Short items, August 2011
Polymer nanobrushes ’paint’ Mona Lisa
Chinese scientists have used polymer nanobrushes to ’paint’ a 3D representation of Leonardo da Vinci’s masterpiece, the Mona Lisa.
Surface patterning with polymer nanoarrays is important in many areas of science, including the design of electronics and medical devices. But in order to fabricate these intricate devices 3D polymer structures, which are difficult to make, are necessary.
Now, Zijian Zheng and colleagues at the Hong Kong Polytechnic University have developed a simple way to produce 3D polymer structures and demonstrated it by creating an image of the Mona Lisa.
To make the image, the team created a template by converting a greyscale image of the picture into a bitmap image. Where a white pixel appeared on the image, a nanobrush building block was attached to the substrate. The black pixel areas were left vacant to serve as spaces. Nanobrushes separated by small spaces polymerised to form denser 3D architectures. But where larger spaces existed the polymer chains did not polymerise further.
The research is published in Angewandte Chemie, International Edition (DOI: 10.1002/anie.201102518).
UK higher education white paper
In June, the UK governments’ department for business innovation and skills (BIS) published its white paper on higher education. The reforms include the previously reported changes to student finance (see Chemistry World, December 2010, p7) as well as reforms that are intended to improve students’ experience.
The government intends to publish an increased level of information to prospective students, including graduate employment and earnings outcomes for individual courses and institutions. They are also asking universities to publish the qualifications of previously sucessful applicants to assist teenagers who are choosing their A-levels.
The recruitment of the 65,000 students achieving A, A, B or above at A-level will be relaxed so that any university can take them regardless of student numbers. This is in contrast to the present system where universities are fined if they recruit more students than their quota.
European patent moves closer
A single European patent looks closer than ever now ministers have agreed on the details, at the Competitiveness Council in Luxembourg. The agreement is seen as a significant step for the Hungarian Presidency and the European Commission.
After a halt in proceedings (see Chemistry World, April 2011, p6), ministers have agreed on the number of translations that applicants will need to file, as well as technical details of the patent itself.
Agreement of these two regulations will reduce the cost of translating patents by up to 80 per cent in Europe. This will allow companies and individuals to protect their inventions with a single patent that is valid in 25 European countries.
Making smell-o-vision a reality
A polymeric matrix of cells, which can be opened and closed individually, could bring personal ’smell-o-vision’ a step closer to reality.
Virtual reality experiences are becoming more realistic and smell-o-vision can enhance these. However, current attempts can fail to impress due to a narrow range of smells that can only be deployed once.
Writing in Angewante Chemie, International Edition (DOI: 10.1002/anie.201102759) researchers at the University of California, San Diego, US, and Samsung in Korea, explain how they’ve used the polymer polydimethylsiloxane to create a square matrix of cells, each of which holds a different fragrance. The scientists use heat to release an odour on cue.
The system can be used with cells ranging in size from nanometres through to micrometres, and shows no signs of leakage.
Metallic pick ’n’ mix
Scientists in Germany have plucked a metal ion from the middle of a phthalocyanine molecule on a silver surface using the tip of a scanning tunnelling microscope (STM).
The chemical and electronic properties of phthalocyanines - molecular rings of 16 alternating carbon and nitrogen atoms - can be tuned by changing the metal ion at their centre. But swapping these in a simple, controlled way is difficult.
Using the new technique, the team from University of Kiel successfully removed lead ions from the centre of phthalocyanine molecules. By approaching the lead with the STM tip, a strong bond between the tip apex atom and the lead can be formed.
When the tip is retracted, the bond between the lead and the phthalocyanine breaks and demetalation occurs.
The research is published in the Journal of the American Chemical Society (DOI: 10.1021/ja203199q).
Germany votes no to nuclear
The German parliament has voted to phase out the country’s nuclear power plants by 2022 and shift to using renewable power sources instead.
The phase out has in essence already begun. In March, after the Fukushima disaster, German chancellor Angela Merkel announced that seven nuclear power plants would be shut down for safety review until at least June (see Chemistry World, April 2011, p11). These will not be restarted. The other nine reactors still running will be switched off on fixed dates between now and 2022.
In addition, the government will invest in renewable energy, including new grids and feed-in tariffs. This will ensure that Germany will stick to its pledge to reduce CO2 production by 40 per cent from 1990 to 2020.
Chatty nanoparticles attack tumour
Researchers in the US have shown how drugs can be directed to a tumour using two different nanoparticles that talk to each other: one nanoparticle homes in on the tumour then loudly broadcasts its location to a second, drug-carrying particle. In studies with mice, the system can result in 40 times more drug reaching the target than when non-communicating controls are used.
Conventional approaches involve swamping tissues with excessive amounts of drug so that the tumour gets a therapeutic dose. In research published in Nature Materials (DOI: 10.1038/nmat3049), Sangeeta Bhatia of the Massachusetts Institute of Technology and colleagues used the blood’s coagulation response to signal a drug carrier so that it accumulates where needed.
The team devised one nanoparticle system to enter the tumour and cause damage to the blood vessels, resulting in production of fibrin, which acts as the ’transmitting’ signal. A second nanoparticle circulating in the blood seeks out the fibrin, as a ’receiver’ of the signal.
Breaking C-F bonds
US chemists have discovered a new way to break the bond between carbon and fluorine - the strongest carbon bond there is.
Bonds between fluorine and sp2 hybridised carbon atoms can be made and broken using oxidative addition. But this approach has failed with bonds between fluorine and alkyl carbon atoms. In Science (DOI:10.1126/science.1200514) researchers at Rutgers University in New Jersey used a catalyst based on iridium clamped between two bulky dialkylphosphino groups - a so-called pincer-ligated complex - to break the bond.
The reaction proceeds in an unexpected way - the metal centre inserts itself into a C-H bond before the fluorine migrates to the metal, with the displaced hydrogen returning to the carbon. This suggests possible routes for the development of new catalysts to promote reactions that make or break C-F bonds.
3D Tetris photosystems
Scientists have used self-organising surface-initiated polymerisation (SOSIP) to develop 3D supramolecular structures mounted on oxide surfaces to make photosystems that generate electrical current from light energy.
In order to efficiently convert light into energy, photosystems need two channels of molecules adjacent to each other within the structure. One channel carries electrons in one direction and the other carries the positive charge or ’hole transport’ in the opposite direction.
A research team at the University of Geneva, in Switzerland, has incorporated this double channel concept into supramolecular architectures, using SOSIP. Different component parts can be built into the structure in a uniform manner by remote control. The process can be thought of as ’3D Tetris’ on the molecular level.
The research is published in the Journal of the American Chemical Society (DOI: 10.1021/ja204020p).
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