Optimising Photoexcited Spin Interactions in Charge Transfer and Chromophore Radical Systems in the Pursuit of Quantum Sensors

Organic molecules are emerging as promising candidates for photoactivated quantum sensing devices such as masers and spin-ensemble detectors. In such systems, sensing relies on monitoring the spin coherence of paramagnetic states or the stimulated collapse of a spin-polarised state. However, due to inefficient spin dynamics, the molecular materials underpinning these technologies exhibit limited sensitivity and require strong light sources and supporting cavities with unrealistically high-quality factors. For these families of molecular quantum sensors to be widely applied we must develop new materials with enhanced spin dynamics that simplify their operation and improve sensitivity.<br/>To tackle these issues, we have designed novel approaches to tune the quantum properties of candidate molecular systems and^[2,3] synthesized several new triplet and radical-based materials capable of producing strong and long-lived electron spin polarisation. Using transient optical spectroscopy and pulsed electron spin resonance spectroscopy it has been possible to link the electronic behaviour with their spin dynamics and, ultimately, determine their merit as quantum sensors. These results pave the way for the development of more widely applicable molecular quantum technologies.<br/><br/><b>References:</b><br/>[1] D. M. Arroo, N. M. Alford, J. D. Breeze, <i>Appl. Phys. Lett.</i> <b>2021</b>, <i>119</i>, 140502.<br/>[2] W. Ng, X. Xu, M. Attwood, H. Wu, Z. Meng, X. Chen, M. Oxborrow, <i>Adv. Mater.</i> <b>2023</b>, <i>35</i>, 2300441.<br/>[3] M. Attwood, X. Xu, M. Newns, Z. Meng, R. A. Ingle, H. Wu, X. Chen, W. Xu, W. Ng, T. T. Abiola, V. G. Stavros, M. Oxborrow, <i>Chem. Mater.</i> <b>2023</b>, <i>35</i>, 4498–4509.