A Review on Quinoline-Based Derivatives as Selective Colorimetric and Fluorescent Chemosensors for Cu

Quinoline-based scaffolds have emerged as versatile platforms for designing selective colorimetric and fluorescent chemosensors due to their excellent π-conjugation, nitrogen donor sites, and tunable photophysical properties. Recent studies have demonstrated that quinoline derivatives, including Schiff bases, sugar conjugates, supramolecular assemblies, and hybrid frameworks, provide highly sensitive and selective detection of Cu2+ and Fe3+ ions through mechanisms such as intramolecular charge transfer (ICT), photoinduced electron transfer (PET), and chelation-enhanced quenching (CHEQ). These sensors display diverse outputs, including fluorescence “turn-off/turn-on,” ratiometric emission, and naked-eye colorimetric changes, with detection limits often well below WHO/EPA standards for safe water. Importantly, many probes have shown real-world applicability in biological imaging, industrial wastewater monitoring, and portable sensing devices. This review highlights the structural diversity, sensing mechanisms, and practical utility of quinoline-derived chemosensors, underscoring their significance in environmental and biomedical applications.