Department of Chemistry, Fudan University, 2005 Songhu Road, Shanghai 200433, People's Republic of China.
Human Phenome Institute, Fudan University, 825 Zhangheng Road, Shanghai 201203, People's Republic of China.
ACS Appl Mater Interfaces. 2022 Mar 30;14(12):14004-14011. doi: 10.1021/acsami.1c21838. Epub 2022 Mar 17.
Lanthanide-ion-doped upconversion materials have been widely used in biological detection, bioimaging, displays, and anticounterfeiting due to their abilities of real-time readings, high spatial resolution, and deep tissue penetration. The typically long fluorescence lifetimes of rare-earth nanoparticles, in the microsecond to millisecond range, make them useful in interference-free lifetime detection imaging. Most detection systems are accompanied by fluorescence resonance energy transfer (FRET), in which the lifetime of the luminescence center can be used as a signal to reveal the degree of FRET. Due to the complex energy level structure and complex energy transfer processes, the apparent lifetimes of upconversion nanoparticles (UCNPs) do not simply equal the decay time of the corresponding energy level, inducing an insignificant lifetime change in the upconversion detection system. In this study, the relationship between the apparent luminescence lifetime of upconversion and the decay rate of each energy level was studied by numerical simulations. It was proved that the apparent lifetime of the emission at 540 nm was mainly affected by the decay rate of Yb. We then constructed a nanocomposite with Rh1000 fluorophores loaded onto the surface of UCNPs to quench the sensitizer Yb. We found that the lifetime of the emission at 540 nm from Er was affected to a large extent by the number of attached Rh1000 molecules, proving the greater influence on the apparent luminescent lifetime of Er at 540 nm caused by quenching the Yb excited state. The qualitative detection of hypochlorous acid (HClO) was also achieved using the luminescent lifetime as the signal.
镧系离子掺杂的上转换材料由于其实时读数、高空间分辨率和深组织穿透能力，广泛应用于生物检测、生物成像、显示和防伪领域。稀土纳米粒子的典型荧光寿命较长，在微秒到毫秒范围内，这使得它们在无干扰寿命检测成像中非常有用。大多数检测系统都伴随着荧光共振能量转移（FRET），其中发光中心的寿命可作为信号来揭示 FRET 的程度。由于能级结构复杂和能量转移过程复杂，上转换纳米粒子（UCNP）的表观寿命并不简单地等于相应能级的衰减时间，这在上转换检测系统中导致了不明显的寿命变化。在本研究中，通过数值模拟研究了上转换的表观发光寿命与各能级衰减速率之间的关系。证明了 540nm 发射的表观寿命主要受 Yb 衰减速率的影响。然后，我们构建了一种纳米复合材料，将 Rh1000 荧光团负载到 UCNP 表面上，以猝灭敏化剂 Yb。我们发现，Er 在 540nm 的发射寿命在很大程度上受到附着的 Rh1000 分子数量的影响，这证明了猝灭 Yb 激发态对 Er 在 540nm 处的表观发光寿命的更大影响。通过将荧光寿命作为信号，还实现了对次氯酸（HClO）的定性检测。
