Entity

Time filter

Source Type

IPC
Marseille, France

At Warsaw's Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) a nanosensor has been developed for the continuous monitoring of changes in pH. Used as a scanning electrochemical microscope probe, it allows for the precise measurement of changes in acidity/alkalinity occurring over very small fragments of the surface of a sample immersed in a solution. The spatial resolution here is just 50 nm, and in the future, it can be reduced even further. "The ability to monitor changes in the acidity or alkalinity of solutions at the nanoscale, and thus over areas whose dimensions can be counted in billionths of a metre, is an important step toward better understanding of many chemical processes. The most obvious examples here are various kinds of catalytic reactions or pitting corrosion, which begins on very small fragments of a surface," explains Prof. Marcin Opallo (IPC PAS). Changes in the pH of solutions are due to reactions involving hydrogen ions (i.e. positively charged protons, H+) or hydroxide ions (negatively charged, OH-). These reactions interfere with the ratio between the numbers of ions of both types. The more protons there are, the more acidic the environment is; the more hydroxide ions, the more alkaline. The pH indicates the scale of the disturbance of neutrality. Its values are generally within the rangle of zero to 14, where in a neutral environment the value is seven; a pH of less than seven corresponds to acids, and higher values to alkalis. Measuring the pH of solutions is not generally difficult and part of standard laboratory and industrial practice. However, measuring changes in extremely small volumes—for example, directly in the vicinity of individual chemical molecules—is more difficult. To date, there are no instruments capable of detecting changes in pH at such a small, nanometric scale. "With our nanosensor we can measure the pH with a resolution similar to the diameter of the carbon electrode scanning over the surface of the sample, which is currently 50 nm. We determine the pH in the range of two to 12 to two decimal places, as well as being able to keep track of its changes, even dozens of times per second," says Dr. Wojciech Nogala (IPC PAS), one of the inventors. The preparation of the carbon nanoelectrode starts by heating up a thin quartz tube with a laser beam. At an appropriately selected temperature, quartz becomes malleable and the tube can be gently stretched, which results in reduced diameter. Finally, the process leads to the formation of a glass 'hair' with an outer diameter of approximately 100 nm and an inner tunnel with a diameter of approximately 50 nm. This pipette is then surrounded by an argon atmosphere. Next, a mixture of propane and butane is introduced into the pipette and pyrolysis occurs, i.e. decomposition at a high temperature. Carbon is progressively deposited on the inner walls of the pipette (the lack of oxygen prevents it from burning). Conducted carefully and for long enough, the pyrolysis completely fills the interior of the nanopipette with carbon, making it into a long and extremely thin rod. "The method of production of ultra-thin carbon electrodes has been known for several years and is in use in a few research centres in the world. However, an electrode obtained in this manner is not suitable for measuring pH. We had to modify it with something that would react with changes in the concentration of protons and hydroxide ions. To this end, we used a compound known as syringaldazine," explains Ph.D. student Magdalena Michalak (IPC PAS), the first author of the publication in the journal Analytical Chemistry, in which the construction of the nanosensor is described. The syringaldazine molecule can be electrochemically oxidized, resulting in the elimination of two electrons and two protons. Since the reaction is reversible, oxidized syringaldazine can be reduced to its original form by adding on two protons and two electrons from the environment. For the IPC PAS researchers, what was most important was the fact that the redox potential of the oxidation/reduction of syringaldazine depends on the pH of the solution and varies by 59 millivolts per pH unit. After the deposition of syringaldazine at the end of the carbon electrode, it is possible to carry out pH measurement by monitoring changes in the flow of current depending on the applied voltage. "It's easy to say, a little harder to do. We are talking about measuring picoamperes. Why, even the currents induced in the antenna of a radio receiver are a thousand times larger! So we have to carry out the measurements of pH changes inside a Faraday cage, which isolates the sensor and sample from the electromagnetic fields that are all around us," says Dr. Nogala. The pH mapping using the modified carbon nanoelectrode used SECMx software prepared by Prof. Gunther Wittstock from the University of Oldenburg. The long-term goal of the research at the IPC PAS is to develop methods for monitoring pH changes taking place in the vicinity of individual chemical molecules. Such sophisticated measurements would make it possible to, for example, resolve in what manner enzyme molecules lose their activity – whether the process occurs gradually in each molecule in the solution simultaneously, or whether individual molecules lose their activity suddenly. Explore further: pH measurements: How to see the real face of electrochemistry and corrosion?


News Article
Site: http://www.rdmag.com/rss-feeds/all/rss.xml/all

Even the most practiced performers experience anxiety on the stage. Empirical evidence suggests that having an audience can have either facilitative or detrimental effects on a performance. Now, neuroscientists from the Univ. of Sussex have identified the brain network system responsible for anxious flubs and stumbles. Using functional magnetic resonance neuroimaging (fMRI), the team observed the brains of people carrying out an activity. The task—which required study participants to exert a precise amount of force when gripping an object—was performed while the participant viewed video footage. “The presence or absence of social evaluation was experimentally manipulated by presenting each participant with video footage of two observers who appeared to be closely evaluating the participant’s own task performance in real-time (observed condition) or that of another participant (unobserved condition),” the researchers wrote in Scientific Reports. “We predicted that the observed condition would elicit a mild level of anxiety in our participants.” Participants, according to the researchers, reported heightened levels of anxiety when they perceived that they were being viewed. It caused them to grip the objects harder. Brain scans of the participants showed that the area of the brain responsible for fine sensorimotor functions—the inferior parietal cortex (IPC)—was deactivated when participants believed they were being viewed. The IPC works with the brain’s posterior superior temporal sulcus (pSTS) to create the action-observation network, which humans use to infer what other people are thinking based on gaze and facial expressions. According to Dr. Michiko Yoshie, the action-observation network could be related to performance anxiety, as people tend to care what others think of their performance. “Our data suggest that social evaluation can vary force output through the altered engagement of (the IPC); a region implicated in sensorimotor integration necessary for object manipulation, and a component of the action-observation network which integrates and facilitates performance of observed actions,” the researchers write. While this information may not directly help people overcome social anxiety, Yoshie said there are brain stimulation techniques that can help activate desired behavior, such as transcranial magnetic stimulation and transcranial direct current stimulation.


News Article
Site: http://phys.org/chemistry-news/

Crystals of kryptonite, a material deadly to Superman and his race, were supposed to have been created within the planet Krypton, most likely under very high pressure. The planet's name is derived from the element krypton, with the atomic number of 36, a noble gas considered to be incapable of forming stable chemical compounds. However, a publication in the journal Scientific Reports by a two-man team of theoretical chemists from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw, Poland, predict the synthesis of a new crystalline material in which atoms of krypton would be chemically bonded to another element. "The substance we are predicting is a compound of krypton with oxygen, not nitrogen. In the convention of the comic book it should, therefore, be called 'kryptoxide,' not 'kryptonite.' So if Superman's reading this, he can stay calm—at the moment, there's no cause for panic," says Dr. Patrick Zaleski-Ejgierd (IPC PAS). "Our krypton monoxide, KrO, probably does not exist in nature. According to current knowledge, the deep interiors of planets are the only place where there is sufficient pressure for its synthesis. Oxygen does not exist there, nor does krypton." Compounds of krypton have been produced in the laboratory under cryogenic conditions. They were, however, only single, linear and small molecules of the hydrogen-carbon-krypton-carbon-hydrogen type. The Polish chemists wondered if there were conditions in which krypton would not only bond chemically with another element, but also in which it would be capable of forming an extensive and stable crystal lattice. Their search, funded by an OPUS grant from the Polish National Science Centre, involved using genetic algorithms and models built on the so-called density functional theory. In the field of solid-state physics, this theory is a basic tool for the description and study of the world of chemical molecules. "Our computer simulations suggest that crystals of krypton monoxide will be formed at a pressure in the range of 300 to 500 million atmospheres. This is a high pressure, but it can be achieved even in today's laboratories, by skillfully squeezing samples in diamond anvils," says Ph.D. student Pawel M. Lata (IPC PAS). Crystal lattices are built from atoms or molecules arranged in space in an orderly manner. The smallest repetitive fragment of such structures, the basic 'building block,' is called a unit cell. In crystals of table salt, the unit cell has the shape of a cube in which the sodium and chlorine atoms, arranged alternately, are mounted on each corner, close enough to each other that they are bound by covalent (chemical) bonds. The unit cell of krypton monoxide is cuboid with a diamond base, with krypton atoms at the corners. In addition, in the middle of the two opposite side walls, there is one atom of krypton. "Where is the oxygen? On the side walls of the unit cell, where there are five atoms of krypton, they are arranged like the dots on a dice showing the number five. Single atoms of oxygen are located between the krypton atoms, but only along the diagonal—and only along one. Thus, on each wall with five krypton atoms, there are only two atoms of oxygen. Not only that, the oxygen is not exactly on the diagonal: One of the atoms is slightly offset from it in one direction and the other atom in the other direction," says Lata. In such an idiosyncratic unit cell, each atom of oxygen is chemically bound to the two nearest adjacent atoms of krypton. Zigzag chains of Kr/OKrO/Kr will therefore pass through the crystal of krypton monoxide, forming long polymer structures. Calculations indicate that crystals of this type of krypton monoxide should have the characteristics of a semiconductor. One can assume that they will be dark, and their transparency will not be great. Theorists from the IPC PAS have also found a second, slightly less stable compound of krypton: the tetroxide KrO . This material, which probably has properties typical of a metal, has a simpler crystalline structure and could be formed at a pressure exceeding 340 million atmospheres. After formation, the two kinds of krypton oxide crystals could probably exist at a somewhat lower pressure than that required for their formation. The pressure on earth, however, is so low that on our planet these crystals would undergo degradation immediately. "Reactions occurring at extremely high pressure are almost unknown, very, very exotic chemistry. We call it 'Chemistry on the Edge.' Often, the pressures needed to perform syntheses are so gigantic that at present, there is no point in trying to produce them in laboratories. In those cases, even methods of theoretic description fail! But what is most interesting here is the non-intuitiveness. From the very first to the last step of synthesis you never know what's going to happen," says Dr. Zaleski-Ejgierd. Explore further: On titanium oxide catalyst, certain atoms and molecules flee when light appears More information: Patryk Zaleski-Ejgierd et al. Krypton oxides under pressure, Scientific Reports (2016). DOI: 10.1038/srep18938


News Article | March 30, 2016
Site: http://www.techtimes.com/rss/sections/smartphone.xml

Ringing Bells Pvt. Ltd. continues to be indignant about its flagship Freedom 251 device despite various accusations from different parties. Earlier controversies that surrounded the release of the $4 Freedom 251 smartphone include rebranded Adcom smartphones distributed to media personnel during the phone's debut and the company's rather ambiguous and vague way of explaining how their phones can be priced so cheaply, not to menion their company is in the government's Make in India initiative. Now, a first information report (FIR) has been filed against Ringing Bells by Kirit Somaiya, leader of Bharatiya Janata Party (BJP) in India. The complaint accuses Ringing Bells of "cheating" as the company is allegedly violating Section 420 of the Indian Penal Code (IPC) and the Information Technology (IT) Acts. Somaiya believes the pricing of the phone is just not realistic and is accusing the company of committing fraud. The given specifications and features of the phone greatly exceed the selling price of the Freedom 251. Officials are assembling a team to investigate the matter after an initial report found the FIR had enough grounds to proceed. Ringing Bells has been required to submit documents for the inquiries pointed out in the FIR. The company states it is willing to oblige and it is in full cooperation with any government officials who need clarification from their side. Ringing Bells is seemingly ready to face and disprove any accusation. The company has also previously changed the mode of payments for preorders to a cash-on-delivery basis to further legitimize their business. Payments that had already been made were refunded. Such payments had been made through 3rd party banks and were held in escrow. In spite of these allegations directed at the company, not including all the assumptions and negative publicity, Ringing Bells seems unfazed. It promises to release the first batch of phones that will be delivered to users by the end of June 2016. Candidates were picked on a first come, first served basis and a status update on their company's Facebook page announced that they had sent out texts and e-mails to the users who had been picked. An estimated 50 lakh or 5 million units of the smartphone are expected to be sold both online and offline.


News Article
Site: http://phys.org/chemistry-news/

When you squeeze something, you usually expect it to shrink, particularly when the pressure exerted acts uniformly from all sides. However, there are materials which, when subjected to hydrostatic pressure, elongate slightly in one or two directions. During the search for optimal compounds for hydrogen storage, researchers made an accidental, albeit very interesting, discovery: Under increasing pressure, one of the tested materials elongated significantly. "Usually, the increase in dimensions observed in materials with negative compressibility subjected to high hydrostatic pressure is small. We are talking here about values of the order of a single percentage point or even less. We have found a material of very high negative compressibility, of up to 10% in one direction. Interestingly, the elongation occurred abruptly at a pressure of approx. 30 thousand atmospheres," says Dr. Taras Palasyuk (IPC PAS). Dr. Palasyuk is conducting research on materials subjected to hydrostatic pressures of one to several million atmospheres (the prefix hydro- means that the pressure acts on the material from all sides). Such high pressures are produced in the laboratory using diamond anvils, between which a micrometre-sized sample is placed. The sample is in a seal ensuring that the exerted pressure acts on the test material uniformly from all directions. To lead to an increase in pressure, the anvils are compressed by means of a screw. A ruby crystal placed next to the sample acts as a pressure gauge. It changes its mode of fluorescence depending on the pressure exerted upon it. The volume of the material samples exposed to increasing pressure decreases, which is usually associated with a reduction of all spatial dimensions. However, there are also atypical crystalline materials whose volume decreases during compression (because thermodynamics dictates that it must) while at the same time, the crystal elongates in one or two directions. The mechanism responsible for this elongation has always been of a geometric nature: Under pressure, individual elements of the crystal structure simply moved relative to each other to varying degrees in different directions. "In our laboratory, using laser light, we analyzed how the manners of vibration of molecules in the crystal changed with increasing pressure, and on this basis, we drew conclusions about the structure of the material. We quickly discovered that in the crystal we were examining, which was sodium amidoborane, the elongation could not be explained by changes in geometry alone," says Ph.D. student Ewelina Magos-Palasyuk, the lead author of the publication in the journal Scientific Reports. Sodium amidoborane is a relatively readily available compound with the chemical formula Na(NH BH ) forming transparent crystals with an orthorhombic structure. The results of research on crystals of this compound obtained at the IPC PAS using Raman spectroscopy were confronted with theoretical model predictions. It turned out that the negative compressibility of sodium amidoborane crystals has to be a consequence of the elongation of the chemical bonds between nitrogen, hydrogen, boron and nitrogen, caused by the abrupt formation of new hydrogen bonds between adjacent molecules in the crystal. "Sodium amidoborane is thus the first material known to us where the negative compressibility is primarily of a chemical nature," says Dr. Taras Palasyuk, stressing that in contrast to other materials in which the symmetry of the crystal structure changes under high pressure, there are no drastic changes in sodium amidoborane. He adds: "Our preliminary results, obtained by X-ray diffraction at the National Synchrotron Radiation Research Center in Taiwan, also confirm that the material retains its original symmetry. It is precisely because it does not have to rebuild that the increase in the linear dimensions occurs here in such an abrupt manner." The discovery of a previously unknown mechanism responsible for negative compressibility opens up interesting avenues in the search for new materials with similarly exotic physical properties. The significant, abrupt and reversible increase in length of the sodium amidoborane crystals at a clearly defined value of pressure makes the material an interesting candidate for such applications as components of pressure detectors of a threshold pressure of around 30 thousand atmospheres (in industry, pressures as high as 300 thousand atmospheres are used). Another potential application of sodium amidoborane could be active bulletproof vests, which would behave like airbags in a car under the influence of the sharp increase in pressure caused by the projectile strike. Explore further: Superman can start worrying—we've almost got the formula for kryptonite More information: Ewelina Magos-Palasyuk et al, Chemically driven negative linear compressibility in sodium amidoborane, Na(NH BH ), Scientific Reports (2016). DOI: 10.1038/srep28745

Discover hidden collaborations