and tested each to see how good of a catalyst each of them is,” reports Dr Tsukamoto. 

Unlike corresponding nanoparticles, the SNPs created were found to be stable and more effective. Moreover, SNPs showed a high catalytic performance even under the milder conditions, in direct contrast to conventional catalysts. Monometallic, bimetallic, and trimetallic SNPs demonstrated the formation of different products, and this hybridization or combination of metals seemed to show a higher turnover frequency (TOF). The trimetallic combination “Au4Ag8Cu16” showed the highest TOF because each metal element plays a unique role, and these effects work in concert to contribute to high reaction activity.

Furthermore, SNP selectively created hydroperoxide, which is a high-energy compound that cannot be normally obtained due to instability. Mild reactions without high temperature and pressure realized in SNP catalysts resulted in the stable formation of hydroperoxide by suppressing its decomposition.

When asked about the relevance of these findings, Prof Yamamoto states: “We demonstrate for the first time ever, that olefin hydroperoxygenation can been catalyzed under extremely mild conditions using metal particles in the quantum size range. The reactivity was significantly improved in the alloyed systems especially for the trimetallic combinations, which has not been studied previously.”

The team emphasized that because of the extreme miniaturization of the structures and the hybridization of different elements, the coinage metals acquired a high enough reactivity to catalyze the oxidation even under the mild condition. These findings will prove to be a pioneering key in the discovery of innovative sub-nanomaterials from a wide variety of elements and can solve energy crises and environmental problems in the years to come.

Story Source:

Materials provided by Tokyo Institute of Technology. Note: Content may be edited for style and length.

Go to Source
Author:

Categories
ScienceDaily

Discovery will allow more sophisticated work at nanoscale

The movement of fluids through small capillaries and channels is crucial for processes ranging from blood flow through the brain to power generation and electronic cooling systems, but that movement often stops when the channel is smaller than 10 nanometers.

Researchers led by a University of Houston engineer have reported a new understanding of the process and why some fluids stagnate in these tiny channels, as well as a new way to stimulate the fluid flow by using a small increase in temperature or voltage to promote mass and ion transport.

The work, published in ACS Applied Nano Materials, explores the movement of fluids with lower surface tension, which allows the bonds between molecules to break apart when forced into narrow channels, stopping the process of fluid transport, known as capillary wicking. The research was also featured on the journal’s cover.

Hadi Ghasemi, Cullen Associate Professor of Mechanical Engineering at UH and corresponding author for the paper, said this capillary force drives liquid flow in small channels and is the critical mechanism for mass transport in nature and technology — that is, in situations ranging from blood flow in the human brain to the movement of water and nutrients from soil to plant roots and leaves, as well as in industrial processes.

But differences in the surface tension of some fluids causes the wicking process — and therefore, the movement of the fluid — to stop when those channels are smaller than 10 nanometers, he said. The researchers reported that it is possible to prompt continued flow by manipulating the surface tension through small stimuli, such as raising the temperature or using a small amount of voltage.

Ghasemi said raising the temperature even slightly can activate movement by changing surface tension, which they dubbed “nanogates.” Depending on the liquid, raising the temperature between 2 degrees Centigrade and 3 degrees C is enough to mobilize the fluid.

“The surface tension can be changed through different variables,” he said. “The simplest one is temperature. If you change temperature of the fluid, you can activate this fluid flow again.” The process can be fine-tuned to move the fluid, or just specific ions within it, offering promise for more sophisticated work at nanoscale.

“The surface tension nanogates promise platforms to govern nanoscale functionality of a wide spectrum of systems, and applications can be foreseen in drug delivery, energy conversion, power generation, seawater desalination, and ionic separation,” the researchers wrote.

In addition to Ghasemi and first author Masoumeh Nazari, researchers involved with the project include Sina Nazifi, Zixu Huang, Tian Tong and Jiming Bao, all with the University of Houston, and Kausik Das and Habilou Ouro-Koura, both with the University of Maryland Eastern Shore.

Funding for the project came from the Air Force Office of Scientific Research, the National Science Foundation and the U.S. Department of Education.

Story Source:

Materials provided by University of Houston. Original written by Jeannie Kever. Note: Content may be edited for style and length.

Go to Source
Author:

Categories
ScienceDaily

What can you do with spiral graph? Help understand how galaxies evolve

Spiral structure is seen in a variety of natural objects, ranging from plants and animals to tropical cyclones and galaxies. Now researchers at the North Carolina Museum of Natural Sciences have developed a technique to accurately measure the winding arms of spiral galaxies that is so easy, virtually anyone can participate. This new and simple method is currently being applied in a citizen science project, called Spiral Graph, that takes advantage of a person’s innate ability to recognize patterns, and ultimately could provide researchers with some insight into how galaxies evolve.

Spiral galaxies, like our own Milky Way, make up approximately 70 percent of the galaxies in the nearby Universe. In many of these galaxies the difference in brightness between the winding arms and the inter-arm regions is very subtle, making it challenging for automated methods to measure. Even bright foreground stars can skew the automated analysis of a galaxy. Additionally, patterns in spiral galaxies are easily seen and followed by people but computer algorithms have a harder time determining where spirals begin and end, especially if they aren’t continuous.

The Spiral Graph project takes advantage of a time-honored short cut common in art classes — tracing. Ian Hewitt, Research Adjunct at the NC Museum of Natural Sciences, and Patrick Treuthardt, Assistant Head of the Museum’s Astronomy & Astrophysics Research Lab, tested their tracing method on a set of simple model images of spiral galaxies with known windings. They then traced out the spiral structure and measured the winding of the tracings with their own specially designed software, P2DFFT. When they compared their results against other approaches that involved an artificial intelligence program, fitting observed structure with mathematical models, or even directly inputting images into their own measurement software, none produced results as precise and accurate as their tracing method. A paper detailing this comparison appeared online on March 9, 2020. Spiral Graph is available on the Zooniverse.org platform for citizen science projects.

“These human-generated tracings give our software a boost so it can accurately measure how tightly wrapped the structure is,” Treuthardt says. “The degree of wrapping of the spiral arms is called the pitch angle. If a spiral pattern has very tightly wrapped arms, it has a small pitch angle. If it the spiral pattern is very open, it has a large pitch angle.” Why is pitch angle important? Because it relates to other parameters of the host galaxy that are more difficult and time consuming to measure, such as the mass of the black hole found in the nucleus, or dark matter content of the galaxy. “If we know the pitch angle we can quickly and easily estimate these parameters and identify interesting galaxies for more detailed, follow-up telescope observations,” Treuthardt adds.

Hewitt’s work on this study, and the Spiral Graph citizen science project, is especially rewarding since he started out as a volunteer working with Treuthardt. Although a long-time amateur astronomer, Hewitt retired from a career in industry to pursue astronomy full time. He later completed a degree in astronomy and began teaching and working on programming projects in the Museum’s Astronomy & Astrophysics Research Lab. “It’s been really exciting to get a chance to participate in this kind of research, but even better to have a part in enabling others to contribute to the efforts to better understand our Universe,” says Hewitt. And with an estimated 6,000 galaxies in their study, enlisting citizen scientists is a must.

Story Source:

Materials provided by North Carolina Museum of Natural Sciences. Note: Content may be edited for style and length.

Go to Source
Author:

Categories
3D Printing Industry

New video features ExOne’s 20+ years of metal binder jetting experience

As a binder jet additive manufacturing specialist, ExOne has expertise ranging across a variety of different materials. Working with sand, the company has become well established in the investment casting industry, providing a custom solution for the production of core tooling. On the other hand, with its metal 3D printing capabilities, ExOne is providing its […]

Go to Source
Author: Beau Jackson

Categories
ScienceDaily

The smell of old books could help preserve them

Old books give off a complex mélange of odors, ranging from pleasant (almonds, caramel and chocolate) to nasty (formaldehyde, old clothes and trash). Detecting early signs of paper degradation could help guide preservation efforts, but most techniques destroy the very paper historians want to save. Now, researchers reporting in ACS Sensors have developed an electronic nose that can non-destructively sniff out odors emitted by books of different paper compositions, conditions and ages.

Paper is made primarily of cellulose, along with other plant components, and additives that improve the paper’s properties. Cellulose is resistant to ageing, but the other paper components are much more vulnerable to degradation by heat, humidity and UV light. Before 1845, paper was made mainly from cotton and linen rags, which were relatively pure forms of cellulose and therefore quite stable. Then, in 1845, inventors developed a process to make paper from wood-pulp fibers. This paper is less durable than that made from cotton, but wood is cheaper and more readily available. In 1980, the advent of acid-free paper was a boon to preservationists because it degrades much more slowly than acidic wood-pulp paper. Marta Veríssimo, M. Teresa Gomes and colleagues wanted to develop an electronic nose that could non-destructively detect early signs of paper degradation from the volatile organic compounds (VOCs) books emit.

The researchers collected 19 books published from 1567 to 2016. They classified the books by time period, paper composition, color and visible state. Then, the researchers collected VOCs released from the books and detected the gases with an electronic nose containing six sensors that selectively bound different VOCs. The electronic nose clearly distinguished between paper from cotton or linen rags and paper from wood, as well as among books from three different time periods. Unexpectedly, some books published after 1990 still contained acidic paper, which the sensor discriminated from books with acid-free paper. And finally, the device sniffed out yellowing books, and new and used books from the same time period. The sensitive new method could help identify books in need of preservation, as well as help protect books from VOCs emitted by their neighbors on a shelf.

Story Source:

Materials provided by American Chemical Society. Note: Content may be edited for style and length.

Go to Source
Author:

Categories
ScienceDaily

Six galaxies undergoing sudden, dramatic transitions

Galaxies come in a wide variety of shapes, sizes and brightnesses, ranging from humdrum ordinary galaxies to luminous active galaxies. While an ordinary galaxy is visible mainly because of the light from its stars, an active galaxy shines brightest at its center, or nucleus, where a supermassive black hole emits a steady blast of bright light as it voraciously consumes nearby gas and dust.

Sitting somewhere on the spectrum between ordinary and active galaxies is another class, known as low-ionization nuclear emission-line region (LINER) galaxies. While LINERs are relatively common, accounting for roughly one-third of all nearby galaxies, astronomers have fiercely debated the main source of light emission from LINERs. Some argue that weakly active galactic nuclei are responsible, while others maintain that star-forming regions outside the galactic nucleus produce the most light.

A team of astronomers observed six mild-mannered LINER galaxies suddenly and surprisingly transforming into ravenous quasars — home to the brightest of all active galactic nuclei. The team reported their observations, which could help demystify the nature of both LINERs and quasars while answering some burning questions about galactic evolution, in the Astrophysical Journal on September 18, 2019. Based on their analysis, the researchers suggest they have discovered an entirely new type of black hole activity at the centers of these six LINER galaxies.

“For one of the six objects, we first thought we had observed a tidal disruption event, which happens when a star passes too close to a supermassive black hole and gets shredded,” said Sara Frederick, a graduate student in the University of Maryland Department of Astronomy and the lead author of the research paper. “But we later found it was a previously dormant black hole undergoing a transition that astronomers call a ‘changing look,’ resulting in a bright quasar. Observing six of these transitions, all in relatively quiet LINER galaxies, suggests that we’ve identified a totally new class of active galactic nucleus.”

All six of the surprising transitions were observed during the first nine months of the Zwicky Transient Facility (ZTF), an automated sky survey project based at Caltech’s Palomar Observatory near San Diego, California, which began observations in March 2018. UMD is a partner in the ZTF effort, facilitated by the Joint Space-Science Institute (JSI), a partnership between UMD and NASA’s Goddard Space Flight Center.

Changing look transitions have been documented in other galaxies — most commonly in a class of active galaxies known as Seyfert galaxies. By definition, Seyfert galaxies all have a bright, active galactic nucleus, but Type 1 and Type 2 Seyfert galaxies differ in the amount of light they emit at specific wavelengths. According to Frederick, many astronomers suspect that the difference results from the angle at which astronomers view the galaxies.

Type 1 Seyfert galaxies are thought to face Earth head-on, giving an unobstructed view of their nuclei, while Type 2 Seyfert galaxies are tilted at an oblique angle, such that their nuclei are partially obscured by a donut-shaped ring of dense, dusty gas clouds. Thus, changing look transitions between these two classes present a puzzle for astronomers, since a galaxy’s orientation towards Earth is not expected to change.

Frederick and her colleagues’ new observations may call these assumptions into question.

“We started out trying to understand changing look transformations in Seyfert galaxies. But instead, we found a whole new class of active galactic nucleus capable of transforming a wimpy galaxy to a luminous quasar,” said Suvi Gezari, an associate professor of astronomy at UMD, a co-director of JSI and a co-author of the research paper. “Theory suggests that a quasar should take thousands of years to turn on, but these observations suggest that it can happen very quickly. It tells us that the theory is all wrong. We thought that Seyfert transformation was the major puzzle. But now we have a bigger issue to solve.”

Frederick and her colleagues want to understand how a previously quiet galaxy with a calm nucleus can suddenly transition to a bright beacon of galactic radiation. To learn more, they performed follow-up observations on the objects with the Discovery Channel Telescope, which is operated by the Lowell Observatory in partnership with UMD, Boston University, the University of Toledo and Northern Arizona University. These observations helped to clarify aspects of the transitions, including how the rapidly transforming galactic nuclei interacted with their host galaxies.

“Our findings confirm that LINERs can, in fact, host active supermassive black holes at their centers,” Frederick said. “But these six transitions were so sudden and dramatic, it tells us that there is something altogether different going on in these galaxies. We want to know how such massive amounts of gas and dust can suddenly start falling into a black hole. Because we caught these transitions in the act, it opens up a lot of opportunities to compare what the nuclei looked like before and after the transformation.”

Unlike most quasars, which light up the surrounding clouds of gas and dust far beyond the galactic nucleus, the researchers found that only the gas and dust closest to the nucleus had been turned on. Frederick, Gezari and their collaborators suspect that this activity gradually spreads from the galactic nucleus — and may provide the opportunity to map the development of a newborn quasar.

“It’s surprising that any galaxy can change its look on human time scales. These changes are taking place much more quickly than we can explain with current quasar theory,” Frederick said. “It will take some work to understand what can disrupt a galaxy’s accretion structure and cause these changes on such short order. The forces at play must be very extreme and very dramatic.”

Go to Source
Author:

Categories
IEEE Spectrum

One Apollo 11 Experiment Is Still Going 50 Years Later

The Lunar Laser Ranging Experiment lets NASA precisely measure the distance between Earth and the moon