Multifunctional Lanthanide-Doped Core/Shell Nanoparticles: Integration of Upconversion Luminescence, Temperature Sensing, and Photothermal Conversion Properties

Multifunctional integration on single upconversion nanoparticles (UCNPs), such as the simultaneous achievement of imaging, sensing, and therapy, will be extremely attractive in various application fields. Herein, we demonstrated that single core/shell NaGdF4:Yb/Er-based UCNPs (<10 nm) with a highly Yb3+ or Nd3+ doped shell simultaneously exhibited good upconversion luminescence (UCL), temperature sensing, and photothermal conversion properties under 980 or 808 nm excitation, respectively. The spatial separation between the emission/sensing core and the heating shell was able to tailor the competition between the light and heat generation processes, and hence higher UCL efficiency and enhanced heating capability were achieved by introducing the rational core/shell design. Especially, Nd3+-sensitized core/shell nanoparticles were excitable to the laser at a more biocompatible wavelength of 808 nm, and hence the heating effect of water was greatly minimized. The heating and sensing capabilities of Nd3+-sensitized core/shell UCNPs with smaller sizes (<10 nm) were confirmed in aqueous environment under single 808 nm laser excitation, implying their promising applications in imaging-guided and temperature-monitored photothermal treatments.