以EuCl3和NdCl3混合水溶液为研究对象, 按正交浓度序列以浓度为外部扰动构建紫外可见-荧光二维相关光谱。 在混合溶液的二维相关光谱中, 观察到了Eu3+的荧光发射谱峰与Nd3+的吸收谱峰之间存在交叉峰。 交叉峰的出现表明Eu3+和Nd3+的荧光发射与吸收之间存在能量传递。 二维相关光谱中交叉峰的产生并非由于溶剂水分子与溶质(Eu3+或Nd3+)之间相互作用; 若以单一溶质的EuCl3和NdCl3的水溶液构造模拟的“混合溶液”的拟合光谱构建二维紫外可见-荧光相关光谱, 由于Eu3+和Nd3+在空间上相互分离, 无相互作用发生, 交叉峰并不存在。 二维相关光谱的交叉峰可为从光谱学角度探测复杂体系能量传递及其相关机制提供一条新思路。

In the present paper, the authors developed a new approach by constructing two-dimensional (2D) UV-Vis/fluorescence heterogeneous synchronous spectrum based on the orthogonal sample design scheme (OSD) developed in our previous works to characterize energy transfer among different lanthanide ions during the luminescence process. The authors use the EuCl3-NdCl3 system as an example. The preliminary experimental results on the 2D synchronous spectra of EuCl3-NdCl3 mixture solutions have demonstrated that cross peaks can be observed among the UV-Vis absorption bands from Nd3+ and fluorescence emission bands from Eu3+. The cross peaks in the 2D synchronous spectra of EuCl3-NdCl3 mixture solutions manifested the interaction between the fluorescence emission from Eu3+ and UV-Vis absorbance from Nd3+, and therefore gives out experimental evidences for the occurrence of energy transfer between Eu3+ and Nd3+ ions. The cross peaks are not from the interaction between the solvent, water, and the solute, Eu3+ or Nd3+ ions. Mathematical analysis performed on 2D synchronous spectra using variable concentration as an external perturbation shows that the orthogonal sample design scheme is indispensable in removing the interfering cross peaks in 2D synchronous spectra. In fact, if the authors detect, respectively, the fluorescence emission spectra of pure Eu3+ solutions and the UV-Vis absorbance spectra of pure Nd3+ solutions, then use these spectra data to construct a series of synthesized spectra of an assumed mixture solution in which Eu3+ and Nd3+ are not mixed together, because Eu3+ and Nd3+ ions are spatially separated, there are no intermolecular interactions that should have occurred. Therefore, there are no cross-peaks that can be observed in the comparative 2D synchronous spectra. The cross peaks in 2D synchronous correlation spectra gives out a new approach to characterizing energy transfer among different lanthanide ions during the luminescence process.