Fluorescent Chemosensors Based on Polyamine Ligands: A Review

Polyamine ligands are water-soluble receptors that are able to coordinate, depending on their protonation degree, either metal ions, anionic, or neutral species. Furthermore, the presence of fluorescent signaling units allows an immediate visual response/signal. For these reasons, they can find applications in a wide variety of fields, mainly those where aqueous media is necessary, such as biological studies, wastewater analysis, soil contamination, etc. This review provides an overview of the recent developments in the research of chemosensors based on polyamine ligands functionalized with fluorescent signaling units. The discussion focuses on the design, synthesis, and physicochemical properties of this type of fluorescent chemosensors in order to analyze the applications associated to the sensing of metal ions, anions, and neutral molecules of environmental and/or biological interest. To facilitate a quick access and overview of all the chemosensors covered in this review, a summary table of the chemosensor structures and analytes, with all the corresponding references, is also presented.

Review on Calixarene Fluorescent Chemosensor Agents for Various Analytes

Calixarenes are well-known supramolecular host molecules with versatile applications. Over the past decades, hundreds of selective and sensitive detections of several analytes have been reported by employing calixarenes as the chemosensor agent. The detection and quantification of metal ions and anions are crucial as heavy metal ions are harmful to living organisms, while monitoring anions is pivotal in the environmental samples. On the other hand, detecting and quantifying biomolecules and neutral molecules are critical due to their irreplaceable role in human health. In this review, we summarized the application of calixarenes as the supramolecular chemosensor agent for detecting metal ions, anions, biomolecules, and neutral molecules through fluorescent spectroscopy to give brief information on the design and development of the chemosensor field. This review updates the world with the application of calixarene derivatives as fluorescent chemosensors and challenges researchers to design and develop better chemosensor agents in the future.

A chemosensor-based chiral coassembly with switchable circularly polarized luminescence

Fluorescent chemosensors represent fast response to analytes with pronounced luminescent variations. They are promising as potential candidates in controlling luminescence and chiroptical activities of self-assembled chiral systems, which however have not been accomplished to date. We present a coassembled multiple component system that could respond to SO2 derivatives, giving rise to dynamic aggregation behaviors and switchable luminescence as well as circularly polarized luminescence (CPL). Cholesteryl-naphthalimide and coumarin derivatives coassemble into vesicles and nanohelices under the solvent strategy, behaving as energy transfer donor and accepter respectively. Energy transfer enables CPL transition from green to red depending on the molar fraction. After the addition of SO2 derivatives, hypochromic shifts occur to CPL due to the nucleophilic addition reaction to coumarin domain, hindering energy transfer and allow for the emergence of pristine luminescence. Here, we show a protocol to control over luminescence and chiroptical features of supramolecular chiral self-assemblies using fluorescent chemosensors.

Fluorescent Chemosensors for Ion and Molecule Recognition: The Next Chapter

Over the past 30 years fluorescent chemosensors have evolved to incorporate many optical-based modalities and strategies. In this perspective we seek to highlight the current state of the art as well as provide our viewpoint on the most significant future challenges remaining in the area. To underscore current trends in the field and to facilitate understanding of the area, we provide the reader with appropriate contemporary examples. We then conclude with our thoughts on the most probable directions that chemosensor development will take in the not-too-distant future.