How Can We Get to Know a Single Photon, Atom or Molecule?

 

Particles or molecules, like people, appear differently when seen as individuals rather than as part of a group. Identical protein molecules, for instance, can have idiosyncratic pathways of folding. Only by looking at them one at a time can one begin to tease out the most basic behavior of these molecules. Ensemble studies may yield averages – speed of motion, for example – that hide significant facts; some molecules may actually have two different means of locomotion, neither of them at the average speed.

Single molecules can also perform functions that larger bits of matter can’t. For example, signals emitted by individual molecules can help map nanoparticle surfaces and report on their interactions with light, opening up new possibilities for applications in nanotechnology. And the role of solitary molecules in electronics is likely to grow as the size of components continues to shrink. To understand how these will function in future devices, scientists are studying how electrons move through molecules and how changes in a molecule’s structure can alter the way it conducts electricity.

In the Faculty of Chemistry, Prof. Gilad Haran uses a wide variety of optical techniques to uncover the dynamics of different molecules, both biological and non-biological. With an optical microscope fitted with lasers and detectors capable of recording single photons, as well as fast cameras, he can observe a molecule’s progress down to the nanosecond and nanometer. Dr. Oren Tal captures single molecules in a tiny break in a sort of spring-loaded wire. By precisely manipulating the distance between the edges of the break, Tal is able to stretch and tilt molecules, changing their conductivity. The basic principles he is uncovering may one day help in designing a new generation of electronic devices.