An image of the diffraction pattern of phthalocyanine molecules after their coherent propagation through the frustule of Amphipleura pellucida. Courtesy: Michele Sclafani et al.

An image of the diffraction pattern of phthalocyanine molecules after their coherent propagation through the frustule of Amphipleura pellucida.
Courtesy: Michele Sclafani et al.

Physics World reports that the exoskeleton of a diatom has been used as a diffraction grating by researchers in Vienna, who have carried out a molecular interferometry experiment using it. The team showed that a coherent molecular beam could be diffracted from the silicon-based cell walls of the marine alga. Algae are cheap and easily available, so replacing costly nanodevices with them in interferometry experiments would be beneficial, according to the researchers.

Contrary to classical mechanics, quantum physics states that a particle can act like a wave and vice versa – an idea that was first proposed by Nobel-prize-winning physicist Louis de Broglie back in 1923. While the idea that tiny particles such as electrons could behave like a wave came as a shock, scientists now know that even objects a million times more massive than electrons, such as complex molecules, also show quantum interference. Massive molecules have very small wavelengths and therefore a grating with extremely thin and closely spaced slits is needed to observe their diffraction. Currently, such sophisticated devices are specially fabricated using nanotechnology techniques.

Now physicists Michele Sclafani, Markus Arndt and colleagues from the University of Vienna have shown that a simple, inexpensive and natural grating is close at hand in the form of diatoms – mostly unicellular marine algae that are encased within a cell wall made of silica that is known as a frustule. In the experiment, Sclafani used Amphipleura pellucida – an alga that can be found on the beach. It has a wall thickness of 90 nm and a surprisingly regular pore distance of about 200 nm. The researchers found that they could use the diatom to measure molecular De Broglie wavelengths as small as a few billionths of a millimeter by firing beams of molecules at it.

Read More