The single-molecule imaging of inherently ?uorescent nanocars on three substrates, (plasma cleaned, reactive ion etched, and amine-functionalized glass) and nanocars equipped with either p-carborane-wheeled or adamantane wheels are reported. The nanocars were imaged using 4,4-di?uoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) as the chromophore, which was rigidly incorporated into the nanocar chassis via Sonogashira cross-coupling chemistry that permitted the synthesis of nanocars having di?erent geometries. Using single-molecule fluorescence imaging, the percentage of moving nanocars and their diffusion constants were determined for each substrate. We found that the nanocar mobility decreased with increasing surface roughness and increasing surface interaction strength.  The mobility of four- and three-wheeled nanocars with adamantane wheels was also compared. It was found that, for the four-wheeled nanocar, the percentage of moving nanocars and the di?usion constant show a signi?cant improvement over p-carborane-wheeled nanocars with the same chassis. The three-wheeled nanocar showed only limited mobility due to its geometry. These results are consistent with a wheel-like rolling motion. We furthermore developed a model that relates the percentage of moving nanocars in single-molecule experiments with the di?usion constant. The excellent agreement between the model and the single-molecule studies yields a detailed understanding of motion in these molecular machines.

Modulating the mobility of surface-rolling molecules via substrate and wheels

247th National Meeting (2014)

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