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
In best circles: First integrated circuit from self-assembled polymer
19.02.2018 | Max-Planck-Institut für Polymerforschung
System draws power from daily temperature swings
16.02.2018 | Massachusetts Institute of Technology
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
19.02.2018 | Information Technology
19.02.2018 | Ecology, The Environment and Conservation
19.02.2018 | Life Sciences