Highly Efficient Near-Infrared Light-Driven Molecular Motor Rotation Enabled by Upconversion Nanoparticles as Nanoscale Light Sources.

Powering light-driven molecular motors with visible or near-infrared (NIR) light is essential in the design of molecular machines, bringing dynamic functions to the next generation of responsive materials particularly for biological applications. However, current strategies suffer from heavy molecular substitution and low photoefficiency of excitation, limiting their practical use in bulk materials and biomolecular systems. Here, we report a general and highly efficient strategy to power NIR light-driven molecular motors via a radiative energy transfer mechanism. Taking advantage of spectrally tunable upconversion nanoparticles (UCNPs), the motors powered by continuous wave NIR light can reach photostationary states (PSS) with high efficiency, comparable to those of direct UV/visible light-driven systems, without a deaeration process needed. The concept is validated on various molecular motors with different rotary speeds, providing a general, broadly applicable principle for the future design of highly efficient NIR-powered photodynamic molecular motor systems.