Although plants have efficiently captured energy from sunlight for millions of years, producing light-harvesting and energy storage devices based on photosynthesis is no easy task.
Now, a research team led by Makoto Fujita from the University of Tokyo and Tahei Tahara from the RIKEN Advanced Science Institute has found a simple way to mimic the initial stage of photosynthesis by mechanically trapping a guest molecule inside a cage structure1.
Prototypical artificial photosynthetic systems contain donor- and acceptor-type molecules. When light is absorbed by the donor, it becomes photo-excited—its electrons move to higher energy states. The acceptor group can receive and store these energetic electrons, but only if the donor and acceptor come together into what is known as an exciplex, or an excited state complex.
The difficulty is bringing together the donor and acceptor groups. An exciplex can form only if the two components are close enough and in the proper orientation during photo-excitation.
Fujita and Tahara’s team ensured exciplex formation by locking a photoactive donor molecule called bisanthracene inside a molecular cage acceptor. The self-assembled cage is highly water soluble as it contains six charged palladium atoms. The cage panels, however, are organic molecules and form a hydrophobic (water-repelling) pocket inside the cage when dissolved in water.
According to Jeremy Klosterman, the lead author of the study, the donor molecule bisanthracene is not soluble in water and, at high temperatures, is driven into the hydrophobic cage pocket. Once the solution cools, the bisanthracene is too large to exit the cage and remains trapped inside.
“Synthetically, our system is incredibly straightforward,” says Klosterman. “Simply mixing the host cage and the guest bisanthracene in water and heating causes the exciplex to self-assemble.”
Ultrafast laser spectroscopy of the host–guest complex found that the excited bisanthracene donor transferred the majority of its energy, 82%, to the exciplex state. Klosterman says the effective energy transfer is due to the extremely tight fit and strong interactions between the mechanically linked host and guest.
“This study helped us resolve an important question,” states Klosterman. Typically fluorescent molecules are non-emissive upon encapsulation by cages, but now they can infer that energy transfer into the host–guest exciplex state decreases the fluorescence lifetime.
By choosing a guest molecule that does not form an exciplex, the researchers have developed a new water-soluble fluorescent dye with a long lifetime—ideal for applications including biological sensing and imaging.
1. Klosterman, J.K., Iwamura, M., Tahara, T. & Fujita. M. Energy transfer in a mechanically trapped exciplex. Journal of the American Chemical Society 131, 9478–9479 (2009).
The corresponding authors for this highlight are based at the RIKEN Molecular Spectroscopy Laboratory and the School of Engineering, University of Tokyo
Harvesting the Sun for Power and Produce
24.11.2017 | Fraunhofer-Institut für Solare Energiesysteme ISE
Batteries with better performance and improved safety
23.11.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
High-precision measurement of the g-factor eleven times more precise than before / Results indicate a strong similarity between protons and antiprotons
The magnetic moment of an individual proton is inconceivably small, but can still be quantified. The basis for undertaking this measurement was laid over ten...
Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
24.11.2017 | Physics and Astronomy
24.11.2017 | Health and Medicine
24.11.2017 | Earth Sciences