In this study, two photoswitchable spiropryran-capped hybrid nanoparticles based on two different core/shell upconverting nanoparticles (UCNPs) were reported. Two kinds of LiYF₄ core/shell UCNPs doped with Yb³⁺/Ho³⁺ and Yb³⁺/Tm³⁺ were first prepared and could emit the ultraviolet (UV) and visible light under 980 nm NIR excitation respectively. X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis indicated that both kinds of UCNPs had the tetragonal phase and the single-crystal structure. The photoluminescence (PL) intensities were much enhanced through the active-core/active-shell synthetic strategy. Next, the spiropyran molecules could be coordinated onto the surface of the oleate-capped UCNPs via ligand exchange, which was confirmed by fourier transform infrared (FTIR) spectra. PL spectra for the Ho³⁺-doped SP-UCNPs hybrid nanoparticles revealed that the green emission band excited by near-infrared (NIR) light could be completely quenched after illuminating SP-UCNPs with UV for 150 s. The cyclical photoswitching tests were further carried out for both kinds of UCNPs by alternating irradiation with UV/visible, UV/NIR, or NIR/visible light. The optical switching of PL intensity of the spiropryran-capped UCPNs did not have apparent decline effect after 10 cycles of on/off test. A reversible photoswitching of the hybrid nanoparticles revealed that both kinds of spiropyran-capped UCNPs had a superior photostability for the biological applications.

在这项研究中，报道了基于两种不同的核/壳上转换纳米颗粒（UCNP）的两种光可转换螺并吡喃帽封端的杂化纳米颗粒。两种掺有Yb ³⁺ / Ho ³⁺和Yb ³⁺ / Tm ³⁺的LiYF ₄核/壳UCNP首先制备了它们，它们可以分别在980 nm NIR激发下发射紫外线（UV）和可见光。X射线衍射（XRD）和透射电子显微镜（TEM）分析表明，两种UCNP均具有四方相和单晶结构。通过主动核心/主动壳合成策略大大提高了光致发光（PL）强度。接下来，螺吡喃分子可以通过配体交换配位到油酸酯封端的UCNPs表面，这通过傅立叶变换红外（FTIR）光谱得以证实。Ho ^3+的PL光谱掺杂SP-UCNPs杂化纳米颗粒表明，用UV照射SP-UCNPs 150 s后，近红外（NIR）激发的绿色发射带可以完全淬灭。通过用紫外线/可见光，紫外线/近红外或近红外/可见光交替照射，进一步对两种UCNP进行了周期性光开关测试。在开/关测试10个循环后，螺吡喃帽式UCPN的PL强度的光开关没有明显的下降效果。杂化纳米颗粒的可逆光开关显示，两种螺吡喃帽封端的UCNP在生物学应用中均具有优异的光稳定性。