Architecture of Easy-to-Synthesize and Superior Probe Based on Aminoquinoline Appended Naphthoquinone: Instant and On-Site Cu²⁺ Ion Quantification in Real Samples and Unusual Crystal Structure and Logic Gate Operations

Easy-to-synthesize aminoquinoline (AQ) appended naphthoquinone (NQ)-based colorimetric and ratiometric probe (AQNQ) was successfully synthesized in one step with high yield and low cost, and was utilized to supply an effective solution to critical shortcomings encountered in Cu²⁺ analysis. The structure of AQNQ and its interaction with Cu²⁺ forming an unusual AQNQ-Cu complex were enlightened with single-crystal X-ray diffraction analysis and different spectroscopic methods. AQNQ-Cu complex is the first Cu²⁺ containing dinuclear crystal where the octahedral coordination sphere is fulfilled through the coordination of a NQ oxygen atom. AQNQ exhibited long-term stability (more than 1 month), superior probe ability toward Cu²⁺ with quite fast response (30 s), high selectivity among many ions, and limit of detection of 12.13 ppb that is significantly below the highest amount of Cu²⁺ allowed in drinking water established by both WHO and EPA. Ratiometric determination of Cu²⁺ using AQNQ was performed with high recovery and low RSD values for drinking water, tap water, lake water, cherry, and watermelon samples. Colorimetric on-site determination including smartphone and paper strip applications, IMPLICATION, and INHIBIT logic gate applications were successfully carried out. The reversibility and reusability of the response to Cu²⁺ ions with the paper strip application were examined for the first time.