Trivalent europium ions (Eu³⁺) activated inorganic materials, known as one of the most important red-emitting phosphors, are emerging as an attractive class of luminescent materials over the past decades. Specifically, Eu³⁺ ion is considered as an ideal spectroscopic probe to decipher the local environment in view of its non-degenerate ground state of ⁷F₀ and excitation state of ⁵D₀. Benefiting from the intense long-lived luminescence from ⁵D₀, Eu³⁺-activated inorganic nanoparticles are also frequently reported as luminescent probes in biological assays and medical imaging. With the development of advanced synthesis strategies and characterization techniques, more new understanding or progress in Eu³⁺-activated luminescent nanoprobes have been gained with regard to their fundamental photophysics/photochemistry properties and versatile bioapplications. As such, it is urgent to renew the knowledge in this field. Rather than being exhaustive, this review aims to highlight the latest progress in the electronic structures, optical properties and emerging bioapplications of Eu³⁺-activated nanoprobes, which covers from spectroscopic site symmetry, excited-state dynamics, downshifting/upconversion luminescence enhancement strategies, and luminescent biosensing, with an emphasis on their heterogeneous/homogeneous biodetection as well as in vitro and in vivo bioimaging. Some future prospects and efforts toward this rapidly developing field are also discussed.

在过去的几十年中，三价离子（Eu ³⁺）活化的无机材料被公认为是最重要的发红光的磷光体之一，已成为一类有吸引力的发光材料。具体地，鉴于Eu ³⁺离子的未简并基态⁷ F ₀和激发态⁵ D ₀，它被认为是解密局部环境的理想光谱探针。受益于⁵ D ₀，Eu ³⁺的强烈长寿命发光活化的无机纳米粒子在生物测定和医学成像中也经常报道为发光探针。随着先进合成策略和表征技术的发展，关于Eu ³⁺活化的发光纳米探针的基本光物理/光化学性质和通用的生物应用，人们获得了更多的新理解或新进展。因此，迫切需要更新该领域的知识。这篇综述并非详尽无遗，而是着重强调了Eu ³⁺在电子结构，光学性质和新兴生物应用方面的最新进展。激活的纳米探针，涵盖了光谱学上的位点对称性，激发态动力学，降频/上转换发光增强策略和发光生物传感，重点是它们的异质/均质生物检测以及体外和体内生物成像。还讨论了在这个快速发展的领域中的一些未来前景和努力。