Dual-functional β-NaYF4: Yb3+, Er3+ nanoparticles for bioimaging and temperature sensing

Hexagonal-phase NaYF4: Yb3+, Er3+ nanoparticles (NPs) have been widely used as the most efficient NIR-to-visible upconversion (UC) luminescent and probe in bioscience. Here, we exploited not only the function of dual-mode emission of β-NaYF4: Yb3+, Er3+ NPs in the near infrared (NIR) and visible regions with single wavelength excitation at 980 nm, but also the function of physiological temperature sensing with the luminescence of Er3+ in the visible region. The structural and optical characteristics of β-NaYF4: Yb3+, Er3+ NPs were obtained using X-ray diffraction (XRD), scanning electron microscopy (SEM),and fluorescence spectral measurements, respectively; the mechanism for the energy transfer has been suggested with emphasis on the optimized Er/Yb concentration for most efficient UC. Due to the UC and down-shifting NIR properties, we achieved the dual-functional nanoparticles with potential application in physiological range temperature sensing and bioimaging simultaneously.