Colloidal quantum dots are showcasing their potential beyond vibrant colors, diving deep into quantum effects such as spin coherence.
Researchers are pioneering the use of these quantum properties to influence photochemical processes, an innovative cross-disciplinary effort with implications for quantum biology.
Advancements in Quantum Dot Applications
Colloidal quantum dots (QDs) offer a versatile platform for exploring various quantum effects. Their unique size-dependent colors provide a vivid, visible demonstration of the quantum confinement effect under ambient conditions.
In recent years, QDs have revealed even more exotic quantum behaviors, including single-photon emission, spin coherence, and exciton coherence. Unlike other solid-state quantum platforms, QDs can be handled in solution just like molecules. This property enables the functionalization of their surfaces with organic molecules, making them powerful tools for driving photochemical processes.
Exploring Quantum Coherence in Photochemical Reactions
The ability of colloidal QDs to maintain strong room-temperature spin quantum coherence while also participating in photochemistry inspired Prof. Kaifeng Wu and his team at the Dalian Institute of Chemical Physics, part of the Chinese Academy of Sciences, to pioneer a new interdisciplinary field: leveraging the quantum coherence of QDs to control photochemical reactions.
This idea is in close relation to a fascinating example of quantum biology, in which migratory animals are believed to use the Earth’s magnetic field to coherently modulate the spin-triplet recombination yields of photogenerated radical pairs and subsequently trigger a sensory signaling cascade for navigation.
Breakthrough in Quantum Controlled Photochemistry
In a study published on January 6 in Nature Materials, Prof. Wu’s team reported the hybrid radical pairs prepared from colloidal QDs and their surface-anchored molecules, and demonstrated the unique “quantum advantage” of hybrid radical pairs in quantum coherent control of triplet photochemistry.
Unlike pure organic radical pairs featuring a pair of electrons with similar Landé g-factors and thus a small Δg (0.001-0.01), the large Δg (0.1-1) of the hybrid radical pairs, along with the strong exchange coupling enabled by quantum confinement of QDs, allowed for direct observation of the radical-pair spin quantum beats that are usually hidden in previous studies.
Leveraging such rapid quantum beating, researchers demonstrated a strong magnetic field control over the triplet recombination dynamics, with the modulation level of the triplet yield reaching 400% at 1.9 T. Moreover, the magnetic field effect was facilely tunable through QD size and composition, which is an unmatched advantage over previous pure organic radical pairs.
Future Prospects of Quantum Dots in Technology
“The QD-molecule hybrid radical pairs and their strong, tunable magnetic field effect reported in this study will strongly benefit the spin-control over molecular and hybrid inorganic/organic optoelectronics through borrowing the fundamental principles of semiconductor spin physics,” said Prof. Wu.
“Hybrid radical pairs may constitute a unique material platform to merge the field of emerging molecular quantum sciences with solid-state quantum platforms to enable many novel quantum information technologies,” he added.
Reference: “Coherent manipulation of photochemical spin-triplet formation in quantum dot–molecule hybrids” by Meng Liu, Jingyi Zhu, Guohui Zhao, Yuxuan Li, Yupeng Yang, Kaimin Gao and Kaifeng Wu, 6 January 2025, Nature Materials.
DOI: 10.1038/s41563-024-02061-1
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