In this paper, a rhodamine derivative was synthesized as a probe for Hg(II) detection. Its spectral response and sensing mechanism towards Hg(II) were discussed carefully. It was found that its absorption and emission were increased by Hg(II), via a direct bonding stoichiometry of 1:1. Its association constant was determined with absorption titration as 2.59 × 10⁵ M⁻¹, which suggested a coordination procedure between Hg(II) and this rhodamine probe. It showed good selectivity towards Hg(II) over competing metal cations, no increased emission or absorption was observed in the presence of interfering metal cations. It was then covalently grafted onto silica (SiO₂)-encapsulated upconversion nanoparticles (UCNPs). Upon near-infrared (NIR) excitation (980 nm), RHO accepted energy from these UCNPs through a FRET (fluorescence resonance energy transfer) procedure, quenching their upconversion emission. A sensing response towards Hg(II) was thus constructed. Good linearity and selectivity were still preserved in this composite sample. On the other hand, this work found a different phenomenon from literature cases, which was the emission absence of rhodamine emission in this composite structure. Detailed analysis suggested that rhodamine emission absence was caused by its self-quenching effect.

本文合成了罗丹明衍生物作为Hg（II）检测的探针。仔细讨论了其对汞（II）的光谱响应和传感机理。发现通过Hg（II）通过1：1的直接键合化学计量增加了它的吸收和发射。通过吸收滴定法确定其缔合常数为2.59×10 ⁵ M ^-1，这表明Hg（II）与该罗丹明探针之间的配位程序。与竞争性金属阳离子相比，它显示出对Hg（II）的良好选择性，在存在干扰金属阳离子的情况下，未观察到增加的发射或吸收。然后将其共价接枝到二氧化硅（SiO ₂）封装的上转换纳米粒子（UCNP）。在近红外（NIR）激发（980 nm）下，RHO通过FRET（荧光共振能量转移）程序从这些UCNP接收能量，从而淬灭了它们的上转换发射。因此构建了对Hg（II）的感应响应。在该复合样品中仍保持了良好的线性和选择性。另一方面，这项工作发现了与文献案例不同的现象，即在这种复合结构中没有罗丹明释放。详细分析表明，若丹明释放不出来是由于其自身的猝灭作用引起的。