A surface-bound molecule that undergoes optically biased Brownian rotation

James A. Hutchison, Hiroshi Uji-i, Ania Deres, Tom André Jos Vosch, Susana Rocha, Sibylle Müller, Andreas A. Bastian, Jörg Enderlein, Hassan Nourouzi, Chen Li, Andreas Herrmann, Klaus Müllen, Frans De Schryver, Johan Hofkens

48 Citationer (Scopus)

Abstract

Developing molecular systems with functions analogous to those of macroscopic machine components, such as rotors, gyroscopes and valves, is a long-standing goal of nanotechnology. However, macroscopic analogies go only so far in predicting function in nanoscale environments, where friction dominates over inertia. In some instances, ratchet mechanisms have been used to bias the ever-present random, thermally driven (Brownian) motion and drive molecular diffusion in desired directions. Here, we visualize the motions of surface-bound molecular rotors using defocused fluorescence imaging, and observe the transition from hindered to free Brownian rotation by tuning medium viscosity. We show that the otherwise random rotations can be biased by the polarization of the excitation light field, even though the associated optical torque is insufficient to overcome thermal fluctuations. The biased rotation is attributed instead to a fluctuating-friction mechanism in which photoexcitation of the rotor strongly inhibits its diffusion rate.

OriginalsprogEngelsk
TidsskriftNature Nanotechnology
Vol/bind9
Udgave nummer2
Sider (fra-til)131-136
Antal sider6
ISSN1748-3387
DOI
StatusUdgivet - feb. 2014

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