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HOT Chem Soc Rev articles for June-August 2013

23 Sep 2013

Photonic crystal fibres for chemical sensing and photochemistry
Ana M. Cubillas, Sarah Unterkofler, Tijmen G. Euser, Bastian J. M. Etzold, Anita C. Jones, Peter J. Sadler, Peter Wasserscheid and Philip St.J. Russell
Chem. Soc. Rev., 2013, Advance Article
DOI: 10.1039/C3CS60128E, Review Article
Part of our upcoming themed issue: Chemical and biological detection

Free to access until 20th October 2013

Magnetic nanoparticles as contrast agents in the diagnosis and treatment of cancer
Juan Gallo, Nicholas J. Long and Eric O. Aboagye
Chem. Soc. Rev., 2013,42, 7816-7833
DOI: 10.1039/C3CS60149H, Review Article

Free to access until 20th October 2013

Salt melt synthesis of ceramics, semiconductors and carbon nanostructures
Xiaofeng Liu, Nina Fechler and Markus Antonietti
Chem. Soc. Rev., 2013, Advance Article
DOI: 10.1039/C3CS60159E, Review Article

Free to access until 20th October 2013

Be squared: expanding the horizon of squaric acid-mediated conjugations
Frederik R. Wurm and Harm-Anton Klok
Chem. Soc. Rev., 2013, Advance Article
DOI: 10.1039/C3CS60153F, Review Article

Free to access until 20th October 2013

Chemistry and formulations for siRNA therapeutics
Andrzej Gallas, Cameron Alexander, Martyn C. Davies, Sanyogitta Puri and Stephanie Allen
Chem. Soc. Rev., 2013, Advance Article
DOI: 10.1039/C3CS35520A, Tutorial Review

Free to access until 20th October 2013

Breaking the concentration limit of optical single-molecule detection
Phil Holzmeister, Guillermo P. Acuna, Dina Grohmann and Philip Tinnefeld
Chem. Soc. Rev., 2014, Advance Article
DOI: 10.1039/C3CS60207A, Tutorial Review
Part of our upcoming themed issue: Single-molecule optical spectroscopy

Free to access until 20th October 2013

THAT’S NOT ALL! Click here for more free HOT Chem Soc Rev articles for June-August!

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Metrics for characterising N-heterocyclic carbenes

26 Jul 2013

The chemistry of stable carbene molecules has been of interest to me for many years, from an undergraduate lecture on organometallic chemistry to recent research on diamond chemistry and surface modification.

Unlike their unstable counter-parts, the stable versions have controllable and versatile chemistry. This has led to the creation of hundreds of these stable carbenes for various applications. The overwhelming literature on the topic makes it difficult to compare carbene chemistry, introduce oneself to the field, or pick suitable carbenes for any given application.

Recently, navigating the literature has been made easier for one class of carbenes – the N-heterocyclic carbenes. David J. Nelson¹ and Steven P. Nolan have written a HOT review in Chemical Society Reviews which categorizes N-heterocyclic carbenes based on their steric and electronic properties.

They do so with the aid of chemical ‘metrics’, deriving from NMR, IR, electrochemical and computational data. Each metric enables different features of carbene chemistry to be probed. For example, parameters derived from IR data are used to quantify the extent of d to π* backbonding between the carbene and a metal centre. In this manner, the results of over 300 N-heterocyclic carbenes have been filtered by the authors to further a comprehensive understanding of N-heterocyclic carbene chemistry.

This review is valuable to the newcomer and experienced carbene chemist, alike. It lays the framework for a more systematic approach to carbene chemistry, in which the molecules are tailored for specific organometallic, catalytic, and surface chemistry.

1. No relation to the author of the blog

Read this Chem Soc Rev Review article in full:
Quantifying and understanding the electronic properties of N-heterocyclic carbenes
David J. Nelson and Steven P. Nolan
Chem. Soc. Rev., 2013, Advance Article
DOI: 10.1039/C3CS60146C

Geoff Nelson is a new guest web-writer for Chemical Science. He currently works as a post-doctoral research associate in Dr David Payne’s research group in the Department of Materials at Imperial College, London. Geoff’s current research concerns the synthesis and characterization of post-transition metal oxides for use in the energy sector. His other research interests include carbon-based materials, biophysical chemistry, electrochemistry, and surface science.

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New clarity in the mechanism for lithium salt-free Wittig reactions

27 May 2013

The Wittig reaction was first reported in 1954 and awarded the Nobel Prize in 1979. Today, it is widely used for the preparation of alkenes by reaction of a carbonyl compound with a phosphonium ylide. Despite its age and broad utility, differing mechanisms for the Wittig reaction still feature in the literature and textbooks.

Peter Byrne and Declan Gilheany at University College Dublin have written a substantial review of this transformation, which provides definitive evidence regarding the mechanism of lithium salt-free Wittig reactions of phosphonium ylides.

Phosphonium ylides can be represented in either ylide (1a) or ylene (1b) form and they are classified according to their substitution at the α-carbon. The P–C bond of a phosphonium ylide is heavily polarised towards carbon and so ‘R’ groups that offer a greater degree of conjugative stabilisation increase the overall stabilisation of the ylide. Additionally, the nature of the ‘R’ group influences the selectivity for formation of Z or E alkenes.

The mechanism that features in many undergraduate textbooks involves the attack of the carbonyl carbon by the nucleophilic ylide α-carbon to form a betaine intermediate (7), which undergoes ring closure to form an oxaphosphetane (OPA) (8) and subsequently decomposes to form the product alkene (9) and a phosphine oxide (10) by-product.

Byrne and Gilheany present a body of evidence that disputes this mechanistic pathway and instead supports an irreversible [2 + 2] cycloaddition between the ylide and carbonyl compound to directly form the OPA (8). The OPA then decomposes in a stereospecific manner, meaning that the stereochemistry of the alkene product is determined by the shape of the transition state for the [2 + 2] cycloaddition, and hence the structure of the OPA. The E-selectivity commonly observed in the case of semi-stabilised and stabilised ylides is explained by a kinetic preference for the formation of trans-OPA, which decomposes to form the E-alkene.

This clarification of the mechanism for the lithium salt-free Wittig reaction will likely feature in future editions of undergraduate textbooks and will encourage many chemistry lecturers to update their course notes before the start of the new academic year.

For more, read this HOT Chem Soc Rev Review Article in full:

The Modern Interpretation of the Wittig Reaction Mechanism
Peter A. Byrne and Declan G. Gilheany
Chem. Soc. Rev., 2013, Advance Article
DOI: 10.1039/C3CS60105F

Alice Williamson is a guest web-writer for Chem Soc Rev. She is currently a postdoc for the OSDDMalaria Project in Dr. Matthew H Todd’s group at the University of Sydney.

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The ins and outs of enzyme immobilisation: a Tutorial Review

14 May 2013

Great attention is focused on the burgeoning role of biocatalysis in industrial processes. Enzymes offer a mild, efficient and “green” process that can save money, conserve energy and cut down on waste compared to conventional chemistry. However, despite their advantages, the implementation of enzymatic processes in industry suffers from a number of limitations. Enzymes are often unstable to the industrial or storage conditions, and can be difficult to recover and re-use.

Enzyme immobilisation is one way to combat these drawbacks. In addition to facilitating the storage, recovery and re-use of an enzyme, immobilisation also affords the more convenient handling of the enzyme as well as reducing its toxicity in cases. As part of Chem Soc Rev‘s upcoming ‘Enzyme Immobilisation’ themed issue, Professor Roger A. Sheldon and Dr. Sander van Pelt of Delft University of Technology have produced a Tutorial Review shedding light on the role of this key application in biocatalysis.

Enzyme Immobilization: Why, What and How | Roger A. Sheldon

The Tutorial Review – which is accompanied by additional PDF slides in the electronic supplementary information (ESI) – highlights a number of key learning points, including the advantages and limitations of the various approaches to enzyme immobilisation. The types of immobilisation are discussed in detail, from binding to a carrier, to entrapment and cross-linking, including cross-linked enzyme aggregates (CLEAs). Helpfully, Sheldon and von Pelt also clarify immobilisation terminology, which is often confusing and inconsistent.

Given the potential of this technology, especially in the chemical industry, it is essential that we gain more insight into the performance and application of immobilised enzymes. This Tutorial Review is a step towards that objective and offers an enlightening overview of this fascinating subject.

For more, read this Chemical Society Reviews article today:

Enzyme immobilisation in biocatalysis: why, what and how
Roger A. Sheldon and Sander van Pelt
Chem. Soc. Rev., 2013, Advance Article
DOI:10.1039/C3CS60075K

Ruth Gilligan is a guest web-writer for Chem Soc Rev. She has recently completed her PhD in the group of Prof. Matthew J. Gaunt at the University of Cambridge, focusing on the development and application of C–H functionalisation methodology.

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Smart wormlike micelles react to their environment

22 Apr 2013

An exciting challenge for soft matter chemists is the development of smart materials that can respond to “triggers” from their environment. By using materials which form by supramolecular self assembly, researchers can use very simple building blocks to create sophisticated materials, which can be applied in key areas such as diagnostics, biosensors, drug delivery, tissue engineering and smart optical systems.

This Chem Soc Rev review by Zonglin Chu, Cécile Dreiss and Yujun Feng describes the potential and application of stimuli-responsive “wormlike micelles” (WLMs). These are long, flexible structures assembled from molecules that contain both hydrophilic and hydrophobic areas, and so assemble into a wide range of micellar structures in an aqueous environment. Under certain conditions, these structures are constantly breaking and reforming, and are referred to as “living.” Small changes in the environment can offset this balance and cause large changes to the properties of the material.

One fascinating example reviewed by Chu, et al. is the thermo-responsive gel system reported by Huang and co-workers in 2009 (see figure below). At 21 °C, this system is a transparent fluid, but cooling it to 20 °C results in the formation of a gel. This is a drastic, reversible change in response to a small modification of the environment.

Figure taken from Y. Lin et al., Soft Matter, 2009, 5, 3047-3053.

This Review provides an in-depth coverage of recent advances in the development of interesting wormlike micelle systems, including systems which can be switched “on” and “off” by electrical, optical, thermal and pH triggers, and an excellent understanding of WLM behaviour and their practical applications.

Read this Chemical Society Reviews article today:

Smart wormlike micelles
Zonglin Chu, Cécile A. Dreiss and Yujun Feng
Chem. Soc. Rev., 2013, Advance Article
DOI: 10.1039/C3Cs35490C

Cally Haynes is a guest web-writer for Chem Soc Rev. She is currently a post doctoral researcher at the University of Southampton, and her research interests include the supramolecular chemistry of anions. When not in the laboratory, she likes travelling and watching football.

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Another europium crisis? Clarifying misconceptions on the spectra of lanthanides

17 Apr 2013

Thinking about electronic spectra, spins and orbitals takes me back to my good old undergraduate days, when denim jackets worn with jeans were cool and having predictive text meant you had a top-of-the-range phone, and I would sit with my brain burning with wonder and confusion (and probably a small hangover) as these concepts and theories would be explained to me by the lecturer, affectionately nicknamed Disco Dave; so-called for the the entanglements and angles that his fingers and arms would get into, trying to explain such things. And it worked.

Well, Disco Dave may be retired now but Peter Tanner, a well-known analytical chemistry expert from the Hong Kong Institute of Education, has published a Tutorial Review in Chem Soc Rev that looks to clarify misconceptions regarding the electronic spectra of tri-positive europium and cerium. Tri-positive europium has attracted attention due to its potential application in sensors and time-gated bioimaging agents based on its optical emission spectra. Tanner’s review gives the background to the electronic states, energy levels and transition intensities of lanthanide ions, and describes how to interpret the emission spectra of tri-positive europium in the solid state.

Professor Tanner has written this review to address, he says, the inaccurate descriptions of these spectra that are being amplified throughout the literature. One such inaccuracy is the misuse of the term ‘Stokes shift.’ (This must be the chemistry equivalent of doing ‘hip hop’ moves to the disco tune ‘Saturday Night Fever.’) The spectral properties 4f^N-4f^N lanthanide ions are often referred to, in the literature, to have large Stokes shifts; Professor Tanner explains that it is quite the contrary. The Stokes shifts involved in such transitions are negligible, he explains, as the vibrational progressions are very weak and the maximum intensity lies in the 0-0 band. In his Tutorial Review, we discover the alternative terms, Richardson shift and Denning shift, which are perhaps more appropriate– more consistently ‘disco.’

Read this HOT Chem Soc Rev Tutorial Review to find out more!

Some misconceptions concerning the electronic spectra of tri-positive europium and cerium
Peter A. Tanner
Chem. Soc. Rev., 2013, Advance Article
DOI: 10.1039/C3CS60033E

Sarah Brown is a guest web-writer for Chem Soc Rev. Sarah hung up her lab coat after finishing her PhD and post-doctorate in nanotechnology for diagnostics and therapeutics, to become an assistant editor at the BMJ Publishing Group. When not trying to explain science through ridiculous analogies, you can often find her crocheting, baking or climbing, but not all at once.

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Biosensors – A personal overview by Anthony Turner

15 Apr 2013

With tens of thousands of papers published in the area of biosensors, it can be a daunting task to try and get a foothold in the literature. There are many excellent review articles on the subject that can help, and Anthony Turner’s new Tutorial Review is a very fine place to start your exploration of the field. It is based on his Theophilus Redwood Medal and Award lectures and is open access– more reasons to have a look.

Anthony Turner was project director for MediSense’s in vitro diagnostics programme where he led the team that created the mediated amperometric enzyme electrode for glucose sensing, the world’s most successful biosensor. Glucose detection is a tale of how a dozen scientists working in small, lightly equipped labs sowed the seeds for a multi-billion dollar global industry. The review also casts a look towards future developments in the area, including the possibility of an all-printed biosensing system.

The future of biosensors: an all-printed system.

The market for glucose sensing accounts for the vast majority of the $13 billion biosensor market but, rather than viewing this as the only market for developments in biosensors, Turner suggests it should serve as a model to be copied for the hundreds– if not thousands– of alternative analytes to be detected. The need for robust inexpensive diagnostics in the developing world and the development of personal health accounts in the developed world will drive biosensor research towards alternative analytes and beyond glucose.

This review contains a history of the most commercially successful biosensor to date, the current state-of-the-art, and a look at future possibilities that is grounded in the lessons learnt from a lifetime working in the biosensor field. For these reasons, this is a review that you should read today.

For more, read this Open Access Chem Soc Rev Tutorial Review today!

Biosensors: sense and sensibility
Anthony P. F. Turner
Chem. Soc. Rev., 2013, 42, 3184-3196
DOI: 10.1039/C3CS35528D

Iain Larmour is a guest web-writer for Chem Soc Rev. 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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Power is nothing without control: Smart, polymeric, thermally-responsive nanoparticles

11 Apr 2013

In this Review, which forms part of the upcoming Chem Soc Rev themed issue on Stimuli Responsive Materials, Rachel K. O’Reilly and Matthew I. Gibson, from the Department of Chemistry at the University of Warwick, give an account of the factors involved in the design, characterisation and function of thermally responsive polymeric nanoparticles.

This review is concerned with a class of synthetic polymer, which have a lower critical solution temperature, the macroscopic result of which is a cloud point, accompanied by a structural change from coil to globule. A variety of LCST type thermoresponsive polymers are discussed in the review, including poly-N-vinylpiperidone, poly-oligoethyleneglycol-methacrylate, two substituted polyacrylamide polymers and also an elastin side chain polymer.

Phase transitions for polymers with lower and upper critical solution temperatures, common synthetic methodologies

Synthetic protocols described are self-assembly driven by hydrophobic or hydrophilic interactions and the grafting from or grafting to approaches, leading to a spherical, corona type assembly of thermally responsive polymer units, bound to a micelle, vesicle or inorganic nanoparticle such as silica, gold, iron oxide or polymeric colloid.

A large body of knowledge in the area of polymer brush functionalised flat surfaces is used as a comparison to the behaviour of the thermally responsive nanoparticles. Similar synthetic approaches are employed here too, which are well understood via complimentary analytical techniques such as Atomic Force Microscopy, ellipsometry, and Quartz Crystal Microbalance analysis.

Emphasis is put on the importance of accurate determination of the cloud point. Examples are given of systems where significant differences in cloud point are observed, depending on whether the polymer is free in solution, or bound to a surface or nanoparticle. The use of Dynamic Light Scattering is shown to be a useful probe of aggregation or shrinkage properties, occurring upon heating. It is described how this adds to the understanding of the effect of various synthetic routes and polymerization methodologies on resultant properties.

Applications of such responsive materials are highlighted in the areas of enzyme function and solubility switching, and also in drug encapsulation and delivery. The nanoparticle response may also be achieved by a secondary stimulus, such as a pH change, or salt environment, when temperature remains constant.

Overall, this is a highly interesting insight into a complex area with huge potential, which will prove to be an important reference point for researchers in this field.

Read this HOT Chem Soc Rev article today!

To aggregate, or not to aggregate? considerations in the design and application of polymeric thermally-responsive nanoparticles
Matthew I. Gibson and Rachel K. O’Reilly
Chem. Soc. Rev., 2013, Advance Article
DOI: 10.1039/C3CS60035A

Kevin Murnaghan is a guest web-writer for Chem Soc Rev. He is currently a Research Chemist in the Adhesive Technologies Business Sector of Henkel AG & Co. KGaA, based in Düsseldorf, Germany. His research interests focus primarily on enabling chemistries and technologies for next generation adhesives and surface treatments. Any views expressed here are his personal ones and not those of Henkel AG & Co. KGaA.

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Spotting Quantum Mechanics at Work in Biological Systems

22 Feb 2013

Quantum mechanical predictions reduce to those of classical mechanics in the macroscopic world; otherwise absurd situations would result such as Schrödinger’s cat being both dead and alive in the box. But does quantum mechanics play a specific role in the functions of complex biological systems?

An advance in the study of the photosynthetic light-harvesting process demonstrated that the electronic energy transfer might not follow the classical hopping mechanism but involve quantum-coherent energy transfer. This discovery relied on the development of new ultrafast spectroscopic techniques and these form the basis of this Tutorial Review by Elisabetta Collini from the Department of Chemical Sciences at the University of Padova.

a) Hopping and b) quantum coherent energy transfer mechanisms.

The state-of-the-art techniques, and their limitations, for the detection of quantum-coherent energy transfer in light-harvesting complexes are discussed. They include; pump-probe anisotropy, two-time anisotropy decay and 2D photon echo techniques.

Although the review focuses on photosynthetic energy transfer, quantum effects have been posited in other processes including; olfaction, magnetic sensing and even consciousness. The extent to which quantum mechanics affect these processes in physiological conditions has often been seen as a negligible curiosity.

This Tutorial Review explores the techniques, including the debate surrounding their use, for the experimental verification of the role of quantum effects in biological processes. It is therefore a must read for those who wish to experimentally explore quantum mechanical effects in other biological processes.

Related slides on “Energy Transfer in the Weak and Strong Coupling Regimes” are also available as electronic supplementary information (ESI) – these are free to access.

For more, read this Chem Soc Rev article today:

Spectroscopic signatures of quantum-coherent energy transfer

Elisabetta Collini
Chem. Soc. Rev., 2013, Advance Article
DOI: 10.1039/C3CS35444J

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Chemical Society Reviews Blog

Archive for the ‘Hot Articles’ Category

HOT Chem Soc Rev articles for June-August 2013

Metrics for characterising N-heterocyclic carbenes

New clarity in the mechanism for lithium salt-free Wittig reactions

The ins and outs of enzyme immobilisation: a Tutorial Review

Smart wormlike micelles react to their environment

Another europium crisis? Clarifying misconceptions on the spectra of lanthanides

Biosensors – A personal overview by Anthony Turner

Power is nothing without control: Smart, polymeric, thermally-responsive nanoparticles

Spotting Quantum Mechanics at Work in Biological Systems

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