Abstract
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.
Highlights
In the past few decades, tomographic imaging techniques have played an important role in the investigation of novel biomedical imaging methods
Optical probes that emit in the visible range (400-750nm) can only penetrate approximately 1 mm into the tissue because of the absorption and scattering of the photons [3,4]; for those emitting in the “biological transparency window”, that is the first nearinfrared (NIR-I) window (750-900 nm), the penetration depth only reaches several millimeters [5,6]
For the medical applications of this material, we exploited 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, and the function of physiological temperature sensing with the luminescence of Er3+ in the visible region
Summary
In the past few decades, tomographic imaging techniques have played an important role in the investigation of novel biomedical imaging methods. Near-infrared contrast agents have generated particular interest in recent years due to their emission at longer wavelengths where scattering is reduced, and auto-fluorescence is weak [7–9] These advantageous features enable imaging with increased signal-to-background ratio to greater depths within tissue and realize high spatial resolution imaging. Compared with the previously reported handful of NIR II organic dyes and QDs, lanthanide-doped nanoparticles possess outstanding chemical and optical properties, including low cytotoxicity, high efficiency, low photo-bleaching, long luminescence and photochemical degradation [15, 16] They can emit UV and visible light after excitation by near-IR (NIR) light, through a process known as photon upconversion [17]. The strategy to design dual mode sensing and imaging composites may be extended to prepare multi-functional platforms for targeted multi-mode imaging of various biological systems
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