Journal of Sol-Gel Science and Technology https://doi.org/10.1007/s10971-019-05213-x ORIGINAL PAPER: SOL – GEL AND HYBRID MATERIALS FOR BIOLOGICAL AND HEALTH (MEDICAL) APPLICATIONS Niobium oxide doped with Tm 3+ and Gd 3+ ions for multimodal imaging in biology Eduardo J. Nassar 1 ● Susane B. Moscardini 1 ● Séverine Lechevallier 2 ● Marc Vereslt 2 ● Beata Borak 3 ● Lucas A. Rocha 1 Received: 22 September 2019 / Accepted: 23 December 2019 © Springer Science+Business Media, LLC, part of Springer Nature 2020 Abstract The development of new imaging agents able to differentiate tissue, organs, or pathologies more efficiently and presenting good biocompatibility motivates new studies due to its huge importance in the medical field. On the another hand, near- infrared (NIR) fluorescent probes offer advantages such as very high sensitivity, high photon penetration, low-light scattering, and minimal autofluorescence from living tissues, whereas magnetic resonance imaging (MRI) offers better resolution. In this context, this work aimed to obtain particles based on niobium oxide doped with Gd 3+ (1, 6, and 10%) and Tm 3+ (3%) by the nonhydrolytic sol–gel to be applied as contrast agents as well as nanoprobes for biolabelling. The structure, luminescent properties, and T1/T2 relaxivity behavior were investigated using scanning electron microscopy, X-ray diffraction, fluorimeter, FTIR and Raman spectroscopies, dynamic light scattering, and MRI techniques. Graphical Abstract The T1 images, no contrast properties can be evidenced which is not surprising for Gd nanoparticles bigger than 10 nm. The T2 image, it can be seen that the signal decreases (increase of T2 contrast properties) as the NPs concentration increases. * Eduardo J. Nassar eduardo.nassar@unifran.edu.br 1 Universidade de Franca, Franca, SP, Brazil 2 CEMES-CNRS, Centre for Elaboration of Materials and Structural Studies, Toulouse, France 3 Department of Mechanics, Materials Science and Engineering, Wroclaw University of Science and Technology, Smoluchowskiego 25 Str., 50-370 Wroclaw, Poland 1234567890();,: 1234567890();,: