Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Nanocapsules for artificial photosynthesis

06.11.2009
Imitating photosynthesis in plants? If we were to accomplish this, mankind would have a little less to worry about. Chemists from the University of Würzburg have now made progress on the road to achieving artificial photosynthesis.

The structure that has been developed in the university's Organic Chemistry laboratory is fascinatingly complex: thousands of similar molecules are packed together to create a capsule that is filled with molecules of a different kind. The diameter of one capsule is a mere 20 to 50 nanometers, which is one ten-thousandth of a pinhead.


Nanocapsule, made in Würzburg: Thousands of similar molecules are packed together to create a capsule that is filled with molecules of a different kind. Figure: Institute of Organic Chemistry, University of Würzburg

Structures that are so elaborate are far from the ordinary in chemistry. So, it is hardly surprising that these Würzburg nanocapsules appear on the front page of the November issue of the journal "Nature Chemistry". What is more, they can also do something that has not been described before for chemically synthesized molecules.

Encapsulated molecules transmit energy

Nanocapsules possess a property that is important in photosynthesis in plants: the molecules inside the capsule absorb light energy and emit some of this again in the form of fluorescent light. The rest of it, however, is transmitted by energy transfer to the capsule molecules, which then also cast fluorescent light.

As far as photosynthesis is concerned nothing different happens, to put it simply: molecules harness energy from sunlight and transmit it to other molecules in a complex process, at the end of which the energy is bound chemically. The sun's power then sits in valuable carbohydrates that plants, animals, and people use to generate the energy they need to live.

In principle, therefore, the nanocapsules should make suitable components for an artificial photosynthesis contraption. "They would even use the light far more efficiently than plants because their synthetic bilayer membranes would be composed entirely of photoactive material," says Professor Frank Würthner.

The value of artificial photosynthesis

Why conduct research into artificial photosynthesis? In photosynthesis, plants consume the "climate killer" that is carbon dioxide. In view of global warming, many scientists see artificial photosynthesis as a possible way of reducing the volume of the greenhouse gas carbon dioxide in the atmosphere. In addition, this process would also create valuable raw materials: sugar, starch, and the gas methane.

Unique material for the capsule shell

The Würzburg nanocapsules are comprised of a unique material. This was developed in Frank Würthner's working group on the basis of so-called amphiphilic perylene bisimides. If the base material, which can be isolated as a powder, is placed in water, its molecules automatically form so-called vesicles, though these are not stable at that point. It is only through photopolymerization with light that they become robust nanocapsules that are stable in an aqueous solution - regardless of its pH value.

Bispyrenes as the filling inside the capsules

It was the visiting scientist from China, Dr. Xin Zhang, who managed to fill the nanocapsules with other photoactive molecules. A fellow of the Humboldt Foundation, he is currently a member of Professor Würthner's working group.

Zhang smuggled bispyrene molecules into the nanocapsules. The special thing about these molecules is that they change their shape to suit their environment. Where the pH value is low, in other words in an acidic environment, they assume an elongated form. If they are then excited with UV light, they emit blue fluorescent light.

If the pH value rises, the molecules fold. In this shape they emit green fluorescent light. In this state the bispyrenes excite the capsule shell energetically, which reacts to this with red fluorescence.

Blue, green, and red. If the three primary colors overlap, this produces white - as with a color television. It is the same with the nanocapsules: with a pH value of 9, in other words just right of neutral, they emit white fluorescent light - "a so far unique effect in the field of chemical sensing, which might be groundbreaking for the design of fluorescence probes for life sciences," explains Professor Würthner.

Nanoprobe for pH measurements

The Würzburg chemists have access to an extremely sensitive nanoprobe: the pH value of an aqueous solution can be determined with nanoscale spatial resolution over the wavelength of the fluorescent light emitted by the nanocapsules.

This means that nanocapsules are not just an option for artificial photosynthesis, they can also be used for diagnostic applications. For example, they could be equipped with special surface structures that purposefully dock to tumor cells and then make these visible by means of fluorescence.

Both possible applications are the subject of further research by Frank Würthner and his team. The work described here was funded by the German Research Foundation (DFG).

Contact

Prof. Dr. Frank Würthner, T (0931) 31-85340, wuerthner@chemie.uni-wuerzburg.de

"Vesicular perylene dye nanocapsules as supramolecular fluorescent pH sensor systems", Xin Zhang, Stefanie Rehm, Marina M. Safont-Sempere & Frank Würthner, Nature Chemistry 1, 623 - 629 (2009), doi:10.1038/nchem.368

Robert Emmerich | idw
Further information:
http://www.uni-wuerzburg.de/fuer/studierende/

More articles from Life Sciences:

nachricht Individual Receptors Caught at Work
19.10.2017 | Julius-Maximilians-Universität Würzburg

nachricht Rapid environmental change makes species more vulnerable to extinction
19.10.2017 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Electrode materials from the microwave oven

19.10.2017 | Materials Sciences

New material for digital memories of the future

19.10.2017 | Materials Sciences

Physics boosts artificial intelligence methods

19.10.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>