Author Archive

Mutating DNA with electric fields

electric-field induced mutation of DNAIt may be possible to selectively mutate DNA using electric fields, opening the door for exciting new strategies to tune DNA’s structures.

José Cerón-Carrasco and Denis Jacquemin used density functional theory and second-order Møller–Plesset approaches to investigate the effects of electric fields on the tautomeric equilibria of the guanine–cytosine (GC) base pair. They found that electric fields not only drastically alter the kinetics of these equilibria, but also tune the very mechanism of the proton transfer reactions.

A proton transfer between two bases in DNA causes a modification of the interbase hydrogen-bonding pattern, and may consequently lead to a mutation. It is known that external environmental agents, such as free radicals and ionizing radiation, can alter the natural tautomeric equilibria of bases, but little research has been conducted so far about the effects of an external electric field.

Read more in this HOT PCCP article:

Electric-field induced mutation of DNA: a theoretical investigation of the GC base pair
José P. Cerón-Carrasco and Denis Jacquemin
DOI: 10.1039/C2CP44066K

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Professor Mike Ashfold picks out his Editor’s Choice on photochemistry and spectroscopy

Mike AshfoldPCCP Advisory Board members are occasionally invited to select a few personal ‘highlights’ from recent issues of the journal. I received such a call in autumn 2012, and readily agreed to try and pick out ten particularly noteworthy papers in the general areas of photochemistry and spectroscopy.hydrogen bonding in electronically excited states

I had long penciled in the Christmas break as the first realistic opportunity for this task. I have been involved with PCCP in one way or another since its launch in 1999, so I should know better than most just how successful a journal it has now become. But it very soon became apparent that I would need to constrain my selection more tightly than I had originally imagined. PCCP publishes a lot of papers (1843 in 2012, many of which impinge on areas of photochemistry and spectroscopy, and many of which certainly merit very careful study. So, my first self-imposed (and completely arbitrary) constraint was that only papers carrying a (print) publication date of 2012 would be eligible for inclusion in my ‘Editor’s Choice’ list. This still left the challenge of somehow picking out less than one in every hundred papers!

The next obvious challenge was that Vol. 14 contains several themed issues, two of which – on Ultrafast chemical dynamics and on Hydrogen bonding in electronically excited states – could easily provide more than ten personal highlights.  In both cases, the guest editors did an exemplary job securing many new, high quality articles. I thoroughly recommend both of these themed issues to all who share my scientific interests, and claim writer’s prerogative by counting each as just one of my ten! I applied one more filter, and excluded from consideration the several excellent papers published in PCCP by Bristol colleagues during 2012.

The 2012 collection includes many notable articles offering new insights into photo-induced processes (e.g. photofragmentations, studies of intramolecular energy flow, photoionization, etc) and into the dynamics of bimolecular encounters – some with unprecedented definition of the initial (reactant) and final (product) quantum states. From the many excellent gas phase studies, I eventually selected:

M.P. Grubb, M.L. Warter and S.W. North, ‘Stereodynamics of multistate roaming’, which reported clear correlations between the velocity vector v and the angular momentum vector j of the NO fragments from NO3 photolysis, implying that the final intra-molecular abstraction in this roaming ‘reaction’ is constrained to occur at planar geometries;

C. Logé and U. Boesl, ‘Laser mass spectrometry with circularly polarized light: two-photon circular dichroism’ demonstrating two-photon circular dichroism of isolated gas phase molecules (cyclopentadienone) by multiphoton ionization measurements;

and the perspective article C.D. Lin and Junliang Xu, ‘Imaging ultrafast dynamics of molecules with laser-induced electron diffraction’, as a new route to imaging the ultrafast dynamics of small molecules with sub-Å spatial and a few-fsec temporal resolution.

My personal interests are now evolving to include photo-induced processes in solution, with particular emphasis on studies that reveal dynamical information about such processes. Obviously, there already exists a very rich and extensive literature pertaining to this field – which I am working hard to absorb – but the 2012 issues of PCCP provide many further articles that I have now come to regard almost as essential reading.  The following five complete my ‘Editor’s Choice’ list:

B. Abel, U. Buck, A. L. Sobolewski and W. Domcke, ‘On the nature and signatures of the solvated electron in water’ – a perspective article that reviews recent measurements of the binding energy of hydrated electrons by liquid-jet photoelectron spectroscopy, and considers their implications for our understanding of electron solvation in aqueous environments;

R.R. Frontiera, C. Fang, J. Dasgupta and R.A. Mathies, ‘Probing structural evolution along multidimensional reaction coordinates with femtosecond stimulated Raman spectroscopy’. Another excellent perspective article, in which the authors demonstrate how the exquisite time and frequency resolution afforded by fsec stimulated Raman spectroscopy has allowed them to follow structural evolutions in an isomerization, and in selected electron and proton transfer reactions;

O. Braem, T.J. Penfold, A. Cannizzo and M. Chergui, ‘A femtosecond fluorescence study of vibrational relaxation and cooling dynamics of UV dyes’– that reports a fsec broad-band fluorescence up-conversion study that explores details of the (contrasting) vibrational relaxation dynamics of two UV chromophores;

K.M. Lange, A. Kothe and E.F. Aziz, ‘Chemistry in solution: recent techniques and applications using soft X-ray spectroscopy’.  Another perspective article, this one highlighting some of the new opportunities for studying the structure and dynamics of chemical and biochemical systems in solution offered by time-resolved soft X-ray absorption and emission spectroscopies;

F. Zamponi, J. Stingl, M. Woerner and T. Elsaesser, ‘Ultrafast soft-mode driven charge relocation in an ionic crystal’  – a short paper that illustrates some of the exciting structural and dynamical insights offered by the latest generation fsec X-ray laser pulses in powder diffraction measurements of an ionic solid (potassium dihydrogen phosphate in this case).

Read Professor Ashfold’s Editor’s choice selection for free for a limited period:

Stereodynamics of multistate roaming
Michael P. Grubb, Michelle L. Warter and Simon W. North
DOI: 10.1039/C2CP40235A

Laser mass spectrometry with circularly polarized light: two-photon circular dichroism
Christoph Logé and Ulrich Boesl
DOI: 10.1039/C2CP41405H

Imaging ultrafast dynamics of molecules with laser-induced electron diffraction
C. D. Lin and Junliang Xu
DOI: 10.1039/C2CP41606A

On the nature and signatures of the solvated electron in water
B. Abel, U. Buck, A. L. Sobolewski and W. Domcke
DOI: 10.1039/C1CP21803D

Probing structural evolution along multidimensional reaction coordinates with femtosecond stimulated Raman spectroscopy
Renee R. Frontiera, Chong Fang, Jyotishman Dasgupta and Richard A. Mathies
DOI: 10.1039/C1CP22767J

Chemistry in solution: recent techniques and applications using soft X-ray spectroscopy
Kathrin M. Lange, Alexander Kothe and Emad F. Aziz
DOI: 10.1039/C2CP24028A

A femtosecond fluorescence study of vibrational relaxation and cooling dynamics of UV dyes
Olivier Braem, Thomas J. Penfold, Andrea Cannizzo and Majed Chergui
DOI: 10.1039/C2CP23167K

Ultrafast soft-mode driven charge relocation in an ionic crystal
F. Zamponi, J. Stingl, M. Woerner and T. Elsaesser
DOI: 10.1039/C2CP24072F

And don’t forget to check out his themed issue highlights:

Ultrafast chemical dynamics 
Guest Editors: Klaas Wynne (University of Glasgow, UK) and Neil T. Hunt (University of Strathclyde, UK).

Hydrogen bonding in electronically excited states 
Guest Editors: Guang-Jiu Zhao and Ke-Li Han (Dalian Institute of Chemical Physics, China)

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Surface-Enhanced Raman Spectroscopy – how much do we understand?

Despite 35 years of research and over 10 000 publications on surface-enhanced Raman spectroscopy (SERS), a universal agreement regarding the physical mechanism responsible for the effect still appears to be elusive. Is SERS in actual fact better understood than the impression given by a number of tenacious misconceptions? Professor Martin Moskovits believes so.

surface enhanced Raman spectroscopyIn his recent PCCP Perspective, Moskovits discusses several important topics in SERS, which are often subject to dispute or contradictions in the current literature, including its physical origin. He explains plasmonic theory, the mechanism that underlies the current understanding, and reasons that alternatively proposed mechanisms, such as chemical enhancement, have not only impeded the establishment of a universally accepted understanding, but have hindered the use of SERS in applications such ultrasensitive chemical and biological sensors.

SERS is a surface-sensitive technique that enhances Raman signals from Raman-active analyte molecules absorbed onto specially prepared metal surfaces.  SERS is sufficiently sensitive to allow the detection of single molecules.

SERS theory, as it is commonly applied, is a classical theory largely based on electrostatics. To obtain a more complete understanding of SERS, a theory based on quantum mechanics, and approached as a dynamical theory, needs developing, Moskovits explains in his review. He suggests that in the meantime, researchers should deal with the surface chemistry that arises in a given experiment on a molecule-by-molecule basis.

Read the details in this HOT PCCP Perspective today:

Persistent misconceptions regarding SERS
Martin Moskovits
DOI: 10.1039/C2CP44030J

If you enjoyed this perspective, you may also be interested in our web collection on SERS.

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Coherent transient spectroscopy with continuous wave quantum cascade lasers

Rapid passage effects have been demonstrated in a Lamb dip experiment for the first time, by researchers from Oxford, UK.

Grant Ritchie’s team conducted Lamb dip spectroscopy on a low pressure sample of NO using a narrow-linewidth, high-power, single-mode quantum cascade laser. They were able to determine the laser linewidth, and that the power was sufficient to induce significant population transfer of up to 35%, from the widths of the Lamb dips. The population transfer efficiencies could be controlled by the laser chirp rate.

The lamb dip signals became increasingly asymmetric as the chirp rate was increased. At sufficiently high chirp rates rapid passage oscillations on the Lamb dips were observed due to the narrow laser linewidth, and were seen to be affected by the hyperfine splitting in the transition.

Furthermore, the team showed that it was possible to separate the asymmetry effect from the rapid passage oscillations by pumping a single velocity group using a second laser at a fixed frequency.

Read this HOT article today:

Coherent transient spectroscopy with continuous wave quantum cascade lasers
James M. R. Kirkbride, Sarah K. Causier, Elin A. McCormack, Damien Weidmann and Grant A. D. Ritchie
DOI: 10.1039/C2CP44116K

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Grabbing attention: Graphene oxide and its ability to remove radioactive waste

In a recent PCCP paper, scientists have shown that graphene oxide has a surprising ability to quickly remove radioactive material from contaminated water.

This exciting article, by James Tour, Stepan Kalmykov and co-workers, has been featured in Futurity, UPI.com and Business Standard.

They found that atom-thick flakes of graphene oxide can bind quickly to natural and human-made radionuclides and condense them into solids for easy removal from contaminated water. The flakes are soluble in liquids and easily produced in bulk. 

Although detection of radionuceotide contamination is relatively simple, their removal from aqueous media is significantly challenging and costly. It is hoped that the findings from this collaborative effort from researchers at Rice University and Lomonosov Moscow State could be put into use in the cleanup of contaminated sites like the Fukushima nuclear plants damaged by the 2011 earthquake and tsunami.

Read this HOT PCCP article today: 

Graphene oxide for effective radionuclide removal
Anna Yu. Romanchuk, Alexander S. Slesarev, Stepan N. Kalmykov, Dmitry V. Kosynkin and James M. Tour
DOI: 10.1039/C2CP44593J

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Predicting properties of ionic liquids

It is now possible to accurately predict the density, refractive index and molar polarisability of any imidazolium-based ionic liquid thanks to the recent work of Schröder et al.

Given the availability of at least one million simple ionic liquids, predicting which ionic liquid is best suited to a given application is a significant task. Molar polarisability is a key factor in describing solvation effects and, in principle, can be determined by various quantum-mechanical methods. However, these methods are Polarisabilities of ionic liquidstime-consuming and can only be applied to a small subset of ionic liquids.

Schroder et al. used a Designed Regression Analysis to deconstruct the molar polarisability and molar volume into atomic contributions in this recent PCCP article. They used their approach to explore how the refractive indices of various imidazolium-based ionic liquids were influenced by the length of the alkyl chains.

Read the full PCCP article today:

Polarisabilities of alkylimidazolium ionic liquids
Christian Schröder, Katharina Bica, Maggel Deetlefs and Kenneth R. Seddon
DOI: 10.1039/C3CP43867H

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New PCCP Associate Editor: Dr Ajayaghosh

New PCCP Associate Editor Dr Ayyappanpillai AjayaghoshWe are extremely pleased to annouce that Dr Ayyappanpillai Ajayaghosh is a new Associate Editor for Physical Chemistry Chemical Physics (PCCP). His research interests include supramolecular chemistry, chemosensors, low band-gap polymers, fluorescent gels, organic nanostructures and photoresponsive systems.

Dr Ajayaghosh is a CSIR Outstanding Scientist at the National Institute for Interdisciplinary Science and Technology (NIIST), India. He completed his PhD at the University of Calicut after graduating from Kerala University with a BSc. He has received numerous awards including  the Infosys Prize (2012) for his outstanding contribution in the field of physical sciences, and in particular for his work that has advanced supramolecular chemistry.

Dr Ajayagosh will begin handling papers soon and so we encourage you to submit to his editorial office.

Read Dr Ajayaghosh’s paper in the PCCP themed issue on materials innovation through interfacial physics and chemistry:

Excitation energy migration in oligo(p-phenylenevinylene) based organogels: structure-property relationship and FRET efficiency
Chakkooth Vijayakumar, Vakayil K. Praveen, Kalathil K. Kartha and Ayyappanpillai Ajayaghosh
DOI: 10.1039/C0CP02110E

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Not-so innocent interactions of oxide-surfaces

In this insightful and well-rounded review, Gianfranco Pacchioni summarises the latest knowledge regarding the metal/oxide interface. Such knowledge has become crucial in the elucidation of reaction mechanisms and catalytic properties of metal-oxide catalysts.

Thanks to increasingly sophisticated techniques, it has become known that the original chemical and structural properties of a metal nanoparticle deposit can be significantly altered upon interaction with an oxide support. Particularly for catalysts containing metal nanoparticles smaller then about 1 nm, the phenomenon is particularly significant and somewhat complex.Electronic interactions and charge transfers of metal atoms and clusters on oxide surfaces

For a long time, it was assumed that the oxide component of heterogeneous catalysts provided an “inert” support. Pacchioni takes us through the experimental and theoretical evidence that has shown that the support is in fact not as “innocent” as first thought, and focuses on the nature of the chemical bonds formed between metal atoms and clusters and oxide surfaces.

Read this PCCP Perspective in full today:

Electronic interactions and charge transfers of metal atoms and clusters on oxide surfaces
Gianfranco Pacchioni
DOI: 10.1039/C2CP43731G

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Understanding nanoparticle surface electromagnetic fields

US Scientists have successfully used second harmonic generation (SHG) measurements to probe the complicated plasmon resonances arising from inter-particle interactions within nanoparticle networks.

Kenneth Knappenberger Jr. and Manabendra Chandra from Florida State University performed systematic polarization-resolved single-particle SHG measurements on solid gold nanosphere dimers.  In addition, continuous polarization variation (CPV) experiments were used to obtain single particle non-linear optical data. They were able to demonstrate the superiority of their technique over measurements that rely exclusively on linearly polarized light to study structure-specific plasmonics.single particle non-linear optical spectroscopy to study nanoparticle surface electromagnetic fields

A large SHG depolarization ratio was measured when the two nanoparticles forming a dimer were in close vicinity of each other. CPV spectra of single dimers revealed large inter-dimer variations, which can only be described by including magnetic-dipolar interactions.

Their work represents an important step towards a predictive understanding of the optical properties of nanostructured materials.

Read this HOT PCCP article today:

Nanoparticle surface electromagnetic fields studied by single-particle nonlinear optical spectroscopy
Manabendra Chandra and Kenneth L. Knappenberger
DOI: 10.1039/C2CP43271D, Paper

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New PCCP Associate Editor Prof. Gaoquan Shi

Photograph of Gaoquan ShiWe are delighted to welcome Professor Gaoquan Shi as a new Associate Editor for Physical Chemistry Chemical Physics (PCCP). His research interests are focused on functional polymers, especially the syntheses and applications of conducting polymers and carbon nanomaterials.

Professor Shi has been a professor of Chemistry at Tsinghua University since 2000. In 2004,  he received the 2nd grade award of Natural Science of China and the youth knowledge innovation prize of Chinese Chemical Society and BASF Company.

Professor Shi will start handling papers soon and so we encourage you to submit to his editorial office.

Read some of Professor Shi’s recent articles in PCCP:

Synthesis of gold@carbon dots composite nanoparticles for surface enhanced Raman scattering
Peihui Luo, Chun Li and Gaoquan Shi
DOI: 10.1039/C2CP40767A

Supercapacitors based on self-assembled graphene organogel
Yiqing Sun, Qiong Wu and Gaoquan Shi
DOI: 10.1039/C1CP22409C

High-performance supercapacitor electrodes based on graphene hydrogels modified with 2-aminoanthraquinone moieties
Qiong Wu, Yiqing Sun, Hua Bai and Gaoquan Shi
DOI: 10.1039/C1CP20980A

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