Archive for the ‘Physical’ Category

Highlights from themed issues on ionic liquids

Ionic liquids ChemComm web themed issueCrystal engineering with ionic liquids CrystEngComm CollectionInterfaces of ionic liquids PCCP Themed issue

The field of ionic liquids has seen phenomenal growth in recent years, with the topic spanning a variety of disciplines across the chemical sciences. The recent themed issues from ChemComm, PCCP and CrystEngComm showcase some of the latest developments from a range of scientific subjects utilising the unique properties of ionic liquids.

Highlights from these themed issues include the articles below, which are free to download until the 24th August. You can also access the full themed issues by clicking on the buttons above.

CrystEngComm journal cover imageIonic liquids as crystallisation media for inorganic materials Ejaz Ahmed, Joachim Breternitz, Matthias Friedrich Groh and Michael Ruck, CrystEngComm, 2012, 14, 4874-4885

Ionic liquids in confined geometries Susan Perkin, Phys. Chem. Chem. Phys., 2012, 14, 5052-5062

Fluorescence monitoring of ionic liquid-facilitated biopolymer mobilization and reorganization Luke M. Haverhals, Laura M. Nevin, Matthew P. Foley, E. Kathryn Brown, Hugh C. De Long and Paul C. Trulove, Chem. Commun., 2012, 48, 6417-6419

Hofmeister effects of ionic liquids in protein crystallization: Direct and water-mediated interactions Magdalena Kowacz, Abhik Mukhopadhyay, Ana Luísa Carvalho, José M. S. S. Esperança, Maria J. Romão and Luís Paulo N. Rebelo, CrystEngComm, 2012, 14, 4912-4921

Influence of the ionic liquid/gas surface on ionic liquid chemistry Kevin R. J. Lovelock, Phys. Chem. Chem. Phys., 2012, 14, 5071-5089

ChemComm cover imageOptically responsive switchable ionic liquid for internally-referenced fluorescence monitoring and visual determination of carbon dioxide Shubha Pandey, Sheila N. Baker, Siddharth Pandey and Gary A. Baker, Chem. Commun., 2012, 48, 7043-7045

Supramolecular architectures of symmetrical dicationic ionic liquid based systems Haregewine Tadesse, Alexander J. Blake, Neil R. Champness, John E. Warren, Pierre J. Rizkallah and Peter Licence, CrystEngComm, 2012, 14, 4886-4893

New insights into the interface between a single-crystalline metal electrode and an extremely pure ionic liquid: slow interfacial processes and the influence of temperature on interfacial dynamics Marcel Drüschler, Natalia Borisenko, Jens Wallauer, Christian Winter, Benedikt Huber, Frank Endres and Bernhard Roling, Phys. Chem. Chem. Phys., 2012, 14, 5090-5099

An elegant access to formation and vaporization enthalpies of ionic liquids by indirect DSC experiment and “in silico” calculations Sergey P. Verevkin, Dzmitry H. Zaitsau, Vladimir N. Emel’yanenko, Christoph Schick, Saivenkataraman Jayaraman and Edward J. Maginn, Chem. Commun., 2012, 48, 6915-6917

PCCP journal cover imageIonic liquid-mediated epitaxy of high-quality C60 crystallites in a vacuum Yoko Takeyama, Shingo Maruyama, Hiroki Taniguchi, Mitsuru Itoh, Keiji Ueno and Yuji Matsumoto, CrystEngComm, 2012, 14, 4939-4945

Proton transfer and polarity changes in ionic liquid–water mixtures: a perspective on hydrogen bonds from ab initio molecular dynamics at the example of 1-ethyl-3-methylimidazolium acetate–water mixtures—Part 1 Martin Brehm, Henry Weber, Alfonso S. Pensado, Annegret Stark and Barbara Kirchner, Phys. Chem. Chem. Phys., 2012, 14, 5030-5044

Direct visualization of solution morphology of cellulose in ionic liquids by conventional TEM at room temperature Nan Luo, Yuxia Lv, Dexiu Wang, Jinming Zhang, Jin Wu, Jiasong He and Jun Zhang, Chem. Commun., 2012, 48, 6283-6285

If you’re interested in ionic liquids, why not take a look at the recent cross-journal promotion Incredible ionic liquids: an article collection.

You can keep up to date with all the latest developments across the chemical sciences by signing up to your favourite journal e-alerts or following them on twitter!

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Luminogenic materials have a bright future

Luminogenic materials are a hot topic of research due to their potential applications in biotechnology and memory systems. But most luminogenic materials undergo aggregation-caused quenching (ACQ) in the solid state. This is when the dye molecules near each other aggregate and form species that weaken the material’s emission.

Ben Zhong Tang and his team have been researching materials that instead exhibit aggregation-induced emission (AIE). This makes the preparation of solid state luminogens much simpler as aggregation increases the activity. Unfortunately, there are few AIE-active emitters in the longer wavelength region, which is of interest for biotechnology applications.

Tang’s team have addressed this oversight by developing a novel luminogen which couples the AIE property of tetraphenylethene and the longer wavelength activity of a hemicyanine dye. The emission properties of the resultant crystals can be readily tuned by the solvent molecules in the solution they are grown from.

Crystochromism of the novel luminogen

Most interestingly, the prepared luminogen shows crystochromism: a strong yellow emission in its thermodynamically stable crystalline form and a red colour in its metastable amorphous form. These changes are fully reversible, with grinding, heating or fuming causing the change in the luminogen’s crystallinity.

To find out more, download the ChemComm article today.

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Magneto-chiral dichroism observed in light-harvesting antenna

Artificial light-harvesting antennas absorb light travelling parallel to a magnetic field differently from light travelling anti-parallel to the field, according to Japanese researchers. 

Magneto-chiral dichroism in artificial light-harvesting antenna

This effect – known as magneto-chiral dichroism (MChD) – is proposed to have played a role in the origin of homochirality in life and is important for the development of new magneto-optical devices.

This is only the second example of MChD reported in organic compounds. It indicates that MChD may occur during the light-harvesting process, says the team, which is important not only for learning more about photosynthesis but also for clarifying the origin of asymmetry in biological systems.

Read the communication:
Magneto-chiral dichroism of artificial light-harvesting antenna
Yuichi Kitagawa, Tomohiro Miyatake and Kazuyuki Ishii
Chem. Commun., 2012, DOI: 10.1039/C2CC30996C

Also of interest:
Nanoscale spectroscopy with optical antennas
Palash Bharadwaj, Ryan Beams and Lukas Novotny, Chem. Sci., 2011, 2, 136-140

Artificial Photosynthesis – a ChemComm web theme

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Micro power for micro devices

An easy way to make high-performance micro-supercapacitors based on nanocrystal building blocks has been developed by scientists in the US and China. Micro-power sources have become a key component for micro-electronics but they are expensive and difficult to make. To demonstrate their concept, the team made nanoporous thin-film pseudocapacitor electrodes that showed ultrafast lithium storage kinetics, high capacitance and excellent cycling stability, giving them great promise for high energy and high power micro-device applications.

c2cc30406f

Link to journal article
Ready Fabrication of Thin-Film Electrodes from Building Nanocrystals for Micro-Supercapacitors
Z Chen et al
Chem. Commun., 2012, DOI: 10.1039/c2cc30406f

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One nanoparticle, two nanoparticles, three nanoparticles, four!

Nanoparticles might be small but they frequent the pages of many a journal due to the ongoing boom in nanotechnology research. Whilst they are useful in a myriad of fields, it is still difficult to directly characterise these extraordinarily small entities. King among the visualisation techniques is electron microscopy but this often requires the isolation of the sample on a support – hardly sufficient for analysing a dynamic sample in solution! Dynamic light scattering is another potential technique but finds limitations when it comes to much smaller nanoparticle sizes.

Ideally, you want to be able to count and size individual nanoparticles at a rate which produces reliable statistics. To address this challenge, Richard Compton and his team, including Neil Rees and Yi-ge Zhou who conducted the experiments alongside Jeseelan Pillay, Robert Tshikhudo and Sibulelo Vilakazi from Mintek, Randburg, have used anodic particle coulometry (APC) to measure gold nanoparticle collisions with a glassy carbon microelectrode and thus count and size individual nanoparticles.

With the electrode potential set above +1.0 V, they were able to record oxidative Faradaic transients from nanoparticle collisions and calculate an average nanoparticle radius which compared extremely well to the radius obtained from scanning electron microscopy measurements. They were also able to observe nanoparticle aggregation, which holds great promise for monitoring dynamic aggregation reactions.

It shouldn’t be long before this technique is routinely used to gain more information on all sizes of metallic nanoparticles which are currently being used in a variety of applications.

Read the ChemComm article by Compton and team for more.

Posted on behalf of Iain Larmour, web science writer for ChemComm.

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Super-fast crystals

Identification of all solid forms of a pharmaceutical is important for drug delivery, due to the potential variability in the physical and chemical properties between amorphous and crystalline forms. The amorphous form of a compound is typically more soluble, but less stable than its crystalline counterpart. Not only that but different polymorphs of the crystalline compound can also have significantly different properties.  To accurately characterise drug action, these polymorphs need to be identified.

Using small-scale crystallisation and in-situ Raman spectroscopic analysis of the antihypertensive drug, nifedipine, Franziska Emmerling and colleagues discovered an extraordinarily fast transition from the glassy amorphous state to the metastable β polymorph in less than a minute. The β polymorph is stable for less than ten minutes before transforming again, to the thermodynamically stable α polymorph.

The speed at which the transformations take place implies that classical diffusion is not responsible for the different polymorphs but could instead be the result of small intramolecular changes arising from a pre-ordered physical arrangement of the molecules.

In an industrial world where screening for solid drug forms is always leaning towards scale-reduction and time-reduction, three physical forms on a glass slide in less than twenty minutes is pretty impressive!

To find out more, download the ChemComm article.

Also of interest…  Read Andrew Bond, U. Ramamurty, and Gautam Desiraju’s Chemical Science article on “Interaction anisotropy and shear instability of aspirin polymorphs established by  nanoidentation“.

Posted on behalf of Scott McKellar, web science writer for ChemComm.

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Aromaticity web theme issue – welcoming submissions

We are delighted to announce a high-profile web themed issue on Aromaticity.

Guest editors: Nazario Martín (University Complutense of Madrid), Michael Hayley (University of Oregon) and Rik Tykwinski (University of Erlangen-Nuremberg)

This themed issue will consist of a series of invited Communications and Feature Articles covering work on all aspects of chemistry related with aromaticity – from new fundamental knowledge about aromaticity and theoretically interesting new arene structures to novel applications of aromatics and heteroaromatics which take advantage of their unique optical and electronic attributes.

The level of quality of this issue will be extremely high, and all manuscripts will undergo strict peer review. You are therefore encouraged to report work that you consider to be very important and conceptually significant. Please note that inclusion in the issue is subject to the discretion of the guest editors.

Publication of the peer-reviewed articles will occur without delay to ensure the timely dissemination of the work. The articles will then be assembled on the ChemComm website as a web-based thematic issue.

Submit your work before 31st May 2012. Please add “aromaticity” in the comments to the editor section.

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Ionic Liquids web theme issue – welcoming submissions

ChemComm is delighted to announce a high-profile web themed issue on Ionic Liquids.

Guest editors: Robin D. Rogers (University of Alabama), Doug MacFarlane (Monash University) and Suojiang Zhang (Institute of Process Engineering)

Picture courtesy of Photodisc

This issue will consist of a series of Communications and Feature Articles from prominent scientists working on all aspects of ionic liquid chemistry. The scope will range from new fundamental knowledge about ionic liquids to novel applications of ionic liquids which take advantage of their unique attributes.  Follow on studies or those of routine interest will not be considered. 

The level of quality of this issue will be extremely high, and all manuscripts will undergo strict peer review. You are therefore encouraged to report work that you consider to be very important and conceptually significant in accord with the ChemComm mandate. Please note that inclusion in the issue is subject to the discretion of the guest editors.

Publication of the peer-reviewed articles will occur without delay to ensure the timely dissemination of the work. The articles will then be assembled on the ChemComm website as a web-based thematic issue.

Submit your work before 29th February 2012. Please add “ionic liquids” in the comments to the editor section.

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Modelling reveals interconnect between SERS enhancement mechanisms

Surface enhanced Raman scattering (SERS) uses noble metal substrates to enhance the inherently weak Raman signal from analytes. In some cases, the enhancement stems from two different mechanisms: a physical enhancement that comes from excitation of the metal surface plasmons and a chemical enhancement arising from charge transfer between the metal surface and an adsorbed molecule.

Up until now, theoretical SERS models have tended to treat these mechanisms separately. However, Duan and colleagues point out that this simplification is not always valid since plasmonic properties can be significantly affected by adsorbed molecules. Using state-of-the-art density functional models, they have revealed the connection between the two mechanisms, allowing more accurate modelling of SERS spectra.

To learn more about how Duan’s team have implemented this model, download the ChemComm article.

Also of interest:

Visit the ChemComm Surface Enhanced Raman Spectroscopy web theme issue for more articles.

Posted on behalf of Iain A. Larmour, ChemComm web writer.

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Extension of Hirsch’s rule opens the door on spherical aromaticity

Miquel Solà and Jordi Poater working University of Girona in Spain have put forward an extension of Hirsch’s rule to open-shell spherical species. 

The famous Hückel rule allows one to estimate whether or not a planar ring molecule would have aromatic properties. When the molecule has 4N + 2 π-electrons then it follows Hückel’s rule. In 2000 Andreas Hirsch found a rule to predict the aromaticity of fullerenes, known as the 2(N +1)2 rule and now Solà has extended this rule to spherical systems with an open-shell.

They found that spherical compounds with a half filled last energy level, e.g. those with 2N2 + 2N + 1 electrons, are aromatic. This was backed up with computational evidence and showed that for example C6019+ and C601- both have strong aromatic character.

Solà speculates that this finding could be an important tool for those working in the in stable high spin molecules such as molecular magnets. 

Interested in finding out more? Then download the full ChemComm article for free today.

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