Multifunctional nanoprobe based on upconversion nanoparticles for luminescent sensing and magnetic resonance imaging

Copper ions (Cu2+) play a key role in ecosystems and human health, however, the copper pollution caused by the excessive use of copper has become one of the main problems of modem world. In this paper, a facile method was developed to construct a multifunctional nanoprobe for Cu2+ detection by combining the mesoporous silica coated upconversion nanoparticles (UCNPs) with rhodamine B derivative. beta-NaYF4:Yb,Er@NaGdF4, which could achieve upconversion luminescence (UCL)/magnetic resonance imaging (MRI) dual-mode imaging, was prepared first and then coated with mesoporous silica to form the hydrophilic nanospheres. Subsequently, a rhodamine B derivative DFPP-RhB (denoted as P) was grafted to the mesoporous silica to construct the final multifunctional nanoprobe (denoted as UCNPs@mSiO(2)-P). In this nanoprobe, the mesoporous silica coated NaYF4:Yb,Er@NaGdF4 served as the energy donor, while the rhodamine B derivative P was used as the energy acceptor, resulting in an efficient luminescence resonance energy transfer (LRET) system. The UCNPs@mSiO(2)-P nanoprobe shows high selectivity and sensitivity in detecting of Cu2+. In addition, the Trweighted MRI measured in aqueous solutions reveals that the positive enhancement signals were obtained with increasing of Gd3+ concentrations. This method demonstrates a simple but fascinating strategy to combine the metal ion sensing and multimodal imaging.