Two-photon fluorescent probes with large two-photon absorption (TPA) cross sections have shown wide applications in biomedical domain. However, both the species and amounts of high efficient probes are far from meeting the requirements, one main reason is that the relationship between the molecular structures and the responsive mechanisms are not clear and theoretical framework in this field is not perfect. In this work, the photophysical properties including one- and two-photon absorption and emission of three newly synthesized fluorescent probes for hydrogen polysulfide (H₂S_n) detection are investigated by density functional theory and time-dependent density functional theory with the polarizable continuum model in different solvents. Results indicate that the enhanced fluorescent intensity and enlarged TPA cross section can be found when the probes reacted with H₂S_n. Moreover, the OPA intensity is largest and its fluorescent intensity is largely enhanced when detecting H₂S_n for Pro2, this verifies its superior performance in the detection of H₂S_n than Pro1 and Pro 3. Furthermore, the inner mechanism for the increase of TPA cross section is revealed, the responsive mechanisms for photo induced electron transfer (PET) and fluorescence resonance energy transfer (FRET) processes are revealed through analyzing the energies and distributions of frontier orbitals. Our calculations provide theoretical perspectives for experimental measurements and could sever as a useful reference for developing advanced probes in biomedical fields.

具有大的两光子吸收（TPA）横截面的两光子荧光探针已在生物医学领域显示出广泛的应用。但是，高效探针的种类和数量均不能满足要求，主要原因之一是分子结构与响应机制之间的关系不明确，该领域的理论框架还不完善。在这项工作中，光物理特性包括三个新合成的多硫化氢（H ₂ S _n通过密度泛函理论和随时间变化的密度泛函理论，研究了在不同溶剂中可极化连续体模型的检测。结果表明，当探针与H ₂ S _n反应时，荧光强度增强，TPA截面增大。此外，在检测Pro _2的H ₂ S _n时，OPA强度最大，荧光强度大大增强，这证明了其在H ₂ S _n检测中的优越性能。通过分析Pro的能量和分布，揭示了TPA截面增加的内在机理，揭示了光诱导电子转移（PET）和荧光共振能量转移（FRET）过程的响应机制。边界轨道。我们的计算为实验测量提供了理论观点，并可能为开发生物医学领域的先进探针提供有用的参考。