Lanthanide doped upconversion nanoparticles (UCNPs) that convert near infrared photons to visible/ultraviolet emissions have been widely used in sensing applications due to high chemical/photostability without bleaching and blinking, large anti-Stokes shift with low autofluorescence background, sharp and tunable emission bands, etc. Normally, these prominent achievements are accomplished by using UCNP ensembles with statistical average luminescence. However, the nanoparticle ensembles neglect the discrepancy between nanoparticles, especially for the interactions between nanoparticles and in situ status. Benefiting from uniform UCNP construction and single particle spectroscopy, the investigations of upconverting sensing have been expanded to single nanoparticle level. These facilitated the revelation of photophysics and photochemistry variations in micro/nano regions, leading to efficient and sensitive in situ detection, tracking, and sensing. Herein, we present a systematic review on the recent advances in single upconverting nanoparticle sensing, including the strategies to obtain uniform and sensitive upconversion nanoprobes, optical detection systems and emerging single UCNP applications in ions, molecules and in situ microenvironment sensing. Then, current challenges and future potentials of single UCNP sensing with high sensitivity and spatial resolution are discussed. This review is expected to inspire more thorough investigations of high throughput single upconverting nanoparticle sensing with high spatial and temporal resolution.

中文翻译：

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单上转换纳米粒子传感的进展


稀土掺杂上转换纳米颗粒 (UCNP) 可将近红外光子转换为可见光/紫外线发射，由于具有高化学/光稳定性（无需漂白和闪烁）、大反斯托克斯位移和低自发荧光背景、锐利且可调谐的发射带，已广泛用于传感应用通常，这些突出的成就是通过使用具有统计平均发光的 UCNP 系综来完成的。然而，纳米粒子系综忽略了纳米粒子之间的差异，特别是纳米粒子与原位状态之间的相互作用。受益于统一的UCNP结构和单粒子光谱学，上转换传感的研究已经扩展到单纳米粒子水平。这些有助于揭示微/纳米区域的光物理和光化学变化，从而实现高效、灵敏的原位检测、跟踪和传感。在此，我们对单上转换纳米粒子传感的最新进展进行了系统综述，包括获得均匀且灵敏的上转换纳米探针的策略、光学检测系统以及在离子、分子和原位微环境传感中新兴的单UCNP应用。然后，讨论了具有高灵敏度和空间分辨率的单一 UCNP 传感的当前挑战和未来潜力。这篇综述预计将激发对具有高空间和时间分辨率的高通量单上转换纳米粒子传感的更彻底的研究。