A simple and low cost chemosensor is described. This sensor could simultaneously detect three biologically important metal ions through fluorogenic (Zn²⁺) and chromogenic (Fe²⁺, Cu²⁺, and Zn²⁺) methods in aqueous solution. The sensor could function as a “turn-on” fluorescence receptor only to Zn²⁺ ions. In addition, the sensor could be successfully applied to the detection of intracellular Zn²⁺. Meanwhile, the sensor displayed an obvious red color upon selective binding with Fe²⁺. Therefore, the sensor could serve as a useful tool for the discrimination of Fe²⁺ from Fe³⁺ in aqueous media. Moreover, the sensor also showed color changes from yellow to colorless upon selective binding with Zn²⁺ and Cu²⁺, respectively. The detection limit of the sensor for Cu²⁺ (1.5 μM) is far below the guidelines of the World Health Organization (30 μM) as the maximum allowable copper concentration in drinking water, and therefore it is capable of being a practical system for the monitoring of Cu²⁺ concentrations in aqueous samples. These results provide a new approach for selectively recognizing the most important three trace elements in the human body simultaneously, for Zn²⁺ by emission spectra and Fe²⁺, Cu²⁺, and Zn²⁺ by the naked eye.

A new multifunctional Schiff-base receptor 1 which exhibits an excellent cell-permeable fluorescence for Al ³⁺ and a color change for CN ⁻ in aqueous media has been prepared.

A colorimetric chemosensor was synthesized for sequential detection of Cu²⁺and CN⁻, and used to detect and quantify Cu²⁺.

A new metal ion sensor that contains quinoline and pyridylaminophenol has been synthesized. In acetonitrile and in the presence of Zn²⁺, the sensor fluoresces. In contrast, in aqueous solutions the sensor fluoresces in the presence of Cd²⁺. The fluorescence of the molecule is selective for Zn²⁺ or Cd²⁺ and shows no fluorescence with other metal ions. The crystal structure of the Cd²⁺ complex shows coordination through the amide and phenol oxygens, as well as the amine nitrogen of the sensor. The sensor also acts as a colorimetric sensor for Co²⁺ by changing color from colorless to yellow. The color change is selective for Co²⁺ and is not observed with other metal ions. The unique combination of pyridine and phenol groups with quinoline results in the properties of this sensor.

A highly selective and sensitive colorimetric Cu²⁺-chemosensor and pH probe for practical use in water has been developed.