Archive for October, 2010

Hot Article: New class of high Δε nematic liquid crystals

Polar liquid crystals are key components of mixtures for liquid crystals display (LCD) technologies and compounds that exhibit high dielectric anisotropy (Δε), moderate TNI, and have minimal effect on material’s viscosity are of particular interest for technological applications.

 High Δε nematic liquid crystals: fluxional zwitterions of the [closo-1-CB9H10]− clusterBryan Ringstrand and Piotr Kaszynski
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM02075C, Paper

Bryan Ringstrand and Piotr Kaszynski have developed a new class of nematics with high Δε for display applications and characterized them by thermal and dielectric methods in mixtures with 3 nematic hosts.  These sulfonium zwitterion esters represent a new concept in designing polar additives. They combine the polar zwitterionic fragment that gives rise to a large positive Δε, and shape-shifting ability, which results in high solubility, high effective electric dipole moment µeff, and relatively low contribution to rotational viscosity γ.

Interested in knowing more?  Read the full article here; it will be free to access until the 3rd November.

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Nobel Congratulations to Andre Geim and Kostya Novoselov

The 2010 Nobel prize for physics has been awarded to Professors Andre Geim and Kostya Novoselov, both from the University of Manchester, UK.   Andre and Kostya were awarded the prize for ‘ for groundbreaking experiments regarding the two-dimensional material graphene’, including the discovery that stable graphene can be prepared using sticky tape and graphite!

Since their discovery in 2004, research into graphene has grown considerably, and graphene based materials have been shown to have many potential applications, such as for single molecule gas detection, as transistors, for integrated circuits, as conducting electrodes, bio-devices and antibacterial coatings.

From the Journal of Materials Chemistry Editorial Office and Editorial Board, warm congratulations, Andre and Kostya!

Read Journal of Materials Chemistry articles on graphene here.

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One-step room-temperature synthesis of fibrous polyimide aerogels from anhydrides and isocyanates and conversion to isomorphic carbons

 Aerogels are low-density solids with high open porosity and surface area which have a potential niche in high temperature thermal insulation.  The classic route of synthesis involves two expensive processes, supercritical drying and high temperature imidization. 

One-step room-temperature synthesis of fibrous polyimide aerogels from anhydrides and isocyanates and conversion to isomorphic carbonsIn this study, Nicholas Leventis and co-workers in the USA have described polyimide aerogels synthesized via a low temperature process through the rather underutilized reaction of dianhydrides with diisocyanates.  These polyimide aerogels are compared with those obtained by the classic high-temperature amine route and are shown to be chemically identical but morphologically different.  Overall, the isocyanate route has several distinct advantages over the classic route.

Interested in knowing more?  Read the full article here.

Chakkaravarthy Chidambareswarapattar, Zachary Larimore, Chariklia Sotiriou-Leventis, Joseph T. Mang and Nicholas Leventis
J. Mater. Chem., 2010, Advance Article, DOI: 10.1039/C0JM01844A, Paper

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Aqueous soft matter based photovoltaic devices which mimic leaves and produce electricity

Leaves in sunlightA new type of low-cost, flexible and potentially biocompatible photovoltaic system based on aqueous gel which has the potential for energy generation with minimized environmental pollution has been demonstrated by Orlin D. Velev and colleagues in the USA and South Korea.  The article has received widespread media attention including coverage in the ACS’s Chemical & Engineering News.

Hyung-Jun Koo, Suk Tai Chang, Joseph M. Slocik
Rajesh R. Naik and Orlin D. Velev*
J. Mater. Chem., 2011, Advance Article
DOI: 10.1039/C0JM01820A, Paper

This system consists of two layers of photosensitive ionic dyes infused into a hydrogel which sits between an anode and a cathode.  These dyes capture light and work cooperatively to contribute to the photocurrent generating process both on the surface of the working electrode and in the bulk of the gel.  It was also demonstrated that carbon-coated Cu electrodes could replace the expensive Pt counter electrodes and reduce the production cost without loss of efficiency.

Biomimetic or biocompatible solar cells, inspired by “artificial leaves”, are a novel class of photovoltaics currently being developed which utilise Chlorophyll and photosynthetic reaction centers (Photosystem I and II). This system allows for facile hosting of these naturally derived photosensitive molecules and shows performance comparable with or higher than those of other biomimetic or ionic photovoltaic systems reported recently.

Aqueous soft matter based photovoltaic devicesProfessor Velev explains that  ‘many photoexcitable molecules generate electricity in the right “asymmetric potential” media – used in many organic cells already, but as our medium is water-based it is particularly useful for bioderived molecules’.  However, there are challenges to be solved before these devices can be considered for commercialisation as Professor Velev explains. ‘First, we still have to improve the efficiency of these devices, which is presently very low. Second, we plan to replicate in such devices the ability of the natural leaves to regenerate and replace the organic dye, which will allow us to solve the problems with the long-term stability and performance that are common for all organic photovoltaic devices.  We have clear plans how to address both of these challenges and hope to be able to report the results in future publications’.

This article will be free for the next four weeks! Click here to access it.

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Hot articles: rainbow nanoparticles, atomic layer deposition and liquid crystals

Synthesis and characterization of tunable rainbow colored colloidal silver nanoparticles using single-nanoparticle plasmonic microscopy and spectroscopy

Synthesis and characterization of tunable rainbow colored colloidal silver nanoparticles using single-nanoparticle plasmonic microscopy and spectroscopy

Tao Huang and Xiao-Hong Nancy Xu*
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM01990A, Paper

Tao Huang and Xiao-Hong Nancy Xu have developed a rapid simple one-pot synthesis method to produce twelve representative colloidal Ag NPs that exhibit rainbow colors, ranging from violet to red (full visible range).  They characterized each colloid at single NP resolution and found that the colors of colloids were tunable by controlling the various amounts of sizes and shapes of single NPs. The colloids contained spherical, rod, triangular, and cookie shaped NPs.  These single NPs have the potential for use as multicolored optical probes for the study of dynamic events in solutions and living organisms at nm scale in real time.

Atomic layer deposition of CaB2O4 films using bis(tris(pyrazolyl)borate) calcium as a highly thermally stable boron and calcium source

 Atomic layer deposition of CaB2O4 films using bis(tris(pyrazolyl)borate)calcium as a highly thermally stable boron and calcium sourceMark J. Saly, Frans Munnik and Charles H. Winter*
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM02280B, Paper

Materials containing calcium ions have a wide range of applications. Few reports exist of calcium borate-based thin films and there are only a few deposition techniques.  Atomic layer deposition (ALD) is an emerging thin film deposition method in which gas phase precursors are introduced stepwise to the substrate and are separated by inert purges.  ALD leads to conformal and uniform films with precise thickness control and has been used to coat three dimensional substrates such as nanoparticles, nanotubes, and biotemplates. In this paper, Charles Winter and colleagues report the atomic layer deposition growth of CaB2O4 films using the gas phase precursors CaTp2 and water.

How much can an electric dipole stabilize a nematic phase? Polar and non-polar isosteric derivatives of [closo-1-CB9H10] and [closo-1,10-C2B8H10]

How much can an electric dipole stabilize a nematic phase? Polar and non-polar isosteric derivatives of [closo-1-CB9H10]− and [closo-1,10-C2B8H10]Bryan Ringstrand and Piotr Kaszynski*
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM02876B, Communication

Most liquid crystals of technological importance possess a dipole moment.  Typically, change of the molecular dipole moment is associated with alteration of the molecular geometry and conformational dynamics, which themselves affect phase behavior. Recently, Kaszynski and colleagues suggested that the N+–B fragment can serve as an isosteric polar replacement for the C–C fragment in liquid crystalline molecules, having negligible impact on molecular geometry and dynamics thus any change in phase properties being solely to the molecular dipole.  In this communication, Bryan Ringstrand and Piotr Kaszynski demonstrate for the first time, experimentally, that the replacement of a C–C fragment with a polar isosteric N+–B fragment leads to 5 pairs of non-polar/polar nematics.  Polar nematics, such these are of interest for LCD applications.

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Top Ten most-read Journal of Materials Chemistry articles

Read the most-read Journal of Materials Chemistry articles of August 2010, listed below:

Soo-Kang Kim, Bing Yang, Yuguang Ma, Ji-Hoon Lee and Jong-Wook Park, J. Mater. Chem., 2008, 18, 3376-3384
DOI: 10.1039/B805062G
 
Harald Hoppe and Niyazi Serdar Sariciftci, J. Mater. Chem., 2006, 16, 45-61
DOI: 10.1039/B510618B
 
John C. Hulteen and Charles R. Martin, J. Mater. Chem., 1997, 7, 1075-1087
DOI: 10.1039/A700027H
 
Soo-Kang Kim, Young-Il Park, In-Nam Kang and Jong-Wook Park, J. Mater. Chem., 2007, 17, 4670-4678
DOI: 10.1039/B706606F
 
Clément Sanchez, Beatriz Julián, Philippe Belleville and Michael Popall, J. Mater. Chem., 2005, 15, 3559-3592
DOI: 10.1039/B509097K
 
Suijun Liu, Feng He, Huan Wang, Hai Xu, Chunyu Wang, Feng Li and Yuguang Ma, J. Mater. Chem., 2008, 18, 4802-4807
DOI: 10.1039/B807266C
 
Sasha Stankovich, Richard D. Piner, Xinqi Chen, Nianqiang Wu, SonBinh T. Nguyen and Rodney S. Ruoff, J. Mater. Chem., 2006, 16, 155-158
DOI: 10.1039/B512799H
 
Li Li Zhang, Rui Zhou and X. S. Zhao, J. Mater. Chem., 2010, 20, 5983-5992
DOI: 10.1039/C000417K
 
Stéphane Mornet, Sébastien Vasseur, Fabien Grasset and Etienne Duguet, J. Mater. Chem., 2004, 14, 2161-2175
DOI: 10.1039/B402025A
 
Wei-De Zhang, Bin Xu and Liao-Chuan Jiang, J. Mater. Chem., 2010, 20, 6383-6391
DOI: 10.1039/B926341A
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