Past and Present Research Systems of Green Chemistry

Biography

Biography: Juan Li

Abstract

Unmodified metallofullerenes (Gd@C82) were carried on Graphene oxide (GO) as a new magnetic resonance imaging (MRI) contrast agent. The higher R1 relaxivity of GO-Gd@C82 nanohybrids and better brightening effect than Gd@C82(OH)X, in T1-weighted MR images in vivo. How does the proton relaxivity from original gadofullerenes, which kept perfect carbon cage structure and so might completely avoid the release of Gd3+ ions? A “secondary spin-electron transfer” relaxation mechanism was proposed. To better understand the relaxation mechanism in the novel carbon nanohybrids, the structure and the physicochemical properties of carbon nanohybrids were compared carefully, which including the appropriate electric conductivity and the size of GO, the increased number of H proton exchange sites and the enough concentration of Gd3+. The results indicated that though the fundamental origin of relaxivity was still the unpaired electrons spin from Gd3+ in the nanohybrids, but the variety of Gd3+ concentration was not adequately to decipher the high relaxation of the novel architecture. The hydrophilic groups (-OH, -COOH) on GO nanosheets and the electric conductivity were considered to influence the relaxivity of GO-Gd@C82 nanohybrids when the concentration of Gd3+ was certain. The electron transfer from Gd@C82 to GO also contributed to the proton relaxation, which should cooperate with the excellent conductivity of GO to transfer spin-electron to the proton exchange sites.