Journal of Materials Chemistry Blog

 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. 

In 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

A 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.

Professor 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’.

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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

Mark 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]

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.

Advance articles are now going online for our upcoming themed issues on Advanced Hybrid Materials and Modelling of Materials.  Three ‘hot’ articles from these issues have recently been published online and will be free to access for the next four weeks. 

To be included in the themed issue on Advanced Hybrid Materials:

Nano-gold biosynthesis by silica-encapsulated micro-algae: a “living” bio-hybrid material

Clémence Sicard, Roberta Brayner, Jérémie Margueritat, Miryana Hémadi, Alain Couté, Claude Yéprémian, Chakib Djediat, Jean Aubard, Fernand Fiévet, Jacques Livage and Thibaud Coradin*
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM01735C, Paper

Some photosynthetic organisms have the ability to form metal and metal oxide nanoparticles, it is one of the most promising route to “green” nanomaterials.  Thibaud Coradin and co-workers in France took algal cells which exhibit the ability to form gold nano-particles in solution and encapsulated them in silica gels in order to stabilise them for use as a bio-hybrid material.  Entrapped algae maintained their ability to form gold colloids, and, for the first time, it was possible to use Raman spectroscopy imaging for the in situ study of encapsulated cells, opening the route to the design of novel cell-based biosensors

In situ controllable synthesis of magnetite nanocrystals/CoSe₂ hybrid nanobelts and their enhanced catalytic performance

Min-Rui Gao, Shuang Liu, Jun Jiang, Chun-Hua Cui, Wei-Tang Yao and Shu-Hong Yu*
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM01547D, Paper

Platinum-based electrocatalysts are state-of-the-art materials for the O₂ reduction reaction (ORR) in proton exchange membrance fuel cells.  However, due to the expense of platinum and the sluggish ORR kinetics the search is on for next generation ORR electrocatalysts.  Shu-Hong Yu and colleagues in China have demonstrated that a new nanocomposite electrocatalyst, magnetite nanocrystals/CoSe₂ hybrid nanobelts can be easily synthesized by in situ decorating Fe₃O₄ nanoparticles on CoSe₂-DETA nanobelts through a simple thermal reduction process in polyol solution. The resulting functionalized nanobelts present superparamagnetic properties and enhancement for ORR. 

To be included in the themed issue on Modelling of Materials:

Biomimetic chemical signaling across synthetic microcapsule arrays 

Amitabh Bhattacharya and Anna C. Balazs
J. Mater. Chem., 2010, Advance Article
DOI: 10.1039/C0JM01682A, Paper

Using theory and simulation, Amitabh Bhattacharaya and Anna C. Balazs have designed a system of interacting microcapsules that effectively act like a relay: receiving a chemical signal from one capsule and transmitting this signal to another, so that a “message” is propagated over macroscopic distances.  These configurations have the potential to be used to design biomimetic chemical devices, including chemical oscillators, sensors and waveguides.

Interested in reading more?  Read the full texts online by clicking on their title or visiting the Journal of Materials Chemistry.

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Nanostructured tungsten oxide is of great interest due to its broad range of applications such as gas sensors, photocatalysts, electrochromic devices, field-emission devices, and solar-energy devices. In this paper, De Zhang and co-workers in China and Australia report for the first time the synthesis of hierarchical Cu-doped tungsten oxide with distinguished photonic crystal (PC) structures by using Morpho butterfly wings as a hard template. 

The gas sensing properties of the photonic replicas were tested for a range of gases and it was found that the Cu-doped tungsten oxide replicas showed much higher sensitivity to trimethylamine (TMA) than pure tungsten oxide and the replicas with PC structures possess even more enhanced sensitivity to TMA. 

Interested in knowing more?  Read the full article here.

Shenmin Zhu, Xinye Liu, Zhixin Chen, Chunjiao Liu, Chuanliang Feng, Jiajun Gu, Qinglei Liu and Di Zhang*
J. Mater. Chem., 2010, Advance Article DOI:10.1039/C0JM02113J, Paper

Intergranular films (IGFs) are amorphous nanometer-scale thin films that are observed at many grain boundaries in polycrystalline ceramics. IGFs make up only a small volume percent of the bulk ceramic, but their unique local chemistry can strongly influence the macroscopic properties of the material. 

Results of the simulations performed in this study by Stephen H. Garofalini and Yun Jiang show segregation of La ions (arrows) from intergranular film to the prismatic Si3N4 surface; equivalent to HAADF-STEM results.  The simulations and also show the effect of composition on varying segregation and growth.

Interested to know more?  Read the full article:

Yun Jiang and Stephen H. Garofalini, J. Mater. Chem., 2010, DOI: 10.1039/C0JM01555E

Nanoparticles, in sizes under 200 nm, exclusively accumulate into malignant lesions with decreased exposure to other vital organs. This typical property, known as passive targeting, has been utilized for cancer drug targeting.  Porphyrins produce a singlet oxygen under UV exposure to induce tumour cell death. 

In this study, hematoporphyrin attached albumin nanoparticles (HP-ANP) were fabricated and their therapeutic application for lung cancer was evaluated. HP-ANP were further functionalized with gamma-emitting nuclides (99mTc) to demonstrate in vivo imaging and pharmacokinetic properties through scintigraphic imaging. Here, Chang-Koo Shim and colleagues in South Korea have illustrated the possible application of HP-ANP for cancer targeted imaging and therapy.

Interested to know more?  Read the full article here

Su-Geun Yang, Ji-Eun Chang, Byungchul Shin, Sanghyun Park, Kun Na and Chang-Koo Shim, J. Mater. Chem., 2010, DOI:10.1039/C0JM01544J