Journal of Materials Chemistry Blog

Multifunctionalization of carbon nanotube fibers with the aid of graphene wrapping
The excellent mechanical and electrical properties of carbon nanotubes is harnessed in a range of applications from advanced textiles through to supercapacitors, and artificial muscles. However, the mechanical properties of the CNT fiber can be affected by chemical modification of the CNTs, and the fabrication and performance depend strongly on the morphology of the fiber surface. In this hot paper Xiaohua Zhang, Qingwen Li and co-workers report a new method to modify the surface roughness and level of functionalization of CNT fibers, by wrapping them in graphene oxide or reduced graphene. The introduction of a graphene layer also has smoothing and shield effects, resulting in higher tensile strength and improved and stabilized performance. The nanotubes can also be further functionalised with polyaniline or TiO₂ nanoparticles.
(J. Mater. Chem., 2012, 22, 16277-16282)

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Scientists in China have made an energy source for wireless nanobiodevices, such as nanorobots and cardiac pacemakers, that could be implanted under the skin.

The device comprises a photovoltaic cell that converts laser energy into electrical energy. The team optimised its performance by improving a couple of components – the nanophosphor and electrolyte. This resulted in an output power of 45µW under normal circumstances and 22 µW when covered by a 1mm thick layer of chicken skin.

Construction of 980 nm laser-driven dye-sensitized photovoltaic cell with excellent performance for powering nanobiodevices implanted under the skin
Lisha Zhang, Qiwei Tian, Wenju Xu, Xingyu Kuang, Junqing Hu, Meifang Zhu, Jianshe Liu and Zhigang Chen, J. Mater. Chem., 2012, DOI: 10.1039/C2JM33742H (Advance Article)

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The interplay of intermolecular interactions, packing motifs and electron transport properties in perylene diimide related materials: a theoretical perspective
Yun Geng,  Hai-Bin Li,  Shui-Xing Wu and Zhong-Min Su,
J. Mater. Chem., 2012, DOI: 10.1039/C2JM33369D, Advance Article   

 
Organic semiconductor heterojunctions as charge generation layers and their application in tandem organic light-emitting diodes for high power efficiency
Yonghua Chen and Dongge Ma,
J. Mater. Chem., 2012, DOI: 10.1039/C2JM32246C, Advance Article 

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CdSe-sensitized mesoscopic TiO₂ solar cells exhibiting >5% efficiency: redundancy of CdS buffer layer
Good progress has been made in improving the power conversion efficiency of semiconductor-sensitized solar cells over the last few years; however, it is unclear exactly what role the buffer layer plays in CdS/CdSe sensitized cells. In this hot paper a team from National University of Singapore and Nanyang Technological University fabricated CdSe-sensitized TiO₂ electrodes with nearly identical optical density to the best-performing CdS/CdSe electrodes. A careful comparison between CdSe and CdS/CdSe sensitized cells reveals that the CdSe-sensitized solar cells offer a better performance when light absorption is identical to that of CdS/CdSe cells, making the CdS buffer layer redundant. (J. Mater. Chem., 2012, 22, 16235-16242)

Electrochemically stimulated release of lysozyme from an alginate matrix cross-linked with iron cations
Electrochemically controlled drug release from stimuli-responsive materials offers a convenient method to control dosage for personalised medicine; however this requires the development of biologically safe, intelligent materials, to act as delivery systems. In this hot paper Evgeny Katz and co-workers at Clarkson University, USA, report an alginate matrix cross-linked with Fe³⁺ cations that releases lysozyme when an electrochemical signal is applied. The released lysozyme retains it biological activity and could be replaced in the system with protein-based drugs. The team say the switchable behaviour of the alginate hydrogel is based on the different interaction of Fe³⁺ and Fe²⁺ cations with alginate. (J. Mater. Chem., 2012, DOI: 10.1039/C2JM32008H, Advance Article)

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Fungi-based porous carbons for CO₂ adsorption and separation
Physisorption using solid adsorbents is a promising method for the separation and capture of CO₂. It uses much less energy than the conventional chemical absorption process but requires materials with very high specific surface areas. In this hot article Stefan Kaskel and co-workers from Dresden University of Technology, Germany, have prepared a set of porous carbons with very high specific surface areas (up to 2264 m² g⁻¹) by KOH activation of sustainable, environmentally friendly, fungi-based carbon sources. (J. Mater. Chem., 2012, 22, 13911-13913)

Effective solvothermal deoxidization of graphene oxide using solid sulphur as a reducing agent
Chemical reduction of graphene oxide offers a plausible route to prepare graphene-style materials on a large scale. Hydrazine has been used as one reducing agent; however, it’s highly toxic and explosive and can cause nitrogen incorporation into the carbon structure. In this hot paper Liangxu Lin and Shaowei Zhang report a simple process to prepare highly electrically conductive solid reduced graphene oxide and its dispersions using solid S as a reducing agent and NMP or DMF as a surfactant. The team say that their method allows a wide range of water soluble organic solvents and surfactants, along with a safe and moderate reducing agent, to be combined to produce high quality graphene products. (J. Mater. Chem., 2012, 22, 14385-14393)

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Controlling the dynamic behavior of heterogeneous self-oscillating gels
Belousov–Zhabotinsky gels convert chemical energy into mechanical oscillations without requiring an external stimulus. This rhythmic behaviour arises from the periodic oxidation and reduction of a ruthenium catalyst bound to the polymer. The chemical oscillations affect the hydration of the metal ion which induces the swelling and deswelling of the gel until the reagents in the host solution are consumed. In this hot paper Anna C. Balazs and co-workers combine experimental and computational studies to investigate the behaviour of heterogeneous Belousov–Zhabotinsky gels in which the Belousov–Zhabotinsky patches can differ in both size and the concentration of the ruthenium ion. The team says that this is the first reported synthesis of heterogeneous Belousov–Zhabotinsky gels.
(J. Mater. Chem., 2012, 22, 13625-13636)

Interfacial engineering of quantum dot-sensitized TiO2 fibrous electrodes for futuristic photoanodes in photovoltaic applications
Fibrous electrodes often suffer from poor adhesion, connectivity or efficiency. In an effort to solve this problem, Yong Soo Kang, Iván Mora-Seró and colleagues report a generic surface treatment approach to improve the electronic interface, and hence the photoanode performance, of quantum dot-sensitized TiO2 fiber electrodes. The team say that their interfacial engineering approach on fibrous membranes could improve the efficiency of photoanodes for range of applications including solar hydrogen generation via water splitting, hybrid (QDs–dye) excitonic solar cells, and light driven photocatalysts.
(J. Mater. Chem., 2012, 22, 14228-14235)

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A novel separation technique for aqueous nanoparticles based on a phase transfer approach 
Synthetic preparations of nanoparticles often create a mixture of sized particles; however, the properties and suitability for a specific application is often linked directly to their physical dimensions. In this hot paper Yiping Cui and colleagues report a phase transfer approach for separating different sized particles. Using an anti-charged surfactant in oil phase allowed the team to extract small nanoparticles into the oil phase while leaving larger nanoparticles behind in the aqueous phase. 
(J. Mater. Chem., 2012, 22, 13469-13472)  

The selective intercalation of organic carboxylates and sulfonates into hydroxy double salts  
Hydroxy double salts can selectively store and deliver a range of functional anions via ion exchange; however, unlike the related layered double hydroxide family they have received relatively little attention. This hot paper Gareth R. Williams and co-workers report the first systematic investigation of the selectivity of organic guest intercalation into hydroxy double salts. 
(J. Mater. Chem., 2012, 22, 13600-13611)   

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Polymeric nanowires have been made into a “paper” form, in a new method that doesn’t require harsh treatments such as etching, patterning and cleaning, unlike current methods. The “papers” are made by filtering a gel through a Buchner funnel, then peeling the “paper” off from the filter paper.

The paper contains Na⁺, but if replaced by other cations and subjected to ultraviolet light, the paper changes colour, which is easily distinguishable by the eye, and between different cations – therefore it’s an easy way of sensing different ions (calcium, mercury, lead, manganese etc). Read the article for free until 15th August.

Feng Bai, Zaicheng Sun, Ping Lu and Hongyou Fan, J. Mater. Chem., 2012, 22, 14839-14842

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Facile synthesis of well-dispersed graphene by γ-ray induced reduction of graphene oxide 
Graphene has been produced by a range of techniques including micro-mechanical exfoliation of graphite, chemical vapour deposition, epitaxial growth and the chemical reduction of graphene oxide. Chemical reduction of graphene oxide has received considerable attention as it offers a route to produce graphene on a large scale starting from cheaper natural graphite; however the reducing agents required are often poisonous or explosive. Now Chinese scientists have developed a simple approach to prepare well-dispersed graphene sheets by γ-ray induced reduction of a graphene oxide in DMF at room temperature. 
Youwei Zhang,  Hui-Ling Ma,  Qilu Zhang,  Jing Peng,  Jiuqiang Li,  Maolin Zhai and Zhong-Zhen Yu, J. Mater. Chem., 2012, 22, 13064-13069

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US researchers have made a transparent membrane that is highly electron and proton conductive.

Transparent materials with both ionic and electrical conductivity and mixed conducting properties are used in devices which require a membrane with both electrical and protonic conductivity but minimal light absorption– such as some water splitting solar cells. Blending conjugated polymers is one approach to achieve electrical and ionic conductivity; however, polymer membranes formed from blending two polymers often suffer from poor mechanical properties and polymer phase separation.

In this hot paper Paula T. Hammond and co-workers at Massachusetts Institute of Technology, USA, demonstrate that they can tune the ionic conductivity, the electrical, optical, and mechanical properties of PEDOT:sPPO by changing the composition ratio and by DMSO treatment. The polymer thin films become more transparent, smoother, softer, and exhibit higher proton conductivity as the sPPO ratio in PEDOT:sPPO is increased. After DMSO treatment, the polymer electrical conductivity dramatically increased without jeopardizing the protonic conductivity.

Highly transparent mixed electron and proton conducting polymer membranes: Junying Liu, Nicole R. Davis, David S. Liu and Paula T. Hammond, J. Mater. Chem., 2012, DOI: 10.1039/C2JM32296J (Advance Article)

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