Journal of Materials Chemistry Blog

Thin-films of semi-conducting polymers, which are used in the production of light emitting diodes (LEDs) and organic photovoltaic (OPV) devices, are commonly prepared by a spin coating method. The performance of these films is highly dependent on their final morphology; however understanding and exercising control over the formation of film morphologies has previously been challenging.

In this hot paper, Howse and co-workers used high speed stroboscopic fluorescence microscopy to observe directly the development  of phase separated structures in poly(styrene) and poly(9,9’-dioctylfluorene) blends during the spin-coating process. Their feedback-modulated spin coating technique enabled unprecedented control over the thin-film morphology, and presents a route towards increased efficiency in the manufacture of LED and OPV devices.

Directed phase separation of PFO:PS blends during spin-coating using feedback controlled in situ stroboscopic fluorescence microscopy

J. Mater. Chem. A, 2013, 1, 3587-3592 DOI: 10.1039/C3TA01530K

Follow the latest journal news on Twitter @JMaterChem or go to our Facebook page.

To keep up-to-date with all the latest research, sign-up to our RSS feed or Table of contents alert.

Functionalisation of graphene by adsorbed single-stranded DNA (ssDNA) enables the dispersion of graphene in aqueous solution.  The resulting composites are of great interest as biomaterials with applications in areas such as molecular diagnostics, biosensors and DNA sequencing. Hence, there is much to be gained from an improved understanding of the interaction between graphene and ssDNA.

In this hot paper, Manna and Pati use atomistic molecular dynamics (MD) simulation and density functional theory (DFT) to investigate the structural topology, energetics and electronic structure of ssDNA hybridized with graphene.  They find the adsorption process is influenced by competing π–π stacking interactions, which are highly dependent on the chemical nature of the nucleobase and the sequence type of the ssDNA.  Mixed nucleobase sequence ssDNA is proposed as a better candidate for dispersing graphene than ssDNA containing homologous base sequences.

This research provides a fundamental understanding of the adsorption of ssDNA on graphene, and therefore has important implications for the design of graphene-based biomaterials.

Theoretical understanding of single-stranded DNA assisted dispersion of graphene
J. Mater. Chem. B, 2013, 1, 91-100 DOI: 10.1039/C2TB00184E

Follow the latest journal news on Twitter @JMaterChem or go to our Facebook page.

To keep up-to-date with all the latest research, sign-up to our RSS feed or Table of contents alert.

The use of antitumour drugs has always been problematic due to the risk of severe side-effects consistent with such cytotoxic compounds. A logical method of reducing side effects is to exercise more control over the deployment of drugs, ensuring that they are only delivered to cancer cells and not across the entire body. The first stage in the development of such a system is the design of biocompatible drug carriers.

Drug carriers must be designed in such a way that they do not interfere with the therapeutic action of the drug yet also be sufficiently resilient that their payload is not released before their cellular destination. A solution to this is to use a chemical trigger that exploits differences in the extracellular and intracellular environments. One such difference is redox potential. Inside the cell, the concentration of the thiol-containing tripeptide glutathione (GSH) is around one order of magnitude higher than it is outside the cell. Disulfides (-S-S-) can be rapidly degraded by GSH meaning that structures that contain them are extremly unstable inside the cell yet remain completely stable in the mildly oxidising conditions found in the extracellular milieu.

Ding et al. prepared micelles consisting of poly(ethylene glycol) (PEG) and poly(ε-benzyloxycarbonyl-L-lysine) (PZLL) linked by a disulfide group. Upon entering the cell, it was envisaged that the fission of the disulfide would greatly undermine the structural integrity of the micelle. The carriers formed were of the order of 100 nm in size and were loaded with the drug Doxorubicon (DOX). In a non-reducing environment more than 50% of the drug was held after sixty hours; in the presence of GSH less than 10% was held demonstrating the effectiveness of the trigger. In vitro efficacy of the micelles was demonstrated using cellular imaging and the biocompatibility of the micelles was found to be extremely high.

Biocompatible reduction-responsive polypeptide micelles as nanocarriers for enhanced chemotherapy efficacy in vitro

J. Mater. Chem. B, 2013, 1, 69.  DOI: 10.1039/c2tb00063f

James Serginson is a guest web writer for the Journal of Materials Chemistry blog. He currently works at Imperial College London carrying out research into nanocomposites.

To keep up-to-date with all the latest research, sign-up to our RSS feed or Table of contents alert.

This Highlight Article by Chaikittisilp, Ariga and Yamauchi reviews the recent progress in the preparation of novel MOF-derived nanoporous carbons and their potential applications in energy and environmental related areas. The authors discuss the general utilization of MOFs as sacrificial templates, how functionalisation of MOF-derived nanoporous carbon is achieved and the direct carbonisation of MOFs. The authors also highlight the energy and environmental related utilisations of these materials and provide a future outlook for this hot area of research.

A new family of carbon materials: synthesis of MOF-derived nanoporous carbons and their promising applications
J. Mater. Chem. A, 2013,1, 14-19.  DOI: 10.1039/c2ta00278g (free to read for a short time)

Follow the latest journal news on Twitter @JMaterChem or go to our Facebook page.

To keep up-to-date with all the latest research, sign-up to our RSS feed or Table of contents alert.

Dendrimers (or apparently “arborols” for those who prefer nomenclature with a Latin flavour) offer some of the most fascinating molecular architectures in chemistry. Molecules such as PAMAM are robust, well defined spherical structures with several possible applications in the fields of sensors and drug delivery. They also provide the opportunity for chemists to produce some first-rate molecular models.

Fans of photogenic chemistry will now be pleased to hear that dendritic architectures have recently been observed in samples of another journal cover mainstay: the carbon nanotube.

The usefulness of composite materials prepared by introducing carbon nanotubes (CNTs) into a bulk polymer is well known; mechanical properties, conductivity and thermal properties can all be improved greatly. There is unfortunately a problem with getting the tubes sufficiently well dispersed throughout the polymer. Kobashi et al. have recently published work showing  the  formation and dispersion of a dendritic network of CNTs that is strikingly reminiscent of the structure of a tree or a circulatory system. The tubes form large, central “trunks” and then branch off again and again until, at the extremities of the network, only single tubes are visible.

The structures are not only aesthetically pleasing; they are also extremely useful. Use of the network allows a ten-fold increase in the conductivity of a rubber composite compared to individually dispersed tubes. When combined with epoxy resins the network was also able to improve the Young’s Modulus of the material (by 200% to 5.6 GPa) and the tensile strength (by 170% to 85 MPa). To prepare the networks the researchers use long (0.1 – 1 mm) tubes which are flexible and entangled. The nanotube forests (“carpets” of vertical tubes grown off a flat surface) are also imperfectly aligned which is believed to cause the required “meshes” instead of bundles. It is also envisaged that this novel method of CNT dispersion is scalable offering the potential for use in industry.

A dispersion strategy: dendritic carbon nanotube network dispersion for advanced composites

Chem. Sci., 2013, 4, 727.  DOI: 10.1039/c2sc21266h

James Serginson is a guest web writer for the Journal of Materials Chemistry blog. He currently works at Imperial College London carrying out research into nanocomposites.

To keep up-to-date with all the latest research, sign-up to our RSS feed or Table of contents alert.

This Feature Article by Jose Manuel Valverde from the University of Seville, reviews Ca-based adsorbents for post-combustion carbon capture in Ca-looping processes. This process involves the carbonation reaction of CaO to capture CO₂, followed by calcination of limestone to regenerate the sorbent. The author discusses several topics, including: strategies for reactivation of natural limestones, Ca-based sorbents from synthetic precursors, the use of nanomaterials, the performance of sorbents under harsh calcination conditions, SO₂/CO₂ capture efficiency and physical methods to enhance CO₂ capture performance.

(Featured on the inside front cover of Issue 3 of J. Mater. Chem. A)

Ca-based synthetic materials with enhanced CO₂ capture efficiency
J. Mater. Chem. A, 2013, 1, 447-468.  DOI: 10.1039/c2ta00096b (free to read for a short time)

Follow the latest journal news on Twitter @JMaterChem or go to our Facebook page.

To keep up-to-date with all the latest research, sign-up to our RSS feed or Table of contents alert.

Nonviral vector-based delivery of genetic information into cells to manipulate their protein expression is of great interest for applications in regenerative medicine and the treatment of genetic diseases. Nanoparticles are a type of nonviral delivery vehicle that can be employed; however their contact with cells is, too a large extent, a diffusion limited process. Using magnetic forces to pull magnetic nanoparticles towards target cells is an established technique to overcome this. However, this can have the drawback that the nanoparticles form overly tight complexes with DNA, which can inhibit gene release. Stimuli-responsive polymer vectors can be used to tune DNA unpacking, by adapting to microenvironmental changes such as temperature, pH, light and redox.

In this hot paper, scientists from Tianjin University describe the preparation of magnetic/thermoresponsive nonviral vectors in the form of monodispersed magnetic nanoparticles (MNPs). The authors investigate the physicochemical properties of the MNP-polymer brushes/DNA nanocomplexes and the in vitro gene transfection of the MNPs-polymer brushes under a magnetic field with variable temperature conditions. Co-application of magnetic field and temperature stimuli was shown to enhance gene transfection efficiencies.

Combining magnetic field/temperature dual stimuli to significantly enhance gene transfection of nonviral vectors
J. Mater. Chem. B , 2013,1, 43-51.  DOI: 10.1039/c2tb00203e (free to read for a short time)

Follow the latest journal news on Twitter @JMaterChem or go to our Facebook page.

To keep up-to-date with all the latest research, sign-up to our RSS feed or Table of contents alert.

Metal-organic frameworks (MOFs) are a class of well-known crystalline compounds at the bridge of organic and inorganic chemistry. MOFs have many potential applications such as in gas storage and catalysis. They also have potential applications as semiconductors in photovoltaics, photo-emitters and transistors.

In this hot paper, researchers from the University of Bath, UK use DFT calculations to predict novel hybrid MOFs with desirable semiconductor properties. They expand on the ubiquitous II-VI and IV-VI semiconductors (e.g. CdS, ZnSe, PbTe) and investigate their corresponding hybrid organic-inorganic analogues based on the archetype 3D framework of Pb₃(C₆S₆). Five hybrids were found to be of interest because they have a negative formation enthalpy and band gaps predicted to be in the visible light spectrum. Thus, these five hybrids may have applications as photo-active materials.

Thermodynamic and electronic properties of tunable II–VI and IV–VI semiconductor based metal–organic frameworks from computational chemistry

J. Mater. Chem. C, 2013, Advance Article.  DOI: 10.1039/c2tc00108j (free to read for a short time)

Follow the latest journal news on Twitter @JMaterChem or go to our Facebook page.

To keep up-to-date with all the latest research, sign-up to our RSS feed or Table of contents alert.

Acetylene is widely known for its use as a fuel in welding equipment and it is also a very important building block in industrial chemical synthesis. Unfortunately, obtaining high-purity acetylene is not a trivial matter. Removing methane and carbon dioxide via cryogenic distillation is extremely energy intensive due to the low temperature required and therefore a process that avoids the need for such cooling is extremely attractive.

Hui Xu et al. have recently demonstrated the effective purification of acetylene at room temperature and pressure through the use of a microporous metal-organic framework, Cu₆(PDC)₆ ^. 2.6H₂O (PDC = 3,4-pyridine-dicarboxylate). Known as UTSA-50, the material was designed such that its pores are not only optimally sized for gas storage but that they also contain both exposed metal atoms and pyridyl groups. This enables both electrostatic and hydrogen-bonding interactions with acetylene. The latter are thought to be the key to selectivity given the ability of pyridyl nitrogen atoms to form hydrogen bonds with acetylene but not with CO₂ or CH₄.

At 296 K and 1 atm the UTSA-50 framework can adsorb 91 cm^-1 g^-1 acetylene which is comparable to other materials with similar pore size and surface area. Henry’s law selectivities of 68.0 and 13.3 for acetylene over carbon dioxide and methane, respectively, are extremely promising. In fact, the selectivity for CO₂ is, according to the authors, the highest ever reported.

A microporous metal-organic framework with both open metal and Lewis basic pyridyl sites for highly selective C₂H₂/CH₄ and C₂H₂/CO₂ gas separation at room temperature

J. Mater. Chem. A, 2013, 2, 77.  DOI: 10.1039/c2ta00155a

James Serginson is a guest web writer for the Journal of Materials Chemistry blog. He currently works at Imperial College London carrying out research into nanocomposites.

To keep up-to-date with all the latest research, sign-up to our RSS feed or Table of contents alert.