Powering Molecular Motors with Light Across the Rainbow Using Quantum Dots.

Overcrowded alkene-based molecular motors have high potential in building artificial molecular machines, precise drug delivery, and smart responsive materials due to their unidirectional rotation at the molecular scale under UV light. Powering molecular motors with visible light, especially in the low-energy green, yellow, and red regions, has been a significant challenge, limiting their further application. Herein, we report a general and versatile strategy to overcome this challenge and drive molecular motors using low-energy, low-intensity, noncoherent light across the visible spectrum. Our approach is achieved by simply mixing molecular motors with semiconductor colloidal quantum dots (QDs) and a triplet mediator (9-anthracenecarboxylic acid). The size-tunable absorption of QDs can precisely match the desired color for activating the motor. The mechanism of our design relies on the unique property of QDs, which can efficiently sensitize molecular triplets. Through two-step triplet energy transfers, the rotation of the motor can be efficiently activated using low-energy photons. For the first time, we accomplished driving molecular motors at wavelengths beyond 530 nm under low-intensity and noncoherent light. This breakthrough not only expands the capabilities of visible-light-activated molecular systems to operate in a broad wavelength range but also opens numerous opportunities toward controlling dynamic functions while circumventing competing photochemical processes (i.e., photodegradation).