TY - JOUR
T1 - A surface-bound molecule that undergoes optically biased Brownian rotation
AU - Hutchison, James A.
AU - Uji-i, Hiroshi
AU - Deres, Ania
AU - Vosch, Tom André Jos
AU - Rocha, Susana
AU - Müller, Sibylle
AU - Bastian, Andreas A.
AU - Enderlein, Jörg
AU - Nourouzi, Hassan
AU - Li, Chen
AU - Herrmann, Andreas
AU - Müllen, Klaus
AU - De Schryver, Frans
AU - Hofkens, Johan
PY - 2014/2
Y1 - 2014/2
N2 - 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.
AB - 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.
U2 - 10.1038/nnano.2013.285
DO - 10.1038/nnano.2013.285
M3 - Journal article
SN - 1748-3387
VL - 9
SP - 131
EP - 136
JO - Nature Nanotechnology
JF - Nature Nanotechnology
IS - 2
ER -