Near-infrared light-activated Z-to-E isomerization of azobenzene via triplet sensitization from PbS quantum dots.

Azobenzene (Azo) photoswitches have attracted significant attention for developing smart photoresponsive materials owing to their reversible light-induced isomerization between E and Z configurations. However, it is challenging to design an Azo capable of quantitative and efficient Z → E photoisomerization under low-energy photon irradiation, particularly near-infrared (NIR) light above 800 nm. Here, we demonstrate that Z → E photoswitching of Azo can be achieved under 808 nm light irradiation when PbS quantum dots (QDs) are combined with carboxylated Azo (Azo1). The unique spin-orbit coupling of PbS QDs facilitates efficient triplet energy transfer to Z-Azo1 under NIR light irradiation, thereby facilitating Z → E photoswitching via the excited triplet surface. Importantly, the broad absorption spectrum of PbS QDs enables activation of Z → E photoisomerization using any desired wavelength across the visible and NIR spectra up to 900 nm. The photoswitching of Azo1 when combined with PbS QDs exhibits reversible photoisomerization and good fatigue resistance over alternating irradiation cycles of 365 nm and 808 nm light. Our strategy of combining Azo and QDs holds promise for advancing the development of high-performance NIR light-activated optoelectronic materials and devices.