Qiyue Shao

Enhancing the upconversion luminescence and photothermal conversion properties of ∼800 nm excitable core/shell nanoparticles by dye molecule sensitization

Upconversion nanoparticles capable of strongly absorbing photons in a wide spectral range are highly desired for practical applications. In this work, IR-806 dye was used to increase the light absorptivity of Nd3+/Yb3+/Er3+ tri-doped core/shell nanoparticles and then to enhance their upconversion luminescence under ∼800nm excitation. The IR-806 dye exhibited more efficient energy transfer to Nd3+ ions than to Yb3+ ions for subsequent upconversion emission due to the increased spectral overlap between the dye emission and Nd3+ absorption. The influence of the Nd3+ concentration in the shell and the dye/nanoparticle ratio on the dye-sensitization effect was also investigated. A maximum 28-fold overall enhancement in the emission intensity was achieved for NaYF4:Yb3+/Er3+@NaYF4:Yb3+/Nd3+ core/shell nanoparticles using dye sensitization. The dye-sensitized NaYF4:Yb3+/Er3+@NaYF4:Yb3+/Nd3+ core/shell nanoparticles also exhibited increased photothermal conversion capabilities and excellent temperature sensing properties, enabling their potential application in photothermal nanoheaters with real-time temperature monitoring under 808nm single beam excitation.

Phase-, shape- and size-controlled synthesis of NaYF4:Yb3+,Er3+ nanoparticles using rare-earth acetate precursors

Abstract Hexagonal-phase NaYF4:Yb3+,Er3+ upconversion nanoparticles (UCNPs) with a uniform size distribution were synthesized using rare-earth acetates as precursors. The effects of reaction temperature and time on the phase transition process of the UCNPs were systematically studied. Based on the evolution of particle morphology and phase with temperature and time, it could be concluded that the transition from cubic phase to hexagonal phase for NaYF4:Yb3+,Er3+ UCNPs was consistent with a dissolution/recrystallization process. In addition, the shape and size of the UCNPs could be controlled by adjusting the solvent ratio and the precursor ratio, respectively.

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.