Squaraine dyes, a four-membered ring system with structural rigidity, possess unique photoelectrical properties and are marked by their exceptionally sharp and intense absorption associated with a strong fluorescent emission in solution. These favorable characteristics have prompted their exploitation in a number of state of the art applications including photoconductivity, data storage, light-emitting field-effect transistors, solar cells and fluorescent histological probes. In this review, we first summarize the recently proposed novel methods in the synthesis of these versatile derivatives. Subsequently, their extensive applications in the prevalent optical detection of the surrounding medium such as ions, pH, thiol-based compounds, biomolecules and cell over the past decades are covered and discussed. In addition, different categories for the synthesis and sensing mechanisms for various squaric acid-based chemo-/bio- sensors are illustrated. Finally, the challenges and opportunities in the synthesis and application of these derivatives are also briefly discussed.

鱿鱼染料是具有结构刚性的四元环系统，具有独特的光电性能，并以与溶液中强烈的荧光发射相关的异常敏锐和强烈的吸收为特征。这些有利的特性促使它们在包括光电导，数据存储，发光场效应晶体管，太阳能电池和荧光组织学探针在内的许多现有应用中得到利用。在这篇综述中，我们首先总结了最近提出的合成这些通用衍生物的新颖方法。随后，讨论了它们在过去数十年中在周围介质（如离子，pH，基于硫醇的化合物，生物分子和细胞）的流行光学检测中的广泛应用。此外，说明了各种基于方酸的化学/生物传感器的合成和传感机制的不同类别。最后，还简要讨论了这些衍生物的合成和应用中的挑战和机遇。