Heavy metal and transition metal ions are widely present in the natural world and have significant implications for human health. Certain transition metal ions, such as Cu2+, Zn2+, and Fe3+, serve as essential trace elements in the organism, playing crucial roles in protein synthesis and metabolic processes [[1], [2], [3]]. Conversely, highly toxic and carcinogenic heavy metal ions can accumulate in both ecosystems and living organisms, leading to significant harm to the environment and posing serious risks to human health [4,5].

Copper ions are essential trace elements for living organisms [6,7]. Adequate levels of Cu2+ can promote the growth of both animals and plants. Under normal conditions, the concentration of copper ions in human blood should be maintained between 100 and 150 μg/dL [8]. However, excessive copper ions in the liver and kidneys can lead to serious health conditions, including Wilson's disease, amyotrophic lateral sclerosis, and Menke's syndrome, among others [[9], [10], [11], [12], [13], [14], [15]]. Therefore, developing effective technologies for detecting copper ions is crucial. Fluorescent probes are particularly favored for their high selectivity, excellent sensitivity, and ease of use [[16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29]]. However, most fluorescent probes for detecting copper ions have the drawback of short emission wavelengths, which are prone to crosstalk with the fluorescence of the actual samples themselves during the recognition of copper ions [30,31].

Coumarin derivatives have demonstrated significant potential in the detection of anions, metal ions, and other species [2,32]. As a natural compound with broad biological activity, coumarin, due to its excellent fluorescence properties, has found extensive use in the development of chemosensors. Through chemical modifications, coumarin derivatives can achieve highly selective responses to specific target molecules, such as metal ions, anions, and other biomolecules, thus playing an important role in fields like environmental monitoring, clinical biomedical diagnostics, and drug development. The development of these derivatives has not only enhanced the sensitivity and specificity of molecular sensing but also broadened their application prospects across various fields [[33], [34], [35], [36], [37], [38], [39]].

In this study, a coumarin chalcone derivative featuring a hydroxyl substituent was specifically developed for selectively recognizing copper ions in aqueous solutions (Scheme 1). This design mainly utilizes the strong fluorescence of the coumarin moiety and the potential coordination sites provided by the carbonyl and hydroxyl groups. The probe is capable of detecting copper ions with long-wavelength fluorescence. The long-wavelength fluorescence offers deeper tissue penetration, reduced photodamage, and can effectively minimizes fluorescence interference from the tested samples, thus being conducive to the detection in biological cells and actual samples [40,41]. The probe demonstrates the effectiveness in the real-time quantitative determination of Cu2+ content in a range of real samples, including water, beverages, and plant samples. Additionally, it is capable of monitoring dynamic fluctuations in intracellular Cu2+ levels, offering valuable insights into cellular copper ion regulation. Compared to previously reported work of our group [42], the introduction of diethylamino groups in the probe enhances the fluorescent properties and solubility of the probe molecule, simultaneously improving recognition sensitivity. Compared to most of the probes reported in references, the probe has longer fluorescence wavelength, fast response rate and more application tests (Table S1).