Archive for the ‘Physical’ Category

Mechanochemistry: ChemComm web theme and Faraday Discussion 170 abstracts deadline 12 August

ChemComm Mechanochemistry web collection

We are delighted to present our ChemComm web themed issue on Mechanochemistry: fundamentals and applications in synthesis, guest edited by Stuart James (Queen’s University Belfast, UK) and Tomislav Friščić (McGill University, Canada).  Check out this special online collection now!

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Faraday Discussion 170 on Mechanochemistry– deadline for oral abstracts 12 August 2013

We also invite you to submit your oral abstract for Faraday Discussion 170– Mechanochemistry: From Functional Solids to Single Molecules by Monday, 12 August 2013.  Stuart and Tomislav co-chair the FD170 Scientific Committee; they are joined by Jon Steed, James Mack, Elena Boldyreva and Carsten Bolm.

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Submit your abstract now and register to secure your place at this exciting event!

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A cloak of many carbons

Catalysts can be exceedingly useful in the real world, from treating our car’s exhaust fumes to creating fertilisers.  There are many ways to make catalysts and even multiple ways to make the same catalyst.  The path that you choose to a catalyst can have a significant impact on the quality of the end product.

Eloy del Rio and team from the Structure and Chemistry of Nanomaterials group at the University of Cadiz in Spain have investigated ceria-based oxide-supported gold catalysts for carbon monoxide oxidation.  The routine for depositing the metal phase onto the oxide support and the subsequent catalyst activation step can ultimately affect the activity of the catalyst.  Catalysts prepared by deposition-precipitation with urea followed by activation under oxidising conditions result in significantly more activity than those prepared under reducing conditions.

Variation in catalyst activity under oxidising and reducing activation protocols.

This had previously been observed by others, but the reason for the difference was never discussed.  The authors set out to find out why the activity differed.  They used a suite of nano-analytical and nano-structural techniques to probe the catalysts, finding that the catalyst prepared under reducing conditions had a coat of amorphous carbon which severely hampered the catalyst activity.  This could be removed by a re-oxidation treatment that burnt away the carbon layer and produced an active catalyst similar to the one produced under oxidising conditions.

The precipitating agent used in the synthesis can also influence the resulting activities of catalysts prepared via the deposition-precipitation method.  No difference between oxidising and reducing activations is observed when sodium carbonate is used in place of urea.

To read the details, check out the ChemComm article in full:

Dramatic effect of redox pre-treatments on the CO oxidation activity of Au/Ce0.50Tb0.12Zr0.38O2-x catalysts prepared by deposition-precipitation with urea: a nano-analytical and nano-structural study
E. del Rio, M. López-Haro, J.M. Cies, J.J. Delgado, J.J. Calvino, S. Trasobares, G. Blanco, M.A. Cauqui and S. Bernal
Chem. Commun., 2013, 49, Accepted Manuscript
DOI: 10.1039/C3CC42051e

Iain Larmour is a guest web writer for ChemComm.  He has researched a wide variety of topics during his years in the lab including nanostructured surfaces for water repellency and developing nanoparticle systems for bioanalysis by surface enhanced optical spectroscopies.  He currently works in science management with a focus on responses to climate change.  In his spare time he enjoys reading, photography and art.

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ChemComm Emerging Investigator Lectureship 2013: Winners Announced

louise

Louise Berben

On behalf of the ChemComm Editorial Board we are delighted to announce the winners of the ChemComm Emerging Investigator Lectureship 2013.

Marina Kuimova

Marina Kuimova

This year we received a high number of excellent nominations and therefore the Editorial Board have decided to award two Emerging Investigator Lectureships in 2013. The winners are Professor Louise A. Berben (University of California Davis, USA) and Dr Marina Kuimova (Imperial College London).

This annual lectureship recognises an emerging scientist in the early stages of their independent academic career.

The Editorial Board commended Louise’s contributions to the field of synthetic and physical inorganic chemistry, and Marina was awarded the lectureship for her excellent work within biophysical chemistry. Further details of the two Lectureships, including lecture locations, will be announced soon.

To find out more about the winners’ research, read some of their latest articles in ChemComm:

Redox active aluminium(III) complexes convert CO2 into MgCO3 or CaCO3 in a synthetic cycle using Mg or Ca metal
Thomas W. Myers and Louise A. Berben
Chem. Commun., 2013, DOI: 10.1039/C2CC37208H

Simple routes to bulky silyl-substituted acetylide ligands and examples of V(III), Fe(II), and Mn(II) complexes
Gereon M. Yee, Kristin Kowolik, Shuhei Manabe, James C. Fettinger and Louise A. Berben
Chem. Commun., 2011,47, 11680-11682, DOI: 10.1039/C1CC14758G

Reactive oxygen species in photochemistry of the red fluorescent protein “Killer Red”
Russell B. Vegh, Kyril M. Solntsev, Marina K. Kuimova, Soohee Cho, Yue Liang, Bernard L. W. Loo, Laren M. Tolbert and Andreas S. Bommarius
Chem. Commun., 2011,47, 4887-4889, DOI: 10.1039/C0CC05713D

Also of interest: You can now browse the 2013 Emerging Investigators Issue – which features research from outstanding up-and-coming scientists

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Nitrogen-containing graphene-like structures: Theory and experiment combine to reveal active sites

There is significant interest in nitrogen-containing electrocatalysts, driven by the need to find cost-effective and efficient material solutions for replacing platinum in polymer electrolyte membrane fuel cells.  However, the active sites of non-platinum group metal, oxygen reduction reaction electrocatalysts have been contentious for over 50 years.

Fortunately researchers are agreed that Metal(Me)-Nx centres may serve as possible active sites but whether it is Me-N2 or Me-N4 remains unresolved.  X-ray Photoelectron Spectroscopy (XPS) would be the ideal technique to answer this question if it didn’t rely on the use of reference spectra; none exist for the Me-N2 species which makes it less than ideal.

Fitting of DFT calculated curves to experimental results.

Kateryna Artyushkova, Plamen Atanassov and their team have overcome this problem by using density functional theory (DFT) to calculate the binding energy shifts of the species.  Calculating the binding energy shifts, rather than just the binding energies, allows the team to overcome the challenges associated with DFT calculations including; treatment of the core electrons and the poorly screened Coulomb potential near the nucleus.

Once validated, the DFT output can be used as input for XPS curve fitting.  This has revealed rearrangement around Cobalt-Nx centres in an oxidizing atmosphere and supports the understanding of these catalysts as vacancy-and-substitution defects in a graphene-like matrix.

This work demonstrates the synergy between experiment and theory which allows critical information to be extracted that might otherwise remain hidden.

For more, read this ChemComm article in full:

Density functional theory calculations of XPS binding energy shift for nitrogen-containing graphene-like structures
K. Artyushkova, B. Kiefer, B. Halevi, A. Knop-Gericke, R. Schlogl and P. Atanassov
Chem. Commun., 2013, 49, 2539-2541
DOI: 10.1039/C3CC40324F

Iain Larmour is a guest web-writer for ChemComm.  He has researched a wide variety of topics during his years in the lab including nanostructured surfaces for water repellency and developing nanoparticle systems for bioanalysis by surface enhanced optical spectroscopies.  He currently works in science management with a focus on responses to climate change.  In his spare time he enjoys reading and photography.

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Lewis acidity of metal ions investigated in the gas phase

In aqueous solutions metal ions can promote acidity via the hydrolysis reaction. This is measured by a hydrolysis constant, which has previously been correlated to the ratio of the ion’s charge to size. Unfortunately lead and tin stubbornly refuse to fit this correlation; additional factors must be at work.

Anthony Stace and team investigated further by studying the minimum number of water molecules needed to stabilise a dication complex in the gas phase against spontaneous hydrolysis (called Coulomb fission in the gas phase). They found an extraordinarily good correlation between the number of water molecules required and the metal ion’s hydrolysis constant in aqueous solution.

What about those stubborn dications, lead and tin? They fit within the trend, requiring a surprising 11 and 26 water molecules to stabilise them respectively. This work suggests that Lewis acidity of metal ions is determined, in part, by the requirement that the ions remain fully solvated.

Plot of acidity constant against minimum number of water molecules required to stabilise the complex against Coulomb fission.

To find out more, download the ChemComm article today.

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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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