Squaraine dye molecules and their derivatives are gaining significant interest in the field of supramolecular chemistry, both in host–guest recognition and self-assembly. The unique structure and properties of squaraine molecules has led to extensive research into their use as sensors. This feature article covers the most recent studies (2004–2009) in the development, characterization, and application of squaraine dye-based molecular sensors, self-assembly, and their use in polymeric materials and biological applications.

A simple pyrene-based triazole receptor has been synthesised and shown to self-assemble in the presence of ZnCl₂ in an exclusively 2 : 1 ratio, whereas a mixture of 2 : 1 and 1 : 1 ratios are observed for other Zn²⁺ salts. The pyrene units are syn in orientation; this is supported by a strong excimer signal observed at 410 nm in the presence of ZnCl₂ in acetonitrile. DFT calculations and 2D NMR support the proposed structure.

A glow assay technology for the detection of a chemical warfare simulant is presented, which is based on modulating the peroxyoxalate chemiluminescence pathway by way of utilising an oximate super nucleophile that gives an “off–on” glow response.

The measurement of trace analytes in aqueous systems has become increasingly important for understanding ocean primary productivity. In oceanography, iron (Fe) is a key element in regulating ocean productivity, microplankton assemblages and has been identified as a causative element in the development of some harmful algal blooms.The chemosenor developed in this study is based on an indicator displacement approach that utilizes time-resolved fluorescence and fluorescence resonance energy transfer as the sensing mechanism to achieve detection of Fe³⁺ ions as low as 5 nM. This novel approach holds promise for the development of photoactive chemosensors for ocean deployment.

Two coumarin-enamine chemodosimeters have been synthesized in three steps. They have been shown to selectively detect the cyanide ion with a fluorescent response (t_1/2 = 20 s) and a limit of detection approximately 4.2 ppb in DMSO. The X-ray crystal structure of the thermodynamically stable E-(keto) enamine isomer of one compound was obtained and exhibited offset π-stacking.