Activatable Rare Earth Near-Infrared-II Fluorescence Ratiometric Nanoprobes

Rational design of efficient lanthanide-doped downshifting nanoparticles (DSNPs) has attracted tremendous attention. However, energy loss was inevitable in the multiple Ln(3+) doping systems owing to complex energy migration processes. Here, an efficient NaErF4@NaYF4@NaYF4:10%Nd@NaYF4 DSNP was tactfully designed, in which a buffer layer of NaYF4 was modulated to restrict the interionic energy migration between Er3+ and Nd3+; meanwhile, the surface defects were passivated by an outermost layer of NaYF4. Therefore, the asprepared DSNPs exhibited two intensive near-infrared-II fluorescence emissions of 1525 nm from Er3+ and 1060 nm from doped Nd3+ under 808 nm excitation. Further, a novel ratiometric nanoprobe NaErF4@ NaYF4@NaYF4:10%Nd@NaYF4@A1094 was fabricated by coupling an organic dye of A1094 onto the DSNP surface to quench the 1060 nm emission by the efficient Forster resonance energy transfer, while emission at 1525 nm retained. Thereafter, these activatable ratiometric nanoprobes were used for rapid and sensitive detection of peroxynitrite (ONOO-) in vivo.

Automated summary

Efficient lanthanide-doped downshifting nanoparticles were successfully designed with minimized energy loss, demonstrating strong near-infrared-II fluorescence emissions. A novel ratiometric nanoprobe was fabricated for rapid and sensitive detection of peroxynitrite in vivo, showing great potential for biomedical applications.