Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Detecting an unexpected delay at ultrafast speed

08.08.2011
High-speed laser measurements reveal new insights into rearrangements of light-driven chemical structures with implications for solar-energy conversion and opto-electric devices

Molecules that suddenly transform into new structures when stimulated by photons or electrons play key roles in many chemical and biological processes. Recently, chemists have discovered that adding transition metals such as copper to photo-responsive organic ligands produces materials with high solar conversion efficiencies, owing to the metal’s ready supply of light-activated electrons. But despite the interest in these substances for opto-electronic devices, their inner workings remain mostly inscrutable because the charge-transfer dynamics happen too quickly for detection by typical instruments.

Tahei Tahara and colleagues from the RIKEN Advanced Science Institute, Wako, have spearheaded development of ultrafast laser spectroscopy that can capture these high-speed reactions by taking ‘snapshots’ of photochemical transformations with quadrillionths-of-a-second (10-15 s) accuracy. Now, an unprecedented finding by the research team—a picosecond (10-12 s) time delay during a theoretically instantaneous distortion—is set to overturn current thinking about light-driven rearrangements in transition metal complexes.

Copper dimethylphenanthroline is a compound containing two propeller-shaped wings, made out of thin aromatic sheets. Chemists regularly use it to explore photo-induced structural changes. In its unexcited state, the complex’s wings are oriented perpendicular to each other. But when illuminated at a specific wavelength, the copper ion absorbs a photon and transfers an electron to the sheets—an action that flattens the structure by disrupting critical copper—phenanthroline bonds.

The exact flattening mechanism, however, has been controversial because copper electrons can be photo-excited in two different ways: through an easily accessible high-energy state called S2, or a harder-to-spot, low-energy transition called the S1 state. Tahara and colleagues tracked the extremely fast relaxation process from both states and found that S1 electrons provoked the flattening. This finding will allow researchers to eventually squeeze as much efficiency as possible from these devices.

When the team examined how the molecule behaved in the S1 excited state, they saw unexpected oscillations in the absorption signals during its picosecond-long lifetime. According to Tahara, these signals are unmistakable evidence that the excited complex vibrates coherently in place and waits a short while before distorting.

Because this result contradicts traditional understandings of transition metal processes—atomic movements were theorized to immediately follow excitation to S1-type electronic states—it may spark revolutionary changes in how chemists conceive and control photo-initiated reactions. “This is a fundamental and deep issue,” says Tahara.

By expanding this technique to other poorly understood metal complexes, the team hopes to produce ‘textbook-type’ results that can guide future development of these remarkable materials.

The corresponding author for this highlight is based at the Molecular Spectroscopy Laboratory, RIKEN Advanced Science Institute

Reference:
Iwamura, M., Watanabe, H., Ishii, K., Takeuchi, S. & Tahara, T. Coherent nuclear dynamics in ultrafast photoinduced structural change of bis(diimine)copper(I) complex. Journal of the American Chemical Society 133, 7728–7736 (2011).

gro-pr | Research asia research news
Further information:
http://www.riken.jp
http://www.researchsea.com

More articles from Process Engineering:

nachricht Dresdner scientists print tomorrow’s world
08.02.2017 | Fraunhofer-Institut für Werkstoff- und Strahltechnik IWS

nachricht New technology for mass-production of complex molded composite components
23.01.2017 | Evonik Industries AG

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

When Air is in Short Supply - Shedding light on plant stress reactions when oxygen runs short

23.03.2017 | Life Sciences

Researchers use light to remotely control curvature of plastics

23.03.2017 | Power and Electrical Engineering

Sea ice extent sinks to record lows at both poles

23.03.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>