Journal of Materials Chemistry Blog

Hydrogen holds immeasurable promise in our search for alternative, sustainable, cleaner fuels. However, the simple, cheap production of hydrogen is still proving a problem. Water photolysis is a great way to achieve pure H₂ and as O₂ is the only side product it does not result in the harmful greenhouse gas emissions that arise from using hydrocarbons to produce H₂. Unfortunately, the generation of H₂ by water photolysis is challenging as the reaction that forms O₂ is much slower than the H₂ forming reaction. The use of an efficient photocatalyst can significantly improve the success of this process.

This paper by Moniz et al. details the development of just such a photocatalyst. In this work a bimetallic BiFeO₃ catalyst is prepared using a novel method of Aerosol Assisted Chemical Vapour Deposition (AA CVD). This is the first time that this method has been used to prepare a photocatalyst of this type. The team go on to test this photocatalyst for the electrolysis of water using both UV and solar irridation and encouragingly, activity is confirmed for the BiFeO₃ catalyst. Even more impressively the catalyst greatly outperforms both a commercially available photocatalyst (TiO₂ Activ^® glass) and another recently published photocatalyst (B-doped TiO₂ films).

The novel synthetic methodology presented in this paper enables large area thin film deposition and as a result has potential for high volume applications in the future.

A simple, low-cost CVD route to thin films of BiFeO₃ for efficient water photo-oxidation

Savio J. A. Moniz, Raul Quessada-Cabrera, Christopher S. Blackman, Junwang Tang, Paul Southern, Paul M. Weaver and Claire J. Carmalt,
J. Mater. Chem. A, 2014, 2, 2922-2927 C3TA14824F

H. L. Parker is a guest web writer for the Journal of Materials Chemistry blog. She currently works at the Green Chemistry Centre of Excellence, the University of York.

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Targeted drug delivery has developed greatly over the past fifty years although it remains a largely uncontrolled exercise. In general, even the most effective vectors rely on passive targeting analogous to a driver travelling from Land’s End to John o’ Groats by making random turns until they see a sign saying “Welcome to John o’ Groats”.

Nano- and microrobots have the potential to offer a more guided method of drug delivery as well as facilitating new approaches to non-invasive surgery and diagnosis. A recent paper by Qiu et al. describes the preparation of a helical microrobot inspired by the flagella used to propel bacteria. To start with, polymer helices of around 10 µm in length were prepared using a two-photon polymerisation whereby a laser is used to “write” a 3D structure is photoresist. These helices were then covered in iron or iron/titanium thin films.

It was found that by using low-strength magnetic fields it was possible to control the movement of the helices through water. Pleasingly, the helices also showed no signs of cytotoxicity according to both direct cellular imaging and an MTT assay.

Noncytotoxic artificial bacterial flagella fabricated from biocompatible ORMOCOMP and iron coating
Famin Qiu, Li Zhang, Kathrin E. Peyer, Marco Casarosa, Alfredo Franco-Obregón, Hongsoo Choi and Bradley J. Nelson
J. Mater. Chem. B, 2014, 2, 357.  DOI:10.1039/C3TB20840k

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.

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The battery is one of the biggest obstacles that is limiting many energy related breakthroughs. From allowing the capture and storage of renewable energy that will accommodate the fluctuating needs of power usage, to the use of electric cars that are able to drive further without needing to be recharged. Many solutions are being sort, some of them seeming increasingly wacky, such as the use of rhubarb to make flow batteries being carried out by Harvard researchers.

Yet it is the much more traditional low-cost lithium-ion batteries that are the most popular. These batteries are already included in a range of commercially available electric cars and small electronic gadgets. The specific energy storage capacity and the charge/discharge rate of Li-ion batteries is critical for their use and increasing this life time remains a significant challenge for their further development.

One method for the improvement is to use silicon based hollow nanostructures as high energy density anodes in these batteries. Using Si as the anode material can considerably increase the energy storage capacity of the battery; however commercialisation remains limited due to the materials accelerated mechanical failure relative to conventional anode materials. This paper by Lotfabad et al, uses atomic layer desorption of TiO2, TiN and Al2O3 on to the inner, outer or both surfaces of hollow Si nanotubes in order to overcome this mechanical failure and enhance the cycling performance of the material. Their results show that by coating with TiO2 both inside and out of the nanotube the coulombic efficiency is as high as 99.9% (among the highest ever reported for this group of materials). In reality this could mean a battery lifetime of up to 1000 cycles. The results presented in this paper are extremely promising for the future of Li-ion batteries.

Si nanotubes ALD coated with TiO2, TiN or AL2O3 as high performance lithium ion battery anodes
Elmira Memarzadeh Lotfabad, Peter Kalisvaart, Alireza Kohandehghan, Kai Cui, Martin Kupsta, Behdokht Farbod and David Mitlin,
J. Mater. Chem. A, 2014, 2, 2504-2516. c3ta14302c

H. L. Parker is a guest web writer for the Journal of Materials Chemistry blog. She currently works at the Green Chemistry Centre of Excellence, the University of York.

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Dynachromes – dynamic electrochromic polymers capable of property tuning and patterning via multiple constitutional component exchange
Daminda Navarathne and W.G. Skene

Single-crystal FeFe(CN)₆ nanoparticles: a high capacity and high rate cathode for Na-ion batteries
Xianyong Wu, Wenwen Deng, Jiangfeng Qian, Yuliang Cao, Xinping Ai and Hanxi Yang

Hot deformation induced bulk nanostructuring of unidirectionally grown p-type (Bi,Sb)₂Te₃ thermoelectric materials
Tiejun Zhu, Zhaojun Xu, Jian He, Junjie Shen, Song Zhu, Lipeng Hu, Terry M. Tritt and Xinbing Zhao

These papers are free to access until 18th March 2014 

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