Tag Archives: Poland

Martini with your salad? an update on Janus particles and emulsification

Close to a year since I first posted about this research (my July 8, 2013 posting about oil, electricity, and emulsification), scientists have published their latest work on using electricity to control nanoparticles. A June 26, 2014 Polish Academy of Sciences press release (also on EurekAlert) provides this summary,

Everything depends on how you look at them. Looking from one side you will see one face; and when looking from the opposite side – you will see a different one. So appear Janus capsules, miniature, hollow structures, in different fragments composed of different micro- and nanoparticles. Theoreticians were able to design models of such capsules, but a real challenge was to produce them. Now, Janus capsules can be produced easily and at low cost.

Before describing the process for producing Janus capsules, an explanation of Janus (a Roman god) and the problem the scientists were trying to solve (from the press release),

Janus, the old Roman god of beginnings and transitions, attracted believers’ attention with his two faces, each looking to different direction of the world. Janus capsules – ‘bubbles’ made up of two shells stuck one another, each composed of micro- or nanoparticles of different properties – have been for some time attracting the researchers’ attention. They see in the capsules an excellent tool for transporting drugs and a vehicle leading to innovative materials. To have, however, Janus capsules generally accessible, efficient methods for their mass production must be developed. An important step in this direction is the achievement of researchers from the Norwegian and French research institutions and the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw, reported recently in one of the most reputable scientific journals: “Nature Communications”.

At present, it is not a problem to produce Janus spheres – round, entirely filled micro- and nanoobjects with one part having different properties than the other. Such spheres can be, for instance, produced by sticking together two drops of different substances. After merging, the new drop requires a sufficiently fast fixation only, e.g., by cooling it down or initiating polymerisation of its materials. For instance, Janus spheres are particles with white and black halves, used for image generation in electrophoretic displays incorporated in e-book reading devices.

“Janus capsules differ from Janus spheres: the former are hollow structures, and their partially permeable shell is made of colloidal particles. How to make such a ‘two-faced bubble’ using micro- and nanoparticles? Many researchers reflect on the problem. We proposed a really not complicated solution”, says Dr Zbigniew Rozynek (IPC PAS [Institute of Physical Chemistry Polish Academy of Sciences]), who experimentally studied Janus capsules during his postdoctoral training at Norwegian University of Science and Technology in Trondheim.

Here’s an illustration the researchers have provided,

Caption: These are typical capsules (mainly Janus capsules) obtained with the method described in the press release of the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw. Credit: adopted from Nat. Commun. 5, 3945 (2014)

Caption: These are typical capsules (mainly Janus capsules) obtained with the method described in the press release of the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw.
Credit: adopted from Nat. Commun. 5, 3945 (2014)

Here’s how the researchers solved their problem (from the press release),

In their experiments, an international team of researchers produced Janus capsules with drops of single millilitres in volume. The drops were coated, for instance, with polystyrene or glass nanoparticles with diameters of about 500 nm (billionth parts of a meter) or 1000 nm, respectively. Also differently coloured polyethylene particles were used.

The experiments were performed with oil drops suspended in another oil. To a so prepared environment micro- or nanoparticles of one type were placed and deposited on the surface of a selected drop. Then, particles of another type were brought to the surface of the second drop. Due to the action of capillary forces, the particles were durably kept on the surfaces of both drops, being approximately uniformly distributed.

When an external electric field was turned on, microflows were induced inside and outside the drops. The microflows transported the particles toward the electric ‘equator’. In this step, the packing of colloidal particles could be controlled by shaking the drops in a slowly alternating electric field. The way how the particles are packed is an important factor, as it determines the number and size of pores of the future capsule, and consequently the capsule permeability.

The microflows around the electric equators of the drops resulted in formation of a ring-shaped ribbon, composed of densely packed particles , whereas both electric ‘poles’ became particles-free regions. At the same time, the poles of each drop were acquiring opposite electric charges.

Opposite electric charges attract one another, so the drops with charged poles were heading to each other. In this step, the only thing to do was to convince both drops not only to adjoin with their poles, but actually to merge. For that purpose the long-known electrocoalescence was used: the drops were stimulated for faster merging by an electric field. Finally the drops electrocoalesced, resulting in the formation of a Janus capsule. Due to a dense packing of particles within the capsule the particles of different types virtually did not mix with each other.

It’s like the famous James Bond’s martini: it was always to be shaken, not stirred“, laughs Dr Rozynek. [emphasis mine]

The ultimate capsule appearance was determined by the number of particles deposited on the surfaces of initial drops. If the particles covered both drops with a uniform film, extending almost to the poles, the coalescence resulted in a non-spherical structure. When empty areas around the poles were suitably larger, the Janus capsules acquired a spherical shape. Finally, if the ribbons around the equators of the initial drops were narrow, the coalescence resulted in formation of a structure, which could be called a Janus ring.

The rings with two parts composed of two different types of particles provide interesting opportunities. They can be further stuck each other and produce more complex striped structures. The capsules could be then composed of alternately placed strips of particles, with each strip having different properties than its neighbours.

Janus capsules enable encapsulation of microobjects, nanoparticles or molecules, which must be protected against the environment because of their sensitivity or reactivity. Different properties of both capsule parts make it easier to control the movement of the capsules and the release of their contents. In view of these factors, Janus capsules may find numerous applications. The proposed method for producing the Janus capsules is potentially of great importance for pharmaceutical, dye or food industries, as well as for the development of materials engineering and medicine.

Here’s a link to and a citation for the paper,

Electroformation of Janus and patchy capsules by Zbigniew Rozynek, Alexander Mikkelsen, Paul Dommersnes, & Jon Otto Fossum. Nature Communications 5, Article number: 3945 doi:10.1038/ncomms4945 Published 23 May 2014

This is an open access paper,

Canada’s ‘nano’satellites to gaze upon luminous stars

The launch (from Yasny, Russia) of two car battery-sized satellites happened on June 18, 2014 at 15:11:11 Eastern Daylight Time according to a June 18, 2014 University of Montreal (Université de Montréal) news release (also on EurekAlert).

Together, the satellites are known as the BRITE-Constellation, standing for BRIght Target Explorer. “BRITE-Constellation will monitor for long stretches of time the brightness and colour variations of most of the brightest stars visible to the eye in the night sky. These stars include some of the most massive and luminous stars in the Galaxy, many of which are precursors to supernova explosions. This project will contribute to unprecedented advances in our understanding of such stars and the life cycles of the current and future generations of stars,” said Professor Moffat [Anthony Moffat, of the University of Montreal and the Centre for Research in Astrophysics of Quebec], who is the scientific mission lead for the Canadian contribution to BRITE and current chair of the international executive science team.

Here’s what the satellites (BRITE-Constellatio) are looking for (from the news release),

Luminous stars dominate the ecology of the Universe. “During their relatively brief lives, massive luminous stars gradually eject enriched gas into the interstellar medium, adding heavy elements critical to the formation of future stars, terrestrial planets and organics. In their spectacular deaths as supernova explosions, massive stars violently inject even more crucial ingredients into the mix. The first generation of massive stars in the history of the Universe may have laid the imprint for all future stellar history,” Moffat explained. “Yet, massive stars – rapidly spinning and with radiation fields whose pressure resists gravity itself – are arguably the least understood, despite being the brightest members of the familiar constellations of the night sky.” Other less-massive stars, including stars similar to our own Sun, also contribute to the ecology of the Universe, but only at the end of their lives, when they brighten by factors of a thousand and shed off their tenuous outer layers.

BRITE-Constellation is both a multinational effort and a Canadian bi-provincial effort,

BRITE-Constellation is in fact a multinational effort that relies on pioneering Canadian space technology and a partnership with Austrian and Polish space researchers – the three countries act as equal partners. Canada’s participation was made possible thanks to an investment of $4.07 million by the Canadian Space Agency. The two new Canadian satellites are joining two Austrian satellites and a Polish satellite already in orbit; the final Polish satellite will be launched in August [2014?].

All six satellites were designed by the University of Toronto Institute for Aerospace Studies – Space Flight Laboratory, who also built the Canadian pair. The satellites were in fact named “BRITE Toronto” and “BRITE Montreal” after the University of Toronto and the University of Montreal, who play a major role in the mission.  “BRITE-Constellation will exploit and enhance recent Canadian advances in precise attitude control that have opened up for space science  the domain of very low cost, miniature spacecraft, allowing a scientific return that otherwise would have had price tags 10 to 100 times higher,” Moffat said. “This will actually be the first network of satellites devoted to a fundamental problem in astrophysics.”

Is it my imagination or is there a lot more Canada/Canadian being included in news releases from the academic community these days? In fact, I made a similar comment in my June 10, 2014 posting about TRIUMF, Canada’s National Laboratory for Particle and Nuclear Physics where I noted we might not need to honk our own horns quite so loudly.

One final comment, ‘nano’satellites have been launched before as per my Aug. 6, 2012 posting,

The nanosatellites referred to in the Aug.2, 2012 news release on EurekALert aren’t strictly speaking nano since they are measured in inches and weigh approximately eight pounds. I guess by comparison with a standard-sized satellite, CINEMA, one of 11 CubeSats, seems nano-sized. From the news release,

Eleven tiny satellites called CubeSats will accompany a spy satellite into Earth orbit on Friday, Aug. 3, inaugurating a new type of inexpensive, modular nanosatellite designed to piggyback aboard other NASA missions. [emphasis mine]

One of the 11 will be CINEMA (CubeSat for Ions, Neutrals, Electrons, & MAgnetic fields), an 8-pound, shoebox-sized package which was built over a period of three years by 45 students from the University of California, Berkeley, Kyung Hee University in Korea, Imperial College London, Inter-American University of Puerto Rico, and University of Puerto Rico, Mayaguez.

This 2012 project had a very different focus from this Austrian-Canadian-Polish effort. From the University of Montreal news release,

The nanosatellites will be able to explore a wide range of astrophysical questions. “The constellation could detect exoplanetary transits around other stars, putting our own planetary system in context, or the pulsations of red giants, which will enable us to test and refine our models regarding the eventual fate of our Sun,” Moffatt explained.

Good luck!

Italians and Polish collaborate on nanoscale study of vanishing Da Vinci self-portrait

In addition to a new nondamaging technique to examine paintings (my June 2, 2014 post: Damage-free art authentication and spatially offset Raman spectroscopy [SORS]), there’s a new report in a June 3, 2014 news item on ScienceDaily about a nondamaging technique to examine paper such as the paper on which holds a Da Vinci self-portrait,

One of Leonardo da Vinci’s masterpieces, drawn in red chalk on paper during the early 1500s and widely believed to be a self-portrait, is in extremely poor condition. Centuries of exposure to humid storage conditions or a closed environment has led to widespread and localized yellowing and browning of the paper, which is reducing the contrast between the colors of chalk and paper and substantially diminishing the visibility of the drawing.

A group of researchers from Italy and Poland with expertise in paper degradation mechanisms was tasked with determining whether the degradation process has now slowed with appropriate conservation conditions — or if the aging process is continuing at an unacceptable rate.

Caption: This is Leonardo da Vinci's self-portrait as acquired during diagnostic studies carried out at the Central Institute for the Restoration of Archival and Library Heritage in Rome, Italy. Credit: M. C. Misiti/Central Institute for the Restoration of Archival and Library Heritage, Rome

Caption: This is Leonardo da Vinci’s self-portrait as acquired during diagnostic studies carried out at the Central Institute for the Restoration of Archival and Library Heritage in Rome, Italy.
Credit: M. C. Misiti/Central Institute for the Restoration of Archival and Library Heritage, Rome

The June 3, 2014 American Institute of Physics news release on EurekAlert provides more detail about the work,

… the team developed an approach to nondestructively identify and quantify the concentration of light-absorbing molecules known as chromophores in ancient paper, the culprit behind the “yellowing” of the cellulose within ancient documents and works of art.

“During the centuries, the combined actions of light, heat, moisture, metallic and acidic impurities, and pollutant gases modify the white color of ancient paper’s main component: cellulose,” explained Joanna Łojewska, a professor in the Department of Chemistry at Jagiellonian University in Krakow, Poland. “This phenomenon is known as ‘yellowing,’ which causes severe damage and negatively affects the aesthetic enjoyment of ancient art works on paper.”

Chromophores are the key to understanding the visual degradation process because they are among the chemical products developed by oxidation during aging and are, ultimately, behind the “yellowing” within cellulose. Yellowing occurs when “chromophores within cellulose absorb the violet and blue range of visible light and largely scatter the yellow and red portions — resulting in the characteristic yellow-brown hue,” said Olivia Pulci, a professor in the Physics Department at the University of Rome Tor Vergata.

To determine the degradation rate of Leonardo’s self-portrait, the team created a nondestructive approach that centers on identifying and quantifying the concentration of chromophores within paper. It involves using a reflectance spectroscopy setup to obtain optical reflectance spectra of paper samples in the near-infrared, visible, and near-ultraviolet wavelength ranges.

Once reflectance data is gathered, the optical absorption spectrum of cellulose fibers that form the sheet of paper can be calculated using special spectroscopic data analysis.

Then, computational simulations based on quantum mechanics — in particular, Time-Dependent Density Functional Theory, which plays a key role in studying optical properties in theoretical condensed matter physics — are tapped to calculate the optical absorption spectrum of chromophores in cellulose.

“Using our approach, we were able to evaluate the state of degradation of Leonardo da Vinci’s self-portrait and other paper specimens from ancient books dating from the 15th century,” said Adriano Mosca Conte, a researcher at the University of Rome Tor Vergata. “By comparing the results of ancient papers with those of artificially aged samples, we gained significant insights into the environmental conditions in which Leonardo da Vinci’s self-portrait was stored during its lifetime.”

Their work revealed that the type of chromophores present in Leonardo’s self portrait are “similar to those found in ancient and modern paper samples aged in extremely humid conditions or within a closed environment, which agrees with its documented history,” said Mauro Missori, a researcher at the Institute for Complex Systems, CNR, in Rome, Italy.

One of the most significant implications of their work is that the state of degradation of ancient paper can be measured and quantified by evaluation of the concentrations of chromophores in cellulose fibers. “The periodic repetition of our approach is fundamental to establishing the formation rate of chromophores within the self-portrait. Now our approach can serve as a precious tool to preserve and save not only this invaluable work of art, but others as well,” Conte noted.

Absolutely fascinating stuff to those of use who care about yellowing paper. (Having worked in an archives, I care deeply.) Here’s a link to and a citation for the study,

Visual degradation in Leonardo da Vinci’s iconic self-portrait: A nanoscale study by A. Mosca Conte, O. Pulci, M. C. Misiti, J. Lojewska, L. Teodonio1, C. Violante, and M. Missori. Appl. Phys. Lett. 104, 224101 (2014); http://dx.doi.org/10.1063/1.4879838

This is an open access study.

Chiral breathing at the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS)

An April 17, 2014 news item on ScienceDaily highlights some research about a polymer that has some special properties,

Electrically controlled glasses with continuously adjustable transparency, new polarisation filters, and even chemosensors capable of detecting single molecules of specific chemicals could be fabricated thanks to a new polymer unprecedentedly combining optical and electrical properties.

An international team of chemists from Italy, Germany, and Poland developed a polymer with unique optical and electric properties. Components of this polymer change their spatial configuration depending on the electric potential applied. In turn, the polarisation of transmitted light is affected. The material can be used, for instance, in polarisation filters and window glasses with continuously adjustable transparency. Due to its mechanical properties, the polymer is also perfectly suitable for fabrication of chemical sensors for selective detection and determination of optically active (chiral) forms of an analyte.

The research findings of the international team headed by Prof. Francesco Sannicolo from the Universita degli Studi di Milano were recently published in Angewandte Chemie International Edition.

“Until now, to give polymers chiral properties, chiral pendants were attached to the polymer backbone. In such designs the polymer was used as a scaffold only. Our polymer is exceptional, with chirality inherent to it, and with no pending groups. The polymer is both a scaffold and an optically active chiral structure. Moreover, the polymer conducts electricity,” comments Prof. Włodzimierz Kutner from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw, one of the initiators of the research.

An April 17, 2014 IPC PAS news release (also on EurrekAlert), which originated the news item, describes chirality and the breathing metaphor with regard to this new polymer,

Chirality can be best explained by referring to mirror reflection. If two varieties of the same object look like their mutual mirror images, they differ in chirality. Human hands provide perhaps the most universal example of chirality, and the difference between the left and right hand becomes obvious if we try to place a left-handed glove on a right hand. The same difference as between the left and right hand is between two chiral molecules with identical chemical composition. Each of them shows different optical properties, and differently rotates plane-polarised light. In such a case, chemists refer to one chemical compound existing as two optical isomers called enantiomers.

The polymer presented by Prof. Sannicolo’s team was developed on the basis of thiophene, an organic compound composed of a five-member aromatic ring containing a sulphur atom. Thiophene polymerisation gives rise to a chemically stable polymer of high conductivity. The basic component of the new polymer – its monomer – is made of a dimer with two halves each made of two thiophene rings and one thianaphthene unit. The halves are connected at a single point and can partially be rotated with respect to each other by applying electric potential. Depending on the orientation of the halves, the new polymer either assumes or looses chirality. This behaviour is fully reversible and resembles a breathing system, whereas the “chiral breathing” is controlled by an external electric potential.

The development of a new polymer was initiated thanks to the research on molecular imprinting pursued at the Institute of Physical Chemistry of the PAS. The research resulted, for instance, in the development of polymers used as recognising units (receptors) in chemosensors, capable of selective capturing of molecules of various analytes, for instance nicotine, and also melamine, an ill-reputed chemical detrimental to human health, used as an additive to falsify protein content in milk and dairy products produced in China.

Generally, molecular imprinting consists in creating template-shaped cavities in polymer matrices with molecules of interest used first as cavity templates. Subsequently these templates are washed out from the polymer. As a result, the polymer contains traps with a shape and size matching those of molecules of the removed template. To be used as a receptor in chemosensor to recognize analyte molecules similar to templates or templates themselves, the polymer imprinted with these cavities must show a sufficient mechanical strength.

“Three-dimensional networks we attempted to build at the IPC PAS using existing two-dimensional thiophene derivatives just collapsed after the template molecules were removed. That’s why we asked for assistance our Italian partners, specialising in the synthesis of thiophene derivatives. The problem was to design and synthesise a three-dimensional thiophene derivative that would allow us for cross-linking of our polymers in three dimensions. The thiophene derivative synthesised in Milan has a stable three-dimensional structure, and the controllable chiral properties of the new polymer obtained after the derivative was polymerised, turned out a nice surprise for all of us”, explains Prof. Kutner.

Here’s a link to and a citation for the paper,

Potential-Driven Chirality Manifestations and Impressive Enantioselectivity by Inherently Chiral Electroactive Organic Films by  Prof. Francesco Sannicolò1, Serena Arnaboldi, Prof. Tiziana Benincori, Dr. Valentina Bonometti, Dr. Roberto Cirilli, Prof. Lothar Dunsch, Prof. Włodzimierz Kutner, Prof. Giovanna Longhi, Prof. Patrizia R. Mussini, Dr. Monica Panigati, Prof. Marco Pierini, and Dr. Simona Rizzo. Angewandte Chemie International Edition Volume 53, Issue 10, pages 2623–2627, March 3, 2014. Article first published online: 5 FEB 2014 DOI: 10.1002/anie.201309585

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This article is behind a paywall.

Transition metal dichalcogenides (molybdenum disulfide and tungsten diselenide) rock the graphene boat

Anyone who’s read stories about scientific discovery knows that the early stages are characterized by a number of possibilities so the current race to unseat graphene as the wonder material of the nanoworld is a ‘business as usual’ sign although I imagine it can be confusing for investors and others hoping to make their fortunes. As for the contenders to the ‘wonder nanomaterial throne’, they are transition metal dichalcogenides: molybdenum disulfide and tungsten diselenide both of which have garnered some recent attention.

A March 12, 2014 news item on Nanwerk features research on molybdenum disulfide from Poland,

Will one-atom-thick layers of molybdenum disulfide, a compound that occurs naturally in rocks, prove to be better than graphene for electronic applications? There are many signs that might prove to be the case. But physicists from the Faculty of Physics at the University of Warsaw have shown that the nature of the phenomena occurring in layered materials are still ill-understood and require further research.

….

Researchers at the University of Warsaw, Faculty of Physics (FUW) have shown that the phenomena occurring in the crystal network of molybdenum disulfide sheets are of a slightly different nature than previously thought. A report describing the discovery, achieved in collaboration with Laboratoire National des Champs Magnétiques Intenses in Grenoble, has recently been published in Applied Physics Letters.

“It will not become possible to construct complex electronic systems consisting of individual atomic sheets until we have a sufficiently good understanding of the physics involved in the phenomena occurring within the crystal network of those materials. Our research shows, however, that research still has a long way to go in this field”, says Prof. Adam Babinski at the UW Faculty of Physics.

A March 12, 2014 Dept. of Physics University of Warsaw (FUW) news release, which originated the news item, describes the researchers’ ideas about graphene and alternative materials such as molybdenum disulfide,

“It will not become possible to construct complex electronic systems consisting of individual atomic sheets until we have a sufficiently good understanding of the physics involved in the phenomena occurring within the crystal network of those materials. Our research shows, however, that research still has a long way to go in this field”, says Prof. Adam Babiński at the UW Faculty of Physics.

The simplest method of creating graphene is called exfoliation: a piece of scotch tape is first stuck to a piece of graphite, then peeled off. Among the particles that remain stuck to the tape, one can find microscopic layers of graphene. This is because graphite consists of many graphene sheets adjacent to one another. The carbon atoms within each layer are very strongly bound to one another (by covalent bonds, to which graphene owes its legendary resilience), but the individual layers are held together by significantly weaker bonds (van de Walls [van der Waals] bonds). Ordinary scotch tape is strong enough to break the latter and to tear individual graphene sheets away from the graphite crystal.

A few years ago it was noticed that just as graphene can be obtained from graphite, sheets a single atom thick can similarly be obtained from many other crystals. This has been successfully done, for instance, with transition metals chalcogenides (sulfides, selenides, and tellurides). Layers of molybdenum disulfide (MoS2), in particular, have proven to be a very interesting material. This compound exists in nature as molybdenite, a crystal material found in rocks around the world, frequently taking the characteristic form of silver-colored hexagonal plates. For years molybdenite has been used in the manufacturing of lubricants and metal alloys. Like in the case of graphite, the properties of single-atom sheets of MoS2 long went unnoticed.

From the standpoint of applications in electronics, molybdenum disulfide sheets exhibit a significant advantage over graphene: they have an energy gap, an energy range within which no electron states can exist. By applying electric field, the material can be switched between a state that conducts electricity and one that behaves like an insulator. By current calculations, a switched-off molybdenum disulfide transistor would consume even as little as several hundred thousand times less energy than a silicon transistor. Graphene, on the other hand, has no energy gap and transistors made of graphene cannot be fully switched off.

The news release goes on to describe how the researchers refined their understanding of molybdenum disulfide and its properties,

Valuable information about a crystal’s structure and phenomena occurring within it can be obtained by analyzing how light gets scattered within the material. Photons of a given energy are usually absorbed by the atoms and molecules of the material, then reemitted at the same energy. In the spectrum of the scattered light one can then see a distinctive peak, corresponding to that energy. It turns out, however, that one out of many millions of photons is able to use some of its energy otherwise, for instance to alter the vibration or circulation of a molecule. The reverse situation also sometimes occurs: a photon may take away some of the energy of a molecule, and so its own energy slightly increases. In this situation, known as Raman scattering, two smaller peaks are observed to either side of the main peak.

The scientists at the UW Faculty of Physics analyzed the Raman spectra of molybdenum disulfide carrying on low-temperature microscopic measurements. The higher sensitivity of the equipment and detailed analysis methods enabled the team to propose a more precise model of the phenomena occurring in the crystal network of molybdenum disulfide.

“In the case of single-layer materials, the shape of the Raman lines has previously been explained in terms of phenomena involving certain characteristic vibrations of the crystal network. We have shown for molybdenum disulfide sheets that the effects ascribed to those vibrations must actually, at least in part, be due to other network vibrations not previously taken into account”, explains Katarzyna Gołasa, a doctorate student at the UW Faculty of Physics.

The presence of the new type of vibration in single-sheet materials has an impact on how electrons behave. As a consequence, these materials must have somewhat different electronic properties than previously anticipated.

Here’s what the rocks look like,

Molybdenum disulfide occurs in nature as molybdenite, crystalline material that frequently takes the characteristic form of silver-colored hexagonal plates. (Source: FUW)

Molybdenum disulfide occurs in nature as molybdenite, crystalline material that frequently takes the characteristic form of silver-colored hexagonal plates. (Source: FUW)

I am not able to find the published research at this time (March 13, 2014).

The tungsten diselenide story is specifically application-centric. Dexter Johnson in a March 11, 2014 post on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) describes the differing perspectives and potential applications suggested by the three teams that cooperated to produce papers united by a joint theme ,

The three research groups focused on optoelectronics applications of tungsten diselenide, but each with a slightly different emphasis.

The University of Washington scientists highlighted applications of the material for a light emitting diode (LED). The Vienna University of Technology group focused on the material’s photovoltaic applications. And, finally, the MIT [Massachusetts Institute of Technology] group looked at all of the optoelectronic applications for the material that would result from the way it can be switched from being a p-type to a n-type semiconductor.

Here are some details of the research from each of the institutions’ news releases.

A March 10, 2014 University of Washington (state) news release highlights their LED work,

University of Washington [UW] scientists have built the thinnest-known LED that can be used as a source of light energy in electronics. The LED is based off of two-dimensional, flexible semiconductors, making it possible to stack or use in much smaller and more diverse applications than current technology allows.

“We are able to make the thinnest-possible LEDs, only three atoms thick yet mechanically strong. Such thin and foldable LEDs are critical for future portable and integrated electronic devices,” said Xiaodong Xu, a UW assistant professor in materials science and engineering and in physics.

The UW’s LED is made from flat sheets of the molecular semiconductor known as tungsten diselenide, a member of a group of two-dimensional materials that have been recently identified as the thinnest-known semiconductors. Researchers use regular adhesive tape to extract a single sheet of this material from thick, layered pieces in a method inspired by the 2010 Nobel Prize in Physics awarded to the University of Manchester for isolating one-atom-thick flakes of carbon, called graphene, from a piece of graphite.

In addition to light-emitting applications, this technology could open doors for using light as interconnects to run nano-scale computer chips instead of standard devices that operate off the movement of electrons, or electricity. The latter process creates a lot of heat and wastes power, whereas sending light through a chip to achieve the same purpose would be highly efficient.

“A promising solution is to replace the electrical interconnect with optical ones, which will maintain the high bandwidth but consume less energy,” Xu said. “Our work makes it possible to make highly integrated and energy-efficient devices in areas such as lighting, optical communication and nano lasers.”

Here’s a link to and a citation for this team’s paper,

Electrically tunable excitonic light-emitting diodes based on monolayer WSe2 p–n junctions by Jason S. Ross, Philip Klement, Aaron M. Jones, Nirmal J. Ghimire, Jiaqiang Yan, D. G. Mandrus, Takashi Taniguchi, Kenji Watanabe, Kenji Kitamura, Wang Yao, David H. Cobden, & Xiaodong Xu. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.26 Published online 09 March 2014

This paper is behind a paywall.

A March 9, 2014 University of Vienna news release highlights their work on tungsten diselinide and its possible application in solar cells,

… With graphene as a light detector, optical signals can be transformed into electric pulses on extremely short timescales.

For one very similar application, however, graphene is not well suited for building solar cells. “The electronic states in graphene are not very practical for creating photovoltaics”, says Thomas Mueller. Therefore, he and his team started to look for other materials, which, similarly to graphene, can arranged in ultrathin layers, but have even better electronic properties.

The material of choice was tungsten diselenide: It consists of one layer of tungsten atoms, which are connected by selenium atoms above and below the tungsten plane. The material absorbs light, much like graphene, but in tungsten diselenide, this light can be used to create electrical power.

The layer is so thin that 95% of the light just passes through – but a tenth of the remaining five percent, which are absorbed by the material, are converted into electrical power. Therefore, the internal efficiency is quite high. A larger portion of the incident light can be used if several of the ultrathin layers are stacked on top of each other – but sometimes the high transparency can be a useful side effect. “We are envisioning solar cell layers on glass facades, which let part of the light into the building while at the same time creating electricity”, says Thomas Mueller.

Today, standard solar cells are mostly made of silicon, they are rather bulky and inflexible. Organic materials are also used for opto-electronic applications, but they age rather quickly. “A big advantage of two-dimensional structures of single atomic layers is their crystallinity. Crystal structures lend stability”, says Thomas Mueller.

Here’s a link to and a citation for the University of Vienna paper,

Solar-energy conversion and light emission in an atomic monolayer p–n diode by Andreas Pospischil, Marco M. Furchi, & Thomas Mueller. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.14 Published online 09 March 2014

This paper is behind a paywll.

Finally, a March 10, 2014 MIT news release details their work about material able to switch from p-type (p = positive) to a n-type (n = negative) semiconductors,

The material they used, called tungsten diselenide (WSe2), is part of a class of single-molecule-thick materials under investigation for possible use in new optoelectronic devices — ones that can manipulate the interactions of light and electricity. In these experiments, the MIT researchers were able to use the material to produce diodes, the basic building block of modern electronics.

Typically, diodes (which allow electrons to flow in only one direction) are made by “doping,” which is a process of injecting other atoms into the crystal structure of a host material. By using different materials for this irreversible process, it is possible to make either of the two basic kinds of semiconducting materials, p-type or n-type.

But with the new material, either p-type or n-type functions can be obtained just by bringing the vanishingly thin film into very close proximity with an adjacent metal electrode, and tuning the voltage in this electrode from positive to negative. That means the material can easily and instantly be switched from one type to the other, which is rarely the case with conventional semiconductors.

In their experiments, the MIT team produced a device with a sheet of WSe2 material that was electrically doped half n-type and half p-type, creating a working diode that has properties “very close to the ideal,” Jarillo-Herrero says.

By making diodes, it is possible to produce all three basic optoelectronic devices — photodetectors, photovoltaic cells, and LEDs; the MIT team has demonstrated all three, Jarillo-Herrero says. While these are proof-of-concept devices, and not designed for scaling up, the successful demonstration could point the way toward a wide range of potential uses, he says.

“It’s known how to make very large-area materials” of this type, Churchill says. While further work will be required, he says, “there’s no reason you wouldn’t be able to do it on an industrial scale.”

In principle, Jarillo-Herrero says, because this material can be engineered to produce different values of a key property called bandgap, it should be possible to make LEDs that produce any color — something that is difficult to do with conventional materials. And because the material is so thin, transparent, and lightweight, devices such as solar cells or displays could potentially be built into building or vehicle windows, or even incorporated into clothing, he says.

While selenium is not as abundant as silicon or other promising materials for electronics, the thinness of these sheets is a big advantage, Churchill points out: “It’s thousands or tens of thousands of times thinner” than conventional diode materials, “so you’d use thousands of times less material” to make devices of a given size.

Here’s a link to and a citation for the MIT paper,

Optoelectronic devices based on electrically tunable p–n diodes in a monolayer dichalcogenide by Britton W. H. Baugher, Hugh O. H. Churchill, Yafang Yang, & Pablo Jarillo-Herrero. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.25 Published online 09 March 2014

This paper is behind a paywall.

These are very exciting, if not to say, electrifying times. (Couldn’t resist the wordplay.)

Carbon dioxide as a source for new nanomaterials

Polish researchers have made a startling suggestion (from a Jan. 23, 2014 news item on Nanowerk),

In common perception, carbon dioxide is just a greenhouse gas, one of the major environmental problems of mankind. For Warsaw chemists CO2 became, however, something else: a key element of reactions allowing for creation of nanomaterials with unprecedented properties.

In reaction with carbon dioxide, appropriately designed chemicals allowed researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw and the Faculty of Chemistry, Warsaw University of Technology, (WUT) for production of unprecedented nanomaterials.

Here’s an image the researchers use to illustrate their work,

Yellow tennis balls, spatially integrated in an adamant-like structure, symbolise crystal lattice of the microporous material resulting from self-assembly of nanoclusters. Orange balls imitate gas molecules that can adsorb in this material. The presentation is performed by Katarzyna Sołtys, a doctoral student from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw. (Source: IPC PAS, Grzegorz Krzyżewski).

Yellow tennis balls, spatially integrated in an adamant-like structure, symbolise crystal lattice of the microporous material resulting from self-assembly of nanoclusters. Orange balls imitate gas molecules that can adsorb in this material. The presentation is performed by Katarzyna Sołtys, a doctoral student from the Institute of Physical Chemistry of the Polish Academy of Sciences in Warsaw. (Source: IPC PAS, Grzegorz Krzyżewski).

The Jan. 23, 2014 IPC news release, which originated the news item, describes the work in more detail,

Carbon dioxide (CO2) is a natural component of Earth’s atmosphere. It is the most abundant carbon-based building block, and is involved in the synthesis of glucose, an energy carrier and building unit of paramount importance for living organisms.

“Carbon dioxide has been for years used in industrial synthesis of polymers. On the other hand, there has been very few research papers reporting fabrication of inorganic functional materials using CO2”, says Kamil Sokołowski, a doctoral student in IPC PAS.

Prof. Lewiński’s [Janusz Lewiński (IPC PAS, WUT)] group has shown that appropriately designed precursor compounds in reaction with carbon dioxide lead to fabrication of a microporous material (with pore diameters below 2 nm) resulting from self-assembly of luminescent nanoclusters. Novel microporous material, composed of building blocks with zinc carbonate core encapsulated in appropriately designed organic shell (hydroxyquinoline ligands), is highly luminescent, with photoluminescence quantum yield significantly higher than those of classical fluorescent compounds used in state-of-the-art OLEDs.

“Using carbon dioxide as a building block we were able to construct a highly porous and really highly luminescent material. Can it be used for construction of luminescent diodes or sensing devices? The discovery is new, the research work on the novel material is in progress, but we are deeply convinced that the answer is: yes”, says Sokołowski.

Already now it can be said that the novel material enjoys considerable interest. Polish and international patent applications were filed for the invention and the implementation work in cooperation with a joint venture company is in progress.

The design of precursors was inspired by nature, in particular by the binding of carbon dioxide in enzymatic systems of carbonic anhydrase, an enzyme responsible for fast metabolism of CO2 in human body. Effective enzyme activity is based on its active centre, where a hydroxyzinc (ZnOH) type reaction system is located.

“A hydroxyzinc reaction system occurs also in molecules of alkylzinc compounds, designed by us and used for fixation of carbon dioxide”, explains Sokołowski and continues: “These compounds are of particular interest for us, because in addition to hydroxyl group they contain also a reactive metal-carbon bond. It means that both the first and the second reaction system can participate in consecutive chemical transformations of such precursors”.

The research related to the chemistry of alkylhydroxyzinc compounds has an over 150 years of history and its roots are directly connected to the birth of organometallic chemistry. It was, however, only in 2011 and 2012 when Prof. Lewiński’s group has presented the first examples of stable alkylhydroxyzinc compounds obtained as a result of rationally designed synthesis.

The strategy for materials synthesis using carbon dioxide and appropriate alkylhydroxyzinc precursors, discovered by the researchers from Warsaw, seems to be a versatile tool for production of various functional materials. Depending on the composition of the reagents and the process conditions, a mesoporous material (with pore diameter from 2 to 50 nm) composed of zinc carbonate nanoparticles or multinuclear zinc nanocapsules for prospective applications in supramolecular chemistry can be obtained in addition to the material described above.

Further research of Prof. Lewiński’s group has shown that the mesoporous materials based on ZnCO3-nanoparticles can be transformed into zinc oxide (ZnO) aerogels. Mesoporous materials made of ZnO nanoparticles with extended surface can be used as catalytic fillings, allowing for and accelerating reactions of various gaseous reagents. Other potential applications are related to semiconducting properties of zinc oxide. That’s why the novel materials can be used in future in photovoltaic cells or as a major component of semiconductor sensing devices.

Good luck to the researchers as they find ways to turn a greenhouse gas into something useful.

Shining a light on Poland’s nanotechnology effort

Last week I managed to mention Mongolia’s nanotechnology center (my Nov. 29, 2013 posting) and now I get to feature Poland here thanks to a Nov. 29, 2013 news item (also from last week) on Nanowerk,

Strengthening the nanotechnology capabilities of a key institute in Poland will enable the country to upgrade research on biomaterials and alternative energy. It will also help further integrate the country in the European Research Area (ERA).
Nanotechnology has been instrumental in creating many new materials and devices that offer numerous applications from biomaterials to alternative energy, representing an important driver of competitiveness within the ERA. The EU-funded project

‘Nanotechnology, biomaterials and alternative energy source for ERA [European Research Area] integration’ (NOBLESSE) is supporting Poland in strengthening its research capabilities in this pivotal field.

To achieve its aims, NOBLESSE is procuring new equipment for the academy, in addition to strengthening links with other institutes, promoting twinning activities and enhancing knowledge transfer. …

Already, the project team has installed an advanced scanning electron microscope, created a new laboratory in the IPC PAS, the Mazovia Center for Surface Analysis (which is one of the most advanced in Europe), and built an open-access Electronic Laboratory Equipment Database (ELAD) that documents research equipment available in specialised laboratories across Poland.

There is more about the NOBLESSE project from this webpage: http://ec.europa.eu/research/infocentre/article_en.cfm?id=/research/star/index_en.cfm?p=ss-noblesse&calledby=infocentre&item=Energy&artid=28137&caller=SuccessStories (article published Nov. 15, 2012),

The use and control of nano-structured materials is of great importance for the development of new environmentally friendly materials, more efficient energy sources and biosensors for medical analysis. The European Noblesse project is boosting a Polish academy’s capabilities to research these developments.

… Such is the scope for the development and application of nanotechnology that nano-structured materials are in high demand. To meet this demand, nano-science institutes need to rise to the challenges that modern society presents.

This is one of the driving forces behind the Noblesse project which aims to establish the Institute of Physical Chemistry, Polish Academy of Sciences (IPC-PAS) as an integrated partner and respected participant in the European nano-science community.

Through a combination of newly purchased, state-of-the-art equipment – financed by EU FP7 funding – and a programme of recruitment and training, Noblesse promises to position IPC-PAS as a leading research centre in Europe and beyond.

Significant progress

The project has already made great strides towards bringing new nanotechnology applications to the market place and in promoting the career development of a team of young, dedicated researchers in the field.

“In the first year of the project, we filed 49 patent applications, 25 of them abroad – most of which are nanotechnology patents,” says Professor Robert Holyst, the project coordinator. “I am not aware of any institute in Poland filing more patent applications than us at the moment.

“We have also established two spin-off companies, thanks to the valuable influence of our advisory board members from industry,” he adds. Tomasz Tuora, who is on the advisory board of the Noblesse project, is the main investor in Scope Fluidics Ltd and Curiosity Diagnostics Ltd, Prof. Holyst explains. “While the Noblesse grant did not promise to set up spin-off companies in the Institute, we did promise to collaborate and develop ties with industry,” he says.

According to Prof. Holyst, the two companies plan to make products for the medical sector and have each employed between 10 and 20 scientists to develop new nanotechnology applications.

The creation of spin-off companies from IPC-PAS is unlikely to end there if an application for a €1.3 million-grant from the NCBIR, the Polish funding agency for applied research, is successful. “We are currently applying for this grant to develop and later commercialise the SERS (surface enhanced resonance spectroscopy) platform for molecular diagnostics,” Prof. Holyst explains. “If we are successful in our application, we’ll establish a new spin-off company for this purpose.”

,The 2013 news item on Nanowerk does not mention the commercialization project referred to in the 2012 article. Good luck to the NOBLESSE team and I look forward to hearing more about the nanotechnology effort in Poland.

Batteries that breathe

Researchers at the Polish Academy of Sciences Institute of Physical Chemistry have constructed a biobattery that breathes. The device could be used in medication applications as the researchers note in the Mar. 7, 2013 news release on EurekAlert,

People are increasingly taking advantage of devices supporting various functions of our bodies. Today they include cardiac pacemakers or hearing aids; tomorrow it will be contact lenses with automatically changing focal length or computer-controlled displays generating images directly in the eye. None of these devices will work if not coupled to an efficient and long-lasting power supply source. The best solution seems to be miniaturised biofuel cells consuming substances naturally occurring in human body or in its direct surrounding.

Researchers from the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw developed an efficient electrode for the use in construction of biofuel cells or zinc-oxygen biobatteries. After installation in a cell, the new biocathode generates a voltage, during many hours, that is higher than that obtained in existing power sources of similar design. The most interesting is that the device is air-breathing: it works at full efficiency when it can take oxygen directly from the air.

Here’s some of the reasoning which underlies this project’s approach to the challenge of creating better batteries for implantable medical devices (from the news release),

Common batteries and rechargeable batteries are unsuitable to power implants inside the human body as they use strong bases or acids. These agents can on no account get into the body. The battery housing must be therefore absolutely tight. But in line with reducing the battery size, it must be better isolated. In extreme cases, the weight of the housing of a common, miniaturised battery would be even a few dozen times greater than the weight of the battery’s active components that generate electricity. And here biofuel cells offer an essential advantage: they do not require housing. To get electricity, it is enough to insert the electrodes into the body.

“One of the most popular experiments in electrochemistry is to make a battery by sticking appropriately selected electrodes into a potato. We are doing something similar, the difference is that we are focusing on biofuel cells and the improvement of the cathode. And, of course, to have the whole project working, we’d rather replace the potato with… a human being”, says Dr Martin Jönsson-Niedziółka (IPC PAS).

Here’s what the researchers decided to do,

In the experiments, Dr Jönsson-Niedziółka’s group uses zinc-oxygen batteries. The principle of their operation is not new. The batteries constructed in this way had been popular before the time of alkaline power sources came. “At present, many laboratories work on glucose-oxygen biofuel cells. In the best case they generate a voltage of 0.6-0.7 V. A zinc-oxygen biobattery with our cathode is able to generate 1.75 V for many hours.”, says Adrianna Złoczewska, a PhD student at the IPC PAS, whose research has been supported under the International PhD Projects Programme of the Foundation for Polish Science.

The main component of the biocathode developed at the IPC PAS is an enzyme surrounded by carbon nanotubes and encapsulated in a porous structure – a silicate matrix deposited on an oxygen permeable membrane. “Our group had been working for many years on techniques that were necessary to construct the cathode using enzymes, carbon nanotubes and silicate matrices”, stresses Prof. Marcin Opałło (IPC PAS).

An electrode so constructed is installed in a wall of a small container. To have the biofuel cell working, it is enough to pour an electrolyte (here: a solution containing hydrogen ions) and insert the zinc electrode in the electrolyte. The pores in the silicate matrix enable oxygen supply from the air and H+ ions from the solution to active centres of the enzyme, where oxygen reduction takes place. Carbon nanotubes facilitate transport of electrons from the surface of the semipermeable membrane.

A cell with the new biocathode is able to supply power with a voltage of 1.6 V, for a minimum one and a half of a week. The cell efficiency decreases with time, likely because of gradual deactivation of the enzyme on the biocathode. “Here not everything is dependent on us, but on the progress in biotechnology. The lifetime of a biofuel cells with our biocathode could be significantly prolonged, if the enzyme regeneration processes are successfully developed”, says Dr Jönsson-Niedziółka.

In the experiments carried out so far, a stack of four batteries connected in series successfully powered a lamp composed of two LEDs. Before, however, the biofuel cells based on the design developed at the IPC PAS get popularised, the researchers must solve the problem of relatively low electric power that is common to all types of biofuel cells.

I have mentioned similar projects in two previous postings, long ago. The first project was a vampire battery (a battery for implantable medical devices that powers itself with blood) mentioned in an April 3, 2009 posting. The second project was to power batteries from harvested mechanical energy from heart beats, breathing, vocal cord vibrations, and more and that was mentioned in a July 12, 2010 posting.

“It is more important to have beauty in one’s equations than to have them fit experiment” and nano protection against nerve agents

Michael Berger’s Nov. 7, 2012 Nanowerk Spotlight article about nanoporous adsorbents and protection against toxic nerve agents features Dr. Piotr Kowalczyk, a Senior Research Fellow at the Nanochemistry Research Institute at Curtin University of Technology in Australia, quoting English theoretical physicist, Paul Dirac,

“Some of my colleagues asked me if I believe in our theoretical results” says Kowalczyk. “The great physicist Paul Dirac used to say: ‘This result is too beautiful to be false; it is more important to have beauty in one’s equations than to have them fit experiment’.”

“And I truly believe that our theoretical results have to be correct – within the assumed model of nanopores – because they are so simple and beautiful” he concludes.

Kowalczyk is discussing some of  his latest work on protection against toxic nerve agents (Note: I have removed a link),

In a paper published in the October 31, 2012 online edition of Physical Chemistry Chemical Physics (“Screening of Carbonaceous Nanoporous Materials for Capture of Nerve Agents”), an international team led by Kowalczyk and Alexander V Neimark, a professor at Rutgers University, together with scientists from the Physicochemistry of Carbon Materials Research Group at Nicolaus Copernicus University in Poland, is shedding new light on the selection of an optimal nanomaterial for capturing highly volatile nerve agents.

Berger’s article gives some context for this research,

Protection against nerve agents – such as tabun, sarin, soman, VX, and others – is a major terrorism concern of security experts. Nerve agents, which attack the nervous system of the human body, are clear and colorless or slightly colored liquids and may have no odor or a faint, sweetish smell. They evaporate at various rates and are denser than air. Current methods to detect nerve agents include surface acoustic wave sensors; conducting polymer arrays; vector machines; and the most simple: color change paper sensors. Most of these systems have have certain limitations including low sensitivity and slow response times.

You can find more detail about nanopores and toxic nerve agents in Berger’s article.