Fluorescein molecules are extensively used to develop fluorescent probes for various analytes due to their excellent photophysical properties and the spirocyclic structure. The main structural modification of fluorescein occurs at the carboxyl group where different groups can be easily introduced to produce the spirolactam structure which is non-fluorescent. The spirolactam ring opening accounts for the fluorescence and the dual sensing of analytes using fluorescent sensors is still a topic of high interest. There is an increase in the number of dual sensors developed in the past five years and quite a good number of fluorescein derivatives were also reported based on reversible mechanisms. This review analyses environmentally and biologically important cations such as Cu²⁺, Hg²⁺, Fe³⁺, Pd²⁺, Zn²⁺, Cd²⁺, and Mg²⁺; anions (F⁻, OCl⁻) and small molecules (thiols, CO and H₂S). Structural modifications, binding mechanisms, different strategies and a comparative study for selected cations, anions and molecules are outlined in the article.

荧光素分子因其优异的光物理性质和螺环结构而被广泛用于开发各种分析物的荧光探针。荧光素的主要结构修饰发生在羧基上，可以很容易地引入不同的基团以产生不发荧光的螺内酰胺结构。螺内酰胺开环解释了荧光，使用荧光传感器对分析物进行双重传感仍然是一个备受关注的话题。在过去五年中开发的双传感器数量有所增加，并且还报道了相当多的基于可逆机制的荧光素衍生物。这篇综述分析了环境和生物学上重要的阳离子，例如 Cu ²⁺、Hg ²⁺、Fe³⁺、Pd ²⁺、Zn ²⁺、Cd ²⁺和Mg ²⁺；阴离子（F ^-、OCl ^-）和小分子（硫醇、CO 和 H ₂ S）。本文概述了结构修饰、结合机制、不同策略以及对选定的阳离子、阴离子和分子的比较研究。