基于谷胱甘肽配体的ZnSe量子点对pH响应的时间分辨荧光光谱特性

当前，有关量子点pH响应方面的研究主要集中在含Cd（镉）类量子点，且都是研究其稳态荧光光谱对pH值的响应。然而，Cd类量子点对生物体系具有一定的毒性，且稳态荧光光谱法由于受浓度等因素的影响具有一定的不稳定性，因此应用于生物体系中作为pH探针具有明显的缺点。基于以上分析，通过水相合成法，我们制备出了基于谷胱甘肽配体的水溶性ZnSe量子点，该量子点具有毒性小，生物兼容性好等特点，适合被应用于生物体系中。利用所制备的ZnSe量子点，采用时间相关单光子计数技术，结合紫外可见吸收光谱和稳态荧光光谱，对pH值在5~11不同环境下的ZnSe量子点荧光动力学进行了系统性的研究。ZnSe量子点荧光衰减具有两个寿命组分，拟合得到分别为4和24 ns。通过采集不同探测波长下ZnSe量子点荧光衰减曲线，发现其长寿命组分随探测波长的增加而增加，而短寿命组分基本不随探测波长的改变而改变，结合有关报道分析判断，短寿命和长寿命组分分别来源于核内非局域载流子复合和表面态局域载流子复合。实验发现，处于不同pH值的环境下的ZnSe量子点具有不同的荧光寿命，其荧光寿命与pH值的变化呈负相关。通过比较ZnSe量子点两种荧光寿命组分随pH值的变化关系，发现ZnSe量子点的荧光寿命对pH值的响应主要来源于长寿命组分即表面态寿命，且在不同pH值范围内响应的灵敏度不同，在6~8的pH值范围内响应最为显著，表现为长寿命组分随pH值的增加出现一个较大幅度的衰减。实验进一步发现，ZnSe量子点两个寿命组分的比值在不同pH值范围内具有较好的线性相关性，但在不同pH值范围内斜率不同，通过比较，最大值在pH值为6~8的范围内。另外，与金属钠离子相互作用实验及相关报道表明，金属离子对ZnSe量子点荧光寿命的影响较小。以上研究表明，ZnSe量子点在生物体系pH值检测中具有良好的应用前景。

pH Dependent Time-Resolved Fluorescence Spectra of ZnSe Quantum Dots Based on Glutathione Ligands

At present, the research on the pH response of quantum dots mainly focuses on quantum dots containing Cd, and study only the response of steady-state fluorescence spectrum to pH value. However, quantum dots containing Cd have certain toxicity to the biological system, and the steady-state fluorescence spectrometry has certain instability due to the influence of concentration and other factors, so the application of quantum dots containing Cd as pH probes in biological systems has obvious disadvantages. Based on the above analysis，water-soluble ZnSe quantum dots based on glutathione ligand were made by the water phase synthesis method, showing the characteristics of low toxicity and good biological compatibility，which is suitable for application in biological systems. The fluorescence dynamics of ZnSe quantum dots under different pH values from 5 to 11 have been systematically studied by using time-correlated single-photon counting technique, UV-VIS absorption and steady-state fluorescence spectroscopy. Two fluorescence decay lifetime components of ZnSe quantum dots were found around 4 and 24 ns. By collecting fluorescence decay curves of ZnSe quantum dots at different detection wavelengths, it was found that the long-lifetime components increased with the increment of detection wavelength, while the short-life components did not change with the change of detection wavelength. It is concluded that the short life and long-life components were derived from non-local carrier recombination in the nucleus and local carrier recombination in the surface state, respectively. In addition, it was found that ZnSe quantum dots under different pH values showed different fluorescence lifetimes, and the fluorescence lifetime was negatively correlated with pH change, which was mainly derived from the surface state lifetime components. The sensitivity responding to the pH values was different, which maximized in the pH value range of 6~8, showing a large decay with the increase of pH value for the surface state lifetime components. It was further found that the ratio of two-lifetime components of ZnSe had a good linear correlation with all the pH values, but the slope was different in different pH ranges. The maximum value was within the range of 6~8. The interaction experiments with metal sodium ions and related reports show that metal ions have little influence on the fluorescence lifetime of ZnSe quantum dots. The above studies show that ZnSe quantum dots have a good application prospect in the pH detection of biological systems.