Archive for the ‘Hot Articles’ Category

Destruction and Reconstruction of Nanorods Controlled by Visible Light

Written by Tianyu Liu, University of California, Santa Cruz

Supramolecular smart materials are a family of materials composed of several molecules. They have the ability to change their configurations in response to external stimuli such as the presence of enzymes, light irradiation, and changes in pH. This property can be manipulated for a variety of applications including drug delivery and tissue engineering.

In recent years, pH-responsive supramolecular smart materials have been intensively investigated due to the simplicity of pH alteration. However, adjusting pH can have undesired consequences. First, chemical species other than the supramolecular materials (e.g., acid and base) are needed for tuning pH. The involvement of external reagents hinders the readiness of operation. Additionally, the use of acid and base inevitably introduces waste products, which could eventually suppress the stimulus-response activity of the smart materials. Therefore, developing alternative ways to initiate the configuration modification of the supramolecular smart materials is highly desirable.

In a recent ChemComm. publication, Professor Heng-Yi Zhang, Professor Yu Liu and coworkers from Nankai University, China have developed supramolecular smart nanorods consisting of β-cyclodextrin (β-CD) and 4,4’-bipyridine-coordinated zinc ions. In the presence of protonated merocyanine (MEH) in water, the nanorods are able to dissociate upon visible light illumination and reconstruct themselves when placed in the dark (Figure above).

The method by which these structures can reconfigure involves a light-driven proton transfer process (Figure below). MEH molecules absorb energy from visible light and subsequently release their protons to the surroundings. These free protons then combine with the 4,4’-bipyridine (DPD). The protonated DPD molecules lose their coordination ability and disassemble with zinc ions. As a result, the entire nanorod structure collapses. When no light is present, the aforementioned proton transfer process is reversed and the nanorods are reformed. Such a process is highly reversible with no observable light-responsive activity loss for at least five cycles.

The demonstrated light-responsive supramolecular nanorods enable facile operations with no additional chemicals. This technology opens up endless new opportunities in remote control of light-responsive processes.

To find out more please see:

Light-controlled reversible self-assembly of nanorod suprastructures

Jie Guo, Heng-Yi Zhang, Yan Zhou and Yu Liu

DOI:10.1039/C7CC03280C

 

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Improving Sodium-Ion Batteries for Large-Scale Energy Storage

One of the greatest global challenges is the ever-growing demand for reliable, large-scale energy production.

The depletion of cost-effective fossil fuels and concerns about climate change are driving the need for clean energy sources derived from renewable technologies. Wind and solar power show significant potential as sustainable alternatives however, both solar photovoltaics and wind energy display intermittent output which has led to concerns regarding reliability for global energy production. As a result, there has been an increased demand for the development of large-scale energy storage.

Among energy storage technologies, lithium-ion batteries (LIBs) predominate however lithium’s high cost, abundance, unevenglobal distribution and safety concerns have limited its widespread application. In recent years, researchers have become interested in high energy sodium-ion batteries (SIBs) as a safer and less expensive alternative. Nevertheless, their inferior electrochemical performances, due to the larger size and heavier mass of sodium ions, has become a major hurdle in the development and implementation of SIBs.

In a recent ChemComm publication, Prof. Jun Chen of Nankai University has demonstrated the improved capabilities of SIBs using a manganite hydroxide (MnOOH)-based anode.

In the past, transition metal oxides, such as MnOx-based materials, have been used in LIBs as they possess a high theoretical capacity and—in some cases—improved conductivity. In this study by Chen and co-workers, MnOOH nanorods (figure, top) were synthesized, and were shown to display a higher initial Coulombic efficiency and rate performance compared to MnO2 (a common anode material in LIBs). Cyclic voltammetry (figure, bottom) and various other spectroscopic techniques were used to investigate the electrochemical properties and storage behaviour of MnOOH-SIBs. These experiments showed improvements in charge capacity and overall rate performance when compared to other transition metal oxides and sulfides.

The results of this work show promise toward the fabrication of high-performance SIBs which are encouraging alternatives for energy storage due to sustainable cost, improved thermal stability and transport safety. The performance of SIBs still lags behind that of LIBs but this study, among others, demonstrates that new electrode materials need to be explored in the development of SIBs and solving large-scale energy storage challenges.

To find out more see:

MnOOH nanorods as high-performance anodes for sodium ion batteries
Lianyi Shao, Qing Zhao and Jun Chen
DOI: 10.1039/C7CC00087A


Victoria Corless is currently completing her Ph.D. in organic chemistry with Prof. Andrei Yudin at The University of Toronto. Her research is centred on the synthesis of kinetically amphoteric molecules, which offer a versatile platform for the development of chemoselective transformations with particular emphasis on creating novel biologically active molecules.

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Hydrogen bonds in water clusters catalyse acid rain formation

Hydrogen bonds in water clusters help catalyse acid rain formation via a mechanism more typically found in organic synthesis, new research shows.

Burning fossil fuels, volcanic eruptions and soil bacteria release oxides of sulfur and nitrogen into the air. High in the atmosphere, these oxides transform into sulfuric acid and nitric acid – which falls as acid rain.

Source: © Royal Society of Chemistry
Comparison between a typical bifunctional catalyst in synthetic organic chemistry (left) and the embedded water molecules in the supramolecular complexes (H2O)2⋯SO3 (middle) and (H2O)3⋯SO3 (right). Red = oxygen, grey = carbon, blue = nitrogen, yellow = sulfur, white = hydrogen

 

Sulfuric acid, in particular, forms when sulfur trioxide reacts with atmospheric water. During the reaction, hydrogen bonds organise sulfur trioxide and water into a stable supramolecular complex called an adduct, which facilitates an unusual nucleophilic attack by water. However, the precise mechanism behind this nucleophilic behaviour has long been unclear.

 

Read the full story by Thomas Foley in Chemistry World.


This article is free to access until 17 April 2017.

E Romero-Montalvo et al., Chem. Commun., 2017, DOI: 10.1039/c6cc09616f

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Molecular structure is teixobactin’s pièce de résistance

Study builds scientists’ arsenal against drug-resistant superbugs

Scientists in the UK, Belgium and the Netherlands have gained a crucial understanding of the structure–activity relationship of new antibiotic, teixobactin. Since reports of its discovery in early 2015, researchers have shown it can kill a number of pathogens without them developing resistance to it.

The University of Lincoln’s Ishwar Singh explains that there are several reasons for teixobactin’s potency: ‘It uses multiple modes of action to kill resistant bacteria, this makes it very attractive since, if it worked by only one mode, bacteria could modify more easily. It is much more challenging for bacteria to mutate on multiple levels.’ Teixobactin also targets lipids in the bacteria’s cell walls, which are considered to be less able to mutate and develop resistance.

Read the full story by Hannah Dunckley on Chemistry World.

Source: © Royal Society of Chemistry
Structure of teixobactin and with the D-amino acids highlighted in red

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Sunset for perovskites?

Perovskites have arguably transformed solar energy more in the last few years than other technologies have in decades. But British researchers have called into question optimistic predictions of undiscovered perovskites.

© Shutterstock

Hybrid perovskites are a mix of organic and inorganic ions with the same crystal structure as calcium titanium oxide (CaTiO3). Halide perovskites are a subset of these structures containing halide ions such as fluoride or chloride. Iodide perovskites such as methylammonium lead iodide (CH3NH3PbI3) can convert sunlight to electricity.

Researchers use a decades-old geometric ‘tolerance factor’ to propose new combinations of ions that will form stable perovskites. Now, Robert Palgrave and his team at University College London, UK, have reassessed the validity of the tolerance factor in predicting new hybrid perovskite structures. Read the full article in Chemistry World»


Read the original journal article in Chemical Science – it’s open access:
On the application of the tolerance factor to inorganic and hybrid halide perovskites: a revised system
W. Travis, E. N. K. Glover, H. Bronstein, D. O. Scanlon and R. G. Palgrave 
Chem. Sci., 2016, Advance Article, DOI: 10.1039/C5SC04845A, Edge Article

 
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Iron-rich silicate plays cosmic matchmaker

Computational chemists in Spain have discovered that iron in cosmic dust grains helps turn hydrogen atoms into molecular hydrogen (H2).

The average density of the interstellar medium is several billion times less dense than even the best vacuum chambers on Earth. Collisions between hydrogen atoms are therefore rare, and when they do occur, only one out of every 100,000 creates H2. Read the full article in Chemistry World»


Read the original journal article in ChemComm – it’s open access:
Does Fe2+ in olivine-based interstellar grains play any role in the formation of H2? Atomistic insights from DFT periodic simulations
J. Navarro-Ruiz, P. Ugliengo, M. Sodupe and A. Rimola 
Chem. Commun., 2016, Advance Article, DOI: 10.1039/C6CC02313D, Communication

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Caging chemical weapons

Scientists in the UK have developed supramolecular cages that can trap chemical weapon simulants using the hydrophobic effect.

Organophosphorous chemical weapons, such as sarin and soman, interfere with signals between nerve cells, and have recently been used to deadly effect in places such as Syria. Researchers are therefore trying to develop techniques that detect these chemical weapons in the environment, and destroy them. Read the full article in Chemistry World»


Read the original journal article in ChemComm – it’s open access:
Binding of chemical warfare agent simulants as guests in a coordination cage: contributions to binding and a fluorescence-based response
Christopher G. P. Taylor, Jerico R. Piper and Michael D. Ward 
DOI: 10.1039/C6CC02021F, Communication

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Macrocyle aromaticity switch is all about that base

Researchers have discovered a macrocyle that they can render aromatic, non-aromatic or anti-aromatic by altering the amount of base they add.

 

Meso-aryl expanded porphyrins are usually exceedingly twisted structures due to strong hydrogen bonds within them. Even though they contain many conjugated bonds, this twisted structure means that most of these porphyrins are non-aromatic (to be aromatic, a molecule not only needs conjugation, but must also be flat). Previously scientists had added hydrogen ions to disturb hydrogen bonding in porphyrins, causing them to untwist and become aromatic. Here, a team led by Dongho Kim from Yonsei University, Korea, have flattened a porphyrin by removing hydrogen ions. Read the full article in Chemistry World»


Read the original research in ChemComm – it’s free to read until 20 May 2016:
Multifaceted [36]octaphyrin(1.1.1.1.1.1.1.1): deprotonation-induced switching among nonaromatic, Möbius aromatic, and Hückel antiaromatic species
Won-Young Cha, Takanori Soya, Takayuki Tanaka, Hirotaka Mori, Yongseok Hong, Sangsu Lee, Kyu Hyung Park, Atsuhiro Osuka and Dongho Kim 
DOI: 10.1039/C6CC02051H, Communication

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Fluorescently finding a specific disease marker needle in a biological haystack

The early detection and monitoring of disease is a somewhat recent advancement in healthcare that offers the significant advantage of being able to treat an illness in its initial stages, rather than once it has already manifested itself in the patient. Such a feat requires, however, the ability to see very specific and characteristic disease markers in situ, not unlike the search for a needle in a haystack.
 
Luckily, with the advent of fluorescence (and other) imaging techniques, methods have been developed whereby, in combination with contrast agents that are able to interact with specific molecules in the body, cell chemistry and function can be observed with high sensitivity, and, more importantly, abnormalities in these processes noticed in real time.
 
The art and ultimate success of this fluorescence imaging comes from the design of the contrast agent employed – the probe should be able to selectively recognise and target the relevant disease marker reversibly and under biological conditions. A number of approaches currently exist that meet these requirements, one of which is the boronic acid recognition motif that is able to act as a molecular receptor for the 1,2- and 1,3-diols commonly expressed in carbohydrates and complex glycoproteins. Tony James and his team from the University of Bath, whose own research focuses on such use of boronic acid receptors in the detection of carbohydrates, have summarised the recent and exciting advances in this particular field of selective biological imaging.
 
The well-known and strong affinity of boronic acids for carbohydrates offers a convenient means of detecting commonly expressed markers in diseases including some cancers, as well as Alzheimer’s, autoimmune, and heart diseases. As such, the attachment of this relatively simple chemical moiety to fluorescent small molecular, polymeric or benzoxaborale-based probes offers a diagnostic tool that is able to detect, monitor, and aid in the personalised treatment of such significant and life-changing diseases.
 
This Feature Article convincingly highlights the impact that boronic acid-based fluorescence imaging will ultimately have on a range of important clinical and theranostic practices and their successes.
  
Read this hot ChemComm article in full:
X. Sun, W. Zhai, J. S. Fossey and T. D. James
Chem. Commun., 2016, 52, 3456–3469
DOI: 10.1039/C5CC08633G

About the Writer:
Anthea Blackburn is a guest Web Writer for Chemical Communications. Anthea hails from New Zealand, carried out her graduate studies in mechanostereochemistry under the guidance of Prof. Fraser Stoddart in the US, and has recently relocated to live in London. She is a recent addition to the Econic Technologies team, where she is working on the development of new catalysts for the environmentally beneficial preparation of polycarbonates from CO2.
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Hot ChemComm articles for March

Take a look at this selection of recently published referee-recommended articles – all are free to read* until 17 April.

Printed microelectrodes for scalable, high-areal-capacity lithium–sulfur batteries
Craig Milroy and Arumugam Manthiram
DOI: 10.1039/C5CC10503J, Communication

C5CC10503J GA


Lanthanide-based luminescence biolabelling
Mohamadou Sy, Aline Nonat, Niko Hildebrandt and Loïc J. Charbonnière
DOI: 10.1039/C6CC00922K, Feature Article

C6CC00922K GA


Superior anti-CO poisoning capability: Au-decorated PtFe nanocatalysts for high-performance methanol oxidation
Zhao Cai, Zhiyi Lu, Yongmin Bi, Yaping Li, Yun Kuang and Xiaoming Sun
DOI: 10.1039/C5CC10513G, Communication

C5CC10513G GA


Pharmaceutical nanocrystals confined in porous host systems – interfacial effects and amorphous interphases
N. Sonnenberger, N. Anders, Y. Golitsyn, M. Steinhart, D. Enke, K. Saalwächter and M. Beiner
DOI: 10.1039/C6CC00962J, Communication
From themed collection Pharmaceutical Solids

C6CC00962J GA


Rupture force of cell adhesion ligand tethers modulates biological activities of a cell-laden hydrogel
Min Kyung Lee, Jooyeon Park, Xuefeng Wang, Mehdi Roein-Peikar, Eunkyung Ko, Ellen Qin, Jonghwi Lee, Taekjip Ha and Hyunjoon Kong
DOI: 10.1039/C6CC00036C, Communication

C6CC00036C GA


High-symmetry hydrogen-bonded organic frameworks: air separation and crystal-to-crystal structural transformation
Dong-Dong Zhou, Yan-Tong Xu, Rui-Biao Lin, Zong-Wen Mo, Wei-Xiong Zhang and Jie-Peng Zhang
DOI: 10.1039/C6CC00366D, Communication

C6CC00366D GA

*Access is free through a registered RSC account

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