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Archive for the ‘Materials’ Category

Bendy non-volatile flash memory data storage device

11 Jul 2012

Scientists in Taiwan have made a flexible memory device, which they say could open up a new design approach for high performance flexible non-volatile resistive memory devices. Non-volatile devices are computer memory devices that can retain stored information even when not powered, for example read-only memory, flash memory, hard drives and floppy disks.

The team’s device consists of a single-layer donor-acceptor conjugated polymer fabricated on plastic polyethylene naphthalene. It displayed a low threshold voltage (±2V), low switching power (~100µW cm^-2), large on/off memory window (10⁴), good retention (>10⁴s) and excellent endurance against electrical and mechanical stimuli, they say.

Link to journal article
Poly(fluorene-thiophene) Donor Tethered Phenanthro[9,10-d]imidazole Acceptor for Flexible Nonvolatile Flash Resistive Memory Devices
H-C Wu et al
Chem. Commun., 2012, DOI: 10.1039/c2cc34257j

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A new type of conducting polymer

05 Jul 2012

Scientists in the US have reported a new type of conducting polymer, generated by a ROMP (ring opening metathesis polymerisation) reaction. The new polymers could have potentially useful properties, they say.

They reacted the complex (η⁵-C₅H₅)Ir(η⁴-C₆H₆) with Grubbs’ catalyst to give a polyacetylene consisting of cyclopentadienyliridium bound s-cis butadiene moieties separated by C=C linkages, a previously unavailable polyacetylene type.

Link to journal article
Ring Opening Metathesis Polymerization of an η⁴-Benzene Complex: A Direct Synthesis of a Polyacetylene with a Regular Pattern of Π Bound Metal Fragments
P D Zeits, T Fiedler and J A Gladysz
Chem. Commun., 2012, DOI: 10.1039/c2cc32150e

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Film to aid drug metabolism study

05 Jul 2012

A way to study drug metabolism using cytochrome P450 enzymes (which are involved in the metabolism of over 60% of clinically used drugs) has been developed by scientists in China.

The team made a film of indium tin oxide nanoparticles (they have good conductivity) and cytochrome P450s encapsulated by chitosan (which are biocompatible) on a carbon electrode. They were able to bioelectronically initiate cytochrome P450 catalysis by replacing electron donation from expensive nicotinamide adenine dinucleotide phosphate with electrodes.

The system has potential for applications in drug discovery and development by monitoring substrate metabolism and enzyme inhibition. Other applications include biosensors for toxicity analysis and bioreactors for chemical synthesis.

Link to journal article
Electrochemically Driven Drug Metabolism via Cytochrome P450 2C9 Isozyme Microsomes with Cytochrome P450 Reductase and Indium Tin Oxide Nanoparticle Composites
X Xu et al
Chem. Commun., 2012, DOI: 10.1039/c2cc33575a

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Mirrors to improve dye sensitised solar cell performance

11 Jun 2012

Mirror-like nanoparticles can boost the efficiency of solar cells. Scientists in Australia coated a solar cell’s TiO₂ photoanode with cubic cerium oxide nanoparticles. The nanoparticles’ large mirror-like facets are good at scattering light back onto the TiO₂ nanoparticles, resulting in a 17.8% improvement in the power conversion efficiency compared to regular dye sensitised solar cells.

Link to journal article
Cubic CeO₂ Nanoparticles as Mirror-like Scattering Layer for Efficient Light Harvesting in Dye-Sensitized Solar Cells
Lianzhou Wang
Chem. Commun., 2012, DOI: 10.1039/c2cc32239k

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Easy synthesis of nanocups and nanopatches

29 May 2012

Graphical abstract: Facile synthesis of functional Au nanopatches and nanocups A gold nanocup – it sounds like something a posh fairy might drink out of. But actually, metal nanocups are promising particles for sensing and nanoelectronics thanks to their plasmon coupling and light scattering properties. Until now, they have been difficult to make but Jinlong Gong at Tianjin University, China, Zhihong Nie, at the University of Maryland, USA, and colleagues have developed a new easy route suitable for large scale synthesis.

The team used a template-free, liquid-liquid interfacial reaction to build up the gold cups round polymer particles. These so called ‘patchy particles’ are themselves attractive as building blocks for nanostructures due to the directional interactions between the metal patches. Removing the polymers using organic solvent revealed the nanocups with diameters as small as 76 nm. The team demonstrated that the cups can enhance surface enhanced Raman scattering intensity up to the order of 10⁸.

Find out more – download Gong’s ChemComm communication

Want to learn more about surface enhanced Raman spectroscopy? Check out the ChemComm web theme >

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Nanoscopic electrochemical cells probe forests

16 May 2012

3D carbon nanotube forests are of particular interest in the electrochemical arenas of sensing and energy applications. Some researchers have suggested that it is necessary to use open-ended carbon nanotubes and carry out a pre-treatment or activation step to support fast electrochemistry, but is this always the case?

Patrick Unwin and co-workers set out to investigate. They prepared carbon nanotube forests using a chemical vapour deposition growth method. To probe the local electrochemical response of the forests, they used a nanoscopic double barrelled pipette tip, filled with supporting electrolyte and redox species. This allowed the team to interrogate the sidewalls and closed ends of the nanotubes that made up the forest with high spatial resolution.

Both sidewalls and the closed tube ends were capable of fast electron transfer proving that single walled carbon nanotubes do not require open ends for fast electrochemistry with outer sphere redox couples. This overturns the current consensus, based on averaged macro-sized measurements, that open ends dominate nanotube forest electrochemistry.

Without the requirement for pre-treatment or activation, electrochemical nanotube forest applications will be easier to achieve.

To find out more, download the ChemComm article today.

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Ambient pressure XPS on the cheap

21 Mar 2012

X-ray photoelectron spectroscopy (XPS) is capable of characterising the surface composition, oxidation state and electron state of materials. Unfortunately, it uses electrons and so common XPS machines must work at vacuum pressures. But how could you use XPS under ambient pressure?

One option would be to use public synchrotron facilities but access is through proposal review and available time is restricted so it is not feasible for day-to-day studies. Another option would be to follow the lead of Franklin Tao and build an inexpensive, ambient pressure XPS machine in-house.

Such a machine is ideal for catalytic studies. Previously scientists investigated catalysts with conventional vacuum XPS before and after experiments. Tao’s machine enables him to investigate catalyst surface changes during reaction conditions, something that required synchrotron facilities until now. The machine’s novel reaction cell allows XPS measurements to be carried out at up to 25-50 Torr using an inexpensive bench top X-ray source.

: external view of the reaction cell

In addition to the ambient pressure XPS functionality, an on-line mass spectrometer allows correlation between catalytic performance and surface chemistry. Tao has demonstrated this novel machine by investigating the oxidation and reduction of ceria under real reaction conditions.

With day-to-day ambient pressure XPS now within reach of every research group, catalytic studies under reaction conditions have received a significant boost.

To find out more, download the ChemComm article today.

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Stopping bugs in their tracks

20 Mar 2012

To prevent the spread of bugs, scientists in Switzerland have starved microbes of phosphate by using lanthanum oxide nanoparticles. The nanoparticles compete against the microbes for available phosphate and so the microbes can’t grow. The team says that the strategy is of particular technical interest as it can bypass toxic material release and provides an antimicrobial solution with small environmental footprint.

Link to journal article
Phosphate starvation as an antimicrobial strategy: the controllable toxicity of lanthanum oxide nanoparticles
L C Gerber et al
Chem. Commun., 2012, DOI: 10.1039/c2cc30903c

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Micro power for micro devices

08 Mar 2012

An easy way to make high-performance micro-supercapacitors based on nanocrystal building blocks has been developed by scientists in the US and China. Micro-power sources have become a key component for micro-electronics but they are expensive and difficult to make. To demonstrate their concept, the team made nanoporous thin-film pseudocapacitor electrodes that showed ultrafast lithium storage kinetics, high capacitance and excellent cycling stability, giving them great promise for high energy and high power micro-device applications.

Link to journal article
Ready Fabrication of Thin-Film Electrodes from Building Nanocrystals for Micro-Supercapacitors
Z Chen et al
Chem. Commun., 2012, DOI: 10.1039/c2cc30406f

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Hydrogen storage material reaches 12wt% release of pure hydrogen at moderate temperature

08 Mar 2012

Ammine aluminium borohydrides are promising materials for hydrogen storage but they have low hydrogen capacities and sluggish kinetics under moderate temperatures.

Now, by changing the coordination number of ammonia and adopting mixed cations, scientists in China have found an ammine aluminium borohydride that releases over 12wt% of pure hydrogen at 120^oC. This is well above the minimum abundance of hydrogen required for on-board applications, they say.

Link to journal article
Ammine aluminum borohydrides: an appealing system releasing over 12 wt.% pure H2 under moderate temperature
Y Guo et al
Chem Commun., 2012, DOI: 10.1039/c2cc30751k

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