The mysterious f-block

Thomas Just Sørensen is a guest web-writer for PCCP. He is currently a post-doctoral researcher at the University of Copenhagen, Denmark.

Table of contents imageThe complex electronic structure of the lanthanides and actinides is largely a mystery. The f-shell is not readily explained in our theoretical treatment of atoms and molecules, and coupled with the difficulty of obtaining readily interpreted experimental data. The result is that we are still struggling to understand the elements at the bottom of the periodic table. Xu and co-workers conduct a good and meticulous computational study of lanthanide trifluorides, and do significantly increase our understanding of the rare earth elements, albeit in simple molecules in the gas phase. My problem is that I work in aqueous solution, where lanthanide ions have not just three ligands—as the molecules investigated in this paper have—they have eight, nine or ten.

The bonding orbitals in the lanthanide series can, in theory, be 4f, 5d, and 6s orbitals. Traditionally, the contracted f-shell orbitals have been viewed as shielded, and the interaction between lanthanide ions and ions of the opposite charge has to be regarded as purely ionic in nature. This work shows that our current computational models include a significant covalent contribution in the bonding of fluoride to trivalent lanthanide ions.

I look forward to the paper where lanthanide ions with a full coordination sphere are treated, although I fear it will be a long wait. Luckily, the papers reporting the progress towards a full computational treatment of lanthanide in solution are also worth reading, even for experimentalists like me.

On structure and bonding of lanthanoid trifluorides LnF3 (Ln = La to Lu)
Wei Xu, Wen-Xin Ji, Yi-Xiang Qiu, W. H. Eugen Schwarz and Shu-Guang Wang
Phys. Chem. Chem. Phys., 2013, 15, 7839-7847
DOI: 10.1039/C3CP50717C

by Dr Thomas Just Sørensen

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Integrated microfluidic test-bed for energy conversion devices

Integrated microfluidic test-bed for energy conversion devicesSegalman, Ager and co-authors present a versatile microfluidic test-bed for testing of integrated catalysis and mass transport components for energy conversion via water electrolysis in their recent PCCP Communication.

Their microfluidic electrolyzer for water splitting can be integrated with different anode and cathode materials, which can be easily exchanged and tailored at scales amenable to research activities, therefore allowing the performance of integrated devices to be readily assessed. In addition, their novel design can be easily adapted to allow direct solar irradiation and, consequently, artificial photosynthesis.

Read the Communication today:

Integrated microfluidic test-bed for energy conversion devices
Miguel A. Modestino, Camilo A. Diaz-Botia, Sophia Haussener, Rafael Gomez-Sjoberg, Joel W. Ager and Rachel A. Segalman
DOI: 10.1039/C3CP51302E

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Understanding defects in graphene: PCCP article in Chemistry World

The products of thermally exfoliating graphite oxide to make graphene are much more complex than previously thought, new research shows. The volatile compounds formed vary with reaction conditions, and may influence the graphene’s structure.

The most common way to prepare graphene is by thermally reducing – or ‘exfoliating’ – graphite oxide. But the graphene produced often contains defects and lacks the perfect honeycomb structure. One explanation is that these defects may be the result of organic by-products forming and escaping as gases during the reaction.

Interested to know more? Read the full article by Emma Stoye in Chemistry World here…

Complex organic molecules are released during thermal reduction of graphite oxides
Zdeněk Sofer, Petr Šimek and Martin Pumera
Phys. Chem. Chem. Phys., 2013, Advance Article
DOI: 10.1039/C3CP51189H

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Understanding defects in graphene

The products of making graphene by thermally exfoliating graphite oxide are much more complex than previously thought, new research shows.

The most common way to prepare graphene is by thermally reducing – or ‘exfoliating’ – graphite oxide. But the graphene produced in the process often contains defects and lacks the perfect ‘honeycomb’ structure. One explanation is that these defects may be the result of organic by-products forming and escaping as gases during the reaction.

Scientists from Singapore and the Czech Republic allowed exfoliation to take place in an autoclave at 500 degrees for two hours then analysed the gases produced using gas chromatography–mass spectrometry (GC-MS). They detected many other volatiles in addition to H2O, CO and CO2, including polycyclic aromatic molecules, and those containing sulphur and nitrogen heteroatoms that are present as contaminants in the graphite oxide.

Moreover, the nature of the volatiles released varies hugely depending on pressure (2 bar versus 100 bar) and the gaseous atmosphere in which the exfoliation was carried out (hydrogen versus inert argon). The method by which the graphite oxide itself was prepared also had an effect – the Hummers method yielded the highest number of volatiles.

Understanding these by-products is crucial as they can affect the structure of the resultant graphene which influences its future use. The team suggest that measuring the volatiles produced during exfoliation could help determine the nature of defects.

Read this HOT PCCP article in full today:

Complex organic molecules are released during thermal reduction of graphite oxides
Z Sofer, P Šimek and M Pumera
DOI: 10.1039/C3CP51189H

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The Gordon F. Kirkbright Bursary Award 2014

The Gordon F. Kirkbright bursary award is a prestigious annual award that enables a promising student/non-tenured young scientist of any nation to attend a recognised scientific meeting or visit a place of learning.

Applications are invited for the 2014 Gordon Kirkbright Bursary.

For further information contact John Chalmers at, email: vibspecconsult@aol.com

The closing date for entries is 31 December 2013.

The fund for this bursary was established in 1985 as a memorial to Professor Gordon Kirkbright in recognition of his contributions to analytical spectroscopy and to science in general. Although the fund is administered by the Association of British Spectroscopists (ABS) Trust, the award is not restricted to spectroscopists.

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DNP SENS – a fast method to probe surface functionality

We are delighted to welcome Alexander Forse as a new guest web-writer for PCCP, Nanoscale, and Energy and Environmental Science. Alexander is a PhD student in Professor Clare Grey’s group at the University of Cambridge. When not in the lab, he enjoys playing football, skateboarding and producing electronic music.

Table of contents imageThe development of new experimental methods to probe surface functionality is crucial to the understanding of functional materials. For the typically low concentrations of surface functional groups, traditional nuclear magnetic resonance (NMR) spectroscopy lacks the sensitivity to provide chemical information quickly.

In dynamic nuclear polarisation surface enhanced NMR spectroscopy (DNP SENS), a porous or particulate sample is wetted with a radical solution. The large polarisation of the radicals’ unpaired electrons is then transferred to surrounding nuclear spins, with a typical signal enhancement of between 10 and 100. This can decrease experimental time dramatically, whilst probing specifically the surface functionality.

In their recent communication in PCCP, the research groups of Professor Lyndon Emsley and Professor Christophe Copéret collaborated to characterise the organic part of a periodic mesoporous organosilicate (PMO). Structural changes following functionalisation with an organoiridium compound were studied using DNP SENS. Remarkably, 15N (0.37% natural abundance) DNP SENS spectra revealed the appearance of a new chemical environment following functionalisation, corresponding to nitrogen atoms (in the PMO) bonded to Iridium (III). This key piece of evidence allowed the authors to elucidate a layered structure in which only the surface layers were available for functionalisation.

Whilst the 15N spectra would have taken weeks to acquire using conventional NMR methods, DNP SENS experiments took only a matter of hours, highlighting the power of this fascinating method.

Full details can be found in the PCCP communication:

Molecular-level characterization of the structure and the surface chemistry of periodic mesoporous organosilicates using DNP-surface enhanced NMR spectroscopy
Wolfram R. Grüning, Aaron J. Rossini, Alexandre Zagdoun, David Gajan, Anne Lesage, Lyndon Emsley and Christophe Copéret
DOI: 10.1039/C3CP00026E

By Alexander Forse

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Top 10 most accessed PCCP articles in March

The following articles in PCCP were the top ten most accessed in March:

Structural evolution and the capacity fade mechanism upon long-term cycling in Li-rich cathode material 
Bohang Song,  Zongwen Liu,  Man On Laia and   Li Lu 
Phys. Chem. Chem. Phys., 2012,14, 12875-12883 
DOI: 10.1039/C2CP42068F 

A europium complex with enhanced long-wavelength sensitized luminescent properties 
Fumin Xue, Yan Ma,  Limin Fu,  Rui Hao,  Guangsheng Shao,  Minxian Tang,  Jianping Zhang and  Yuan Wang   
Phys. Chem. Chem. Phys., 2010,12, 3195-3202 
DOI: 10.1039/B920448B 

CO adsorption on Cu–Pd alloy surfaces: ligand versus ensemble effects 
Sung Sakong, Christian Mosch and Axel Groß 
Phys. Chem. Chem. Phys., 2007,9, 2216-2225 
DOI: 10.1039/B615547B 

Single nanoparticle plasmonics 
Emilie Ringe, Bhavya Sharma,  Anne-Isabelle Henry,  Laurence D. Marks and   Richard P. Van Duyne 
Phys. Chem. Chem. Phys., 2013,15, 4110-4129 
DOI: 10.1039/C3CP44574G 

Nutrient removal and energy production in a urine treatment process using magnesium ammonium phosphate precipitation and a microbial fuel cell technique 
Guo-Long Zang,  Guo-Ping Sheng,   Wen-Wei Li,  Zhong-Hua Tong,  Raymond J. Zeng,  Chen Shi and   Han-Qing Yu 
Phys. Chem. Chem. Phys., 2012,14, 1978-1984 
DOI: 10.1039/C2CP23402E 

Semiconductor-based nanocomposites for photocatalytic H2 production and CO2 conversion 
Wenqing Fan,   Qinghong Zhang and   Ye Wang 
Phys. Chem. Chem. Phys., 2013,15, 2632-2649 
DOI: 10.1039/C2CP43524A 

Density functional theory for transition metals and transition metal chemistry 
Christopher J. Cramer and   Donald G. Truhlar 
Phys. Chem. Chem. Phys., 2009,11, 10757-1081
DOI: 10.1039/B907148B 

Visible light driven overall water splitting using cocatalyst/BiVO4 photoanode with minimized bias
Chunmei Ding,  Jingying Shi, Donge Wang, Zhijun Wang,  Nan Wang,   Guiji Liu,  Fengqiang Xiong and   Can Li 
Phys. Chem. Chem. Phys., 2013,15, 4589-4595 
DOI: 10.1039/C3CP50295C 

Characterization of nanostructured hybrid and organic solar cells by impedance spectroscopy 
Francisco Fabregat-Santiago, Germà Garcia-Belmonte,  
Iván Mora-Seró and  Juan Bisquert 
Phys. Chem. Chem. Phys., 2011,13, 9083-9118 
DOI: 10.1039/C0CP02249G 

Charge transport improvement employing TiO2 nanotube arrays as front-side illuminated dye-sensitized solar cell photoanodes
Andrea Lamberti, Adriano Sacco, Stefano Bianco, Diego Manfredi, Federica Cappelluti, Simelys Hernandez, Marzia Quaglio and Candido Fabrizio Pirri  
Phys. Chem. Chem. Phys., 2013,15, 2596-2602 
DOI: 10.1039/C2CP41788J 

We hope you enjoyed reading the articles – please sign up for the free PCCP table of contents e-alerts to make sure you keep up to date with the latest research being published in the journal

On behalf of the Editorial Board of  PCCP, we invite you to submit your best research to us today!

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Water of life

Thomas Just Sørensen is a guest web-writer for PCCP. He is currently a post-doctoral researcher at the University of Copenhagen, Denmark.

molecular image plus 4 graphsMore than 50 % of our bodies are water. Plain and simple, we are more water than anything else. Following that statement it must be said that none of the water in our body is simply water. Excluding the content of your bladder, none of the water in your body is water as you have come to know it from your glass, rain, your local river and the oceans. Your body water surrounds cell membranes, microtubule, proteins, sugars, bones; all the smaller and larger biomolecules that make up our bodies. Not to mention the specific concentrations of salts and inorganic molecules that are required to run our bodies. We are beginning to understand the structure of water itself, and when water solvates simple ions. The work of Takis and co-workers increases the stakes and opens our mind to the specific solvations of small protein fragments.

The research from the groups of Troganis and Melissas at the University of Ioannina is focused on simple dipeptides, and exploits molecular dynamic simulations, density functional theory based calculations and advanced nuclear magnetic resonance spectroscopy. This combination allows them to probe the solvation of the small peptide experimentally, and rationalize the findings by the theoretical approach. Specifically the distances between selected carbon atoms in the peptide structure and water molecules can be measured. The challenge in this approach is the continuous and rapid exchange of the water molecules.

To me, the most readily accessible data is the plots showing the probability of finding water oxygen and hydrogen atoms at a specific distance to selected groups in the peptide structure. Here, extracted from MD simulations. When experimental data can yield similar results, we will be able to start directly investigating how more than half of our bodies are made up.

The excellent work on the solvation of dipeptides is published in the PCCP paper titled:

Probing micro-solvation in “numbers”: the case of neutral dipeptides in water
Panteleimon G. Takis, Konstantinos D. Papavasileiou, Loukas D. Peristeras, Vasilios S. Melissas and Anastassios N. Troganis
Phys. Chem. Chem. Phys., 2013, 15, 7354-7362
DOI: 10.1039/C3CP44606A

by Thomas Just Sørensen

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Playing with liquid crystalline water balloons

Thomas Just Sørensen is a guest web-writer for PCCP. He is currently a post-doctoral researcher at the University of Copenhagen, Denmark.

Table of contents imageSometimes you just have to sit back, read, and enjoy the ride. This is exactly the case with the work of Kirsten Harth and Ralf Stannarius from the Institute of Experimental Physics at the Otto von Guericke University Magdeburg. The have investigated the interface tension between soapy water and a smectic liquid crystal.

Apparently, thin films of smectic—and only smectic—liquid crystals readily form in water, where they can form bubbles. In an ingenious experimental set-up Harth and Stannarius can measure the surface tension by letting a single air bubble put the smectic film bubble under tension. Amazing as it sounds, it is a viable procedure and the interface tension can be accurately determined.

The generic appeal of this study makes it one of the more enjoyable reads I have had in a while. The images were just so interesting that my curiosity forced me to download and read the paper.

If you are equally enticed, the paper is published in PCCP:

Measurement of the interface tension of smectic membranes in water
Kirsten Harth and Ralf Stannarius
Phys. Chem. Chem. Phys., 2013, 15, 7204-7209
DOI: 10.1039/C3CP44055A

by Thomas Just Sørensen

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Using NMR to study ion adsorption in porous carbide-derived carbons

Nuclear magnetic resonance study of ion adsorption on microporous carbide-derived carbonDeveloping alternative energy storage devices, such as supercapacitors, is of rising importance when facing today’s challenges of climate change and fossil fuel depletion. Supercapacitors typically employ porous carbon electrodes as they have large surface areas for ion electrosorption, good electronic conductivities and relatively low production cost. The design and improvement of supercapacitors is only possible with a detailed understanding of ion adsorption within porous carbon.

A group of Scientists from the UK, Germany, the USA and France have used NMR spectroscopy to systematically study ion adsorption in porous carbide-derived carbons. Their results provide insight into the different electrolyte environments present in the carbon, and how they are affected by pore size. The group, led by Prof. Clare Grey, also explored the effects of sample orientation, and developed 13C-1H CP NMR experiments to select the ions adsorbed in the pores.

These techniques presented in their recent PCCP paper will be useful for future investigations into adsorption on porous carbons.

Read this HOT article today:

Nuclear magnetic resonance study of ion adsorption on microporous carbide-derived carbon
Alexander C. Forse, John M. Griffin, Hao Wang, Nicole M. Trease, Volker Presser, Yury Gogotsi, Patrice Simon and Clare P. Grey
DOI: 10.1039/C3CP51210J

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