10-09 :: September 2010

nanotimes News in Brief

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A new class of organic substances discovered by scientists from the Institute of Physical Chemistry of the Polish Academy of Sciences and the Faculty of Chemistry of the University of Warsaw emits white light with continuous spectrum. This achie- vement provides experimental evidence that only single component luminophore will be necessary to construct eye-friendly light sources and displays.

“We have discovered a class of organic molecules emitting white light with continuous spectrum cove- ring almost the entire visible range,” says Dr. Jerzy Karpiuk from the IPC PAS who heads the research team. It is also important that the emission of the white light was obtained from one chemical com- pound with a very simple structure.

The research team composed of Jerzy Karpiuk (IPC PAS), Ewelina Karolak (IPC PAS) and Jacek Nowacki (Faculty of Chemistry of the University of Warsaw) observed white light emission continuously covering virtually the entire visible range. Its source is crystal violet lactone (CVL), a substance produced in mass quantities and commonly used in copy paper as the so-called dye precursor. A CVL molecule has two fluorophores embedded in its structure and respon- sible for the emission of light: one for blue and the other one for orange. The contribution of each of them to CVL’s dual fluorescence heavily depends

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on the environment of the molecule which modifies the energetics of their excited states.

“By properly adjusting the molecule’s surrounding, it is possible to control the parameters of the emis- sion spectrum, and consequently, to change the colour or shade of the white light obtained,” says Ewelina Karolak, a PhD student from the IPC PAS. http://ichf.edu.pl/press/2010/10/index101006_EN.html

The experiments conducted in the Institute of Phy- sical Chemistry of the Polish Academy of Sciences on super-thin liquid-crystal films created on water surface allowed the surprisingly slow and continu- ous rotational motion of molecules, rotating “in unison”, to be observed nearly with the naked eye.

Scientists from the Institute of Physical Chemi- stry of the Polish Academy of Sciences (IPC PAS) established that in the liquid-crystal layers that are several nanometers thick and created on water surface, molecules may rotate with extremely low speed, just one revolution per several minutes. Such slow rotational motion is a real surprise since it was expected that rotation would be quickly destroyed by thermal fluctuations. “The slowdown in rotation of molecules is nothing unexpected in liquid crystals usually formed of thousands of layers. However, in our experiments we have monolayers and we can observe the effects of very slow rotational motion of chemical mole- cules nearly with the naked eye,” emphasises Prof. Robert Hołyst from the IPC PAS.

Contact: Antoni Szafranski, Phone: +48 22 343 3262 http://www.ichf.edu.pl/