@article{oai:repo.qst.go.jp:00074806,
 author = {K, Morishita and S, Ueki and Y, Fuchi and S, Murayama and T, Kaneko and N, Narita and S, Kobayashi and G, Hirai and Aoki, Ichio and S, Karasawa and Murayama, Shuhei and Aoki, Ichio},
 issue = {12},
 journal = {ACS Appl. Nano Mater.},
 month = {Nov},
 note = {As part of a series of investigations related to the construction of metal-free magnetic resonance imaging (MRI) contrast agents as alternatives to gadolinium agents, water-soluble biradicals, denoted as 1-AMP and 2-HEG, were prepared, in which two stable radicals were introduced to a ureabenzene framework. We found that 1-AMP possessed an amphiphilic side chain that consisted of an alkyl group and a hexaethylene glycol (HEG) chain, whereas 2-HEG possessed only an HEG chain. Accordingly, the biradicals showed self-assembly behavior due to multiple intermolecular interactions through which nanoparticles were formed in a water solution. Magnetic interaction took place in both biradicals, and the estimated interaction strength was J = 5.4 mT. Through MRI measurement, the water proton relaxivities, r1, were estimated to be 0.12 and 0.41 mM–1 s–1 for 1-AMP and 2-HEG, respectively; in other words, the r1 value for 2-HEG was approximately twice as high as that of monoradical-based contrast agents.},
 pages = {6967--6975},
 title = {Self-Assembled Biradical Ureabenzene Nanoparticles for Magnetic Resonance Imaging},
 volume = {1},
 year = {2018}
}